A metal that is highly toxic to the nervous system at very low levels of exposure. Mercury is one of the world’s most common industrial pollutants and is a particular problem when it settles to the bottom of waterways (including the ocean). Some people experience health problems related to mercury through occupational exposure, but most mercury exposure occurs through eating of contaminated fish. According to the U.S. Food and Drug Administration’s Center for Food Safety and Applied Nutrition (FDA CFSAN), fish with the highest mercury contamination levels are large long-lived species including tilefish, swordfish, king mackerel, and shark. The fish most commonly eaten in the United States tuna, pollock, halibut, grouper, and shellfish typically have low levels of mercury. Although debate continues about the safety of mercury in dental fillings, most health experts believe the level of mercury in dental amalgams is too low to have adverse health effects.
Mercury poisoning causes neurological damage that can include numbness and problems with vision and hearing and has been investigated as a potential cause of Parkinson’s disease. Some genetic mutations that interfere with the body’s processing of metals such as iron do cause Parkin-son’s-like diseases. However, these diseases are progressive and neurodegenerative, as is idio-pathic Parkinson’s, whereas the neurological symptoms of mercury poisoning are usually temporary and subside as the body clears itself of excess mercury. As well, they differ from the classic symptoms of Parkinson’s. Research continues to investigate the role mercury exposure, as well as exposure to other environmental contaminants, may play in Parkinson’s disease, but at present it seems an unlikely cause.