Review of the national ambient air quality standards for carbon monoxide assessment of scientific and technical information. OAQPS staff paper. Final report

The paper evaluates and interprets the updated scientific and technical information that EPA staff believes is most relevant to the review of primary (health) national ambient air quality standards for carbon monoxide. The assessment is intended to bridge the gap between the scientific review in the EPA criteria document for carbon monoxide and the judgements required of the Administrator in setting ambient air quality standards for carbon monoxide. The major recommendations of the staff paper include the following: (1) There continues to be a need to control ambient levels of carbon monoxide to protect public health; (2) Both 1-hour and 8-hour averaging times should be retained for primary carbon monoxide standards; (3) Exposure analysis results indicate relatively few individuals with angina pectoris would experience carboxyhemoglobin (COHb) levels of 2.1% or greater when exposed to carbon monoxide levels in ambient air only if current standards are attained; (4) Public health risk for COHb levels of 2.0% or lower appears to be small, if any; (5) Current 1-hour (35 ppm) and 8-hour (9 ppm) standards for carbon monoxide should be reaffirmed.