What type of incident is characterized by hazardous materials being released into the environment?

The correct choice describes an "Actual release" as an incident where hazardous materials have been unintentionally released into the environment. This situation demands immediate attention and action because it poses risks to public safety and the environment. An actual release indicates that the hazardous material has escaped from its intended containment—such as storage tanks, pipelines, or containers—resulting in exposure or potential harm.

In contrast, a potential release refers to a situation where there might be a risk of such a release occurring but has not yet transpired. A threat involves the possibility of a release occurring due to external or internal factors, yet it does not confirm that any hazardous materials have actually entered the environment. Emergency response refers to the actions taken to mitigate or manage the consequences of an actual release but does not describe the incident type itself. Recognizing the difference is crucial for proper response protocols and public safety measures.