By Timothy Gardner

WASHINGTON (Reuters) - The Obama administration on Friday tightened limits on harmful soot pollution from sources including power plants, diesel engines and burning wood.

The new standards, which the Environmental Protection Agency was under court order to finalize, limit annual average soot emissions by the end of decade to about 12 micrograms per cubic meter of air from the standard of 15 micrograms set in 1997.

Individual states will be responsible for deciding how to cut emissions of the fine particulates, which can lodge deep in the lungs and threaten the elderly, people with heart disease and children. Health problems associated with the pollution include premature death, acute bronchitis, and asthma.

"More mothers like me will be able to rest a little easier knowing that our children and our children's children will have healthier air to breathe for decades to come," EPA Administrator Lisa Jackson, who has two sons with asthma, told reporters in a conference call about the rules.

Industry groups and some lawmakers have complained the soot standards are too costly. The standards "impose significant new economic burdens on many communities, hurting workers and their families," a group of senators including global warming skeptic Jim Inhofe, an Oklahoma Republican, and Mary Landrieu, a Louisiana Democrat, said in a letter on Friday to Jackson.

New power plants, machinery at ports and other industrial sources of soot could find it hard to get operating permits in places found in violation of the limits.

The American Petroleum Institute, an industry group, said it feared the new rule "may be just the beginning of a ‘regulatory cliff'" including forthcoming EPA rules on smog and greenhouse gas emissions.

"EXCITING AND ENERGIZING"

The EPA, however, estimated that by 2030 the soot rules would prevent up to 40,000 premature deaths and that health care bills would be cut by $4 billion to $9 billion annually. Costs on industry to implement the rules would range from $53 million to $350 million, it said.

The agency said only seven counties, all of them in central or southern California, are projected to fail to meet the standard by 2020. The rest of the counties can rely on air quality standards that have already been finalized to meet the limits, it said. Continued...