ABSTRACT
Mercury is emitted to the atmosphere from various natural and anthropogenic sources, and degrades with difficulty in the environment. Mercury exists as various species, mainly elemental (Hg0) and divalent (Hg2+) mercury depending on its oxidation states in air and water. Mercury emitted to the atmosphere can be deposited into aqueous environments by wet and dry depositions, and some can be re-emitted into the atmosphere. The deposited mercury species, mainly Hg2+, can react with various organic compounds in water and sediment by biotic reactions mediated by sulfur-reducing bacteria, and abiotic reactions mediated by sunlight photolysis, resulting in conversion into organic mercury such as methylmercury (MeHg). MeHg can be bioaccumulated through the food web in the ecosystem, finally exposing humans who consume fish. For a better understanding of how humans are exposed to mercury in the environment, this review paper summarizes the mechanisms of emission, fate and transport, speciation chemistry, bioaccumulation, levels of contamination in environmental media, and finally exposure assessment of humans.
Subject(s)
Humans , Air Pollutants/chemistry , Environmental Exposure , Environmental Restoration and Remediation , Food Chain , Mercury/chemistry , Methylmercury Compounds/chemistry , Photolysis , Sulfur-Reducing Bacteria/metabolism , Water Pollutants, Chemical/metabolismABSTRACT
Methylmercury is a hazardous substance that is of interest with regard to environmental health, as inorganic mercury circulating in the general environment is dissolved into freshwater and seawater, condensed through the food chain, ingested by humans, and consequently affects human health. Recently, there has been much interest and discussion regarding the toxicity of methylmercury, the correlation with fish and shellfish intake, and methods of long-term management of the human health effects of methylmercury. What effects chronic exposure to a low concentration of methylmercury has on human health remains controversial. Although the possibility of methylmercury poisoning the heart and blood vessel system, the reproductive system, and the immune system is continuously raised and discussed, and the carcinogenicity of methylmercury is also under discussion, a clear conclusion regarding the human health effects according to exposure level has not yet been drawn. The Joint FAO/WHO Expert Committee on Food Additives proposed to prepare additional fish and shellfish intake recommendations for consumers based on the quantified evaluation of the hazardousness of methylmercury contained in fish and shellfish, methylmercury management in the Korea has not yet caught up with this international trend. Currently, the methylmercury exposure level of Koreans is known to be very high. The starting point of methylmercury exposure management is inorganic mercury in the general environment, but food intake through methylation is the main exposure source. Along with efforts to reduce mercury in the general environment, food intake management should be undertaken to reduce the human exposure to methylmercury in Korea.
Subject(s)
Animals , Humans , Environmental Exposure , Fishes/metabolism , Food Chain , Mercury Poisoning, Nervous System/etiology , Methylmercury Compounds/chemistry , Neurons/drug effects , Oxidative Stress/drug effects , Public Health , Reproduction/drug effects , Thymocytes/cytologyABSTRACT
A população ribeirinha na região do Pantanal, Brasil, é dependente do peixe, como principal fonte de alimentos e proteínas. Naquela região, o resultado de décadas de mineração de ouro, em pequena escala, foi a contaminação de muitos sistemas aquáticos com mercúrio. Conseqüentemente, muitas espécies de peixes possuem níveis de MeHg relativamente altos. O objetivo deste trabalho foi avaliar o nível de exposição ao MeHg entre a população ribeirinha do Pantanal. No primeiro artigo, apresentam-se os resultados de validação do método recordatório de 24 horas auto-referido, utilizando-se como padrão ouro, o método da pesagem, tendo-se verificado que há aproximadamente um erro de 30 por cento ao estimar a quantidade de peixe consumido por aquela população. Um erro de 30 por cento na estimativa do consumo de peixe pode nao ter muita influencia na avaliaçao da ingestão de mercúrio, se se considerarem os peixes das espécies herbívoras. Porém, este erro pode ser importante em se tratando do consumo de peixes carnívoros, os quais apresentam altos teores de mercúrio. No segundo artigo, ao analisar a associação entre o status neurocognitivo e a concentração de mercúrio no cabelo da população acima, os resultados indicaram que adultos expostos ao metil-mercúrio, através do consumo de peixe, podem ter déficits importantes nas medidas do desempenho neurocomportamental, sem alterações detectáveis no humor ou afetividade. Os efeitos mais importantes do mercúrio, entre os indivíduos analisados, foram detectados nos testes de velocidade e destreza da coordenação motora fina, na inibição da resposta na busca visual, e em tarefas de atenção. Estes resultados são consistentes com outros estudos, que sugeriram que o mercúrio causa alterações no cerebelo. A possibilidade de efeitos adversos, em adultos expostos a níveis mais baixos de mercúrio, foi também levantada por outros estudos no Brasil, que abordaram o consumo de peixe pelas populações ribeirinhas. No terceiro artigo ... calculou-se a dose marcadora (BMD) e o limite inferior do intervalo de confiança do BMD (BMDL)...