Check with your state Department of Public Health before eating fish from local waters. Warnings can be very different from region to region, based on local industries' polluting specific water sources. Most advisories involve five primary contaminants: mercury, PCBs, chlordane, dioxins, and DDT. These chemical contaminants persist for long periods in sediments, where bottom-dwelling animals accumulate them and pass them up the food chain to fish. Levels of these contaminants may increase as they move up the food chain, so top predators in a food chain, such as largemouth bass or pike, may have levels a million times as high as that in the water.
Mercury, PCBs, chlordane, dioxins, and DDT were at least partly responsible for 96 percent of all fish consumption advisories in effect in 2002. In 2002, nineteen states issued statewide advisories for mercury in freshwater lakes and/or rivers. Another eleven states issued statewide advisories for mercury in their coastal waters. Thirty-eight states issued PCB advisories and four states added nine new PCB advisories in 2002. The number of dioxin advisories is small compared to the other four major contaminants'. But although its use has been banned since 1975, the number of advisories currently in effect for DDT continues to increase.
Some fish and shellfish are a significant source of purines. Since purines can be broken down to form uric acid, excess accumulation of purines in the body can lead to excess accumulation of uric acid. Gout and the formation of kidney stones from uric acid are two examples of uric acid-related problems that can be caused by excessive intake of purine-containing foods. For this reason, individuals with kidney problems or gout should avoid or limit their intake of fish and shellfish.