What air toxics are included in the 1999 national-scale assessment?
The 1999 national-scale assessment includes emissions and ambient concentrations for 177 air toxics plus diesel PM. It also includes an exposure and risk assessment (cancer risk and noncancer hazard) for 133 of these air toxics (this subset is identified in the list of 178 pollutants in the assessment), plus an exposure and noncancer hazard assessment for diesel PM. EPA was able to characterize the cancer risk and noncancer hazard from this subset of 133 air toxics and diesel PM since these pollutants have health data based on chronic exposure. It should be noted that in December 2005 the EPA removed Methyl Ethyl Ketone (MEK) from the Clean Air Act list of HAPs, However, NATA was conducted prior to this action, thus MEK was included in the assessment.
