Lung response to test toner upon 2 year inhalation exposure in rats
SPF F-344 rats were exposed to a special test toner by the inhalation route. The animals were kept for an additional six weeks in filtered air. Surviving animals were sacrificed at 25.5 months after start of exposure. Life-span and causes of death were independent of treatment and in accordance with published values. No evidence for systemic toxicity or any upper-respiratory system effects were found in the toner exposed groups. The incidence of lung tumors was comparable in the control, 3 toner and Ti02-exposed groups. An incidence of 18% combined benign and malignant tumors was observed in the quartz treated rats. A slight to moderate degree of fibrosis was observed at the toner high exposure level in all animals, while a very slight degree of fibrosis was noted in 20% of the animals at the toner middle exposure level. The fibrogenic potency of the test toner was calculated to be comparable to Ti02. No pulmonary changes were seen at the toner low and environmentally most relevant exp osure level.