Risk management offers us insights into this question. Environmental health professionals would most likely answer that our purpose is to save lives. But politicians, long known for saving face, would usually have final word in the form of law. All of these answers play a role. Risk analysis is a broad term that represents a collection of approaches and disciplines devoted to all aspects of risk issues.
Risk assessment is the characterization of adverse effects from exposure to hazards.
Hazard identification is to determine whether a particular agent is causally linked to particular health effects. Dose-Response Assessment is to determine the relation between the magnitude of exposure and the probability of occurrence of health effects in question. Risk characterization is to describe the nature and often the magnitude of human risk, including attendant uncertainty. Risk communication is an interactive exchange of information and opinions among individuals, groups, and institutions regarding risk. Risk management is the evaluation, selection, and implementation of alternative risk control actions.