Photodegradation of six polycyclic aromatic hydrocarbons (PAHs) was studied in liquids composed of actual organic aerosol constituents using a photochemical turntable reactor. All six PAHs exhibited more rapid decay in a liquid mixture of methoxyphenols, an abundant class of compounds present in wood smoke, than in hexadecane, which is representative of aliphatic hydrocarbons abundant in diesel soot and automobile exhaust. The most rapid decay was observed for benz [a] anthracene and benzo[a]pyrene in both hexadecane and the methoxyphenols. Benzo [o] pyrene decay was approximately seven times faster in the methoxyphenol mixture than in hexadecane. The results indicate that the organic composition of atmospheric particulate matter can influence PAH decay.

No abstract

Personal 48-hr exposures to formaldehyde and acetaldehyde of 15 randomly selected participants were measured during the summer/autumn of 1997 using Sep-Pak DNPH-Silica cartridges as a part of the EXPOLIS study in Helsinki, Finland. In addition to personal exposures, simultaneous measurements of microenvironmental concentrations were conducted at each participant's residence (indoor and outdoor) and workplace. Mean personal exposure levels were 21.4 ppb for formaldehyde and 7.9 ppb for acetaldehyde. Personal exposures were systematically lower than indoor residential concentrations for both compounds, and ambient air concentrations were lower than both indoor residential concentrations and personal exposure levels. Mean workplace concentrations of both compounds were lower than mean indoor residential concentrations. Correlation between personal exposures and indoor residential concentrations was statistically significant for both compounds. This indicated that indoor residential concentrations of formaldehyde and acetaldehyde are a better estimate of personal exposures than are concentrations in ambient air. In addition, a time-weighted exposure model did not improve the estimation of personal exposures above that obtained using indoor residential concentrations as a surrogate for personal exposures. Correlation between formaldehyde and acetaldehyde was statistically significant in outdoor microenvironments, suggesting that both compounds have similar sources and sinks in ambient urban air.

No abstract

In-vehicle exposures to different sizes of particles and carbon monoxide (CO) were determined while driving along a standardized route under a variety of traffic conditions in Kuopio, Finland during the 12-month period from January to December 1995. Arithmetic means of in-vehicle exposures during the 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 m) and 0.9 #/cm 3 (GM=0.6 #/cm 3 , GSD=2.1) for coarse particles (optical equivalent particle size range 1±10 m). Fine particles and CO behaved similarly in different weather and traffic conditions, while the behavior of coarse particles was usually different, and often opposite. The driving conditions that affected the passengers' exposures to CO and fine particles were the time of day (morning vs. afternoon) and average speed (decreasing). The meteorological parameters that affected the passengers' exposures to CO and fine particles were wind speed (decreasing) and relative humidity (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 fine particles were considerably higher in the morning vs. the afternoon runs and also higher in the slower vs. the faster runs.