Most man-made mercury pollution is emitted by coal power plants, but mercury can also be a byproduct of gold mining, cement production, iron and steel production and waste disposal. Once in the environment, mercury can accumulate in the soil, water and atmosphere. It is particularly apparent in the marine food chain. The consumption of fish is by far the most significant source of mercury contamination in humans. Some effects of mercury poisoning include impaired cognitive function, kidney failure, loss of hair, teeth or nails, and extreme muscle weakness.