A recent federal appeals court decision vacating EPA’s 2024 methylene chloride risk management rule has significant implications for how chemical risks may be evaluated and regulated under the Toxic Substances Control Act (TSCA). But for manufacturers, employers and product stewards, the broader takeaway extends beyond methylene chloride or even TSCA itself.

The decision reinforces an important principle in chemical risk assessment: identifying a chemical hazard is only one part of determining risk. How a chemical is used, who is exposed, the magnitude and duration of exposure, the effectiveness of controls, and the availability and risks of alternatives can materially change the risk profile from one application to another.

That distinction matters for companies making decisions about worker protection, product formulations, chemical substitution, regulatory compliance and product stewardship.

What Did the Fifth Circuit Decide?

On September 15, 2026, the U.S. Court of Appeals for the Fifth Circuit issued its published decision in East Fork Enterprises v. EPA, vacating EPA’s 2024 methylene chloride rule and the revised unreasonable-risk determination underlying it, and remanding the matter to EPA. The rule had prohibited 40 of 53 evaluated conditions of use and imposed a Workplace Chemical Protection Program on 13 continuing industrial and commercial uses.

Among the issues addressed, the court rejected EPA’s approach of determining unreasonable risk for methylene chloride as a “whole chemical” rather than making separate determinations for individual conditions of use. The court also found problems with EPA’s treatment of personal protective equipment and with aspects of the exposure limits used to support the rule.

Importantly, the decision should not be interpreted as a finding that methylene chloride presents no health hazard. Methylene chloride remains associated with serious acute and chronic health effects, and OSHA continues to regulate occupational exposure under its methylene chloride standard. OSHA’s existing standard includes an 8-hour permissible exposure limit of 25 ppm, a 15-minute short-term exposure limit of 125 ppm, exposure monitoring requirements, engineering and work-practice controls, respiratory protection, regulated areas, training and recordkeeping.

The more consequential issue for risk professionals may be how regulators, employers and manufacturers determine when a known hazard becomes an unreasonable or unacceptable risk under a particular set of circumstances.

The Same Chemical Can Present Different Risks Under Different Conditions

Methylene chloride provides a useful example because its applications vary substantially.

OSHA identifies uses including paint and coating removal, degreasing, polyurethane foam manufacturing, plastics processing, pharmaceutical extraction and other solvent applications. EPA’s rule also addressed highly specialized uses in chemical manufacturing, laboratory settings, plastic and rubber manufacturing, solvent welding, aerospace applications and production processes related to batteries and refrigerants.

Those uses do not necessarily create identical exposure scenarios.

A worker manually applying a solvent in an open or poorly ventilated workspace may experience a very different exposure than an employee working with the same substance in a closed industrial process. Likewise, a laboratory use involving small quantities and local exhaust ventilation may differ considerably from high-volume production, maintenance, or cleaning operations.

Understanding risk therefore requires asking more specific questions:

• What is the actual condition of use?
• How much of the chemical is present?
• How frequently and for how long is it used?
• Is the process open or enclosed?
• What inhalation or dermal exposure can reasonably occur?
• What engineering controls, work practices and PPE are in place?
• Are those controls effective under actual operating conditions?
• Are workers, consumers or surrounding populations potentially exposed?
• If substitution is being considered, what risks accompany the alternative?

These are exposure and risk characterization questions, not simply chemical classification questions.

Why Exposure Data Matters

For employers, the court decision does not eliminate the need to understand workplace exposures.

OSHA requires employers covered by its methylene chloride standard to determine employee exposure, typically through personal breathing-zone monitoring or representative sampling. The standard also requires controls when applicable exposure limits are exceeded or reasonably expected to be exceeded.

That same general principle applies well beyond methylene chloride.

Whether an organization is evaluating solvents, metals, powders, vapors, sensitizers or other workplace chemicals, reliable exposure data can help distinguish a theoretical hazard from the risk presented by an actual process.

