40 CFR 302.4: Hazardous Substances, Mixture RQs, and Reporting

40 CFR 302.4 is the federal regulation that catalogs every hazardous substance covered by CERCLA’s release-reporting rules and assigns each one a reportable quantity (RQ). If your facility or vessel releases a listed substance into the environment in an amount that meets or exceeds its RQ within any 24-hour period, the person in charge must immediately call the National Response Center. Missing that call exposes you to criminal fines, up to three years in prison for a first offense, and civil penalties above $71,000 per violation.

What the Regulation Lists

The regulation does not build its chemical list from scratch. It consolidates substances designated under five federal environmental statutes into a single alphabetical table (Table 302.4):¹

Clean Water Act Section 311(b)(2)(A) hazardous substances
Clean Water Act Section 307(a) toxic pollutants
Clean Air Act Section 112 hazardous air pollutants
RCRA Section 3001 hazardous wastes
TSCA Section 7 substances subject to emergency EPA action²

Each entry in Table 302.4 shows the chemical name, the Chemical Abstracts Service Registry Number (CASRN), any applicable RCRA waste code, and the RQ in both pounds and kilograms. The CASRN is the most reliable identifier because many of these chemicals travel under several trade names. Pull the CASRN off your safety data sheet and check it against the table.

Reportable Quantities and the One-Pound Default

RQs range from one pound for the most dangerous substances to 5,000 pounds for others, and the threshold applies to the total quantity released within any 24-hour period. Multiple small releases of the same substance during a single day add together.³

Watch for the default. If a substance is listed but has not been assigned a specific adjusted quantity, the statutory RQ under CERCLA Section 102 is one pound.¹ One pound is very little material, and it catches operators off guard more than any other feature of the regulation.

Calculating the RQ for Mixtures

Pure substances are simple: compare pounds released against pounds in the table. Mixtures and solutions follow a two-part rule in 40 CFR 302.6(b).³

If you know the concentration of every hazardous component in the mixture, you only report when the actual weight of a single hazardous constituent released meets or exceeds that constituent’s RQ. A large spill of a diluted acid solution only triggers notification if the weight of the pure acid inside it hits the acid’s RQ.⁴

If any one component’s concentration is unknown, the rule flips. You must treat the total weight of the entire mixture as if it were the most dangerous constituent present, and compare that total against the lowest RQ of any hazardous substance in the mixture.⁵ Facilities without accurate safety data sheets and inventory records end up reporting far more often than necessary, because the unknown-concentration rule almost always produces a lower trigger.

What Counts as a Release

CERCLA defines “release” to cover almost any way a substance can enter the environment: spilling, leaking, pumping, pouring, emitting, discharging, injecting, escaping, leaching, dumping, and disposing. Abandoning or discarding containers holding hazardous substances is also a release.⁶

Several situations are carved out and do not require notification:

A release that only exposes workers at the facility, with respect to claims those workers may bring against their employer
Engine exhaust from motor vehicles, aircraft, vessels, rolling stock, and pipeline pumping station engines
Certain nuclear incidents covered by NRC financial protection requirements
Normal application of fertilizer⁶
Federally permitted releases and the application of a pesticide³

A federally permitted release generally means one occurring under a valid permit or control regulation issued under the Clean Water Act, Clean Air Act, or another specified statute. If your facility operates under such a permit and the discharge stays within its terms, that particular release does not trigger a call to the NRC.

Calling the National Response Center

Once the person in charge has knowledge that a release has met or exceeded an RQ, the statute requires immediate notification.⁷ Take the basic steps needed to protect life and safety, then make the call. Any delay beyond that invites enforcement scrutiny.

The NRC operates around the clock at 1-800-424-8802.³ A duty officer records the incident and forwards the notification to appropriate federal agencies and to the governor of any affected state.⁷ Post the number where supervisors can find it without hunting.

