The majority of mercury in the air is present as elemental mercury, not methylmercury. In fact,
approximately 98% of atmospheric mercury is elemental mercury. While elemental mercury is
one of the less toxic forms of mercury, it can be converted to methylmercury once it is deposited
onto the landscape. The conversion of mercury to methylmercury is actually done by bacteria,
and often occurs in areas where there is not much oxygen (for example, lake bottoms, areas
where the tundra is saturated with water, and wetlands). Once methylmercury is formed it is
easily absorbed into the muscle tissue of fish, wildlife, and humans. Methylmercury can also