Chemicals and Ethylene Oxide Lookahead

Continuing the momentum of the past several years as the United States Environmental Protection Agency (U.S. EPA) is conducting its required periodic reviews of air rules, 2025 promises to bring additional changes to regulations for the chemical industry, including users of ethylene oxide (EtO). This article mainly covers updates to three major chemicals air rules for the Synthetic Organic Chemical Manufacturing Industry, Polyether Polyols Production, and Chemical Manufacturing Area Sources, but multiple other rules affecting industry are also covered, including an outlook for Toxics Substance Control Act updates in 2025.

U.S. EPA finalized revised standards for the Synthetic Organic Chemical Manufacturing Industry (SOCMI) on May 16, 2024. This action included changes to National Emissions Standards for Hazardous Air Pollutants (NESHAP) and Standards of Performance for New Stationary Sources (or “New Source Performance Standards,” NSPS) for several rules including 40 CFR Part 63, Subparts F, G, H, I (HON), 40 CFR Part 63, Subpart U (Polymers and Resins I, or P&R I), and 40 CFR Part 63, Subpart W (P&R II). U.S. EPA also finalized four new subparts under 40 CFR Part 60: VVb (SOCMI Equipment Leaks), IIIa (SOCMI Air Oxidation Unit Processes), NNNa (SOCMI Distillation Operations), and RRRa (SOCMI Reactor Processes).

Multiple industry representatives have filed both judicial petitions for review and petitions for agency reconsideration. Petitioners have been busy preparing court briefs and oral arguments; however, it is currently unknown how the change in U.S. EPA administration will impact the pending litigation and reconsideration. We expect 2025 will bring some clarity to the future of several provisions, including those related to controlling emissions of ethylene oxide (EtO) and dioxins and furans, as well as those related to fenceline monitoring. Stay tuned to our 4 The Record Articles for updates on these rules throughout 2025.

Polyether Polyols Production Industry

On December 27, 2024, U.S. EPA proposed changes to the NESHAP for Polyether Polyols Production, commonly referred to as the “PEPO NESHAP,” codified under 40 CFR Part 63, Subpart PPP. As with their HON review, U.S. EPA performed a second risk analysis under Clean Air Act (CAA) Section 112(f) and is proposing that risks from EtO emissions from PEPO sources are unacceptable. To address risk, U.S. EPA is proposing additional control requirements for EtO emissions from process vents, storage vessels, equipment leaks, heat exchange systems, and wastewater. U.S. EPA is also proposing rule updates as part of their CAA Section 112(d)(6) technology review for heat exchange systems, storage vessels, process vents, and equipment leaks. Additionally, U.S. EPA is proposing fenceline monitoring requirements under CAA Section 112(d)(6) along with several other important changes as part of a gap-filling exercise. A brief summary of the proposed changes is provided below.

Changes to Address Risk

According to U.S. EPA’s proposal, risk from the PEPO source category is driven by emissions from wastewater and equipment leaks and there are six facilities with a maximum individual lifetime cancer risk (MIR) greater than 100-in-1 million. The table below presents the standards U.S. EPA is proposing to reduce emissions of EtO from PEPO facilities.

