People who eat a lot of fish from Lake Michigan are less contaminated with PCBs and DDT because they are eating fewer of the most contaminated fatty fish, according to research by the Wisconsin Department of Natural Resources.

Environmental Health News reports that sport fisherman and boat captains who consume large quantities of Great Lakes fish had 33 percent less polychlorinated biphenyls (PCBs) in their blood than they did when tested nine years earlier. Blood levels of the pesticide DDT, which was banned in the 70s but is still present in the environment, declined by 43 percent in the same period. 

PCBs — industrial chemicals used in electrical equipment and banned in 1976 — are carcinogenic and cause brain damage to children exposed in the womb.

Candy Schrank, an environmental toxicologist at the Wisconsin Department of Natural Resources, told Environmental Health News that a change in fish consumption was key in reducing the contamination.

“They moved from eating lake trout in the earlier years, which are a fattier, more polluted fish and switched to cleaner fish.”

Cleaner fish include salmon and perch.