Characteristics of Carbonyls: Concentrations, Possible Sources, and Personal Exposures for Indoor and Outdoor Subway Microenvironments

Characteristics of carbonyl compounds including their concentrations, possible sources and personal exposure were investigated in six underground subway stations in Shanghai in June 2008. Nineteen out of twenty target carbonyls were detected with the exception of 2,5-dimethylbenzaldehyd. Formaldehyde was the most abundant carbonyl, followed by acetaldehyde and acetone. Their highest mean concentrations were 31.5±2.96, 22.5±2.75 and 18.7±2.69 μg/m3, and contributed more than 30%, 21% and 18% of the total carbonyl concentrations, respectively. A significant correlation (r>0.5, p<0.01) between the concentration of the low molecular-weight carbonyl compounds (<C5) and ozone was found in the subway stations. Comparison of the indoor and outdoor carbonyl concentrations found "indoor>outdoor" for every carbonyl species except for benzaldehyde and o/m/p-tolualdehyde which might possible come from the outdoor source as a result of air exchanged by the ventilation system. The personal exposure showed that the underground subway stations were an important microenvironment for exposure to formaldehyde and acetaldehyde, especially for people who worked in the subway stations.