Final answer:
An individual tasked with notifying authorities about a contaminant release is known as a first responder or emergency responder, responsible for initiating actions to control the release.
Step-by-step explanation:
An individual who is likely to witness or discover a hazardous substance release and who will notify the proper authorities of the release is called a first responder or emergency responder. These individuals are trained to recognize the presence of a contaminant and understand the necessary steps to take in order to mitigate the risk it poses to humans and the environment. Reporting the release to the proper authorities is critical to ensure a timely and appropriate response to manage the contamination and minimize any potential harm.