In this section, “dangerous contaminant” means a contaminant that, if present in a public water system, would present an imminent and substantial danger to the health of individuals. On receipt of information that a dangerous contaminant is present in or likely to enter a public water system, the Secretary may take any action necessary to protect the health of the individuals whose health is or would be endangered by the dangerous contaminant. The actions that the Secretary may take under this section include: Issuing any order necessary to protect the health of individuals who are or may be users of the public water system; and Suing for injunctive or other appropriate relief.