Environmental Pollution 204 (2015) 298e305

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Environmental Pollution

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Wild growing for the Edible City? Cadmium and lead content in edible mushrooms harvested within the urban agglomeration of Berlin, Germany

* Martin Thomas Schlecht, Ina Saumel€

Department of Ecology, Technische Universitat€ Berlin, Ernst Reuter Platz 1 (BH 9-1), D-10587 Berlin, Germany article info abstract

Article history: Health effects by consuming urban garden products are discussed controversially due to high urban Received 27 January 2015 pollution loads. We sampled wild edible mushrooms of different habitats and commercial Received in revised form cultivars exposed to high traffic areas within Berlin, Germany. We determined the content of cadmium 8 May 2015 and lead in the fruiting bodies and analysed how the local setting shaped the concentration patterns. EU Accepted 9 May 2015 standards for cultivated mushrooms were exceeded by 86% of the wild mushroom samples for lead and Available online by 54% for cadmium but not by mushroom cultures. We revealed significant differences in trace metal content depending on species, trophic status, habitat and local traffic burden. Higher overall traffic Keywords: burden increased trace metal content in the biomass of wild mushrooms, whereas cultivated mushrooms fi fi Human health exposed to inner city high traf c areas had signi cantly lower trace metal contents. Based on these we Macroscopic fungi discuss the consequences for the consumption of mushrooms originating from urban areas. Trace metal concentration © 2015 Elsevier Ltd. All rights reserved. Traffic parameters

