Hydrologists know what should be in water - they know what is safe and what is aberrant and harmful. For that reason, hydrologists are employed on government task forces concerned with public safety. Their job is to determine which chemicals absolutely must not occur in any water source. These are important policies with wide-reaching ramifications. Some manufacturing plants and mills may have to make integral changes to their production methods, and those changes can be costly and publicly awkward. Contaminant policy making hydrologists must have the courage and respect for public safety to stand up to the interests of businesses and lobbyists.