BACKGROUND: Limited studies have suggested that male reproductive function might be associated with exposure to polycyclic aromatic hydrocarbons (PAHs).

METHODS: Five hundred and thirteen idiopathic infertile male subjects and 273 fertile males as controls were recruited in this study, through eligibility screening procedures. Individual exposures to PAHs were measured as spot urinary concentrations of four PAH metabolites, including 1-hydroxynaphthalene (1-N), 2-hydroxynaphthalene (2-N), 1-hydroxypyrene (1-OHP) and 2-hydroxyfluorene (2-OHF), which were adjusted by urinary creatinine (CR). Subjects with idiopathic infertility were further divided into 'normal' and 'abnormal' semen quality groups based on their semen volume, sperm concentration, sperm number per ejaculum and sperm motility.

RESULTS: The median CR-adjusted urinary concentrations of 1-N, 2-N, 1-OHP, 2-OHF and Sum PAH metabolites (sum of all four metabolites) of control group were lower than those found in case groups. Subjects with higher urinary concentrations of 1-OHP, 2-OHF and Sum PAH metabolites (assessed as tertiles) were more likely to have idiopathic male infertility (P-value for trend = 0.034, 0.022 and 0.022, respectively). Comparing the two groups of idiopathic infertile subjects with different semen quality, a higher idiopathic infertility risk was found in the group with abnormal semen quality.

CONCLUSIONS: Increased urinary concentrations of 1-OHP, 2-OHF and Sum PAH metabolites were associated with increased male idiopathic infertility risks, while the idiopathic infertile subjects with abnormal semen might be at higher risk.