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Avaliação do risco de exposição a metilmercúrio em amostras de cabelo humano
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O metilmercúrio (MeHg) é um composto orgânico de mercúrio que se acumula facilmente na cadeia alimentar marinha e é eliminado muito lentamente pelo organismo humano. Tal representa um risco significativo para os humanos, sobretudo devido ao consumo de peixe, a principal via de exposição ao MeHg. Esta problemática é particularmente relevante em países com elevado consumo de pescado, como é o caso de Portugal (57 kg per capita por ano). Estudos anteriores revelaram níveis preocupantes de exposição ao MeHg em grupos vulneráveis, como grávidas e crianças. O cabelo humano é um bom indicador de exposição ao metilmercúrio, acumulando concentrações cerca de 250 vezes superiores às do sangue e 50 vezes mais elevadas que no Sistema Nervoso Central, tornando-o um biomarcador de excelência, devido à facilidade e não-invasividade da sua recolha. Assim, o principal objetivo deste projeto é avaliar o risco de exposição da população ao MeHg, tendo em conta a frequência e tipologia do consumo de peixe reportada em inquéritos de frequência alimentar e o nível de mercúrio determinado em amostras de cabelo. Entre os objetivos secundários estão: validar o método, estimar a exposição ao MeHg, comparar resultados analíticos com inquéritos alimentares, identificar perfis de consumo associados a maior risco, e analisar a relação entre exposição recente e continuada. A recolha de cabelo foi realizada de acordo com os protocolos da OMS, sendo as amostras analisadas por espectroscopia de absorção atómica (AAS). Os dados obtidos, com base em 154 amostras, indicaram um baixo risco de toxicidade na população estudada, sendo que apenas 4,5% se encontrava acima do limiar de toxicidade (IR>1), tendo-se igualmente verificado que os inquéritos alimentares tendem a sobrestimar a exposição. A análise segmentada de madeixas do cabelo indicou que a exposição recente nem sempre reflete a exposição do último ano, uma vez que apenas em 53% das amostras o valor mais recente não foi significativamente diferente do valor médio do ano anterior. Um aspeto importante, que pode ser útil no desenho da amostragem para a Avaliação de Risco de exposição a MeHg, é o facto de que, nesta amostra populacional, o risco de exposição individual ter sido independente do risco de exposição dos restantes membros do mesmo agregado familiar.
Methylmercury (MeHg) is an organic mercury compound that accumulates readily in the marine food chain and is eliminated very slowly by human organisms. This poses a significant risk to humans, primarily due to fish consumption, the primary route of MeHg exposure. This problem is particularly relevant in countries with high fish consumption, such as Portugal (57 kg per capita per year). Previous studies have revealed worrying levels of MeHg exposure in vulnerable groups, such as pregnant women and children. Human hair is a good indicator of methylmercury exposure, accumulating concentrations approximately 250 times higher than those in blood and 50 times higher than those in the central nervous system, making it an excellent biomarker due to its ease and noninvasiveness. Therefore, the main objective of this project is to assess the risk of population exposure to MeHg, considering the frequency and typology of fish consumption reported in food frequency surveys and the mercury level determined in hair samples. Secondary objectives include validating the method, estimating MeHg exposure, comparing analytical results with dietary surveys, identifying consumption patterns associated with increased risk, and analyzing the relationship between recent and ongoing exposure. Hair collection was performed according to WHO protocols, and samples were analyzed by atomic absorption spectroscopy (AAS). The data obtained, based on 154 samples, indicated a low risk of toxicity in the study population, with only 4.5% being above the toxicity threshold (IR>1). It was also found that dietary surveys tend to overestimate exposure. Segmented analysis of hair strands indicated that recent exposure does not always reflect exposure in the past year, as in only 53% of samples the most recent value was not significantly different from the average value of the previous year. An important aspect, which may be useful in sampling design for the Risk Assessment of MeHg exposure, is the fact that, in this population sample, the risk of individual exposure was independent of the risk of exposure of other members of the same household.
Methylmercury (MeHg) is an organic mercury compound that accumulates readily in the marine food chain and is eliminated very slowly by human organisms. This poses a significant risk to humans, primarily due to fish consumption, the primary route of MeHg exposure. This problem is particularly relevant in countries with high fish consumption, such as Portugal (57 kg per capita per year). Previous studies have revealed worrying levels of MeHg exposure in vulnerable groups, such as pregnant women and children. Human hair is a good indicator of methylmercury exposure, accumulating concentrations approximately 250 times higher than those in blood and 50 times higher than those in the central nervous system, making it an excellent biomarker due to its ease and noninvasiveness. Therefore, the main objective of this project is to assess the risk of population exposure to MeHg, considering the frequency and typology of fish consumption reported in food frequency surveys and the mercury level determined in hair samples. Secondary objectives include validating the method, estimating MeHg exposure, comparing analytical results with dietary surveys, identifying consumption patterns associated with increased risk, and analyzing the relationship between recent and ongoing exposure. Hair collection was performed according to WHO protocols, and samples were analyzed by atomic absorption spectroscopy (AAS). The data obtained, based on 154 samples, indicated a low risk of toxicity in the study population, with only 4.5% being above the toxicity threshold (IR>1). It was also found that dietary surveys tend to overestimate exposure. Segmented analysis of hair strands indicated that recent exposure does not always reflect exposure in the past year, as in only 53% of samples the most recent value was not significantly different from the average value of the previous year. An important aspect, which may be useful in sampling design for the Risk Assessment of MeHg exposure, is the fact that, in this population sample, the risk of individual exposure was independent of the risk of exposure of other members of the same household.
Descrição
Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas Moniz
Palavras-chave
Cabelo humano Espetrometria de absorção atómica Metilmercúrio Risco de exposição