Respiratory exposure to carbon black nanoparticles may induce testicular structure damage and lead to decreased sperm quality in mice

Environmental carbon black nanoparticles (CBNPs) can enter into various organs including testes through the respiratory tract. However, there are few studies describing reproductive toxicity of CBNPs after respiratory exposure. In this study, male KM mice were exposed to CBNPs in their natural breathing state. Four-, 8-, and 12-week-old mice were exposed to 0, 9, 18 and 27 mg/m3 of CBNPs for 4 weeks in order to examine the relationship between CBNP exposure and age. Eight-week-old mice were exposed to CBNPs at the same four concentrations for 1-4 weeks in order to examine the effects of CBNP exposure time. After CBNP exposure, testicular oxidative stress and inflammation increased significantly, and these effects varied with exposure time. Seminiferous tubule diameter (STD), seminiferous epithelium height (SEH), the number of spermatogenic and Leydig cells, sperm motility, and sperm speed decreased significantly, and these effects varied with exposure dose. Data analyses suggested that increased oxidative stress and inflammation in testes damaged testicular morphology, spermatogenesis, and testosterone secretion, and decreased sperm quality. Morphological damage to the testes was also closely related to decreased the sperm quantity. These findings are of significance for evaluating the reproductive toxicity of CBNPs.