Air Date: Week of October 31, 1997

Steve Curwood talks with Michael Gilbertson, a biologist with the International Joint Commission which oversees Great Lakes cleanup. on the 25th anniversary of the joint U.S. - Canadian agreement to clean up the Great Lakes. Lakes Michigan, Erie, Ontario, Superior, and Huron together hold one fifth of the world's fresh water and Gilbertson says one of the most intriguing new findings concerns trout in Lake Ontario.

Transcript

CURWOOD: It's Living on Earth. I'm Steve Curwood. It's been 25 years since the US and Canada signed an agreement to clean up the Great Lakes. The lakes, which together form the world's largest body of fresh water, have become badly polluted by industry, farms, and cities. Today, the Great Lakes are cleaner, thanks to better farming practices and improved sewage treatment, but a huge problem remains. How to deal with tons of persistent toxic chemicals, including DDT, PCBs, and dioxins, that lie in lake sediments, and leak from shoreline landfills. Michael Gilbertson is a biologist for the commission which oversees the Great Lakes cleanup. He says, new research indicates the pollution must share the blame with overfishing for the collapse of fishing stocks.

GILBERTSON: There have been two sets of studies which have been done, particularly by Dr. Phillip Cook, and Dr. Richard Petersen. Dick Petersen has been looking at the toxicity of dioxins to lake trout, and what he's found is that, if you get 100 parts per trillion, that's a minute amount of dioxins in the eggs of lake trout, none of them will hatch out. The other kind of research is by Dr. Phillip Cook, in which he's gone and taken a large sediment core from Lake Ontario, and what he's done is, to find out when each of the different layers of sediment was laid down, and then he's gone and found out, "Ok, how much dioxin was there in each of those different layers." So he knows how much dioxin was being put into Lake Ontario.

CURWOOD: Ah, hah. Now, what happens when you compare these two sets of data?

GILBERTSON: Well, when you bring the information together, I think the shocking thing was, that, by 1940, the amounts of dioxin in Lake Ontario, was high enough, that none of the lake trout could have hatched out after that period of time.

CURWOOD: 1940?!

GILBERTSON: 1940, yes. And, of course, the lake trout went extinct, in Lake Ontario, by the early 1950s.

CURWOOD: Now, last summer the US Agency for Toxic Substances and Disease Registry issued a new report saying that fish can be harmful, fish in the Great Lakes, especially to fetuses of mothers who consume fish. Now what's the significance of this report?

GILBERTSON: The significance of this report is, that one of the, US senior health agencies, has now made a definitive statement about the effects that are occurring, on reproduction and on the development of infants, who have been actually exposed to these chemicals. I think these are quite different statements from the kinds of statements which have been made in the past, where the agencies were talking about the potential effects, which might occur, if people were exposed to them. And it's taken a long period of time, but what we now understand is, just how certain we are, that these kinds of chemicals are having effects on humans in the functional development, the development of the neurological system, the behavioral systems, the systems for learning.

CURWOOD: So, eating fish from the Great Lakes is a risky proposition?

GILBERTSON: Well, the situation is, that people who are eating larger quantities of these fish, are exposing themselves to higher concentrations of these chemicals--they go and store them in their bodies--and if they are of reproductive age, then their fetuses will be exposed to these kinds of chemicals.

CURWOOD: Well, I want to thank you for taking this time with us today.

GILBERTSON: Thanks very much.

CURWOOD: Michael Gilbertson is a biologist with the International Joint Commission.