Studies on the effects of exposure to diesel exhaust, by itself or in conjunction with dust, on respiratory morbidity in salt, metal, potash, trona, and coal miners were reviewed. Potentially hazardous substances in diesel exhaust include nitrogen oxides, sulfur oxides, carbon-monoxide (630080), aldehydes, hydrocarbons, and particulate matter. A total of 5747 workers in 27 mines were studied. Each worker was given a detailed questionnaire regarding respiratory symptoms and smoking habits. A detailed industrial history was also taken and simple spirometry was performed. Respirable dust samples in metal and coal mines, and total dust samples in the nonmetal mines were collected by personal gravimetric methods and the quartz percentage was determined. Personal samples of nitrogen-dioxide were obtained using dosimeters. Carbon-monoxide, carbon-dioxide, and aldehydes were measured in each work area. Estimated cumulative diesel exposures were calculated for each worker. Results showed no consistent effects due to diesel emissions. Most results were either mixed or negative. There were no effects in relation to nitrogen-dioxide exposure. Various qualitative indicators of diesel use failed to show any consistent trend with symptoms and lung function. The authors conclude that the data have statistical limitations such as the "healthy worker effect", lack of local controls, low exposure levels, and availability of past exposure data, and that follow up studies are indicated. They also note that none of these studies was designed to address the carcinogenic potential of diesel emissions.