This handy anniversary logo is from the American Water Works Association (AWWA) which, despite its name, is an international scientific and educational association founded to improve water quality and supply of which I have been a member for over 10 years.
The SDWA was the first comprehensive regulatory framework for drinking water in the United States. Prior to SDWA, federal regulation of drinking water began in 1914 when the US Public Health Service regulated interstate water carriers such as ships or railroads. These standards were expanded in 1925, 1946, and 1962. The ’62 standards covering 28 substances, were the most comprehensive pre-SDWA federal drinking water standards and all 50 states had adopted them with varying modifications.
Believe it or not the USPHS is a uniformed service of the US by 37 USC §101. They seem to be a very confused branch because the Surgeon General, in this case Vivek Murthy, is a Vice Admiral.
SDWA Build-up
The ’62 standards did not include many industrial or agricultural chemicals which found their way into drinking water supplies at the time. Concerns around this led to the federal government commissioning water system surveys, a famous one in 1969 (published by none other than AWWA!), showed that only ≈60% of surveyed water systems met the ’62 USPHS standards. Over half of the systems surveyed had major deficiencies involving disinfection, clarification, or pressure. A Region VI study found 36 chemicals in treated drinking water sourced from the Mississippi River in Louisiana. This increasing awareness lead to a constellation of laws which work in concert with SDWA such as the Clean Water Act, CERCLA, RCRA, and many others.
Excerpt from Survey of Community Water Supply Systems by Leland J. McCabe, James M. Symons, Roger D. Lee, Gordon G. Robeck, one of the reports which lead to SDWA.
SDWA Overview
SDWA aims to protect public water supplies, it does not apply to private wells which serve about 13 million people in the US. Under SDWA, a public water supply/system does not refer to who owns it but rather if the system meets certain characteristics such as having more than 15 service connections or serving greater than 25 people so, by SDWA, a public water system can be privately owned. SDWA divides public water systems into categories based on characteristics such as where they serve customers and how often they serve the same people; systems with different characteristics have different rules. The original 1974 SDWA was heavily predicated on the ’62 USPHS standards with added requirements for monitoring, analytical standards, reporting results, record keeping, notification for failing to meet standards, and adding standards.
SDWA has a few seemingly counterintuitive features. Chief among them for the public is the concept of primacy. While SDWA is a federal standard and federal regulators determine the levels of contaminants allowed in drinking water, enforcement authority is delegated to more local bodies that meet specific criteria. Every state except of Wyoming, the inhabited territories, the District of Columbia, and the Navajo Nation all have primacy, or enforcement authority for drinking water.
While there have been several amendments to SDWA, the main amendments occurred in 1986, and 1996. After SDWA’s passage, Congress became frustrated by the slow regulatory pace at the EPA. The 1986 Amendments required EPA to set standards for 83 contaminants and make determinations to regulate an additional 25 contaminants every three years as well as to specify the best available treatment technology for removing each regulated contaminant from drinking water among other provisions. EPA categorically missed statutorily imposed deadlines and there were questions about enforcement efficacy. In the words of EPA’s 1996 water head (known as the Assistant Administrator for the Office of Water), Robert Perciasepe, in testimony to Congress on 31 January said the ’86 amendments created a “regulatory treadmill [which] dilutes limited resources on lower priority contaminants and as a consequence may hinder more rapid progress on high-priority contaminants.” Increased public scrutiny brought about major changes to SDWA in 1996. These amendments focused regulation on through risk-based standard setting, increased funding, created “right-to-know” provisions, and strengthen enforcement authorities among other provisions.
As of third quarter 2024, federal drinking water regulations apply to approximately 143,539 privately and publicly owned water systems and cover ≈87% of the US population. The US is a far cry from circa 40% of surveyed water systems failing basic standards. SDWA has achieved better drinking water quality across the United States. Water-related gastrointestinal disease outbreaks have reduced considerably with SDWA while surveillance and detection have improved. SDWA has been successful in reducing risks and improving public health through dedicated water professionals at the utility, primacy agency, and federal levels. I am proud to play a role in that joint enterprise.
Depending on whom you speak with the term forensics can be a dirty word. It either conjures up images of flawed feature-comparison disciplines (hair-, bite-, or tool-mark comparisons for example) underlined by poor science or single source DNA which exonerates the falsely accused. PFAS forensics, when practiced well, more closely resembles DNA evidence for a criminal case and may play a critical role in ensuring those responsible for contamination pay for its remediation. The purpose of this article is to provide a gentle introduction to environmental forensics with an emphasis on PFAS. This is just one of several articles I have written on PFAS, it may help to refresh on PFAS terminology as well as PFAS analytic strategies. I am acting in my own capacity, my views are my own and do not represent my employer. Nothing here constitutes legal or professional advice.
About 99.9% of DNA between humans is the same however, scientists have characterized DNA regions that are different between people who are not closely related. Forensic labs look at 20 DNA regions that vary between individuals, called short tandem repeats (STRs), to create a DNA “fingerprint.” The chance that two people who aren’t closely related have the same DNA profile is 1 in 1,000,000,000,000,000,000. Paraphrased from Mary May and figure by Rebecca Clements
Introduction to PFAS Forensics
PFAS forensics is not a bunch of EPA investigators playing “good cop bad cop” with a chemical manufacturer or waste manager tied to a chair with a bright spotlight shining in their face. PFAS forensics is the subset of environmental forensics which deals with PFAS. Environmental forensics more generally is really the logical outgrowth and terminus of one branch in fate and contaminant transport. While fate and contaminant transport in general describes how chemicals move and transform throughout the environment, when this is reframed through the lens of forensics the emphasis shifts from more describing mobility and persistence to assist in assessing exposure more to source identification/attribution as well as developing legal along with scientific defensibility of conclusions. With billions on the line in multidistrict litigation you can bet the science will be heavily scrutinized.
Environmental forensics, and by extension PFAS forensics, typically has a few routine questions:
Who is responsible for the PFAS?
When and how was the PFAS released?
In cases with more than one responsible party: How much has each party contributed?
Were the releases progressive or sudden?
Environmental forensics uses several techniques to answer these questions to tease out information about how the contaminant (PFAS in this case) got to the place where it was detected. In many cases multiple releases of the same or related chemical are from the same site which may require contribution allocation for each identified release – this is especially important where more than one responsible party is identified. Beyond obvious applications in litigation, PFAS forensics could potentially lead to cost savings by better characterizing the sites and understanding related risks from them, better tailoring remediation or treatment, and assisting in insurance claims. In some cases, environmental forensics has also lead to completely new discoveries. For example, an unknown natural perchlorate source, unrelated to nitrate from the Atacama Desert or other known sources, was discovered using isotropic fingerprinting during a forensic investigation launched after routine perchlorate monitoring discovered contamination north of San Diego. While a PFAS forensic study may be solved using only one technique it is important to build multiple independent lines of evidence consisting of at least two distinct techniques to check your work. The independent evidence should obviously point to the same conclusion. Cases where one line of evidence is enough tend to include straightforward reported releases or dumping.
Common Non-Intrusive Environmental and PFAS Forensic Techniques
When performing document review, it’s critical to pay attention to chemicals which while may not pose health risks may be linked to the original health contaminant as an additive or may influence the fate and transport of the contaminant of concern. Site features such as underground storage tanks, https://www.epa.gov/ust ditches, loading docks, transformers/electrical components (especially for PCBs) are also important.
Historical document review which can include historical documents (deeds, spill, or ownership records), environmental permits, operational or monitoring data, shipping manifests, as well as sales or invoices can be extremely helpful. These can also assist in recreating production processes if no records exist.
Photographic review is very valuable. Systematic coverage of the US has occurred since the 1930s and changes overtime can be very instructive. The Aerial Photography Field Office of the USDA is particularly valuable and infrared photography can also assist in differentiating vegetation changes.
Interviews with current and past employees, neighbors, or other relevant parties can provide clues to focusing the search or turn up undocumented knowledge.
Market forensics started due to diffuse releases, for example in consumer products. Essentially sales and other relevant product information (eg formulation) is aggregated to estimate total loading. Market forensics has been successfully used on a local scale to determine fatty alcohol (detergent) contamination in Luray, Virginia (home of the caverns). I believe this to be most accurate for PFAS on a global scale as some emissions inventories have shown. In most instances on local scales it is closer to bite mark analysis (forensic odontology) than DNA analysis.
A document review conducted according to the All Appropriate Inquires rule can serve as liability protection and should be the first step in any forensic investigation. Image from Digital WarRoom
Advanced Environmental and PFAS Forensic Techniques
Non-intrusive techniques alone may be enough to end investigations into PFAS sources however, sometimes more advanced techniques are required. These advanced techniques should only be undertaken after integrating any existing knowledge body related to a specific site because advanced techniques are often costly.
Chemical Fingerprinting
Chemical fingerprinting is where specific sources are associated with characteristic distributions typically developed through comparison source samples or a priori knowledge developed using non-intrusive techniques. Chemical fingerprinting has successfully been used for PFAS source identification several times.
This fantastic image from Per- and polyfluoroalkyl substances in Chinese and German river water – Point source- and country-specific fingerprints including unknown precursors does an excellent job showing how testing for specific chemicals can develop a “fingerprint” for specific sites and introduces some challenges to that technique in the form of unknown precursors. Manufacturing sites are plotted and labeled in the left panel, their specific chemical fingerprint as percent of total load is given in the center panel, and the TOP assay was used to show that some of the targeted endpoints were from untargeted unknown precursors
Isomer Analysis
Isomer analysis, isomers are compounds with the same formula but differing chemical structures. PFAS are generally produced through either electrochemical fluorination (ECF) or telomerization. ECF products contain approximately 70–80% linear structures and 20–30% branched isomers; telomerization yields relatively pure linear or isopropyl branched isomers. This technique also has been used several times for PFAS source identification.
Isomers elute at different points during HPLC. Branched forms of PFAS elute after linear PFAS and the more branched it is the slower it typically elutes. Image from Eurofins
Chiral Analysis
Chiral analysis is a very unique subset of isomer analysis. The easiest way to think about chiral isomers, or enantiomers as they’re also known, is your right and left hand. Your hands are the same “isomer” except for an asymmetry so if you line your hands on top of each other palms down they do not match however, palms together they do. This is the same concept behind chirality. Manufactured compounds (such as PFAS) are racemic mixtures which means they contain the same or near equal enantiomer ratios. Since enzymes are always chiral, biotransformation is normally enantioselective. Chiral analysis can show if biotic uptake is due to precursors or direct source and has been used for this purpose. While I am not aware of any studies, this kind of analysis may also be able to differentiate weathering and precursor transformation for example between manufactured PFOA against PFOA degraded from fluorotelomer alcohols.
PFOA enantiomers which can be helpful in elucidating precursor loading
Isotropic Analysis
While isomers have the same chemical formula but distinct structures; isotopes are elements that have the same atomic number but different atomic mass. Isotopic Analysis means techniques measuring the mass of different stable isotopes, typically carbon, hydrogen, oxygen, nitrogen, and chlorine although there are many other possibilities. Unless something is ionized its protons must balance charge with electrons however, neutrons, which carry no charge, affect the weight allowing for this type of analysis. There are three main Isotopic Analyses which fall into this category: bulk, compound specific, and positional specific.
Elements are tracked by protons, unless an atom is ionized, the charge must balance so protons equal electrons; the neutrons may vary in stable compounds which is the basis for Isotopic Analysis
Bulk Stable Isotropic Analysis (BSIA)
Bulk Stable Isotropic Analysis is a specific type of isotropic analysis that measures the total concentrations of stable elements in a sample and can be correlated to the specific element in the releasing source. While I do not know any direct applications to PFAS yet, this technique has been used before to combat pharmaceutical counterfeiting.
The assumption that root water uptake and within-plant water transport are non-fractionating is slowly crumbling. Several studies such as this one from Javier de la Casa have reported offsets between plant and source water stable isotope composition. Without proper accounting, these isotopic offsets can result in the erroneous source water attribution and uptake overestimations by vegetation. This image shows a shift in soil water excess against line conditioned excess the green dots are where both LC-excess and SW-excess plus the corresponding standard error were negative.
While CSIA is not yet proven for PFAS, analogies can be drawn to chlorinated solvents. Since several manufacturing processes and raw materials are used to make chlorinated solvents each solvent tends to have different δ13C, δ37Cl and δ2H signatures for specific VOCs which can allow distinguishing different contaminant sources at the same site, identifying a contaminant from an off-site source located upgradient, as well as establishing links between observed compounds and emitting sources. Image courtesy of Terus Environmental
Advanced statistical techniques such as principal component analysis can also assist in forensic studies. PCA is designed to reduce a dataset to its principal components by taking an original dataset and finding a new smaller set of variables that still describes the most variance in the original dataset – that is to say to take the chemical inputs and reduce it to source inputs. PCA relies on eigen values and eigen vectors to reduce the dimensionality of a dataset.
A principal component analysis for PFAS profiles. The score plot is shown to the left and the loading plot is shown to the right. In the loading plot, PFCA are colored purple and pink, PFSA are colored green, and PFOS precursors are colored yellow. In this study PCA was used to aid in PFAS source identification.
PCA was discovered in 1901 by Karl Pearson. Pearson was a brilliant but misguided statistician who founded mathematical statistics along with the world’s first statistical department but is also the poster child for scientific racism. Image from the American Statistical Association. I wonder why they didn’t decide to call themselves the American Statistical Society.
Careful analysis on core parts can assist in developing timelines, while unproven for PFAS it has been used for petroleum and chlorinated solvents cases. Image from Britannica
Some PFAS Forensics Considerations
PFAS forensics is a rapidly evolving science with many unknowns. However, it can draw many parallels to petroleum forensics which has a very deep body of knowledge around it because of the environmental liability associated with petroleum. For example, both are made of complex chemical mixtures enabling chemical fingerprinting for ready source identification. Despite a varied chemical composition, there are a few constants with PFAS. For example, Perfluoroalkyl acids (PFAAs) are strong acids that are anionic at environmentally-relevant pH. PFAAs are extremely persistent in the environment and do not degrade or transform under typical environmental conditions polyfluoroalkyl substances include compounds that have the potential to transform into PFAAs and are known as precursors. Carbon chain length and functional moiety control sorption and therefore transport. High sorption capacity implies slower environmental transport and vice versa.
