By SARAH COEFIELD
Capital News Service
LANSING — Bob Barnes doesn’t worry about contaminants when he drops a line into his favorite fishing hole.
In the early morning when the walleye come in droves to pick off schooling bait fish, he’s at the spot where the South Channel dumps into Lake St. Clair.
Barnes, an engineer from Sterling Heights, and vice president of the Lake St. Clair Walleye Association, knows the lake’s history. He knows about the mercury and PCBs. He knows he’s supposed to limit the number of fish he eats.
He just doesn’t much care.
Research shows that methyl mercury inhibits brain development. PCBs can suppress the immune system and thyroid development. They may also cause cancer.
But Barnes doesn’t think about that. He thinks about the fish.
Lake St. Clair, he says, “is a great fishery. It’s fantastic.”
But that fishery has a murky past.
In 1970, the Canadian government banned commercial fishing in Lake St. Clair because chemical plants and petroleum refineries on the St. Clair River had released so much mercury into the water that fish were unsafe to eat.
When the fishery reopened 10 years later, officials retained warnings against eating mercury-contaminated fish.
Thirty years later, consumption advisories are just part of the reality when fishing the lake.
And that won’t change any time soon, according to a recent study.
Mercury and PCB levels in fish dropped dramatically between the 1970s and 1990s but leveled off in the past decade, said Sarah Gewurtz, a postdoctoral fellow in the department of ecology and evolutionary biology at the University of Toronto.
Gewurtz was part of a research team that analyzed fish contamination data collected by the Ontario Ministry of the Environment since the 1970s.
Fish contaminants dropped rapidly when polluters closed and dredging removed toxic hotspots, the study shows.
But now the contaminants are coming from the sediment itself, Gewurtz said.
The contaminated lake bottom is the legacy of decades of pollution, she said, with little prospect for rapid improvement. “Unless the whole system is dredged, which is not feasible, it can be hypothesized that the sediment will continue to be a source to the fish.”
Enough mercury and PCBs are released from the sediment to limit fish consumption for the foreseeable future, Gewurtz says.
There are mercury-based advisories for two of the lake’s most popular sport fish: walleye and yellow perch. PCBs are a concern in carp, but studies show that St. Clair area anglers aren’t much interested in catching them.
Both contaminants build up in fish over time – mercury in the muscle and PCBs in the fat. Older fish and fish higher up the food chain are the most contaminated.
The U.S. and Canadian governments recommend children under 15 and women of child-bearing age restrict themselves to small fish, and even then eat the popular sport fish only one to four times each month. The general population can eat more fish, but should still avoid large ones.
While PCBs slowly degrade, mercury stays in the system until it’s covered by a new layer of sediment – hardly a quick process. “It could certainly be on the order of decades,” said Alexis Cain, an environmental specialist with the U.S. Environmental Protection Agency regional office in Chicago.
Still, Cain said the mercury levels are improving, even if the fish testing suggests otherwise.
“We’re confident that putting less mercury into the system is a good thing and eventually will result in declined concentrations in fish,” he said. “The way mercury circulates in the environment, even if releases go down, it may not show up in the fish.”
And while natural sedimentation takes care of the lake bottom, additional dredging is planned to clean up three more areas on the St. Clair River.
Claude Lafrance, who coordinates cleanup of the river for Ontario, said, “We expect that once these areas are remediated this will further reduce available contaminants and contribute to reducing fish contamination.
Plans for managing those areas are underway, and any remediation will begin in 2011, he said.
Meanwhile, Barnes keeps fishing and eating what he catches.
Barnes usually eats fish at least once a week but trims fat from his catch and generally sticks to small and mid-size fish to limit risk of contaminant exposure.
It’s enough, he figures, to keep him safe in the pastime he loves.
“Maybe I’ve lulled myself into a false sense of security, but I believe it to be safe,” he says
Sarah Coefield writes for Great Lakes Echo
© 2010, Capital News Service, Michigan State University School of Journalism. Not to be reproduced without permission.