Pulmonary response to toner, TiO2 and crystalline silica upon chronic inhalation exposure in syrian golden hamsters

A chronic inhalation study of a test toner, TiO2, and crystalline silica was conducted by exposure of groups of Syrian golden hamsters (strain: Han:AURA) for 6 h/day, 5 days/wk for 18 mo. Subsequently, the animals inhaled clean air only for an additional period of 5 mo. The target test aerosol exposure concentrations were 1.5, 6, and 24 mg/m3 for the test toner, 40 mg/m3 for TiO2, and 3 mg/m3 for SiO2. The latter two materials were used as negative and positive controls for fibrogenicity. The aerosol concentrations were charged to 4, 16, and 64 mg/m3 for toner (referred to as toner low, toner medium, and toner high) and 30 mg/m3 for TiO2 after 5 mo, in order to achieve the disired lung burdens. Inhalation of the test toner or the control materials showed no signs of overt toxicity.