Hourly Personal Exposures to Fine Particles and Gaseous Pollutants--results from Baltimore, Maryland

A study to characterize 1-hr multi-pollutant exposures was performed in Baltimore, MD, during the summer of 1998 and the winter of 1999, and was conducted over a 15-day period in each of the two seasons. Personal exposures were measured by a trained field technician, who wore a newly developed Roll-Around System (RAS) to measure 1-hr PM2.5 and gaseous (CO, O3, NO2, SO2, volatile organic compounds [VOCs]) exposures. One-hour O3, NO2, and SO2 personal exposures were measured using samplers developed in our laboratory, while short-term PM2.5, CO, and VOCs exposures were measured using currently available monitors. All 1-hr multi-pollutant exposures were measured while the technician performed pre-determined activities, beginning at 7:00 a.m. and ending at 7:00 p.m. of the same day. Activities were scripted to simulate activities performed by older adults (65+ years of age). Corresponding 1-hr ambient pollutant concentrations were obtained from federal or state monitoring networks. In this paper, we discuss the results from our study and present our descriptive analysis of the 1-hr personal particulate and gaseous exposure data. Personal PM2.5, O3, CO, and VOCs exposures showed substantial variability over the 12-hr sampling periods. Multiple pairwise comparison tests showed that 1-hr personal O3 exposures were significantly lower in indoor microenvironments as compared with outdoor microenvironments. One-hour personal CO exposures measured in vehicles were significantly higher than those measured in other microenvironments. The associations between 1-hr personal exposures and corresponding ambient concentrations differed by pollutant and by microenvironment. For example, the correlation between personal PM2.5 exposures and ambient concentrations was lowest (rs = 0.36, p < 0.05) in the winter for indoor non-residential microenvironments, and was highest (rs = 0.90, p < 0.05) in the winter for in-vehicle microenvironments. For O3, the correlation between personal exposures and ambient levels was weakest in the winter for residential microenvironments (rs = 0.05, p > 0.05), and was strongest in the summer for outdoor near-roadway microenvironments (rs = 0.91, p < 0.05).