Earlier this year, the US Environmental Protection Agency proposed maximum permissible levels of six PFAS (per- and polyfluoroalkyl compounds) – so-called everlasting chemicals – in drinking water.
However, the proposed guidelines do not account for half of the PFAS found at contaminated sites across the country.
The findings were published in the journal Environmental Science & Technology by a team led by the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS).
PFAS are found in a variety of products, including fire retardant foams, and have been accumulating in the environment since they were initially created by Dupont in the 1930s and commercially manufactured by 3M beginning in the 1950s.
Some PFAS have been associated to a variety of health hazards, including cancer, immunological suppression, diabetes, and low newborn birth weight.
There are two types of PFAS compounds: precursors and terminals. The majority of the PFAS chemicals being monitored are terminal compounds.
The EPA’s draft drinking water guidelines apply to six terminal chemicals that do not degrade in natural environments. Precursor chemicals can be converted into terminal forms via biological or environmental mechanisms.
There are several precursor substances, the vast majority of which are not routinely monitored and are not currently regulated.The United States military is the world’s largest consumer of PFAS-containing fire-retardant foams known as AFFF (aqueous film forming foam).
For decades, hundreds of military bases in the United States and around the world used AFFF with high quantities of PFAS for fire training drills and firefighting. The use of AFFF is one of the leading causes of PFAS contamination in drinking water.
“Many of the PFAS precursors found in AFFF are difficult to quantify.” “Our findings show that they are gradually transforming into PFAS of concern at AFFF-contaminated sites and contributing to downstream contamination,” said Elsie Sunderland, Fred Kavli Professor of Environmental Chemistry and Professor of Earth and Planetary Sciences at SEAS and senior author on the new paper.
The researchers projected using a computer model and field data that, without remediation, widespread PFAS contamination of drinking water supplies near military facilities is likely to persist for centuries
Many of the PFAS at military sites are precursors that are not detected by normal analytical procedures. The Harvard researchers analyzed the expected lifetime and contribution of those precursors to groundwater contamination using a technology developed earlier in the Sunderland lab that catches all precursors in AFFF.
The study discovered that contamination of two newly controlled PFAS compounds (perfluorohexane sulfonate: PFHxS and perfluorobutane sulfonate: PFBS) at one military facility on Cape Cod, Massachusetts, is maintained via microbial precursor biotransformation in the soil.
These precursors are maintained in the soil and leak into groundwater in terminal form at concentrations hundreds of times higher than the EPA’s acceptable levels.
Using a computer model and field data, the researchers predicted that without remediation, extensive PFAS contamination of drinking water sources around military bases will likely last for generations.
Despite the contamination of nearby aquifers, which may already pose a risk to human health, the majority of PFAS are still present in the soils surrounding these contaminated sites, highlighting the critical need for advances in remediation technology that are effective at cleaning up both terminal and precursor compounds.
Because rules only apply to terminal compounds, the efficacy of current remediation strategies in cleaning up precursors is unknown.
The researchers determined that higher PFAS exposures downstream of over 300 US military locations that employed fire-fighting foams could last for generations.
“The role of PFAS precursors in maintaining hazardous levels of contamination at Joint Base Cape Cod raises concerns about whether exposure risks are being understated near hundreds of other sites where they are not measured,” said Bridger Ruyle, the study’s first author and a former doctoral student in Sunderland’s Lab.
The public comment period for the Environmental Protection Agency’s draft PFAS drinking water regulation ends on May 30. While this is a step in the right direction, Sunderland points out that there are thousands of PFAS chemical structures, many hundred of which have already been found in the environment.
Sunderland’s research has also proven that the amount of military fire training grounds inside a watershed is an excellent predictor of PFAS contamination in a community’s drinking water supply in related study published today in Environmental Science & Technology.
However, certain groups are more vulnerable than others; a forthcoming study from the Sunderland lab demonstrates significant sociodemographic variations in PFAS exposure and closeness to PFAS sources across the country.
Source: Harvard University
