"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."