Metal and metalloid exposure and cognitive function among copper mine workers: A three-year longitudinal study

Occupational exposure to heavy metals is increasingly recognized as a threat to neurological health. This three-year longitudinal study investigated the relationship between heavy metal exposure and cognitive performance among 69 copper miners and 74 non-miner controls. Blood concentrations of heavy metals were determined using atomic absorption spectrophotometry, while cognitive performance was assessed with standardized neuropsychological tests, including the Mini-Mental State Examination (MMSE), Symbol Digit Modalities Test (SDMT), Paced Auditory Serial Addition Test (PASAT), Psychomotor Vigilance Task (PVT), creativity measures, and the Beck Depression Inventory. The results demonstrated significantly higher blood levels of arsenic and lead in miners compared with controls, whereas copper levels showed no meaningful group difference. Elevated arsenic concentrations were strongly associated with reduced performance on the oral SDMT, reflecting impairments in information processing speed and working memory. Longitudinal analyses confirmed persistent group differences in neurocognitive outcomes, with age and education exerting notable modifying effects. Interestingly, miners consistently exhibited lower depression scores across the study period, despite greater exposure to toxic metals. These findings indicate that chronic occupational exposure to arsenic and lead contributes to subtle but measurable cognitive deficits in copper miners, particularly in domains of working memory and processing speed.