RHP Risk Management’s Industrial Hygiene services help employers characterize workplace exposures through personal and area air monitoring, process evaluations, ventilation assessments, review of work practices and evaluation of engineering controls and personal protective equipment. RHP’s Certified Industrial Hygienists can then interpret those findings against applicable regulatory limits and occupational exposure guidelines.

The Issue Extends Beyond Workplace Compliance

The same use-specific approach is important not only in product stewardship and consumer product risk assessment, but also when evaluating environmental exposures and regulatory decisions tied to emissions and other release pathways.

A raw material may have a recognized hazard classification, but understanding risk requires evaluating the relevant condition of use and exposure pathway. For a finished product, that may mean considering concentration, formulation, route and frequency of consumer exposure. For an industrial source, it may also mean considering how a chemical is released, the populations potentially exposed, the magnitude and duration of environmental exposure, and the controls that influence those exposures.

For manufacturers, this can become especially important when regulators restrict a chemical, customers request reformulation, or companies consider substitutes.

Simply replacing one substance with another does not necessarily reduce overall risk. An alternative may introduce a different toxicological endpoint, require larger quantities, change volatility or particle characteristics, create new worker exposures during manufacturing, or alter consumer exposure during product use.

RHP’s Product Stewardship services integrate toxicology, exposure science, and regulatory expertise to evaluate chemical risks across a product’s lifecycle. This includes product safety evaluations, exposure modeling, safer-alternative assessments, laboratory simulation studies, and development of data to support regulatory and formulation decisions.

RHP’s Human Health Risk Sciences team combines toxicology, epidemiology, dose-response analysis and exposure science to evaluate whether available hazard information translates into meaningful risk under specific occupational, consumer or environmental exposure conditions. This same framework can support questions involving product safety, community or ambient exposures, and regulatory air-emission issues when the scientific question depends on how risk changes across different exposure scenarios.

The court’s emphasis on conditions of use may therefore have relevance beyond workplace exposure programs. Organizations involved in environmental permitting, air emissions, product stewardship or consumer risk assessment may want to consider whether the scientific and regulatory record adequately distinguishes among exposure pathways, populations and use scenarios rather than treating all uses as presenting the same risk profile.

EPA and OSHA May Ask Different Questions About the Same Chemical

The methylene chloride decision also brings renewed attention to the relationship between EPA chemical risk management and OSHA workplace regulation.

RHP recently discussed this issue in EPA, OSHA, and OMB Urged to Establish Federal Framework for Worker Chemical Safety. EPA and OSHA may evaluate overlapping occupational chemical exposures under different statutory authorities, methodologies, and regulatory objectives.

For employers, that means compliance cannot always be reduced to identifying a single exposure limit.

A company may need to understand OSHA requirements, EPA chemical restrictions, state requirements, product-specific obligations, and evolving toxicological information at the same time. Differences among those frameworks can also make well-documented exposure assessment and risk characterization particularly valuable.

A Broader Lesson for Chemical Risk Management

The Fifth Circuit’s decision will have direct consequences for EPA’s next steps on methylene chloride, but its practical relevance extends further.

For companies evaluating chemicals in the workplace or marketplace, sound decisions require connecting hazard information to actual conditions of use.

In practice, this means building a risk assessment around the actual condition of use: who may be exposed, by which route, at what magnitude and duration, how effective existing controls are, what uncertainty remains in the available data, and whether proposed alternatives introduce different risks. The appropriate questions may differ for workers, consumers and surrounding communities, but the underlying need for exposure-specific evidence is the same.

RHP Risk Management brings together Industrial Hygiene, Human Health Risk Sciences, Product Stewardship and Exposure Sciences to help clients evaluate chemical risk across occupational, consumer and environmental settings using defensible exposure data and risk assessment methods.

Our teams support occupational exposure assessments, chemical risk characterization, toxicological reviews, product and consumer exposure studies, safer-alternative evaluations, regulatory compliance, exposure modeling, and development of practical risk-management strategies.

Contact RHP Risk Management at (866) 481-8188 to set up an initial consultation and learn more about our Industrial Hygiene, Human Health Risk Sciences and Product Stewardship services.