Food and Chemical Toxicology 73 (2014) 44–50
Contents lists available at ScienceDirect
Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox
Total contents of arsenic and associated health risks in edible mushrooms, mushroom supplements and growth substrates from Galicia (NW Spain) M.J. Melgar ⇑, J. Alonso, M.A. García Department of Toxicology, Faculty of Veterinary Science, University of Santiago de Compostela, 27002 Lugo, Spain
a r t i c l e
i n f o
Article history: Received 28 May 2014 Accepted 4 August 2014 Available online 14 August 2014 Keywords: Arsenic Fungi Mushroom supplements Substrates Bioconcentration factors
a b s t r a c t The levels of arsenic (As) in the main commercial species of mushrooms present in Galicia, in their growth substrates, and mushroom supplements have been analysed by ICP-MS, with the intention of assessing potential health risks involved with their consumption. The mean concentrations of As in wild and cultivated mushrooms was 0.27 mg/kg dw, in mushroom supplements 0.40 mg/kg dw, in soils 5.10 mg/kg dw, and in growth substrate 0.51 mg/kg dw. No significant differences were observed between species, although the species Lactarius deliciosus possessed a slightly more elevated mean concentration (at 0.49 mg/kg dw) than the other species investigated. In soils, statistically significant differences (p < 0.05) were observed according to geographic origin. Levels in mushroom supplements, although low, were higher than in wild or cultivated mushrooms. Measured arsenic levels were within the normal range in samples analysed in unpolluted areas. Because of the low As concentrations found in fungi and mushroom supplements from Galicia, and considering the relatively small inclusion of these foods in people’s diet, it can be concluded that there is no toxicological risk of arsenic associated with the consumption of the species of mushrooms analysed or at the dosages indicated for mushroom supplements. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Mushrooms are edible products with high protein and mineral content but low carbohydrate and fat values. Mushrooms provide relatively high concentrations of essential elements but are able to accumulate different toxic metals (e.g., Pb, Hg, Cd) and metalloids like arsenic (As), which could represent a serious risk to consumer health. Mushrooms may play an important role in As cycling in the environment, both as decomposers and plant symbioses (Smith et al., 2007). Therefore, intensive research has been carried out to detect and explain the presence and distribution of many heavy metals in edible mushrooms (Alonso et al., 2000; Cocchi et al., 2006; García et al., 2013; Gonzálvez et al., 2009; Li et al., 2011; Melgar et al., 2009; Soeroes et al., 2005; Ouzouni et al., 2009). Arsenic is a widespread metalloid in nature and one of the elements present in concentrations that raise chemical and toxicological concerns. Different chemical forms of arsenic have different ⇑ Corresponding author. Tel.: +34 982 822206; fax: +34 982 822001. E-mail address: [email protected] (M.J. Melgar). http://dx.doi.org/10.1016/j.fct.2014.08.003 0278-6915/Ó 2014 Elsevier Ltd. All rights reserved.
toxicity; thus, inorganic arsenic is generally toxic in both its arsenite [As (III)] and arsenate [As (V)] forms. However, it is non-toxic in some highly methylated forms, such as arsenobetaine and arsenocholine. In general, organic arsenic compounds are considered less toxic than inorganic arsenic. Still, they cannot be assumed as being completely benign (Sofuoglu et al., 2014); indeed, arsenic has been classified as Group 1 carcinogens (i.e., carcinogenic to humans) (ATSDR, 2007; Gonzálvez et al., 2009; HHS, 2011; Niedzielski et al., 2013; Soeroes et al., 2005). Determining the form of arsenic for mushrooms grown in unpolluted and polluted soils is an important issue for understanding the uptake, transfer, and accumulation processes in fruiting bodies. For this reason, analysis of arsenic species in selected mushroom species was performed in some earlier studies (Niedzielski et al., 2013; Smith et al., 2007).Accordingly, accurate data on As content in foods are essential both in primary research and subsequent governance and legislation that allows the assessment of health risks to be carried out. The uptake of metals and metalloids by fungi can occur because the mycelium can capture and bioaccumulate these heavy metals and other trace elements present in their growth substrates. The metals and trace elements can then accumulate in the carpophores
