Transcript: Gabriel Spitzer, August 17, 2009
Scientists have known for a long time that a lot of wild-caught fish have dangerous contaminants. People who eat fish have to weigh the health benefits against the risks of consuming those pollutants. Now, some research could make that balancing act even trickier. Gabriel Spitzer has more on the link between diabetes... and an infamous old chemical many assumed was long gone:
In the early morning hours, anglers gather on Navy Pier in downtown Chicago.
Ray Penn is practically within casting distance of the city's skyscrapers.
He dips his line in the waters of Lake Michigan, hoping to pull out something tasty.
"I filet 'em, and I fry 'em, yeah. They got a little bit of bones in 'em, but - oh yeah. Oh, yeah, baby! I felt that!"
It's looking like a good morning for rock bass.
"See, there's a bass on the end of this. This is a small bass, now this guy here, he's edible."
Penn says he eats fish a couple of times a week, without giving it a second thought.
Down the pier, Patrick Duhan has the same attitude.
"This is the Great Lakes! It's such a big body of water. It's almost like the ocean. They throw tons of crap in the ocean, and there's just too much of it to screw up."
But, scientists say, people have managed to screw up the Lakes a fair amount.
Epidemiologists have been studying a group of sport fishers, like these guys, and charter boat captains, who eat a lot of Great Lakes fish.
Mary Turyk of the University of Illinois at Chicago measured the contaminants in their blood, and tracked their health over the years.
"We found we had 36 cases of new diabetes. And what we found was that DDE, the metabolite of DDT, was related to diabetes incidence."
That's the pesticide made famous by Rachel Carson's book, "Silent Spring."
The chemical was banned in 1972, but traces of it are still all over the place - including in fish.
And like mercury or PCBs, it concentrates as it moves up the food chain.
So you don't have to eat much.
"The captains were eating, I think, on average, a meal a week. One meal a week? Yeah. That doesn't seem outlandish or anything. No, it doesn't. It doesn't at all. In fact, recommendations from the FDA for eating fish, based on mercury levels, are two meals per week, for pregnant women."
So just half that much fish was linked to about a 33% increase in diabetes cases.
Turyk says it's not clear how DDE or DDT might contribute to diabetes.
It may have to do with effects on hormones or the immune system.
"We really need more basic science to determine mechanisms that might be responsible for this."
Another unknown is just how dangerous might this be, and when does it start to outweigh the advantages of an otherwise healthy food?
Tamara Duperval is a family doctor at a West Side Chicago clinic.
She says she still tells people to eat more fish.
"In our population, it's really a wonder and a challenge to try to present fish as an option, when primarily the staple of diet is either chicken or beef."
That population is mostly low-income and minority.
She says about half are overweight or obese.
From a nutrition point of view, those are exactly the people you'd want to be eating a lean, healthy protein like fish.
So Duperval is concerned about sending mixed messages.
"I do think it is confusing. And, it's in part, I think, how we communicate crisis in this country, especially when it comes to food safety. They miss the overall preventative message, that fish is good food, and it actually provides a lot of important nutrients that are lacking in their diets."
Health authorities often issue advisories about certain fish that have a lot of pollution.
Duperval says understanding those warnings can help people avoid some of the hazards.
But the diabetes research shows we may still have a lot to learn about these chemicals, so what's safe to eat is getting harder to know.
For The Environment Report, I'm Gabriel Spitzer.
Copyright © 2009. The Regents of the University Of Michigan. Used with permission.