Scientists have been raising growing concerns for decades over the use of toxic “forever chemicals,” so called because their strong molecular bonds can take hundreds of years to completely break down in the environment. These chemicals are found in many consumer products, including cookware and clothing. They can also be found in our bloodstreams. And now researchers are warning of yet another–and so far underrecognized–source of these troubling toxins: common pesticides. Nearly 70 percent of all pesticides introduced into the global market from 2015 to 2020 contained these chemicals or related compounds, according to a review paper recently published in Environmental Pollution. The increase in their use has occurred without a complete understanding of their potential effects on the environment and human well-being.
Forever chemicals–scientifically known as perfluoroalkyl and polyfluoroalkyl substances, or PFASs–are a subset of so-called fluorinated chemicals, which possess strong carbon-fluorine bonds. These chemicals are highly stable and can be used in products that repel grease and water. However, they are not easily biodegradable. Though governments have been working to limit the use of PFASs, those efforts are complicated by differing technical definitions of which fluorinated chemicals are technically PFASs–and as such pose a risk to people and the environment. Many chemicals that are considered PFASs in large parts of the world do not have the same classification in the U.S. This could lead to communities being exposed to dangerous chemicals, such as pesticides that are fluorinated and sprayed on many crops around the globe every year.
Pesticides made from fluorinated chemicals, commonly referred to as fluorinated pesticides, “can be incredible molecules that meet a lot of the challenges that exist in agriculture,” says study co-author Diogo Alexandrino, a researcher at the University of Porto in Portugal and a co-author of the Environmental Pollution paper. “But they should be properly vetted, and we should be aware that they can have a very huge impact on the environment, on biodiversity and eventually on our own health.”
Stability or Persistence?
Fluorinated chemicals, including PFASs, have been widely used in consumer products since the 1940s. But in the following decades scientists began realizing that these chemicals persisted in drinking water and human bodies, and in the 1990s the Environmental Protection Agency began investigating PFASs. Nearly all Americans have low levels of PFASs. These chemicals have been linked to testicular and kidney cancers, reproductive disorders, thyroid disease, high cholesterol levels, reduced immune response and even increased susceptibility to COVID-19. Based on these concerns, the U.S. Congress is weighing several bipartisan bills to restrict their use in food containers and cookware and to require the EPA to take comprehensive action to prevent PFAS pollution–including setting national limits on levels in drinking water. Under the Biden administration, the EPA has published a PFAS Strategic Roadmap for addressing the crisis. Eight states have already passed laws banning PFASs in certain products and packaging, but not pesticides.
Fluorinated pesticides first appeared on the market in the 1930s, but it is only in the past decade that this use has expanded so dramatically. Alexandrino explains that this rise can be attributed to improvements in manufacturing processes, as well as the expiration patents that have allowed for greater competition.
Fluorinated insecticides provide “efficacy” and stability for pest management, according to Karen Reardon, spokesperson of Responsible Industry for a Sound Earth (RISE). This stability allows pesticides to be more effective for longer periods of time, so crops can be sprayed less frequently than with nonfluorinated alternatives.
Some call stability, while others call persistence. Alexandrino and his colleagues compiled data that shows half-lives, which are the time it takes for chemicals to dissipate half in the environment. These range from a few days up to 2.5 years for top-selling fluorinated insecticides. That is less than the half-lives of some older pesticides such as DDT, but at the upper end of the scale, it is still a relatively long time: the EPA defines a “persistent” pollutant as having a half-life of 60 days or more. Kyla Bennett, science director at the non-profit environmental advocacy organization Public Employees for Environmental Responsibility (PEER), bluntly stated that PFAS should not be allowed to be in something that is sprayed on millions or millions of acres every year. It’s called a forever chemical for a reason.”
What Is–and Isn’t–a PFAS?
One of the most widely used fluorinated pesticides is bifenthrin. It targets insects’ nervous system and is the prime ingredient in more than 600 pesticide formulations used on corn, soy, vegetables, berries and orchard crops. It is also used in urban pest control, such as termites, ants and termites, and as a treatment for seeds. Although its potential health effects on humans are not known, there is evidence that chronic exposure may cause neurotoxicity. The EPA has also classified it as a human carcinogen. Ultimately, the EPA concluded in a 2020 human health risk assessment that “dietary exposure and risk estimates are not of concern for the existing uses of bifenthrin”–at least when levels designated as safe for human consumption are not exceeded. However, recent amounts found on collard greens and eggplants, sweet potatoes, sweet potatoes, and cherry tomatoes have exceeded the EPA safety levels. Removing such residues from produce requires extra scrubbing because bifenthrin is an oily substance.
Bifenthrin is also a persistent pollutant with a half-life of 97 to 345 days in soil, depending on soil type. A 2016 U.S. Geological Survey study found that it binds to sediments contained in stormwater and can persist in surface waters, where it harms beneficial insects that provide food for fish, birds and wildlife. Maria de Fatima Carvalho from the University of Porto, co-author of the paper, said that the particular combination of carbon and fluorine is “really strong and will be really persistent within the environment.”
