Background: Acute exposure to environmental chemicals can result in loss of consciousness and upon recovery neurological symptoms, but little evidence exists in large epidemiological human studies. Hence, it was aimed to determine the relationships between urinary environmental chemicals (including heavy metals, environmental bisphenols, pesticides, arsenic, and phthalates) concentrations and vision, hearing, and balance disorders in a national population-based setting.
Methods: United States National Health and Nutrition Examination Surveys is a national population-based multi-year cross-sectional study. Information on demographics and vision, hearing, and balance disorders was obtained by household interview using questionnaires in the 2003-2004 cohort (aged 50 and above). Urinary environmental chemicals were detected by mass spectrometry in selected but representative people. Analyses involved logistic regression models.
Results: Urinary cadmium, molybdenum, and tungsten concentrations, which are commonly associated with heart disease, were associated with vision disorder. Urinary 2,4,5-trichlorophenol and arsenic acid concentrations and circulating mono-n-butyl phthalate, mono-benzyl phthalate, and mono-(3-carboxypropyl) phthalate metabolites were significantly associated with hearing disorder. Moreover, urinary barium and 4-tert-octyl-phenol concentrations were associated with balance disorder. People who had ears ringing, roaring, or buzzing in the past year tended to have higher urinary barium, 2,4-dichlorophenol, and mono-benzyl phthalate concentrations.
Discussion: Significant correlations were observed in urinary environmental chemicals and neurobehavioural impairment for the first time. However, the causation cannot be established due to its cross-sectional study design. Future studies with a longitudinal aspect and/or in clinical trials are warranted to clearly understand the biological mechanism along the pathway before drawing a firm conclusion on these relationships.
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