For the Source Type Below:	That Contain the Following Amount of EtO:	Facilities Must Reduce EtO Emissions by:
Equipment Leaks	0.1% by weight	Monitoring connectors and gas/vapor light liquid valves on a monthly basis using a leak definition of 100 parts per million by volume (ppmv) with no skip period or delay of repair unless the equipment can be isolated such that it is no longer in EtO service; and Monitoring pumps on a monthly basis using a leak definition of 500 ppmv with no delay of repair unless the equipment can be isolated such that it is no longer in EtO service.
Heat Exchange Systems	0.1% by weight	Monitoring on a weekly basis for leaks using the Modified El Paso Method and repairing leaks above the leak action level (6.2 ppmv as methane in the stripping gas) within 15 days with no delay of repair allowed.
Process Vents	Vents that contain 1 ppmv or more of EtO (uncontrolled) and when combined emit 5 lb/yr or more of EtO (Uncontrolled)	Venting to a flare meeting the Refinery Sector Rule (40 CFR Part 63, Subpart CC) requirements; or By venting to a control device that reduces EtO by 99.9% by weight or to a concentration of less than 1 ppmv or to less than 5 lb/yr for all combined process vents. Additionally, facilities would not be able to use the extended cookout (ECO) pollution prevention technique or existing production-based limits in place of the proposed provisions above.
Storage Vessels	0.1% by weight
Wastewater	1 part per million by weight (ppmw, annual average)	Reducing the concentration of EtO in the wastewater to less than 1 ppmw. Additionally, U.S. EPA is proposing to add provisions prohibiting the injection of wastewater, or water that contains or has contacted EtO into a heat exchange system.
Pressure Release Devices (PRD)	0.1% by weight	Conducting instrument monitoring with a 500 ppmv leak definition; Implementing three prevention measures; Monitoring for releases and implementing corrective actions; and Any release event from a PRD in EtO service would be a deviation.
Pressure Vessels	0.1% by weight, any capacity	Monitoring initially and annually, > 500 ppm is a violation. Excludes equipment in EtO service (connectors, G/V/LL valves, LL pump), and G/V/LL valves/connectors covered by LDAR provisions. Operating as a closed system routed to control. PRD releases would be a deviation.
Flares used to comply with process vent and storage vessel EtO control requirements or where leaks from equipment in EtO service are routed to a flare		Meeting the Refinery Sector Rule (40 CFR Part 63, Subpart CC) flare requirements at 40 CFR §§63.670 and 63.671.

 

U.S. EPA estimates that the proposed requirements above will reduce the MIR of the PEPO source category to 100-in-1 million. Although U.S. EPA is proposing fenceline monitoring requirements for EtO, they are doing so under their CAA Section 112(d)(6) technology review, which is described below.

Changes to PEPO based on U.S. EPA’s Technology Review

U.S. EPA is proposing several changes to the requirements for heat exchange systems, storage vessels, process vents, and equipment leaks as part of a technology review. These changes are summarized in the next table.

Source Type	Proposed Rule Requirements
Heat Exchange Systems	Removal of the leak monitoring exemptions for once-through heat exchange systems meeting certain National Pollutant Discharge Elimination System (NPDES) permit conditions. Except for heat exchange systems with a maximum cooling water flow rate of 10 gallons per minute or less: Monitoring must be conducted using the Modified El Paso Method with a leak definition of 6.2 parts per million by volume (ppmv). Quarterly monitoring preceded by an initial 6-month period where monitoring is conducted monthly. Establishes a delay of repair action level of 62 ppmv. If this value is exceeded, delay of repair cannot be used beyond 30 days. If 99 wt.% or more of the organic compounds that could leak are water soluble and have a Henry’s Law Constant < 5.0E-6 atm-m3/mol at 25°C, the system can be monitored using water sampling methods instead of the Modified El Paso method.
Storage Vessels	Revision of the control applicability volume criteria from 75 cubic meters (m3) to 38 m3. Addition of upgraded deck fittings and controls for guidepoles for all storage vessels equipped with an internal floating roof (as required by 40 CFR Part 63, Subpart WW).
Process Vents	Removal of the total resource effectiveness (TRE) concept. Removal of the 50-ppmv and 0.005 standard cubic meter per minute (scmm) thresholds from the group 1 definition for continuous process vents associated with non-epoxide organic Hazardous Air Pollutants (HAP) and from the group 1 definition for process vents associated with a polyether polyol manufacturing unit (PMPU) using tetrahydrofuran (THF). Instead, facilities would be required to control process vents that emit 1.0 lb/hr or more of organic HAP. Removal of the group 1 process vent thresholds for mass flow rate, cutoff flow rate, and annual average batch vent flow rate from the definition of “group 1 combination of batch process vents” for batch process vents associated with the use of a non-epoxide organic HAP to make or modify the product at PEPO facilities. Instead, the combination of batch process vents that release a total of annual non-epoxide organic HAP emissions of 10,000 lb/yr or more would be considered “group 1 combination of batch process vents.”
Equipment Leaks	Lowering of the leak definition for valves in light liquid and gas/vapor service from 500 ppmv to 100 ppmv.

