Hazardous substances are materials that can pose a risk to health, safety, or the environment. These substances can be chemical, biological, or physical agents that may cause harm through exposure, ingestion, or inhalation. Common examples include toxic chemicals, flammable materials, and infectious agents. Regulations often classify hazardous substances based on their properties and potential risks. Proper handling, storage, and disposal are essential to minimize their impact. Organizations must follow guidelines set by agencies like the Environmental Protection Agency (EPA) to ensure safety and compliance when dealing with these materials.