Manganese in blood cells as an exposure biomarker in manganese-exposed workers healthy cohort

Elevated exposure to manganese (Mn) has long been a public health concern. However, there is currently no consensus on the best exposure biomarker. Here we aimed to investigate the exposomic characteristics of plasma metals among Mn-exposed workers and explore the potential biomarkers of Mn exposure in the blood pool. First, total sixteen plasma metals (Calcium, Magnesium, Iron, Zinc, Copper, Selenium, Lead, Chromium, Arsenic, Manganese, Nickel, Molybdenum, Cadmium, Mercury, Thallium, and Cobalt) were determined among 40 occupationally Mn-exposed subjects. Second, Mn levels in both plasma and blood cells were detected among 234 workers from the manganese-exposed workers healthy cohort (MEWHC), respectively. Analysis of plasma metal exposome showed that the plasma Mn concentrations were positively correlated to plasma Fe (r = 0.361), Ni (r = 0.363), Cr (r = 0.486), and Hg (r = 0.313) (all p < 0.05). Mn concentrations in plasma were not significantly correlated to external exposure levels (ptrend = 0.200), and it was further confirmed among the 234 subjects (ptrend = 0.452). However, Mn concentrations in blood cells progressively increased as the external exposure dose increased (low-exposure group vs high-exposure group, median 11.53 μg/L vs 20.41 μg/L, ptrend = 0.001). Our results suggest that Mn in blood cells, but not plasma, could serve as a potential internal exposure biomarker. Larger validation studies are needed to establish the utility of this biomarker.