HAZMAT

HAZMAT—short for hazardous materials—refers to any substance or material capable of causing harm to people, property, or the environment when released, spilled, or improperly managed. These materials may be flammable, explosive, toxic, radioactive, corrosive, reactive, infectious, or otherwise dangerous because of their chemical, physical, or biological properties. In the U.S., the term is most closely tied to the Department of Transportation’s (DOT) classification system under 49 CFR, which governs the transportation of hazardous materials, but it’s also widely used in the Occupational Safety and Health Administration (OSHA), Environmental Protection Agency (EPA), and emergency response settings to identify substances that require special handling, packaging, training, and preparedness.

DOT Definition of Hazardous Materials (HAZMAT)

Under DOT, a hazardous material or (HAZMAT)—as defined in 49 CFR §171.8—is any substance or material that the Secretary of Transportation determines is capable of posing an unreasonable risk to health, safety, or property when transported in commerce. This definition specifically applies to materials being shipped, offered for transport, or moved across public roads, railways, airways, or waterways.

DOT further clarifies that HAZMAT includes:

Any substance listed in the Hazardous Materials Table (49 CFR §172.101)
Materials that meet the criteria for any of the DOT hazard classes (Classes 1–9)
Hazardous substances, based on EPA reportable-quantity thresholds
Hazardous wastes, regulated under EPA’s Resource Conservation and Recovery Act (RCRA) but incorporated into DOT shipping rules
Marine pollutants
Elevated-temperature materials
Materials requiring special permits or handling

In short, if a material can endanger people, property, or the environment during transportation—and meets DOT’s classification criteria—it is regulated as a HAZMAT under 49 CFR. This definition forms the legal basis for packaging, marking, labeling, shipping papers, placarding, training, and emergency response requirements across the transportation industry.

The EPA Does Not Use “Hazardous Material” as an Official Regulatory Term

EPA does not define “hazardous material” or HAZMAT as a single regulatory category. Instead, the agency regulates materials that pose risk to human health or the environment under specific programs—primarily hazardous waste (RCRA), hazardous substances Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), and extremely hazardous substances Emergency Planning and Community Right-to-Know Act (EPCRA). Any material that meets these criteria is considered hazardous when released, managed, stored, or disposed under EPA authority.

OSHA Definition of Hazardous Materials

OSHA defines hazardous materials or HAZMAT through the framework of its Hazard Communication Standard (29 CFR 1910.1200), which classifies any chemical that poses a physical or health hazard as a hazardous chemical. This includes flammable, explosive, reactive, corrosive, toxic, carcinogenic, and environmentally harmful substances, as well as simple asphyxiants and combustible dusts. While OSHA uses the term “hazardous materials” in several standards—such as Hazardous Waste Operations and Emergency Response (HAZWOPER)—the agency’s official regulatory definition is grounded in the classification of hazardous chemicals that can harm workers in the workplace.

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