With mosquito season here again, there’s reason to wonder if the annual spraying of Chesapeake Bay watershed communities to control the pesky insects could also have put humans at risk by exposing them to “forever chemicals.”
A pair of environmental groups reported recently that high levels of per– and polyfluoroalkyl substances, or PFAS, were detected in a sample of a widely used mosquito insecticide that is sprayed every spring and summer in the streets of 2,100 communities across Maryland, as well as in other states.
Maryland annually sprays 2,100 communities in 16 counties to kill adult mosquitoes. The state switched pesticide brands this spring after high levels of two PFAS compounds were found in the insecticide the state has used in the past. (Edwin Remsberg/Maryland Department of Agriculture)
Public Employees for Environmental Responsibility and the Maryland Pesticide Education Network announced in late March that a sample of Permanone 30-30, used by the Maryland Department of Agriculture for a statewide mosquito control program, contained 3,500 parts per trillion of perfluorooctanoic acid (PFOA). That is one of the thousands of PFAS compounds known to be in use in manufacturing and commerce.
The sample tested also had about 630 ppt of another PFAS compound, hexafluoropropylene oxide dimer acid (HFPO-DA), a PFOA alternative trademarked as GenX.
PFAS remain largely unregulated in the United States, though the U.S. Environmental Protection Agency has set a “lifetime health advisory” threshold of 70 ppt for PFOA. European regulators have expressed concern about the safety of HFPO-DA and its variants, citing research that shows they also affect human health and the environment.
Environmentalists say that because PFAS persist and build up in bodies when ingested, finding the chemicals in pesticides being sprayed throughout communities is particularly troubling. Studies have linked PFAS exposure to liver damage, thyroid disease, developmental issues, reduced fertility, high cholesterol, obesity, hormone suppression and cancer.
“Spraying millions of acres with a chemical that does not break down in the environment, and for which there is no safe means of disposal, is beyond nonsensical,” said Ruth Berlin, executive director of the Maryland Pesticide Education Network.
PEER executive director Tim Whitehouse called on the EPA, which regulates pesticide content, to test all mosquito sprays for PFAS.
On May 7, EPA spokesman Ken Labbe said the agency “is currently reviewing the data from PEER on Permanone 30-30 and will provide information and guidance on next steps expeditiously.”
Permanone 30-30, produced by the Germany-based pharmaceutical giant Bayer Corp., had been used in the past in Maryland’s mosquito control program. Every year beginning in May, truck-mounted “foggers” spray residential and recreational areas in communities in 16 counties.
Last fall, PEER also reported finding PFOA in samples from Massachusetts containing another widely used mosquito-control pesticide, Anvil 10+10, which is made by Clarke, a company based in St. Charles, IL.
After confirming the results from Massachusetts, the EPA in January said it had determined that the PFAS had leached from fluorinated plastic containers used to store and transport the pesticide. Plastic and other containers for holding chemicals are often treated with fluorine gas to prevent vapors from escaping or to keep oxygen from getting in.
It’s unclear how fluorination of containers produced fluorine-containing PFAS compounds in the pesticides, but the EPA said it was looking into it. In the meantime, the agency has asked states with existing stock of Anvilto discontinue its use, and the manufacturer voluntarily halted shipments in those plastic containers.
Now, with PFAS reported in a second pesticide, Labbe said the EPA would be working as needed “with states and registrants to test additional pesticide products and the containers they are stored in for PFAS.”
Before PEER reported it had found PFAS in Permanone, the EPA had already announced that it was testing different brands of fluorinated containers to see if they contain or leach PFAS. It also said it was encouraging pesticide manufacturers to consider alternative packaging, such as metal or non-fluorinated plastic.
The EPA allows some PFAS to be used as either an active or inert ingredient in pesticides. But Labbe, the EPA spokesman, said the agency has determined that the pesticides in question did not themselves have any active or inert ingredients with chemical structures similar to PFOA, or the GenX alternative. He said the agency is still checking for the possible presence of any of the thousands of other PFAS compounds.
Susan Luke, a spokesperson for Bayer’s crop science division, said by email that the two PFAS compounds found by PEER are not ingredients of Permanone and that the pesticide is not shipped by Bayer in fluorinated containers.
“We are actively working with the EPA to better understand this topic and the relevance to Permanone 30-30,” Luke added, “including looking into the chemical makeup of the lids and other components of the product containers.”
In the meantime, state and local agencies in the Bay watershed are adjusting their mosquito control programs for this year.
In Pennsylvania, the Department of Environmental Protection ordered county mosquito programs to stop using Clarke’s Anvil 10+10, according to DEP spokesman Jamar Thrasher. The department also tested non-Clarke pesticides in plastic containers “and found those products to be free of PFAS contamination,” he said by email.
The Maryland Department of Agriculture likewise has switched to two other insecticides for truck-based spraying this year “out of an abundance of caution,” according to MDA spokesman Jason Schellhardt. State officials, he said, have been assured by the companies involved with the replacements, Biomist 30+30 and Permasease 30-30, that measures have been taken with both products to eliminate exposure to fluorinated containers.
Karen Larson, Clarke’s vice president for product innovation and government affairs, said it stopped distributing all of its pesticide products in fluorinated containers as soon as it learned of the EPA’s findings earlier this year. The company also has offered to take back all of its products in fluorinated plastic barrels and jugs and replace them in non-fluorinated packaging, Larson said by email.
Kyla Bennett, PEER’s science policy director, said her group has not tested Biomist for PFAS. The Permanone tested came from a metal container, she said, but it’s possible the insecticide had been previously stored or shipped in a larger fluorinated plastic container.
But after finding PFAS in two pesticides, she said in an email, “I am not convinced any pesticide is PFAS-free until I see tests from an independent lab [with appropriate detection limits].” Otherwise, she warned, “we may be jumping from the frying pan into the fire.”