In addition to the above requirements, U.S. EPA is also proposing a fenceline monitoring program for PEPO facilities under the CAA Section 112(d)(6) technology review. Facilities that use, produce, store, or emit EtO would be required to conduct fenceline monitoring. Facilities would be required to place eight ambient air sampling canisters around their fencelines and potentially rotate the sampling locations for each sampling event based on the magnitude of the facility perimeter. Sampling events would be conducted every five days for a period of 24 hours. Facilities would be required to calculate the difference between the highest and lowest individual sample for each sampling event (known as “Δc”) and maintain their annual average Δc value below an action level of 0.2 micrograms of EtO per cubic meter (µg/m³). If the action level is exceeded, facilities would conduct a root cause analysis and implement corrective actions to reduce emissions if the source of the exceedance is under their control. The fenceline monitoring data would be electronically reported on a quarterly basis.

Changes to PEPO based on CAA Section 112(d)(2), (d)(3), and (h)

U.S. EPA is proposing several additional changes consistent with CAA Sections 112(d)(2), (d)(3), and (h) as summarized in the table below.

Source Type	Proposed Requirements
Non-Flare Control Devices	Conduct repeat performance tests within 60 months of previous tests.
Adsorbers	Adsorbers that cannot be regenerated or that are regenerated off-site would be required to use two or more beds in series and must monitor for HAP or Total organic compounds (TOC) at the outlet of the first bed.
Flares	Flares used to comply with the emissions standard would be subject to the requirements in 40 CFR Part 63, Subpart CC (Refinery MACT), with certain clarifications and exemptions.
Bypass Lines	Any bypass would be a violation. Estimate, maintain records, and report the quantity of organic HAP released by bypasses.
Maintenance Activities	Work practice standards for storage vessel degassing, storage vessel maintenance, and equipment opening would be added. Planned routine maintenance of storage vessel control devices would be limited to 240 hr/yr and vessels could not be filled during maintenance periods.
Pressure Vessels	Pressure vessels greater than 204.9 kilopascal (kPa) and without emissions to atmosphere would no longer be excluded from the definition of storage vessel. A definition for pressure vessels would be added. For Group 1 pressure vessels: monitoring initially, and annually, > 500 ppm is a violation. Excludes equipment in EtO service (connectors, G/V/LL valves, LL pump), and G/V/LL valves/connectors covered by LDAR provisions. Operate Group 1 vessels as a closed system routed to control. PRD releases would be a violation.
Surge Control Vessels and Bottoms Receivers	Emissions would be treated as process vents and subject to the applicable control requirements.
Transfer Operations	Transfer racks that load organic HAP materials with a maximum true vapor pressure of 0.5 psia or more must comply with the HON requirements for transfer racks.

 

U.S. EPA is proposing two additional changes as part of their CAA Sections 112(d)(2), (d)(3), and (h) review. First, the agency is proposing to add butylene oxide to the list of HAP presented in Table 4 to subpart PPP (Known Organic HAP from Polyether Polyol Production). Second, U.S. EPA is proposing to remove the exemption for reactions/processing that occur after completion of epoxide polymerization and all catalyst removal steps; instead, U.S. EPA is proposing to require control of emissions from these unregulated sources (including solvent removal, purification, drying, and solids handling).

Other Changes

U.S. EPA is proposing several other changes to Subpart PPP including a 5-year repeat performance testing requirement, electronic reporting requirements, and requirements for monitoring adsorbers that cannot be regenerated and regenerative adsorbers that are regenerated offsite. U.S. EPA is also proposing to remove the provision exempting sources from determining uncontrolled process vent emissions when complying with the percent reduction and production-based emissions limits.