This image I made helps to show major sorption potential of various types of PFAS with the defining characteristics listed on the sides.
Some specifics that make PFAS forensics unique are:
With no known natural formation there is a source responsible somewhere.
Formulation can help establish dates. PFAS are entirely anthropogenic first starting in 1938 with several types not produced till much later. Presence of ether-ified PFAS, such as HFPO-DA (GenX Chemicals), for instance implies a 2000s source at the earliest.
Broad industrial use means many sources exist and differentiation may be important.
PFAS typically had industrial formulations to meet performance standards eg being able to extinguish a fire in a set time and not chemical composition standards so the chemical composition varies through time. In other words PFAS formulation depends on production year. Commercial formulation and usage profiles can identify sources.
Individual PFAS measured are only a fraction of total PFAS.
Lowered measured concentrations lead to increased uncertainty.
Transport properties can additional sources. For example, if PFOA is ahead of PFHxA it can indicated separate releases since the longer chained PFAS has lower transport capabilities.
PFAS are generally resistant to weathering and transformation (hence the term “forever chemicals”) however, precursors may occur. For example fluorotelomer alcohols may transform into perfluoroalkyl carboxylic acids.
Ratios of precursors (such as FTOHs) to terminal end products (PFAAs) should increase (ie fewer FTOHs and more PFAAs) with time and distance from sources. There should be a precursor gradient in other words.
PFAS tend to accumulate at interfaces for example between bulk liquids and L- or D-NAPLs, soil/water, soil/water and the atmosphere and so forth. In fact, this tendency has lead to foam fractionation as a potential treatment method.
PFAS tend to accumulate in muscle as opposed to adipose (fat) tissue unlike most contaminants.
Linear compared to branched PFAS should increase with distance from point source because most Br-PFAS have a higher water solubility and faster biological elimination from organisms which also results in faster biotransformation closer to the source.
Due to biotransformation, specific environmental PFAS concentrations should not be used to predict biotic uptake (take total organofluorine into account).
Low water concentrations compared to biota (hence implied high bioaccumulation factors) can indicate that water is not the only source.
Age-dating may be possible using specific diagnostic ratios.
Practically, it is impossible to remediate global PFAS contamination however, managing PFAS hotspots through forensic investigations may significantly reduce global contamination’s extent. There are many parallels which can be drawn between petroleum forensic investigations and PFAS as well as many well-developed techniques to assist in source identification however, it is still a rapidly evolving field. The goal of PFAS forensics, and really environmental forensics, is ultimately to develop legal as well as scientific defensible conclusions related to source attribution. To that end, multiple independent lines of evidence should be used to validate and strengthen conclusions. If you learned something or enjoyed this article (I know I separated those but for me they tend to be correlated!) take a look at some other articles I have written on PFAS.
The public comment period for listing 9 PFAS as RCRA hazardous constituents ends on 8 April. This covers what that means and how to comment.
The public comment period to list some PFAS as hazardous constituents under the Resource Conservation and Recovery Act ends on 8 April 2024.
The public comment period for the EPA proposal to list 9 PFAS as hazardous constituents under the Resource Conservation and Recovery Act (RCRA) ends on 8 April 2024. You may submit a comment here. The 9 PFAS are PFOA, PFOS, PFBS, HFPO-DA, PFNA, PFHxS, PFDA, PFHxA, and PFBA. This includes the 6 PFAS which were have a proposed maximum contaminant level under the Safe Drinking Water Act: PFOA, PFOS, PFHxS, HFPO-DA, PFNA, and PFBS. It may be helpful to review the article on PFAS nomenclature. The intent of this article is to encourage informed public participation in the rule making process. To that end, I plan on covering what RCRA is, what a hazardous constituent is, what that means, and what I, acting in my own personal capacity not representing my employer, think. Please remember that my views are my own and I do not work in this area!
RCRA Introduction
RCRA was first signed into law 21 October 1976 and had major amendments in 1984, 1992, and 1996. RCRA itself is an amendment to the first federal solid waste statute (the Solid Waste Disposal Act of 1965) which is typically included in the term. RCRA governs solid and hazardous waste disposal in the United States and is known for its “cradle to grave” management framework. This law has multiple subtitles, the most referenced are Subtitles C, D, and I.
An overview of the types of waste which exist under US law, thanks for the visual Wikipedia.
RCRA Subtitle C
Subtitle C establishes the cradle to grave framework for hazardous wastes which means from the point of generation through transportation, treatment, storage and disposal hazardous wastes must be tracked, handled, recorded, and stored in specific ways.
RCRA Subtitle D
Subtitle D covers for non-hazardous solid wastes. Among other things it banned open landfills. This section covers sludge from industrial wastes, wastewater treatment plants, and drinking water plants as well. It also excludes small quantity generators from having to follow Subtitle C requirements.
RCRA Subtitle I
covers underground storage tanks (USTs) containing petroleum or other listed hazardous substances and provides technical, monitoring, and reporting standards for them.
A note on RCRA Special Wastes
Several wastes, known as “special wastes,” are industrial wastes which were exempted from Subtitle C and includes oil and gas exploration wastes (such as drill cuttings, produced water, or drilling fluids), coal combustion residuals (fly ash, bottom ash, slag waste and flue-gas desulfurization wastes), mining waste, and cement kiln waste.
What is a Hazardous Constituent?
A hazardous constituent is not a hazardous waste. Instead, it is anything listed in 40 CFR part 261 Appendix VIII. A hazardous constituent listing is a step toward a potential hazardous waste listing. To list a waste as a RCRA hazardous waste under 40 CFR 261.11(a)(3), the waste must contain a hazardous constituent listed on Appendix VIII and determine that it is capable of posing a substantial hazard. Additionally, when a corrective action is required, hazardous constituents are expressly identified for consideration and RCRA section 3004(u) requires that any permit issued to a treatment, storage, or disposal facility after November 8, 1984 requires corrective action for all hazardous waste or constituent releases from solid waste management units at the facility. There are additional regulations surrounding hazardous constituents in parts 261, 264, 265, 268, and 270 however, these are not particularly relevant here. To be listed as a as hazardous constituents under RCRA, a substance must have been shown in scientific studies to have toxic, carcinogenic, mutagenic, or teratogenic effects on humans or other life forms.
Does this affect drinking water?
I do not believe so because hazardous constituents do not make themselves, or the wastes containing them, RCRA hazardous wastes. Only hazardous waste treatment storage or disposal facilities are subject to RCRA corrective actions according to 42 U.S.C. 3004(u)(v). I supposed it is possible that a drinking water plant is a hazardous waste treatment, storage, or disposal facility but that would be novel for me. There’s also a domestic sewage exclusion in 40 CFR 261.4(a)(1), which excludes domestic sewage and any mixture of domestic sewage and other wastes that passes through a sewer system from being considered solid wastes (with some exceptions). However, remember folks I’m not a lawyer and don’t know law.
Why is it important to submit a comment?
Simply put the EPA generally listens if you have a well thought out point and it is important to participate in the laws which govern you.
How to submit a comment
To submit comments, just click the “submit a formal comment” button as shown in the picture below. You can also view all comments submitted. Once the public comment period closes, the EPA reviews all the comments and replies to every one; I’m glad I wasn’t working on this Clean Water Rule which received over 1,000,000 public comments.
Click the big green button on the middle right of the screen!
What do I think?
I believe that the EPA has shown that the nine PFAS, their salts, and their structural isomers meet the listing criteria for RCRA hazardous constituents because there is plenty of detailed, peer reviewed, well established scientific studies that show that these PFAS have toxic effects on humans or other life forms. I believe that it would have been better if rather than listing individual chemicals a structural definition was provided.
I understand the argument that there may not be enough evidence to show that a structural definition should apply however, to quote:
To be honest, PFAS is starting to resemble Christopher Duntsch, also known as Dr. Death. He is one of the only, if not the only, surgeon to face felony accounts for maiming his patients. This is because every doctor is human and humans make mistakes. The prosecution successfully argued that Duntsch should have known he was likely to hurt others unless he changed his approach, and that his failure to learn from his past mistakes demonstrated that his maimings were intentional. Likewise, with PFAS, I feel that even though we may lack specific studies for all perfluoroalkyl carboxylic acids or perfluoroalkyl sulfonic acids from say C4-C20 but at this point are we learning from similar enough chemicals? Baseball is three strikes and you’re out; this listing includes 5 perfluoroalkyl carboxylic acids, 3 perfluoroalkyl sulfonic acids, and 1 perfluoropolyether carboxylic acids could we not just say perfluoroalkyl carboxylic acids or perfluoroalkyl sulfonic acids at this point? How different does something have to be so we prevent regrettable substitutions?
The face of PFAS? No, just a guy whose failure to learn showed that his mistakes were intentional. Photo from the Dallas County Sheriff.
Conclusions
Even if you don’t agree with me you should participate in your democracy! I plan on submitting a comment agreeing with this, if you don’t agree with it why not submit a comment to balance me out? Don’t worry if you miss this opportunity, there are many opportunities to participate in federal decision-making and occur before a rule is proposed, after a rule is proposed, and even after a rule is finalized as this handy site from Harvard’s Environmental and Energy Law Program shows.
A contribution to the circular economy; fish excrete nutrients which algae take up and are then fed to Daphnia magna which is then fed back to fish.
The basic concept in my paper is that aquaculture effluent (fish farming wastewater) is high in excreted phosphorus and nitrogen which cause eutrophication in lakes and must be managed. Algae uptake nitrogen and phosphorus into their biomass and Daphnia magnaeat algae which can then be fed back to shrimp and fish larvae.
Project Summary
Recirculated aquaculture systems (RAS) are often seen as the future of aquaculture because of well-documented issues surrounding wild capture or open-net farming. One engineering problem for RAS are nutrient discharges, which cause water eutrophication (water body senescence or aging and death). Microalgae are one of the causes of eutrophication, however, microalgae directly incorporate nutrients such as nitrogen and phosphorus as well as carbon dioxide directly into their biomass. Removing microalgae from water is extremely resource intensive but Daphnia magna eat (harvest) microalgae and are a high value fish feed. These D. magna can then be fed to shrimp or fish larvae presenting a nice bio-circular economic production system. This was essentially a lab scale proof of concept for this system. The scientific details are published in the Science of The Total Environment. In future posts, I plan on going into detail some of the motivations behind this project such as eutrophication and the circular economy as well as on the ramifications of this work.
Gratitude
Standing on the shoulders of giants is grandiose for this work but I’m glad to have had tremendous help to slightly push the boundaries of knowledge outwards a little.
Musholm A/S was extremely generous in providing the wastewater used in this study.
The research was supported through the InWAP project grant by the Danish Innovation Foundation, Denmark and Department of Biotechnology, Government of India (Grant no. BT/IN/Denmark/61/KM/2018-19).
Disclaimer
In the future I really should make an omnibus disclaimer then link to it from every page.
The information and views here are my own and I do not speak on behalf of the EPA in any way shape or form. None of the information provided is intended to offer engineering, legal, financial, business, information technology, or any other possible professional advice and the information provided may contain errors or omissions. I will not accept any responsibility or liability for how you use this information. Use it at your own risk and take all steps necessary to ascertain that this information is correct.
The World Health Organization is considering comments for the updated Guidelines for Drinking Water Quality.
The World Health Organization (WHO) is considering adding PFOA and PFOS into its Guidelines for Drinking Water Quality and is seeking public comment on their background document for development of WHO Guidelines for Drinking Water Quality. This document is undergoing rolling revisions and accepting public comment using the form here sent to gdwq@who.int by 11 November 2022. Guidelines for Drinking Water Quality are essentially the WHO’s version of the US EPA’s Health Advisories however, are 5 orders of magnitude higher with 100 ppt individual guidelines for PFOA and PFOS as well as a 500 ppt total PFAS guideline. This 5 order of magnitude divergence between health agencies is primarily because the US EPA used epidemiological studies to define the reference dose while the WHO primarily relied on toxicology. Relying on toxicology, the “WHO considered that the uncertainties in identifying the key endpoint applicable to human health following exposure to PFOS and/or PFOA are too significant to derive a HBGV with confidence” (page 79) while the US EPA did not have that issue. The intent of this article is to go over what the WHO is, why it publishes drinking water quality guidelines, and the comments I submitted. Please remember that my views are my own and do not reflect my employer’s position!
The WHO serves to coordinate and guide public health policy on a global level. It started as the Office International d’Hygiène Publique (OIHP) or The International Office of Public Hygiene of President Wilson’s failed experiment, the League of Nations. After the League of Nations folded on 20 April 1946 many of its functions were eventually rolled into the Untied Nations including the WHO. The WHO has been heavily criticized for decades such as by its former leaders and think tanks. Criticism stepped up sharply during the ongoing corona virus pandemic. Despite all this, the WHO remains virtually the only true global consensus-building public health organization. While its influence has weakened in recent years due to other global public health actors such as the World Bank or the Bill and Melinda Gates Foundation, it still is one of the most broadly recognized and supported organizations dedicated to public health.
Why does the WHO publish drinking water quality guidelines?
The WHO itself has been publishing drinking water quality guidelines since 1958 and in fact the WHO’s grandparents were the International Sanitary Conferences (ISC) first held on 23 June 1851 which were established as a result of a cholera pandemic. The OIHP was initially established to carry out some of the ISC’s recommendations. Cholera is a waterborne disease; a fact made famous by John Snow and the Broad Street Pump. By removing a pump handle Dr. Snow helped deal a blow to the miasma theory of disease and served as a founding father to epidemiology; a subject I have a case study in.
The WHO currently recommends individual provisional guidance values of 100 ppt for PFOS and PFOA as well as 500 ppt for total PFAS. These numbers exactly mirror the EU Drinking Water Directive and are substantially higher than the US EPA recommendations which are 0.004 ppt (or 4 parts per quadrillion) and 0.02 ppt (or 20 parts per quadrillion) for PFOA and PFOS respectively. A key reason why these values are so dramatically different is that the US EPA considered epidemiological studies while the WHO did not.
Throughout the document the WHO uses older thoughts on PFAS and consistently cites the 2016 health advisories. The US EPA has the most current human health toxicity assessments for PFAS however, the WHO consistently lists them last.