1. Introduction In general, mushrooms are seen as healthy food sources being low in calories and with nutritional contents comparable to most Accelerated urbanisation and related environmental degrada- legumes and meats (Kalac, 2009). Mushrooms become increasingly tion reduce arable land availability worldwide, especially nearby attractive as functional foods for nutritional and medicinal effects cities (Chen, 2007; FAOSTAT, 2014). Fertile soils and regional food (Barros et al., 2008; Roupas et al., 2012; Reis et al., 2012; Wang et al., production get lost and food miles increase (Satterthwaite et al., 2014). The food industry is especially interested to develop a new 2010). Consequently, future food production as an integrated ur- generation of foods based on both cultivated and wild growing ban activity is postulated to enhance urban resilience (Barthel and edible mushrooms (Barros et al., 2008). The production of mush- Isendahl, 2013). The vision of the 'Edible City' promises a strategic rooms increased by 90% within the last decade (FAOSTAT, 2014). step towards the development of sustainable and productive urban However, mushrooms are also known to accumulate trace metals landscapes that will considerably reduce the ecological footprint of (Kalac and Svoboda, 2000; Kalac, 2010; Falandysz and Borovicka, cities (Bohn and Vilijoen, 2011). 2013). Trace metal concentrations in mushrooms are significantly Beyond urban agriculture and horticulture, the collection of higher than those in agricultural crop plants, vegetables, fruits or wild growing edibles can contribute to local food security (e.g. even animal tissue (Mleczek et al., 2013). Especially, cadmium, lead, Toledo and Burlingame, 2006; Uprety et al., 2012). Wild edible and silver, mercury and arsenic are considered as hazardous metals or medicinal mushrooms have been acknowledged for subsistence metalloids in mushrooms (Falandysz and Borovicka, 2013). Various uses (Boa, 2004). The consumption of wild edible mushrooms is studies from rural sites highlighted negative health effects from the high, notably in East Asia and Europe (Mleczek et al., 2013). ingestion of mushrooms (e.g. Kalac and Svoboda, 2000; Cocchi Furthermore, about 35 mushroom species have been cultivated et al., 2006; Svoboda et al., 2006; Falandysz and Borovicka, 2013). commercially, 10-20 species of those on an industrial scale The health effects from the consumption of food products (Sanchez, 2004; Aida et al., 2009). grown in cities are questioned due to high urban pollution (Alloway, 2004; Hough et al., 2004; Leake et al., 2009) and resulting levels of pollutants in urban vegetables (e.g. Saumel€ et al., 2012). * Corresponding author. Similar health risks might be also associated with the consumption E-mail address: [email protected] (I. Saumel).€ http://dx.doi.org/10.1016/j.envpol.2015.05.018 0269-7491/© 2015 Elsevier Ltd. All rights reserved. M.T. Schlecht, I. Saumel€ / Environmental Pollution 204 (2015) 298e305 299 of urban edible mushrooms, but studies from urban areas are scarce inductively coupled plasma mass spectrometry (ICP-MS; for details compared to studies at rural sites (but see Kuusi et al., 1981; see ENISO17294e2:2004). Certified reference material (SRM 3128 Svoboda and Kalac, 2003; Falandysz and Bielawski, 2007; Ji et al., (Pb) and SRM 3108 (Cd); ICP Multielement Standard VIII, Merck 2009). Effects of urbanisation on fungal communities are mostly KGaA, Germany) was used to assess quality of the measurements unknown (Newbound et al., 2010). (see UBA, 2011). The recovery rate ranged from 95 to 100% for both In this study, we harvested 184 samples of 18 different wild elements. The applied methods have been previously used in growing edible mushroom species within different urban habitats determination of metals in mushroom (e.g. Yin et al., 2012). in Berlin, Germany. Additionally, we exposed commercial mush- We used analysis of variance (ANOVA) for data analysis. Cd or Pb room cultures to high traffic areas within the inner city of Berlin. content in the dried biomass were the response variables and We determined the content of Pb and Cd in fruiting bodies species, genera, trophic status, and the parameters characterising depending on species (i.e. genus, trophic status) and sampling site local settings at sampling site (urban habitat type, overall traffic characteristics (i.e. habitat type, local traffic burden, presence or burden, distance to the nearest road and number of vehicles of the absence of barriers between sampling site and roads) to assess the nearest road, presence and absence of a barrier) were taken as health impact for consumers and to discuss consequences for the explanatory variables. Homogeneity of data (BrowneForsythe's integration of edible mushrooms into 'Edible City' approaches. test) and normal distribution of data (ShapiroeWilk test) were tested before applying the ANOVA. Log transformations were 2. Material and methods applied to comply with the assumptions of the residual normality and variance homogeneity needed for the analysis. We used the We collected in total 518 wild common edible mushrooms in the Bonferoni test for the comparison of means. Effects were consid- typical harvest period from May to November 2013 within the city ered significant at p < 0.05 level. The statistical analysis was done of Berlin, Germany. The sampling sites represented different urban by using R version 2.15.2 (R Foundation for Statistical Computing, habitats (i.e. cemeteries, parks, gardens, forests or along roads; Vienna, Austria). habitat classification according to Berlin Department for Urban Development, 2009; see Fig. 1) and were characterized by the 3. Results following parameters: distance to nearest road (d) in meters, traffic burden on the nearest road (tb) according to the number of vehicles Pb and Cd content in the wild edible mushrooms differed per day (1 5000; 2 ¼ 5001e10,000; 3 ¼ 10,001e15.000; significantly among species and genera. Few samples had concen- 4 ¼ 15,001e20000; 5 ¼ 20,001e30000; 6 ¼ 30,001e40000; trations below the detection limit (see Table 2). Comparing the 7 40,001; Berlin Department for Urban Development, 2009), trace metal content within a genus, high differences were detected presence or absence of barrier between sampling sites and nearest for Boletus and Macrolepiota species (i.e. B. luridus and B. reticulatus roads (b). Furthermore, we classified the overall traffic burden (otb) differed on average Cd content but not on Pd content, B. boletus had within a radius of 250 m around the planting sites (for details see low Pb and Cd contents and M. mastoidea had significantly lower Pb von Hoffen and Saumel,€ 2014). contents than M. procera, while Cd contents were similar; Fig. 2). In Stratified per habitat type and species we analysed Pb and Cd contrast, no differences were detected for and Agaricus ssp. content in randomly chosen subsamples of the wild edible mush- (Fig. 2). Certain species tended to gather less Pb, but accumulated rooms (n ¼ 184). The subsample consisted of a total of 18 different high amounts of Cd (X. chyrsenteron), and others showed relatively species of 11 genera (Table 1). We sampled four species of Agaricus low levels of both the tested elements (i.e. S. crispa, B. luridus, (Agaricus arvensis, Agaricus bitorquis, Agaricus Table 2). suberonatus), three of Boletus (Boletus luridus, Boletus recticulatus, Eighty two percent of all wild mushroom samples exceeded Boletus badius), two of Macrolepiota (Macroleptiota mastoidea, EU standard of 0.3 mg/kg wet weight for Pb and two third of our Macroleptiota procera), two of Russula (Russula exalbicans, Russula samples exceeded EU standard of 0.2 mg/kg wet weight for Cd vesca) and each one species of Xerocomus (Xerocomus chrysenteron), for cultivated mushrooms (EC, 2006). A third of all samples Armillaria (Armillaria solidipes), Coprinus (Coprinus comatus), Cal- exceeded these limits for both elements, only six percent did not vatia (Calvatia gigantea), Leccinum (Leccinum scabrum), Sparassis exceed the limits for both elements. For eleven out of eighteen (Sparassis crispa) and Tuber spp. species over 90 percent of the samples analysed in this study In order to explore potential health risks of commercial mush- exceeded the EU standards for Pb in cultivated mushrooms, rooms cultivars cultivated in urban areas, we exposed 16 cultivars whereas in all species at least one sample did not exceed the of Agaricus bisporus to high traffic areas within the inner city of limits for Cd. A third of our samples were characterized by Cd Berlin, Germany. A. bisporus is the most cultivated mushroom contents higher than the EU limits set for mushroom species worldwide (Aida et al., 2009) and can be cultivated in a simple and other than typically cultivated species such as Agaricus bisporus, cheap way (Reis et al., 2012). Mature fruiting bodies of A. bisporus Pleurotus ostreatus and Lentinus edodes (EC, 2008). In contrast to were harvested after the common growing period of 15 days. wild growing mushrooms, samples from sixteen commercial Directly after the harvest, the mushrooms were identified using A. bisporus cultures had significantly lower trace metal content in mushroom guides books (Breitenbach and Kranzlin, 1984, 1986, the fruiting bodies (FCd ¼ 4.8, pCd<0.001; FPb ¼ 20.5, pPb<0.001); 1991; Moser, 1983; Pegler, 1990; Winkler, 1996; Gminder, 2008) no sample exceeded the EU standard for Pb and Cd (EC, 2006, and when necessary, with additional expertise from the German Table 2). Mycological Society. The mushrooms were carefully cleaned of all Pb content of wild growing urban mushrooms was in average surface contamination by a stainless steel knife as usual for seven times higher than the respective EU standard (Table 2). mushrooms prior to prepare dishes and afterwards frozen. The A. bitorquis, A. subperonatus, A. campestris, A. arvensis, M. procera, fruiting bodies of the mushrooms were oven dried at a temperature R. exalbicans, Russula versca, and C. gigantea all accumulated higher of 65 C for 72 h in vessels to include most parts of the leaking juice amounts of Pb, compared to the other species; in average ten times per sample. After drying, the samples were ground (<100 mm) and higher than EU standard for Pb. Low average Pb contents were stored in a desiccator. Contents of Cd and Pb in the samples were detected in B. badius, A. solidipes, S. crispa, and L. scabrum. Only few analysed after digestion for subsequent determination of aqua regia samples of these species exceeded EU standard for Pb. soluble portion of elements (for details see EN13657:2002) and by Pb content of wild growing mushrooms depended on trophic 300 M.T. Schlecht, I. Saumel€ / Environmental Pollution 204 (2015) 298e305

