What are the quantitative relationships between concentrations of particulate matter and gaseous copollutants measured at stationary outdoor air-monitoring sites and the contributions of these concentrations to actual personal exposures, especially for subpopulations and individuals?

In its first report (NRC 1998), the committee recommended that information be obtained on relationships between total personal exposures and outdoor concentrations of PM. Specifically, the committee recommended longitudinal panel studies, in which groups of 10-40 persons would be studied at successive times to examine the relationship between their exposures to PM and the corresponding outdoor concentrations. The studies were intended to focus not only on the general population, but also on subpopulations that could be susceptible¹ to the effects of PM exposures, such as the elderly, children, and persons with respiratory or cardiovascular disease. It was recommended that some of the exposure studies include measurements of PM with an aerodynamic diameter of 2.5 µm or less (PM_2.5), PM with an aerodynamic diameter of 10 µm or less (PM₁₀), and gaseous copollutants. It was expected that the investigations would quantify the contribution of outdoor sources to personal and indoor exposures. The design and execution of studies were to take about 3 years, and the suggestion was made to conduct the studies at various geographical locations in different seasons.

Substantial research is in progress, and some studies, started before the committee's first report, have been completed. Results of