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December 28, 2023

EPA Begins TSCA Prioritization Process for Five Chemicals, Requires Reporting on MBOCA

The ACTA Group

The U.S. Environmental Protection Agency (EPA) announced on December 18, 2023, that it is beginning the process to prioritize five additional toxic chemicals for risk evaluation under the Toxic Substances Control Act (TSCA). 88 Fed. Reg. 87423. The chemicals are acetaldehyde, acrylonitrile, benzenamine, 4,4’-methylene bis(2-chloroaniline) (MBOCA), and vinyl chloride. EPA seeks relevant information, including but not limited to, the chemical substance’s hazard and exposure potential; the chemical substance’s persistence and bioaccumulation; potentially exposed or susceptible subpopulations relevant to the prioritization; whether there is any storage of the chemical substance near significant sources of drinking water; the chemical substance’s conditions of use or significant changes in conditions of use, including information regarding trade names; the chemical substance’s production volume or significant changes in production volume; and any other information relevant to the potential risks of the chemical substance that might be relevant to the designation of the chemical substance’s priority for risk evaluation. Comments are due March 18, 2024. EPA has opened a chemical-specific docket for each of the five chemicals.

EPA’s December 14, 2023, press release includes the following information regarding the five chemicals:

  • Acetaldehyde is primarily used in the manufacturing and processing of adhesives, petrochemicals, and other chemicals, as well as intermediates for products like packaging and construction materials. Exposure to acetaldehyde may result in a range of health effects such as irritation of the respiratory system. It is a probable human carcinogen.
  • Acrylonitrile is primarily used in the manufacturing and processing of plastic materials, paints, petrochemicals and other chemicals. Exposure to acrylonitrile may result in a range of health effects such as irritation of the respiratory system. It is a probable human carcinogen.
  • Benzenamine is used in the manufacturing and processing of dyes and pigments, petrochemicals, plastics, resins, and other chemicals. Exposure to benzenamine may result in a range of health effects such as adverse effects on the blood, fetal development, and reproduction. Benzenamine is a probable human carcinogen.
  • MBOCA is used in the manufacturing and processing of rubbers, plastics, resins, and other chemicals. It is a probable human carcinogen. There is also extensive data that demonstrate exposure to MBOCA may damage genetic material in cells, potentially leading to other adverse health effects, particularly when exposure occurs to infants and children.
  • Vinyl chloride is primarily used in the manufacturing and processing of plastic materials like polyvinyl chloride (PVC), plastic resins, and other chemicals, and many of these materials are used for pipes, insulating materials, and consumer goods. This chemical was also involved in the Norfolk Southern train derailment in East Palestine, Ohio. Exposure to vinyl chloride may result in a range of health effects, such as liver toxicity. It is also a known human carcinogen. In the 1970s, the White House Council on Environmental Quality and EPA officials raised serious concerns about the health impacts of vinyl chloride. These concerns were the impetus for Congress to write a law to ensure chemicals were made and used safely, which led to passage of the “original” TSCA in 1976.

EPA states that it selected all five chemicals from the 2014 TSCA Work Plan, “which is a list of chemicals identified by EPA for further assessment based on their hazards and potential for exposure.” According to EPA, between September and November 2023, it met with federal partners, industry, environmental organizations, labor organizations, state and local governments, and Tribes to discuss the prioritization process and presented a list of 15 chemicals that EPA was considering for prioritization. EPA took feedback from these discussions into consideration when selecting the five chemicals for prioritization. The ten chemicals not selected include: 4-tert-Octylphenol(4-(1,1,3,3-Tetramethylbutyl)-phenol); benzene; bisphenol A; ethylbenzene; naphthalene; styrene; tribromomethane; triglycidyl isocyanurate; hydrogen fluoride; and N-(1,3-Dimethylbutyl)-N’-phenyl-p-phenylenediamine. The Federal Register notice states that interested persons may submit relevant information on these ten chemicals by using Docket ID No. EPA-HQ-OPPT-2023-0606.

According to EPA’s press release, “[a]lthough EPA expects these chemicals to be designated as high-priority for risk evaluation during the prioritization process, EPA will continue to review and screen reasonably available and submitted information to make a final designation.” Going forward, EPA states that it expects to initiate prioritization on five chemicals every year, “which will create a sustainable and effective pace for risk evaluations.”

On December 21, 2023, EPA announced that it is requiring chemical companies to submit records of significant adverse human health and environmental effects reported to have been caused by MBOCA. EPA states that under TSCA Section 8(c), chemical companies must maintain records of reports about a chemical’s harm to human health or the environment. According to EPA, this recordkeeping requirement “includes records of employee health-related effects reported to companies over the last 30 years, public reports of other health-related harm for the previous five years, and reports of harm related to animals, plants, and the environment for the past five years.” EPA is using its TSCA Section 8(c) authority to request copies of these records. EPA notes that it may use this authority to collect data on one or more of the other five chemicals undergoing prioritization “in the coming months.” Records are due to EPA by February 26, 2024. 88 Fed. Reg. 88915.


