Environmental Neurotoxin Exposure and Subclinical Cognitive Decline in Industrial Workers

Abstract

Background: Chronic occupational exposure to neurotoxic substances may be associated with subtle cognitive changes before the development of clinically evident neurological disease. Industrial workers in settings with potential exposure to lead, mercury, and organic solvents may be particularly vulnerable, yet evidence from Pakistan remains limited. Objective: To assess the association between chronic low-level occupational exposure to lead, mercury, and solvent metabolites and subclinical cognitive decline among industrial workers in Punjab, Pakistan. Methods: This cross-sectional analytical study included 300 industrial workers aged 25–55 years from chemical manufacturing, metal processing, and textile sectors. Cognitive performance was assessed using the Mini-Mental State Examination, Stroop Test, Wisconsin Card Sorting Test, and Digit Span Test. Exposure was assessed through blood lead level, blood mercury level, urinary solvent metabolites, and workplace exposure assessment. Correlation and regression analyses were used to examine exposure–cognition associations, with adjustment for age, education, and work history. Results: Chemical manufacturing workers had the highest mean blood lead level at 18.2 µg/dL and the poorest cognitive profile, including the lowest MMSE score of 25.3, lowest WCST score of 50.7, and longest Stroop completion time of 50.2 seconds. Metal processing workers had the highest mercury level at 7.5 µg/L and solvent metabolite level at 2.3 mg/L. Higher lead, mercury, and solvent exposure markers were significantly associated with poorer Stroop, WCST, MMSE, and Digit Span performance. Conclusion: Higher occupational neurotoxin exposure was associated with poorer cognitive performance among industrial workers, particularly in attention, processing speed, working memory, and executive function. Longitudinal studies are needed to clarify causality.