Peripheral and central auditory impairment linked to heavy metal exposure in Nicaraguan children from artisanal mining communities

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Background: Children living in artisanal and small-scale gold mining (ASGM) communities are exposed to numerous metals with possible ototoxic and neurotoxic effects. Tests of peripheral and central auditory function can reflect toxicity to the ear and brain, respectively. This study investigated the link between metal exposure and peripheral and central auditory processing (CAP) in children exposed to metals in ASGM settings. Methods: In a cross-sectional study, 211 children aged 6-18 in ASGM communities performed audiometric (pure-tone audiometry, PTA) and CAP assessments (dichotic digits test, DDT). Toenail samples were analysed for 21 metals. Data on noise exposure and other covariates were collected via questionnaire. Linear and Elastic Net regression models were used to identify predictors of auditory impairment. Results: Median metal concentrations except chromium (Cr) and selenium (Se) exceeded published reference values. For CAP assessments, several metals were identified by Elastic Net (lead (Pb), antimony (Sb), uranium (U), vanadium (V)) and linear regression (aluminium (Al), cadmium (Cd), cobalt (Co), Cr, copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), strontium (Sr), thallium (Tl), U, V), respectively. Both methods identified U and V as potential predictors. For peripheral auditory function, Elastic Net selected silver (Ag), Cd, Cr, Hg, and molybdenum (Mo), while linear regression identified Ag, arsenic (As), Co, Cr, Cu, Hg, Mn, Mo, Pb, Sr, and Tl. Silver (Ag), Cr, Hg, and Mo were consistently selected by both methods. At high-frequency peripheral thresholds, Elastic Net identified As, nickel (Ni), Pb, and tin (Sn), and linear regression identified Ag, Al, As, Cd, Co, Cu, Fe, Hg, Mn, Mo, Pb, and V. Both analyses selected As and Pb as potential predictors. Conclusions: CAP and peripheral auditory test performance correlated with metals known to have ototoxic and neurotoxic effects, as well as metals with previously unrecognised neurotoxic potential. These findings support measuring multiple metals in future epidemiologic studies to examine potential metal toxicities beyond those with known neurotoxicity.

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