28 August 2009
Toxins in Lake Michigan fish linked to diabetes
This is a fish tale in which smaller is better than bigger, especially if the catch is to be eaten in any quantity.
That's because a new study of Great Lakes boat captains over 15 years found a correlation between the chemical DDE and diabetes. Those who ate more fish had more DDE in their blood and were more likely to develop diabetes, according to results published in the journal Environmental Health Perspectives in July.
DDE is produced in the bodies of small bottom-feeding fish from ingesting the prevalent pesticide DDT. The chemical transfers to bigger fish when they eat smaller fish and then accumulates in the fat and liver of people who eat lots of what they catch.
"Sports fishermen are at the top of the food chain," said Bruce Fowler, assistant director of science at the Agency for Toxic Substances and Disease Registry at the Centers for Disease Control and Prevention, which funded the study, along with the federal Environmental Protection Agency.
Charter boat captains tend to catch and eat more fish than the average recreational fisherman. But the captains care about their health, said Henry Anderson of the Wisconsin Division of Public Health, who managed the study.
"Many saw that their levels were high from the study and they cut back on their intake of fish," he said.
Exactly how DDE may lead to diabetes is unknown. Another pesticide, Agent Orange, can cause diabetes, but it's believed to do so in a different way than DDE, said Mary Turyk, an assistant professor at the University of Illinois at Chicago and lead author of the study.
DDE is a byproduct of the pesticide DTT, which was used in farming in the Great Lakes region. It was banned in the United States 37 years ago but continues to be a worrisome pollutant because it is used in other countries to combat malaria and because it remains in the lakes due to the slow turnover of water.
"DDT gets thrown up in the atmosphere and can be deposited by rain and snow attached to particles which settle at the bottom of the lakes," Fowler said. "The toxins are released by Asia and settle in North America. The jet stream carries a lot of things besides temperature and rain."
There is reason for hope, scientists say.
"The good news is that levels in fish and in people have been going down because we have been cleaning up the lakes," Anderson said.
Fisherman Todd Panagopalores, who often can be found at Northerly Island, said he and others worry about what they eat and keep only the smaller fish because they know the bigger fish accumulate the most harmful toxins. That advice is contained in guidelines from the Illinois Department of Public Health fish advisory, which are based on a monitoring program that test for 14 environmental chemicals in fish.
The advisory sets limits of fish consumption based on levels of PCBs, which can cause cancer, and mercury, which causes nerve damage and birth defects. Though tests for DDE are included, they do not contribute to the advisory because the levels found in local fish do not exceed health-based guidelines, said Ken Runkle, senior environmental toxicologist from the Illinois Department of Public Health.
Anderson said existing advisories are adequate, even given the possible DDE link to diabetes.
"The point is not to discourage people from eating fish but to be selective. If you eat a balanced source of fish, you will not run into problems with the fish advisory," Runkle said. He suggests eating different types of fish from different water sources.
"When properly prepared, fish are high in protein and low in saturated fats and part of a balanced diet," he said.
Researchers discount that mercury might have been the culprit of diabetes in their study, because mercury and DDE do not travel together. Mercury is found in fish muscle, whereas DDE and PCBs accumulate in the fat and skin. Trimming the fish's belly fat before cooking it and allowing the fat to drip off during cooking can reduce intake of the toxins, advises the Web site for the Illinois Department of Public Health.
An earlier study measured chemicals in 8,000 people across the U.S. to see whether pollutants were linked to diabetes. "Basically, it looked like a relationship between chemicals and diabetes, but they couldn't say which chemical was the toxic one," said Fowler. "This new research carries this one step further and points the finger at DDT as the primary agent."
Chris Taglieri, who fishes every morning for carp in the same spot at Northerly Island before he heads to work as a Chicago police officer, doubts the research will change fishermen's eating habits. He tosses back what he catches.
"There are other things with larger implications to be worried about," Taglieri said. "I think you should be more concerned with what's in a can of tuna than a fish that you catch."