On page 63 the WHO states (the numbers in the quote are line numbers for that page) “PFOA exposure is associated with clear 23 evidence of carcinogenic activity in male rats based on the increased incidence of liver 24 adenomas and pancreatic acinar cell tumours.” It is therefore not possible using current evidence 25 to exclude PFOA as a human carcinogen”. This wording reflects the US EPA’s 2016 position; more recent human and animal studies lead the US EPA to conclude that PFOA is a more potent carcinogen than previously thought.
I am not enough of a health scientist to know or provide a meaningful analysis on the health aspects of the document other than the superficial one I just provided pointing out the WHO is using older science. Normally in the debate between epidemiology and toxicology, toxicology points to a more dangerous substance than the epidemiological studies. Here, due to the preferred analysis by these organizations it appears to be flip flopped. I would personally prefer to err on the side of caution; especially since drinking water according to the UN is a fundamental human right.
Why I submitted comments to the WHO
Simply put the WHO generally listens if you have a well thought out valid point which conforms to their purpose. During their last request for comment I (and probably quite a few other people) made quite a few recommendations which were incorporated into this draft document. For example, I recommended they:
Take into account Xiao’s paper which shows that PFAS can be generated during advanced oxidation processes. This also changed their practical considerations on monitoring so was quite a substantial change to the document.
Take out the octanol water partitioning coefficient (Kow) from their table of physicochemical properties because PFOA and PFOS are both hydro- and lithophobic so bifurcate into its own layer between octanol and water. Although some people report values, these values are not reflective of the ground truth since the standard test was not designed for that type of material. They also changed some of the other values such as the boiling point and melting point because the predicted range was larger than the experimental range.
Specify that anion exchange deals with anionic PFAS since there are cationic and neutral PFAS so there were some changes to those sections as a result.
Drop the “s” from the PFAS acronym for plurals because a substance cannot simultaneously be per- and polyfluorinated so the plural is already implied.
Use the OECD definition of PFAS which they updated.
Use updates I provided on page 71 about characterizing EPA methods 533 and 537.1
One of my comments was almost incorporated word for word on page 74 related to chain length and functional group removal efficacy; a conclusion I partially took from this Sörengård et al. paper.
Previous comments which were not accepted
Not all my previous comments were accepted. This goes to reflect that two people can look at the same data and draw different conclusions. Especially when the topic is a matter of policy there is often no “correct” answer although there are often clear cut “incorrect” answers. I am going to use this section to highlight some of the comments I made which were rejected, why I made those comments, and potentially the reason why the comment was rejected.
I recommended against using percent removal as a characterization of process efficiency. You can think of properly designed granular activated carbon or anion exchange beds as towels wiping up liquid (contaminant). When the towel is dry and the spill is small it picks up all of it quickly. A wet towel mopping up a large spill may not clean everything or may not clean it quickly. Try and keep that analogy in mind for a contactor. The photo below shows one mode for thinking of breakthrough. Better ways to characterize the efficiency are to use media usage rate or bed life. I believe that the WHO used percent removal because it makes it easier to compare to membrane filtration although again, I disagree with this characterization.
This diagram shows one way of thinking about breakthrough although it is one of two main conceptual processes currently in the vouge.
I provided references which show greater removal percentages for sorption that the WHO quotes. There are many however, the US EPA drinking water treatability database captures many such examples. The WHO is also much more pessimistic on anion exchange than I believe is warranted based on the data. There are both full scale, pilot, and bench studies included. I do not really know why the WHO was cautious there compared to their membrane section where results were more often accepted at face value except potentially that was due to the declining efficacy over bed life which again, is why I suggested percent removal is a bad way to measure sorption process efficiency.
The WHO focuses on source water monitoring. In general, this is a good approach however, I do not agree with it for PFAS. PFAS is not known to and is unlikely to leach or permeate into drinking water supply. Likewise, PFAS can be generated during treatment when advanced oxidation (and potentially advanced reduction) processes are used. If resources are constrained it makes more sense to me to monitor the finished water rather than source water if only one is to be monitored especially since source waters are unlikely to change. The counter argument is that only specific wells could be contaminated, and it would make sense to shut down those wells and not have to treat. If you only monitor finished water, you will miss that level of detail. If resources are constrained and you only monitor the influent, you’ll miss that anyway. To me, this is a good example of two reasonable policy positions based on the same facts with divergent conclusions.
In the previous document, the WHO referenced replacement chemistries; specifically short chained PFAS. I recommended that esterified replacement chemistries be mentioned as well such as HFPO-DA (also known as GenX chemicals), ADONA, and Nafion byproducts. Instead, the WHO removed references to replacement chemistries. This is a good compromise because there are many replacement chemistries available.
My comments on the current draft
On this new draft the comments I have submitted to the WHO using their form emailing to gdwq@who.int (11 November 2022 deadline) are:
The recommendation on page 70 that PFAS monitoring is only required when there is a reasonable source nearby is not protective of public health or in the best interests of society at large. As this document points out PFAS is capable of long-range transport and deposition. PFAS has been found in the artic and Antarctic as well as other remote areas. Additionally, airports; military sites; landfills; wastewater treatment plants; carpet, upholstery, wax, and paper product manufacturers; or spreading biosolids (composting) are all PFAS sources. Rasstadt, Germany was contaminated with composting from used food containers for example. I do not believe that you can successfully perform a risk assessment given the diverse set of sources, low toxicity thresholds, and long-range transport capabilities.
Page 72 lines 8-9 state (line numbers in parathesis): “Blending or diluting PFAS contaminated source water with uncontaminated water may be a (9) cost-effective and viable option for some water systems.” As there is ultra-low toxicity and PFOA as well as PFOS have been identified as likely carcinogens I do not believe that deliberately exposing people to these contaminants through diluting or blending is an appropriate course of action unless there are no other alternatives such as treatment (this would be an economics question) or source substitution.
Page 76 provides information on PFAS removal through sorptive technologies. I believe, and have provided references above in this article, that significantly lower treatment standards are possible.
On page 16 lines 27-30 it states (line numbers in quotes): “In 2019, the US EPA conducted a broad literature search to evaluate (28) evidence for pathways of human exposure to PFOA and PFOS, and in 2021 released a draft (29) analysis that supports application of a 20 percent relative source contribution for PFOA and (30) PFOS in drinking water (US EPA, 2021b,c).” This seems to overstate the strength of the conclusion the EPA made in those health advisories. As I mention in this article, the EPA’s position was that there was insufficient evidence to deviate from a 20% default value; not that evidence supported a particular value.
On page 4 line 37-39 it states (line number in parentheses): “PFOA remains possible, even where it is no longer (38) manufactured or used due to its legacy uses, degradation of precursors, and extremely high (39) persistence in the environment and the human body.” I believe this is also true for PFOS and that disclaimer should be added to that section as well.
Page 74 lines 45-46 deal with anion exchange resin regeneration. Greater than 95% resin regeneration has been demonstrated in literature here, here, and here although it may not be practical for utilities from a safety and/or cost prospective.
On page 9, the WHO references this Boone et al study; when the study was published the conclusion that only one monitored drinking water plan exceeded the EPA’s HAs was valid however, the HAs were updated. That changes the study conclusion from one drinking water plan exceeding the EPA’s HAs to all quantitatively monitored plants exceeding the HAs, a significantly different conclusion.
Conclusion and Key Take Aways
Over time, scientific consensus points to greater and greater awareness of the dangers PFAS pose. Generally, we thought these chemicals were safer in the past than most scientists do today. The WHO, in its role as a policy leader, has developed a significantly less stringent health recommendation than even the old 2016 US EPA HAs on the dangers of these chemicals by not weighting epidemiological evidence the same way. The WHO standard exactly mirrors the EU standard under the drinking water directive. The WHO is a reasonable organization and solicits public comment and feedback as well as generally listening to it. I highly recommend you share your opinions with the WHO regardless of whether you agree with me and take an active role in global public health.
In general, there are three broad strategies for PFAS analysis:
1. Target analysis
2. Total fluorine (organic fluorine) methods
3. Non-target analysis including suspect screening and the total oxidizable precursor (TOP) assay (TOPA)
PFAS analysis is severely complicated by the prevalence of fluorochemicals in laboratory equipment particularly PTFE. For example, PFAS is widely prevalent in HPLC solvent inlet tubing and PFAS from felt tip permanent markers used to mark containers during sampling campaigns.
Target analysis summary
Target analysis targeted methods typically involve either liquid or gas chromatography (LC or GC) coupled with mass spectrometry (MS) and require a reference standard for quantification. Standards are only available for select PFAS and only these specific substances can be quantified. Target analysis yields accurate concentrations but does not provide the total PFAS load.
Total fluorine methods summary
Fluorine is a sum of its inorganic and organic constituents; this insight forms the basis for quantification attempts by total fluorine methods. As PFAS are organic molecules, inorganic fluorine is typically removed from the analysis and absorbable or extractable organic fluorine is measured. Due to differing chemical properties among PFAS, the extraction method chosen will not be suitable for all PFAS classes. Absorbable organic fluorine relies on choosing a suitable absorbent so suffers from the same difficulties.
Non-target analysis summary
Non-target analysis uses chromatography coupled to a high-resolution mass spectrometer and can identify previously unknown PFAS. These methods tend to rely on quadrupole time-of-flight and linear ion trap-orbitraps which are not common instruments. If reference standards are available, similar detection limits to targeted analysis can be achieved. The TOPA deserves special mention as this method performs targeted analysis then attempts to oxidize all precursor compounds into compound endpoints which have standards then performs targeted analysis again to see the difference and theoretically quantify the precursor load but not the specific precursors. These methods suffer from the high technical capacity and equipment required to employ them.
Targeted Analysis
Targeted analysis is currently the only form of analysis which can support drinking water regulatory action because it is able to quantify extremely low PFAS levels; generally around 4 parts per trillion (ppt). In general, LC-MS/MS or GC-MS/MS is used. Reference standards are only available for select PFAS so only select PFAS may be quantified. Which PFAS have standards is driven both by the ability to synthesize extremely high purity samples, regulatory emphasis, and economic viability for the producers. The main PFAS which have standards are per- and polyfluorinated acids (PFAA) – particularly the carboxylic (PFCA) and sulfonic acids (PFSA) as well as the etherified versions of these. As a quick reminder PFCA end in “O” such as PFOA and PFSA end in “S” such as PFOS. The etherified versions tend to have a less standardized nomenclature structure such as “GenX chemicals” or ADONA.
Targeted analysis is well established for various matrices. For example, USEPA Methods 537.1 and 533 together cover 29 PFAS (537.1 focuses mainly on long chain PFAS and covers 18 while 533 was developed mainly to cover some more short chained PFAS and covers 25 PFAS; there are 14 PFAS which overlap between the standards). The German Institute for Standardization (DIN) has also published standard methods DIN 38407-42 and 38414-14. DINs are not freely available like the American methods so I will not link to a store here however, the DINs are broadly similar to the American methods. All these methods use solid phase extraction (SPE) followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). As these methods rely on solid phase extraction, the method efficacy declines with chain length. In other words, the quantification and detection limits for short chained PFAS are higher than they are for long chained PFAS.
As mentioned in the nomenclature article, PFAS may come in “linear” or “branched” forms. These targeted methods may detect branched forms however, branched standards are not widely available and ignoring these will result in a low bias. Linear to branched isomer ratios can also help to identify the PFAS sources. The USEPA Methods 537.1 and 533 include technical notes for dealing with branched isomers.
The DINs note that these methods can be extended to other PFAA with appropriate standard availability however, volatile fluorotelomers (like fluorotelomer alcohols) cannot be determined using these methods.
Comparison of EPA methods for PFAS determination in water; EPA 1633 (aqueous samples), EPA 537.1 (drinking water), and EPA 533 (drinking water). As you will notice the methods are broadly similar and will not work for volatile PFAS.
Total fluorine methods
Total fluorine (TF) is the sum of Inorganic Fluorine (IF) and Organic Fluorine (OF) sometimes called Total Organic Fluorine (TOF). TOF includes fluorine content of all PFAS and their precursors in the sample. TOF methods cannot however separate out organic fluorine contained in medications or other common uses from PFAS. There have been exceedingly few studies quantifying TOF fractions from PFAS compared to medications or other uses of organofluorine. Additionally, TOF methods have much higher quantification limits than targeted analysis, typically around 100 ppt. These two limitations make TOF methods suitable for screening but not protective enough of public health to seriously be used in drinking water regulation. Remember the interim health advisories (HAs) for the apical effects of PFOA and PFOS were 0.004 and 0.02 ppt respectively, so 100 ppt is 4 or 5 orders of magnitude larger than the level at which no apical effects are expected. Additionally, organic fluorine methods only measure the fluorine while the HAs measure the full molecular weight. For example, PFOA (C8HF15O2) has a molar mass of 414.07 g/mol but the mass of fluorine only weighs approximately 285 g/mol PFOA meaning that only about 69% of each PFOA molecule would be quantified assuming perfect extraction and quantification. The exact ratio of fluorine to the overall molecular weight is species dependent.
Organofluorine analysis requires the organic fluorine to be extracted – Extractable Organic Fluorine (EOF). There will always be some organofluorine which cannot be extracted and some which can be extracted but cannot be quantified. Extraction can be the same as for targeted methods. However, due to the large variability between the PFAS chemical composition, the extraction method will influence the test results. Likewise, similar to targeted methods, there is worse extraction efficiency for shorter chained PFAS and specific substances such as trifluoroacetic acid. A special EOF method is known as absorbable organic fluorine (AOF). During AOF, the sample is typically absorbed to a mixed-mode weak anion exchange SPE; again similar to targeted analysis methods.
The most common total fluorine methods are: combustion ion chromatography (CIC), particle-induced gamma-ray emission spectroscopy (PIGE), instrumental neutron activation analysis (INAA), X-ray photoelectron spectroscopy (XPS), and 19F nuclear magnetic resonance spectroscopy (19F NMR). Other methods are under development including: inductively coupled plasma mass-spectrometry (ICP-MS), continuum source molecular absorption spectrometry (CS-MAS), defluorination with sodium biphenyl (SBP), potentiometric and fluorimetric detection, and reversed phase LC-UV or GC coupled with a flame ionization detector (FID), electron capture detector (ECD), or MS. CIC is currently the most discussed TF method.
