Uncontrolled release of a chemical from its containment that either threatens to, or does, cause exposure to a chemical hazard. Such an incident may occur accidentally or deliberately.

Elements, compounds, mixtures, or solutions that are considered severely harmful to human health and the environment. They include substances that are toxic, corrosive, flammable, or explosive.

Uncontrolled release of radioactive material from its containment. This either threatens to, or does, cause exposure to a radioactive hazard. Such an incident may occur accidentally or deliberately.

The exposure to potentially harmful chemical, physical, or biological agents that occurs as a result of one's occupation.