Proposed Compliance Dates

Sources that were constructed or reconstructed on or before December 27, 2024 would be required to comply with the EtO control requirements two years from the effective date of the final rule and all other control requirements three years from the effective date of the final rule, with the exception of the fenceline monitoring requirements. Sources would be required to start collecting fenceline monitoring data within two years, and would be required to implement correction actions within three years. Sources that are constructed or reconstructed after December 27, 2024 would be required to comply with the new requirements upon the effective date of the final rule or upon startup, whichever is later.

Chemical Manufacturing Area Sources

On January 22, 2025, U.S. EPA published a proposed rule updating the NESHAP for Chemical Manufacturing Area Sources, otherwise known as the CMAS NESHAP. The proposed rule is a result of the U.S. EPA’s CAA Section 112(d)(6) technology review of the generally available control technology (GACT) standards previously promulgated in 2009. Furthermore, U.S. EPA is using their authority under CAA Section 112(c)(5) to establish an additional category/subcategory of sources in response to identifying a threat of adverse effects to human health or the environment. As a result of the 2016 update to the integrated risk information system (IRIS) value for EtO, the U.S. EPA is proposing to add “Chemical Manufacturing with Ethylene Oxide” to the source category list along with GACT standards per CAA Section 112(d)(5). The new are source category would include “processes that produce a material or family of materials described by NAICS code 325 where EtO is used as a feedstock, generated as a byproduct, or is the material produced.”

U.S. EPA is proposing EtO GACT standards for equipment leaks, heat exchange systems, process vents, storage tanks, wastewater, transfer operations, pressure vessels, and pressure relief devices (PRDs). These standards mirror what we have seen in other recent updates to chemical sector rules include the Miscellaneous Organic Chemical Manufacturing NESHAP (MON) and the HON. U.S. EPA is also proposing a fenceline monitoring program for EtO emissions.

U.S. EPA is proposing additional GACT standards for non-EtO emissions including a PRD work practice standard, requirements for bypasses, and revisions to requirements for pressure vessels. Revised requirements for equipment leaks, heat exchange systems, and process vents are also being proposed under U.S. EPA’s technology review. Below is a summary of the proposed rule.

Controls to Address Risk

U.S. EPA is proposing that sources will be newly subject to CMAS if they own or operate a CMPU located at an area source of hazardous air pollutants (HAP) and:

• EtO is used as a feedstock at an individual concentration greater than 0.1% by weight;
• EtO is produced as a product of the CMPU;
• EtO is produced as a byproduct and is present in any liquid stream (process or waste) at a concentration of 1 ppmw or more; or
• EtO is produced as a byproduct and is present in any continuous or batch process vent at a concentration of 1 ppmv or more.

The table below presents the standards U.S. EPA is proposing to reduce emissions of EtO from CMAS facilities.