Non-targeted Analysis
Non-target analysis for PFAS typically uses chromatography coupled to high-resolution mass spectrometers to identify previously unknown PFAS. These methods tend to rely on quadrupole time-of-flight and linear ion trap-orbitraps observed accurate masses, isotopic fingerprints, and MS/MS fragments. Accurate masses, isotope patterns, and molecular feature fragmentation patterns obtained from high resolution mass spectroscopy (HRMS) are compared to databases with known PFAS, such as the USEPA CompTox Chemistry Dashboard, NORMAN Suspect List Exchange, MetFrag, and STOFF-IDENT. Measured chemical responses are compared across two or more sample groups in a process known as fold-change comparison.
The Total Oxidizable Precursor (TOP) Assay (TOPA) was developed by Houtz and Sedlak in 2012 to quantify concentrations of difficult-to-measure and unidentified precursors of PFCA and PFSA in urban runoff. Essentially a sample is measured following conventional targeted analysis methods and then samples are exposed to hydroxyl radicals generated by persulfate thermolysis under basic pH conditions and measured following conventional targeted analysis methods again. Comparing pre- and post-oxidation concentrations the PFAA precursor load can be estimated. Unfortunately, oxidation conversion yields are compound dependent and many factors affect the oxidation process. Oxidation completeness can be tracked by adding a 13C mass labelled precursor however, this again is dependent on the specific compound chosen. Additionally, the endpoint compounds selected for targeted analysis affect the results dramatically. Activated persulfate does not generally oxidize PFSA so this can only really provide inference on PFCA precursors. The TOP assay is also labor intensive, requiring twice the number of samples and more than twice the amount of work to produce a single result. The TOP assay does provide an indication of PFAS precursor load without requiring as advanced equipment or training as non-targeted analysis.
Image from CDM Smith which summarizes the TOPA; essentially targeted analysis is run, precursors are oxidized as much as feasible and targeted analysis is re-run. An important point is that activated persulfate does not readily oxidize PFSA so it only really provides inference on PFCA precursors.
Conclusions
Each strategy selected for PFAS analysis carries with it its own unique strengths and drawbacks. Under most current toxicological frameworks employed by regulatory agencies targeted analysis is the only real viable option however, this can miss many PFAS. Total fluorine methods are several orders of magnitude too imprecise to accurately protect public health but capture most PFAS. Non-targeted analysis methods require expensive equipment, much experience, as well as being non-quantified.
A word cloud containing some common PFAS terms. Made using Wordit.
Per- and polyfluoroalkyl substances (PFAS) are a ubiquitous emerging public health threat. PFAS terminology can be extremely confusing because it looks like an alphabet soup of similar acronyms. This article is the second of two on PFAS terminology. The first intended to provide an overview of PFAS structure (including what counts as PFAS), this one intends to help demystify PFAS terminology and nomenclature. These are part of a broader series on PFAS including their serendipitous discovery.
Introduction
PFAS are a large chemical class generally produced in industrial processes which do not produce pure substances; often impurities are introduced to the end product. An isomer is a compound with the same chemical composition as another compound but a different chemical structure. In the PFAS world the terms “branched” and “linear” refer to differing isomers. As a short hand, people often mean all isomers of a particular compound when they name it. PFAS can also be cyclic in which case the linear/branched nomenclature breaks down.
Linear and branched non-polymeric PFAS are typically composed of two parts: a hydrophobic as well as lipophobic fluorinated carbon backbone and a typically polar hydrophilic functional group. The suffix philic means an affinity for and phobic means fear or aversion, the prefix hydro means water and lipo is for lipid or fat.
Structural analogues are compounds similar to other compounds but differing in one aspect. Structural analogues are also known as congeners. An example could be homologues. PFAS with the same functional groups differing in the number of carbons and fluorine atoms in the backbone are known as homologue series. For example, perfluoroalkyl carboxylic acids with 4 fully saturated carbons in the backbone to 12 fully saturated carbons in the backbone would form a homologue series. A homologue group includes all linear and branched carboxylic acids with the same number of carbons in the backbone. For example, the C8 carboxylic homologue group includes linear perfluoroalkyloctanoic acid (PFOA), isopropyl-PFOA, and 3-methyl-PFOA; there are 89 total theoretically possible C8 carboxylic homologue congeners although in addition to the linear form. The picture below shows some C8 carboxylic homologue congeners, while technically separate compounds for ease they are often referred to as a singular entity.
Image courtesy of Battelle Memorial Institute particularly Craig Hutchings and Steve Helgen. While technically different compounds these are often considered together.
Naming Systems
There are 5 main systematic methods currently in use to name fluorinated compounds: the International Union for Pure and Applied Chemistry (IUPAC) nomenclature, the perfluoro nomenclature, code numbers, Chemical Abstract Service (CAS) nomenclature, and F-nomenclature systems. Due to strong similarities, fluorinated organic compounds tend to follow hydrocarbon naming conventions.
Basic Conventions
Many PFAS are acids and may exist as a protonated or anionic form as well as a mixture of both depending on the pH. The pKa values tend to be quite small and scientists generally refer to PFAS with acid functionalities as “acids” rather than carboxylates, sulfonates, or the correct terms even though the dissociated forms may be the only relevant forms. Scientists refer to both the protonated and ionized forms by the same acronyms. Most perfluorinated acids are environmentally anions. Some labs report results in the acidic form, some report anions, and some a mixture. Many times, perfluorinated carboxylic acids are reported as acids (for example perfluorooctanoic acid instead of perfluorooctanoate) and perfluoroalkyl sulfonic acids as anions (for example perfluorooctane sulfonate instead of perfluorooctane sulfonic acid). This has caused confusion. The labs are really measuring the concentration of perfluorinated acid anions present; when the lab reports an acid the lab adjusts for the cation. Most sulfonate standards are prepared from salts and the mass adjusted which is why they are often reported that way. This is especially true for PFHxS, PFOS, ADONA, 9Cl-PF3ONS and 11Cl-PF3OUdS. Section 7.2.3 of EPA Method 537.1 details how to convert to adjust for this.
IUPAC Nomenclature
IUPAC Nomenclature systematically establishes unambiguous, unique, uniform, and consistent compound names based on their chemical structure. IUPAC Nomenclature can be used for all organic compounds and is not specific to PFAS. IUPAC Nomenclature is quite literally a book containing many precedents and steps however, the general simplified steps for IUPAC Nomenclature are:
Identify the longest carbon chain. The longest carbon chain is also known as the “parent chain.”
Identify any groups off the parent chain.
Number the carbons in the parent chain so that the groups off the parent chain have the lowest number.
Number and name the groups just counted.
Put all the name components together in alphabetical order; prefixes such as di- are not used for alphabetical order.
For example, C2F4 is tetrafluoroethene, shown below, is the simplest perfluorinated alkene (fully saturated carbon backbone with no functional groups).
Picture from Wikidata. There are two carbons and a double bond so it is named “ethene.” Tetrafluoro comes from the 4 fluorine atoms attached to the carbons.
Perfluoro Nomenclature
Perfluoro Nomenclature only applied to perfluoroalkyl substances. It is commonly used to quickly identify fully fluorine saturated carbon compounds. For shorter substances using IUPAC naming conventions is still easy and understandable. Most chemists would immediately understand that hexafluorobenzene (C6F6 – shown below) has a cyclic fully saturated carbon backbone. However, for longer compounds such as pentadecafluorooctanoic acid it is difficult to readily tell which is the motivation for Perfluoro Nomenclature. The proper IUPAC name for that compound is actually: 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoic acid which is fairly cumbersome to use further motivating Perfluoro Nomenclature. The pentadecafluoro refers to the 15 fluorine atoms, octanoic acid refers to a carboxylic acid functional group that is off the 8th carbon in a chain. This compound is pictured under hexafluorobenzene.
Picture from Wikimedia. Hexafluoro denotes the 6 fluorine atoms coming off the carbons in the benzine ring. By Buck et al’s or one of the OECD’s PFAS definitions this compound would not be included however, it would be under Glüge et al’s definition. The preferred IUPAC name for this compound is 1,2,3,4,5,6-hexafluorobenzene.
Perfluoro Nomenclature uses the prefix perfluoro along with standard hydrocarbon nomenclature. This simplified naming system has been in place since the 1950s and is the most common naming system among practitioners. The acronyms developed from this system follow a simple pattern; they all start with the prefix PF for perfluoro then have a root based on the carbon backbone, and a suffix denoting the functional group. The table below gives the roots for C1-C14 and the two most common functional group abbreviations are A for carboxylic acids as well as S for sulfonic acids.
Table of roots for specific carbon backbone lengths.
The carboxylic acid (left) and sulfonic acid (right) functional groups. The R represents some organic chain.
The acronym itself provides a well-defined structure for the PFAS compound. For instance perfluorobutanesulfonic acid or PFBS is shown below. The front letters PF stand for per-fluoroalkyl, the B stands for but-, -ane shows there are only single bonds in the carbon backbone which is implied, and the S is for sulfonic acid. PFBA, PFHpA, and PFDA are also shown.
Perfluorobutanesulfonic acid or PFBS. The sulfonic acid functional group is circled in dashed yellow, the carbons are in red, numbered so that the first carbon is nearest the functional group. By convention, the unlabeled connectors are carbon atoms. Carbon always forms 4 total bonds, if 4 bonds are not shown the carbon by general agreement is bonded to a hydrogen.
The table shows the appropriate root color coded, carboxylic acid groups are circled in dashed blue and sulfonic acid groups are circled in dashed yellow. PFBS is perfluorobutanesulfonic acid, PFHpA is perfluoroheptanoic acid, and PFDA is perfluorodecanoic acid. PFBA is perfluorobutanoic acid however, butanoic is sometimes replaced by butyric acid in older works.
Should it be necessary to refer to a specific salt for a perfluorinated compound it is customary to write the salt’s common abbreviation in front of the standard perfluorinated abbreviation then drop the acid from the name. For instance, the ammonium salt of PFOA, ammonium perfluorooctanoate, is often abbreviated APFO. While not strictly included in the perfluorinated system, some polyfluoroalkyl compounds can degrade into perfluorinated compounds. A polyfluoroalkyl compound is one where the carbon backbone is not fully fluorinated. An important subset of polyfluoroalkyl substances are fluorotelomers. Fluorotelomers are substances made from the most common industrial process for perfluorinated compounds, telomerization. In telomerization a transfer agent, known as a telogen, reacts with a polymerizable taxogen (monomer) to produce a telomer. Generally in commercial production, perfluoroethyl (pentafluoroethyl) iodide as a telogen reacts with tetrafluoroethylene oligomers as taxogens, most commonly tetrafluoroethylene, to produce telomer perfluoroalkyl iodide polymers. The perfluoroalkyl iodide polymers are then converted into other substances.
Picture from the Big Chemical Encyclopedia showing pentafluoroethyl iodide reacting with tetrafluoroethylene oligomers to produce perfluoroalkyl iodide polymers.
Similar to perfluorinated acids, fluorotelomer substances are typically named for their functional group. Fluorotelomers often are abbreviated FT followed by their functional group. There are often numbers preceding the abbreviation such as 8:2. The first number represents the total perfluorinated carbon atoms and the second number the unsaturated carbons atoms.
By convention the unlabeled connectors are carbon atoms. Carbon atoms always have 4 bounds and as this field was developed from hydrocarbon chemistry the hydrogens are typically not shown unless part of a functional group. The carbon atom labeled “2” in green for instance has two hydrogens attached to it. An alcohol group is a hydroxyl connected to an aliphatic carbon.
Code numbers
Systematic names are fantastic in precision but can be difficult to use. Unless you work with compounds frequently, memorizing the prefix structures and extra rules, which were glossed over in this article can represent an annoying time commitment. Additionally, it can be error prone especially to infrequent or new users. Industrial PFAS manufacturers such as ICI Fluoropolymers, ISC, DuPont, and 3M developed inhouse shorthands for PFAS. As the inhouse systems were not meant for the general public this initially caused confusion. In Organofluorine Chemistry dichlorodifluoromethane (CF2Cl2) is used as an example to illustrate this. Dichlorodifluoromethane was known as Freon-12 by DuPont, Arcton-6 by ICI, and Isceon-122 by ISC. By 1957 a standardized code number system based on DuPont’s system was adopted and formalized as The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 34 which was last updated in 2019. DuPont’s system was first developed by Albert Henne, Thomas Midgley, and Robert McNary in 1929.
Dichlorodifluoromethane (CF2Cl2), better known as Freon-12, was formerly a popular chlorofluorocarbon halomethane refrigerant now banned under the Montreal Protocol. It is now only allowed as a fire suppressant in submarines and aircraft. Picture from the Gas Encyclopedia by Air Liquide.
In the ASHRAE system for pure compounds, a letter designates the primary purpose of the compound, R for refrigerant, P for aerosol propellant, S for solvent, and the numbers are based on the chemical formula. Sometimes the letter is replaced with a trade name such as Freon. For blends, numbers are assigned sequentially based on ASHRAE data review completion date. For an ASHRAE designation, the first digit from the right is the number of fluorine atoms. The second digit from the right is the number of hydrogen atoms plus one. The third digit is the number of carbon atoms minus one; if this is a zero then that number would be omitted. The fourth digit is the number of unsaturated carbon-carbon bonds, in saturated compounds this number is omitted. If an upper-case B or I appears the number immediately following it is the number of bromine or iodine atoms respectively. There are often lowercase letters following the numeric designations. The first appended letter is for substitutions on the central carbon atom, an x represents a chlorine substitution, y for fluorine, and z for hydrogen. The second appended letter designates substitutions on the terminal methylene carbon, =CCl2 is -a, =CClF is -b, =CF2 is -c, =CHCl is -d, =CHF is -e, and =CH2 is -f. Isomers are also designated by a Z or an E appended to the name for “zusammen” or “entgegen” respectively. Zusammen is German for together and entgegen is opposite; they represent cis and trans isomers respectively.
Cyclic compounds (R300 series), ethers, inorganic fluids (R700 series), and miscellaneous organic compounds (R600 series) have additional rules. The series are specified so the 000 series are methane based compounds, 100 are ethane based, 200 are propane based, and 300 are cyclic. The 400 series are zeotropes and 500 are azeotropes. The 600 series are other organic compounds. The 700 series are inorganic refrigerants such as ammonia, also known as R-717. The 1000 series which are unsaturated organic compounds such as the new R-1234yf refrigerant. R-1234yf is used for about half of all automobiles built after 2018 and it breaks down into short chained perfluorinated carboxylic acids; specifically, trifluoroacetic acid.
