Unconventional Natural Gas Development and Birth Outcomes in Texas

Introduction: Unconventional natural gas (UNG) development has expanded rapidly in the United States and may contribute to local air pollution exposures; however, very little epidemiological research has been conducted to-date. Methods: We investigated the association between UNG development and adverse birth outcomes in Texas, using a population-based birth cohort from 1996-2009. Exposure assessment was conducted separately for operating and drilled wells (n= 463,021 and 399,168 births, respectively) and includes distance and squared inverse-distance weighted (IDW2), number of days in pregnancy living upwind and downwind from nearest well, and production levels for operating wells. We used multivariate linear and logistic regression to examine associations between UNG exposure measures and term birth weight, small for gestational age (SGA), and premature birth (<37 weeks gestation). Results: In fully adjusted models term birth weight was lower for mothers living closer to operating drilled wells as well as for increasing IDW2 measures. For example, birth weights for the quartile living closest to drilled and operating wells were 5.5g (95% CI: -8.31;-2.77) and 3.0g (95% CI: -5.90;-0.11) less than births weights in quartile 4 (reference group). Decreased term birth weight (-25.81g, 95% CI: -38.51;-13.11) and odds of SGA (1.18, 95% CI: 1.07;1.30) were greater for mothers living closer and downwind but not upwind of nearest operating well. Conclusions: These findings suggest that air pollution from UNG development may contribute to adverse birth outcomes. Further studies are warranted to measure local air pollution exposures and associated health impacts.