While manganese (Mn) is known in the pre-clinical community as a T1 contrast agent, it is also notorious as a neurotoxin that can cause irreversible parkinsonian symptoms at high enough exposure levels. In an occupational setting, workers are exposed to Mn through processes such as welding, smelting, and other metalwork. As the workload changes over time, so does the level of exposure. Using MRI and MRS, effects of exposure such as elevated thalamic GABA levels and brain Mn deposition can be detected and show evidence of reversibility. This may help identifying meaningful no-observed-adverse-effect levels (NOAEL) as used in occupational settings.