Fish Still Contaminated with Phased-out Chemical
ניתן לקבל שירות החלפת גלגל התקנה של A persistent chemical formerly used in Scotchgard still contaminates most fish in U.S. rivers and the Great Lakes despite a phase-out a dozen years ago, a new federal study shows.
U.S. Environmental Protection Agency researchers found perfluorooctane sulfonic acid (PFOS) in all of the 157 fish sampled from nearshore waters in the five Great Lakes and in 73 percent from 162 rivers.
The study, the largest of its kind in freshwater fish, suggests that eating bass, trout, walleye and catfish could be a major source of exposure for anglers and their families. The chemical remains widespread in wildlife, people and water around the world.
"This just shows that PFOS still dominates. Even though production stopped more than a decade ago, it's still the main perfluorinated acid in the environment," said Craig Butt, a Duke University chemist who was not involved in the study.
PFOS and other perfluorinated compounds are used in oil and water resistant coatings for pots and pans, clothes, paper, carpet and flame retardant foams.
The 3M Company, the major manufacturer of PFOS, voluntarily stopped its production in 2002 after scientists discovered that it was building up in water, wildlife and people.
Nevertheless, "every single human being we test has levels of PFOS in them," Butt said. The compound "doesn't break down in light, it doesn't oxidize. Once it's in the environment it's not going anywhere."
Most health studies have focused on communities with drinking water contaminated by PFOS. But people are exposed in many ways, said Sarah Knox, a professor and epidemiologist at West Virginia University. "Routes of exposure are multiple - things like linings of food containers, stain resistance sprays, fire-proofing and non-stick cookware," she said.
The EPA estimates that "contamination in food may account for more than 90 percent of human exposure to PFOS and PFOA" and that fish may be a major source of PFOS.
"It should be noted that the higher the fish is in the food chain, the greater the concentration of toxic compounds," Knox said.
In the rivers 25 fish species were tested, with smallmouth and largemouth bass and channel catfish the most prevalent. In the Great Lakes, 18 species were tested, mostly lake trout, smallmouth bass and walleye. The study did not name the rivers but the sites were mostly east of the Mississippi River.
PFOS, a suspected endocrine disruptor, has been linked to low birth weights, reduced immune system function in children andhigh blood pressure during pregnancy.
In addition, a study of about 47,000 people in West Virginia whose drinking water was contaminated by a DuPont plant linked PFOS to changes in liver function, early menopause in women and high cholesterol. Animal studies with rats and mice also have shown PFOS causes developmental, reproductive and immune system problems.
PFOA, another perfluorinated compound, was found in just 19 of the Great Lakes samples and none of the river samples. It has been linked to heart disease, suppressed immune systems in children and cancers.
Despite repeated requests, EPA officials would not allow the scientists who conducted the study to be available for an interview.
Of 13 compounds measured, PFOS was detected at the highest levels: In urban river fish it was measured at 4.8 to 127 parts per billion, and at 1.9 to 80 parts per billion in Great Lakes fish.
The EPA hasn't established a "safe dose" of PFOS. However, Minnesota health officials recommend eating only one meal of fish per week if PFOS concentrations are 40 to 200 parts per billion, and only one meal per month if 200 to 800 parts per billion. About 11 percent of the fish samples from U.S. rivers and 9 percent of the Great Lakes samples exceeded 40 parts per billion.
Minnesotas guidelines were developed using the federal drinking water standards, said Helen Goeden, a toxicologist with the states department of health.
Keri Hornbuckle, a professor at the University of Iowa who studies Great Lakes contaminants, said researchers suspect that wastewater treatment plants are an ongoing source of PFCs.
The compounds also travel on ocean and wind currents. "The animals with the highest levels of PFOS we know of are polar bears from the Arctic," Butt said.
New compounds have emerged after 3Ms phase-out of PFOS and PFOA, which the company eliminated in 2008. 3M has touted perfluorobutane sulfonate (PFBS) as a safe alternative, and the compound was not found in any of the river or Great Lakes samples. 3M did not respond to repeated requests for an interview.
Michael Murray, a scientist for the National Wildlife Federation, said that the key to addressing emerging contaminants in the Great Lakes is to look upstream now, before it's too late.
"We don't want to be dealing with the next round of perfluorinated compounds in five years," Murray said. "The key is pollution prevention, practices like green chemistry, to reduce the need for these chemicals in the first place.