Mothers living near more intense oil and gas development activity have a 40-70% higher chance of having children with congenital heart defects (CHDs) compared to those living in areas of less intense activity, according to a new study from researchers at the Colorado School of Public Health.

“We observed more children were being born with a congenital heart defect in areas with the highest intensity of oil and gas well activity,” said the study’s senior author Lisa McKenzie, PhD, MPH, of the Colorado School of Public Health at the University of Colorado Anschutz Medical Campus.  At least 17 million people in the U.S. and 6% of Colorado’s population live within one mile of an active oil and gas well site.

The study was published today July 18th in the peer-reviewed journal Environment International.

The researchers studied 3,324 infants born in Colorado from 2005-2011. They looked at infants with several specific types of CHDs.