In analyzing 1,021 chemicals contained in fluids and wastewater used in hydraulic fracturing (fracking) for oil or natural gas, a Yale University study found that at least 157 of the chemicals—including arsenic, benzene, formaldehyde and mercury—are associated with either developmental toxicity, reproductive toxicity or both.

Of the total identified chemicals, 925 were used in the hydraulic fracturing process, 132 in fracking wastewater and 36 were present in both. The scientists utilized the REPROTOX database in the Chemical Abstract Service registry and then reviewed the available research, including human and animal studies.

Toxicity data wasn’t available for 781 of the chemicals used in fracking. Among the other 240 chemicals, 103 were reproductive toxins. An additional 95 were developmental toxins. Another 41 have been found to be both reproductive and developmental toxins. The researchers further suggested that at least 67 of the chemicals be prioritized in drinking water testing.

Senior author and Professor of Public Health Nicole Deziel, Ph.D., adds, “This evaluation is a first step to prioritize the vast array of potential environmental contaminants from hydraulic fracturing for future exposure and health studies. Quantification of the potential exposure to these chemicals, such as by monitoring drinking water in people’s homes, is vital for understanding the [associated] public health impact.”