“Forever chemicals,” officially called per- and polyfluoroalkyl substances, or PFAS, are incredibly persistent, widely used chemicals that are now present in soil, water, and human bodies. Some PFAS are now linked to cancers, reproductive issues, and developmental delays in children.

Concerns about those health risks are compounded by the fact that authorities have not identified all sources of PFAS contamination in the environment. The U.S. Environmental Protection Agency (EPA) and other regulators have been trying to understand the scope and impacts of contamination from a wide range of sources, including firefighting foam, sewage sludge, and food packaging. Last year, the EPA proposed the first drinking water limits for four of the chemicals.

The new analysis, published today in Environmental Health Perspectives, represents the latest effort to understand how common PFAS are in pesticides, which are widely used around the country and directly affect food, water, and soil. The researchers, associated with environmental advocacy groups including the Center for Biological Diversity, Public Employees for Environmental Responsibility (PEER), and the Environmental Working Group, found that 66 active ingredients currently approved for use in pesticides qualify as PFAS, and eight approved “inert” ingredients—added to pesticides to help the chemical disperse, for example—also qualify as PFAS.

Most of the chemicals identified are referred to as “short chain” PFAS, which means they are likely less persistent and less toxic than the more common forever chemicals—like PFOA and PFOS—that the EPA has begun to regulate. But more research is needed on their impacts, the researchers say.

Plus, overall, they found that fluorination (a process that can create PFAS) is increasingly used by chemical companies in the manufacture of pesticides, to make them stick around for longer. While 14 percent of the overall active ingredients currently used in pesticides qualify as PFAS, 30 percent of the ingredients approved in the last decade qualify.

“What’s clear is that some of the most widely dispersed pollutants across the world are becoming increasingly fluorinated, which means that they’re becoming increasingly persistent, and we don’t really have a grasp yet on what the consequences are going to be,” said Nathan Donley, one of the paper’s authors and the environmental health science director at the Center for Biological Diversity. “What our research showed is that this issue is a lot bigger than many people have thought, and the trend is really worrisome.”

Of course, fluorination is not unique to the pesticide industry, said A. Daniel Jones, a professor of biochemistry and molecular biology and the associate director of Michigan State University’s Center for PFAS Research. Common medicines like Prozac and Lipitor, for example, meet some definitions of PFAS. “We could get rid of lots of really important drugs if we got rid of all of the organic fluorine,” he said. “At the same time, we do want to start moving away from non-essential uses of persistent organic chemicals. Any chemical that outlives me is probably not good to have moving around the environment.”

The study contributes to the still-developing picture of how significant of an issue PFAS in pesticides might be. In 2022, testing done by environmental groups found the chemicals in common pesticide products, which has since been partially attributed to leaching from plastic containers. The EPA took steps to address that contamination. However, an independent researcher also found alarming levels of the most dangerous PFAS in multiple pesticides that wasn’t attributable to plastic containers. EPA then did its own tests and announced no pesticides were found, but the agency is now facing allegations of misconduct related to that testing.

The EPA did not respond to requests for comment by press time.

Short-Chain PFAS Are More Common in Pesticides

One of the aspects at issue is the length of the carbon chain. All PFAS contain a chain of carbon atoms connected to fluorine atoms, and it’s widely understood that the longer the carbon chain, the more problematic the chemical, in terms of both environmental persistence and health impacts.

Most of the active and inert ingredients now being used in pesticides are short chain and are not from the class of PFAS that have been the focus of regulatory efforts so far, so a looming question is: Are they of serious concern?

“From my perspective, ultimately, it doesn’t matter whether you think these are PFAS or not,” Donley said. “They are forever chemicals, and the fluorinated parts of these pesticides will be around for the birth of your grandchildren’s grandchildren.”

While these chemicals are “certainly persistent,” Jones agreed, their impact across the board is unknown.

In terms of health, one of the reasons PFOS and PFOA are so dangerous is that they can stay in the human body for up to a decade, wreaking havoc all the while. “The longer they’re in us, the more opportunity they have to do harm,” Jones said. “Generally, we do know that shorter chain compounds don’t stay in your body as long as the longer chain compounds. So the short-chain compounds are probably not nearly as bad for us as the long-chain compounds, but that doesn’t mean they’re completely innocuous either.”

