Home Indoor Pollutant Exposures among Inner-City Children With and Without Asthma (original) (raw)

2007, Environmental Health Perspectives

Asthma is common among children in the United States, especially those who are racial/ethnic minorities living in inner cities (Centers for Disease Control and Prevention 2004). Although definitive causes of asthma remain to be discovered, substantial evidence points to environmental exposures, which may in turn interact with individual genetic susceptibility-a phenomenon often called gene-environment interaction. Some evidence points to the heritability of asthma, because it occurs more commonly in children whose parents have asthma and in affected twins (Laitinen et al. 1998). Because not all cases of asthma arise in people with affected first-degree relatives, however, it leaves open the possibility that asthma results from high exposure to environmental factors. Evidence to support asthma causation through high exposure alone can come from studies that compare the environment of people with and without asthma. Environmental studies of inner-city children are especially important for understanding asthma disparities among African Americans. Asthma prevalence is 39% higher among African Americans than whites, and African Americans are more likely than whites to live in urban areas (86% vs. 70% of the respective populations), areas which are at high risk for air pollution (American Lung Association 2005). Indeed, 65% of African Americans live in counties that failed to meet at least one of the U.S. Environmental Protection Agency's (EPA) outdoor air quality standards (American Lung Association 2005). The home indoor environment is especially relevant for studying inner-city childhood asthma, because some pollutants, such as ambient particulate matter (PM), penetrate from the outside, and some are generated and remain indoors, such as particles and gases from smoking, heating, cooking, and cleaning (Abt et al. 2000; Howard-Reed et al. 2000; Long et al. 2000; National Research Council and Committee on Research Priorities for Airborne Particulate Matter 2004; Rea et al. 2001; Vette et al. 2001). Remarkably, a previously published study from the Center for Childhood Asthma in the Urban Environment, conducted in older children from inner-city Baltimore (90% African American), has already shown that children are exposed to concentrations of indoor PM that are three times the concentrations found in outdoor air (Breysse et al. 2005). Such concentrations would frequently exceed the outdoor limits set by the U.S. EPA (Breysse et al. 2005). Furthermore, the indoor environment may be especially critical to study because Americans, including preschool children, spend the vast majority of time indoors. Studies are urgently needed to determine the causes of the asthma epidemic, and in response to this need, there has been support for research from the U.S. federal government to uncover the role of environmental exposures in the etiology and prevention of prevalent disorders, such as asthma, in children (National Institute of Environmental Health Sciences 2003). To address this issue, the Johns Hopkins Center for Childhood Asthma in the Urban Environment conducted a study to determine whether indoor home environmental pollutants are greater in homes of preschool children with asthma compared with homes of children without asthma. Methods Study population. We recruited children 2-6 years of age who resided in urban area of Baltimore, Maryland, defined by 9 contiguous zip codes. Children with and without asthma were identified using a two-stage screening method. All children who were patients of health systems that provide care to most East Baltimore residents were identified from billing records. If the child had had a health care encounter for asthma [International Classification of Diseases, 9th Revision (ICD-9) code 493.x (World Health Organization 1975)] in the previous 12 months, he or she was considered a potential asthma subject. Asthma status was confirmed, for the purposes of this study, if the primary caregiver also reported that the child met both of the following criteria: a) doctor-diagnosed asthma