What term is used to identify lines that contain materials considered extremely hazardous to life or health?

The term "toxic" specifically refers to materials that are harmful or lethal to human health and can cause serious biological effects if they are ingested, inhaled, or come into contact with the skin. In the context of hazardous materials, toxic substances pose a significant risk, as exposure to them can lead to acute or chronic health problems. This encompasses a wide range of materials that can be present in various forms, such as gases, liquids, or solids.

The other terms, while they do indicate certain properties of materials, do not cover the full spectrum of health hazards to the same extent as toxic materials. For instance, corrosive materials can damage living tissue or materials but are not necessarily toxic. Explosive materials refer to substances that can cause explosions, and hazardous materials is a broader category that includes many types of risks. The specificity of "toxic" highlights its critical relevance to health and safety concerns in environments where hazardous materials are handled.