Appendix E describes the inventory methodology and presents the toxics inventory by major source categories and relative contribution by source category. An emissions inventory provides the basis for developing effective control strategies and the relative contribution by source category. Figure 6 illustrates the source apportionment by toxicity-weighted emissions for the basin . This figure summarizes the overall emission distribution based on the 1998 inventory, excluding natural sources. In this figure, the emissions provided in Appendix E, Table E-2, have been weighted by their unit risk factors.
Stationary sources account for five percent of the toxicity-weighted emissions.
Therefore, any direct comparison would not be a proper use of the information and would produce inaccurate findings. EPA will be updating risk estimates for major metropolitan areas in their Cumulative Exposure Project document, but that will not be completed for some time.