2,3,3,3-Tetrafluoropropene also known as HFO-1234yf and R-1234yf. It has a greenhouse gas (GHG) warming potential less than that of carbon dioxide. R-134a, which R-1234yf helped replace, has a GHG warming potential of 1,430 as a comparison. Picture from Wikipedia.
The compound on the left is R-1234ye(E) and the compound on the right is R-1234ye(Z). The part which makes the compound an isomer is circled in dotted blue lines. R-1234 has other possibilities and chemical structures as well which can be further specified by the letters following the numbers. As an example R-1234yc is CH2FCF=CF2.
There are other code systems in use that are more field dependent as well. For instance, chlorofluorocarbons have a numbering system as do halogenated fire extinguishers. The Halon numbering system is in comparison very easy; there are always four numbers and left to right the digits represent carbon, fluorine, chlorine, and bromine atoms present in the molecule. For instance, Halon-1211 (CF2ClBr also known as Freon-12B1) and Halon-1301 (CF3Br which would also be known as R-13B1). On 1 January 1994 the United States banned the import and production of halons 1211 and 1301 under the Clean Air Act to comply with the Montreal Protocol. These halons are still allowed to be used and recycled halons may be purchased. Both Halon 1211 and 1301 have Class A, B, and C ratings. Halon-1211 is a “streaming agent,” and more commonly used in hand-held extinguishers because it discharges mostly as a liquid stream. Halon-1301 is a “flooding agent” and discharges mostly as a gas, allowing it to penetrate tight spaces and behind obstacles making it ideal for enclosed spaces commonly found in aircraft. The United States owns about 40% of global halon-1301 supply and it will likely stay in use for many years worldwide. Halon-1301 is critical as it was formerly the only material usable in enclosed spaces where humans were present.
CAS nomenclature
CAS stands for Chemical Abstract Service (CAS) and it is a division of the American Chemical Society. A CAS number is a unique identifier assigned by CAS to every chemical substance. It includes isotopes, mixtures, alloys, and substances which have unknown or variable composition. CAS numbers do not contain information about the substance structure unlike all previously discussed naming systems, simplified molecular-input line-entry system (SMILES), or the IUPAC International Chemical Identifier (InChI) system.
The same PFAS chemical in different forms will have differing chemical properties because of structural differences. For example, PFOS (perfluorooctanesulfonic acid) in its acid form (C8HF17O3S) has a CAS number of 1763-23-1, its potassium salt (C8F17KO3S) 2795-39-3, and its ammonium salt (C8H4F17NO3S) 29081-56-9.
F-Nomenclature
F-nomenclature was accepted by the American Chemical Society as an alternative to perfluoro nomenclature because some early fluorochemistry pioneers disliked perfluoro nomenclature. JH Simons in particular disliked perfluoro nomenclature. Simons invented the electrochemical fluoridization processes which was the first industrial process for producing perfluorinated compounds.
In F-nomenclature perfluoropentanoic acid (PFPeA – a C5 fully saturated carboxylic acid) would be F-pentanoic acid. As an aside, C5H10O2 which is pentanoic acid, is also known as valeric acid because it is the cause of the unpleasant smell in valerian.
Picture of valerian by Ivar Leidus. The unpleasant smell these flowers give off is caused by pentaonic acid.
Some elements of this naming system have survived. For instance, the symbol -R which indicates an organic backbone sometimes is written -RF to indicate a perfluoro backbone. Also, placing an F internal to a benzene ring structure is a shorthand saying that all the bonds off the ring not otherwise indicated are fluorine instead of hydrogen. A forerunner to F-nomenclature used a phi (φ) but was generally similar to F-nomenclature.
Other less common nomenclature systems
In the 1970s, J.H. Simons, an early fluorochemistry pioneer, advocated for placing “for” before the final syllable in standard hydrocarbon nomenclature to convey it was perfluorinated. Organofluorine Chemistry gives the following examples: CF4 as methforane and the perfluorinated version of ethene, CF2=CF2 would be ethforene.
Conclusion and Key Take Aways
Most PFAS naming systems are designed to reveal information about the basic chemical structure or function and to facilitate communication. In industrial settings where not many PFAS are used simultaneously it can be easier to use codes to cut down on potential errors common in systematic names. It is important to understand the basic names within your specific use.
This article is one of several on PFAS. You can read about PFAS discovery, structure, or all my articles on PFAS.
Per- and polyfluoroalkyl substances (PFAS) are a ubiquitous emerging public health threat. PFAS terminology can be extremely confusing because it looks like an alphabet soup of similar acronyms. This article is the first of two on PFAS terminology. This one intends to provide an overview of PFAS structure, the second one intends to help demystify PFAS terminology and nomenclature. My previous article on PFAS was on Dr. Roy Plunkett’s discovery of PTFE, a tetrafluoroethylene fluoropolymer.
Scope
The EPA’s comptox database lists over 9,252 PFAS; this is too large a class to name on individual bases. A systematic naming convention has evolved so that much information is conveyed with just the name. There are 5 main ways to name fluorinated compounds: the perfluoro nomenclature, F-nomenclature, code numbers, the International Union for Pure and Applied Chemistry (IUPAC) nomenclature, and Chemical Abstract Service (CAS) nomenclature systems. Additionally, fluorine chemistry as a field has existed long before those five systems were created and naming was not really standardized until Buck et al tried to harmonize conventions in 2011. The idea of this article is to provide an overview of common PFAS groupings, the second article will go into the five naming conventions.
Introduction
PFAS is a general nonspecific name encompassing a group of substances. There is no clear agreed upon definition of what exactly counts as PFAS. The Organization of Economically Developed Countries (OECD), the United States Environmental Protection Agency (EPA), and the World Health Organization (WHO) have all used various definitions. In the paper meant to harmonize conventions, Buck defined PFAS as “highly fluorinated aliphatic substances that contain 1 or more carbon atoms on which all the hydrogen substituents (present in the nonfluorinated analogues from which they are notionally derived) have been replaced by F atoms, in such a manner that they contain the perfluoroalkyl moiety CnF2n+1–.” This definition was the first clear PFAS definition. A moiety means part of a molecule. The OECD/United Nations Environment Program (UNEP) pointed out that Buck’s definition left out many substances commonly recognized as PFAS such as perfluorodicarboxylic acids and recommended the –CnF2n– moiety instead, although there is still debate surrounding this. Buck’s definition was updated by Glüge et al and informed the OECD/UNEP definition. Glüge’s definition expands Buck’s to cover perfluorocarbon chains with functional groups on both ends, aromatic substances with perfluoroalkyl moieties on side chains, and fluorinated cycloaliphatic substances.
Historical Note
As mentioned in the PFAS discovery article, PFAS were initially investigated to replace sulfur dioxide, methyl chloride, ammonia, and other extremely dangerous early refrigerants. This may jog your memory; the first major public PFAS concerns were mainly focused on perfluorocarbons under the 1987 Montreal and 1997 Kyoto Protocols. The Montreal Protocol aimed to limit chlorofluorocarbons. The Kyoto Protocol aimed to limit 7 greenhouse gas (GHG) categories and stated that climate change is real and driven by anthropogenic emissions. The GHG categories included perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs).
Photo courtesy of Wikimedia Commons Green: Annex B parties with binding targets in the second period, Purple: Annex B parties with binding targets in the first period but not the second, Blue: non-Annex B parties without binding targets, Yellow: Annex B parties with binding targets in the first period but which withdrew from the Protocol, Orange: Signatories to the Protocol that have not ratified, Red: Other UN member states and observers that are not party to the Protocol.
Unfortunately, early 2000 environmental scientists adopted the PFC acronym for PFAS instead of the perfluorocarbons identified in the Kyoto Protocol. There is still quite some confusion caused by this. While PFC is used in turn of the millennium PFAS literature it should be avoided now.
General Organofluorine Concepts
Carbon (C) bonded to fluorine (F) is the class basis for PFAS. The C-F bond is extremely persistent and the key factor for the problems PFAS causes as well as its desirable technical properties. Carbon can form up to 4 bonds with other atoms. The first broad distinction is between polymers and non-polymers. A polymer is a molecule made up of repeating subunits called monomers. Polymers often serve as the feedstock to produce other PFAS chemicals, the most widely recognized fluoropolymer is polytetrafluoroethylene (PTFE) which Dr. Roy Plunkett discovered on 6 April 1938.
Picture courtesy of Wikipedia Commons. This depicts PTFE. The brackets show the monomer tetrafluoroethylene, the n symbolizes that this is a repeating structure.
Functional groups often serve as the basis for classification systems. A functional group is a moiety made of a specific structure which causes characteristic chemical reactions which are similar no matter what the rest of the molecular composition is. PFAS chemicals can also exist in multiple states such as acids, anions, cations, and salts which have important implications for their physical and chemical properties. Anionic forms are the environmentally prevalent form and the general form most authors refer to. Some legislation, particularly European Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH), defines substance to include impurities and stabilizers of the main PFAS compound.
Broad non-polymeric structure
Non-polymeric PFAS include perfluorinated and polyfluorinated substances. When carbon is bound only to fluorine except for functional groups it is called perfluorinated and the compound is saturated with F. When some carbon bonds include things other than functional groups or fluorine it is called polyfluorinated and is considered unsaturated with respect to F; hydrogen is the most common other bond. As PFAS stands for “per- and polyfluoroalkyl substances” and no single compound can be both unsaturated and saturated with respect to fluorine simultaneously “PFAS” is by default a plural acronym. Both per- and poly-fluoroalkyl substances are subdivided into classes where the functional groups behave relatively similarly. Two large classes are fluoroalkyl acids and fluoroalkane sulfonamides. These large classes are then subdivided again based on functional groups/moieties. For example, perfluoroalkyl acids are further subdivided into carboxylic, sulfonic, sulfinic, phosphoric, phosphinic, and other acid types. There are about 425 common moiety-based subdivisions within PFAS.
Picture courtesy of The Interstate Technology Regulatory Council. This photo goes over some broad PFAS categories; while only 5 moiety based groups are shown here there are currently over 425 acknowledged nonpolymer moiety classification groups.
In 2017, Wang et al published an iconic chart covering the number of papers published on various PFAS groups reproduced below.
Picture from Wang et al. This shows some broad helpful PFAS classifications. PFCA stands for perfluorinated carboxylic acids, PFSA for perfluorinated sulfonic acids, PFPA for perfluorinated phosphoric acids, PFPiA for perfluorinated phosphinic acids, PFECA for perfluoropolyether carboxylic acids, PFESA for perfluoropolyether sulfonic acids, and PASF for perfluoroalkane sulfonyl fluorides. Examples of groups left off this classification include perfluoroalkyl iodides (PFAI) and many others. The articles mentioned cover 2002 to 2016.
Conclusion and Key Take Aways
There is no clear definition on what PFAS encompass, even within regulatory organizations. There are about 9,252 PFAS substances which are broadly divided into polymeric and non-polymeric substances. Non-polymeric PFAS subclasses are based on carbon chain saturation with fluorine into full saturated (perfluoroalkyl) or non-fully saturated (polyfluoroalkyl) groups. Those groups are subdivided based on moieties/functional groups so that compounds which behave similarly are classified together. An upcoming article will cover the five common classification systems for individual compounds.
Since my previous article on wastewater based epidemiology (WBE) for SARS-Cov-2 monitoring, there have been rapid developments. According to the World Health Organization’s 12 September 2020 update there have been over 28 million confirmed cases and 900,000 deaths worldwide making it a serious global pandemic. For comparison, last year about 1.7 million people acquired AIDS and 700,000 died. There is growing evidence that built environmental systems, particularly ventilation systems and residential plumbing systems, contribute to SARS-Cov-2 spread.
SARS-Cov-2 in the Gastrointestinal Track
The pooled SARS-Cov-2 viral RNA prevalence in stool samples from clinically confirmed cases is only estimated to be around 50% although estimates range from 15% to 84% in this meta-study and review. These studies unfortunately generally did not have many participants; between 9 and 4,243, with most studies having under 60 participants. Likewise, SARS-Cov-2 loads and viral RNA in fecal samples reported between 1,000 and 10,000,000 SARS-Cov-2 copies per fecal milliliter; one study had 153 participants, where only 44 participants (29%) had viral RNA present, while the other studies all had under 50 total participants. That study indicated that there was, broadly speaking, a traceable general shedding pattern. During the initial SARS-Cov outbreak in 2002-2003 and MERS-Cov outbreak in 2012, viral RNA was still present in stool samples over 30 days after the illness. Similarly, patients with SARS-Cov-2 in their stool continued to shed RNA viral positive fecal samples after showing negative respiratory/nasopharyngeal samples. The estimated continued positive shedding duration and percentage still shedding varied greatly but reported means vary between 11 days and 5 weeks in 20% to greater than 70% of patients that had positive stool samples. There is limited evidence to suggest that viral RNA in stool comes from live infectious viruses instead of deactivated or destroyed viruses however, testing for the live virus is difficult to do and few people try. Most studies suggest that SARS-Cov-2 in urine is rare however, some studies report its presence past negative throat swabs.
This guy has about a 50% chance of containing SARS-Cov-2 when excreted from an infected individual
SARS-Cov-2 in potable water distribution
It is extremely unlikely that SARS-Cov-2 can remain viable in potable water systems, especially in the US where 0.2 mg/L chlorine residual minimum must be at temporally farthest tap. While I could not find information on SARS-Cov-2’s survival in chlorinated water, other human coronaviruses are highly susceptible to chlorination. Likewise, I could not find information on SARS-Cov-2’s survival in non-chlorinated tap water which dominates Europe however, other human coronaviruses showed a three log removal (99.9% removal) at 23°C (73.4°F) in 10 days; at 4°C (39.2°F) human coronaviruses do not show a three log removal after greater 100 days. These results are not particularly helpful. Cold inlet tap water’s temperature is normally 10-15.5°C (50-60°F) but can vary from 3.6-“jacuzzi temperature” 39°C (38.6- ≈100°F) in the United States (low value is Anchorage, Alaska and the high value is Death Valley, California). The temperature depends on several factors: water age, water source (surface or ground), season, processed water storage, pipe depth, and ambient air temperature. In aggregate however, I cannot derive a scenario where SARS-Cov-2 would proliferate enough in potable water systems to make someone sick through showering for instance.
