Abstract
Objective: This study aimed to investigate the effects of chronic exposure to water-soluble fractions (WSFs) of spent engine oil (SEO) on male fertility in adult male rats.
Materials and Methods: The study included 40 rats, which were randomized into 4 groups (n = 10) and treated for 45 days with different SEO concentrations. Group A (the control) received distilled water, while Groups B, C, and D were given 0.2 ml of 10%, 50%, and 100% concentrations of WSF of SEO, respectively, via oral gavage.
Results: The study found no significant differences in the gonadometric indices, sperm motility, livability, and sperm concentration among the groups, except for slight changes in the weight and length of the testis and the mean diameter of both testes. However, the study found significant changes in the red blood cell, white blood cell, mean corpuscular hemoglobin, and neutrophil values following exposure to SEO. The mean values of testosterone, luteinizing hormone, and follicle-stimulating hormone did not show any significant alterations in the experimental groups compared to the control group.
Conclusion: It was concluded that chronic exposure to SEO-soluble fractions can adversely affect the body’s physiological and biochemical processes, but it does not appear to have any significant effect on the fertility of male rats. However, further studies are needed to confirm these findings and to investigate the much longer-term effects of SEO exposure on male fertility.

Key words: Fertility; blood; rats; spent engine oil; testes