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Chronic Inhalation Exposure of Rats for up to 104 Weeks to a Non–Carbon-Based Magnetite Photocopying Toner

ENVIRON International Corporation, Arlington, Virginia, USA

Correspondence: Address correspondence to Duncan Turnbull, DPhil, DABT, ENVIRON International Corporation, 4350 North Fairfax Drive, Suite 300, Arlington, VA 22203, USA. E-mail:dturnbull{at}environcorp.com

Male and female Han Wistar rats were exposed for 6 h/day, 5 days/week for 13 or 104 weeks (whole body) to a magnetite photocopying toner. The toner contained 45% to 50% magnetite, with 45% to 50% styrene acrylic resin and less than 5% external additives, including hydrophobic amorphous silica and proprietary surface functional modifiers. Exposure levels were 1, 5, and 25 mg/m³ for the 13-week study and 1, 4, and 16 mg/m³ for the 104-week study. Lung toner burdens averaged 36, 288, and 604 µg per lung after 104 weeks’ exposure at 1, 4, and 16 mg/m³. The lung burdens were lower than have been reported in a similar study with a carbon-based toner. There were no significant effects on weight gain or food consumption in either study, or on clinical pathology parameters examined in the 13-week study. After 104 weeks’ exposure at 16 mg/m³, macroscopic examination revealed dark discoloration of the lungs and associated lymph nodes. Lung weights were significantly elevated by 21% and 14% for male and female rats, respectively. Microscopic findings indicative of a mild inflammatory response were similar in both studies, and included the presence of black-pigmented macrophages in the lungs and tracheobronchial and mediastinal lymph nodes; increased incidences of perivascular/peribronchiolar inflammatory cell infiltration; inflammation of the alveolar ducts (characterized by aggregations of black-pigmented alveolar macrophages and interstitial lymphocytic infiltration); increased cellularity of the bronchiole-associated lymphoid tissue; and a few instances of alveolar ciliated metaplasia. The 104-week study showed no increase in the incidence of pulmonary tumors.

Key Words: Chronic • Inhalation • Magnetite • Rats • Toner

International Journal of Toxicology, Vol. 27, No. 6, 427-439 (2008)
DOI: 10.1080/10915810802616560


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