Welding-related brain and functional changes in welders with chronic and low-level exposure

•Manganese (Mn) may accumulate in the brain in a non-linear fashion: MRI R1 signals increased only after a critical level of exposure was reached.•Chronic Mn-exposure may lead to microstructural changes as indicated by lower DTI fractional anisotropy values in the basal ganglia.•Mn-related subtle motor dysfunctions can be captured by synergy metrics (indices for motor stability).•Iron may also play a role in welding-related neurotoxicity, especially at low-level Mn-exposure.