SARS-Cov-2 in sewers
Similar to potable water, I was unable to find information specific to SARS-Cov-2 however, information on other human coronaviruses is available. Other human coronaviruses die rapidly in wastewater with three log removal (99.9%) occurring between 2 and 4 days for all temperatures. I do not believe there is a general standard time for sewage to reach treatment plants however, most sewers are designed with a self-cleaning velocity that should be reached daily (between 0.6 m/s and 1 m/s mainly dependent on specific gravity and pipe diameter) and are generally capped at 3 m/s during max flow to prevent erosion. Rochester, NY takes about 24 hours for sewage to reach its treatment facilities which is normal and a decent average proxy. All reputable sources agree that standard wastewater treatment processes, which are designed for virus and bacteria inactivation among other things, inactivate SARS-Cov-2. Likewise, dilution occurs in sewers which should increase the minimum infective dose by lowering the virus’ concentration.
SARS-Cov-2 in residential plumbing
Sewers, unlike potable water, are not generally pressurized and are ventilated to eliminate smells. This little distinction is critical. Circumstantial evidence reported in the Annals of Internal Medicine indicated that 9 people became sick with SARS-Cov-2 from fecal aerosols. This is not the first time that a respiratory disease has been tied to sewage waste vents. The 2003 SARS outbreak at Amoy Gardens in Hong Kong was implicated in 321 cases and 43 deaths. During China’s ultra-strict lockdown, Kang complied camera footage indicating no contact between the sick apartment members and the newly infected group who lived on different floors. Among more than 200 air and surface samples collected, the only ones testing positive for SARS-CoV-2 came from the 15th floor family’s apartment and a vacant apartment’s bathroom on the 16th floor directly above. Tracer gas piped into the 15th floor apartment’s drainpipe exited in the 25th and 27th floor apartment bathrooms. Generally, there is a plumbing “trap” (shaped like a U or P) that has water in it to block smells from rising. These however, can dry out leaving a transmission route for disease. Drying out can occur from non-use or air pressure surges. The ethane tracer gas presence indicates that these traps dried out. Contact tracing and other standard causal patterns did not reveal leads. One team member on Kang’s study indicated that there could also be three other outbreak incidents related to waste vent gases. However, while compelling, there is no iron clad evidence and it is possible the disease was contracted elsewhere. Mechanical bathroom exhaust fans and outdoor air conditions can lead to a favorable environment for SARS-Cov-2 to spread through bathroom exhaust. There should be appropriate caution reading these findings. Many factors must fall into place for this kind of residential transmission. For instance, the proposed transmission route relies on viral infectivity in fecal droplets and aerosols. However, building wastewater systems are a potential reservoir for many other viruses and bacteria, even in the absence of SARS-CoV-2.
SARS-Cov-2 in toilets
Virus-containing fecal aerosols can be produced during toilet flushing after index patient use. These bioaerosols can settle onto surfaces and remain infective. There was a case where a South Korean woman most likely contracted Covid-19 from an airplane toilet. She self-quarantined in complete isolation for three weeks before the flight, did not use public transport to get to the airport, wore an N-95 mask for the entire flight except a visit to the bathroom, all passengers sat two meters (six feet) from each other during boarding, and quarantined for two weeks by South Korean officials on landing. The one asymptomatic sick passenger on the plane used the toilet before her. The most likely transmission route was encountering contaminate surfaces because the airplane used high-efficiency particulate arresting systems. According to Dr. Joseph Allen from Harvard’s T.H. Chan School of Public Health, about 1,000,000 additional particles per air cubic meter are generated when a toilet is flushed with the lid up. These particles can settle on surfaces or linger in the air until someone breaths them in.
Protecting yourself
There are some easy common-sense protective measures you can take to protect yourself. Ensure bathrooms you use are well ventilated, turn on an exhaust fan when entering a bathroom and leave it on when you leave. Make sure the P or U trap isn’t dried out; a bad smell indicates a dry trap. Close the lid when flushing the toilet to help prevent bioaerosols from spreading. Clean and disinfect bathroom surfaces. Most importantly, wash your hands when leaving the bathroom, then try and use a paper towel to touch surfaces including the door handle on your way out.
Potential WBE Advances
To date SARS-Cov-2 Wastewater Based Epidemiology (WBE) relies on the same analytical platforms used in clinical diagnostic testing (eg PCR or antigen testing). WBE does not need to be limited to the monitoring the infectious agent’s nucleic acid or antigens. WBE could target endogenous biomarkers that are significantly elevated in diseased states. This could reduce analytical costs and broaden availability (through immunoassays) or better serving as leading infection indicators (earlier alerts). Urine (as opposed to fecal) biomarkers would also simplify sampling and sample preparation. Since Covid-19 can cause extensive inflammatory damage, biomarker for systemic oxidative stress such as the prostaglandin-like class of substances called isoprostanes are currently being proposed. These biomarkers may be more universally excreted among infected individuals, better track the infection severity, have tighter per-capita excretion ranges (allowing for better case count calibration and estimation), and avoiding a potential under-appreciated problem with using PCR, where RNA fragments may not be originating from viable virus, but rather from virus remnants (litter) from cleared infections. That last issue could overestimate infection incidence or intensity. It is also speculated that patient repeat infection reports are caused by this.
WBE could also be used to test hypotheses involving correlating various community-wide population demographics with the magnitude and duration of SARS-CoV-2 measurements to probe inter-community disparities such as race, culture, income, healthcare availability, and occupation. WBE data could also be examined for correlations with drug manufacturer geographic prescribing data — notably for drugs suspected to improve or exacerbate Covid-19 therapeutic outcomes. WBE could also determine which SARS-CoV-2 subtypes dominate in given populations.
WBE Other Shortcomings
In addition to the difficulties I outlined in my first article on WBE, I have learned about some additional difficulties. Population size estimations are difficult because populations fluctuate due to travel and commuters. The standard approach to this is to measure certain endogenous biomarkers such as cortisol or cotinine then calculate those as daily loads normalized to population sizes. However, some unique population fluctuations have negligible catchment impacts leading to higher uncertainties in smaller populations. Other standard population estimating wastewater parameters used such as Chemical Oxygen Demand, Biochemical Oxygen Demand, or ammonia can reduce uncertainties but can be strongly influenced by the wastewater’s composition. Another is that biomarkers must be relatively stable not only in the sewer system but also through the sampling and storage processes.
Another shortcoming is wastewater itself makes it extremely difficult to extract and quantify biomarkers and chemicals. PCR inhibitors include fats and proteins, as well as humic and fulvic acids. New digital PCR techniques use Poisson distributions, via partitioning samples into reaction wells to lessen these effects.
Previously Unmentioned Successes
WBE can distinguish differences between prescription and consumption of a pharmaceutical. Investigating parent compounds to metabolites ratios or ratios between compound enantiomers in wastewater can distinguish human excretion from direct pharmaceutical disposal in sewers. This distinction ability is important because prescriptions do not necessarily correlate to use. Delayed prescribing is a strategy where doctors prescriptions available but ask patients to delay using them to see if symptoms improve. These initiative successfully reduced antibiotic use in New Zealand, Norway and England; WBE can distinguish how many antibiotics were actually used as opposed to prescribed.
WBE can minimize the tests required to uncover positive cases. Clinical tests need to continually increase test coverage. The ratio between tests required to uncover a single case and total tests is generally the most direct infection extent indicator. A low ratio (when using random sampling) points to a high incidence of infection and therefore the need for more intensive testing until the ratio significantly increases (where increasing testing amounts are required to confirm additional cases). This indicates increasing success in containment or mitigation measures. However, diagnostic tests are never intended for mass surveillance. The tests are generally time-consuming and costly as well as exposing the test administrator. There are two alternatives: increase conventional testing or minimize the tests required to reveal positive cases. Pooled testing procedures increases testing capacity and throughput, especially for PCRs. Pre-targeting subpopulations can help with minimizing the rests required as well. These methods conserve diagnostic tests. Using WBE then can be akin to using a forward observer to improve artillery’s accuracy. This would greatly reduce the demand for diagnostic testing and reduce supply-chain shortages caused by insufficient manufacturing capacity. The metric of success for WBE when used for targeting the use of clinical diagnostic testing would be lower ratios for “Tests Administered” per “Case Confirmed” (counter intuitively, maximize the positivity test rate).
WBE may also be the only way to infer the uninfected population as well as provide perspective on how well diagnostic testing reflects the total population.
You can probably catch Covid-19 from public toilets and in star-crossed circumstances from your neighbor’s toilet. WBE research is developing but remains much more difficult than analyzing for chemicals such as illegal drugs because there are differences in viral shedding patterns, total shedding, viral attenuation during sewer travel, and determining statistically representative sampling. Even in other applications, matrix separations pose difficulties for WBE. WBE is still an effective epidemiology tool to rapidly monitor disease spread and trends, especially when paired with other contemporary measures. The preponderance of evidence suggests that CoVs are less stable in the environment than other enteric viruses. Water recycling guidelines may have to be revised in light of emergent diseases and viral shedding into sewer systems. Effective surveillance systems are key for the rapid intervention and infectious disease control. WBE is the most effective and cheap near real-time tool available to communities.
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A thorough look at the EPA’s perchlorate final action
99.3% pure potassium perchlorate containing a small amount of cabosil to minimize clumping and keep the mixture free-flowing. This is typical of fireworks; courtesy of https://fireworkscookbook.com/
The EPA recently declined to regulate perchlorate under the Safe Drinking Water Act (SDWA) and promulgated this press release. The Federal Register Final Action Notice is here (RIN:2040-AF28). In general, this decision has been heavily criticized; for instance, a New York Times’ headline read “E.P.A. Won’t Regulate Toxic Compound Linked to Fetal Brain Damage.” The ranking Senate Environment and Public Works Committee member, Senator Tom Carper (D-DE) even said “ [the] EPA has abdicated its responsibility to set federal drinking water standards for a chemical long known to be unsafe, instead leaving it up to states to decide whether or not to protect people from it.” It begs the question why would an agency charged to protect human and environmental health decline to regulate a known hazard? Perhaps more surprisingly, the nation’s water safety and utility advocate, the American Water Works Association (AWWA) agreed with the EPA’s ruling. This article will examine what perchlorate is, what it means to be regulated under the SDWA, perchlorate’s regulatory history, and what the EPA, as well as advocates and critics had to say about the recent ruling. As this is slightly longer than a typical article each section is meant to be relatively self-contained.
What is Perchlorate?
Perchlorates are chemical compounds containing ClO4–. The most common commercial perchlorates are ammonium perchlorate (NH4ClO4), perchloric acid (HClO4), potassium perchlorate (KClO4), sodium perchlorate (NaClO4), and lithium perchlorate (LiClO4). The perchlorate anion may also be bound to other alkali or alkaline earth metals. Perchloric Acid (HClO4) is stronger than sulfuric and nitric acids and is the most common precursor for other perchlorates. Perchlorates can form naturally in the atmosphere leading to trace amounts in precipitation; especially in west Texas, New Mexico, and Northern Chile in the Atacama Desert. Perchlorate is often used as solid-state rocket fuel and is also used in fireworks, flares, gunpowder, and explosives. Surprisingly, given its highly reactive nature, perchlorate can persist in the environment for years. By far the most manufactured perchlorate is ammonium perchlorate for its use in aerospace and defense; it is manufactured more by mass than all other perchlorates combined.
Perchlorate’s uses
The space shuttle’s booster rocket was about 70% ammonium perchlorate and the rest was powdered aluminum or elastomeric binders. Ammonium perchlorate was also responsible for the PEPCON disaster on 4 May 1988 which caused 2 fatalities, 372 injuries, and about $100 million 1988 dollars damage ($218 million in 2020 dollars). The disaster’s damage radius was approximately 10 miles (16 km) and equivalent to about one TNT kiloton or the same yield as a small tactical nuclear weapon. The blast was caught on video by Dennis Todd and has been used in many TV shows. It can be viewed here.
Perchlorates’ use in rocket fuel extends to military applications. Most submarine launched intercontinental ballistic missiles use ammonium perchlorate boosters; because of this many countries, including the US, consider exact perchlorate production, import, and export figures confidential or a state secret. However in 2008, the Department of Defense did publish an estimated use between 6 and 8 million perchlorate pounds annually.
Perchlorate is also used in temporary adhesives, electrolysis baths, batteries, air bag ignitors, matches, desiccants (drying agents), etching agents, electropolishing, ion-exchange chromatography, oxygen candles (used on submarines and in spacecraft), cleaning agents, and oxygen generating systems. Much like the rat poison Warfarin, perchlorates are sometimes used in medical applications. Perchlorate is used to treat overactive thyroids and to counter the drug amiodarone’s side effects. Additionally, perchlorate is used to block radioactive technetium uptake during medical imaging of the brain, blood, and placenta.
Perchlorate in Agriculture
Chilean nitrate fertilizer contained high natural perchlorate levels (0.12-0.26% by weight) and perchlorate is found where this was used; especially on Long Island, New York. Studies have also uncovered perchlorates in synthetic fertilizers in concentrations from 1,800 μg/g to 4,200 μg/g. Likewise, perchlorates have been used in weed killers and leguminous plant growth promoters. Perchlorates have also been used to increase poultry and other farm animal’s weights although there is no evidence perchlorates increase human weight.
Perchlorate, Mars, and Space Travel
Magnesium perchlorate (Mg(ClO4)2) is manufactured in smaller amounts than other perchlorates however, it has been found on Mars in large quantities (>0.6% by weight in soil). Magnesium perchlorate forms the basis for several theories that liquid water can be found on Mars at or below the surface because it has a high solubility (99.3 g/100 mL) and freezing point depression/boiling point elevation falls into colligative properties. A colligative property depends on the quantity of solutes in a solvent rather than the solute’s specific chemical nature. Magnesium perchlorate’s presence on Mars has also led to theories that Mars could be a natural rocket refueling station. Unfortunately, 0.6% by weight in soil is equivalent to 6×106 ppb and would be exceedingly toxic to human settlement.
Where is perchlorate found?