Fig. 1. A Overview on sampling sites in different urban habitat types in Berlin, Germany. Habitat classification according to the State Development Plan BerlineBrandenburg (Berlin Department for Urban Development, 2009): light blue trapeze: road scapes (A. campestris, B); blue triangle: garden (L. scabrum, C); red circles: park (A. arvensis, D); black semicircle: cemeteries (L. scabrum, E); and green squares: forest (S. crispa, F). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) status of the species (see Tables 1 and 3). Saprotrophic mushrooms contents. We found no significant differences in Cd content be- accumulated significantly more Pb than mycorrhizal species tween trophic status types (Table 3). (Fig. 3A; mean ± SE: CMY ¼ 3.4 ± 0.4; N ¼ 82 and CSA ¼ 9.8 ± 1.1; Habitat type significantly influenced the Cd content of the N ¼ 102). fruiting bodies (Table 3). Across all species, samples harvested at Pb content of the fruiting bodies increased with the increasing cemeteries had higher Cd contents compared to samples from overall traffic burden and with the increasing number of vehicles other habitats (Fig. 3D). Cd content in Agaricus and Russula species per day on the nearest road. It was not however related to habitat, was significantly lower in forest habitats (Fig. 3F, H). presence or absence of barriers between sampling site and road or Overall traffic burden, distance to nearest road, number of ve- distance to the nearest road (Table 3; Fig. 3I). All samples from sites hicles per day on the nearest road shaped Cd content for some with high overall traffic and about 75 percent of the samples from species (Table 3). Cd content of Agaricus ssp. harvested at low traffic sites with low overall traffic exceeded EU standards for Pb. Samples areas was significantly lower than those from medium or high originating from forest habitats exceeded less often EU standard for traffic areas (Fig. 3J). 85 percent of the samples from sites with high Pb. In contrast, all samples originating from roads exceeded these overall traffic, but only 56 percent of the samples from sites with standards (Fig. 3C). low overall traffic exceeded EU standards for Cd. Our data do not The average Cd content of wild urban mushrooms was in prove the protecting function of barriers between sampling site and average 2.5 times higher than the respective EU standard (Table 2). nearby roads: sampling sites nearby high traffic roads without X. chyrsenteron, B. recticulatus, and A. solidipes had high average Cd barriers in between can be associated with high Cd samples con- contents. In contrast, fruiting bodies of S. crispa, B. badius, tent, although some samples nearby buildings as barrier accumu- C. gigantea, B. luridus, Tuber spp., and L. scabrum had low average Cd lated high amounts of Cd. M.T. Schlecht, I. Saumel€ / Environmental Pollution 204 (2015) 298e305 301

