Artificial 137Cs and natural 40K in mushrooms from the subalpine region of the Minya Konka summit and Yunnan Province in China

Conceptualization of the comprehensive phyto-radiotoxicity incurred by radiocesium and strategies to expunge the metal using biotechnological and phytoremediative approaches

Agricultural pollution with 137Cs is an ecological threat due to its sustained half-life and radioactivity. Release of radiocesium isotopes after major nuclear power plant accidents like the Fukushima Dai-ichi and the Chernobyl nuclear power plant disasters have severely affected the surrounding growth of agricultural crops and vegetables cultivated across extensive areas. Even years after the nuclear accidents, biosafety in these agricultural fields is still questionable. Due to similarity in charge and ionic radius between radiocesium and K+, the radionuclides are promiscuously uptaken via K+ channels expressed in plants. Bioaccumulation of radiocesium reportedly promotes physiological and anatomical anomalies in crops due to radiation and also affects the rhizospheric architecture. Due to radiation hazard, the ecological balance and quality are compromised and ingestion of such contaminated food results in irreversible health hazards. Recently, strategies like exogenous supplementation of K+ or genetic engineering of K+ channels were able to reduce radiocesium bioaccumulation in plants taking the advantage of competition between radiocesium and K+ translocation. Furthermore, bioremediation strategies like phycoremediation, mycoremediation, phytoremediation and rhizofiltration have also showed promising results for removing radiocesium from polluted sites. It has been proposed that these eco-friendly ways can be adopted to de-pollute the contaminated sites prior to subsequent cultivation of crops and vegetables. Hence it is essential to: 1) understand the basic radiotoxic effects of radiocesium on agricultural crops and surrounding vegetation and, 2) design sustainable ameliorative strategies to promote radiocesium tolerance for ensuring food and social security of the affected population.

Assessment of Radium Equivalent Activity and Total Annual Effective Dose in Cassava cultivated around Ewekoro Cement Factory

In this study, cassava tubers cultivated in the Ewekoro cement area were investigated with the aid of Hyper Pure Germanium (HPGe) detector in order to assess the radionuclide content. Twenty-seven (27) samples of both arable soil and cassava tubers were studied at different sites to the epicenter of the mining activity. The results revealed the highest activity concentrations of K-40, Ra-226, and Th-232 to be 194.10, 63.92, and 76.90 Bq/kg, respectively, in soil to be at site 1, which was 50 m away from the cement mining site. Similarly, cassava reported the highest activity concentrations of 228.15 and 81.50 Bq/kg for K-40 and Ra-226, respectively, at sites 2, which was 150 m away from the mining site. However, the highest value of Th-232 in cassava was noted in site 1. Also, the highest values of Raeq for arable soil and cassava tubers were estimated to be 188.84 Bq/kg and 199.89 Bq/kg at site 1 and site 2, respectively. All the above results were higher than the recommended safe limits by a factor of 2. Moreover, the Total Annual Effective Dose of exposure by oral ingestion of cassava tubers for different age groups revealed children to have the highest level of exposure with the highest mean value of 7.98 mSv. This is followed by adults and infants, which reported 5.66 and 5.38 mSv, respectively, all at site 2. This result is far greater than the recommended safe limits of 1 mSv. Therefore, the results of the total averages of annual effective doses due to consumption of the three natural radionuclides in cassava tubers and other products from it by adults, children, and infants were found to be above the average annual ingestion radiation dose due to natural sources. Further statistical analysis of the results showed significant differences between sites 1 and 2 and between sites 1 and 3, where there was no statistically significant difference between sites 2 and 3.

Levels, sources, variations, and human health risk assessment of 90Sr and 137Cs in water and food around Sanmen Nuclear Power Plant (China) from 2011 to 2020

Objectives

Radioactivity monitoring around nuclear facilities is crucial to provide important baseline data for effective detection of radioactive leakage to the environment. We aim to establish a baseline study for monitoring radioactive levels of ⁹⁰Sr and ¹³⁷Cs around Sammen Nuclear Power Plant (SNPP) and to assess their associated health impact on surrounding residents.

