Objective:

To explore the associations between metal mixtures in seminal plasma and sperm quality metrics, and to examine the mediating role of urinary oxidative stress markers.

Approach:

• Study Design: A cross-sectional cohort study involving 425 men from the RHCC-AC, measuring 17 metals in seminal plasma and 8 urinary oxidative stress biomarkers.
• Statistical Analysis: Weighted quantile sum (WQS) regression was used to assess the effects of metal mixtures, and exploratory mediation analysis was conducted to evaluate the role of oxidative stress.

Key Findings:

• Al was positively associated with sperm abnormality rate (β = 0.014; 95% CI: 0.004–0.024).
• Co and Cu were inversely associated with progressive motility (β = −0.188; 95% CI: −0.309 to −0.067) and total motility.
• As, Fe, and Se were positively associated with sperm concentration.
• In mixture analyses, Al was the primary contributor to increased sperm abnormality rate, while Co was the main contributor to reduced total motility.
• D,L-ortho-tyrosine mediated the associations of Hg and V with sperm concentration, with mediated proportions of 11.8% and 13.0%, respectively.

Interpretation:

Certain metal mixtures in seminal plasma are associated with sperm quality, with oxidative stress markers potentially mediating some of these associations.

Limitations:

• The findings are exploratory and should be interpreted cautiously.
• Further studies using seminal or reproductive tract-specific oxidative stress biomarkers are warranted to clarify the role of oxidative stress in linking metal exposure to male reproductive health.

Conclusion:

Seminal plasma metal mixtures, particularly Al and Co, were associated with sperm quality, and oxidative stress markers may play a mediating role.