After limited seafood testing, the U.S. Food and Drug Administration has found the presence of PFAS chemicals at levels many times higher than the federal recommended limit in some smoked clams and tuna.

The FDA tested 81 samples of clams, cod, crab, pollock, salmon, shrimp, tuna and tilapia, finding smoked clams imported from China with PFOA levels more than 5 million times the U.S. Environmental Protection Agency’s lifetime health advisory for drinking water and 61,000 times the lifetime health advisory for PFOS.

The drinking water lifetime health advisories are nonenforceable guidelines that take into account exposure to other sources of PFAS beyond drinking water, including food, air, consumer products and other sources.

Testing also found the presence of a dozen other unregulated PFAS chemicals in the clams.

The agency did not identify the brands tested, but said the imported canned clams were “likely a health concern” for people who eat more than 10 ounces of the clams in a month or young children who eat more than 2 ounces per month.

PFAS are a family of thousands of synthetic chemicals used since the 1940s to make products resistant to heat, water, grease and stains. PFAS are known as “forever chemicals” because they are extremely persistent, lasting thousands of years in the environment and at least five years inside human bodies.

The chemicals are linked to a variety of adverse health conditions like increased risk of kidney or testicular cancer, increased cholesterol levels, increased risk of high blood pressure or pre-eclampsia in pregnant women, changes in liver enzymes, decreases in infant birth weight and decreased vaccine response in children.

At least one company that sells the canned smoked clams, Bumble Bee Foods LLC has issued a voluntary recall on the products. The FDA said a second company had also committed to a voluntary recall.

Beyond the canned clams, FDA testing found canned crab meat imported from Indonesia and Mexico with elevated PFOA levels and other PFAS chemicals.

Atlantic salmon showed the presence of PFDoA, a PFAS chemical that occurs when stain-proof and grease-proof coatings on food packaging, couches and carpets break down.

Canned tuna imported from Ecuador, Nicaragua and Thailand had high levels of PFUdA, a chemical used in textiles, surfactants, lubricants and food packaging, and PFDoA.

Cod imported from various nations had high levels of PFUdA, PFDoA, and the similar chemicals, PFTrDA and PFTeDA.

Some fish sticks made from pollock derived from the U.S. or China showed an elevated presence of PFDA and PFDoA.

The tilapia and shrimp tested by the FDA had the lowest occurrence of PFAS chemicals.