This story was updated at 12:55 p.m. EST.
The current air quality standards for carbon monoxide (CO) are strong enough to protect public health, U.S. EPA said today as the agency issued a proposal to keep the existing limits.
Carbon monoxide is best known for its ability to reach dangerously high levels in homes, but the poisonous gas is also regulated under the Clean Air Act because elevated levels outdoors can lead to health problems. It is released mainly from the tailpipes of cars and other pieces of equipment that use combustion engines.
After a court-ordered review of the standards, EPA Administrator Lisa Jackson concluded that there was not a reason to revise the current limit on CO, which is 9 parts per million averaged over an eight-hour period and 35 ppm over a one-hour period. The entire country has met those limits, which have not been reassessed since EPA decided not to change the existing standards in 1994.
"After careful review of the available health science, EPA concludes that the current standards provide the required level of public health protection, including protection for people with heart disease, who are especially susceptible to health problems associated with exposure to CO in ambient air," the agency said today in a statement.
Up until today, it had been unclear whether the agency would set stricter limits. Tougher standards might be justified by new research that linked low levels of carbon monoxide exposure to heart problems, agency staffers had said in an October policy assessment (Greenwire, Dec. 21, 2010).
The agency's scientific advisers had agreed, saying the decision would come down to a policy judgment by the administrator.
"Current levels of CO are far lower than historic levels and the risk for health effects associated with these current levels may be minimal or difficult to quantify with certainty," a panel of the Clean Air Scientific Advisory Committee said in a separate letter to Jackson. "However, the degree of protection afforded to susceptible populations by the current [standards] still needs to be considered by EPA. A greater degree of protection may be warranted."
The agency has been reviewing the carbon monoxide standards since 2008, when a federal judge in San Francisco ordered EPA to decide whether an update is necessary. EPA must now take comments on today's proposal and issue a final rule by Aug. 12.
Click here to read the proposal.
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