Exposure Assessment of Portuguese Population to Ochratoxin a: Contaminated Foods and Urine Levels

Abstract

Ochratoxin A (OTA) is a secondary metabolite mainly produced by fungi from Aspergillus and Penicillium genera. Several toxic effects have been ascribed following exposure, namely nephrotoxicity, hepatotoxicity, teratogenicity and immunotoxicity. In addition, OTA has been classified as possible human carcinogenic - group 2B according to the classification of the International Agency for Research on Cancer (IARC). In fact OTA remains in the list of Balkan endemic nephropathy (BEN) differential diagnosis and it was already established as the cause of porcine endemic nephropathy (PEN) in Denmark. Consequently, a considerable effort has been and is being expended to characterize human and animal exposure to this mycotoxin. Once formed OTA can enter the food chain, through contamination of ingredients or foodstuffs consumed by humans or the feed chain, through contamination of feeds for animals destined for human consumption. Humans are therefore directly and indirectly exposed to this mycotoxin. OTA has been extensively reported as a worldwide contaminant of a wide variety of raw and processed stored commodities, including cereals and their derivatives, wine, coffee, beer, cocoa, dried fruits, meat and spices. However, nearly all studies point to a higher contribution of cereals and their derivatives to exposure, and a comparatively limited importance of meat and other animal-derived products. To assess the exposure of the Portuguese population to OTA a study over a two year period, encompassing four collection periods (winter of 2007/2008, summer of 2008, winter of 2008/2009 and summer of 2009) was conducted. It involved analysis of morning urine samples from inhabitants of four Portuguese mainland regions (Porto, Coimbra, Lisboa and Alentejo), simultaneously with a survey of regionally commercialised bread and pork samples. These two analysed foodstuffs are two staple foods in the Portuguese diet, with a high and transversal consumption to the majority of the population. OTA content the total 738 bread and 472 urine samples was evaluated through previously validated methods, involving clean-up with immunoaffinity columns (IAC) XI and high performance liquid chromatography coupled to fluorescence detection (HPLC/FD). The 254 pork samples were analysed through a developed method entailing IAC clean-up and liquid chromatographic coupled to tandem mass spectrometry (LC/MS/MS). The daily intake of OTA by the Portuguese population through both bread and pork consumption was also estimated. With this study it was possible to draw several conclusions. First the bread samples analysed in all the studied regions presented a widespread low level contamination, although the contamination range was broad, up to European Union (EU)-surpassing levels. Maize bread (broa), first and foremost Avintes broa, was the most contaminated, followed by whole grain-, rye- and wheat-based bread. However, because more consumed, the later contributes more to OTA exposure of the Portuguese consumers. The analysis of pork revealed a relatively high average level of contamination, along with a low frequency of contamination, in contrast with previous national and foreign surveys. The observed high within-subject variability of OTA in urine limits the use of this exposure biomarker at the individual level, but not at a population or subgroup of subjects scale. Among the studied population a widespread exposure was confirmed by the high frequency of contamination of OTA in the urine surveyed, although characterised by a low average contamination level. The urine survey revealed that the population from Alentejo was the most exposed one, and comparing the two studied staple foods, pork emerged as the major contributor. Indeed bread commercialised in this region featured the lowest contamination, as the typical Alentejano wheat bread constituted most of analysed bread samples in such region. As quite the opposite, in general, pork samples from Alentejo featured a higher contamination, probably explained by the traditional extensive feeding-system of the native swine breed, to which some of the surveyed animals belonged. In all the studied regions’ populations’ the contribution of pork to the OTA intake was higher than that of bread, which was clearly in contrast with previous studies, according to which cereals and their derived products were the major contributors, while food of animal origin makes only a small contribution to the total human dietary exposure to OTA. These differing features of the exposure of the Portuguese population XII in comparison to previous studies reinforce the need of a regular testing to monitor the situation and protect human health. The rare occurrence of limit-surpassing food samples indicated that in general the exposure to OTA is unlikely to pose a threat to the health of an average Portuguese consumer, although a continuous intake at low levels can still carry risks.