In the best-case scenario, we’ll be able to eat all the Lake Michigan lake trout we want without worrying about getting cancer from the PCBs — in another 20 years.
Less optimistically, we might have to wait until 2046.
Those are the predictions of U.S. Environmental Protection Agency researchers, who have modeled how long it will take for Lake Michigan to get rid of its PCBs (aka polychlorinated biphenyls) — those persistent, toxic compounds that accumulate in fish and people and, as the report says, “have been consistently identified as the contaminant of greatest concern to human and ecosystem health in the Great Lakes.”
Right now, we’re not supposed to eat more than one meal a month of lake trout — assuming we stick to the smaller fish, and trim away the PCB-laden fatty tissues and skin.
Monsanto Co. produced 700,000 tons of PCBs from 1929 until 1977, according to the EPA. They were used to insulate and cool electrical equipment. Banned in the U.S. in 1979, they’re still around: In Lake Michigan, air and watershed tributaries continue to bring PCBs into Lake Michigan, according to the EPA, and the pollutant hangs around in the lake’s sediment.
Researchers found the main way PCBs get into or leave the lake nowadays is by volatilizing, getting into the air. Once airborne, they travel downwind until they’re deposited on land or water elsewhere. (Figure at this link on page 433.)
Wisconsin Department of Natural Resources advises us which fish not to eat and where in its full Fish Consumption Guide (warning: big PDF, and potentially frightening for avid piscivores). We weren’t talking about mercury in this post — the other reason to avoid Wisconsin fish — but this guide sure does.
Lake Michigan Mass Balance Study (also EPA)