Cumulative Environmental Quality Associations with Limb Reduction Birth Defects

Individual environmental exposures have been associated with limb reduction birth defects, including limb reduction, transverse limb reduction and longitudinal limb reduction. However, environmental exposures often occur simultaneously and the contribution of multiple exposures in association these limb reduction defects is not well understood. We used the Environmental Quality Index (EQI) and its five domains (air, water, land, sociodemographic, built) to estimate county-level cumulative environmental exposures from 2000-2005. The EQI domains were divided into three exposure categories based on percentiles (75%, "worst") and matched to limb reduction, transverse limb reduction and longitudinal limb reduction defects identified from Texas Birth Defects Registry and live birth records from 2000-2006 to assess associations using Poisson regression models. There was an increased prevalence of longitudinal limb reduction defects [prevalence ratio (PR) 1.17, (95% confidence interval:1.06,1.29)], but not limb reduction or transverse limb reduction defects comparing the worst environmental quality category compared to the best for overall EQI. The strongest associations were observed in the sociodemographic domain, with worse environmental quality associated with higher prevalence of limb reduction (1.62,95%CI:1.45,1.80), transverse limb reduction (1.46,95%CI:1.31,1.62), and longitudinal limb reduction (1.82,95%CI:1.63,2.04). In the water domain, associations were non-linear. Compared to better environmental quality, mid and worst environmental quality were associated with higher prevalence of limb reduction (1.61,95%CI:1.43,1.81 and 0.56,95%CI:0.50,0.62, respectively); transverse limb reduction (1.38,95%CI:1.24,1.55 and 0.55,95%CI:0.49,0.61, respectively), and longitudinal limb reduction (1.91,95%CI:1.69,2.17 and 0.54,95%CI:0.48,0.61, respectively). Inverse associations were observed in the air, land, and built domains for all three outcomes (limb, transverse limb, and longitudinal limb reduction defects). When assessing the associations between cumulative environmental exposures and limb reduction defects, strong, positive associations were found with sociodemographic factors and water quality, but not with air, land or built environmental quality. This abstract does not reflect EPA policy.