Maternal exposure to hazardous air pollutants and birth defects among offspring: Texas, 1999-2008

Birth defects occur in approximately 1 out of every 33 births and are the leading cause of infant mortality in the United States. Those who survive often have disabilities and require lifelong medical care. In spite of the clinical significance and prevalence of these conditions, little is known about their etiologies. Environmental toxicants have long been suspected as being associated with disease risk. Hazardous air pollutants (HAPs), such as benzene and 1,3-butadiene are an important group of environmental toxicants commonly found in the air environment that are known or suspected to cause serious health effects. In fact, recent work in Texas suggests maternal exposure to outdoor levels of benzene is associated with neural tube defects, a malformation of the central nervous system. However, much work remains to evaluate the relationship between other HAPs and other birth defects. Therefore we proposed a case-control study to examine the association between HAPs and birth defects in the State of Texas. Texas is an ideal location to assess this association as it has both high and variable levels of several HAPs, and it is home to the Texas Birth Defects Registry (TBDR), one of the world's largest active surveillance systems of birth defects. Data on cases delivered between 1999 and 2008 were provided by the TBDR. The control group was a random sample of live births for the same period. Census tract-level estimates of HAPs concentrations were obtained from the U.S. Environmental Protection Agency 1999 Assessment System for Population Exposure Nationwide (ASPEN). We will use logistic regression to determine the association between HAPs and selected birth defect phenotypes. Results of this study should inform policy to protect maternal health and reduce harmful exposures.