Exposures to sulfur-dioxide (7446095) (SO2) are reviewed. Worker complaints of effects of SO2 are cited, including nasal and throat irritation, coughing, sneezing, nasal discharge, and more seriously, chronic bronchitis, emphysema, shortness of breath, and death. The history of the NIOSH priority of occupational exposures to SO2 and the proposal of a standard for exposure of 2 parts per million (ppm) is noted. Epidemiological studies are described that indicate statistically significant increases in respiratory diseases among workers exposed to SO2 and among the general population as the result of air pollutants. Evidence of mutagenicity and the cancer promotion of benzopyrene (50328) by SO2 is noted. Health effects of SO2 exposure are considered in the recommendation of a new standard of 0.5ppm for a time weighted average work day. The need for preplacement and annual physical examinations, particularly where SO2 exposures exceed 0.25ppm is stressed. The author recommends that employee information, training, and medical records should be maintained for at least 30 years after termination of employment for research on the effects of prolonged exposure.