The National Air Toxics Assessment - The Initial National-Scale Assessment - #96

摘要

EPA conducted a national-scale air toxics assessment for 33 air pollutants. The assessment included the following four steps: (1) compiling a national emissions inventory of air toxics emissions from outdoor sources; (2) estimating ambient concentrations of air toxics across the contiguous United States; (3) estimating population exposures across the contiguous United States; and (4) characterizing potential public health risk due to inhalation of air toxics, including both cancer and noncancer effects. Given its broad scope, this assessment is subject to a number of limitations due to gaps in data or in the state of the science for assessing risk. The most important of these are that the assessment did not include (1) oral exposure, (2) indoor sources, (3) air pollutants beyond its list of 33, or (4) scheduled emissions reductions after 1996. Comparison of modeled ambient concentrations with monitor data suggested that the model may have systematically underestimated ambient levels for some pollutants. The results are best interpreted as applying to groups of people in geographic areas, rather than to individuals. EPA recommends that they be used in prioritizing collection of new data and planning more detailed local-scale assessments, but not as the sole basis for regulatory action.