Identifying windows of susceptibility to essential elements for semen quality among 1428 healthy men screened as potential sperm donors

•Urine and semen samples were repeatedly collected among 1428 healthy men.•Urinary Fe, Co, Cu, Zn, Se, Rb, Sr, and Mo showed high within-subject variations.•Higher urinary Zn and Mo levels were associated with greater sperm production.•The period of epididymal storage may be the critical window of susceptibility to Zn and Mo. Essential elements such as iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), selenium (Se), rubidium (Rb), strontium (Sr), and molybdenum (Mo) are necessary for reproductive health. However, their associations with human semen quality remain inconclusive. To investigate the associations of urinary Fe, Co, Cu, Zn, Se, Rb, Sr, and Mo concentrations with semen quality in healthy men screened as potential sperm donors and identify critical windows of susceptibility. 1428 healthy men provided 3766 urine and 6527 semen samples, which were measured for urinary essential element concentrations and sperm quality parameters, respectively. Linear mixed models and cubic spline curves were used to evaluate associations between urinary essential elements and semen quality. Multiple informant models were used to identify potential critical windows of susceptibility. Linear mixed models and cubic spline curves showed positive dose–response relationships between urinary Zn and sperm concentration and total count and between urinary Mo and total sperm count [all False Discovery Rate (FDR) adjusted p-value for trend