Table 1 Genera and species, common names, urban habitats (C: cemetery; F: forest; G: garden; P: park; R: roadscape) and trophic status (S: Saprotrophic; M: Mycorrhizal) of the sampled mushrooms.

Genera Species Common name Urban habitat Trophic status

Agaricus A. arvensis (Schaeff.) horse mushroom C, F, G, P, R S A. bitorquis (Quel.) Sacc. urban agaricus, sidewalk mushroom F, G, P, R S A. campestris L. field mushroom, meadow mushroom C, F, G, P, R S A. subperonatus (J.E. Lange) Singer C, F, G, P, R S A. bisporus (J.E. Lange) Imbach potabella mushroom a S Armillaria A. solidipes (FR.) Staude honey F, G, P S Boletus B. luridus (Schaeff.) Murril lurid bolete F, G, R M B. reticulatus (Schaeff.) summer cep F, G, P, R M B. badius (FR.) Fr.b bay bolete F, G M Coprinus C. comatus (FR.) Pers. shaggy ink cap F, G, P, R S Calvatia C. gigantean (Batsch) Rostk. giant puffball P S Leccinum L. scabrum (FR.) Grey birch bolete, brown birch scaber stalk C, F, G, P, R M Macrolepiota M. mastoida (FR.) Singer umbonate parasol F, P S M. procera (FR.) Singer parasol mushroom F, G, R S Russula R. exalbicans (Pers.) Melzer & Zvara C, F, G, P, R M R. vesca (FR.) bare-toothed russula, the flirt F, G, P, R M Sparassis S. crispa (FR.) cauliflower mushroom F, P S Tuber Tuber spp. trufflePM Xerocomus X. chrysenteron (Quel.)b red cracking bolete C, F, G, P, R M

a Commercial mushroom cultures exposed to high traffic areas within the inner city of Berlin, Germany. b History of mushroom is complex and an ongoing debate, e.g. Boletus badius was also named as Xerocomus badius or Xerocomus chrysenteron as Xerocomellus chrysenteron.

4. Discussion to evaluate the potential usability for urban food production. To our knowledge, our study is the first that focuses explicitly on Wild growing edible mushrooms are essential for modern wild growing edible mushrooms harvested within a major city and cuisine as an attractive and popular food source. At the same time, hereby relating trace metal content of fruiting bodies to site char- they are well known as trace metal accumulators (e.g. García et al., acteristics such as habitat type or traffic-related parameters. 2009; Kalac, 2010; Yin et al., 2012; Falandysz and Borovicka, 2013). Ranges of Cd and Pb content in urban mushrooms measured in Studied mushrooms frequently originated from polluted areas: our study are large (Table 2) and have been reported previously near motorways (García et al., 1998; Cuny et al., 2001), in sludge- from unpolluted sites (i.e. similar to our minimum to median treated areas (Zabowski et al., 1990) or in a historic silver-mining values) and from polluted sites (i.e. similar to our medium to area (Svoboda et al., 2006). Field surveys in urban areas are maximum values) for A. arvensis, A. campestris, B. badius, C. comatus, scarce but are crucial to determine health risks arising from con- L. scabrum and M. procera (see reviewed data in Al Sayegh sumption of edible mushrooms harvested in cities and furthermore Petkovsek and Pokorny, 2013;inFalandysz and Borovicka, 2013).

