Fish Consumption Health Advisories

Methylmercury is an organic form of mercury that can accumulate in fish to levels that may be toxic to humans who eat them regularly over a prolonged period of time. The species of fish most susceptible to this accumulation of methylmercury are those that feed primarily on other fish such as largemouth bass. This is a problem in many areas of Florida and in many other areas throughout the United States and the world.

The level of mercury in an individual fish depends upon its age and diet. Older, larger fish usually contain more mercury than younger, smaller fish from the same water. The amount of mercury in a fish’s diet depends upon what it eats and the water it lives in. Most of the mercury to which fish are exposed is deposited from the atmosphere by air currents and rain. Municipal incinerators, medical waste incinerators, the combustion of fossil fuels, mining and smelting are the principal sources of atmospheric mercury. These sources may be nearby or on the other side of the earth. Efforts are under way to control Florida sources. Whether mercury from the atmosphere will be incorporated into the diet of the fish you catch depends mainly upon water quality. DEP is working to understand the environmental factors that determine fish mercury levels and how those levels can be reduced.

Mercury is a naturally occurring element for which human beings are believed to have some tolerance. Tolerances are established by the Florida Department of Health (DOH). Fish that have more than 1.5 parts per million in the edible flesh are considered unsafe for any consumption. Consumption should be limited for fish with concentrations from 0.2 to 1.5 parts per million of mercury in edible flesh. These values are based on a body weight of 156 lbs and an 8 ounce (half-pound) serving of fish. Consumption limits are less for women of childbearing age and children. DOH has consumption guidelines for all populations on their website. This site lists those waters where fish likely to be consumed by humans have been tested. It shows which waters tested safe for limited consumption and which are unsafe for any consumption. The complete texts of Department of Health advisories are also given.