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Equating Semi-Continuous (SC) PM2.5 Mass Monitor Measurement Values with Federal Reference Method (FRM) PM2.5 Monitor Measurement Values
Citation:
HALL, ERICS. Equating Semi-Continuous (SC) PM2.5 Mass Monitor Measurement Values with Federal Reference Method (FRM) PM2.5 Monitor Measurement Values . U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-11/039 (NTIS PB2011-110916), 2011.
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA′s mission to protect human health and the environment. HEASD′s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA′s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Description:
The effects of fine particulate matter (PM2.5) on human health are well documented (Pope et al., 2002). In order to spatially and temporally assess the impact of PM2.5 on the U.S. population, the U.S. Environmental Protection Agency (U.S. EPA) operates a network of Federal Reference Method (FRM) air quality monitors which measure ambient PM2.5 concentration in locations that are important due to the need to track compliance with the National Ambient Air Quality Standards (NAAQS) mandated concentration levels in geographic regions of interest and to assess exposures of local populations where the monitors are located. When scientists attempt to correlate ambient concentration levels of PM2.5 to documented health outcomes, in most cases, they are forced to use the PM2.5 concentration measurement values from the monitor(s) closest to the study area as a surrogate for measuring ambient PM2.5 concentration at (or nearer to) the actual location of the study population(s). Due to prohibitive cost, land-use concerns, and EPA’s current strategy for locating air quality monitors, it is not practical to place PM2.5 FRM monitors more closely to improve measurement of ambient PM2.5 concentration for health studies. The standard FRM monitors used to determine the ambient concentration of PM2.5 are filter-based, and the schedule for filter collections is either once every three days (1-in-3) or once every six days (1-in-6). The PM2.5 particles collected on the filters are weighed and the daily concentration of PM2.5 determined for each monitor/site (Noble et al., 2001). A number of technologies/methodologies have been developed for Federal Equivalent Method (FEM) monitors, which measure PM2.5 particles in a continuous/semi-continuous (non-filter based) manner and provide ambient concentration measurements of PM2.5 on an hourly basis (Noble et al., 2001). An increasing number of semi-continuous (SC)/FEM monitors have been deployed each year in the U.S. by EPA to improve the extent of spatial and temporal coverage for ambient PM2.5 concentration measurements. Since a number of the FEM monitors are (and will be) located in areas where FRM monitors used to measure PM2.5 currently exist, a standard protocol for correlating PM2.5 measurements from FEM monitors with PM2.5 measurements from FRM monitors (used to make determinations of NAAQS compliance) must be developed to allow health researchers to measure/report ambient PM2.5 concentration levels linked to health outcomes in a consistent manner to allow more relevant comparisons between health studies. Also, developing a standard methodological approach for correlating PM2.5 measurements from FEM monitors with those from FRM monitors accounting for effect of regional differences, state differences, seasonal differences, equipment/method differences, year, etc., facilitates meaningful comparisons between measurement values and monitor behavior. The purpose of the research report is to provide a well-documented methodology/protocol that can be implemented to correlate FRM and FEM ambient concentration measurements from PM2.5 monitors. This report serves as a starting point for future research activity in this area.