The Atlantic salmon being raised in Maine’s federal fish hatchery on Green Lake do not contain harmful levels of PCBs, mercury and other contaminants, the U.S. Fish and Wildlife Service said Thursday.

Earlier this spring, federal scientists sampled salmon and trout from five hatcheries to determine whether the fish contained toxic pollutants.

The testing was sparked by a widely reported but harshly criticized study published in the scientific journal Nature in January, which found aquaculture salmon contained more contamination than wild fish, likely because of the concentrated fish oils the farm-raised fish had consumed in their feed.

“We want to be proactive in making sure that the fish we’re providing for the American people are safe,” said Dan Kuzmeskus, hatcheries chief for the Northeast Region of the service, based in Hadley, Mass.

“Corny as it sounds, it was the right thing to do,” he said.

Polychlorinated biphenyls have historically been used in pesticides and some types of industrial and motor oils. Exposure to PCBs has been linked to cancer, liver damage, attention deficit disorder and damage to the immune system.

Like many pesticides, PCBs accumulate in animal fat, so they are of particular concern to wildlife and human health.

In total, 90 Atlantic salmon in Northeastern hatcheries were tested, including 24 at the Green Lake hatchery in Ellsworth. The fish, which included young and adults, were of Penobscot River ancestry but had all been raised in the hatchery.

All of the fish sampled met federal guidelines, the U.S. Fish and Wildlife Service report said.

Maine’s fish ranged from .0156 to .0236 parts per million of PCB contamination, and the Green Lake fish’s levels ranked the lowest of all the federal hatcheries.

None of the hatchery salmon even approached the 4.3 parts per million Maine Bureau of Health standard that triggers a warning that fish are not safe to consume.

Two factors likely contributed to the lower levels at Green Lake, Fred Trasko, a fisheries biologist at the hatchery, said Thursday.

None of Green Lake’s fish had ever been to the ocean, where their diets would not be controlled. In the wild, many salmon often feed on capelin, an oily fish that would hold contaminants well, Trasko said.

At the hatchery, biologists make a point of seeking out feed with lower levels of fish oil, and feeds made from species low on the food chain, to reduce the risk of contaminating the salmon with environmental pollutants, he said.

“I was confident that we’d come out low,” he said.

None of the fish were pollutant-free, but, overall, none of the 138 fish tested exceeded EPA consumption levels for PCBs, mercury, dioxins or pesticides. All of the salmon were deemed safe for one meal per month, according to EPA guidelines.

Had any of the fish exceeded federal consumption guidelines, they would not have been released into rivers and lakes where they could pose a risk to fishermen, Kuzmeskus said.

Michael Belliveau of the Environmental Health Strategy Center in Bangor said Thursday that he agreed that the hatchery fish seem to be “relatively clean,” with PCB levels slightly higher than data he has seen for wild fish, and slightly lower than aquaculture fish rated in the Nature study.

But state advisories still recommend limits on the consumption of almost all fish that have lived in Maine’s waters, particularly for pregnant women and children under age 8.

It’s illegal to fish for and eat the 685,000 Atlantic salmon from Green Lake that are released into the Penobscot River each year in an attempt to rebuild its struggling population, but people should still consider the impacts of allowing these fish to become contaminated to any degree, Belliveau said.

“We should still be concerned about building up PCBs in the food chain,” he said.

Kuzmeskus said that the U.S. Fish and Wildlife Service is using the data to develop a plan for further reducing hatchery fish’s exposure to PCBs and other pollutants.

“We want to produce fish that the public knows are safe,” he said.

For more information about Maine state fish consumption advisories, see http://www.maine.gov/dhs/ehu/fish/ For more information about the federal study, visit http://northeast.fwsgov/fisheries/issues/issues.htm