December 12th, 2017
The purpose of this document is to present air quality criteria for carbon monoxide (CO), in accordance with Sections 108 and 109 of the CleanAirAct (CAA), that reflect the latest scientific information useful in indicating the kind and extent of all identifiable effects on public health and welfare that may be expected from the presence of CO in ambient air. This document is an update ofAir Quality Criteria for Carbon Monoxide, published by the U.S. Environmental ProtectionAgency in 1991, and will be used as the scientific basis for reevaluating the current NationalAmbientAir Quality Standards (NAAQS) for CO. This executive summary summarizes key findings from the present document.