Effects of inhalation of red phosphorus/butyl rubber combustion products on aveolar macrophage responses in rats

The effects of inhalation of red phosphorus/butyl rubber (RP/BR) used as an obscurant smoke in tactical environments was examined. Sprague-Dawley male rats were exposed to 1000 mg/m3 of RP/BR for 3.5 h in single exposures, while in subsequent intermediate and subchronic studies the animals were exposed to concentrations ranging from 300 to 1200 mg/m3 for 2.25 h/day, 4 consecutive days/week for 4 and 13 weeks, respectively. Pulmonary bactericidal activity to inhaled [35S]-Klebsiella pneumoniae was depressed after the acute and the 13-week subchronic exposures but was unchanged after the 4-week exposures. The pulmonary free cells collected by lavage showed decreasing trends in total numbers, increased ATP levels and decreased ectoenzyme activity for 5'-nucleotidase after most of the exposures. Mild-to-moderate-to-severe terminal broncheolar fibrosis was observed in all rats after 4- and 13-week exposures to greater than or equal to 750 mg/m3 of RP/BR. The severity of the lesions increased with the severity of the exposure conditions. Except for the fibrosis, most changes were reversible.