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USE OF CONTINUOUS NEPHELOMETER TO MEASURE PERSONAL EXPOSURE TO PARTICULATE MATTER DURING THE 1998 U.S. EPA BALTIMORE PANEL STUDY
Citation:
HowardReed, C, M J. Zufall, J M. Burke, R W. Williams, J C. Suggs, D. B. Walsh, R K. Kwok, AND L S. Sheldon. USE OF CONTINUOUS NEPHELOMETER TO MEASURE PERSONAL EXPOSURE TO PARTICULATE MATTER DURING THE 1998 U.S. EPA BALTIMORE PANEL STUDY. Presented at PM2000 AWMA Conference, Charleston, SC, January 25-28, 2000.
Description:
Personal exposures to particulate matter (PM) have typically been measured using filter samplers worn by the participants in exposure studies. Personal filter samplers, however, are limited to providing average mass concentrations integrated over a 12- to 24-hour period due to low sample flow rates and environmental PM concentrations. To better understand the short-term variation in personal PM exposure, continuous (one-minute averaging time) nephelometers were worn by five participants as part of a four-week study completed at a retirement center in Baltimore, Maryland. The personal nephelometer (pDR-1000, MIE, Inc.) is a passive instrument that uses light-scattering to measure particle number in the size range of 0.1 um to 10 um. Based on gravimetric calibration to an SAE Fine test dust (mmd = 2 to 3 um, bulk density = 2.60 to 2.65 g/cm3, refractive index 1.54), the pDR-1000 reports mass concentration. In addition to wearing the pDR-1000, participants also wore Personal Exposure Monitors (PEMs) with a 2.5 um cut-point) (24-hour integrated filter samples) and recorded their daily activities in 15 minute intervals.
The time-series plots of personal nephelometer data showed each participant's PM exposure to consist of a series of peaks of relatively short duration. The highest measured one-minute mass concentration was 2.5 mg/m3, which was two orders of magnitude greater than the associated 24-hour time-weighted average. Activities corresponding to a significant instrument response included: outdoor activities, transportation, laundry, cleaning, cooking, moving between microenvironm.ents, and removing/putting on the instrument. In comparison with the 2.5 um PEM filter samples, the pDR-1000 generally measured higher 24-hour integrated mass concentrations (geometric mean = 1.5, 0g = 2.0, n = 34). Although not a reference method .for measuring mass concentration, the pDR-1000 did provide useful information regarding the identification of PM sources and their relative contribution to one's personal exposure.
This work has been funded wholly or in part by the United States Environmental Protection Agency under contract 68-D5-0040. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does trot constitute endorsement or recommendation for use.