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What are extremely hazardous substances (EHSs)?

Emergency Planning and Community Right-to-Know Act (EPCRA) section 304 release reporting requirements apply to CERCLA hazardous substances and EPCRA extremely hazardous substances (EHSs). What are EHSs?

The EHS list was first compiled by EPA, and subsequently incorporated into EPCRA, to identify chemicals that could cause serious irreversible health effects from accidental releases. EHSs are listed in 40 CFR Part 355.