The damages are caused almost equally by coal and oil, according to the study, which was ordered by Congress. The study set out to measure the costs not incorporated into the price of a kilowatt-hour or a gallon of gasoline or diesel fuel.
The estimates by the academy do not include damages from global warming, which has been linked to the gases produced by burning fossil fuels. The authors said the extent of such damage, and the timing, were too uncertain to estimate.
Nor did the study measure damage from burning oil for trains, ships and planes. And it did not include the environmental damage from coal mining or the pollution of rivers with chemicals that were filtered from coal plant smokestacks to keep the air clean.
“The largest portion of this is excess mortality — increased human deaths as a result of criteria air pollutants emitted by power plants and vehicles,” said Jared L. Cohon, president of Carnegie Mellon University in Pittsburgh, who led the study committee.Nearly 20,000 people die prematurely each year from such causes, according to the study’s authors, who valued each life at $6 million based on the dollar in 2000. Those pollutants include small soot particles, which cause lung damage; nitrogen oxides, which contribute to smog; and sulfur dioxide, which causes acid rain.
Coal burning was the biggest single source of such external costs . The damages averaged 3.2 cents per kilowatt-hour, compared with 0.16 cents for gas. But the variation among coal plants was enormous.