Aldehydes in the Urban Environment

摘要

The Clean Air Act Amendments of 1990 included a section devoted to the reduction of mobile source emissions through fuel reformulation in which the oxygen content of fuel is increased by adding compounds containing oxygen, termed oxygenates. Oxygenates used in oxygenated fuel (“oxyfbel”) include methyl tert-butyl ether‘ (MTBE) and ethanol. The resulting fuel should decrease the ozone-forming hydrocarbons and total air toxics. However, adding oxygenates to gasoline can increase the emissions of aldehydes and thus increase human exposure to these toxic compounds. The main objective of this work is to compare measured aldehyde exposures for people living in two urban areas to estimated aldehyde exposures calculated using exposure models. Selected aldehydes (formaldehyde, acetaldehyde, acrolein, propionaldehyde, butyraldehyde, crotonaldehyde, glyoxal, methylglyoxal),VOCs (ethanol, MTBE, benzene, toluene, ethylbenzene, xylenes), and carbon monoxide (CO) were collected during periods of defined activity (scripts) in order to characterize the pollutants present in certain microenvironments. Two urban areas were chosen for the study. Sacramento, CAY was selected because of its use of MTBE, and Milwaukee, WI, was selected because of its use of ethanol. A total of 15 scripted monitoring periods were conducted that covered 18 microevironments in Sacramento, CA during August and September, 1999. Microenvironments sampled included various indoor and outdoor locations. Formaldehyde concentrations were lower in outdoor locations than in indoor locations; values ranged fiom 5.3 μg/m~3 in parwgolf course to 27 μg/m~3 in a store. Acetaldehyde concentrations followed a similar trend with values ranging from 3.2 μg/m~3 in an outdoor location to 78 μg/m~3 in a restaurant. A preliminary step-wise linear regression of the data was performed to identify the best predictors of the measured value and the regression coefficients that reflect the typical increase in the measured value when the predictor variable is applied. In addition, the use of Global Positioning System (GPS) monitors was useful to track sample collection locations relative to the city and fixed site monitors.