Researchers find harmful ‘forever chemicals’ in pesticide used against mosquitoes in Maryland

Lab tests ordered by environmental groups found harmful chemicals, called PFAS, in a pesticide that Maryland uses for its mosquito control program, the groups said Thursday.

PFAS — per- and poly-fluoroalkyl substances — are known as “forever chemicals” because they don’t break down in nature, and they’re found in all kinds of products, from nonstick cookware to firefighting foams.


“The results for us are extremely disturbing, given the health impacts linked to these forever chemicals,” said Ruth Berlin, executive director of the Maryland Pesticide Education Network, which helped pay for the tests.

Last year, Maryland environmental regulators announced they intended to begin testing drinking water and Chesapeake Bay oysters for PFAS, since a growing number of studies linked the chemicals to liver, kidney and reproductive dysfunction, as well as high cholesterol levels and tumor growth.


The recent testing, ordered by Berlin’s organization and the group Public Employees for Environmental Responsibility, found 3,500 parts per trillion of one type of PFAS and 630 parts per trillion of another in Permanone 30-30, a pesticide sprayed by Maryland’s Department of Agriculture.

The Environmental Protection Agency has set a lifetime health advisory for two types of PFAS in drinking water at 70 parts per trillion. Such advisories mean the agency has determined that consistent daily exposure at or below that level isn’t likely to cause adverse effects.

The Maryland Department of Agriculture’s mosquito control program serves 2,100 communities in 16 counties, and spraying typically begins in mid-May in Southern Maryland and the Lower Eastern Shore. In other parts of the state, it begins in late May and early June.

“MDA and private vendors are going to begin their applications in numerous communities in the state,” Berlin said. “The impact of that exposure could affect hundreds of thousands of Marylanders.”

A spokesman for Maryland’s Department of Agriculture said the agency is reviewing the study and will wait for further guidance from the EPA.

“Early findings from the U.S. EPA suggest that PFAS levels found in pesticides are related to plastic containers. All of the Permanone 30[-]30 used by MDA’s Mosquito Control Program is packaged in metal containers,” wrote spokesman Jason Schellhardt in a statement.

An EPA spokesperson said the federal agency has received this research, and “will review it as part of the agency’s ongoing efforts to investigate PFAS contamination in pesticide products.”

“EPA understands the need to provide guidance to states, tribes, and other users as they prepare to purchase mosquito control products for 2021 and will provide more information as it continues its investigation,” read a statement from the agency.


After Public Employees for Environmental Responsibility, known as PEER, found PFAS in a different pesticide, called Anvil 10+10, last year, EPA officials said that fluorinated plastic containers used for storage may be to blame. The agency asked states with pesticides stored in such containers to pause their use while it investigates whether they contain or leach PFAS.

But concerned environmental and public health groups worry the chemicals may be discovered in a number of different pesticides, even those that don’t use the same type of container.

“Our suspicion was that: Maybe it was the barrels in the case of Anvil, but that wasn’t the end of the story,” said Kyla Bennett, PEER’s director of science policy.

Meanwhile, the Maryland Pesticide Education Network became concerned that Permanone could contain PFAS, since it’s the same sort of pesticide as Anvil, Berlin said.

Last year, PEER released the results of testing conducted on seafood in St. Mary’s County and drinking water in Montgomery County, which found high levels of PFAS. The group tested oysters, crabs and rockfish caught near the Patuxent River Naval Air Station, where the chemicals are believed to have been used in firefighting exercises over many years. That practice will be prohibited in Maryland starting in October. The group also tested drinking water in three homes in Poolesville and Bethesda.

As researchers discover PFAS in a variety of products, consumers ought to educate themselves whenever possible, and purchase products known to be PFAS-free, Bennett said. They also should consider water filtration systems for their homes.


“It’s absolutely a game of Whac-A-Mole,” she said.