Members of the Sunderland Lab sampling for PFAS contamination on Cape Cod. Credit: Michael Salerno
Key points:
- Researchers say the new draft PFAS rules do not take into account a second form of PFAS compounds that are currently unmonitored.
- The U.S. military is the largest exporter of this PFAS.
- The study shows the PFAS builds up in soil and lasts for centuries.
Earlier this year, the Environmental Protection Agency proposed maximum allowable levels in drinking water for six PFAS—so-called forever chemicals. But now, a study out of Harvard University says the draft standards do not account for half of the PFAS at contaminated sites across the country, namely military bases.
PFAS compounds come in two forms: a precursor form and a terminal form. The EPA’s draft drinking water rules are for six terminal compounds that do not degrade under normal environmental conditions. But, there are many precursor compounds, most of which are not routinely monitored, and none are currently regulated. For example, the U.S. military is the largest global user of fire-retardant foams containing PFAS known as AFFF (aqueous film forming foam), one of the largest sources of PFAS contamination in drinking water.
Much of the PFAS at military sites consists of precursors that are omitted from standard analytical methods. Using a new method that captures all precursors in AFFF, the Harvard team modeled the expected duration and contribution of those precursors to groundwater contamination.
According to the study, published in Environmental Science & Technology, contamination of two of the newly regulated PFAS chemicals—perfluorohexane sulfonate: PFHxS and perfluorbutane sulfonate: PFBS—at one military base on Cape Cod, Massachusetts are sustained by microbial precursor biotransformation in the soil. These precursors are retained in the soil where they leach into groundwater in terminal form at concentrations thousands of times greater than the safe levels established by the EPA.
Using a computer model and field data, the researchers project that, without remediation, widespread PFAS contamination of drinking water supplies near military facilities is likely to persist for centuries. Despite contamination of nearby aquifers that may already pose a risk to human health, the majority of PFAS are still sitting in the soils surrounding these contaminated sites. Since regulations focus only on terminal compounds, the effectiveness of current remediation technologies at cleaning up precursors is unknown.
The public comment period for EPA’s draft PFAS drinking water regulation closes on May 30.