Birth Defects and Mothers’ Proximity to Natural Gas Development: Is There a Connection?

More than 15 million Americans are now estimated to live within one mile of a natural gas well drilled since 2000. Research has demonstrated that natural gas development results in the emission of pollutants that include suspected developmental toxicants, such as benzene, toluene, and xylenes, 2 although few studies have investi­ gated the public health impact of these emissions. In this issue of EHP, researchers report preliminary evidence of an association between two birth defects and a mother's residential proximity to natural gas wells at the time of birth. 3 " Studies like this underscore the need for more repre­ sentative and comprehensive research on workers and com­ munities to understand their exposures and potential health risks, " says Aubrey Miller, a senior medical advisor at the National Institute of Environmental Health Sciences. Researchers led by Lisa McKenzie at the Colorado School of Public Health estimated exposure to nat­ ural gas development for nearly 125,000 Colorado women. They used an " inverse distance weight­ ing " method in which they determined the den­ sity of natural gas wells within a 10­mile radius of each mother's home at the time she gave birth, with greater weighting for wells nearer the home. Then they compared proximity to gas wells between mothers who had adverse birth out­ comes—including three types of birth defects, preterm birth, and term low birth weight—and those who did not. Among 59 cases of neural tube defects, prevalence was twice as high among babies of mothers in the highest exposure group—a group of 19 women with more than 125 wells per mile within a 10­mile radius of the home—compared with babies of unexposed mothers. However, there was no evidence that neural tube defects were increased among the 13 babies of mothers classified as having low or medium exposure. Among 1,823 cases of congenital heart defects, prevalence was 30% higher among babies of mothers in the highest exposure group, compared with babies born to unexposed mothers. In contrast to neural tube defects, however, the likelihood of a congenital heart defect increased steadily with increasing exposure. Congenital heart defects are the most common type of birth defect, affecting about 8 of every 1,000 newborns in the United States. 4 There was no association observed between proximity to natural gas development and having babies with an oral cleft. In addition, babies whose mothers experienced the highest exposures to natural gas wells were …