People who live close to fracking sites are exposed to a variety of air pollutants including volatile organic compounds (VOCs) such as benzene, xylene and toluene. These chemicals can cause a wide range of health problems— from eye irritation and headaches to asthma and cancer.

A 2014 Colorado study linked prenatal exposure to fracking chemicals in the air, specifically toluene, xylenes, and benzene, to higher rates of birth defects. Researchers found that the risk of giving birth to infants with congenital heart or neural tube defects increases with proximity to natural gas extraction sites. In fact, children of mothers living within 10 miles of gas wells were 30 percent more likely to be born with congenital heart disease and twice as likely to have a neural tube defect. A large number of people may be at risk of such effects: As of 2013, more than 15 million people in the U.S. lived within one mile of a natural gas well drilled since 2000, and in some areas, such as Johnson County, Texas, 99.5 percent of residents lived within one mile.

Researchers estimated that the lifetime cancer risk is over 30 percent higher for people living within one tenth of a mile of a natural gas extraction site than for those who resided more than a mile away.