Mercury pollution is a global problem because mercury can travel short, but also very long distances in the air from where it was first released. Although mercury is released from natural sources, like volcanic eruptions and deep-sea hydrothermal vents, it has become a global pollutant because of things we do as humans. Especially things like using coal to generate electricity, using mercury for gold mining, and a lot of other industrial applications.
In New York State, mercury comes primarily from our reliance since the 1840s on coal combustion to generate electricity. Coal contains mercury that gets released into the atmosphere when it is burned. Then it falls back down on the earth through wet or dry deposition (what scientists call rain, snow, fog, and gases or particles that fall out from the air). The expert on mercury deposition in New York State is Gregory Lampman at NYSERDA. He’s written a lot about it, and you can read his reports online here (report 13-23 is the one about mercury deposition).
Even though we know a lot about mercury in the environment from decades of research, we still don’t know enough. In New York State, there are a lot of regions, including the Finger Lakes, that have very little data on mercury in fish and other wildlife. This data is needed to be able to see how limits on mercury emissions change how much mercury ends up in the environment, and ultimately us. New York is taking a lead on protecting human and ecosystem health with the Mercury and Air Toxics Standards in New York, a program that will limit the mercury that is released from power plants. In the long run, these standards will save us a lot of money by protecting our health.