Neurological Impacts of Chronic Methylmercury Exposure in Munduruku Indigenous Adults: Somatosensory, Motor, and Cognitive Abnormalities

Rogério Adas Ayres de Oliveira, Bruna Duarte Pinto, Bruno Hojo Rebouças, Daniel Ciampi de Andrade, Ana Claudia Santiago de Vasconcellos and Paulo Cesar Basta
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Rogério Adas Ayres de Oliveira: Centro de Dor, Departamento de Neurologia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo 05403-000, Brazil
Bruna Duarte Pinto: Centro de Dor, Departamento de Neurologia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo 05403-000, Brazil
Bruno Hojo Rebouças: Centro de Dor, Departamento de Neurologia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo 05403-000, Brazil
Daniel Ciampi de Andrade: Centro de Dor, Departamento de Neurologia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo 05403-000, Brazil
Ana Claudia Santiago de Vasconcellos: Laboratório de Educação Profissional em Vigilância em Saúde, Escola Politécnica de Saúde Joaquim Venâncio, Fundação Oswaldo Cruz (EPSJV/Fiocruz), Rio de Janeiro 21040-900, Brazil
Paulo Cesar Basta: Departamento de Endemias Samuel Pessoa, Escola Nacional de Saúde Pública, Fundação Oswaldo Cruz (ENSP/Fiocruz), Rio de Janeiro 21041-210, Brazil

IJERPH, 2021, vol. 18, issue 19, 1-20

Abstract: There has been increasing evidence about mercury (Hg) contamination in traditional populations from the Amazon Basin due to illegal gold mining. The most concerning health impact is neurotoxicity caused by Hg in its organic form: methylmercury (MeHg). However, the severity and extent of the neurotoxic effects resulting from chronic environmental exposure to MeHg are still unclear. We conducted a clinical-epidemiological study to evaluate the neurological impacts of chronic MeHg exposure in Munduruku indigenous people, focusing on somatosensory, motor, and cognitive abnormalities. All participants were subjected to a systemized neurological exam protocol, including Brief Cognitive Screening Battery (BCSB), verbal fluency test, and Stick Design Test. After the examination, hair samples were collected to determine MeHg levels. Data collection took place between 29 October and 9 November 2019, in three villages ( Sawré Muybu , Poxo Muybu , and Sawré Aboy ) from Sawré Muybu Indigenous Land, Southwest of Pará state. One hundred and ten individuals >12 years old were included, 58 of which were men (52.7%), with an average age of 27.6 years (range from 12 to 72). Participants’ median MeHg level was 7.4 µg/g (average: 8.7; S.D: 4.5; range: 2.0–22.8). In Sawré Aboy village, the median MeHg level was higher (12.5 µg/g) than in the others, showing a significant statistical exposure gradient (Kruskal–Wallis test with p -value < 0.001). Cerebellar ataxia was observed in two participants with MeHg levels of 11.68 and 15.68 µg/g. Individuals with MeHg exposure level ?10 µg/g presented around two-fold higher chances of cognitive deficits (RP: 2.2; CI 95%: 1.13–4.26) in BCSB, and in the verbal fluency test (RP: 2.0; CI 95%: 1.18–3.35). Furthermore, adolescents of 12 to 19 years presented three-fold higher chances of verbal development deficits, according to the fluency test (RP: 3.2; CI 95%: 1.06–9.42), than individuals of 20 to 24 years. The worsened motor and cognitive functions are suggestive of neurotoxicity due to chronic MeHg exposure. In conclusion, we believe monitoring and follow-up measures are necessary for chronic mercury exposed vulnerable people, and a basic care protocol should be established for contaminated people in the Brazilian Unified Health System.

Keywords: mercury exposure; neurological abnormalities; indigenous people; Amazon; environmental impacts; illegal mining (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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