Systematic review and meta-analysis of health effects associated with residential exposure to traffic emissions

Introduction: A growing body of research has suggested an association between residential exposure to traffic emissions and various health outcomes, including asthma and respiratory symptoms, cardiovascular disease, adverse reproductive outcomes, and premature mortality. Additionally, low-income and minority populations are more likely to live near heavy traffic. The Centers for Disease Control and Prevention conducted a systematic review and meta-analysis to assess the state of the evidence and quantify the health burden associated with residential exposure to traffic. Methods: We searched 15 electronic databases for original peer-reviewed articles and dissertations published during 1980–2008. Each article was screened for inclusion, abstracted, and assessed for study quality independently by two authors. Separate meta-analyses were conducted for each health outcome. For health outcome categories with a sufficient number of unique studies, we calculated weighted pooled odds ratios, assessed heterogeneity among studies, conducted subgroup analyses by study design, exposure assessment, and quality score, and assessed the potential for publication bias. Results: We identified 149 articles addressing the following health outcomes: 84 respiratory and allergic diseases, 22 cancer, 10 cardiovascular diseases, 9 reproductive outcomes, 8 mortality, and 16 other health outcomes. The results of this meta-analysis will be available by summer 2010. Conclusions: Living near heavy traffic is associated with a significant burden of disease in the United States and this burden is disproportionately shared by low-income and minority populations. Findings from this study can be used by researchers and practitioners to develop national, state, and local policies to improve population health.