Subacute Toxicity Study of Nanoscale Carbon Black Particles by Dynamic Inhalation Exposure in Mice

Objective To investigate the subacute toxicity by dynamic inhalation exposure of nanoscale carbon black particles in mice,and to provide toxicological data for the risk assessment of nanoscale carbon black particles.

Methods Eightweek-old male C57BL/6 mice were randomly assigned into three groups,including negative control group (filtered air),low dose group (15 mg/m³ carbon black particles),and high dose group (30 mg/m³ carbon black particles).With aerosol generator,nanoscale carbon black particles of designed concentrations were blown into chambers,the mice were exposed through inhalation for 6 h per day for 28 d continuously.During the exposure period,the aerodynamic diameter,spatial distribution,and concentrations of carbon black particles were monitored dynamically.In 24 h after the last exposure,venous blood samples were collected for haematologic and clinical biochemical examinations.The heart,lung,liver,spleen,and kidney were dissected and weighed for pathological examination.Differential cell count of bronchoalveolar lavage fluid (BALF) were conducted under microscope and the total protein level in BALF was detected.

Results The concentrations of carbon black particles in the low and high dose groups were (15.31±3.30) mg/m³ and (30.05±14.20) mg/m³ respectively during the 28-day exposure period.No significant differences of body weight and the consumption of feed and water were observed between the control and exposed groups.The blood biochemical indicators showed no changes between the control and exposed groups.Compared with the control group,red blood cells,hemoglobin concentration,and hematocrit increased slightly in the exposed groups (P<0.01 or P<0.05).In comparison with the control and the low dose groups,there was an increasement of the lung organ coefficient in the high dose group (P=0.016);whereas the heart and kidney organ coefficient in the two exposed groups decreased (P=0.001,P<0.01).The histopathologic examination results showed that carbon black particles were deposited in the pulmonary alveoli or bronchioles in the exposed groups,especially in the high dose group,and were swallowed by macrophages in pulmonary interstitial.The pathological score of lung injury in the low and high dose groups were (6.63±1.13) and (9.80±0.38) respectively,both higher than that in the control group (1.66±0.55).Compared with the control group,the total cell counts,lymphocytes,neutrophils,and eosinophils in BALF were higher in the two exposed groups (all Ps<0.01).

Conclusion The 28-day repeated inhalation exposure to carbon black particles could mainly result in lung tissue injury,providing an ideal model and a reliable analytical method for the study of pulmonary toxicological effects induced by nanoscale carbon black particles.