How were the pollutants on the Air Toxics Priority List selected?
Subcommittees of the Air Toxics Advisory Committee (ATAC) used emissions inventory, monitoring, and toxicity data to rank all toxic air pollutants emitted in Maine. Estimated emissions of toxic air pollutants were multiplied by toxicity factors to take into account how hazardous each pollutant is to human health using a common weighting scale. This prioritized the pollutants relative to each other, but did not identify which posed an actual risk to the public. The subcommittees compared the ranked list to the compounds assessed in the 1996 National Air Toxics Assessment, which did quantify risk, to benchmark actual risk levels. These risk levels needed to be adjusted to 2005, however, to make them current with the most recent air toxic emissions inventory available. Risk levels in 2005 were estimated by applying the ratio of 2005 emissions and 1996 emissions to the 1996 NATA risk. The cutoff for inclusion on the priority list was set at a Health Quotient (HQ) of 1 or greater for non-ca
