BOSTON (AP) — Toxins leached from packaging into a pesticide commonly used on mosquitoes, the Environmental Protection Agency has found, but the risks to human health are unclear.

Testing by the EPA found the pesticide, Anvil 10+10, contains perfluoroalkyl and polyfluoroalkyl substances, known collectively as PFAS, The Boston Globe reported Thursday.

The EPA determined that fluorinated “containers that are used to store and transport a mosquito control pesticide product contain PFAS compounds that are leaching into the pesticide product.”

The St. Charles, Illinois, company that manufactures the pesticide, Clarke, said that its tests had not found the chemicals in its products but that it has stopped the sale and shipment of the pesticide in plastic containers, the newspaper reported.

“The potential for PFAS chemistry from the fluorinated packaging to leach into finished goods was unknown to Clarke,” the company said in a statement to the newspaper.

Massachusetts has sprayed the pesticide from planes and using trucks to reduce the risk of people contracting diseases from mosquitoes, according to the state agency for infectious diseases. The EPA has not released the levels of PFAS it found in the pesticide and says on its website that it is still evaluating whether there are public health risks.

The EPA began testing the pesticide in response to findings from an advocacy group, Public Employees for Environmental Responsibility, that initially tested the pesticide and found elevated levels of PFAS. The organization estimates that some 30 states spray the pesticide in the air to reduce the mosquito population, the newspaper reported.

PFAS — perfluoroalkyl and polyfluoroalkyl substances — are human-made chemicals that research suggests can cause health problems including cancer and weakened immunity. Found in many products like nonstick cookware and firefighting foam, they are also called “forever chemicals” for their longevity in the environment and resistance to destruction.