The acute and subacute inhalation toxicity of highly purified phosphine (PH3, CAS No. 7803-51-2, 99.995%) in male ICR mice was investigated. LC50 for one-hour exposure was greater than 59.2 ppm and that for four-hour exposure was between 26.5 ppm and 33.4 ppm. Experiments involving acute exposure to 25 ppm PH3 for one, two, four or eight hours, and subacute exposure to 5 ppm PH3 for six hours/day, five days/week, for two or four weeks were conducted. All mice subjected to acute eight-hour exposure died but a histopathological examination failed to reveal the actual causes of death. In the nasal cavity, exposure-time related inflammatory changes were observed in the acute two-, four-, and eight-hour exposure groups, and in the subacute four-week exposure group. Other histopathological, hematological, and serum biochemical examinations did not reveal PH3-related changes. Further study is necessary to assess the actual effects of PH3 on the cause of death.
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