Mixed exposure to lithium-battery related metals and menstrual health among young Chinese women: A cross-sectional study.

Environmental contamination from lithium battery waste poses health risks, but the impacts of constituent metals (Li, Ni, Co, Mn) on menstrual health are unclear. This study investigated associations between blood concentrations of these metals and menstrual characteristics in 504 healthy young women. Metals concentrations in whole blood were measured using inductively coupled plasma mass spectrometry. The qgcomp, BKMR, and SHAP models were used to analyse the association and contribution of mixed metal exposure to menstrual outcomes. The average concentrations of whole blood Ni, Li, Co, and Mn of participants reached 1.16, 0.94, 0.27, and 2.87 ng·mL-1. Single-metal analyses showed that Co and Mn were significantly negatively correlated with menstrual cycle, while Li was positively correlated with menstrual bleed duration. The overall metal mixture demonstrated negative associations with menstrual cycle and positive associations with menstrual bleed duration. Specifically, increasing Co (25th to 50th percentile) significantly decreased cycle length (-0.684 days [95 %CI: -1.025, -0.341]), while increasing Li significantly increased duration (0.557 days [95 %CI: 0.133, 0.981]), with other metals fixed at the 25th percentile. These findings highlight environmentally relevant Co and Li exposure as potential modifiable risk factors for female reproductive health disturbances.