Mercury Pollution

! Mercury emitted from power plant stacks and other sources is carried by winds through the air and eventually is deposited to water and land. Mercury can be deposited locally, or it can travel great distances – depending on the form in which it is emitted, the height at which it is released and atmospheric conditions.

! Mercury concentrations in the air are usually low and of little direct concern. However, once mercury enters water – either directly or through deposition from the air – biological processes transform it into methyl mercury, a highly toxic form of mercury that bioaccumulates in fish and other animals that eat fish. When a substance bioaccumulates, its concentration increases as it moves through the food chain.

! Human exposure to mercury occurs primarily through consumption of contaminated saltwater or freshwater fish. Mercury contamination in large, predatory fish can be thousands of times higher than concentrations in the water.

! At high doses, mercury exposure can cause tremors, inability to walk, convulsions – and even death. At levels more commonly seen in the United States, documented mercury exposure effects include more subtle – yet still serious – damage to the senses and brain.

! Women of childbearing age and people who regularly and frequently eat highly contaminated fish (or large amounts of moderately contaminated fish) are the most likely to be at risk from mercury exposure. Those groups include subsistence fishermen and some Native American populations.

! The developing fetus is the most sensitive to the effects of mercury, because its brain is developing rapidly; therefore women of childbearing age are at the greatest risk. Children of women exposed to relatively high levels of methyl mercury during pregnancy have exhibited a variety of abnormalities, including delayed onset of walking and talking, cerebral palsy and reduced neurological test scores. Children exposed to far lower levels of methyl mercury in the womb have exhibited delays and deficits in learning ability. In addition, children exposed after birth potentially are more sensitive to the toxic effects of methyl mercury than adults, because their nervous systems are still developing.