The US Environmental Protection Agency (EPA) has unveiled a new SO2 emissions standard that will have an effect on coal-plant output, but will better protect people from short-term exposure to the pollutant.
SO2, primarily emitted from power plants and other industrial facilities, is a major cause of asthma and respiratory disorders.
The EPA has set the new one-hour SO2 health standard at 75 parts per billion (ppb) to protect against short-term exposures ranging from five minutes to 24 hours.
The agency has replaced the old standard based on 24-hour and annual SO2 health standards to meet shorter-term guidelines.
Coal-burning utilities such as Southern Co and American Electric Power may need to take steps to reduce emissions under the new rule.
The rule is estimated cost the industry about $1.5bn in 2020.