Environmentalists who’ve been warning for years that mercury levels in the Detroit River were rising say their concerns have been confirmed by several recent studies.
"We’re seeing more of an increasing trend rather than a constant or decreasing trend," reports Russell Kreis, director of the U.S. Environmental Protection Agency’s research station on Grosse Ile.
Tests of both fish and sediments, as well as "loading" estimation studies examining the amounts of mercury going into the river, all indicate that mercury levels are indeed increasing.
A toxic heavy metal, mercury can cause damage to the human nervous system, particularly for young children and fetuses. Kreis says mercury levels as high as 16 parts per million are being detected in river sediment. Levels greater than 0.2 ppm are known to harm aquatic life.
Officials at the Michigan Department of Environmental Quality don’t dispute Kreis’ findings, but they disagree with the contention made by environmentalists that the increase results from the continued dumping of mercury into the river by industrial and municipal sources. Bob Sweet, an aquatic biologist for DEQ, says that the increased levels found in recent studies are primarily the result of previous contamination moving within the water system.
"We believe it is from the resuspension of sediments," says Sweet of the increase. "Historically, the inputs from mercury are much higher than they are today. The mercury is moving downstream from throughout the system."
Many environmentalists disagree with that analysis. They point with concern to a new permit for the Detroit wastewater treatment plant that in 1997 increased the allowable detection limit from .006 parts per billion to .018 parts per billion. The increase was granted, says Sweet, because the metal could not be detected at levels below .018 ppb.
That view is not held by others. Saul Simoliunas, a chemist at the wastewater plant and an outspoken critic of Detroit River cleanup efforts, says that mercury can be detected down to parts per trillion.
"They are obfuscating," says Simoliunas about the DEQ.
Although the amounts sound infinitesimal, when put into the context of up to 750 million gallons of wastewater being pumped through the treatment plant each day, even microscopic levels of mercury can have a tremendous impact, says Kreis. He adds that because the metal accumulates as it moves up the food chain, it is one of the leading factors contributing to advisories prohibiting the consumption of Great Lakes-area fish.
Whether the mercury is rising because of new input or past pollution is important because government officials are contemplating a dredging project to clean up "hot spots" in the Trenton Channel near Grosse Ile.
The expensive undertaking will be a wasted effort if new mercury will be an ongoing problem, say critics.
The dispute is long-standing. In 1994, the Citizens Environment Alliance of Southwest Ontario (now the CEA of Southwest Ontario and Southeast Michigan) used State of Michigan data to report that mercury discharged from the Detroit treatment plant had increased 78 percent over a 10-year period. State officials "explained the increase as an ‘accounting error,’" recalls Grosse Ile resident and CEA member Mary Ginnebaugh.
The way she sees it, the EPA’s recent findings support what environmentalists have been saying since the early 1990s. "We think we’ve gained credibility here," says Ginnebaugh.