In the environment, their persistence is complicated, since even those that do degrade in a reasonable amount of time can break down into other compounds that don’t, Donley said. Of course, that doesn’t mean those other compounds are necessarily toxic. For example, Jones has extensively studied one of the compounds identified in the paper, trifluoroacetic acid (TFA), as a substance into which PFAS can break down. He pointed to a recent assessment of toxicity in mammals that found TFA doesn’t pose significant health risks.

In addition, because these chemicals are so widespread in other products, it’s hard to pinpoint how significant pesticides may be as a source of contamination. For example, research shows refrigerants and other non-pesticide chemicals are a much more significant source of TFA pollution.

While most of the chemicals identified in the paper are not the most common pesticides used, some have been used in high volumes in the past, and others are seeing increased use.

In the 1990s, for example, farmers annually sprayed about 25 million pounds of an insecticide called trifluralin, which the researchers identified as PFAS. While its use has since plummeted, in 2018, farmers still used 5 million pounds on crops including cotton, alfalfa, and fruits and vegetables. Use of the herbicide fomesafen—also identified as PFAS in the new study—has gone in the other direction, increasing from just 1 million pounds in the 1990s to nearly 6 million pounds in 2018, primarily on soybeans.

And some of the 66 chemicals identified in the study are used as the active ingredient in a much larger number of products. For example, Bifenthrin, a major water contaminant in the U.S., was an ingredient in 247 different pesticide products registered in Maine in 2022.

Regulatory Implications for PFAS in Pesticides

“When you start getting into breakdown products, the system falls apart pretty quickly, and they’re not getting a whole lot of information on what these breakdown products are doing in the environment,” Donley said. “There are just a lot of question marks there.”

He also questions whether the EPA is effectively evaluating and regulating the additive ingredients called “inerts.” Due to the way the nation’s pesticide law was written, those chemicals are considered confidential business secrets, so companies don’t have to list them on pesticide labels.

So while the paper’s authors were able to identify eight approved inerts that qualify as PFAS, four of which are currently used in products in the U.S, there’s no way to know which products contain them. One such chemical, for instance, is approved for use on food crops and is present in 37 products, according to the EPA. Since the agency doesn’t share the names of those products, we don’t know if they are in wide use—or hardly used at all.

In regulatory recommendations at the end of the new paper, Donley and his co-authors say the U.S. should require all pesticide ingredients, including inerts, to be disclosed on labels. They also recommend the agency evaluate all PFAS pesticides and the compounds they break down into for environmental persistence, expand environmental and biomonitoring programs for PFAS pesticides, and assess the cumulative impacts of all the pesticides and the compounds they break down into based on the “total organic fluorine load in the environment and food.”

Michigan State’s Jones called the goals lofty and said they’d require an enormous amount of resources—which the agency currently does not have. “A more circumspect approach might begin by prioritizing items that present the greatest risk to human health, but should also evaluate the health effects of any proposed alternatives,” he said.

Even before the study, in the absence of more aggressive EPA action on the issue, states have been stepping in. Maine, Minnesota, Maryland, and Massachusetts have all passed laws that specifically tackle PFAS in pesticides in some way. Maine and Minnesota have already begun the process of identifying PFAS in pesticides, with a goal of understanding their impact and eventually ending their use.

Pesticide companies now submit PFAS affidavits when they register their products in Maine. The Minnesota Department of Agriculture, which uses a broader definition of PFAS than even the OECD, issued an interim report earlier this year that identified 95 pesticides that qualified as PFAS. The agency also began looking at contamination in groundwater, rivers, and streams.

“There’s a lot coming out that’s going to make it easier to piece together, state by state, what’s happening,” said Sharon Anglin Treat, an environmental policy expert who has been working on PFAS contamination in Maine. “We’re only regulating the tip of the iceberg in terms of the federal EPA drinking water standard. The more we find out about PFAS, the more concerning they are.”

That’s why, Donley said, the overall trend of fluorinating pesticides to make them more persistent is something regulators should be paying attention to.

“In the ’70s, we were dealing with things like DDT and aldrin and chlordane, really persistent chemicals,” he said. “The EPA kicked that to the curb. Now, we’ve almost come full circle. Whereas the 1970s was the age of the organochlorine [like DDT], now we’re living in the age of the organofluorine, and the persistence is really nerve-wracking, because it wasn’t until decades later that we figured out the long-term consequences of using DDT. . . and we’re still dealing with the ramifications.”