The July 23 editorial wondered why the federal government is going after mercury in the air but not mercury in dental fillings. This concern is misplaced because of a misunderstanding of the science and medicine involved. The issue is quantitative, and the editorial writers didn't do the math.
Silver dissolves into mercury to make an amalgam, in which the components interact chemically to form a metallic solid. A filling lasts for many decades, so mercury can't be escaping very fast. It has been measured to be about 1.6 micrograms a day for a person with seven fillings.
The mercury spill that closed down Eastern Kentucky University was 500 grams (500,000,000 micrograms). Meanwhile, U.S. coal-fired power plants release 50 tons of mercury a year: that is 50,000,000,000,000 micrograms.
Divide by 300,000,000 people in the country and the number of days in a year (365), and you will get 500 micrograms per person per day.
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The comparison isn't accurate, because the power-plant mercury is spread all over the environment while the dental mercury is already in your mouth. But rain washes the mercury into the rivers and into our water supply. The Environmental Protection Agency's recommended level for mercury contamination in drinking water is 2 micrograms per quart, and there are already places in Kentucky that don't meet this.
There is also a distinction between inorganic mercury (which is what comes from your fillings) and methylmercury (which dissolves in water and oil, and is what the EPA is measuring in the water). Inorganic mercury is slowly converted into methylmercury by bacteria. Inorganic mercury isn't accumulated biologically, whereas methylmercury is; that's what causes mercury poisoning. The bioaccumulation effect is the reason the Kentucky Department of Fish and Wildlife recommends that you do not eat more than one fish from a Kentucky river in any month.
The final point missed by the editorial is the relationship between cost and benefit. Dental amalgam is a long-term solution to what otherwise would be a chronic health issue; it has been studied extensively, and the health aspects are pretty well understood.
There is no good reason for mercury to be in our air or water, and the technology that removes it from power plant emissions will also remove other pollutants.