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USE OF A CONTINUOUS NEPHELOMETER TO MEASURE PERSONAL EXPOSURE TO PARTICLES DURING THE U.S. EPA BALTIMORE AND FRESNO PANEL STUDIES
Citation:
HowardReed, C, A W. Rea, M J. Zufall, J M. Burke, R W. Williams, J C. Suggs, L S. Sheldon, D. B. Walsh, AND R K. Kwok. USE OF A CONTINUOUS NEPHELOMETER TO MEASURE PERSONAL EXPOSURE TO PARTICLES DURING THE U.S. EPA BALTIMORE AND FRESNO PANEL STUDIES. JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION 50(7):1125-1132, (2000).
Impact/Purpose:
The primary study objectives are:
1.To quantify personal exposures and indoor air concentrations for PM/gases for potentially sensitive individuals (cross sectional, inter- and intrapersonal).
2.To describe (magnitude and variability) the relationships between personal exposure, and indoor, outdoor and ambient air concentrations for PM/gases for different sensitive cohorts. These cohorts represent subjects of opportunity and relationships established will not be used to extrapolate to the general population.
3.To examine the inter- and intrapersonal variability in the relationship between personal exposures, and indoor, outdoor, and ambient air concentrations for PM/gases for sensitive individuals.
4.To identify and model the factors that contribute to the inter- and intrapersonal variability in the relationships between personal exposures and indoor, outdoor, and ambient air concentrations for PM/gases.
5.To determine the contribution of ambient concentrations to indoor air/personal exposures for PM/gases.
6.To examine the effects of air shed (location, season), population demographics, and residential setting (apartment vs stand-alone homes) on the relationship between personal exposure and indoor, outdoor, and ambient air concentrations for PM/gases.
Description:
In population exposure studies, personal exposure to particulate matter (PM) is typically measured as a 12- to 24-hour integrated mass concentration. To better understand short-term variation in personal PM exposure, continuous (one-minute averaging time) nephelometers were worn by 15 participants as part of two U.S. Environmental Protection Agency(U.S. EPA) longitudinal PM exposure studies conducted in Baltimore County, Maryland and Fresno, California. Participants also wore inertial impactor samplers (24-hour integrated filter samples) and recorded their daily activities in 15 minute intervals. In Baltimore, the nephelometers correlated well (R2= 0.66) with the PM2.5 impactors. Time-series plots of personal nephelometer data showed each participant's PM exposure to consist of a series of peaks of relatively short duration. Activities corresponding to a significant instrument response included cooking, outdoor activities, transportation, laundry, cleaning, shopping, gardening, moving between microenvironments, and removing/putting on the instrument. On average 63% - 66% of the daily PM exposure occurred indoors at home (about 2/3 of which occurred during waking hours), primarily due to the large amount of time spent in that location (an average of 72% - 77%). Although not a reference method for measuring mass concentration, the nephelometer did help identify PM sources and the relative contribution of those sources to an individual's personal exposure.
The U.S. Environmental Protection Agency through its Office of Research and Development funded and managed the research described here under contract #68-D5-0040 to the Research Triangle Institute. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.