Severe mercury contamination in California's water bodies is largely a legacy of historic gold and other mining. It is estimated that 10 to 30% of the 220 million pounds of mercury mined in California, particularly from the Sierra Nevada and Klamath-Trinity Mountains, was lost to the environment. Much of this mercury has since washed into the heavily-populated San Francisco Bay-Delta Estuary. Dischargers such as Bay Area oil refineries also continue to release additional mercury into the environment. Once in the environment, mercury converts to toxic methyl mercury and accumulates in organisms that are eaten by fish. As all animals accumulate mercury faster than they release it, this allows concentrations to reach dangerous levels in fish and birds at the top of the food chain. A recent study highlights the severity of mercury contamination in Bay Area fish. Mercury is a potent neurotoxin, especially dangerous to developing fetuses and young children, putting subsistence fishers particularly at risk.
Selected maps: Back to All Impaired Waterbodies | Nutrient Pollution | Bacteria Pollution | Sediment Pollution