For the Source Type Below:	That Contain the Following Amount of EtO:	Facilities Must Reduce EtO Emissions by:
Equipment Leaks	0.1% by weight	Monitoring connectors and gas/vapor light liquid valves on a monthly basis using a leak definition of 100 ppmv with no skip period or delay of repair unless the equipment can be isolated such that it is no longer in EtO service; and Monitoring pumps on a monthly basis using a leak definition of 500 ppmv with no delay of repair unless the equipment can be isolated such that it is no longer in EtO service.
Heat Exchange Systems	0.1% by weight	Monitoring for leaks using the Modified El Paso Method first monthly for six months and then quarterly, and repairing leaks above the leak action level (6.2 ppmv as methane in the stripping gas) within 15 days with no delay of repair allowed.
Process Vents	Vents that contain 1 ppmv or more of EtO (uncontrolled) and when combined emit 5 lb/yr or more of EtO (uncontrolled)	Venting to a flare meeting the Refinery Sector Rule (40 CFR Part 63, Subpart CC) requirements; or By venting to a control device that reduces EtO by 99.9% by weight or to a concentration of less than 1 ppmv or to less than 5 lb/yr for all combined process vents.
Storage Vessels	0.1% by weight
Wastewater	1 ppmw	Reducing the concentration of EtO in the wastewater to less than 1 ppmw in accordance with the Group 1 wastewater treatment requirements under the HON. Additionally, EPA is proposing to add provisions prohibiting the injection of wastewater, or water that contains or has contacted EtO into a heat exchange system.
Pressure Release Devices	0.1% by weight	Conducting instrument monitoring with a 500 ppm leak definition; Implementing three prevention measures; Monitoring for releases and implementing corrective actions; and Any release event from a PRD in EtO service would be a deviation.
Pressure Vessels	0.1% by weight, any capacity	Monitoring initially, and annually, > 500 ppm is a violation. Excludes equipment in EtO service (connectors, G/V/LL valves, LL pump), and G/V/LL valves/connectors covered by LDAR provisions. Operating as a closed system routed to control. PRD releases would be a deviation.
Transfer Operations	Any transfer operation at the CMPU	Using submerged loading or bottom loading; Routing emissions to a fuel gas system or process; Vapor balancing; or Venting to a control device
Flares used to comply with process vent and storage vessel EtO control requirements or where leaks from equipment in EtO service are routed to a flare		Meeting the Refinery Sector Rule (40 CFR Part 63, Subpart CC) flare requirements at 40 CFR §§63.670 and 63.671.

In addition to the above proposed requirements to address risk from EtO emissions, U.S. EPA is also proposing a fenceline monitoring program for CMAS facilities that use, produce, store, or emit EtO by referencing the fenceline monitoring provisions for EtO from HON. Facilities would be required to place eight ambient air sampling canisters around their fencelines and potentially rotate the sampling locations for each sampling event based on the magnitude of the facility perimeter. Sampling events would be conducted every five days for a period of 24 hours. Facilities would be required to calculate the difference between the highest and lowest individual sample for each sampling event (known as “Δc”) and maintain their annual average Δc value below an action level of 0.2 micrograms of EtO per cubic meter (µg/m³). If the action level is exceeded, facilities would conduct a root cause analysis and implement corrective actions to reduce emissions if the source of the exceedance is under their control. The fenceline monitoring data would be electronically reported on a quarterly basis.

New GACT Standards Under CAA Section 112(d)(5)

U.S. EPA is also proposing the following new GACT standards pursuant to CAA Section 112(d)(5):

Source Type	Proposed Rule Requirements
PRDs	For PRDs not routed to a control device, process, fuel gas system, or drain system, the following requirements would be added: Install monitoring system to alert when a PRD release occurs. Three redundant prevention measures must be implemented. Conduct a root cause analysis and initiate appropriate corrective action in response to any PRD release. Limit number of PRD releases to one or two releases in a three-year period depending on the cause of the release.
Bypass Lines	Any bypass would be a deviation. Sources must continue to monitor for bypasses according to Part 63, Subpart SS, except that analyzer vents and high point bleeds would no longer be exempt from the bypass provisions Open-ended valves or lines that use a cap, blind flange, plug, or second valve and that meet certain requirements would not be subject to bypass monitoring.
Pressure Vessels	Pressure vessels greater than 204.9 kPa and without emissions to atmosphere would no longer be excluded from the definition of storage vessel. A definition for pressure vessels would be added. For pressure vessels storing organic HAP with capacities of 20,000 gallons or more: monitoring initially and annually, > 500 ppm is a violation. Excludes equipment in EtO service (connectors, G/V/LL valves, LL pump), and G/V/LL valves/connectors covered by LDAR provisions. Operate as a closed system routed to control. PRD releases would be a deviation.

Proposed Revisions from U.S. EPA’s CAA Section 112(d)(6) Technology Review

U.S. EPA also conducted a CAA Section 112(d)(6) technology review for CMAS. As indicated in the table below, U.S. EPA has proposed technology review-based changes for equipment leaks, heat exchange systems, and process vents; however, no potential changes were proposed for storage tanks, wastewater, flares, or fenceline monitoring (other than those for source in EtO service as described above).

