Urban commuter exposure to particle matter and carbon monoxide inside an automobile

In-vehicle exposures to different sizes of particles and carbon monoxide (C O) were determined while driving along a standardized route under a variety of traffic conditions in Kuopio, Finland during the 12-month period From J anuary to December 1995. Arithmetic means of in-vehicle exposures during th e morning rush hours were 5.7 parts per million (ppm) (geometric mean, GM=3 .1 ppm, geometric standard deviation, GSD=1.7) for CO, 107 #/cm(3) (GM=75 # /cm(3) GSD=1.9) for fine particles (optical equivalent particle size range 0.3-1 mu m) and 0.9 #/cm(3) (GM=0.6 #/cm(3), GSD=2.1) for coarse particles (optical equivalent particle size range 1-10 mu m). Fine particles and CO b ehaved similarly in different weather and traffic conditions, while the beh avior of coarse particles was usually different, and often opposite. The dr iving conditions that affected the passengers' exposures to CO and fine par ticles were the time of day (morning vs. afternoon) and average speed (decr easing). The meteorological parameters that affected the passengers' exposu res to CO and fine particles were wind speed (decreasing) and relative humi dity (increasing). Wind speed, relative humidity and driving speed all had opposite effects on the exposure levels to fine vs, coarse particles. Added exposures (due to commuting on top of the background levels) to CO and fin e particles were considerably higher in the morning vs. the afternoon runs and also higher in the slower vs, the faster runs.