The millions of carp causing problems for Utah Lake's native fish also may pose a health threat to humans.
Elevated PCB levels have been found in carp collected from the lake, leading state and Utah County officials Tuesday to issue a fish-consumption advisory.
The Utah Department of Health recommends that adults eat no more than one 8-ounce serving of carp from the lake per month. The fish should not be consumed by children, pregnant and nursing women, or women who may become pregnant.
The advisory will be posted on signs at access points to Utah Lake.
PCBs polychlorinated biphenyls are man-made chemicals that were used as coolants and lubricants in transformers, capacitors and other electrical equipment, said John Whitehead, a hydrologist in the state Department of Environmental Quality.
They're also "probable human carcinogens," according to the Environmental Protection Agency, and can cause harmful health effects such as reduced ability to fight infections, low birth weights and learning problems.
"They're not really known to cause cancer in humans, but they can cause cancer in animals," said Jason Scholl, a toxicologist with the state health department.
Those cases were the result of prolonged exposure to PCBs, Scholl said.
PCB levels detected in the carp from Utah Lake were below EPA screening levels for non-cancer effects, he said, meaning the health risks from eating the fish are minimal.
It would take significant consumption of the carp over a long period of time for a person to be at risk. There are no health risks associated with other uses of the lake, such as swimming, boating or waterskiing.
"This is not an immediate health threat," Scholl said.
It does, however, create another obstacle for the Utah Department of Natural Resources, which is trying to remove carp from Utah Lake.
There are an estimated 7.5 million carp in Utah Lake, accounting for 90 percent of its volume of fish, said Reed Harris, DNR recovery programs director.
Carp are bottom-feeders that get down in the sediments, churn around in the mud and make the lake turbid, Harris said.
"They basically make it so it's a better environment for them to the exclusion of all other fishes," he said.
Among those at risk is the June sucker, a rare fish native to Utah Lake that has been on the federal endangered species list since 1986.
The PCB levels were detected as part of the DNR's June Sucker Recovery Implementation Program. Officials are trying to determine whether carp are fit for use as animal feed, fertilizers or biofuels.
"It's another factor we'll consider when we're looking at how we potentially market (the carp)," Harris said.
Carp and other fish will be collected and analyzed throughout the summer, he said.
In addition, the Department of Environmental Quality will be conducting follow-up work to attempt to identify the PCB sources and the extent of the contamination."Typically, PCBs are in the sediments, not in the water column," Whitehead said. "We need to figure out where these are coming from and if there needs to be some sort of a cleanup."
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