M.J. Melgar et al. / Food and Chemical Toxicology 73 (2014) 44–50
(mushrooms), occasionally in high concentrations. Generally, the detoxification process of arsenic (as methylate arsenic) is initiated by microorganisms. Such microorganisms live in a symbiotic relationship with the mycelium of higher fungi in the growth medium. More than 50 different naturally occurring As-containing compounds have been identified, comprising both organic and inorganic forms. Some of these have been found in mushrooms, including As (III), As (V), methylarsonic acid (MA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), tetramethylarsonium cation (TETRA), arsenobetaine and arsenocholine (LlorenteMirandes et al., 2014; Niedzielski et al., 2013; Slejkovec et al., 1997). In a recent study focusing on toxic constituents of Agaricus brasiliensis (Agaricus blazei), a variety of cultivated mushrooms, including Agaricus bisporus, have been investigated for their total arsenic concentrations (Stijve et al., 2003). The normal levels of arsenic in wild mushrooms are usually less than 1 mg/kg dw (Kalacˇ, 2009). However, there are notable exceptions; for example, measured values of As between 4 and 146 mg/ kg dw and even extreme levels of 1420 mg/kg dw in polluted areas have been reported for Laccaria amethystina. Moreover, the inedible Sarcosphaera coronaria species has been measured to possess As levels of 2130 mg/kg dw (Larsen et al., 1998; Slekovec and Irgolic, 1996; Stijve et al., 1990). Lastly, cultivated Agaricus bisporus, which is for sale in Switzerland, was reported to contain As levels between 0.05 and 1.50 lg As/g dry mass (dm) (Soeroes et al., 2005). The arsenic compounds in edible mushrooms are obviously of concern to the consumer and regulatory authorities. Currently, no limits exist in the European Union (EU) for arsenic, either total or inorganic, in foods (Commission Regulation 1881/2006). Notably, the toxic effects of this element in their inorganic forms have led the Joint Commission FAO/WHO to set a provisional tolerable weekly intake (PTWI) for inorganic arsenic of 15 lg/kg of weight corporal. It has been indicated by the CONTAM Panel that this parameter should no longer be used (EFSA, 2009). Summarising the earlier data on arsenic concentrations within higher mushrooms, it can be stated that a high arsenic concentration could be the result of so-called bioaccumulation (i.e., the preferential uptake of the element from soil with low arsenic concentration) or the result of ‘‘normal uptake’’ from a soil with a high arsenic concentration (Vetter, 2004). Because of the growing interest in the consumption of mushrooms (both wild and cultivated) and mushroom supplements, as well as the absence of studies on arsenic in mushrooms in Galicia, we have analysed the levels of As in the species of mushrooms marketed commercially in this region, in their growth substrates, in soils, and mushroom supplements to assess their toxicological implications.
45
Samples of wild mushrooms were constituted by a variable number of fruiting bodies collected ‘‘in situ’’ within zones of the 4 provinces of Galicia (i.e., La Coruña, Lugo, Pontevedra, and Orense, Fig. 1). Samples of cultivated mushrooms, compost, and mushroom supplements were obtained as a result of our collaboration with mycological companies. Soil samples were taken from the areas where sample mushrooms were collected. Each sample consists of the sum (4–8) of the material collected at various representative points of the sampling area by helical probe to a depth of 10 cm. Of the whole sample, representative portions were selected and obtained by breaking the mushroom. An equivalent of approximately 1 kg was introduced into conveniently labelled bags. All samples were subjected to the processes of drying, grinding, and digestion prior to the final analysis of mineral elements by ICP-MS. The soils were sieved through a sieve of plastic material of 2 mm in diameter in agate mortar. Drying to a constant weight took place in a drying oven set to 65 °C. Mineralization of the sample consisted of a wet digestion with a suprapur acid mixture using a variant method of EPA 3052 (EPA, 1996). Approximately 0.1 g of dry subsample was introduced into each glass Teflon (in duplicate). This amount was weighed exactly with an analytical precision balance. Subsequently, a mixture of 7 ml of suprapur nitric acid (65%) and 1 ml of suprapur hydrogen peroxide (30%) was added, which achieved the necessary minimum volume of 8 ml. The digestion process of samples was carried out in a microwave station Model ETHOS Plus 20 MilestoneÒ, with a total duration time of 24 min divided into four progressive stages, to reach the final temperature of 180 °C. The final temperature was maintained for 10 min. Following this step, solutions were prepared in Erlenmeyer flasks to 50 ml volume with milli-Q water. Finally, the solutions were transferred to polyethylene bottles and kept refrigerated until analysis by ICP-MS. In parallel, white and reference material samples were processed to verify the accuracy and precision of this method. 