Genetic Polymorphism of Delta Aminolevulinic Acid Dehydratase (ALAD) Gene and Symptoms of Chronic Mercury Exposure in Munduruku Indigenous Children within the Brazilian Amazon.

Genetic polymorphisms involved in mercury toxicokinetics and toxicodynamics may be associated with severe mercury toxicity. This study aimed to investigate the impact of an ALAD polymorphism on chronic mercury exposure and the health situation of indigenous children from the Brazilian Amazon. One-hundred-and-three indigenous children (under 15 years old) were included and genotyped (rs1800435) using a TaqMan validated assay. The mean age was 6.6 ± 4.5 years old, 60% were female, 49% presented with anemia, and the mean hair mercury concentration was 7.0 ± 4.5 (1.4-23.9) µg/g, with 49% exceeding the reference limit (≥6.0 µg/g). Only two children were heterozygous ALAD, while the others were all wild type. Minor allele frequency (ALAD G) and heterozygous genotype (ALAD CG) were 1% and 2%, respectively. The two children (12 and 14 years old) with the ALAD polymorphism had mercury levels above the average as well as had neurological symptoms related to chronic mercury exposure, such as visual field alterations, memory deficit, distal neuropathy, and toe amyotrophy. Both children also reported frequent consumption of fish in the diet, at least three times a week. In conclusion, our data confirm that an ALAD polymorphism can contribute to mercury half-life time, harmful effects, and neuropsychological disorders in indigenous children with chronic mercury exposure to gold mining activity.

Low doses of methylmercury intoxication solely or associated to ethanol binge drinking induce psychiatric-like disorders in adolescent female rats.

Methylmercury (MeHg) is an environmental contaminant that provokes damage to developing brain. Simultaneously, the consumption of ethanol among adolescents has increased. Evidence concerning the effects of MeHg low doses per se or associated with ethanol during adolescence are scarce. Thus, we investigate behavioral disorders resulted from exposure to MeHg low doses and co-intoxicated with ethanol in adolescent rats. Wistar rats received chronic exposure to low doses of MeHg (40 µg/kg/day for 5 weeks) and/or ethanol binge drinking (3 g/kg/day at 3 days per week for 5 weeks). Animals were submitted to behavioral assays to assess emotionality and cognitive function. Total mercury content was evaluated in the brain and hair. Oxidative parameters were analyzed in blood samples. MeHg at low doses or associated to ethanol binge drinking produced psychiatric-like disorders and cognitive impairment. Peripherally, MeHg altered oxidative parameters when associated to ethanol. Ethanol administration reduced brain mercury deposit. We proposed that ethanol reduces the necessity of mercury tissue levels to display psychiatric-like disorders/cognitive impairment.

Unravelling motor behaviour hallmarks in intoxicated adolescents: methylmercury subtoxic-dose exposure and binge ethanol intake paradigm in rats.

Methylmercury (MeHg) is a hazardous environmental pollutant, affecting Amazon basin communities by anthropogenic activities. The exact safe level of MeHg exposure is unclear, despite the efforts of health international societies to avoid mercury (Hg) poisoning. Central nervous system is severely impacted by Hg intoxication, reflecting on motor impairment. In addition, alcohol has been associated to an overall brain damage. According to lifestyle of Amazon riverside communities, alcohol intake occurs frequently. Thus, we investigated if continuous MeHg exposure at low doses during adolescence displays motor deficits (experiment 1). In the experiment 2, we examine if the co-intoxication (i.e. MeHg plus ethanol exposure) during adolescence intensify motor damage. In the experiment 1, Wistar adolescent rats (31 days old) received chronic exposure to low dose (CELD) of MeHg (40 µg/kg/day) for 35 days. For the experiment 2, five sessions of alcohol binge drinking paradigm (3ON-4OFF; 3.0 g/kg/day) were employed associated to MeHg intoxication. Motor behaviour was evaluated by the open field, pole test, beam walking and rotarod paradigms. CELDS of MeHg display motor function damage, related to hypoactivity, bradykinesia-like behaviour, coordination deficits and motor learning impairment. Co-intoxication of MeHg plus ethanol reduced cerebellar Hg content, however also resulted in motor behavioural impairment, as well as additive effects on bradykinesia and fine motor evaluation.

Mercury speciation in hair of children in three communities of the Amazon, Brazil.

Children from riverside communities located downstream of gold mining areas may be chronically exposed to relatively high levels of MeHg through the consumption of fish of this region. The objective of this study was to evaluate and compare levels of THg and MeHg in hair of children less than 12 years in communities near mines in the municipality of Itaituba and in communities far from prospecting areas in the city of Abaetetuba. The communities of Itaituba (Barreiras and São Luiz do Tapajós) had THg mean levels of 5.64±5.55 µg·g(-1) (0.43-27.82) and 11.41±7.16 µg.g(-1) (1.08-28.17), respectively, and an average count of MeHg relative to THg of 92.20% and 90.27%, respectively. In the Maranhão community, the THg average concentrations results were 2.27±2.11 µg·g(-1) (0.13-9.54) and the average values were 93.17% for MeHg. Children of Itaituba had average levels of mercury above the limit established by the World Health Organization (10 µg·g(-1)) and the strong correlation coefficient between the communities (R=0.968 and P=0.0001) suggests the hair as an excellent biomarker of human exposure to organic mercury in riverside populations of the Tapajós, which has the intake of fish daily as main source of protein dietary.

Níveis de mercúrio em peixes do rio Trombetas no baixo Amazonas: uma área sem influência da garimpagem / Mercury levels in fish of Trombetas river in low Amazon area: an area out of the influence of gold mining

A bioacumulação de Hg em peixes de diferentes níveis tróficos e hábitos alimentares foram avaliados no rio Trombetas, afluente do rio Amazonas, em uma área sem registro de atividade garimpeira na região amazônica. Este estudo tem como objetivo gerar informação sobre as concentrações de Hg nas principais espécies de peixes consumidas nesta área, que foi incluída na metodologia usada para avaliar a exposição aos compostos de Hg através da ingestão de peixes, e as condições de saúde das populações ribeirinhas. As amostras de peixes foram obtidas e identificadas com auxílio de pescadores locais e as análises de Hg foram realizadas por espectrometria de absorção atômica com sistema de geração de vapor frio de Hg após digestão ácida. As espécies foram divididas em cinco grupos, de acordo com o hábito alimentar, e as concentrações de Hg variaram amplamente com a posição ocupada na cadeia trófica e hábito alimentar, com valores mais elevados verificado nas espécies carnívoras e piscívoras com concentrações médias de 0,218 µg/g (variação entre 0,047 e 0,875 µg/g) e 0,357 µg/g (variação entre 0,036 e 1,336 µg/g). Para elucidar a origem desses valores elevados de Hg em peixes de uma área sem impacto da garimpagem e a possibilidade de exposição das populações residentes nesta área é necessário considerar, entre outros fatores, as características de migração das diferentes espécies de peixes e alguns aspectos do ecossistema aquático, que inclui as características dos sedimentos de fundo e material particulado suspenso, água e o substrato geológico. Assim, independente da origem do Hg, natural ou antropogênica, verificada a exposição ao mercúrio das populações residentes sem influência da garimpagem ou outra fonte antrópica através da ingestão de peixes com concentrações elevadas de Hg e hábito alimentar restrito, é necessário que sejam incluídas, nos programas de vigilância à saúde, atividades de monitoramento das concentrações de Hg em materiais biológicos humanos com avaliação clínica e análises de Hg nas principais espécies de peixes consumidas pela população.