The Acta Group (Acta®) was not surprised by EPA’s selection of these five chemical substances for prioritization. After all, each of these substances has undergone evaluation by various expert bodies, including the International Agency for Research on Cancer (IARC), and was determined to have carcinogenic potential to humans with varying levels of confidence. For example, IARC classified acetaldehyde and acrylonitrile as “Possibly carcinogenic to humans,” benzenamine (aniline) as “Probably carcinogenic to humans,” and vinyl chloride and MBOCA as “Carcinogenic to humans.” These substances are also high production volume (HPV) chemicals (i.e., produced or imported in quantities of > 1 million pounds per year), as shown below.

2020 Nationally Aggregated Production Volume
Acetaldehyde100,000,000 – <1,000,000,000100,000,000 – <1,000,000,000100,000,000 – <1,000,000,000100,000,000 – <1,000,000,000
Acrylonitrile1,000,000,000 – <5,000,000,0001,000,000,000 – <5,000,000,0001,000,000,000 – <5,000,000,0001,000,000,000 – <5,000,000,000
Benzenamine1,000,000,000 – <5,000,000,0001,000,000,000 – <5,000,000,0001,000,000,000 – <5,000,000,0001,000,000,000 – <5,000,000,000
Vinyl Chloride10,000,000,000 – <20,000,000,00010,000,000,000 – <20,000,000,00010,000,000,000 – <20,000,000,00010,000,000,000 – <20,000,000,000
MBOCA1,000,000 – <10,000,0001,000,000 – <10,000,0001,000,000 – <10,000,0001,000,000 – <10,000,000
a EPA (2020) 2020 CDR Data.

Further, these substances were identified by EPA as components used with making plastics, which may have aided EPA with narrowing its list for prioritization, given EPA’s initiatives aimed at preventing plastic pollution. We, therefore, expect EPA to designate each of these substances as high-priority substances (HPS). We summarize below potential outcomes for these five substances, should EPA designate them as HPSs. Thereafter, we discuss related activities EPA recently announced that will directly impact one and possibly all five of the potential HPSs and all chemical substances that EPA designates as HPSs.

Acta notes that if and when EPA designates these five chemical substances as HPSs, the eventual proposed regulatory actions are predictable once EPA completes its risk evaluations: each presents unreasonable risk to human health or the environment under EPA’s “whole chemical” approach. EPA will then propose risk management that includes outright prohibitions, workplace chemical protection programs (WCPP) that include existing chemical exposure limits (ECEL) for those uses not prohibited, and time-limited uses that require compliance with the WCPPs. For discussion, see our memoranda on EPA’s proposed risk management options on asbestos dated April 7, 2022, methylene chloride dated April 25, 2023, and trichloroethylene dated November 3, 2023,

Acta made some back-of-the-envelope calculations conservatively to estimate what the cancer-based ECELs may end up being if the five substances are designated as HPSs, undergo TSCA risk evaluations with findings that they present unreasonable risks, and are subjected to risk management. These values are shown below in comparison to existing U.S. occupational exposure limits (OEL).

Chemical SubstanceCAS RNExisting OELsCancer-based ECELs
Acetaldehyde75-07-0OSHA PEL TWA: 360 mg/m30.09 mg/m3
Acrylonitrile107-13-1NIOSH REL TWA: 2.17 mg/m3; OSHA PEL TWA: 4.34 mg/m30.003 mg/m3
Benzenamine (Aniline)62-53-3OSHA PEL TWA: 19 mg/m30.24 mg/m3
Vinyl Chloride75-01-4OSHA PEL TWA: 2.56 mg/m30.02 mg/m3
MBOCA101-14-4NIOSH REL TWA: 0.003 mg/m30.0005 mg/m3

We caution readers that EPA can be expected to propose prohibitions on these substances if occupational monitoring data are not provided to EPA to ensure that the regulated community can comply with EPA’s WCPPs, including any proposed ECELs. Further, if EPA’s prioritization of these substances is intended to further initiatives at preventing plastic pollution, proposals to outright prohibit these substances cannot be far behind.

Beyond its prioritization activities, we also note that EPA expanded use of its information gathering authorities under TSCA for at least one of the substances undergoing prioritization (i.e., MBOCA). Under TSCA Section 8(c) and the implementing regulations at 40 C.F.R. Part 717, manufacturers (including importers), processors, and distributors of chemical substances must maintain “records of significant adverse reactions to health or the environment…alleged to have been caused by the substance or mixture.” Regulated entities must also provide these records to EPA if requested. On December 26, 2023, EPA published such a request for records on MBOCA with a due date for submission to EPA on or before February 26, 2024. It is unusual for EPA to require TSCA Section 8(c) reporting for a substance. EPA typically only reviews Section 8(c) reports during an inspection or audit. EPA did not explain why it expects there to be Section 8(c) reports for MBOCA, but not any of the other substances it has evaluated or intends to consider. It remains unclear, as of the time of our posting, whether EPA will issue requests for TSCA Section 8(c) reports on the other four chemical substances undergoing prioritization or if EPA will issue TSCA Section 8(d) data call-ins for each.

