A review of more than 150 studies has concluded that exposure to chemicals released in hydraulic fracturing operations may harm human reproduction and development.

Susan C. Nagel, a researcher with the University of Missouri, and national colleagues found that a wide range of research studies suggest that adult and early life exposure to chemicals associated with unconventional oil and gas operations can result in adverse reproductive health and developmental defects in humans.

The "weight of evidence" review of scientific literature and peer-reviewed publications was the largest review to date of research focused on fracking byproducts and their effects on human health. U.S. and international studies on chemicals used in unconventional oil and gas development were examined thoroughly for patterns and links.

The reviewers concluded that exposure to air and water pollution caused by unconventional oil and gas operations may be linked to health concerns including infertility, miscarriage, impaired fetal growth, birth defects and reduced semen quality, the University of Missouri reported.

With many of the air and water pollutants found near unconventional oil and gas sites already recognized as being developmental and reproductive toxicants, there is a compelling need to increase our knowledge of the potential health consequences for infants, children and adults from these chemicals, the reviewers stated.

They recommended biomonitoring of humans and domestic and wild animals for these unconventional oil and gas chemicals, together with systematic and comprehensive epidemiological studies to examine the potential for human harm.