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Episode released on February 20, 2025
Episode recorded on October 23, 2024
Joe Cotruvo is President of Joseph Cotruvo & Associates where he provides advice to the World Health Organization's Guidelines for drinking water quality and numerous oversight panels on drinking water quality issues, among many topics. He was the first Director of EPA's Drinking Water Standards Division after passage of the Safe Drinking Water Act and Director of the Risk Assessment Division in the Chemical Toxics Program.
Highlights | Transcript
PFAS: Per- and polyfluoroalkyl substances. There are hundreds of commercial chemicals with many disposed in rivers or groundwater.
Carbon hydrogen bond in the chemical converted into a carbon fluorine bond.
Carbon-fluorine bonds, very stable, “forever chemicals”, persistent but not genotoxic.
A detailed review of PFAS compounds is provided by Wee and Aris, Nature/Clean Water, 2023.
Half life in blood for PFOA, 2 – 10 yr; PFOS: 3 – 27 yr.
Lower chain compounds, C4 rather than C8, half life in blood ~ 1 month, less toxic.
Effective dose for PFAS compounds: much greater than what the concentration in the food or the water indicates, because it bioaccumulates in the blood. It could result in kidney toxicity.
PFOA: perfluorooctanoic acid (Fig. 1). They are like super detergents. The carbon fluorine end of the molecule is hydrophobic; therefore, it repels water. Acids are ionic and dissolve. Chemical on one end is very polar and capable of dissolving in water, on the other end is very nonpolar and very good at picking up oils and dirts, e.t.c.
PFOS: perfluoro octane sulfonic acid. Related to sulfuric acid. Strong acid.
It is water repellent (Gortex), used in nonstick cookware (e.g., Teflon), Scotchgard, and firefighting foams (Fig. 2).
PFAS compounds have been produced since 1940s and 1950s.
Only relatively recently concerned about environmental impacts.
Sources of PFAS:
- Indoor air and dust
- Furniture and carpet and clothes sprays
- Fish (esp freshwater) & shellfish
- Food packaging
- Dairy, eggs, vegetables
- Wastewater discharges and solids
- Soil sediment
- Drinking water
Possible Health Effects:
- Hundreds of high dose animal studies of variable quality
- Human epidemiology studies, some conflicting
- Causality not established, mixed consistency
- Possible thyroid and kidney toxicity
- Slightly increased cholesterol
- Cancer risk?
- Occupational epidemiological studies mostly reported very slight blood pressure effect
- 2018 comprehensive Australian independent advisory committee review concluded that many studies were flawed or biased (Kirk et al., 2018).
Occupational exposure ~ 1000 × general population.
Regulations:
EPA: new regulations April 10 2024 related to PFAS (EPA link).
Maximum Contaminant Level (MCL) under Safe Drinking Water Act (SDWA) is related to the MCL goal.
MCLg: level of a substance in water that would result in no known or anticipated adverse effect on health, with a margin of safety.
MCLg for PFOA and PFOS is zero (Table 1).
MCL is selected to be as close to MCLg as is technically and economically feasible. MCL for PFOS and PFOA: 4 parts per trillion (ppt) and 10 ppt for other regulated PFAS compounds (link).
MCL set at 4 ppt by EPA on April 10, 2024 because that is the minimum reporting level (MRL) based on interlab comparisons. MRL means any concentration below this level does not have to be reported.
Hazard Index (HI): sums concentrations of chemicals and divide by toxicology value for each, if HI exceeds 1 it is a compliance issue.
HI is questionable because there is not necessarily toxicological interaction or additivity with PFAS compounds.
It is difficult to measure PFAS at these low levels because you need to avoid cross contamination, atmospheric deposition, and absorbance onto glassware etc.
PFAS was eliminated from Scotchgard ~ 20 yr ago
Levels of PFAS in the bloodstream now are 90% lower than they were in 2000 (Sonnenberg et al., 2023, Figure 3).
PFAS (C-8) was replaced by perfluorobutane sulfonic acid (PFBS) (C-4) in 3M’s Scotchgard.
PFBS may not be as effective as PFAS but will be more volatile (smaller molecule). It is a substitute for PFAS.
PFAS MCLs in the U.S. are much lower than those in other countries. No international consensus on toxicology of these chemicals.
PFAS MCLs:
Europe 100 ppt (European Chemicals Agency [ECHA], 2021 directive), limits total PFAS in drinking water to 100 ppt.
The recast Drinking Water Directive limits total PFAS in drinking water to 50 ppt and levels of 20 individual PFAS to 10 ppt (12 January, 2021)
WHO: provisional guidance values (pGVs) of 100 ppt individually for PFOA and PFOS, 500 ppt for total PFAS based on 29 PFAS compounds in 2022 (Southerland et al., 2023). These guidelines are currently being reevaluated.
Canada: 30 ppt for total PFAS (~ 25 different substances) (Link).