2.2. Analysis Samples were analysed by an ICP-MS spectrometer, Varian 820. The sensitivity of this method was determined according to the detection limits established for this spectrometer, which for arsenic was 20 ng/l (ppt). To assess the precision of the method, the coefficient of variation (CV) of the average of 15 replicates of a sample solution was determined. The calculated CV was 4.72%. The accuracy of our analytical method was determined using the certified reference material ‘‘CS-M-1: As, Cd, Cu, Hg, Pb, Se and Zn in dried mushroom powder’’, which is certified by the ‘‘Institute of Nuclear Chemistry and Technology, Warsaw, Poland.’’ The referenced value is reported as 0.344 ± 0.033 and the value obtained with our analytical method is 0.339 ± 0.047 (98.55%). 2.3. Statistical analysis Statistical data analysis was performed using the IBM SPSS Statistics software (version 22). In addition to the usual descriptive statistics involved with these studies, an analysis of univariate Variance (ANOVA) was performed to assess the influence of factors such as the type and species of fungi (wild or cultivated) and the concentration of As in the fruiting bodies. Likewise, an ANOVA analysis for arsenic concentrations in mushroom supplements and soils from different sampling areas was conducted. Previously, it was determined whether the data were adjusted to a normal distribution using the Kolmogorov–Smirnov test. Additionally, Levene’s test was performed to test the homogeneity of variances. To achieve these criteria and apply ANOVA, we transformed the data logarithmically.
3. Results and discussion 2. Materials and methods 2.1. Sampling In this study a total of 104 samples were analysed. For the mushrooms, 51 wild mushroom samples that comprise 6 of the main species (or taxonomic sections) commercialised in Galicia and 10 samples of cultivated mushrooms were analysed (Table 1). For the mushroom supplements (taken as extracts from capsules), 21 samples were analysed, which contained the following species: Agaricus blazei Murril (2); Coprinus comatus (O.F. Müll.) Pers. (1); Cordyceps spp. (6); Ganoderma lucidum (Curtis) P. Karst. (4); Grifola frondosa (Dicks.) Gray (2); Hericium erinaceus (Bull.) Pers. (1); Lentinula edodes (Berk.) Pegler (1); Polyporus umbellatus (Pers.) Fr. (1); Trametes versicolor (L.) Lloyd (1); and a mixture of various species (2). Eighteen samples of soils were analysed that correspond to the areas where the wild mushrooms were collected: 4 in La Coruña province, 6 in Lugo province, 6 in Pontevedra province, and 2 in Orense province (Fig. 1). Lastly, 4 samples of growth substrates for cultivated mushrooms were analysed, including 3 from compost (2 from the cultivation of Agaricus bisporus [(J.E. Lange) Imbach and 1 from Pleurotus ostreatus (Jacq.) P. Kumm.)] and 1 from wood (cultivation of Lentinula edodes).
Total arsenic concentrations (mg/kg dw) in different samples of fungi (wild and cultivated), mushroom supplements, substrates, and soils in Galicia are indicated in Table 1. Bioconcentration Factors (BCF), or the ratio between the levels of As in fungi and in substrates where mushrooms grow (i.e., soil for wild species and wood or compost for cultivated species) are also expressed. Mean levels of soils in each of the 4 provinces from Galicia are displayed in Table 2. The arsenic contents of mushrooms are regulated by different factors, both genetic and environmental. The role of genetic factors in As regulation can be stated based on the remarkably high arsenic contents of the mushrooms species of the same genus (Agaricus, Clitocybe, Lepista, Macrolepiota). The taxonomic position of the analysed mushrooms seems to be the most important factor (Vetter, 2004). These factors could influence the As concentrations and the bioconcentration factors.
