Forever chemicals are an underestimated source of water contamination

At the beginning of 2023, the U.S. Environmental Protection Agency (EPA) proposed new rules for maximum allowable levels in drinking water for six per- and polyfluoroalkyl substances (PFAS). Although these human-made so-called “forever chemicals” have been widely used since the 1940s in various industrial and consumer products due to their unique properties, such as oil and water resistance, temperature resistance, and low friction, they can persist for a very long time in the environment, accumulate in the food chain, and lead to a number of health risks.

Unfortunately, according to a recent study led by the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in various sites across the U.S. – particularly in the vicinity of military bases – drinking water currently contains significantly higher levels of PFAS than EPA’s new guidance would allow.

PFAS are present in fire retardant foams which are widely used by the U.S. military for fire training drills and fighting fires in the form of aqueous film forming foam (AFFF), which is one of the largest sources of PFAS contamination in drinking water. 

The problem with monitoring the levels of these chemicals in and around military bases stems from the fact that PFAS compounds come in two forms – a precursor and a terminal form. While the terminal compounds do not degrade under normal environmental conditions, the precursor ones are usually transformed through biological and environmental processes into terminal forms.

Since the EPA’s draft drinking water rules are for six terminal compounds, they fail to take into account the massive presence of precursor compounds in military fire-retardant foams.

“Many PFAS precursors present in AFFF are difficult to measure. This work shows that they are slowly transforming into PFAS of health concern at AFFF-contaminated sites and contributing to downstream contamination,” said senior author Elsie Sunderland, a professor of Environmental Chemistry and Earth and Planetary Sciences at SEAS. 

Since much of the PFAS at military sites consists of precursors which are omitted from standard analytical methods, Sunderland and her colleagues used a previously developed technique to capture all the precursors in AFFF and model the expected duration and contribution of these precursors to groundwater contamination. The analysis revealed that the contamination of two newly regulated PFAS chemicals – perfluorohexane sulfonate (PFHxS) and perfluorbutane sulfonate (PFBS) – at a military base in Cape Cod, Massachusetts is sustained by microbial precursor transformation in the soil, from which they subsequently leak into groundwater in their terminal form at concentrations thousands of times higher than EPA’s safe threshold. 

According to the experts, without urgent advances in remediation technology that are effective at cleaning both terminal and precursor compounds, widespread PFAS contamination of drinking water supplies at the Cape Cod military base, as well as possibly 300 other military facilities across the country, is likely to persist for centuries.

“The role of PFAS precursors in sustaining hazardous levels of contamination at Joint Base Cape Cod raises concern about whether exposure risks are underestimated near hundreds of other sites where they are not measured,” concluded lead author Bridger Ruyle, a postdoctoral fellow at Carnegie Institution for Science in California and former doctoral student in Sunderland’s lab.

The study is published in the journal Environmental Science & Technology.

More about forever chemicals 

“Forever chemicals” is a term used to describe a group of man-made chemicals that are highly persistent in the environment and in the human body – meaning they don’t break down and can accumulate over time. The most well-known and widely studied of these are per- and polyfluoroalkyl substances (PFAS).

PFAS are a large group of more than 4,000 synthetic chemicals that are used in a wide variety of industries and products thanks to their resistance to heat, water, and oil. These characteristics have led to their use in a wide array of products, including non-stick cookware and food packaging materials.

However, because PFAS don’t readily break down in the environment, they can contaminate soil and water and then accumulate in wildlife and humans. Once in the body, they can stay for a long time and have been associated with a number of health concerns, including certain types of cancer, hormone disruption, liver damage, and issues with the immune system.

In recent years, there has been increasing concern about and attention to the environmental and health impacts of PFAS, leading to efforts to limit their use and improve their management. However, their wide use and persistence make this a significant challenge.

More about water contamination 

Water contamination can occur due to various factors, including both natural and human activities. Natural contamination can occur due to the presence of minerals like arsenic or fluoride in the groundwater, for instance. On the other hand, human activities can lead to water contamination through industrial effluents, sewage discharge, agricultural runoff, and more.

When it comes to drinking water, PFAS contamination is a major concern. These chemicals can accumulate in water sources like rivers, lakes, or groundwater, eventually making their way into the water supply. 

Several methods are available for the treatment and removal of PFAS from water, such as granular activated carbon (GAC), ion exchange resins, and high-pressure membrane systems like reverse osmosis. However, these technologies can be costly and complex to implement, especially for small communities. Also, they don’t destroy the PFAS but merely concentrate them, creating a challenge for safe disposal.

In many regions, regulations are being put in place to limit the levels of PFAS allowed in drinking water, and to mandate testing for their presence. There are also ongoing efforts to limit the use of these chemicals, to manage their disposal more effectively, and to clean up contaminated sites.

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By Andrei Ionescu, Earth.com Staff Writer

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