Table 2 Content of cadmium and lead in edible mushrooms grown in the city of Berlin in mg/kg biomass dry weight (DW): median (Med), minimum (Min) and maximum (Max); values for N samples are given; nd ¼ not determined. All samples were taken from wild growing species in different habitats (see Table 1) with the exception of the cultivated Agaricus bisporus*, that were exposed to high traffic areas within the inner city. A: Number of samples exceeded the EU standards for Cd and Pb in cultivated mushrooms (EC, 2006). B: Number of samples exceeded the EU standard for Cd in other mushrooms (EC, 2008). Water content (W) is given in percent of fresh weight. In one percent of the samples (0% of the edible mushrooms, and 13% of the cultivated mushrooms) the Cd content was below the detection limit of 0.1 mg/kg. In 23% of the samples (16% of the edible mushrooms, and 94% of the cultivated mushrooms) the Pb content was below the detection limit of 1.0 mg/kg.

Element Content of trace metals [mg/kg DW]

Pb Cd

Genus Species W N Min Med Max A Min Med Max A (B)

Agaricus A. arvensis 89 19 2.6 8.1 29.1 19 0.8 3.0 24.6 15 (3) A. bitorquis 87 11 2.3 12.8 44.6 11 0.5 2.9 12.8 8 (1) A. campestris 90 12 1.5 8.4 31.1 11 1.2 2.9 32.7 7 (4) A. subperonatus 90 9 1.9 11.8 51.0 8 0.3 3.3 10.2 6 (2) A. bisporus* 90 16 <1.0 <1.0 1.2 0 <0.1 0.2 0.4 0 (0) Armillaria A. solidipes 89 13 <1.0 <1.0 6.6 5 2.0 4.7 13.2 12 (4) Boletus B. luridus 89 7 <1.0 2.2 6.0 6 0.4 1.0 2.6 1 (0) B. recticulatus 89 7 <1.0 2.2 6.1 6 1.9 5.5 67.6 6 (2) B. badius 89 9 <1.0 <1.0 2.4 3 0.4 1.0 7.5 2 (1) Coprinus C. comatus 87 10 2.3 3.3 14.3 10 1.0 3.3 10.2 7 (2) Calvatia C. gigantea 87 6 2.4 4.3 9.6 6 0.6 1.0 1.7 0 (0) Leccinum L. scabrum 90 18 <1.0 1.4 5.4 10 0.3 1.7 4.4 7 (0) Macrolepiota M. mastoidea 89 7 2.0 3.0 8.5 6 2.0 2.8 10.4 6 (2) M. procera 87 10 4.1 13.9 51.6 10 1.0 3.3 11.5 7 (3) Russula R. exalbicans 87 11 1.9 4.8 17.9 11 1.2 2.5 3.0 8 (0) R. vesca 87 11 2.1 4.8 13.8 11 0.3 2.3 14.2 6 (1) Sparassis S. crispa 90 5 <1.0 1.4 2.1 4 0.6 0.8 2.1 0 (0) Tuber T. rufum 89 2 2.9 3.4 3.8 2 1.3 1.5 1.6 0 (0) Xerocomus X. chrysenteron 90 17 <1.0 1.7 9.0 11 1.5 6.8 22.3 15 (6) 302 M.T. Schlecht, I. Saumel€ / Environmental Pollution 204 (2015) 298e305

Fig. 2. Content of lead (A) and cadmium (B) in edible mushroom biomass in mg/kg biomass dry weight (DW). The boxplots indicate the 25th and 75th percentiles and means of the distribution. Lower case letters associated with the boxplots indicate significant interspecific differences using Bonferroni Test. The sampled mushrooms are Agaricus arvensis (AgAr), Agaricus bitorquis (AgBi), Agaricus campestris (AgCa), Agaricus suberonatus (AgSu), Armillaria solidipes (ArSo); Boletus luridus (BoLu); Boletus recticulatus (BoRe), Coprinus comatus (CoCo), Calvatia gigantea (CaGi), Leccinum scabrum (LeSc), Macroleptiota mastoidea (MaMa), Macroleptiota procera (MaPr); Russula exalbicans (RuEx), Russula vesca (RuVe); Sparassis crispa (SpCr) and Tuber ssp. (Tub), Boletus badius (BoBa) and, Xerocomus chrysenteron (XeCh). The significance level is p < 0.05. For ANOVA results see Table 2. 77 percent of all wild growing mushrooms samples exceed European limits for lead in cultivated mushrooms. 61 percent of all wild growing mushrooms samples exceed European limits for cadmium in cultivated mushrooms.

