Methylmercury is a metal found in nearly all fish in lakes, rivers and oceans, reports the Office of Environmental Health Hazard Assessment. Health (OEHHA) advisories are issued in certain areas where the risk for mercury exposure is greatest. Following certain guidelines and being informed of mercury is the best way to prevent poisoning.
Sources
Mercury is found throughout nature in soil, rocks and sediment deposits all over the world. Thermal springs and volcanoes contain high levels of the mineral. The U.S. Geological Survey (USGS) reports that mercury contamination in oceans may be the result of human activities, such as mercury mining and processing and incineration of coal, medical and other waste products. Mercury levels can circulate for many years after it has been released into the air, land or water. Once in the ocean, mercury can settle on the bottom of the sea and be consumed by bacteria. Mercury levels in fish are elevated when the fish consume bacteria or other fish that have been exposed to the toxic metal, according to the OEHHA.
Geography
Toxic mercury levels in fish are profound enough to cause fish consumption warnings and advisories across the United States. Mercury can be found in almost all fish, but certain areas are at higher risk. The USGS reports that 40 states in the U.S. have health advisories for mercury contamination in rivers and lakes. States along the coast, such as Texas, Florida, North Carolina and Maine, also advise residents of mercury toxicity in fish.
Health Effects
Mercury can accumulate within the body over time and lead to harmful effects on the central nervous system. Loss of coordination, blindness, hearing loss and speech impairment are some of the side effects of mercury toxicity reported by the OEHHA. Mercury poisoning is rare, and it only occurs through heavy consumption of fish that contain high amounts of the metal. Children are more sensitive to mercury poisoning from fish because their central nervous systems are not fully developed. Other side effects of mercury exposure include tingling in the body, and problems with the kidneys and heart.
Fish Consumption
Nearly all types of fish contain mercury. The Environmental Protection Agency (EPA) reports that regular consumption of fish is not a health concern, but it is necessary to understand the risks. Women who wish to become pregnant or currently are pregnant are advised to avoid certain types of fish with higher traces of mercury. The EPA recommends avoiding fish that contain the highest concentrations of mercury, like swordfish, shark, tilefish and king mackerel. Fish with lower traces of mercury are shrimp, tuna, salmon and catfish, and can be safely consumed twice a week. Checking local fish safety advisories for the latest report is the best way to stay informed.
Mercury Testing
The OEHHA recommends following its tips for safe fish consumption to reduce exposure and prevent mercury poisoning. Mercury levels in the body can diminish over time if mercury exposure is reduced or ceased. Mercury exposure from fish consumption can be tested by medical procedures that collect, prepare and analyze blood and hair samples. Seek medical advice from a specialized physician if you're interested in getting tested.
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