Infectious risk associated with wastewater reuse: an epidemiological approach applied to the case of Clermont-Ferrand, France

Wastewater reuse raises the question of health risk and the epidemiological surveys needed. An epidemiological and environmental approach was used to check the security for the exposed populations (surrounding and agricultural population in Clermont-Ferrand. Four information systems were set up: two sentinel systems joining general physicians (15) and pharmacists (7) for the surrounding population and two follow-up surveys among field workers and farmers. Water quality monitoring and a study of aerosols from spray irrigation were performed. No epidemic event was identified with only some case clusters (not related to water exposure) being observed. All the declared cases were benign. The workers' survey underlined a substantial incidence of nettle rashes, itchy skins, sunburns, and cuts. The follow-up study among farmers and their families did not reveal any particular phenomena. The bacteriological quality of treated wastewater throughout conformed with the recommendations of the Superior Council of Public Health of France (1,000 faecal coliforms/100 mL). No faecal bacteria were observed in aerosols with water concentrations equal to 10(3) cfu/100 mL and an exposure time of 20 min. The survey of such an irrigation system, towards potential and actual risks, required the conjunction of different epidemiological information sources and microbiological data.