The toxaphene mysteries - a source of pollution in the once Great Lakes

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The toxaphene mysteries

The pesticide toxaphene was banned in the early 1980s because it damages

kidneys, the lungs and the immune system, causes birth defects, and may be a

carcinogen. It has been spread through the atmosphere, and is now the most

ubiquitous of contaminants. It has even been found in water under the polar

ice cap. Environmental researchers have been puzzled because its

concentrations have not declined in Lake Superior fish but they have

declined in fish from the other Great Lakes. And its concentration is higher

in sediment cores from northern Lake Michigan than in the southern end.

Those anomalies have inspired additional research, including studies to

determine whether it is or was an inadvertant result of pulp and paper mills

manufacturing, or whether its past as an agricultural pesticide continues to

haunt the Great Lakes.

In Lake Superior fish

Toxaphene becomes more concentrated as it moves up the food chain from water

and zooplankton to lake trout. A comparison of fish taken from several of

the Great Lakes showed that between 1982, the year it was banned, and 1994,

toxaphene levels in lake trout in Lake Superior remained the same, but

declined sharply in trout from lakes Michigan, Huron and Ontario.

Micrograms per gram 1982 1992-94

Lake Superior 4.9 4.9

Lake Michigan 5.0 1.5

Lake Huron 5.2 2.4

Lake Ontario 4.6 0.5

In Lake Michigan sediment

Lake sediment cores, like tree rings, can track historic patterns. A study

of cores taken from the mud in two spots from Lake Michigan show that in the

north, toxaphene concentrations were historically much higher and have

declined less than in the levels in a core taken in the southern end of the

lake. But two samples taken within a few feet of one another in the northern

end show different levels of toxaphene, prompting further sediment research

which has not yet been completed.

(See microfilm for chart.)

Near the paper mills

Toxaphene is made by adding chlorine, or bleach, to pine resin. And that has

raised the question of whether paper and pulp mills, which bleach paper, may

be inadvertently making toxaphene. The Environmental Protection Agency (EPA)

has funded a study to determine whether sediment core samples taken both up

river and down river from paper mills sites show different levels of

toxaphene.

A toxic legacy

The EPA also has funded research, again by studying sediment core samples,

to determine if past agricultural use of toxaphene is continuing to leach

into rivers and flow to the Great Lakes. Results are not expected until

later this year.

Source: Environmental Science & Technology; Environmental Protection Agency;

University of Minnesota.

Maura Lerner; Staff Writer, Mystery inquiry targets scientist // Deborah

Swackhamer, a researcher studying a toxin in the Great Lakes, has discovered

that the search for data can occur on many levels.., Minneapolis Star

Tribune, 05-17-1998, pp 01A.