Overview of Chronic Oral Toxicity Values for Chemicals Present in Hydraulic Fracturing Fluids, Flowback and Produced Waters
As the use of hydraulic fracturing has increased, concerns have been raised about potential public health effects that may arise if hydraulic fracturing-related chemicals were to impact drinking water resources. This study presents an overview of the chronic oral toxicity values—specifically, noncancer oral reference values (RfVs) and cancer oral slope factors (OSFs)—that are available for a list of 1,173 chemicals that the United States (US) Environmental Protection Agency (EPA) identified as being used in hydraulic fracturing fluids or detected in flowback or produced waters. The EPA compiled RfVs and OSFs for these chemicals using six governmental and intergovernmental data sources, including four US federal databases. Of the 1,173 chemicals, 147 (13%) had a chronic oral RfV or OSF available from one or more of the six sources. Furthermore, of the 36 chemicals that are used in at least 10% of wells nationwide (identified from the EPA’s analysis of the FracFocus Chemical Disclosure Registry 1.0 database), 8 chemicals (22%) have an available chronic oral RfV. Potential health effects associated with these frequently used chemicals include kidney/renal toxicity, hepatotoxicity, developmental toxicity, reproductive toxicity, and decreased terminal body weight. The lack of chronic oral RfVs and OSFs for the majority of these chemicals highlights the significant knowledge gaps that exist to assess the potential human health hazards associated with hydraulic fracturing.