Perchlorates were identified in about 5% of community water systems in the US based on 1997 and 1998 American Water Works Association led studies performed on the EPA’s behalf. A community water system is a water system that serves at least 25 people or 15 service connections; there are about 52,110 community water systems in the United States as of 7 April 2014 according to the CDC. The studies were performed before Standard Method 314.0 was adopted by the EPA and indicated a need for analytical refinements. The Environmental Working Group, a nonprofit environmental activist group that is often labeled as alarmist, suggests that perchlorate was detected in 375 water utilities serving 12.1 million Americans in its Tap Water Database. During EPA mandated tests in 2001 and 2003 under the 1st Unregulated Contaminant Monitoring Rule (UCMR1) perchlorate was found in drinking water systems serving 16.6 million Americans.
As perchlorate is highly soluble, relatively stable, and highly mobile in water and has a low vapor pressure, perchlorates do not volatilize from water or soil to air, leach readily into groundwater, and travel large distances from initial contamination. Perchlorate is only weakly absorbed so its movement through soil is generally un-retarded. These two properties indicate that perchlorate travels rapidly and far in water. For instance, the Olin Flare Facility in Morgan Hill California created a plum which stretched more than 10 miles (16 km). You can read more about the Olin Flare Facility here.
In addition to the UCMR1 studies, Arizona, California, and Texas each completed their own state-based studies summarized in the table below. Texas’ study is particularly interesting because no credible anthropogenic perchlorate source could explain the contamination’s scale or level leading Texas Tech researchers to propose natural contamination.
State based supplements to UCMR1 summay
The AWWA, EPA, and ATSDR (Agency for Toxic Substances and Disease Registry) all agree that perchlorate is not widely dispersed to the environment by rocket combustion. When it is used as a fuel perchlorate is destroyed in the combustion process. Most environmental releases come from anthropogenic releases (manufacturing accidents), fireworks, fertilizer application, and natural formation.
Perchlorate has been detected in most states, the District of Columbia, Puerto Rico, and the Mariana Islands. A contamination map from this 2010 Government Accountability Office (GAO) report is given below.
Perchlorate contamination map from this 2010 GAO report
Surprisingly, potassium perchlorate is also an FDA approved additive in food container rubber gaskets, not to exceed 1% under 21 CFR 177.1210(b)(5). There are perchlorate contamination indications in food. Leafy plants such as tobacco and lettuce and highly vascular plants such as tomatoes have been shown to uptake perchlorate in significant concentrations (upto 164.6 mg/kg dry weight in green flue-cured tobacco). Perchlorates are also found in household bleach that is stored for long times.
Perchlorates health effects
Perchlorates mainly exhibit thyroid toxicity in humans. Perchlorates also partially inhibit thyroidal iodine uptake leading to one medical application for them. Perchlorates are conjectured to lead to hypothyroidism and goiter although this remains unproven. While unproven, perchlorates were used to treat hyperthyroidism for many years leading credence to the suspicion. Side effects from perchlorate treatment included skin rashes, nausea, and vomiting. Some patients developed severe red-blood cell shortages leading to death (fatal aplastic anemia). It is speculated that perchlorate effect depends on gender, exposure length, and dietary iodine consumption.
Perchlorate hurts the thyroid by inhibiting iodine’s transport into thyroid follicle cells by competitive binding to sodium/iodine symporter which catalyzes Na+ and I–‘s transfer. Perchlorate’s inhibition limits iodine levels needed to produce thyroxine (T4) and triiodothyronine (T3). Perchlorate is considered an endocrine disrupting compound because it effects T4 and T3. While perchlorate’s effects are reversible, development problems caused by inadequate circulating hormones are not; leading to conjectured child brain developmental effects and the New York Times’ headline at this article’s start.
Perchlorate was shown to significantly increase systolic blood pressure (the top number in blood pressure readings) which is the maximal arterial pressure when the heart beats. Differences in systolic and diastolic (the bottom number in blood pressure readings or the arterial pressure between beats) are known as pulse pressures. A normal pulse pressure is about 40 mm Hg or less; pulse pressures 60 or greater are considered risk factors for cardiovascular disease, stroke, and heart attacks.
There is some indication that perchlorate may have pulmonary toxicity such as inflammatory infiltrates, alveolar collapse, subpleural thickening, and lymphocyte proliferation.
Perchlorate’s Carcinogenicity
Perchlorates are not considered to be carcinogens by the Department of Health and Human Services or the International Agency for Research on Cancer. It is also conjectured that perchlorate may cause changes in children’s brain development.
The Safe Drinking Water Act (SDWA)
The SDWA, Public Health Services Act Title XIV, is the major federal law protecting drinking water and was first enacted in 1974 with major revisions in 1986 and 1996. The original 1974 act established a system where states, once vetted, are responsible for the SDWA’s implementation and enforcement; this is known as primacy. Primacy may also be granted to Indian Tribes, Territories, and the District of Columbia. In cases where primacy has not been granted to a state, tribe, territory, or district the EPA retains primacy. The EPA has primacy in every Indian tribe except the Navajo Nation, in Wyoming, and the District of Columbia. In every case where primacy was requested it has been granted. To request primacy local regulations at least as stringent as national requirements must be adopted, adequate enforcement procedures must be developed (including monitoring and inspections), and administrative penalty authority must be adopted. Primacy agencies must also conduct water system inventories, maintain records and compliance data, and make reports as EPA may require as well as developing safe water provision emergency plans. Although the SDWA is the major federal law, other laws including the Clean Water Act and various Water Infrastructure Improvement Acts also modify drinking water protection. The SDWA applies to the approximately 152,700 American water systems which supply water to at least 25 people or 15 service connections.
Monitoring Requirements under the SDWA
Primacy agencies may follow the Standardized Monitoring Framework (SMF) or the Alternative Monitoring Guidelines. The SMF was meant to simplify, standardize, and consolidate drinking water monitoring requirements. The SMF was established 30 January 1991 and included 9-year fixed compliance cycles each subset into three periods. The Alternative Monitoring Guidelines allow primacy agencies to grant utilities: monitoring waivers, surrogate sampling and reduced nitrate monitoring.
Under the SMF community water systems serving >10,000 would collect 4 quarterly perchlorate samples during the second compliance period of the fourth compliance cycle (January 1, 2023 through December 31, 2025). Community water systems serving 10,000 or fewer people and non-transient noncommunity water systems would collect 4 quarterly samples during the third compliance period of the fourth compliance cycle (January 1, 2026 through December 31, 2028). The EPA estimated that 60% of surface water systems and 10% of groundwater systems would be ineligible for waivers to reduce monitoring requirements.
SDWA Amendments
The first major SDWA amendments in 1986 were mainly designed to speed the EPA’s contaminant regulation and groundwater protection. The 1986 amendments were extremely ambitious and attempted to make up for lost time since the original act. The 1996 amendments recognized the 1986 amendments were too aspirational and slowed down the required contaminant regulation pace as well as overhauling the entire regulation process. The 1996 amendments gave us the current risk-based regulatory approach used today. Additionally, the 1996 amendments created state-based operator certification programs.
Chemical Regulation under the SDWA
The 1996 SDWA amendments established three requirements for a chemical to be regulated under the Safe Drinking Water Act (SDWA):
The substance must have an adverse health effect
It must occur or have a substantial likelihood to occur at adverse public health frequencies and levels
The EPA’s Administrator must judge regulation to present a meaningful opportunity for health risk reduction
Once the EPA Administrator determines to regulate a contaminant the EPA must propose a rule within 24 months and promulgate a National Primary Drinking Water Regulation (NPDWR) within 18 months after proposal. New regulations generally become effective three years after promulgation and up to two additional years may be provided if capital improvements are needed. Systems serving 3,300 or fewer people may be given an additional 9 years beyond the compliance deadline. The EPA must review and strengthen as appropriate each drinking water regulation every six years. When developing regulations, EPA is required to use the best available, peer reviewed science, supporting studies and data as well as make publicly available a risk assessment document that discusses estimated risks, uncertainties, and studies used in the assessment.
The Unregulated Contaminant Monitoring Rule (UCMR)
The 1996 SDWA amendments also created the Unregulated Contaminant Monitoring Rules. Every 5 years the EPA must publish an unregulated contaminant candidate list (CCL) for chemicals which are known or anticipated to both occur and cause deleterious health effects in public water systems. Additionally, every 5 years the EPA must publish a 30 contaminant or less list that requires a monitoring program by public water systems known as the Unregulated Contaminant Monitoring Rule (UCMR). CCLs and UCMRs are required on a quinquennium basis and are given sequential numbers to refer to the different lists; for example the Third Unregulated Contaminant Monitoring Rule (UCMR3) was published on 2 May 2012 and UCMR4 was published on 20 December 2016. Every 5 years, the EPA is required to make a regulator determination (whether to regulate) for at least 5 of the 30 chemicals under the CCL. Generally, UCMR monitoring is from all public water systems serving more than 10,000 people and 800 representative public water systems serving 10,000 or fewer people. Perchlorate was the first drinking water contaminant that EPA has proposed to regulate in nearly 24 years under the provisions of the Safe Drinking Water Act Amendments of 1996.
Maximum Contaminant Levels (MCL) and a Maximum Contaminant Level Goals (MCLG)
A maximum contaminant level (MCL) is a legally enforceable regulation under the Safe Drinking Water Act. A maximum contaminant level goal (MCLG) is an aspirational non-enforceable public health objective rather than a regulatory standard. For non-carcinogens the MCLG is based on the reference dose. The reference dose essentially is a conservative estimate of the daily allowable contaminant consumption a person can have without an expected adverse health effect during a typical lifetime. As the US adheres to a linear no threshold radiation policy, the MCLG for carcinogens is always zero. MCLs and MCLGs often coincide however, they do not always. Since MCLs are legally enforceable they may not match MCLGs because of difficulties in contaminant measurement, lacking treatment technologies, or treatment cost outweighing public health benefits. MCLs must be set as close as “feasible” using best available technology, treatment techniques, or other means (considering costs) to the MCLG. The EPA may ignore the feasible level if the feasible level could lead to an increase in health risk by increasing other contaminant’s concentration or interfering with treatment processes used to comply with other SDWA requirements. In such cases the overall health risk must be minimized.
For contaminants the EPA wants to regulate but there is no economical or technically viable threshold (MCL), the EPA creates “treatment technique rules” such as the Lead and Copper Rule which are enforceable procedures to minimize risk.
SDWA Cost Benefit Analysis
Criteria three for regulating a contaminant under the SDWA in the 1996 amendments, the EPA Administrator’s judgement to present meaningful health risk reduction, comes with it a required cost-benefit analysis. EPA must publish a “health risk reduction and cost analysis.” For each drinking water standard and each alternative standard being considered, EPA must publish and take comments on quantifiable and nonquantifiable health risk reduction benefits and costs. EPA may promulgate an interim standard without first preparing a health risk reduction and cost analysis or determination whether a regulation’s benefits justify the costs if the Administrator believes that a contaminant presents an urgent public health threat.
If the EPA Administrator determines that the benefits do not justify the costs, the EPA may promulgate a standard that maximizes health risk reduction benefit at a justifiable cost provided by the benefits. The EPA generally has set standards based on technologies affordable for large communities however, P.L. 104-182 requires the EPA to list any technologies or procedures that are affordable for small public water systems serving populations of 10,000 or fewer. If EPA does not identify “compliance” technologies that are affordable for small systems, then the agency must identify small system “variance” technologies or other means that may not achieve the MCL but are protective of public health. The SDWA allows for variances and exceptions based on costs.
Perchlorate Regulation
As of 11 August 2020, drinking water perchlorate is regulated in Arizona, California, Massachusetts, New Jersey, New York, and Texas. In addition, Illinois, Maryland, Nevada, New Mexico, and Wisconsin have advisory levels. The Government Accountability Office states that 10 states have established advisory or health-based perchlorate goals. Perchlorates can be classified as a D001 Resource Conservation and Recovery Act (RCRA) hazardous wastes under 40 CFR 261.23 based on perchlorate’s reactivity characteristic depending on specific circumstances. The EPA has also established a 55 mg/kg residential soil screening level (SSL) and a 720 industrial SSL under Superfund. The Department of Transportation regulates perchlorates under its 49 CFR 172.101 hazardous material table. Various states also list perchlorate as a hazardous substance such as Rhode Island and Pennsylvania.
Perchlorate’s Regulatory history
In 1995, the EPA established a provisional 4 – 18 ppb provisional reference dose range.
In 1997, the EPA first discovered perchlorate contamination in Nevada. At that time, 1,000 pounds (454 kg) per day of perchlorate entered Lake Mead and the Colorado River through contaminated groundwater. Lake Mead provides drinking water to residents of southern Nevada. The contamination originated from the only two perchlorate-manufacturing facilities in the United States at the time.
In August 1997, the Nevada Division of Environmental Protection selected 18 parts per billion (ppb) as the recommended action level for cleanup pending a more current risk assessment. Likewise, California’s Department of Public Health selected 18 ppb action level based on the EPA’s 1995 provisional reference dose range.
In 1998, the EPA published its first draft perchlorate assessment and perchlorate was added to the EPA’s first Contaminant Candidate List (CCL1) indicating that the EPA might be interested in regulating perchlorate. In 1999 perchlorate was included on the EPA’s first Unregulated Contaminant Monitoring Rule (UCMR1). Perchlorate was rolled over into CCL2 in 2005 along with 50 other CCL1 contaminants because the EPA was waiting on monitoring results and health effect studies. Without a regulatory determination perchlorate was rolled into a draft CCL3 in 2008.
In January 2002, the EPA revised its draft assessment with a 1 ppb reference dose (RfD); this assessment was widely criticized although it did cause California to lower its action level to 4 ppb. California selected 4 ppb as that was the 1995 EPA’s lower provisional reference dose range and the lowest level that the era’s analytical methods could detect. After a second peer review which was also not well received by the scientific community, The Department of Defense, The National Aeronautics and Space Administration, The Department of Energy, and the EPA asked the National Academy of Sciences to provide an assessment which it rendered in January 2005 recommending a 0.0007 mg/(kg * day) RfD.
