Researchers had information on reproductive and developmental toxicity for only 24 percent of over 1,000 chemicals they looked at.
Add this to the body of evidence suggesting that the unconventional oil and gas extraction technique known as fracking poses risks to public health.
In a study published Wednesday, researchers at the Yale School of Public Health looked at over 1,000 chemicals in hydraulic-fracturing ﬂuids or wastewater, and found that over 150 of them were linked to potential reproductive or developmental harm.
Those chemicals include arsenic, benzene, lead, formaldehyde, and mercury.
The study, published in the Journal of Exposure Science and Environmental and Epidemiology, also underscores the many unknowns regarding the adverse effects of fracking.
The Yale team was able to obtain information on potential reproductive and developmental toxicity for a small portion 240 of the 1,021 chemicals; for the majority—76 percent—of the chemicals, no such information was available.
"Thus, we were able to evaluate reproductive and/or developmental toxicity for only 24% of chemicals," the researchers write.
While they obtained the list over over 1,00 chemicals from the EPA, the researchers point out that "the exact composition of fracturing ﬂuids remains unknown because chemicals and their concentrations may be classiﬁed as conﬁdential business information."
The "lack of a clear target list of chemicals" used in the fracking process, therefore, presents "a major challenge to conduct efﬁcient and well-designed human exposure assessments," the study states.
Still, based on their study, the researchers write that the substances and processes used in fracking "indicate the potential for reproductive and developmental health risks."
"This evaluation is a first step to prioritize the vast array of potential environmental contaminants from hydraulic fracturing for future exposure and health studies," Nicole Deziel, senior author and assistant professor of public health, said in a media statement. "Quantification of the potential exposure to these chemicals, such as by monitoring drinking water in people's homes, is vital for understanding the public health impact of hydraulic fracturing."
"There's still many unanswered questions," she told the New Haven Register. "We (still) don’t know what aspect of hydraulic fracturing is likely to be most harmful."