Assessment of the potential reproductive toxicity of long-term exposure of adult male rats to low-dose formaldehyde

Formaldehyde (FA), a ubiquitous environmental pollutant, is extensively used in hospitals, laboratories and many industrial settings. Previous studies have showed that short-term, high-dose FA exposure is toxic to male reproduction of mammals. In this paper, we evaluated the male reproductive toxicity of long-term, low-dose formaldehyde exposure in rats, and explored the potential mechanisms. A total of 30 Sprague-Dawley male rats were randomly allotted to three groups, rats were exposed to FA at a dose of 0 (control), 0.5, 2.46 mg/m3 respectively by inhalation for consecutive 60 days. The results indicated that the reproductive toxicity of FA is dose-dependent. Testicular, epididymal structure and function in rats of 0.5 mg/m3 FA exposure group showed no obvious difference compared with those in control group. However, sperm quantity and quality, testicular seminiferous tubular diameter, the activities of superoxide dismutase and glutathione peroxidase was significantly decreased whereas the level of malondialdehyde was significantly increased in rats of 2.46 mg/m3 FA exposure group compared with those in control group. Moreover, histopathological results showed atrophy of seminiferous tubules, decreases of spermatogenic cells and the lumina were oligozoospermic in testes of 2.46 mg/m3 FA exposure rats. In conclusion, the level of 0.5 mg/m3 can be considered as a safe level for FA exposure, but long-term FA exposure at a dose of 2.46 mg/m3 has a harmful effect on male reproduction by inducing oxidative stress in male rats.