The Health Effects Research Laboratory of the U.S. Environmental Protection Agency arranged for several studies, by universities or research institutions, to gather information on health effects associated with wastewater aerosols. Five studies were conducted at wastewater treatment plants and all have been completed. The comprehensive investigations described leave little doubt that working at or living near a wastewater treatment plant does not present a microbiological hazard to the people from the aerosols. However, it should always be kept in mind that sewage contains pathogenic agents and the potential for infection or illness is present.