Original Research ArticleStudy of mercury content in wild edible mushrooms and its contribution to the Provisional Tolerable Weekly Intake in Spain
Introduction
Spain possesses a great diversity in mushrooms and truffles with more than 2500 species (Moreno et al., 1996, Gómez et al., 1993). Picking wild edible mushrooms is an important activity in Spain, and it involves large numbers of consumers. Mushroom consumption has grown1 noticeably in Spain over the past few years, probably as a direct result of, among other factors, recent studies about the health benefits associated with certain compounds found in mushrooms. For instance, Boletus edulis contains a powerful antioxidant compound, ergothioneine, which can be found at high concentrations, reaching levels of 528 mg/kg WW (Ey et al., 2007). Moreover, it has been reported that eating certain mushroom species can have potentially beneficial effects in the reduction of cardiovascular diseases (Guillamón et al., 2010).
It is well known that mushrooms are able to assimilate and accumulate compounds and nutrients from the environment (Alonso et al., 2004). Mushrooms can accumulate metals in the fungi epithelium, which can persist and even increase in some parts of the fruitful body, in some cases reaching higher concentrations than in the environment where they grow (Campos et al., 2009). There are many factors that can influence the presence of metals in mushrooms, such as climate, geographic location, environmental conditions, and concentration of macromolecules in the cellular wall of each specific species. In the case of total mercury (Hg), several studies have highlighted the importance of mushrooms as significant sources of this metal. According to the review by Kalač and Svoboda (2000), total mercury content of the examined wild mushrooms was between 0 and 20 mg/kg. Similarly, high levels of total mercury have been found in Boletus spp. and Agaricus spp. with concentration ranges of 2–5 and 10–20 mg/kg, respectively (Kalač, 2010). Moreover, Hg concentration in wild mushrooms could be higher as suggested by the study by Falandysz and Szajek (1994), in which average Hg concentration in wild growing Agaricus spp. was significantly higher than the concentration found in cultivated A. bisporus. These data demonstrate that the toxicological risk associated with Hg content might be higher in wild edible mushrooms. In addition, mushroom picker populations are usually associated with high consumption levels of wild mushrooms during the picking season.
Exposure to mercury has been identified as a serious threat to the development of the child in utero and early in life in addition to producing toxic effects in the nervous, digestive and immune systems, and in the lungs, kidneys, skin and eyes (Tchounwou et al., 2003). Hence the World Health Organization (WHO, 2010) has considered this heavy metal as one of the top ten elements of major public health concern.
To date, no previous studies have been carried out in the southern Spain on the Hg content of the most consumed wild edible mushroom species in this region, which has one of the biggest mushroom-picker populations in Spain, with a wide consumption of wild edible mushrooms. There is therefore a need to determine the Hg levels in the most-consumed wild edible mushrooms in southern Spain in order to assess the exposure level to this metal in picker populations. Accordingly, the aim of this study was to determine the Hg content in 10 different species of wild edible mushroom collected in the southern Spain and to assess the exposure level of mushroom picker populations by using the well-recognized safety criterion Provisional Tolerable Weekly Intake (PTWI) for Hg.
Section snippets
Methods of sampling
Mushroom samples of 10 edible wild species were picked from different areas of southern Spain during the typical collection season for mushrooms (autumn–winter) in 2011 resulting in n = 602 samples. Only fruit bodies showing full development, with cap and stem, were collected. Old and injured fruit bodies were not used. Caps and stems were sampled separately to enable Hg determination for each anatomic part separately. Each sample consisted of one anatomic part, either the cap or stem from one or
Hg content in Spanish wild mushrooms
Based on the absorbance and the calibration equations, Hg concentration was calculated in different mushroom species, expressed in mg/kg DW. In Table 2, concentration levels are shown for different anatomic parts in the different analyzed samples. Overall, the minimum and maximum concentration levels were 0.09 ± 0.08 and 10.28 ± 2.92 mg/kg DW, which corresponded to Terfezia arenaria and caps of Boletus aereus, respectively. Note that T. arenaria was the only truffle analyzed in this study, hence no
Conclusions
The results of this study show the relatively high Hg content in wild edible mushrooms in southern Spain even though wide variations were found between species. In addition, our results, based on applying PTWI for Hg, indicated that mushroom picker populations, in which elevated consumption levels can be given (≥100 g/week), could be exposed to relatively high Hg levels during mushroom picking season. Thus an exhaustive quantitative risk assessment study should be carried out that would include
Acknowledgements
This work was funded by EGMASA and Consejería de Medio Ambiente (Junta de Andalucía) through the approved contract NET325686/1.
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