EPA’s prioritization announcement provides insight on its future prioritization activities. For example, EPA’s intent to initiate prioritization on five chemical substances each year suggests that the 2024 and 2025 lists may contain one or more of the remaining ten chemical substances that EPA evaluated as potential candidates for prioritization. We mention this because entities that have those chemical substances in their supply chain should be mindful of this and initiate data gathering and generation, as needed, well in advance of EPA’s future announcements.

Finally, Acta notes EPA’s second notice on December 26, 2023, requesting nominations of ad hoc expert reviewers to serve on EPA’s Science Advisory Committee on Chemicals (SACC) for peer reviewing EPA’s draft risk evaluation for formaldehyde. The notice states that EPA plans to announce in a separate notice “a 4-day public meeting of the SACC anticipated to be scheduled for May 2024.” At first glance and even after an in-depth review of the December 26, 2023, notice, it may seem completely unrelated to the five chemical substances undergoing prioritization or to EPA’s other risk evaluation activities. We mention this notice because it serves as an important cautionary reminder that we routinely provide to regulated entities, that is, to be aware of EPA’s activities on existing chemical substances under TSCA Section 6. For further discussion, see our memorandum dated December 21, 2023.

EPA’s notice on formaldehyde included several important points. EPA indicated that it does not plan to peer review parts of the draft risk evaluation for formaldehyde. For example, EPA stated that “[f]or chronic inhalation exposure and the cancer inhalation unit risk (IUR), the Agency intends to deter to the draft 2012 Integrated Risk Information System [IRIS] Toxicological Review of Formaldehyde and associated 2023 review by the NASEM [National Academies of Sciences, Engineering, and Medicine].” We mention this for two reasons. First, it demonstrates that EPA intends to implement its amendments to the proposed risk evaluation framework rule, prior to considering public comments (e.g., the public comment period closed on December 14, 2023). Second, EPA and other organizations have published health and/or risk assessments on each of the five substances undergoing prioritization. We previously cautioned about the potential for “cherry picking” under such circumstances, that is, when assessments are incorporated without justification nor subsequent peer review by the SACC. For discussion, see our memorandum dated October 30, 2023. We also note that the NASEM peer review of the IRIS assessment on formaldehyde is the subject of litigation due to alleged violations of the Federal Advisory Committee Act, which would favor having the SACC peer review all parts of the IRIS Toxicological Review of Formaldehyde.

EPA’s notice on formaldehyde also stated:

[T]he Agency is not intending to request review on the modeling methods used to estimate formaldehyde exposure in ambient (outdoor) air as the methods used have been previously peer reviewed. SACC already reviewed both the Draft TSCA Screening Level Approach for Assessing Ambient Air and Water Exposures to Fenceline Communities, Version 1.0 [the 2022 Fenceline Draft] and the 2023 Draft Supplement to the 1,4-Dioxane Risk Evaluation [the 2023 Draft 1,4-DX RE]. Furthermore, feedback from these reviews have been incorporated into the draft formaldehyde risk assessment.

We note that EPA has yet to issue the 2022 Fenceline Draft in final, nearly one year after it was first released (i.e., January 2022) and later peer reviewed by the SACC, which expressed concerns about the approach. For example, the SACC stated:

The accuracy and/or completeness of the data used to develop the screening analysis was not adequately supported in the document, the Committee decided it did not defensibly represent actual fenceline communities.

Second, the SACC issued its final report on the 2023 Draft 1,4-DX RE on November 16, 2023, yet EPA already incorporated the SACC’s feedback into the draft formaldehyde risk assessment? We find this remarkable.

We mention the above issues and lack of transparency with the 2022 Fenceline Draft and 2023 Draft 1,4-DX RE because these evaluations were based on models that were not peer reviewed by the SACC to ensure they were fit-for-purpose prior to using the models in TSCA risk evaluations. We anticipate that EPA will continue to use these same models for evaluating the five chemical substances undergoing prioritization if (when) they are designated as HPSs.

Acta encourages interested parties to review EPA’s list of chemical substances identified for prioritization and to provide comments and data, as appropriate. We believe that EPA will designate these substances as HPSs and initiate the risk evaluation process. We encourage entities that use these chemical substances to engage with EPA quickly on potential data needs to ensure that the Agency has as complete of an understanding as possible of the engineering controls, exposures, and related considerations. In the absence of representative data to inform these components of conditions of use in a risk evaluation, EPA will use conservative modeling defaults and/or data that may not be representative of current practices.