46
M.J. Melgar et al. / Food and Chemical Toxicology 73 (2014) 44–50
Table 1 Arsenic total concentrations (mg/kg dw) analysed in different species of fungi, mushroom supplements, substrates and soils from Galicia. Number of samples (n), mean concentrations, standard deviations, range and bioconcentration factors (BCF) are indicated. Samples
n
Mean ± SD
Range
BCF
Species of wild mushrooms Boletus section Edules: (Boletus edulis Bull. and Boletus pinophilus Pilat & Dermek) Cantharellus cibarius Fr. Craterellus tubaeformis (Bulliard) Fries Hydnum repandum L. Lactarius deliciosus L. (Gray) Tricholoma portentosum (Fr.) Quel. Species of cultivated mushrooms Into wood (Lentinula edodes (Berk.) Pegler) Into compost (Agaricus bisporus (J.E. Lange) Imbach and Pleurotus ostreatus (Jacq.) P. Kumm.) Mushrooms supplements Substrates Wood cultivation Lentinula edodes Compost cultivation of Agaricus bisporus y Pleurotus ostreatus Soils
51 17 10 8 7 4 5 10 4 6 21 4 1 3 18
0.27 ± 0.24 0.33 ± 0.25 0.18 ± 0.11 0.12 ± 0.07 0.43 ± 0.26 0.49 ± 0.43 0.21 ± 0.11 0.27 ± 0.26 0.09 ± 0.06 0.39 ± 0.06 0.40 ± 0.33 0.51 ± 0.82 0.16 0.66 ± 0.93 5.10 ± 5.00
0.03–1.07 0.09–0.81 0.06–0.46 0.03–0.22 0.15–0.92 0.09–1.07 0.08–0.32 0.02–0.72 0.03–0.17 0.02–0.72 0.05–1.50 0.10–1.74
0.08 0.08 0.05 0.03 0.15 0.19 0.04 0.53 0.57 0.59
The mean concentrations of As found in wild mushrooms were 0.27 mg/kg dw; in cultivated mushrooms 0.27 mg/kg dw; in mushroom supplements 0.40 mg/kg dw; in soil 5.10 mg/kg dw; and in growth substrates 0.51 mg/kg dw. These concentrations could be considered low and were within normal levels (
Contents lists available at ScienceDirect
Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox
Total contents of arsenic and associated health risks in edible mushrooms, mushroom supplements and growth substrates from Galicia (NW Spain) M.J. Melgar ⇑, J. Alonso, M.A. García Department of Toxicology, Faculty of Veterinary Science, University of Santiago de Compostela, 27002 Lugo, Spain
a r t i c l e
i n f o
Article history: Received 28 May 2014 Accepted 4 August 2014 Available online 14 August 2014 Keywords: Arsenic Fungi Mushroom supplements Substrates Bioconcentration factors
a b s t r a c t The levels of arsenic (As) in the main commercial species of mushrooms present in Galicia, in their growth substrates, and mushroom supplements have been analysed by ICP-MS, with the intention of assessing potential health risks involved with their consumption. The mean concentrations of As in wild and cultivated mushrooms was 0.27 mg/kg dw, in mushroom supplements 0.40 mg/kg dw, in soils 5.10 mg/kg dw, and in growth substrate 0.51 mg/kg dw. No significant differences were observed between species, although the species Lactarius deliciosus possessed a slightly more elevated mean concentration (at 0.49 mg/kg dw) than the other species investigated. In soils, statistically significant differences (p < 0.05) were observed according to geographic origin. Levels in mushroom supplements, although low, were higher than in wild or cultivated mushrooms. Measured arsenic levels were within the normal range in samples analysed in unpolluted areas. Because of the low As concentrations found in fungi and mushroom supplements from Galicia, and considering the relatively small inclusion of these foods in people’s diet, it can be concluded that there is no toxicological risk of arsenic associated with the consumption of the species of mushrooms analysed or at the dosages indicated for mushroom supplements. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Mushrooms are edible products with high protein and mineral content but low carbohydrate and fat values. Mushrooms provide relatively high concentrations of essential elements but are able to accumulate different toxic metals (e.g., Pb, Hg, Cd) and metalloids like arsenic (As), which could represent a serious risk to consumer health. Mushrooms may play an important role in As cycling in the environment, both as decomposers and plant symbioses (Smith et al., 2007). Therefore, intensive research has been carried out to detect and explain the presence and distribution of many heavy metals in edible mushrooms (Alonso et al., 2000; Cocchi et al., 2006; García et al., 2013; Gonzálvez et al., 2009; Li et al., 2011; Melgar et al., 2009; Soeroes et al., 2005; Ouzouni et al., 2009). Arsenic is a widespread metalloid in nature and one of the elements present in concentrations that raise chemical and toxicological concerns. Different chemical forms of arsenic have different ⇑ Corresponding author. Tel.: +34 982 822206; fax: +34 982 822001. E-mail address: [email protected] (M.J. Melgar). http://dx.doi.org/10.1016/j.fct.2014.08.003 0278-6915/Ó 2014 Elsevier Ltd. All rights reserved.