Our study demonstrated that the vast majority of the wild for Pb (EFSA, 2014). An adult consuming 300 g of wild urban growing mushrooms, and among them some excellent and popular mushrooms per week would be ingesting an average of 5% and 1% edible species of the genera Agaricus, Macrolepiota or Boletus of the accepted weekly intake of Cd, and Pb, respectively. A daily accumulate extremely high amounts of trace metals in urban areas consumption of the same amounts of wild urban mushrooms (Table 2), which frequently exceed EU standards for Pb and Cd. resulted in an average of 35% and 5% respectively of the accepted At the same time, we also identified low accumulating species daily intake. Children younger than 6 years consuming weekly such as S. crispa, B. luridus, B. badius (Table 2). There is evidence that 150 g each of these mushrooms would be ingesting an average of 9% trace metal accumulation in fruiting bodies depends on genetic and 1% respectively of the accepted weekly intake. A daily con- factors in individual species (Gadd, 2004; Campos and Tejera, sumption of the same amount of wild urban mushrooms would 2011). Interspecific differences are determined by differences in result in an average of 62% and 8% respectively of the accepted daily fungal cell wall compositions (Vimala and Das, 2009) and by the intake. At several sites, the contents of trace metals were signifi- ability of the species to extract elements from the substrate and cantly higher and would increase these ingestion values sharply. In selective uptake and deposition of the elements in the tissue (Sesli addition, seasonal variation and year specific availability of wild and Tüzen, 1999; Kalac and Svoboda, 2000). Significantly lower growing mushrooms and cooking procedures have to be consid- accumulations of elements by the lamellar were found in com- ered to determine health risks of consumers (e.g. Falandysz and parison to the tubular fungi (Mleczek et al., 2013), yet contrasting Borovicka, 2013). evidence can be found (see recent review from Falandysz and Our study highlights that site-specific characteristics signifi- Borovicka, 2013). However, reported metal concentrations can cantly shaped trace metal contents of mushrooms. Cd content differ over very wide ranges within a mushroom species and depended on habitat type (Table 3), with samples from cemeteries knowledge of factors affecting accumulation rates has been very containing higher Cd levels than forests (Fig. 3D). Cemetery soils limited (Chen et al., 2009; Falandysz and Borovicka, 2013). are characterized by high trace metal content compared to back- High accumulating mushroom species of our study (e.g. wild ground values (Fiedler et al. 2012). Consistent with our expecta- growing Agaricus ssp., M. procera, R. exalbicans, R. vesca, and tions, samples of Russula and Agaricus spp. showed lower Cd C. gigantea) had twice higher Pb contents and 10 times higher Cd contents in forest compared to other habitats (Fig. 3F,H). However contents compared to high accumulating vegetables such as chard, other samples from forest showed extremely high levels of Pb and carrots or mint (Saumel€ et al., 2012). Pb or Cd contents are several Cd (e.g. M. procera). Russula ssp. harvested at road sites contained hundred times higher than in urban non-vegetable fruits such as less Pb than samples from forests, thus samples from forest habitats berries or pomes (Von Hoffen and Saumel,€ 2014). are not always 'safer' compared to others, although samples from Depending on the consumer and the average consumption forest habitats less often exceed EU standards for Cd and Pb pattern the ingestion of these wild growing mushrooms can result (Fig. 3CeD). This paradox phenomenon has been explained by the in a possible threat to human health. The tolerable weekly intake ability of mushroom species to accumulate particular elements limits for Cd are 2.5 mg/kg body weight and 25 mg/kg body weight even when growing on uncontaminated soils and mechanisms M.T. Schlecht, I. Saumel€ / Environmental Pollution 204 (2015) 298e305 303

