/>iOn December 23, 2020, the U.S. Environmental Protection Agency (EPA) released the final risk evaluation for N-methylpyrrolidone (NMP). Of the 37 conditions of use that EPA reviewed, EPA found that 26 present unreasonable risks to workers and consumers. These uses include an unreasonable risk to workers when domestically manufacturing or importing NMP, processing NMP for a variety of uses, and when used in a variety of industrial and commercial conditions of use. These uses also include an unreasonable risk to consumers from one consumer use. EPA found that NMP does not pose an unreasonable risk when distributed in commerce or in a variety of industrial and commercial and consumer applications. EPA also determined that NMP does not present an unreasonable risk to the environment and the general population.
The next step in the process required by the Toxic Substances Control Act (TSCA) is for EPA to develop a plan to reduce or eliminate the unreasonable risks found in the final risk evaluation. EPA states that it “is moving immediately to risk management for this chemical and will work as quickly as possible to propose and finalize actions to protect against the unreasonable risks.” The potential actions that EPA could take to address these risks include regulating how NMP is used or limiting or prohibiting the manufacture, processing, distribution in the marketplace, use, or disposal of NMP, as applicable. As with any chemical product, EPA “strongly recommends that users of products containing NMP continue to carefully follow all instructions on the product’s label and safety data sheet.”
Background
TSCA Section 6, as amended by the Frank R. Lautenberg Chemical Safety for the 21st Century Act (Lautenberg Act), requires EPA to conduct risk evaluations to “determine whether a chemical substance presents an unreasonable risk of injury to health or the environment, without consideration of costs or other nonrisk factors, including an unreasonable risk to a potentially exposed or susceptible subpopulation identified as relevant to the risk evaluation by the Administrator, under the conditions of use.” The statute identifies the minimum components EPA must include in all risk evaluations. For each risk evaluation, EPA must publish a document that outlines the scope of the risk evaluation to be conducted, which includes the hazards, exposures, conditions of use, and the potentially exposed or susceptible subpopulations that EPA expects to consider. Each risk evaluation must also: (1) integrate and assess available information on hazards and exposure for the conditions of use of the chemical substance, including information on specific risks of injury to health or the environment and information on relevant potentially exposed or susceptible subpopulations; (2) describe whether aggregate or sentinel exposures were considered and the basis for that consideration; (3) take into account, where relevant, the likely duration, intensity, frequency, and number of exposures under the conditions of use; and (4) describe the weight of the scientific evidence for the identified hazards and exposure. The risk evaluation must not consider costs or other nonrisk factors. A detailed summary and analysis of the final risk evaluation rule is available in our June 26, 2017, memorandum, “EPA Issues Final TSCA Framework Rules.”
Risk Evaluation for NMP
EPA evaluated acute and chronic human exposures by the dermal and inhalation routes, including direct contact with NMP-containing liquids and indirect exposure from vapor-through-skin uptake. For each worker occupational use scenario, EPA considered moderate- and high-end exposure parameters and the impact of different combinations of personal protective equipment (PPE) on exposure. EPA states that it preferred empirical data for exposure estimation when reasonably available. In the absence of measured data, EPA used models to estimate exposure to the human receptors of interest. EPA estimated exposure to individuals located near those using NMP-containing products (i.e., ONUs) based on inhalation and vapor-through-skin uptake.
EPA estimated acute exposures to consumers and to adult and child bystanders. According to the final risk evaluation, because reasonably available information does not indicate that chronic exposures would occur during the use of the consumer products identified as containing NMP, EPA did not evaluate chronic consumer exposures. EPA varied the following input parameters: the activity pattern of the consumer in using the product (including the location or room of use), the duration of use, and the mass of the product used to quantify the amount of NMP exposure to consumers. The final risk evaluation states that EPA selected not only median but also high-end input parameters to develop high-intensity use scenarios to capture the exposures to those consumers who may use the products in greater quantities and for a longer duration.
The final risk evaluation notes that EPA did not identify any “legacy uses” (i.e., circumstances associated with activities that do not reflect ongoing or prospective manufacturing, processing, or distribution) or “associated disposal” (i.e., future disposal from legacy uses) of NMP. Therefore, EPA did not add any such uses or disposals to the scope of the risk evaluation for NMP following the issuance of the opinion in Safer Chemicals, Healthy Families v. EPA. The final risk evaluation states that EPA did not evaluate “legacy disposal” (i.e., disposals that have already occurred) in the risk evaluation “because legacy disposal is not a ‘condition of use’ under Safer Chemicals.”
EPA made the following risk evaluation findings. EPA stated that in making these unreasonable risk determinations, it considered the hazards and exposure, magnitude of risk, exposed population, severity of the hazard, uncertainties, and other factors.
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EPA found no unreasonable risks to the environment from any conditions of use. EPA assessed the impact of NMP on aquatic, sediment-dwelling species through surface water and sediment exposures and on terrestrial species. After reviewing these data, EPA found no unreasonable risk to the environment.
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EPA found no unreasonable risks to the general population from any conditions of use. The general population could be exposed to NMP either through releases to water and air or through waste disposal. EPA found that it was unlikely the general population would be exposed to NMP through surface water, land-applied biosolids, and sediment.
Potential exposure to NMP in ambient air and hazardous waste are under the jurisdiction of other EPA-administered statutes like the Clean Air Act (CAA) and the Resource Conservation and Recovery Act (RCRA). Therefore, these exposure pathways are not part of this risk evaluation. EPA evaluated acute incidental exposures from ambient water and determined that this presents no unreasonable risk to the general population from all conditions of use of NMP.