In 2001, perchlorate was detected in Massachusetts’ Military Reservation’s (MMR) groundwater at 600 ppb. The site was investigated from the 1980s when groundwater contamination was first discovered. In 1996 in response to the contamination discovered in Cape Cod’s Aquifer the first of four EPA SDWA administrative orders was issued forcing the Impact Area Ground Water Study Program’s creation. Cape Cod’s aquifer has 6 lenses: Sagamore, Monomoy, Nauset, Chequesset, Pamet, and Pilgram. MMR is situated directly on top of Cape Cod’s aquifer’s most productive part: the Sagamore Lens. About 450 million gallons per day (MGD) flow through Cape Cod’s aquifer with nearly 60% of water flux due to the Sagamore Lens. The Sagamore Lens is the only drinking water source for Cape Cod’s 200,000 year-round and 500,000 seasonal residents. In 1997 the second administrative order was issued; this order mandated that the Army stop all training at MMR. I cannot understate how far reaching this was for the Army. In the “pre-war era” then the Army existed primarily to train. Stopping that main function was akin to ordering Coca-Cola to stop producing soft drinks. That order was the primary driving force behind the Department of Defense’s extensive perchlorate response. The Bourne Water District Officially requested state guidance in March 2002. Massachusetts officially recommended that Bourne should set a 1 ppb limit based on the EPA draft assessment. In 2003, the Massachusetts Department of Environmental Protection established a scientific advisory committee. In February 2004 the committee recommended, and Massachusetts adopted, a 1 ppb advisory level which was below the 4 ppb detection limit available at the time.
In 2003, a federal court in California found that Superfund applied because perchlorate is ignitable and a characteristic hazardous waste. California’s legislature enacted AB 826, the Perchlorate Contamination Prevention Act of 2003, requiring California’s Department of Toxic Substances Control (DTSC) to adopt regulations specifying best management practices for perchlorate and perchlorate-containing substances.
In March 2004, the California EPA Office of Environmental Health Hazard Assessment (OEHHA) set a 6 ppb Public Health Goal (PHG). A PHG is the contaminant level in drinking water that does not pose a significant risk to health. Unlike EPA’s Drinking Water Equivalent Level, OEHHA’s PHG level accounts for exposures to a contaminant from sources besides drinking water. It was not a regulatory requirement. Interestingly, the EPA and the University of California peer reviewed this document even though the EPA had initially suggested a lower reference dose from only water sources.
On 18 February 2005 the EPA set a 0.0007 mg/(kg * day) reference dose (RfD) for perchlorate consistent with the January 2005 National Academy of Sciences report. A (RfD) is a scientific estimate of a daily exposure level that is not expected to cause adverse health effects in humans with a 10 fold conservative uncertainty factor (meaning the level expected to not cause adverse health effects in health humans (No Observed Effect Level – NOEL) is actually 0.007 mg/(kg * day); the 10 fold uncertainty is to cover scientific error such as variability across life-stages, individuals, or genders and protect sensitive sub-groups such as fetuses). EPA’s RfD translated to a 24.5 ppb Drinking Water Equivalent Level (DWEL). In dilute water a part per billion is equivalent to a microgram per liter μg/L. A Drinking Water Equivalent Level, which assumes that all contamination comes from drinking water and is the contaminant concentration an average citizen will have no adverse effect with a margin of safety. Exposures above the DWEL are not necessarily considered unsafe because of the built-in safety margin. EPA’s Superfund cleanup program issued 24.5 ppb cleanup guidance based on the RfD.
In July 2006 Massachusetts became the first state to adopt a regulatory standard when it promulgated a 2 ppb perchlorate state drinking water standard. To arrive at a drinking water standard, the department considered information on the availability and feasibility of testing and treatment technologies, as well as data that demonstrated that perchlorate can enter drinking water as a by-product of hypochlorite (bleach) solutions used as disinfectants. The department chose to set the standard at a level that did not create disincentives for public water systems to disinfect their water supplies. The department determined that a maximum contaminant level of 2 parts per billion would provide the best overall protection of public health, considering the benefits of disinfection, while retaining a margin of safety to account for uncertainties in the available data.
In October 2007, California promulgated a 6 ppb regulatory standard. By law, the California Department of Public Health is required to set a drinking water standard as close to the public health goal as is economically and technologically feasible. California found that large water systems could meet the standard with $18 per customer annual costs while annual costs for smaller systems ranged from $300 to $1,580. The Department of Public Health proposed economic based variances for systems serving less than 10,000 customers if the estimated annual treatment cost per household exceeds 1% of the median household income in the community served.
On 10 October 2008, under President George W. Bush and EPA Administrator Marcus Peacock, the EPA published a preliminary determination not to regulate perchlorate. Administrator Peacock found that there was no meaningful opportunity for health risk reduction.
In April 2010 the EPA’s Office of the Inspector General released a report critiquing the risk assessment process and procedures used by the EPA to develop and derive the perchlorate RfD.
On 11 February 2011, under President Barrack Obama and EPA Administrator Lisa Jackson, the EPA reversed this decision and decided to regulate perchlorate however, it provided no specific regulatory proposals. This decision caused me personally much consternation as I was writing my bachelor’s thesis on modeling perchlorate in groundwater using the Complex Variable Boundary Element Method and forced me to re-write several sections just before it was due!
In September 2012 the US Chamber of Commerce submitted a request for correction under the Information Quality Act regarding the regulatory decision. The EPA formed a Scientific Advisory Board that recommended many changes to the data under the decision. The Scientific Advisory Board recommended that the EPA abandon the standard RfD based MCL approach in favor of physiologically based pharmacokinetic/pharmacodynamic modeling based on mode of action. The EPA accepted and followed this advice.
On 18 February 2016, the National Defense Resource Council (NDRC), filed a complaint against the EPA essentially saying the EPA was failing in its mandate because the EPA had not yet proposed a perchlorate limit. The NDRC is a non-profit environmental advocacy group which started as a Scenic Hudson Preservation Conference outgrowth; oddly enough this group was created to block Consolidated Edison plans for a powerplant on Storm King Mountain right by West Point, New York.
On 18 October 2016 the NDRC and EPA reached consent degree in which the EPA did not admit to failing to comply with statutory obligations. The EPA entered the consent decree to prevent judicial interference with the remedial plan that it preferred. The EPA also expressly reserved all discretion under the SDWA and general administrative law principles. Basically, the NDRC simply wanted the EPA to hurry up and propose specific limits. Its important to note that the EPA could NOT have promised the NDRC any specific regulatory changes because that would violate the Administrative Procedures Act (APA). Agencies may agree to consider rule-making changes and to adopt regulations required by law, but they generally will not make substantive commitments concerning the content of regulations that are subject to APA requirements. The consent decree required the EPA to issue national drinking water regulation for perchlorate by 19 December 2019. The EPA asked, and the NDRC agreed, to extend the deadline until 19 June 2020.
On 23 May 2020 EPA Administrator Andrew R. Wheeler signed a proposed rule issued on 26 June 2019 setting a maximum contaminant level (MCL) coincidental with a maximum contaminant level goal (MCLG) of 56 micrograms per liter (μg/L). Alternatives included in the proposal were 18 μg/L or 90 μg/L MCLs coinciding with MCLGs, establishing an MCLG of 18, 56, or 90 with a National Drinking Water Standard, and withdrawing its 2011 decision to regulate perchlorate.
On 18 June 2020, after the public comment period, the EPA issued a press release about the final action declining to regulate perchlorate under the Safe Drinking Water Act. The NDRC was given until 9 July 2020 to challenge the scientific footing the EPA used; which it did. On 21 July 2020, the EPA published this final action. It is likely that the NDRC will sue the EPA to try and force a different outcome.
The EPA’s Stated Opinion
On 18 June 2020, the EPA issued a press release about the final action declining to regulate perchlorate under the Safe Drinking Water Act. On 21 July 2020, the EPA published this final action. EPA Administrator Andrew Wheeler said “State and local water systems are effectively and efficiently managing levels of perchlorate. Our state partners deserve credit for their leadership on protecting public health in their communities, not unnecessary federal intervention.” The EPA cited three main criteria for declining to regulate perchlorate:
Californian and Massachusetts’ state level regulation of perchlorate (these two states constituted about 60% of what would have been exceedances in the new rule; the exceedances were based on the old UCMR1 monitoring campaign updated with current conditions from Massachusetts and California)
Current remediation efforts to address perchlorate contamination especially in Nevada contaminating the Colorado River and Lake Meade as well as overall decreasing perchlorate levels
Improved storage and handling procedures for drinking water disinfectants
Oddly enough, in the actual final regulatory action the third criteria cited was not mentioned. Improved bleach storage and handling only appeared in the press release.
The EPA’s analysis found that nationwide perchlorate regulation costs would significantly outweigh benefits and decided to focus its limited resources on more immediate and significant public health concerns. The EPA also cited historical precedent. By the EPA’s analysis the pesticide Aldrin (a DDT component) would have affected more water systems than perchlorate does, and the EPA declined to regulate Aldrin in 2003. The EPA also estimated that implementing a perchlorate regulation would cost $9.5-18M while the benefits only ranged from $0.3-3.7M. The EPA argued that perchlorate’s infrequent occurrence at concerning levels imposes high monitoring and administrative cost burdens on states and public water systems without rendering net tangible benefits.
The EPA wrote: “It is of paramount importance that water systems (particularly medium, small, and economically distressed systems) focus their limited resources on actions that ensure compliance with existing NPDWRs and maintain their technical, managerial, and financial capacity to improve system operations and the quality of water being provided to their customers, rather than spending resources monitoring for contaminants that are unlikely to occur.” While the EPA finds perchlorate dangerous above certain exposure levels however it doesn’t occur often enough to warrant the regulatory program costs.
Key Stakeholder Comments
The AWWA
On 2 July 2007 the AWWA, building on earlier letters from 2 February 2005 and 27 May 2005, recommended the EPA to regulate perchlorate. The AWWA stated that “National compliance costs for a perchlorate MCL ranging from 2 to 24 [ppb] is smaller than estimated compliance costs for other drinking water regulations.”
In the response period to the request for comment on the final action the AWWA submitted a comment supporting no regulation for perchlorate. Absent withdrawal, the AWWA requested that the EPA adjust monitoring requirements due to the significant burden the current requirements would impose on utilities and primacy agencies. The AWWA pointed out that the 2011 consent decree did not require the EPA to regulate perchlorate only to propose a regulation for perchlorate. The AWWA said the “EPA would be acting in an arbitrary and capricious manner if it finalized a perchlorate regulation because the costs of all three of the proposed MCLGs exceed the benefits.” Michigan v. EPA was cited as an example where the Supreme Court overturned a rule where “EPA refused to consider whether the costs of its decision outweighed the benefits.” The AWWA suggested that there were significant technical flaws in the proposed MCLGs and stated that the new pharmacokinetic/pharmacodynamic modeling the EPA used was a flawed method and criticized its transparency as well as a sensitivity analysis’ lack. As an example, the AWWA cited that the epidemiological data used by the EPA was drawn entirely from non-U.S. populations. However, the AWWA charges that the measured variability between individuals and subpopulations is larger than the small perturbations in fT4 and clinical effects considered in the EPA analysis. If the EPA had decided to regulate perchlorate the AWWA requested that the EPA transition utilities to a 9-year monitoring cycle after a year below the MCL.
The NDRC
The NDRC naturally was displeased with the ruling. The NDRC falsely asserts that the EPA was required to regulate perchlorate under the 2016 consent decree.
The American Academy of Pediatrics
The American Academy of Pediatrics (AAP), a non-profit 67,000 member professional organization for primary care pediatricians, pediatric medical subspecialists, and pediatric surgical specialists dedicated to the health, safety, and well-being of infants, children, adolescents, and young adults requested a lower NDWPR than currently exists. The AAP cited that Children born with even mild, subclinical deficiencies in thyroid function may have lower IQs, higher chances of being diagnosed with attention deficit/hyperactivity disorder (ADHD), and visuospatial difficulties. The AAP ended their comment saying:
[we are] particularly concerned that EPA is considering withdrawing its 2011 determination to regulate perchlorate, relinquishing national oversight over a chemical with well-established health risks in drinking water. This would set a precedent inconsistent with EPA’s stated mission to protect public health. AAP urges the EPA to set a stronger MCLG [maximum contaminant level goal] for perchlorate that is based on all available evidence of potential harms to protect public health. A lower MCLG will allow EPA to generate reporting data that more accurately portrays the populations at risk and to better protect vulnerable populations
California, Massachusetts, New York, and New Jersey, states which all set lower state-based limits on perchlorate, were highly critical of the EPA’s methods and also noted that the traditional EPA risk methods would have set an 8 ppb limit.
The Salt River Pima-Maricopa Indian Community from Arizona stated:
Withdrawal of regulation will only encourage the industry to abandon any preventative measures to contain current contamination
The whole debate seems to center on cost-benefit analysis. Something ignored in all the cost-benefit analysis I’ve seen so far is the tendency for compliance costs to come down overtime with monitoring method development, investment, new treatment technologies, and research. It is unlikely however that costs will significantly drop absent that demand driven development. My time at Camp Edwards as a cadet showed me fireworks platforms can create dangerous plumes in small towns from seemingly innocuous widespread traditions. Massachusetts did not attribute the fireworks plume because that would force the county or state to pay the cleanup costs for that plume instead of the Department of Defense. There are probably many smaller water systems without awareness. The 2010 GAO report states that the EPA does not have a perchlorate tracking system and that perchlorate’s nationwide extent is unknown. It seems likely that larger water systems will be less likely to be contaminated and more cheaply treat perchlorate. The overall background perchlorate concentration falling is mainly due to regulation, as the EPA states particularly in California, Massachusetts, and Nevada. The FDA should also be leaned on to develop more robust perchlorate consumption numbers and most likely remove perchlorate from food contact surfaces. Any perchlorate threshold the EPA sets should incorporate total cumulative dose. With all this in mind however, US water systems are already poor and don’t even spend enough to replace or maintain infrastructure. Overall, I like the Californian approach where a relatively strict criteria was set with easy waiver procedures. Since that was not set the health advisory needs to be updated.
Conclusion
Perchlorate can be included on future CCLs; it most likely should be as well. Without the regulatory spotlight perchlorate is unlikely to gather more evidence for or against regulation. To date no new chemical regulations have been passed since the 1996 SDWA amendments (although the EPA proposed PFAS regulation in March 2020). This may be indicative that the regulatory process is not working although it is positive that the EPA does not waste precious resources regulating trivial contaminants (there are 13 SDWA chemicals which have had zero violations – these were mandated by the 1986 SDWA amendments and should probably be de-listed).