Fig. 3. Trace metal content in mg/kg biomass dry weight (DW) in wild edible mushroom of different trophic status (i.e. saprophytic versus mycorrhizal species; A-B), sampled from different habitats (CeD) and in Russula and Agaricus species harvested from different urban habitats (EeH) and at sites with different overall traffic burden (IeJ). The boxplots indicate the 25th and 75th percentiles and means of the distribution. Lower case letters associated with the boxplots indicate significant differences using Bonferroni Test between mushrooms of different trophic status or site characteristics. The significance level is p < 0.05. For ANOVA results see Table 2. beyond this pattern remain widely unknown (Falandysz and underlying substrate were proven only in ex-situ studies (Byrne, Borovicka, 2013). 1991; Bressa et al., 1988). However, in-situ studies report diver- Overall traffic burden and number of vehicles per day on the gent results. Some studies correlate trace metal content of terres- nearest road determined the Pb content of mushrooms and affected trial fungi with metal concentration in the local soil (García et al., the Cd content in Agaricus species (Table 3). High trace metal 2009; Jarzynska and Falandysz, 2012). Whereas other studies do contents in edible mushrooms were mainly associated with high not show a clear relationships between the contents of metals in traffic burdens nearby the sampling site (Table 2, Fig. 3IeJ). Urban fruiting bodies and the local soil (Svoboda et al., 2006) or soil pa- soils are often enriched by trace metals (Alloway, 2004; rameters were not the determinant for the uptake of trace metals Charlesworth et al., 2010). In general, soil pollution decreases (Tyler, 1982; Falandyz and Chwir, 1997; Tüzen et al., 1998). with increasing distance to roads and decreasing traffic burden Furthermore, our data provided evidence, which showed that (Hjortenkrans et al., 2008; Werkenthin et al., 2014). A direct cor- trace metal content depended on trophic status of fungi and is relation between trace metal content of the fruiting body and the consistent with studies that report higher trace metal contents in 304 M.T. Schlecht, I. Saumel€ / Environmental Pollution 204 (2015) 298e305

Table 3 ANOVA results of the species, genus and site effects as well as the interactions between species and site effects on content of cadmium and lead. Minimum adequate linear models were chosen using a step-by-step reduction of the maximum model to find the minimum value of Akaike's information criterion (AIC). The maximum model considered cadmium or lead content of biomass [mg/kg DW] in relation to species (sp), genus (ft), habitat (ha), overall traffic burden (otb), number of vehicles per day on the nearest road (tb), distance (m) to the nearest road (d), and presence or absence of barrier (b; i.e. no barriers, buildings, plantings or buildings and plantings) between sampled mushroom and streets and relevant interactions between parameters. The model with the lowest AIC value was Pb content ~ sp*g*ha*b*d*tb*otb. Cd content ~ sp*g*ha*b*d*tb*otb. F and p values are given (***p < 0.001; **p < 0.01; *p < 0.05; ns, not significant).

Element Content of trace metals

Pb Cd

Parameter Fp Fp

Species (sp) 12.6 0.005** 23.0 0.001** Genus (g) 17.0 <0.001*** 3.1 0.001** Trophic status (ts) 21 <0.001*** 0.0 0.871ns Habitat (ha) 2.3 0.197ns 22.9 0.002** Overall traffic burden (otb) 13.2 0.015* 0.9 0.375ns Presence/absence of barrier (b) 1.9 0.228ns 7.0 0.056ns Distance (m) to nearest road (d) 0.1 0.948ns 0.5 0.508ns Number of vehicles per day on the nearest road (tb) 12.6 0.016* 2.4 0.182ns Relevant interactions between parameters: sp ha 1.5 0.353ns 14.2 0.004** sp otb 2.0 0.227ns 23.1 0.001** sp b 4.5 0.055ns 5.0 0.046* sp tb 3.7 0.078ns 11.1 0.007** ha d 0.3 0.869ns 7.4 0.024* ha tb 0.8 0.572ns 11.3 0.010* b otb 17.6 0.009** 4.6 0.075ns b d 0.5 0.521ns 11.9 0.018* b tb 7.5 0.041* 43.9 0.001**

