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 Bal timore, MD, during the summer of 1998 and the winter of 1999, and was condu cted over a 15-day period in each of the two seasons. Personal exposures we re measured by a trained field technician, who wore a newly developed Roll- Around System (RAS) to measure 1-hr PM2.5 and gaseous (CO, O-3, NO2, SO2, v olatile organic compounds [VOCs]) exposures. One-hour O-3, NO2, and SO2 per sonal exposures were measured using samplers developed in our laboratory, w hile 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 simula te activities performed by older adults (65+ years of age). Corresponding 1 -hr ambient pollutant concentrations were obtained from federal or state mo nitoring networks. In this paper, we discuss the results from our study and present our descri ptive analysis of the 1-hr personal particulate and gaseous exposure data. Personal PM2.5, O-3, CO, and VOCs exposures showed substantial variability over the 12-hr sampling periods. Multiple pairwise comparison tests showed that 1-hr personal O-3 exposures were significantly lower in indoor microen vironments as compared with outdoor microenvironments. One-hour personal CO exposures measured in vehicles were significantly higher than those measur ed in other microenvironments. The associations between 1-hr personal expos ures and corresponding ambient concentrations differed by pollutant and by microenvironment. For example, the correlation between personal PM2.5 expos ures and ambient concentrations was lowest (r = 0.36, p < 0.05) in the wint er for indoor non-residential microenvironments, and was highest (r = 0.90, p < 0.05) in the winter for in-vehicle microenvironments. For O-3, the cor relation between personal exposures and ambient levels was weakest in the w inter for residential microenvironments (r = 0.05, p > 0.05), and was stron gest in the summer for outdoor near-roadway microenvironments (r(s) = 0.91, p < 0.05).