Have this information ready, but do not let gathering it slow the call:⁸

Chemical identity and whether it is an extremely hazardous substance under EPCRA
Estimated quantity released
Time the release started and how long it lasted or whether it is ongoing
Medium affected (air, water, land, or a combination)
Known or anticipated acute or chronic health effects, and medical advice for anyone exposed
Recommended protective actions such as evacuation or sheltering in place
Name and phone number of a contact person for follow-up

A partial report made quickly is better, legally and practically, than a complete report made late. Update the details afterward.

State and Local Notification Under EPCRA

Calling the NRC does not end your obligations. EPCRA Section 304 requires a separate immediate notification to the State or Tribal Emergency Response Commission (SERC or TERC) and to the Local or Tribal Emergency Planning Committee (LEPC or TEPC) for any area likely to be affected.⁸ Meeting the federal reporting duty does not satisfy the state and local ones.

A written follow-up report to the SERC and LEPC is required as soon as practicable. It updates the initial information and describes the response actions taken and any medical attention necessary for exposed individuals.⁸ Some states impose shorter deadlines for the written follow-up, so check with your state emergency response commission.

Continuous Release Reporting

Some facilities have routine, low-level emissions built into normal operations. For those, 40 CFR 302.8 provides a reduced reporting pathway that replaces repeat emergency calls with a structured sequence.⁹

To qualify, the release must be both continuous and stable. Continuous means uninterrupted or a routine, anticipated, intermittent part of normal operations. Stable means predictable and regular in amount and rate. Unpredictable releases do not qualify.⁹

Once qualified, the facility follows this sequence:

An initial telephone notification to the NRC identifying the report as an initial continuous release notification, with facility name, location, and each hazardous substance being released
An initial written notification to the appropriate EPA regional office within 30 days of the phone call
An annual follow-up within 30 days of the first anniversary of the initial written notification, verifying and updating the earlier information
Change notifications for any shift in composition, source, or other reported details
Immediate notification whenever the quantity released in any 24-hour period exceeds the upper bound of the reported normal range⁹

The normal range is calculated from all releases of the substance occurring over any 24-hour period under normal operating conditions during the prior year, counting only releases that were both continuous and stable. A spike outside that range triggers an immediate notification just as a fresh spill would, so setting the range accurately matters.

Penalties for Failing to Report

The consequences split into criminal and civil tracks. On the criminal side, a person in charge who fails to notify the NRC immediately after learning of a reportable release, or who submits false or misleading information, faces fines under Title 18 and imprisonment of up to three years. A second or subsequent conviction raises the maximum to five years.⁷

On the civil side, EPA can pursue administrative penalties under both CERCLA Section 109 and EPCRA Section 325. Under the inflation adjustment effective January 2025, Class I administrative penalties reach up to $71,545 per violation, and Class II penalties for continuing violations climb to $71,545 per day, rising to $214,637 per day for subsequent violations.¹⁰ These figures adjust upward each year. For an unreported release stretching across several days, the daily-penalty math becomes serious quickly.

Because CERCLA and EPCRA impose separate reporting duties, a single release can generate simultaneous enforcement actions under both statutes. Failing to call the SERC and LEPC carries its own EPCRA fines on top of any CERCLA exposure for missing the NRC.

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eCFR. 40 CFR 302.4 – Hazardous Substances and Reportable Quantities
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Environmental Protection Agency. Hazardous Substance Designations and Release Notifications
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eCFR. 40 CFR 302.6 – Notification Requirements
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US EPA. Reporting Hazardous Substance Mixtures
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US EPA. Release Reporting Requirements for Hazardous Substances in Mixtures
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Office of the Law Revision Counsel. 42 USC 9601 – Definitions
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Office of the Law Revision Counsel. 42 USC 9603 – Notification Requirements
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US EPA. EPCRA Emergency Release Notifications
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eCFR. 40 CFR 302.8 – Continuous Releases
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Federal Register. Civil Monetary Penalty Inflation Adjustment