Mercury, arsenic and acid gases don't belong in the open air, where they cause sickness, heart attacks and premature deaths. Now these toxic emissions from coal-fired power plants will finally be curbed by an Environmental Protection Agency ruling.

The decision by the Obama administration caps some 20 years of government study and heavy lobbying by the coal and power generating industries. It's a welcome show of regulatory resolve at a time when GOP presidential contenders scoff at environmental rules and the White House's commitment to clean air was questioned by environmentalists.

The toxics at issue are blamed for some 11,000 early deaths and serious side effects. After spewing untouched out of power plant smokestacks, the substances settle into the natural food chain. For example, fish with high levels of mercury are consumed by humans who suffer the ill effects.

Study after study showed the problem while the EPA contemplated where to set the limit and to gauge the costs.

Under the ruling, power plants must install cleanup equipment with a deadline of up to four years. The total cost is estimated at nearly $10 billion, far smaller than health care bills attributed to the toxics.

There are, of course, predictions of job losses from plants forced to close and fears of spotty power deliveries. But an Associated Press analysis suggests a number of generators are already moving toward cleaner smokestacks, with only the oldest power plants likely to shut down. Also, more than 12 states already have imposed EPA-like limits on the toxic emissions.

More broadly, the ruling gives a fuller picture of the Obama administration's approach. It's not shy about using regulatory powers to push its policies, though it comes with a moderating touch.

In September, the White House overruled the EPA on smog controls targeting chemicals pouring out of power plants. The reason then was that the heavy cost outweighed public health benefits.

Earlier, the administration had used its federal powers to double auto mileage minimums - a plan that both saves gas and cuts emissions - and imposed limits on the downwind drift of harmful chemicals across state lines.

The mercury decision this week is another turning-point choice in cleaning up the environment. The White House got it right this time, and the public, not the coal industry, is the rightful winner.