Molecular epidemiological study of urinary metal mixtures and lipid oxidative damage

Objective To explore the main toxic components of metal mixtures in urine responsible for lipid oxidative damage based on the statistical model of mixed pollutants.

Methods A total of 768 participants in a iron and steel smelting plant were recruited and their urine was collected. Urinary concentrations of vanadium(V), chromium(Cr), manganese(Mn), nickel(Ni), arsenic(As), strontium(Sr), cadmium(Cd), lead(Pb), selenium(Se), cobalt(Co), copper(Cu), and zinc(Zn) were determined by inductively coupled plasma mass spectrometry. The concentration of urinary 8-iso-prostaglandin F2α (8-iso-PGF2α) was measured by ELISA. The concentration of urinary malondialdehyde (MDA) was determined by the MDA-thiobarbituric acid adduct method. Bayesian kernel machine regression (BKMR) and quantile g-computation were performed to analyze the associations of urinary metals with urinary 8-iso-PGF2α and MDA levels.

Results BKMR analysis showed that the total effect of mixed metal exposure increased the levels of 8-iso-PGF2α and MDA in urine (P < 0.05) when all urinary metal concentrations were at the 50th percentile (P₅₀). Urinary 8-iso-PGF2α level increased by 36.72% and urinary MDA level increased by 34.24% when all urinary metal concentrations were at P₅₀ as compared with P₂₅. The main components in metal mixtures responsible for lipid oxidative damage were Se, Cd, and Zn. When other urinary metals were fixed at P₂₅, P₅₀, and P₇₅, urinary 8-iso-PGF2α levels increased by 30.7%, 35.4%, and 41.2% and urinary MDA levels increased by 35.3%, 42.8%, and 54.7% with each interquartile range increase in urinary Se. Quantile g-computation showed that 25% increase of the metal mixture levels resulted in 63.05% increase of urinary 8-iso-PGF2α and 61.23% increase of urinary MDA, respectively.

Conclusion Exposure to metal mixture increases the levels of lipid oxidative damage, and the effects of Se, Cd, and Zn are more significant.