We have previously reported on respiratory symptoms dust and endotoxin exposure within workers exposed to organic dusts. These show increasing symptoms with both increased exposure to dust and airborne endotoxin exposure. However the relative effects of dust and endotoxin were difficult to separate out. In all the industries higher dust levels were associated with increased endotoxin exposure. We are currently studying sewage workers who are potentially exposed to endotoxin but not to dust to determine the respiratory effects of endotoxin exposure alone on respiratory symptom reporting.