Establishment and validation of analytical methods for the determination of arsenic species in foodstuffs

Resumo

[spa] El interés en la determinación de arsénico inorgánico (iAs) en los alimentos se debe al amplio reconocimiento de sus efectos tóxicos en los humanos, incluso a bajas concentraciones. Varios métodos de especiación de arsénico se han publicado, sin embargo es necesario establecer su idoneidad para una serie de muestras de alimentos y /o especies de arsénico Además, existe una necesidad urgente de métodos analíticos robustos y validados y adecuados para la determinación de arsénico inorgánico en una gama de productos alimenticios. Esta necesidad se destacó por varias agencias internacionales de seguridad y salud, y por las organizaciones encargadas de establecer los niveles máximos de la iAs en los productos alimenticios. En vista de todo esto, el objetivo principal de esta tesis es desarrollar y validar metodología analítica robusta para la determinación de arsénico inorgánico, así como otras especies de arsénico en alimentos. La metodología propuesta es aplicada a arroz, alimentos a base de cereales, productos infantiles, setas, algas, peces, crustáceos y bivalvos proporcionando resultados fiables como una respuesta a la demanda de las agencias internacionales de seguridad. Las principales conclusiones derivadas del trabajo llevado a cabo en la presente tesis doctoral se resumen a continuación: • El método de especiación propuesto fue validado con éxito de acuerdo con la norma 17025 ISO/IEC: 2005, es sensible y selectivo y podría ser considerado apropiado para su finalidad, es decir, la determinación de iAs en los alimentos. Este método es sencillo para análisis de rutina para la determinación del tóxico iAs y otras especies de arsénico en varios productos alimenticios, incluso en matrices difíciles tales como las de origen marino. Además, debido a que límites máximos de iAs en arroz y productos de arroz han sido recientemente establecidos por la Unión Europea, el método podría ser útil en los laboratorios de control de los alimentos. • La ingesta diaria promedio de iAs estimada en la población adulta Catalana está por debajo de los rangos BMDL de la EFSA y JECFA, pero teniendo en cuenta relación entre la ingesta de iAs y algunos BMDL para distintos puntos finales, la posibilidad de riesgo para los grandes consumidores de arroz y productos de arroz no pueden ser excluidos [eng] Food and drinking water are the principal routes of exposure to arsenic (As) for humans. More than 50 different naturally occurring As-containing compounds have been identified. Regarding the toxicological aspects of arsenic in food, inorganic arsenic (iAs, (arsenite or As(III) and arsenate or As(V)) is considered to be the most dangerous form and is classified as a nonthreshold, class 1 human carcinogen. The organic forms are mainly considered to be non-toxic. Therefore, species-dependent differences in toxicity must be considered when establishing the maximum tolerated levels in food directives. Recently, maximum levels have been fixed for iAs in rice and rice products in EU legislation. Scientific opinions on arsenic in food were issued by the European Food Safety Authority and the FAO/WHO Joint Expert Committee on Food Additives, focusing on dietary iAs exposure. Both reported the urgent need for further data on As species, particularly iAs data, in food groups that provide a significant contribution to the dietary exposure to iAs. As a general recommendation, dietary exposure to iAs should be reduced. Furthermore, the organisations also called upon further initiatives towards development of validated methods for specific and selective determination of inorganic arsenic in various types of foodstuffs. In view of the above, the main goal of this thesis was to develop and validate robust analytical methodology for the determination of iAs as well as other arsenic species in foodstuffs. As external quality control of the validated methods, the validated methods were tested participating in feasibility studies for the preparation of Certified Reference Materials with certified arsenic species and in proficiency tests for iAs determination The proposed methodology was applied to rice and rice products, infant cereals, cereal-based food, seaweeds, mushrooms, fish, bivalves and crustaceans, providing reliable results in response to demands made by international safety agencies. Additionally, daily dietary exposure to tAs and iAs intake to assess the toxicological implications of the ingestion of the selected foodstuffs was estimated. The main conclusions derived from the work conducted in this doctoral thesis are summarized as follows: - The proposed speciation method was successfully validated according to the ISO/IEC 17025:2005 standard, is sensitive and selective and could be considered fit for purpose, i.e. iAs determination in food. This method is straightforward enough for routine analysis for the determination of toxic iAs and other arsenic species in several foodstuffs, even in challenging matrices such as those of marine origin. Furthermore, since maximum limits of iAs in rice and rice products have recently been established by the European Union, the method could be useful in food control laboratories. - Based on our results on marine foods, wide variability in arsenic species can be expected when dealing with seafood such as seaweeds, bivalves and crustaceans, highlighting the need to carry out speciation to discern the toxic from the non-toxic species. On the other hand, only toxic iAs species were found in cereal products and iAs was the major As compound found in rice products, highlighting the importance of these food groups as a possible source of iAs in rice and cereal-based diets. - All arsenic speciation data obtained in this thesis are useful for assessing the daily intake of arsenic in the Catalan population. Furthermore, these results may contribute to on-going discussions regarding establishing and implementing maximum levels in inorganic arsenic in food commodities, as recommended within the European Union. - The average estimated iAs daily intake in the adult Catalan population is below the EFSA and JECFA BMDL ranges, but given the ratio between iAs intake and some BMDL for distinct end points, the possibility of risk for high consumers of rice and rice products cannot be excluded.