Read the full article XiaoZhi Lim (C&EN)
“For 3 decades starting in the 1940s, General Electric dumped solvents from its manufacturing facilities into New York’s Hudson River, contaminating it with polychlorinated biphenyls (PCBs). Scientists worried about how best to clean up the pollutants. ‘At that time, they thought PCBs were completely nonbiodegradable,’ says Lawrence P. Wackett, a biochemist at the University of Minnesota Twin Cities who consulted for the company in the late 1980s.
But analysis of sediment cores extracted from the river throughout the 1980s showed that the PCBs were slowly losing their chlorine atoms and turning into benign hydrocarbons. Later, scientists determined that the transformation was performed by microbes (Science 1987, DOI: 10.1126/science.236.4802.709).
Now, researchers are hoping microbes could do the same for per- and polyfluoroalkyl substances (PFAS), also known as forever chemicals. Used in personal care products as well as firefighting foam, stain-repellent coatings, and membranes for chlor-alkali production, PFAS have strong carbon-fluorine bonds that make them difficult to degrade. PFAS have become a high-profile contaminant, polluting areas near manufacturing facilities that make or use them and military sites like air bases. Researchers are still trying to fully understand the health effects of PFAS but have determined that some are carcinogenic and toxic to multiple systems.
Traditionally, to treat contaminated water, remediators first concentrate the PFAS, typically via an activated carbon filter, and then incinerate the saturated filters at high temperatures. Biological remediation could be more cost effective for low levels of PFAS in large volumes of contaminated material. So far, no organism has been found that can completely defluorinate PFAS, but researchers have no reason to believe that microbes couldn’t eventually do the job. ‘Never say never in terms of what they can’t handle,’ Wackett says.
The US Department of Defense’s Strategic Environmental Research and Development Program (SERDP) has funded extensive research into the chemical and physical remediation of PFAS. In 2018, SERDP launched a call for research proposals exploring the biodegradation of PFAS and awarded $2.75 million to five projects beginning last year.
However, other scientists, like Rolf U. Halden, an environmental engineer at Arizona State University, worry that investigating bioremediation of PFAS distracts from the real work of having to dial back on their use. Halden is ‘very, very skeptical’ that a microbe could be practically deployed to remediate PFAS. ‘I think that this will only delay the actual hard question that we have to answer: How much [PFAS] is too much, and how do we get to a healthy use of these very useful materials?’ he says…”