The paper reports the results of a study on occupational risks of a group of sewage workers of the city of Genoa vs. a control group of nonexposed subjects; the first group was divided into three subgroups according to the job characteristics. After bibliographical research on the topic, a specific questionnaire was used to analyse individual symptoms. Clinical examinations, blood and respiratory tests were also performed. The statistical analysis was performed by evaluating F test for differences between parametric measures and the relative risk for non-parametric findings. The relative risk of alterations in respiratory function (both instrumental and clinical findings) was increased among the water treatment workers. The average platelets count in the exposed workers appeared to be significantly reduced compared to non-exposed subjects although both were within the normal limits. There was non evidence of an increased prevalence of positive A hepatitis markers in the exposed workers.