Chemicals released during natural gas extraction may harm human reproduction and development.

Unconventional oil and gas (UOG) operations combine directional drilling and hydraulic fracturing, or “fracking,” to release natural gas from underground rock. Recent discussions have focused on potential air and water pollution from chemicals used in these processes and their effects on the more than 15 million Americans living within one mile of UOG operations.

After conducting a review – the largest to date – of more than 150 peer-reviewed studies centred on fracking by-products and their effects on human reproductive and developmental health, researcher Susan C. Nagel and national colleagues determined that exposure to chemicals released in fracking may be harmful to human health, and recommend further scientific study.

“We found previous studies suggest adult and early life exposure to chemicals associated with UOG operations can result in adverse reproductive health and developmental defects in humans,” says Nagel, an associate professor of obstetrics, gynaecology and women’s health in the School of Medicine, and adjunct associate professor of biological sciences in the College of Arts and Science at the University of Missouri.

The “weight of evidence” review of scientific literature and peer-reviewed publications, where studies are scrutinised for patterns and links, includes international studies that focus on UOG chemicals. Reviewers say these chemicals have been measured in air and water near UOG operations, and have been associated with harmful effects in both animals and humans.

“Far fewer human studies than animal studies [have been conducted],” says Nagel. “However, taken together, the studies show humans can be harmed by chemicals released from fracking. There is strong evidence of decreased semen quality in men, higher miscarriages in women and increased risk of birth defects in children.”


Written by Diana Barnett from materials released by University of Missouri-Columbia. Diana is director of SevenCanaries (, a marketplace and information resource for allergy-free and non-toxic living.