Overview of Chronic Oral Toxicity Values for Chemicals Present in Hydraulic Fracturing Fluids, Flowback, and Produced Waters

Abstract

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, chronic oral reference values (RfVs) for noncancer effects, and oral slope factors (OSFs) for cancer-that are available for a list of 1173 chemicals that the United States (U.S.) Environmental Protection Agency (EPA) identified as being associated with hydraulic fracturing, including 1076 chemicals used in hydraulic fracturing fluids and 134 chemicals detected in flowback or produced waters from hydraulically fractured wells. The EPA compiled RfVs and OSFs using six governmental and intergovernmental data sources. Ninety (8%) of the 1076 chemicals reported in hydraulic fracturing fluids and 83 (62%) of the 134 chemicals reported in flowback/produced water had a chronic oral RfV or OSF available from one or more of the six sources. Furthermore, of the 36 chemicals reported in hydraulic fracturing fluids in at least 10% of wells nationwide (identified from EPA's analysis of the FracFocus Chemical Disclosure Registry 1.0), 8 chemicals (22%) had an available chronic oral RfV. The lack of chronic oral RfVs and OSFs for the majority of these chemicals highlights the significant knowledge gap that exists to assess the potential human health hazards associated with hydraulic fracturing.

Quantity of flowback and produced waters from unconventional oil and gas exploration

“…Several studies have identified and defined different contaminants commonly found in injected hydraulic fracturing fluids based on the chemicals toxicity (Hurley et al, 2016;Kahrilas et al, 2015;McLaughlin et al, 2016;Mohan et al, 2013;Yost et al, 2016a;Yost et al, 2016b).…”

A geospatially resolved database of hydraulic fracturing wells for chemical transformation assessment

“…(v) Toxicity measurements [79][80][81] or estimates, exposure models, 82 and population data could be appended, akin to the EPA's Risk Screening Environmental Indicators (RSEI) model, 83 using FracFocus ingredient disclosures and input in lieu of the Toxic Release Inventory (TRI).…”

Salting the Earth: The Environmental Impact of Oil and Gas Wastewater Spills

“…Produced water may still contain small amounts of fracking chemicals 9 . It will also typically contain a number of potentially toxic agents that occur naturally in the rock formation, which can include radioactive isotopes, organic compounds (such as benzene), ions (such as bromide, calcium, and chloride), and metals (such as cadmium, lead, and mercury) 10 .…”

“…A recent analysis showed that only 8% of the 1,076 chemicals listed as being used in fracking fluids and 62% of the 134 chemicals documented in flowback and produced water had sufficient toxicological data to calculate chronic oral toxicity values 9 . These are values that estimate the amount of a chemical that can be ingested daily without appreciable risk of health effects.…”