Pulmonary response to toner upon chronic inhalation exposure in rats.

A chronic inhalation study of a test toner was conducted by exposure of groups of F-344 rats for 6hr/day, 5 days/week for 24 months. The test toner was a special Xerox 9000 type xerographic toner, enriched in respirable-sized particles compared to commercial toner. The target test aerosol exposure concentrations were 0, 1,0 (low), 4,0 (medium), and 16,0 (high) mg/mhigh3. Titanium dioxide (5 mg/mhigh3) and crystalline silicon dioxide (1 mg/mhigh3), used as negative and positive controls for fibrogenicity, were also evaluated. The incidence of primary lung tumors was comparable among the three toner-exposed groups and the TiO2 exposed, and air-only controls. A mild to moderate degree of lung fibrosis was observed in 92 per cent of the rats in the toner high-exposure group.