toxicity; thus, inorganic arsenic is generally toxic in both its arsenite [As (III)] and arsenate [As (V)] forms. However, it is non-toxic in some highly methylated forms, such as arsenobetaine and arsenocholine. In general, organic arsenic compounds are considered less toxic than inorganic arsenic. Still, they cannot be assumed as being completely benign (Sofuoglu et al., 2014); indeed, arsenic has been classified as Group 1 carcinogens (i.e., carcinogenic to humans) (ATSDR, 2007; Gonzálvez et al., 2009; HHS, 2011; Niedzielski et al., 2013; Soeroes et al., 2005). Determining the form of arsenic for mushrooms grown in unpolluted and polluted soils is an important issue for understanding the uptake, transfer, and accumulation processes in fruiting bodies. For this reason, analysis of arsenic species in selected mushroom species was performed in some earlier studies (Niedzielski et al., 2013; Smith et al., 2007).Accordingly, accurate data on As content in foods are essential both in primary research and subsequent governance and legislation that allows the assessment of health risks to be carried out. The uptake of metals and metalloids by fungi can occur because the mycelium can capture and bioaccumulate these heavy metals and other trace elements present in their growth substrates. The metals and trace elements can then accumulate in the carpophores
M.J. Melgar et al. / Food and Chemical Toxicology 73 (2014) 44–50
(mushrooms), occasionally in high concentrations. Generally, the detoxification process of arsenic (as methylate arsenic) is initiated by microorganisms. Such microorganisms live in a symbiotic relationship with the mycelium of higher fungi in the growth medium. More than 50 different naturally occurring As-containing compounds have been identified, comprising both organic and inorganic forms. Some of these have been found in mushrooms, including As (III), As (V), methylarsonic acid (MA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), tetramethylarsonium cation (TETRA), arsenobetaine and arsenocholine (LlorenteMirandes et al., 2014; Niedzielski et al., 2013; Slejkovec et al., 1997). In a recent study focusing on toxic constituents of Agaricus brasiliensis (Agaricus blazei), a variety of cultivated mushrooms, including Agaricus bisporus, have been investigated for their total arsenic concentrations (Stijve et al., 2003). The normal levels of arsenic in wild mushrooms are usually less than 1 mg/kg dw (Kalacˇ, 2009). However, there are notable exceptions; for example, measured values of As between 4 and 146 mg/ kg dw and even extreme levels of 1420 mg/kg dw in polluted areas have been reported for Laccaria amethystina. Moreover, the inedible Sarcosphaera coronaria species has been measured to possess As levels of 2130 mg/kg dw (Larsen et al., 1998; Slekovec and Irgolic, 1996; Stijve et al., 1990). Lastly, cultivated Agaricus bisporus, which is for sale in Switzerland, was reported to contain As levels between 0.05 and 1.50 lg As/g dry mass (dm) (Soeroes et al., 2005). The arsenic compounds in edible mushrooms are obviously of concern to the consumer and regulatory authorities. Currently, no limits exist in the European Union (EU) for arsenic, either total or inorganic, in foods (Commission Regulation 1881/2006). Notably, the toxic effects of this element in their inorganic forms have led the Joint Commission FAO/WHO to set a provisional tolerable weekly intake (PTWI) for inorganic arsenic of 15 lg/kg of weight corporal. It has been indicated by the CONTAM Panel that this parameter should no longer be used (EFSA, 2009). Summarising the earlier data on arsenic concentrations within higher mushrooms, it can be stated that a high arsenic concentration could be the result of so-called bioaccumulation (i.e., the preferential uptake of the element from soil with low arsenic concentration) or the result of ‘‘normal uptake’’ from a soil with a high arsenic concentration (Vetter, 2004). Because of the growing interest in the consumption of mushrooms (both wild and cultivated) and mushroom supplements, as well as the absence of studies on arsenic in mushrooms in Galicia, we have analysed the levels of As in the species of mushrooms marketed commercially in this region, in their growth substrates, in soils, and mushroom supplements to assess their toxicological implications.
