Association and mediation analyses among multiple metal exposure, mineralocorticoid levels, and serum ion balance in residents of northwest China

Toxic metals are vital risk factors affecting serum ion balance; however, the effect of their co-exposure on serum ions and the underlying mechanism remain unclear. We assessed the correlations of single metal and mixed metals with serum ion levels, and the mediating effects of mineralocorticoids by investigating toxic metal concentrations in the blood, as well as the levels of representative mineralocorticoids, such as deoxycorticosterone (DOC), and serum ions in 471 participants from the Dongdagou-Xinglong cohort. In the single-exposure model, sodium and chloride levels were positively correlated with arsenic, selenium, cadmium, and lead levels and negatively correlated with zinc levels, whereas potassium and iron levels and the anion gap were positively correlated with zinc levels and negatively correlated with selenium, cadmium and lead levels (all P < 0.05). Similar results were obtained in the mixed exposure models considering all metals, and the major contributions of cadmium, lead, arsenic, and selenium were highlighted. Significant dose-response relationships were detected between levels of serum DOC and toxic metals and serum ions. Mediation analysis showed that serum DOC partially mediated the relationship of metals (especially mixed metals) with serum iron and anion gap by 8.3% and 8.6%, respectively. These findings suggest that single and mixed metal exposure interferes with the homeostasis of serum mineralocorticoids, which is also related to altered serum ion levels. Furthermore, serum DOC may remarkably affect toxic metal-related serum ion disturbances, providing clues for further study of health risks associated with these toxic metals.

The Effects of Lead and Cadmium Co-exposure on Serum Ions in Residents Living Near a Mining and Smelting Area in Northwest China

In this study, we investigated the associations between cadmium (Cd) and lead (Pb) co-exposure, and serum ion levels in two populations living near a mining/smelting area and a nature reserve (control area), respectively. A total of 445 participants were included in this study. Their blood cadmium (BCd), blood lead (BPb), and serum ion levels were determined, and the association between exposure levels and serum ion levels was analyzed. The exposure levels of subjects living in the polluted area were significantly higher (p < 0.001). Lower levels of potassium, inorganic phosphorus, and iron were observed in subjects from the polluted area, whereas their sodium and chloride levels were higher (p < 0.01). The anion gap in their serum was also significantly lower. We observed positive dose-effect relationships between Cd and/or Pb exposure and serum sodium and chloride, and negative dose-effect relationships between Cd and/or Pb exposure and serum inorganic phosphorus, iron, as well as the anion gap. High Cd-Pb, high Cd, and high Pb exposure led to modification effects in potassium, calcium, inorganic phosphorus, and iron levels, and the anion gap. No synergistic effects were observed in our results. In conclusion, our data demonstrate that Cd and Pb exposure, alone or in combination, can lead to serum ion imbalances.