Is PFAS Inhibiting Bioremediation of Chlorinated Compounds? The State of the Science

Trichloroethylene (TCE), a chlorinated solvent, is one of the more common environmental contaminants. Widely used for years as a degreasing agent and as part of cleaning solutions, TCE is classified as a carcinogen and is highly regulated. Fortunately, naturally occurring microbes can degrade it, offering a cost-effective solution for a complicated problem. But what happens when PFAS is in the mix?

In 2024, the paper “Dual effects of PFOA or PFOS on reductive dechlorination of trichloroethylene (TCE)” was published in the journal Water Research. PFAS and chlorinated solvents like TCE are often found in the same sites. The paper raised the concern that high concentrations of PFAS (approximately 50 to 100 milligrams per liter or mg/L) might inhibit the microbes used to bioremediate TCE, and in laboratory tests, it was found that high levels of PFAS were toxic to microbes. But do the bench tests reflect what’s happening in the field?

Other research has found that it’s not quite so simple. In some cases, PFAS seems to help with bioremediation by helping to dissolve the solvents, which makes them more available to the microbes. In others, it was found that non-PFAS ingredients in PFAS-based AFFF could provide nutrients that promote microbial growth. Fortunately for both humans and microbes, PFAS concentrations in the field likely aren’t high enough to have an impact. In the paper “Microbial Reductive Dechlorination by a Commercially Available Dechlorinating Consortium Is Not Inhibited by Perfluoroalkyl Acids (PFAS) at Field-Relevant Concentrations,” researchers found that anything below 38.7 mg/L doesn’t interfere with a reasonably diverse range of TCE-processing microbes. As concentrations above even 1 mg/L are rare, the microbes can go about their work with minimal worry.

If you’re practicing bioremediation of TCE and find PFAS, in the short term, update your monitoring to include tracking PFAS, if you think it’s a concern. In the long term, stay current on the research into this topic. This is a rapidly evolving branch of remediation science, and there’s likely more we’ll learn as more studies are done.