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EPA found unreasonable risks to human health from 26 out of 37 conditions of use of NMP:
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Consumers: EPA found an unreasonable risk to consumers from one consumer use of NMP (in adhesives and sealants). Risks to consumers can come from short-term inhalation, direct dermal exposure, and vapor-through-skin exposure. Other consumer uses include in automotive care products, adhesive removers, cleaning and furniture care products, and arts and craft paint; and
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Workers: EPA found unreasonable risks to workers from 25 conditions of use of NMP. EPA states that NMP is commonly used commercially in the manufacture and production of electronics, agrichemicals, and petroleum products. Risks to workers can come from short-term and long-term inhalation, direct dermal exposure, and vapor-through-skin exposure.
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Commentary
With the issuance of the final risk evaluation for NMP, risk management efforts will now commence covering the conditions of use for which EPA found unreasonable risk. A final Section 6(a) regulation is required to be issued within three and one half years, including potentially available extensions. In addition, for the conditions of use that were determined not to present an unreasonable risk, these decisions, which EPA issued by order under Section 6(i)(1) of TSCA, represent final agency actions that are subject to legal challenge. Generally consistent with the other risk evaluations issued to date, EPA did not evaluate certain hazards or exposures to the general population in the risk evaluation (i.e., from drinking water and disposal pathways) because those exposures fall under the jurisdiction of other environmental statutes administered by EPA. As a result, the unreasonable risk determinations for the relevant conditions of use do not account for these exposures to the general population. Considering the legal challenges filed to date on the Section 6(i)(1) orders issued as part of final risk evaluations on methylene chloride and the cyclic aliphatic bromide cluster (HBCD), legal challenges to the order may arise for the conditions of use that EPA determined do not present an unreasonable risk for reasons including EPA’s exclusion of certain general population exposure pathways.
There are substantial changes in the calculated Margins of Exposure (MOE) between the draft and final risk evaluations leading to many more conditions of use that EPA identified as unreasonable risk. EPA’s calculation of an MOE depends on both the Point of Departure (POD) (the level to which EPA will compare exposures) divided by the measured or predicted exposures. EPA then compares the calculated MOE to a benchmark MOE (that represents EPA’s uncertainty). If the calculated MOE is below the benchmark, EPA flags that condition of use as an unreasonable risk. In short, higher MOEs indicate lower potential for risk. EPA’s calculated MOEs went down substantially -- generally four- to tenfold -- between the draft and final risk evaluation. As a result, EPA’s prediction of unreasonable risk went from being limited mostly to scenarios without PPE and/or high-end exposures to most conditions of use for workers. This significant change in EPA’s calculation of unreasonable risk warrants careful scrutiny.
In response to peer review comments, EPA’s view of the POD changed in the final risk evaluation largely due to EPA’s view of the studies by Saillenfait et al. As a result, EPA increased the acute POD by a factor of about 2. Increasing the POD should increase the calculated MOE and reduce the likelihood of unreasonable risk. EPA also updated its exposure calculations and, in most cases, exposure predictions were the same as or lower than in the draft risk evaluation. Lower exposure also increases the MOE and reduces the likelihood of unreasonable risk. Despite the higher POD and (mostly) the same or lower exposures, most of the MOEs in the final risk evaluation are lower than in the draft. These differences may be due to changes in EPA’s physiologically based pharmacokinetic (PBPK) model or an arithmetic error in the calculations of the MOEs. Stakeholders should review carefully the underlying science and calculations to understand better this significant change in EPA’s calculations of the MOEs.
Consumers (and retailers) can take some comfort from the fact that in the final risk evaluation, EPA identified few conditions of use that present unreasonable risk outside of the workplace. EPA identified three uses in which high-intensity users might experience unreasonable risk: paint removers (8 hr/day), high weight fraction adhesives and sealants (1 hr/day), and engine cleaner/degreasers (2 hr/day). Furthermore, while EPA’s calculated MOEs are below the benchmark MOE, the calculated MOEs were not substantially below the benchmark, suggesting that the unreasonable risk is only present at the very highest consumer exposure scenarios.
Regardless of the source of the change of the MOEs, EPA’s risk evaluation reinforces the critical importance of strong industrial hygiene practices, including evidence-based selection of gloves that are impervious to the substance and training on how to don and doff PPE to prevent unintended exposures.
Under TSCA Section 6(b)(4), EPA has three years to complete a risk evaluation, extendable for an additional six months; the deadline for the issuance of the risk evaluations for the “first ten” chemicals selected for risk evaluation under Section 6(b)(2)(A), as extended by six months by EPA, was June 19, 2020. EPA has to date completed risk evaluations on six of the “first ten” chemicals selected for risk evaluation under Section 6(b)(2)(A): methylene chloride, 1-bromopropane, HBCD, carbon tetrachloride, trichloroethylene, perchloroethylene, and now, NMP. EPA has stated that the remaining risk evaluations on the “first ten” chemicals are expected by the end of 2020; this includes risk evaluations on 1,4-dioxane, asbestos, and Colour Index (C.I.) Pigment Violet 29. Considering that the comment period for the supplemental analysis to the draft risk evaluation for 1,4-dioxane ended on December 10, 2020, that the comment period for the revised draft risk evaluation for C.I. Pigment Violet 29 ended on December 19, 2020, and the holiday time of the year, EPA’s issuance of these remaining three final risk evaluations by the end of the year is unlikely.
