EPA Strongly Cautions that These Modeling Results Should Not be Use

EPA strongly cautions that these modeling results should not be used to draw conclusions about local exposure concentrations or risk. The results are most meaningful when viewed at the state or national level; for smaller areas, the modeling becomes less certain. In addition, these results represent conditions in 1996 rather than current conditions and only include exposures from outdoor sources of air toxics. The exposure estimates presented above represent midrange estimates of population exposures. Due to a number of factors, some individuals may have substantially higher or lower exposures. It is important to note that the model, as applied on the national scale, is not designed to quantify these extreme values of individual exposures.
Note that for certain chemicals, exposure
pathways other than inhalation as well as indoor sources of air
toxics may contribute substantially to total exposures of concern.
This assessment does not address these other routes of exposure
(i.e., ingestion or dermal) or inhalation exposure resulting from
indoor sources. The emissions used in this assessment do not reflect potentially
significant emission reductions that have taken effect since 1996,
including those from: 1) mobile source regulations which are being
phased in over time; 2) many of the air toxics regulations EPA has
issued for major industrial sources; 3) State or industry initiatives;
and 4) any facility closures. Simplified modeling assumptions may introduce significant uncertainties into each component of the assessment. See the full discussion of these limitations. Because of these uncertainties, EPA will not use the results of this assessment to determine source-specific contributions or to set regulatory requirements. However, EPA expects to use these results to inform decisions about the priorities of the air toxics program as well as to guide the collection of additional data that could lead to regulatory decisions.
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