saprophytic compared to mycorrhizal fungi (Kuusi et al., 1981; traffic areas. Furthermore, our data demonstrated a high variability Lepsova and Mejstrik, 1988). Our study confirms this for Pb, but in trace metal content among mushroom species and urban sites. not for Cd (Fig 3AeB, Table 3). Higher Pb and Cd content were These patterns are only partially explained by the predictors chosen observed in Boletus species compared to saprophytic fungi species in this study. Further research is needed to highlight crop- and site- (Malinowska et al., 2004; Al Sayegh Petkovsek and Pokorny, 2013), specific monitoring to assess the potential impact on human health. while other studies have not found any difference between saprophytic and mycorrhizal fungi (Sesli and Tüzen, 1999). Fungal Acknowledgement species growing on wood generally contain lower concentrations of trace metals than fungi growing on soil (Kalac, 2010). We thank Willy Hawlik for providing mushroom cultures, the In contrast to high accumulating wild growing Agaricus conge- German Mycological Society in Berlin, Christiane Baschien and ners, A. bisporus samples cultivated at commercial substrates Reiner Konefka for sharing their expertise on mushroom identifi- exposed to similar high traffic areas within the inner city of Berlin cation and three anonymous reviewers for helpful comments. did not exceed EU standards for Pb nor Cd (Table 2). Chemical composition can differ between cultivated and wild samples of the References same species (Reis et al., 2012). The 7e14 days short growing period of the fruiting bodies on soil reduces the uptake of air pollutants (Al Aida, F.M.N.A., Shuhaimi, M., Yazid, M., Maaruf, A.G., 2009. Mushroom as a potential e Sayegh Petkovsek and Pokorny, 2013), indicating the main uptake source of prebiotics: a review. Trends Food Sci. Technol. 20, 567 575. Al Sayegh Petkovsek, S., Pokorny, B., 2013. Lead and cadmium in mushrooms from route of these toxic metals into the fruiting bodies is by means of the vicinity of two large emission sources in Slovenia. Sci. Total Environ. 443, absorption from the soil, where mycelium can live for several 944e954. months, years or decades (Svoboda et al., 2006). Alloway, B.J., 2004. Contamination of soils in domestic gardens and allotments: a brief review. Land Contam. Reclam. 12, 179e187. Barros, L., Cruz, T., Baptista, P., Estevinho, L.M., Ferreira, I.C.F.R., 2008. Wild and commercial mushrooms as source of nutrients and nutraceuticals. Food Chem. 5. Conclusion Toxicol. 46, 2742e2747. Barthel, S., Isendahl, C., 2013. Urban gardens, agriculture, and water management: sources of resilience for long-term food security in cities. Ecol. Econ. 86, The vast majority of our wild growing mushroom samples, 224e234. among popular species as M. procera, Boletus recticulantus or Berlin Department for Urban Development, 2009. Urban and environmental infor- mation system. www.stadtentwicklung.berlin.de/umwelt/info_system/index. Agaricus spp., exceeded the EU standards for cultivated mushrooms shtml. and are much higher than those of urban fruits and vegetables Breitenbach, J., Kranzlin, F., 1984. Fungi of Switzerland, vol. 1. Mykologia Verlag, harvested in the same study area (Saumel€ et al., 2012; Von Hoffen Lucerna. and Saumel,€ 2014). Taking into account the multiple additional Breitenbach, J., Kranzlin, F., 1986. Fungi of Switzerland, vol. 2. Mykologia Verlag, Lucerna. sources of human trace metal exposure in urban areas, the con- Breitenbach, J., Kranzlin, F., 1991. Fungi of Switzerland, vol. 3. Mykologia Verlag, sumption of high accumulating mushroom species should be Lucerna. limited. In contrast, cultivated mushrooms and some low accu- Boa, E., 2004. Wild Edible Fungi. A Global Overview of Their Use and Importance to People. FAO, Rome. mulating species did not exceed these limits. Consequently, there is Bohn, K., Vilijoen, A., 2011. The edible city: envisioning the continuous productive evidence that at least the consumption of cultivated mushrooms is urban landscape (CPUL). Field J. 4, 149e161. not harmful to human health and the integration of mushroom Bressa, G., Cima, L., Costa, P., 1988. Bioaccumulation of Hg in the mushroom Pleu- rotus ostreatus. Ecotoxicol. Environ. Saf. 16, 85e89. cultures can be considered as suitable for urban food production Byrne, A.R., 1991. Studies of the uptake and binding of trace metals in fungi. Part II: and can enrich the diet on a local and sustainable basis even in high arsenic compounds in Laccaria amethystina. Appl. Organomet. Chem. 5, 25e32. M.T. Schlecht, I. Saumel€ / Environmental Pollution 204 (2015) 298e305 305

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