Lung deposition and clearance of microparticle and nanoparticle C60 fullerene aggregates in B6C3F1 mice and Wistar Han rats following nose-only inhalation for 13 weeks

C-60 fullerenes (C-60) are spherical structures consisting of 60 carbon atoms that are generated via combustion from both natural and anthropogenic sources. C-60 are also synthesized intentionally for industrial applications. Individual C-60 structures have an approximate diameter of 1 nm; however, C-60 readily forms aggregates and typically exist as larger particles that range from nanometers to micrometers in diameter. In this report, lung and extrapulmonary tissue deposition and lung clearance of C-60 nanoparticles (nano-C-60, 50 nm) and microparticles (micro-C-60, 1 mu m) were examined in Wistar Han rats and B6C3F1/N mice after nose-only inhalation for 90 days. Exposure concentrations were 0.5 and 2 mg/m(3) (nano-C-60) and 2,15, and 30 mg/m(3) (micro-C-60). For both C-60 particle sizes, the C-60 lung burden increased proportionally to exposure concentration. The C-60 lung burden was greater in both species at all time points following exposure to nano-C-60 particle exposure compared to micro-C-60 exposure at the common exposure concentration 2 mg/m(3). The calculated C-60 particle lung retention half-times were similar for both nano-C-60 and micro-C-60 exposure at 2 mg/m(3) in male mice (15-16 days). In contrast, in male rats, the half-time of C-60 particles following nano-C-60 exposure (61 days) was roughly twice as long as the half-time following micro-C-60 exposure (27 days) at the same exposure concentration (2 mg/m(3)) and was similar to the clearance following micro-C-60 exposure at higher exposure concentrations (15 and 30 mg/m(3)). C-60 was detected in bronchial lymph nodes but the burden was not quantified due to the high variability in the data. C-60 concentrations were below the experimental limit of quantitation (ELOQ) in liver, spleen, blood, brain and kidney tissues. These tissue burden data provide information for comparison between nanometer and micrometer sized C-60 particle exposure and will aid in the interpretation of toxicity data. Published by Elsevier Ireland Ltd.