A study of the effects of ethylene-dibromide (106934) (EDB) on semen quality in fumigation workers with long term EDB exposure was conducted. The cohort consisted of 46 males employed at six papaya fumigation facilities in Hawaii. The comparisons consisted of 43 males employed in a sugar refinery. Semen samples were obtained and sperm counts were performed. Parameters of sperm quality such as percentage of viable and motile sperm, sperm velocity, sperm with normal morphology, prevalence of abnormal sperm (tapered heads, absent heads, and abnormal heads), and the presence of YFF bodies were evaluated. The subjects were given questionnaires that sought demographic data and information on medical history, smoking and drinking habits, work history, and current and previous exposure to chemical and physical hazards. Breathing zone samples were analyzed for EDB. Average exposure of the cohort was 5 years. Breathing zone EDB exposures averaged 88 parts per billion (ppb). The proposed OSHA standard for an 8 hour exposure is 100ppb. The current OSHA standard is 20 parts per million. The exposed workers had statistically significant decreases in sperm counts per ejaculate and in percentages of viable and motile sperm. Increases in the numbers of abnormal sperm after correcting for smoking, alcohol consumption, history of urogenital disorders, and other potentially confounding factors were also observed. The other parameters of sperm quality were not affected by EDB. The authors conclude that long term exposure to EDB at concentrations near the recommended NIOSH standard of 45ppb may increase the risk of reproductive impairment.