What is a toxic substance?

A toxic substance is a substance that can be poisonous or cause health effects. People are generally concerned about chemicals like polychlorinated biphenyls (PCBs) and dioxin which can be found at some hazardous waste sites.

I don't know if this is a multiple choice question but I'm going to answer anyway. A toxic substance could be defined as lots of things; for example poison most people when thinking of something toxic and deadly poison comes to mind. Toxic substances are really anything that can kill or seriously harm you when coming into contact with.