Mercury is in the Air

The last thing anyone has wanted to think about is mercury air pollution, but now that the United States government has moved ahead to start control of mercury air emissions from power plants, it is a subject getting attention from the press. Mercury is now on center stage because the Environmental Protection Agency unveiled a rule last week to limit mercury emissions from U.S. power plants. On one side it is being hailed as groundbreaking, in that it is one of the first major attempts at controlling mercury emissions. The world is 510 million square kilometers and 71 percent of that is ocean. One gram of mercury poured into eighty million liters of water would be cause for concern under federal human health standards for drinking water, enough to contaminate a typical mid-western lake. Thus one gram pollutes a typical 20 acre lake and 20 acres equals .081 square kilometers.

One ton of mercury contains 1 million grams which would thus pollute 81,000 square kilometers of lakes. One thousand tons would pollute 81 million square kilometers, so 7,000 tons of mercury would pollute a lake the size of the world. The world is not a lake, so the one gram rule does not quite work, but it offers us a good reference point. The oceans are quite deep and the atmosphere also holds a vast capacity to hold mercury, as does the soil. But over the last five hundred years we have dug up and used approximately 1 million tons of mercury.[ii] That is 1,000,000,000,000 grams (a trillion) or enough to blanket each 20 acres on earth with over 149 grams. It is these 149 grams that is responsible for mercury levels increasing by a factor of 20 times over the last 3 centuries. The new standard will not adequately protect Delawareans or the rest of the country from a potent neurotoxin that EPA had determined to be a serious health threat. [iii] Sen. Tom Carper

Quite a bit of the mercury put into the air each year is from this tonnage dug up from the ground, from medical, industrial and municipal incinerators, but about 1,000 tons a year results from the burning of coal to generate electrical power with an overly large share of it coming from China. Thus some have argued that even if all U.S. power plants were shut down tomorrow Americans are still at risk from mercury that gets carried around the globe in the upper atmosphere.