Characterization of personal exposures to ambient and indoor particulate matter among children with asthma in Detroit, Michigan.

Abstract

The asthma prevalence among children has increased dramatically and has become a growing concern. A large body of epidemiological data has closely linked mortality and morbidity with elevated mass concentrations of ambient particulate matter (PM); many studies have also implicated PM in asthma exacerbation. To date, intensive studies in urban communities of children's exposures to PM together with detailed measures of their asthma status have not been reported. As part of Community Action Against Asthma, a community-based participatory research project in Detroit, MI, two-week seasonal measurement campaigns were conducted from 1999--2002 in which daily ambient and indoor measurements of PM_2.5 and PM₁₀ were collected at two elementary schools representing community-level exposure and exposure in the classroom, respectively. Concurrent measurements of PM_2.5 and PM₁₀ inside the homes of 20 asthmatic children, and personal measurements of PM₁₀ for the same 20 children using personal exposure monitors, were also performed. Evaluation of the PM for mass and chemical constituents permitted characterization of the sources directly impacting the children's personal exposures, and the data collected in the multiple environments provides us with a greater basis for source comparison. The children recorded spending, on average, 16 hours at home and five hours at school which represents approximately 88% of their day. The children's mean 24-hour personal exposures to PM₁₀ were consistently greater than the concentrations measured in the ambient environment and in the classroom. Similarly, the environments in which the children spent the most time were reflected in the elemental concentrations in the children's personal exposures. The trace element concentration observed among the children in both smoking and non-smoking households were strongly and significantly correlated to their home concentrations. The main sources of the children's PM₁₀ mass were consistently environmental tobacco smoke, secondary sulfate, and windblown dust, which represent more than half of the source-contributed mass and explained a majority of the day-to-day variability that was observed in the mass. Mass measurements helped in characterizing the magnitude of the children's PM exposure, but the addition of elemental composition data enabled us to gain insight into the causes of elevated exposures and the sources that influenced the variability. These data will be extremely useful when ultimately evaluating potential sources that can lead to the exacerbation of asthma symptoms.