45
Samples of wild mushrooms were constituted by a variable number of fruiting bodies collected ‘‘in situ’’ within zones of the 4 provinces of Galicia (i.e., La Coruña, Lugo, Pontevedra, and Orense, Fig. 1). Samples of cultivated mushrooms, compost, and mushroom supplements were obtained as a result of our collaboration with mycological companies. Soil samples were taken from the areas where sample mushrooms were collected. Each sample consists of the sum (4–8) of the material collected at various representative points of the sampling area by helical probe to a depth of 10 cm. Of the whole sample, representative portions were selected and obtained by breaking the mushroom. An equivalent of approximately 1 kg was introduced into conveniently labelled bags. All samples were subjected to the processes of drying, grinding, and digestion prior to the final analysis of mineral elements by ICP-MS. The soils were sieved through a sieve of plastic material of 2 mm in diameter in agate mortar. Drying to a constant weight took place in a drying oven set to 65 °C. Mineralization of the sample consisted of a wet digestion with a suprapur acid mixture using a variant method of EPA 3052 (EPA, 1996). Approximately 0.1 g of dry subsample was introduced into each glass Teflon (in duplicate). This amount was weighed exactly with an analytical precision balance. Subsequently, a mixture of 7 ml of suprapur nitric acid (65%) and 1 ml of suprapur hydrogen peroxide (30%) was added, which achieved the necessary minimum volume of 8 ml. The digestion process of samples was carried out in a microwave station Model ETHOS Plus 20 MilestoneÒ, with a total duration time of 24 min divided into four progressive stages, to reach the final temperature of 180 °C. The final temperature was maintained for 10 min. Following this step, solutions were prepared in Erlenmeyer flasks to 50 ml volume with milli-Q water. Finally, the solutions were transferred to polyethylene bottles and kept refrigerated until analysis by ICP-MS. In parallel, white and reference material samples were processed to verify the accuracy and precision of this method. 2.2. Analysis Samples were analysed by an ICP-MS spectrometer, Varian 820. The sensitivity of this method was determined according to the detection limits established for this spectrometer, which for arsenic was 20 ng/l (ppt). To assess the precision of the method, the coefficient of variation (CV) of the average of 15 replicates of a sample solution was determined. The calculated CV was 4.72%. The accuracy of our analytical method was determined using the certified reference material ‘‘CS-M-1: As, Cd, Cu, Hg, Pb, Se and Zn in dried mushroom powder’’, which is certified by the ‘‘Institute of Nuclear Chemistry and Technology, Warsaw, Poland.’’ The referenced value is reported as 0.344 ± 0.033 and the value obtained with our analytical method is 0.339 ± 0.047 (98.55%). 2.3. Statistical analysis Statistical data analysis was performed using the IBM SPSS Statistics software (version 22). In addition to the usual descriptive statistics involved with these studies, an analysis of univariate Variance (ANOVA) was performed to assess the influence of factors such as the type and species of fungi (wild or cultivated) and the concentration of As in the fruiting bodies. Likewise, an ANOVA analysis for arsenic concentrations in mushroom supplements and soils from different sampling areas was conducted. Previously, it was determined whether the data were adjusted to a normal distribution using the Kolmogorov–Smirnov test. Additionally, Levene’s test was performed to test the homogeneity of variances. To achieve these criteria and apply ANOVA, we transformed the data logarithmically.
