Development of an oral reference dose for the perfluorinated compound GenX.

Ammonium 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate, also known as GenX, is a processing aid used in the manufacture of fluoropolymers. GenX is one of several chemistries developed as an alternative to long-chain poly-fluoroalkyl substances, which tend to have long clearance half-lives and are environmentally persistent. Unlike poly-fluoroalkyl substances, GenX has more rapid clearance, but has been detected in US and international water sources. There are currently no federal drinking water standards for GenX in the USA; therefore, we developed a non-cancer oral reference dose (RfD) for GenX based on available repeated dose studies. The review of the available data indicate that GenX is unlikely to be genotoxic. A combination of traditional frequentist benchmark dose models and Bayesian benchmark dose models were used derive relevant points of departure from mammalian toxicity studies. In addition, deterministic and probabilistic RfD values were developed using available tools and regulatory guidance. The two approaches resulted in a narrow range of RfD values for liver lesions observed in a 2-year bioassay in rats (0.01-0.02 mg/kg/day). The probabilistic approach resulted in the lower, i.e., more conservative RfD. The probabilistic RfD of 0.01 mg/kg/day results in a maximum contaminant level goal of 70 ppb. It is anticipated that these values, along with the hazard identification and dose-response modeling described herein, should be informative for risk assessors and regulators interested in setting health-protective drinking water guideline values for GenX.

Bounding Analysis of Drinking Water Health Risks from a Spill of Hydraulic Fracturing Flowback Water.

A bounding risk assessment is presented that evaluates possible human health risk from a hypothetical scenario involving a 10,000-gallon release of flowback water from horizontal fracturing of Marcellus Shale. The water is assumed to be spilled on the ground, infiltrates into groundwater that is a source of drinking water, and an adult and child located downgradient drink the groundwater. Key uncertainties in estimating risk are given explicit quantitative treatment using Monte Carlo analysis. Chemicals that contribute significantly to estimated health risks are identified, as are key uncertainties and variables to which risk estimates are sensitive. The results show that hypothetical exposure via drinking water impacted by chemicals in Marcellus Shale flowback water, assumed to be spilled onto the ground surface, results in predicted bounds between 10-10 and 10-6 (for both adult and child receptors) for excess lifetime cancer risk. Cumulative hazard indices (HICUMULATIVE ) resulting from these hypothetical exposures have predicted bounds (5th to 95th percentile) between 0.02 and 35 for assumed adult receptors and 0.1 and 146 for assumed child receptors. Predicted health risks are dominated by noncancer endpoints related to ingestion of barium and lithium in impacted groundwater. Hazard indices above unity are largely related to exposure to lithium. Salinity taste thresholds are likely to be exceeded before drinking water exposures result in adverse health effects. The findings provide focus for policy discussions concerning flowback water risk management. They also indicate ways to improve the ability to estimate health risks from drinking water impacted by a flowback water spill (i.e., reducing uncertainty).

Exposure monitoring toward environmental justice.

Executive Order 14008, signed on 27 January 2021, established environmental justice (EJ) as a core priority of the Biden Administration. There is a need for state and federal regulators, as well as industry, to enhance risk assessment methods and exposure monitoring approaches to be more inclusive of EJ community involvement and more representative of EJ community exposures. Cumulative risk assessment models are critical for understanding the unique interaction between chemical exposures and nonchemical stressors that EJ communities encounter daily. Enhanced environmental monitoring with personal and portable sensors, especially when deployed using community partnerships, can capture chemical exposures with sufficient resolution to characterize exposures down to the neighborhood level. Use of internet-linked sensors will also require thoughtful advances in management of big data to inform meaningful and time-sensitive decisions. Integr Environ Assess Manag 2022;18:858-862. © 2021 SETAC.

Radiation exposures from the beneficial use of alumina production residue.

Estimates of radiation exposure are developed over the life cycle of beneficial use in cement of an alumina production residue (APR) waste pile. The life cycle includes radiation exposures that might be experienced by industrial workers involved in excavation and transport of the residue to cement plants, industrial workers at the cement plants, construction workers making use of the cement, members of the public who might be in the proximity of the cement products, and disposal of the cement at the end of its useful life. The results indicate that it is not reasonably likely for exposures related to beneficial use of APR waste in cement to exceed the acceptance criteria delineated in current radiation protection standards for workers and members of the general public.Implications: Radiation exposure estimates developed over the life cycle of beneficial use in cement of an alumina production residue (APR) waste pile indicate that it is not reasonably likely for exposures to exceed the acceptance criteria delineated in current radiation protection standards for workers and the public. Assumed APR waste characteristics, storage, transport, cement production, uses in concrete, and ultimate disposal are generalizable to many APR situations. The findings demonstrate that beneficial use of APR waste as a cement ingredient can be accomplished safely, with potentially significant benefits to management of the large volume of APR being stored around the world.