A substance or material that is capable of posing an unreasonable risk to health, safety, and property when transported in commerce is

The U.S. Department of Transportation (DOT) and its Pipeline and Hazardous Materials Safety Administration (PHMSA) define a hazardous material (HAZMAT) almost identically to the question's phrasing. According to federal regulation 49 CFR § 171.8, a hazardous material is a substance or material determined by the Secretary of Transportation to be "capable of posing an unreasonable risk to health, safety, and property when transported in commerce." This term is the specific legal and regulatory standard used within the United States for classifying such materials for transport.

A. HAZCOM (Hazard Communication) is an OSHA standard for communicating chemical hazards to workers in a workplace, not the material itself.

B. "Dangerous goods" is the term used in international transportation regulations (e.g., IATA, IMO), while HAZMAT is the specific term used in U.S. domestic regulations.

D. PHMSA is the Pipeline and Hazardous Materials Safety Administration, the U.S. government agency that regulates HAZMAT, not the substance.

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1. U.S. Department of Transportation. (2023). Code of Federal Regulations, Title 49, Section 171.8 - Definitions and abbreviations. U.S. Government Publishing Office. This section explicitly defines "Hazardous material" as "a substance or material that the Secretary of Transportation has determined is capable of posing an unreasonable risk to health, safety, and property when transported in commerce..."

2. Pipeline and Hazardous Materials Safety Administration (PHMSA). (n.d.). Hazardous Materials Regulations (HMR). U.S. Department of Transportation. The official documentation states that the HMR (49 CFR Parts 171-180) governs the transportation of hazardous materials, using the definition found in § 171.8.

3. University of Washington, Supply Chain Transportation & Logistics. (2018). Basics of Transporting Hazardous Materials. This courseware outlines the key differences in terminology, noting that "In the U.S., these materials are called hazardous materials or HAZMAT. Internationally, they are called dangerous goods." It confirms HAZMAT is the correct U.S. domestic term.