EPA updates how states should address plant startup pollution

The Environmental Protection Agency has issued new guidance on how it intends to review state air-quality plans covering excess emissions from industrial facilities during startup, shutdown and malfunction periods. The memorandum may shape future state submissions and EPA decisions, but it does not itself rewrite facility permits, state laws or every federally enforceable pollution limit.

EPA dated the memorandum September 1, 2026, and posted it September 2. It supersedes agency guidance issued December 19, 2024. The agency says the update responds to two decisions from the U.S. Court of Appeals for the District of Columbia Circuit involving the Clean Air Act and abnormal operating conditions.

What changed

The memorandum concerns State Implementation Plans, or SIPs. States, the District of Columbia, territories, local air authorities and eligible Tribes use these plans to implement, maintain and enforce federal air-quality standards. Once EPA approves a state requirement into a SIP, that requirement becomes federally enforceable.

SIPs can cover stationary sources such as power plants, refineries, chemical facilities and other industrial operations. Startup, shutdown and malfunction periods can involve different operating conditions and potentially elevated emissions, which makes the legal design of the applicable controls important for regulators, facilities and nearby communities.

EPA’s central question is whether a particular SIP provision is legally required, or is necessary or appropriate, to function as a continuous emission limitation. If so, the provision must operate continuously under the Clean Air Act and cannot simply exempt emissions during startup, shutdown or malfunction periods. The agency also recognizes that a SIP may contain other control measures, means or techniques that are not necessarily subject to the same continuous-emission-limitation analysis.

Continuous does not necessarily mean that one identical numerical limit must apply in every operating mode. EPA says a continuous limitation may include different numerical limits, technology requirements or work practices for startup and shutdown, provided the overall provision meets applicable Clean Air Act requirements and remains legally and practically enforceable.

How the court decisions shaped the policy

EPA says its approach reflects Environmental Committee of the Florida Electric Power Coordinating Group, Inc. v. EPA, decided in 2024, and SSM Litigation Group v. EPA, decided in 2025.

In Florida Electric, the D.C. Circuit partially vacated EPA’s earlier SIP call involving automatic exemptions, director’s-discretion provisions and some affirmative defenses. The court said EPA had not first made the required determination that the specific provisions had to qualify as continuous emission limitations. The court did not decide that every such provision must be allowed or approved; it left room for EPA to make a provision-specific determination based on the Clean Air Act and subject to judicial review.

The decision also left open scrutiny of director’s-discretion provisions that are so broad or unbounded that they could interfere with the agency’s ability to assess compliance with the Clean Air Act. EPA’s new memorandum says automatic exemptions and unbounded discretion provisions may therefore still raise legal concerns, depending on their design and operation.

The 2025 SSM Litigation Group decision addressed affirmative defenses. It distinguished a complete affirmative defense to liability from a provision that merely limits particular remedies after a violation has occurred. The court held that a complete affirmative defense may be permissible because it does not change the underlying emission limitation or make that limitation noncontinuous. A defense that restricts only the relief available to a court remains legally distinct and can raise separate enforcement concerns.

How EPA says it will review future plans

Under the memorandum, states are expected to explain in future SIP submissions whether proposed provisions are intended to be continuous emission limitations or other control measures. EPA says it will generally presume that a provision should be treated as a continuous emission limitation when it is required to be one under another Clean Air Act provision, or when the state is using it explicitly to achieve or maintain a national ambient air-quality standard or meet a comparable statutory requirement.

EPA gives attainment modeling as an example. If a state relies on a provision as continuously effective when demonstrating that an area will meet an air-quality standard, the agency says the provision’s actual operation should match that assumption. A state may provide additional analysis arguing that a different treatment is appropriate, and EPA says it will consider that explanation during the review.

The memorandum describes an intended review approach, not an automatic approval or rejection of any particular state rule. EPA says the facts and circumstances of each submission will matter.

What the memorandum does not do

The memorandum is nonbinding guidance. It is not a final agency action, final rule or facility-specific permit decision. It does not give industrial facilities a blanket exemption from emissions limits, and it does not automatically suspend or change current state or federally enforceable requirements.

Future EPA actions on SIP submissions must go through notice-and-comment procedures. Proposed actions can receive public comments, and resulting final agency actions can be challenged in court. That means the practical effect of the memorandum will develop through later state submissions, EPA approvals or disapprovals and litigation.

Who is affected

State and local air agencies will need to decide how to describe and support provisions addressing abnormal operating periods. Industrial sources may seek rules that account for unavoidable operating events, while environmental groups and communities near facilities may examine whether proposed controls remain enforceable and protective of air quality.

For residents near industrial plants, the immediate issue is not a nationwide change in pollution limits. The important records to watch are future SIP proposals, EPA notices, technical support documents and public-comment opportunities. Those materials should show whether a proposed provision is being treated as a continuous emission limitation, another control measure or an affirmative defense.

The policy’s most consequential effects will depend on how EPA applies it to individual submissions. The continuing legal question is whether a particular requirement must operate continuously under the Clean Air Act and what flexibility, if any, can be allowed without undermining enforceable air-quality protections.

Sources

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