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On October 29, 2019, the U.S. Environmental Protection Agency (EPA) announced the availability of the draft Toxic Substances Control Act (TSCA) risk evaluation for methylene chloride (MC). It provides important insights into how the EPA is interpreting the new risk evaluation provisions of the new TSCA. We explain why and how below.
Amended TSCA Section 6 requires the EPA to conduct risk evaluations to determine whether a chemical substance, under its conditions of use, presents an unreasonable risk of injury to health or the environment. The leading applications for MC include as a solvent in the production of pharmaceuticals and polymers, metal cleaning, production of HFC-32 (refrigerant blend), and as an ingredient in adhesives and paint removers. The EPA evaluated several categories of conditions of use: manufacturing; processing; distribution in commerce; industrial, commercial, and consumer uses; and disposal.
Draft Unreasonable Risk Determinations
The EPA’s initial determinations of unreasonable risk for the specific conditions of use of MC listed below are based on health risks to workers, occupational non-users (ONU), consumers and bystanders from consumer use. According to the draft risk evaluation, risks to the general population either were not relevant for these conditions of use or evaluated and not found to be unreasonable.
The EPA identified exposure pathways covered under the jurisdiction of other federal statutes regulating chemical exposures, administered by the EPA, that “adequately assess and effectively manage exposures and for which long-standing regulatory and analytical processes already exist,” i.e., the Clean Air Act (CAA), Safe Drinking Water Act (SDWA), Clean Water Act (CWA), and Resource Conservation and Recovery Act (RCRA). Importantly, the draft risk evaluation states that the EPA believes the TSCA risk evaluation should focus on exposure pathways associated with TSCA uses not subject to other regulatory programs because these pathways likely represent the greatest areas of concern to the EPA.
The EPA also evaluated workers’ inhalation and dermal occupational exposures for cancer and non-cancer risks and determined whether any risks indicated are unreasonable. Drivers for the EPA’s unreasonable risk determination for workers are central nervous system effects resulting from acute inhalation exposure and liver toxicity from chronic inhalation exposure. The EPA determined that processing MC into a formulation or mixture, all but two industrial and commercial uses, and disposal all presented unreasonable risks.
For consumers, the EPA determined all but two consumer conditions of use present unreasonable risks. The EPA evaluated consumer acute inhalation and dermal exposures for non-cancer risks and determined whether the risks indicated are unreasonable. Generally, acute inhalation and dermal exposure at medium and high intensity use indicated risks for consumers. Acute inhalation exposure scenarios at uses deemed to be of medium and high intensity indicated risks for bystanders. Because bystanders are not expected to be dermally exposed to MC, the EPA did not identify dermal non-cancer risks to bystanders.
The EPA is submitting the draft to the TSCA Science Advisory Committee on Chemicals (SACC) for peer review. The SACC will convene an in-person public meeting to consider and review the draft risk evaluation on December 3–4, 2019. Comments on the draft risk evaluation are due December 30, 2019.
Discussion
The MC risk evaluation is interesting for several reasons, including the presence of a risk assessment for MC from 2014 and regulatory actions regarding paint and coating removal use. The risk issues identified by the EPA go beyond the paint and coating removal use that was the initial focus of previous regulatory efforts. In its approach to general population risk, the EPA believes regulations under other environmental statutes sufficiently assess and effectively manage general population exposures. Based on this position, the EPA didn’t include those aspects in its risk evaluation and did not make a general population risk determination. This finding is expected to generate significant comment.
Also worth noting is that the new risk evaluation includes risk conclusions concerning MC’s environmental effects; this is expected to generate controversy. The earlier risk assessment did not consider the environmental impact.
How these issues eventually resolve will provide an informative template on similar exposure issues in other risk evaluations. It’s more likely than not whatever the final rule, litigation will almost certainly be in its future.
