In New York State winds deposit mercury from the coal-fired power plants of the Midwest, contaminating the waters of the Catskill Mountains. Mercury is concentrated up the food chain, as it is converted into methylmercury, a toxic compound which harms both wildlife and people who consume freshwater fish. The mercury is consumed by worms, which are eaten by fish, which are eaten by birds (including bald eagles). As of 2008, mercury levels in bald eagles in the Catskills had reached new heights. People are exposed to methylmercury almost entirely by eating contaminated fish and wildlife that are at the top of aquatic food chains. Ocean fish account for the majority of human exposure to methylmercury; the full range of sources of methylmercury in ocean fish is not well understood.