Source Type	Proposed Rule Requirements
Equipment Leaks	Annual LDAR for pumps in light liquid service, and valves and connectors in gas/vapor/light liquid service using Method 21 instrument monitoring (instead of audio, visual, or olfactory monitoring) 10,000 ppmv leak definition First attempt at repair in 5 days and repair required by 15 days (although delay of repair is allowed in certain circumstances). Sources would be required to comply with HON LDAR requirements for the following: Compressors; Sampling connection systems; Open-ended valves or lines; Equipment in heavy liquid service; and Agitators in gas/vapor/light liquid service.
Heat Exchange Systems	Removal of the leak monitoring exemptions for once-through heat exchange systems meeting certain National Pollutant Discharge Elimination System (NPDES) per conditions. For heat exchange systems with a maximum cooling water flow rate of 8,000 gallons per minute or less: Monitoring must be conducted using the Modified El Paso Method with a leak definition of 6.2 ppmv. Quarterly monitoring preceded by an initial 6-month period where monitoring is conducted monthly. Establishes a delay of repair action level of 62 ppmv. If this value is exceeded, delay of repair cannot be used beyond 30 days. If 99 wt.% or more of the organic compounds that could leak are water soluble and have a Henry’s Law Constant < 5.0E-6 atm-m3/mol at 25°C, the system can be monitored using methods from the previous rule [e.g., §63.104(b)].
Process Vents	Remove the 50 ppmv metal HAP threshold in the definition of a “Metal HAP process vent.”

Other Proposed Changes

U.S. EPA is proposing several other changes in addition to the new GACT standards under CAA Section 112(d)(5) and technology review-based standards under CAA Section 112(d)(6). These include electronic reporting, removal of the affirmative defense provisions, repeat performance testing, and edits to address incorrect section references and minor editorial revisions.

For electronic reporting, facilities would be required to submit compliance status reports, performance test reports, flare management plans, and periodic reports (including fenceline monitoring reports) through U.S. EPA’s Central Data Exchange using the Compliance and Emissions Data Reporting Interface (CEDRI). Facilities would be required to submit results of performance testing using the Electronic Reporting Tool (ERT) and semiannual compliance reports would be submitted using U.S. EPA-developed reporting templates.

U.S. EPA is also proposing to remove the existing affirmative defense provisions consistent with a 2014 D.C. Circuit court case that vacated affirmative defense provisions for Portland cement kilns. In proposing to remove the provisions at 40 CFR §63.11501(e), U.S. EPA states that it may use its case-by-case enforcement discretion to provide flexibility in enforcement decisions.

Facilities are currently allowed to use engineering assessments and design evaluations to demonstrate compliance with process vent and storage tank emissions limits; however, U.S. EPA is proposing to remove that flexibility and instead require sources to conduct performance tests at least once every five years to demonstrate compliance with emissions limits.

U.S. EPA is also proposing several editorial edits and clarifications. The agency provides a list of these edits in the preamble to the proposed rule. The following is a list of notable revisions U.S. EPA is proposing:

• Removal of the provision at 40 CFR §63.11498(b) that exempts facilities from complying with the wastewater control requirements in Table 6 of the rule during periods of startup and shutdown.
• Addition of 40 CFR Part 60, Subparts VVa, VVb, IIIa, NNNa, and RRRa to the overlap provisions in 40 CFR §63.11500(b).
• Removal of the provisions that allow facilities to skip semiannual reporting for periods where certain events do not occur [40 CFR §63.11501(d)].
• Revisions to the definitions of “batch process vent, continuous process vent,” and “in organic HAP service,” to clarify that the specified HAP concentration cut-offs do not apply when evaluating whether vents, wastewater, equipment, and heat exchange systems are “in EtO service.”