Methods

In this study, we collected water and food samples around the SNPP from 2011 to 2020 and determined for ⁹⁰Sr and ¹³⁷Cs activity concentrations. We statistically analyzed the temporal trends of ⁹⁰Sr and ¹³⁷Cs and evaluated their radiation exposure to the local residents.

Results

During this period, the activity concentrations of ⁹⁰Sr and ¹³⁷Cs varied within 1.2-9.9 mBq/L and 0.10-7.6 mBq/L in water, and 0.037-1.3 Bq/kg and 0.011-0.45 Bq/kg in food, respectively, with no significant seasonal variation trend.

Conclusions

All reported activity concentrations of ⁹⁰Sr and ¹³⁷Cs were significantly lower than the recommended value of WHO and Chinese national standards. There is no indication of notable radioactive release into the study area due to the operation of SNPP during 2018-2020. The annual effective doses (AEDs) from the ingestion of ⁹⁰Sr and ¹³⁷Cs in water and food were well below the international permissible limits, indicating the radiation exposure around SNPP during 2011-2020 was kept at a safe level.

ASSESSMENT OF DOSES FROM INGESTION OF RADIONUCLIDES 40 K, 137CS, 226RA AND 232TH IN EDIBLE COMMERCIAL MUSHROOMS FROM TAIWAN

This study analyzed activity concentration and annual effective dose of radionuclides 40K, 137Cs, 226Ra and 232Th of 44 mushrooms collected from local markets in Taiwan. The 40K activity concentrations were 1570 ± 150 Bq/kg-dw (Agaricus bisporus) > 1084 ± 183 Bq/kg-dw (Flammulina velutipe) > 736 ± 150 Bq/kg-dw (Lentinula edodes). The activity concentrations of 226Ra were 5.04 ± 2.43, 4.00 ± 2.40 and 3.43 ± 2.69 Bq/kg-dw, and 232Th were 3.96 ± 2.18, 3.86 ± 1.43 and 2.90 ± 1.99 Bq/kg-dw for F. velutipe, L. edodes and A. bisporus, respectively. In seven of the 44 samples, 137Cs activity concentrations were detected, and the samples had an average of 1.55 ± 1.75 Bq/kg-dw. The total annual effective dose ranged from 0.90 to 3.50 μSv/y, with an average of 1.94 ± 0.62 μSv/y at an ingestion rate of 0.235 kg-dw/y.

Activity concentrations and bioconcentration factors (BCFs) of natural radionuclides (40 K, 226Ra, and 232Th) from cultivated substrates to mushrooms

This study examined 42 mushroom samples and corresponding cultivated substrates. The radionuclide activity concentrations and bioconcentration factor (BCF) from substrate-to-mushroom were determined. The substrate activity concentrations were 59.1-727.5, 4.5-37.6, and 4.0-53.0 Bq/kg dw (dry weight) for 40 K, 226Ra, and 232Th, respectively. The average 40 K concentrations were 1546.5, 1115.7, and 749.3 Bq/kg dw; the BCFs were 2.49, 3.56, and 5.58 for A. bisporus, F. velutipes, and L. edodes, respectively. The 40 K concentrations were insignificantly correlated with each species' corresponding substrate concentration. The 40 K BCFs had a significantly negative correlation with the substrate concentration for each species. Each mushroom species' 40 K concentration was almost stable, suggesting that 40 K has a regulated homeostasis for a given species. The average 226Ra concentrations were 5.5, 5.4, and 3.4 Bq/kg dw; the BCFs were 0.58, 0.17, and 0.50 for L. edodes, A. bisporus, and F. velutipes, respectively. The average 232Th concentrations were 4.7, 4.7, and 3.0 Bq/kg dw; the BCFs were 0.50, 0.11, and 0.53 for L. edodes, A. bisporus, and F. velutipes, respectively. The 226Ra and 232Th concentrations in mushrooms had a weak to moderate correlation with the cultivated substrate concentrations. The absorption of the 226Ra and 232Th from substrate-to-mushroom was similar to the hypothesis of the linear model that mushroom concentration yields a positive correlation with substrate concentration.