3. Results and discussion 2. Materials and methods 2.1. Sampling In this study a total of 104 samples were analysed. For the mushrooms, 51 wild mushroom samples that comprise 6 of the main species (or taxonomic sections) commercialised in Galicia and 10 samples of cultivated mushrooms were analysed (Table 1). For the mushroom supplements (taken as extracts from capsules), 21 samples were analysed, which contained the following species: Agaricus blazei Murril (2); Coprinus comatus (O.F. Müll.) Pers. (1); Cordyceps spp. (6); Ganoderma lucidum (Curtis) P. Karst. (4); Grifola frondosa (Dicks.) Gray (2); Hericium erinaceus (Bull.) Pers. (1); Lentinula edodes (Berk.) Pegler (1); Polyporus umbellatus (Pers.) Fr. (1); Trametes versicolor (L.) Lloyd (1); and a mixture of various species (2). Eighteen samples of soils were analysed that correspond to the areas where the wild mushrooms were collected: 4 in La Coruña province, 6 in Lugo province, 6 in Pontevedra province, and 2 in Orense province (Fig. 1). Lastly, 4 samples of growth substrates for cultivated mushrooms were analysed, including 3 from compost (2 from the cultivation of Agaricus bisporus [(J.E. Lange) Imbach and 1 from Pleurotus ostreatus (Jacq.) P. Kumm.)] and 1 from wood (cultivation of Lentinula edodes).
Total arsenic concentrations (mg/kg dw) in different samples of fungi (wild and cultivated), mushroom supplements, substrates, and soils in Galicia are indicated in Table 1. Bioconcentration Factors (BCF), or the ratio between the levels of As in fungi and in substrates where mushrooms grow (i.e., soil for wild species and wood or compost for cultivated species) are also expressed. Mean levels of soils in each of the 4 provinces from Galicia are displayed in Table 2. The arsenic contents of mushrooms are regulated by different factors, both genetic and environmental. The role of genetic factors in As regulation can be stated based on the remarkably high arsenic contents of the mushrooms species of the same genus (Agaricus, Clitocybe, Lepista, Macrolepiota). The taxonomic position of the analysed mushrooms seems to be the most important factor (Vetter, 2004). These factors could influence the As concentrations and the bioconcentration factors.
46
M.J. Melgar et al. / Food and Chemical Toxicology 73 (2014) 44–50
Table 1 Arsenic total concentrations (mg/kg dw) analysed in different species of fungi, mushroom supplements, substrates and soils from Galicia. Number of samples (n), mean concentrations, standard deviations, range and bioconcentration factors (BCF) are indicated. Samples
n
Mean ± SD
Range
BCF
Species of wild mushrooms Boletus section Edules: (Boletus edulis Bull. and Boletus pinophilus Pilat & Dermek) Cantharellus cibarius Fr. Craterellus tubaeformis (Bulliard) Fries Hydnum repandum L. Lactarius deliciosus L. (Gray) Tricholoma portentosum (Fr.) Quel. Species of cultivated mushrooms Into wood (Lentinula edodes (Berk.) Pegler) Into compost (Agaricus bisporus (J.E. Lange) Imbach and Pleurotus ostreatus (Jacq.) P. Kumm.) Mushrooms supplements Substrates Wood cultivation Lentinula edodes Compost cultivation of Agaricus bisporus y Pleurotus ostreatus Soils
51 17 10 8 7 4 5 10 4 6 21 4 1 3 18
0.27 ± 0.24 0.33 ± 0.25 0.18 ± 0.11 0.12 ± 0.07 0.43 ± 0.26 0.49 ± 0.43 0.21 ± 0.11 0.27 ± 0.26 0.09 ± 0.06 0.39 ± 0.06 0.40 ± 0.33 0.51 ± 0.82 0.16 0.66 ± 0.93 5.10 ± 5.00
0.03–1.07 0.09–0.81 0.06–0.46 0.03–0.22 0.15–0.92 0.09–1.07 0.08–0.32 0.02–0.72 0.03–0.17 0.02–0.72 0.05–1.50 0.10–1.74
0.08 0.08 0.05 0.03 0.15 0.19 0.04 0.53 0.57 0.59
The mean concentrations of As found in wild mushrooms were 0.27 mg/kg dw; in cultivated mushrooms 0.27 mg/kg dw; in mushroom supplements 0.40 mg/kg dw; in soil 5.10 mg/kg dw; and in growth substrates 0.51 mg/kg dw. These concentrations could be considered low and were within normal levels (