Proposed Compliance Dates

U.S. EPA is proposing that facilities that are constructed or reconstructed before the rule’s proposal date would be required to comply with the requirements for control of EtO within two years of the final rule. Facilities would have three years to comply with all non-EtO related requirements. Facilities would be required to start collecting EtO fenceline monitoring data two years after the effective date of the final rule and begin conducting root cause analysis and performing corrective actions three years after the effective date. Sources that commenced construction or reconstruction after the proposal date would be required to comply with all provisions upon the effective date of the final rule, or upon startup, whichever is later.

Additional Chemicals and EtO Related Air Rules

U.S. EPA’s regulatory agenda indicates the agency will be addressing two additional air rules and one method related to chemicals and/or EtO.

U.S. EPA is expected to issue a proposed risk and technology review for Hospital Ethylene Oxide Sterilizers in the fall of this year and it will likely contain revised provisions in light of the revised EtO IRIS value, but the extent of those revisions will likely be foreshadowed by the new administration’s actions related to the SCOMI, PEPO, and CMAS rules.

U.S. EPA’s regulatory agenda also indicates that the agency plans to issue a final reconsideration rule for the Polyvinyl Chloride and Copolymers (PVC) NESHAP sometime this fall. U.S. EPA issued a proposed reconsideration rule in November of 2020, but since then, the agency has not taken the rule back up again. At issue are process vent and wastewater emissions limits, as well as requirements for storage vessels and PRD monitoring.

On a more straightforward note, U.S. EPA’s regulatory agenda indicates that the agency plans to revise U.S. EPA Method 325A/B (used for fenceline monitoring) to incorporate new uptake rates and sorbents consistent with the additional chemicals to which the method is applied under the fenceline monitoring program in the HON (i.e., chloroprene, 1,3-butadiene, and ethylene dichloride). The agenda indicates U.S. EPA plans to issue a proposal in February and a final rule in June.

Toxic Substances Control Act

Barring any major changes from the new administration, 2025 is also likely to be a significant year for activity related to the Toxic Substances Control Act (TSCA). On December 18, 2024, U.S. EPA began the risk evaluation step for five chemicals: vinyl chloride, acetaldehyde, acrylonitrile, benzenamine, and 4,4’-methylenebis(2-chloroaniline) (MBOCA). U.S. EPA also announced the prioritization process for the next five chemicals: benzene, ethylbenzene, naphthalene, styrene, and 4-tert-octylphenol. When a risk evaluation results in a finding of unreasonable risk, U.S. EPA then begins a risk management process that involves developing a rule to protect workers, consumers, and/or the environment from the identified risks. For example, in December 2024, U.S. EPA issued a final rule to ban all uses of trichloroethylene, ban all consumer uses and many commercial uses of perchloroethylene, and require worker protections for all remaining uses of perchloroethylene. They also finalized their technology review of the Perchloroethylene Dry Cleaning NESHAP with no changes in acknowledgement of the impending ban.

Since December, U.S. EPA has finalized TSCA risk evaluations from formaldehyde, diisodecyl phthalate (DIDP), and diisononyl phthalate (DINP). The agency found unreasonable risk for all three chemicals. U.S. EPA also recently released a draft scoping document for vinyl chloride.

Later this year, we expect to see proposed regulations for 1,4-dioxane formaldehyde following U.S. EPA’s late 2024 findings of unreasonable risk. We also expect to see proposed regulations for DIDP, DINP and final regulations for 1-bromopropane, and n-methylpyrrolidone (NMP) late this year.

For additional information, visit U.S. EPA’s Risk Management for Existing Chemicals under TSCA | US EPA and stay current with our “4 The Record” series for updates from our TSCA experts.

Moving Forward

ALL4 has already begun evaluating the impacts of the above-mentioned proposed rule changes for our clients that operate CMAS and PEPO sources. Additionally, ALL4 is assisting clients with their review and implementation of the SOCMI rule changes. We will be updating our clients and readers of our “4 The Record” series as these rules evolve. Updates will also be posted to our chemical industry resources page. If you have questions about any of the topics covered above or how ALL4 might be able to help your facility plan for and comply with evolving regulations, contact your ALL4 project manager or Philip Crawford at pcrawford@all4inc.com.