A published summary of the workshop (Lippmann et al. 1996) identified the following areas of research to be most useful with respect to health risk assessment for particulate matter:
Study accumulation-mode aerosol with the objective of disentangling the roles of its chemical constituents, as well as their interactive effects, with each other and with coexisting gaseous criteria pollutants.
Study the health effects of coarse-mode PM10 and the ultrafine particles in nuclei-mode aerosol.
Study sensitive human subpopulations—infants, the elderly, and people with pre-existing cardiopulmonary diseases.
Further develop and validate animal models for sensitive human groups. Validated animal models are needed for target (sensitive) human populations to investigate:
the roles of specific constituents of particulate-matter mixtures
the roles of exposure concentrations and durations of responses
the risk factors that predispose individuals to be responsive to particulate-matter exposures
physiological, biochemical, molecular, and pathological correlates of mortality, tissue and organ damage, and chronic disease development
As part of each periodic review of NAAQS under the Clean Air Act, EPA prepares a so-called ''criteria" document intended to describe the state of relevant scientific knowledge and important uncertainties in the existing evidence. In a separate document, EPA also identifies research needed to improve the scientific bases for future reviews of the NAAQS. Therefore, in 1996, when EPA prepared the revised criteria