Association between occupational LiFePO 4 exposure and cardiac autonomic function: a cross-sectional study of cathode material production workers

Objectives Lithium (Li) and iron (Fe) are the primary components of LiFePO4 (LFP), a cathode material used in lithium-ion batteries. Both elements have attracted attention due to their cardiovascular toxicity. This study aims to investigate the effects of the emerging nanomaterial LFP on the autonomic nervous function of workers’ hearts. Methods The heart rate (HR) and heart rate variability (HRV) indicators of 318 LFP production workers were collected using a dynamic ECG monitor, and the urine Li, whole blood Fe, and serum ferritin levels of the workers were measured. A covariate-adjusted linear model was employed to examine the association between metal exposures and cardiac function indicators. Furthermore, interaction effects of metal exposures were explored, and a stratified analysis was performed based on the influencing factors of HRV. Results In the covariate-adjusted linear model, per doubling of urinary Li was related to a 2.28 (95% CI 1.25 to 3.33) beats per minute increase in HR and a 5.98% (95% CI −9.87% to −1.85%) reduction in SD of normal-to-normal intervals (SDNN). Meanwhile, each twofold increase in Fe exposure markers was associated with a decrease of 22.62% (95% CI −32.87% to −10.75%) in SDNN, 58.53% (95% CI −77.62% to −23.16%) in high-frequency power and 57.37% (95% CI −74.83% to −27.80%) in total power, respectively (all PFDR<0.05). In addition, there is a positive interaction between whole blood Fe, urinary Li and increased HR (β>0, Pinteraction=0.036). Conclusions Our study suggests that metal exposures in LFP production workers are associated with increased HR and impaired autonomic nervous system function.