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Development of stricter safety standards has prompted state authorities to issue a health advisory on eating fish from many of Indiana's lakes and rivers.
However, Kosciusko County health officials caution that the study for local lakes was based on fish tested in the late 1980s and should not be a cause for alarm.
"We just want people to keep things in perspective," said Kosciusko County health administrator Jon Cupp.
According to the study results issued by the Indiana Department of Natural Resources, contamination from mercury and polychlorinated biphenyls (PCBs) was detected in fish tissue samples (see box for a complete list of lakes and consumption guidelines).
Cupp said the advisory includes most streams and many lakes in the state. He said the state added mercury to its list of contaminants when it tightened the standards, and that authorities also are assuming that people eat more fish out of the lakes than they did previously.
PCBs are usually found in urban areas and tend to come from old transformers, Cupp said. While mercury contamination may be a result of industrial pollution, many times mercury is naturally occurring in lakes, he said.
Center and Winona lakes were reported to have PCB contamination; fish from Pike, Tippecanoe and Waubee lakes were found to contain mercury and not PCBs. From Lake Wawasee, black bullhead were reported to contain PCBs, and largemouth bass to contain mercury.
Larger fish are assumed to contain higher levels of contamination because they have been exposed to chemicals longer and accumulate chemicals present in the food chain, the DNR said.
However, the study also noted that the lakes appear to be cleaner now than they were 20 years ago, and that it may be a greater risk for some individuals to take fish completely out of their diets than to eat the fish mentioned in the study.
Bob Weaver, epidemiologist for the Kosciusko County health department, said mercury builds up in the muscle of the fish, "the part you eat." PCBs, however, collect in the fat, so the risk of consuming PCBs can be reduced by trimming the fat from the fish.
The Indiana Department of Health also recommends keeping only the small fish, eating smaller meals and eating less contaminated kinds of fish. Cooking guidelines include preparing a boneless, skinless fillet for cooking. Broiling, baking or grilling fish so the fat drips away also will reduce PCB levels. Since mercury is bound to the meat in a fish, these precautions will not reduce the amount of mercury consumed.
Cupp said state authorities advised that if a lake is not listed as having been tested, it should be assumed to be a Group 2 lake (see box).
Contaminated fish usually do not smell, taste or look different, DNR reports said, and anglers should rely on the study for advice on which fish to eat or to avoid.
Cupp said testing in the past was done on a complaint-inquiry basis, and warnings for some of the lakes included in the most recent advisory are based on testing of fewer than a dozen fish.
He also emphasized that anyone with questions on specific fish should not bring fish in to the health department for testing. However, the department will have copies of the complete study available for public inspection.
