A 2-year inhalation study of phosphine in rats

Phosphine is a highly toxic gas used as a fumigant, a dopant in semiconductor manufacturing, and in the production of organophosphines. In a chronic toxicity and oncogenicity study of phosphine, 60 male and female F344 rats per group were exposed via whole-body inhalation for 6 h/day, 5 days/wk for up to 104 wk to mean concentrations of 0, 0.3, 1, or 3 ppm phosphine. Three parts per million was considered the maximum exposure level because of lethality seen at higher exposure levels in previous repeat dose studies. Ten rats per sex per group were sacrificed after 52 wk of exposure. Survivors were sacrificed after 104 wk of exposure. There were no phosphine-related effects seen on clinical observations, body weight, food consumption, hematology, clinical chemistry, urinalysis, or ophthalmology. There were no phosphine-related macroscopic findings or effect on absolute or relative organ weights. No histomorphologic alterations attributable to phosphine exposure were seen. In conclusion, under the conditions of this study, there were no treatment-related changes suggestive of a toxic or carcinogenic effect seen in rats following 52 wk or 2 yr of whole-body inhalation exposure to 0.3, 1, or 3 ppm phosphine.