Although bifenthrin is one of more than 200 active pesticide ingredients that would be recognized as a PFAS by the latest Organization for Economic Co-operation and Development (OECD) definition and is banned for most agricultural uses in the European Union, the EPA has a narrower definition of a PFAS. Different definitions make it difficult to regulate the use of these chemicals. Because compounds with longer carbon-fluorine molecule chain chains are less likely to accumulate in the food stream and therefore less toxic, the EPA definition excludes them. Experts disagree on this. Rolf Halden from Arizona State University’s Biodesign Center for Environmental Health Engineering says that it is wrong to claim that everything is safe unless there are two, three, or four [carbon-fluorine], bonds. “We have created a chemistry that has no known biodegradation mechanism. You’re signing up for a lifetime of exposure around the world and for millennia.”
In an e-mail to Scientific American, EPA spokesperson Robert Daguillard wrote that the agency’s PFAS definition, first developed in 2006, was intended to “identify the PFAS most likely to present risk to human health and the environment.” The definition has since been adjusted, Daguillard added, and “we are currently looking at the differences between the OECD and [EPA] definitions to determine whether the [EPA] definition should be modified to capture additional substances.”
At least three active pesticide ingredients currently allowed by the EPA–broflanilide, pyrifluquinazon and noviflumuron–meet its definition for a PFAS. The EPA has banned four other PFASs, but they are still being used in Japan and China. New pesticide ingredients that EPA classifies as PFASs are still being introduced to the Chinese market. The half-lives of the three approved pesticide ingredients in the U.S. are only a few months, but that is not enough to tell the whole story, according to Nathan Donley, environmental science director at Center for Biological Diversity, a non-profit conservation group. Donley states that while they appear to be able to break down in a reasonable time, the by-products of this breakdown must also be considered. He adds that the parent pesticide molecule can be broken down into a more complex molecule, which is still fluorinated. “And what those degradation products do in the environment is really never followed up with at all,” Wendy Heiger-Bernays at the Boston University School of Public Health says that fluorinated pesticides’ breakdown products may interact with other environmental pollutants in unspecified ways.
EPA spokesperson Cathy Milbourn said that the agency has a robust process for identifying the environmental risks from pesticide degradation products and metabolites. But Donley argues the EPA doesn’t follow the entire process of pesticide degradation, which can take decades or even centuries and can produce dozens more molecules. It is important to remember that what happens in nature does not always reflect what happens in laboratories. Donley states that while I don’t expect the EPA or any other agency to conduct all of the necessary research to find definitive answers to all these questions, they must account for uncertainty. “The benefit of the doubt should be given to people and the environment, not to the pesticide companies.”
When Scientific American asked what actions the EPA may take to restrict pesticides that do meet its definition of a PFAS, Milbourn responded in an e-mail that “regardless of the evolving definition of PFAS, pesticides undergo a rigorous scientific assessment process prior to registration” and that “fluorinated pesticides in commerce have met appropriate risk-based standards for registration.”
But PEER’s Bennett was previously employed at the EPA’s New England region office for over a decade. Bennett claims that the data used by the agency to evaluate pesticide safety is almost entirely provided to them by manufacturers. This leaves regulators open to “incredible sector capture” and “political pressure” in order to get pesticides onto the market. She claims that EPA staff evaluating pesticide risk do not have enough information to do their jobs correctly. Recent reporting by the Intercept and Investigate Midwest has also brought these issues to light. Bennett’s points were addressed by RISE’s Reardon, who stated that the “EPA’s pesticide determinations” are made only by the agency, as it fulfills its remit in the Federal Insecticide, Fungicide and Rodenticide Act.
” The EPA and everyone are claiming that these [fluorinated pesticides] are better than the older [nonfluorinated] versions. Donley admits that this might be true in some cases. “But it’s really worrisome to me that even though these don’t technically meet the EPA definition of PFAS, they meet the PFAS definition of much of the rest of the world.”
Some people, however, prefer to concentrate on pesticides that have been EPA-labeled PFASs. Graham Peaslee, a professor of physics from the University of Notre Dame, says, “We’ve seen fluorescent groups in insecticides but I wouldn’t call those PFAS.” Heiger-Bernays says she is also “less concerned” about the possibility of human harm from pesticides like bifenthrin. She emphasizes that she is not a pesticide advocate, but she does acknowledge that there are legitimate uses for pesticides.
Whether the EPA’s PFAS Strategic Roadmap will lead to action on fluorinated pesticides–particularly those that meet its PFAS definition–remains to be seen. In an e-mail to Scientific American, Milbourn wrote that “as EPA continues to refine the testing process, as regulatory work matures, and as the Agency learns more from its partnerships across the country, the Agency will adjust the definition of PFAS to reflect the information gathered through this process. Once the agency has determined the scope of the issue, it will continue to use every regulatory and non-regulatory tool to address PFAS .
For some, these words are not reassuring. “I think many of us are holding our breath. Donley states that we don’t really know much right now. “I’m hoping for the best, but I think it’ll take a few years, or even a few decades, to really grasp what is going to happen with a