Hazardous materials are defined by the U.S. Department of Transportation in accordance with the Federal Hazardous Material Law. A substance or material may be designated as hazardous if the transportation of the material in a particular amount and form poses an unreasonable risk to health and safety or property. Hazardous material may include: an explosive, radioactive material, etiologic agent, flammable or combustible liquid or solid, poison, oxidizing or corrosive material, and compressed gas. For more general information, go to the U.S. DOT website at http://www.phmsa.dot.gov/hazmat