Which agency is primarily responsible for enforcing hazardous material regulations?

The Department of Transportation (DOT) is the agency primarily responsible for enforcing hazardous material regulations. This responsibility primarily falls under the Pipeline and Hazardous Materials Safety Administration (PHMSA), which is a part of DOT. The DOT establishes regulations that govern the transportation of hazardous materials by road, rail, air, and waterways to ensure safety and minimize risks associated with transporting dangerous goods.

The DOT's regulations are crucial for maintaining the safety of transportation systems, protecting the health of workers and the public, and safeguarding the environment from hazardous materials. The agency issues guidelines pertaining to the classification, packaging, labeling, and transportation of hazardous materials, and conducts inspections and assessments to ensure compliance with these regulations.

While the Environmental Protection Agency, Occupational Safety and Health Administration, and Department of Homeland Security all play significant roles in various aspects of hazardous materials in their own right, their primary focus is not on the specific regulations surrounding transportation. The EPA deals more with environmental protection and pollution control, OSHA is focused on worker safety and health in workplaces, and DHS addresses national security and emergency management, which may encompass hazardous materials in certain contexts but does not specifically oversee transportation regulations. Therefore, DOT is the correct answer in this context.