Australia: national health-based guidance values, HBGV, PFOA, 200 ppt; PFOS, 4 ppt, PFHxS, 30 ppt, PFBS, 1000 ppt, GenX chemicals, no HBGVs. (Link)
EPA lowered Health Advisory Level from 70 ppt (2016) to 4 ppt (2022) (Cotruvo et al., 2023).
Relative Source Contribution of PFAS from drinking water is the proportion of a person's total daily exposure to PFAS that comes from drinking water and was set at 20%, remainder from other sources, inhalation of dust, food etc. RSC means that will not allow DW to contribute more than 20% of total daily exposure, which increases the burden on DW.
If RSC was 80%, then the MCL for PFAS could be 4 times higher, 16 ppt rather than 4 ppt.
Current Status based on Unregulated Contaminant Monitoring Review (UCMR) Results
UCMR 3, 2013 – 2015:
4920 Public Water Supplies: All systems > 10,000 people (`~4120 )
~ 800 25 to 10,000 smaller randomly selected
Minimum Reporting Levels (MRL): PFOA = 20 ppt; PFOS = 40 ppt
Results: PFOA PFOS
Detected 117 95
>70 ppt 13 46
UCMR 5: Jan 2023 – Dec 2025:
- ~ 2000 supplies reported
- 7.8% at least one sample above the MRL (4 ppt; 0.004 ppb.
- Health Advisory : 0.004 ppt
PFOA: 7.8 % > MRL; Average = 0.0095 ppb, max. 0.235 ppb
- 68% groundwater
PFOS: 8.5% > MRL: Average 0.01 ppb, max. 0.095 ppb
PFAS in food: Seafood, fish, greater intakes of PFOA than drinking water except for DW sources near PFAS point contaminated sources where PFAS was manufactured or used extensively (military bases) where groundwater is contaminated.
Food and Drug Administration (FDA): PFAS in the food and the packaging. FDA has determined that PFAS in the diet is not a big concern.
Public Water Systems serving large populations are primarily sourced from surface water where PFAS would flush out rapidly resulting in lower exposure from surface water.
Drinking water regulations are applied universally, require all water systems to monitor for PFAS. This could be expensive.
Wastewater treatment plants: PFAS becomes concentrated in the sludge, sludge is used in agriculture or as a soil treatment or as fertilizer because it is high in nutrients.
PFAS compounds (PFOA and PFOS) designated as a hazardous waste according to Superfund regulations in April 2024 by EPA.
PFAS manufacturers, discharging PFAS as a waste, must meet the Clean Water Act regulations, National Pollution Discharge Elimination System (NPDES) permits.
Public Water Systems, ~50,000 community water systems in the US, they often rely on groundwater and highest PFAS concentrations are found in groundwater.
PFAS found next to military bases (Dept. of Defense) and airports.
Cost Benefit Analysis:
EPA estimated benefits from regulation ~ $1.5 Billion/yr, costs of regulation estimated to be $1.5 B also (EPA Fact Sheet, 2024).
American Water Works Association: estimated costs of PFAS regulation to be 3 – 4 times higher than EPA estimates (AWWA PFAS Costs Fact Sheet).
Public Water Systems have until 2029 to comply with the regulation.
Environmental Working Group develop maps of PFAS distributions in the US (Figs. 4, 5).
PFAS Treatment: PFOS and PFOA are anions (EPA; ITRC).
- Anion exchange
- Reverse osmosis
- Granular activated carbon
Treatment results in a concentrate from treatment, burn it or use high energy process to decompose it. Concentrate would be classified as a hazardous substance.
Other sources of contaminants in drinking water, Safe Drinking Water Act: Arsenic, geogenic, naturally occurring, reduced MCL from 50 to 10 ppm in 2006.
It is difficult for small community water systems to treat water. Decentralized treatment may be more feasible, lower costs. Example from California using activated aluminum, ion exchange process.
High risk issues related to drinking water:
- Legionella: grows in home plumbing. Legionella is the only waterborne disease that kills people. EPA could provide guidance for buildings and homes to manage this issue by adding disinfectant (Cotruvo, 2014).
- Small community water systems, don’t have economies of scale. Decentralized treatment may be more feasible.
- Infrastructure: very old, mineral accumulations and bacterial accumulations.
Joe Cotruvo teaches a course: Drinking Water A to Z, is it safe to drink.
Table 1. Final Primary Drinking Water Regulation (NPDWR) for 6 PFAS (EPA, April 10, 2024).
Compound | Final MCLG | Final MCL (enforceable levels)1 |
| PFOA | Zero | 4.0 ppt |
| PFOS | Zero | 4.0 ppt |
| PFHxS | 10 ppt | 10 ppt |
| PFNA | 10 ppt | 10 ppt |
| HFPO-DA (commonly known as GenX Chemicals) | 10 ppt | 10 ppt |
Mixtures containing two or more of PFHxS, PFNA, HFPO-DA, and PFBS | 1 (unitless) | 1 (unitless) |
Hazard Index | Hazard Index |
