Can I compare data across assessments?
For each assessment, EPA has improved its methodology by doing all of the following:
Use a better and more complete inventory of emission sources
Increase the number of air toxics evaluated
Improve upon health data information used in assessments
Due to the extent of improvements in methodology, it is not meaningful to compare the assessments. This is because any change in emissions, ambient concentrations, or risks maybe due to either improvement in methodology or to real changes in emissions or source characterization.
How are NATA assessments developed?
NATA assessments generally include a four step process including:
Compile a national emissions inventory from outdoor sources.
Estimate ambient concentrations of air toxics across the United States.
Estimate population exposures across the United States.
Characterize potential public health risks due to inhalation of air toxics.
Is NATA a collaborative process?
EPA collaborated with State, local and Tribal agencies to develop the information that is contained in the assessment. Communities have been actively involved in partnerships with local governments to use NATA data to develop local toxics inventories and to provide the basis for developing a community-supported plan for reducing toxic emissions. The National Research Council (NRC) in their review of the 1996 NATA ,emphasized in their 2004 report on “Air Quality Management in the United States” Exit EPA disclaimer that “NATA has provided a tool for exploring control priorities and has served as a preliminary attempt to establish a baseline for tracking progress in reducing HAP emissions”.(See p.247 of that report).
Aside from interactions with other environmental agencies, EPA has sought to collaborate with EPA’s Science Advisory Board which provided helpful comments through their peer review process. The methods used for these assessments were peer-reviewed and endorsed by EPA’s Science Advisory Board in 2001. (See http://www.epa.gov/ttn/atw/sab/sabrev.html). The SAB review concluded that NATA represents “an important step toward characterizing the relationship between sources and risk of hazardous air pollutants”.