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BACKGROUND: Developmental neurotoxicity (DNT) is a well-established hazard of methylmercury (MeHg) exposure. Past research on MeHg has highlighted DNT tests of language/verbal function (in particular the Boston naming test (BNT)) as an important aspect of MeHg toxicity. METHODS: We conducted a meta-analysis based on a recent systematic review of MeHg neurodevelopmental dose-response cohort studies published 1998-2025 that reported similarly normed tests of language/verbal function. Meta-analyses were based on recent studies using maternal blood biomarkers or cord blood biomarkers converted into maternal blood biomarkers. RESULTS: For the BNT with or without cues, analysis (based on 2 studies (3 populations)) results were adverse, but not statistically significant. For the similarly normed language/verbal tests, decrements were statistically significant -0.0085 95% (-0.0167; -0.0003) per MeHg µg/L maternal blood (based on eight studies). Results of a fill and trim sensitivity analysis were similar in the size of the effect to the original results. The two studies with sex-specific results indicated that boys appeared to be more sensitive to MeHg-related language/verbal function decrements when compared with girls. CONCLUSIONS: Although most of the individual study results of language/verbal function were not statistically significant, the meta-estimate showed a statistically significant decrement in language/verbal function in children due to prenatal MeHg exposure.
Kopylev et al. (Mon,) studied this question.