Current radioactive fallout contamination along a trans-European gradient assessed using terricolous lichens

Lichens are considered to be good indicators of contamination of the terrestrial environment. In this study, we investigated the level of ¹³⁷Cs and ⁴ K accumulated by Cladonia arbuscula and Stereocaulon alpinum along a longitudinal gradient from northern Norway, across Sweden to southern Poland. Additionally, we compared isotope contents between the selected lichen species, and investigated the correlation of the ¹³⁷Cs content accumulated by C. arbuscula with ¹³⁷Cs fallout after the Chernobyl disaster. The activity of ¹³⁷Cs varied from 3.58 Bq kg^-1 to 559 Bq kg^-1 for S. alpinum, and from 1.18 Bq kg^-1 to 130 Bq kg^-1 for C. arbuscula. The activity of ⁴ K ranged from 114 Bq kg^-1 to 341 Bq kg^-1 for S. alpinum and from 27.2 Bq kg^-1 to 314 Bq kg^-1 for C. arbuscula. The ¹³⁷Cs content did not differ between C. arbuscula and S. alpinum; however, the difference between species was significant for ⁴ K accumulation. The activity of ¹³⁷Cs in C. arbuscula was significantly correlated with deposition from 1986. Based on our findings we created a spatial map of ¹³⁷Cs activity in lichens measured 30 years after the event that was the primary source of this isotope. We showed that C. arbuscula can be used to assess contamination and create interpolation maps of radionuclide deposition, even if the primary deposition took place many years ago.

Spatial risk assessment of radiocesium contamination of edible mushrooms - Lessons from a highly frequented recreational area

The radioactive contamination of edible mushrooms increases human health hazards, especially in high mushroom collection intensity areas. Today only coarse-scale data with low spatial resolution are available, which prevents us from predicting human risk. To reduce the risk for human health, we need spatially explicit recommendations at landscape-scale. We used the Bavarian Forest National Park, a famous mushroom hunting location in Europe, as a model system. We aimed to increase the predictability of the contamination of the two most prominent mushroom species, bay boletus (Imleria badia) and ceps (Boletus edulis), and provide an efficient evidence-based risk assessment at landscape-scale. We revealed a high and a low ¹³⁷Cs-activity impact area based on soil samples, which is also reflected by the mushroom species. ¹³⁷Cs-activity of Imleria badia is about five times higher than the contamination of Boletus edulis; with one-third of the Imleria badia samples being over the statutory limit. The difference of contamination between species is more pronounced in the high-impact area. Elevation is a strong predictor in contrast to orientation of slopes. In high-impact areas, mushrooms showed higher ¹³⁷Cs-activities at lower elevations. Soil analysis revealed that the maximum of the ¹³⁷Cs-activity is still in the organic layers, indicating further mushroom contamination. We recommend using only Boletus edulis in the low-impact area for diet. We suggest that Boletus edulis bear a lower health risk than Imleria badia due to lower ¹³⁷Cs-activities. Nevertheless, we need more landscape-scale studies to assess the ¹³⁷Cs contamination risk for humans. Studies are primarily important in high-impact areas, which can be roughly identified by using soil contamination maps. The focus should be on high accumulating mushroom species like Imleria badia. Our study can serve as a blueprint to rapidly assess human health risks caused by radioactive contamination in landscapes intensively used by mushroom collectors.

137Cs and 40K activity concentrations in edible wild mushrooms from China regions during the 2014–2016 period

Introduction. Contamination by radiocaesium of edible wild mushrooms after major nuclear accidents is a long-lasting process in some regions of the world. Following greater awareness of radioactive pollution in Asia, particularly after the Fukushima accident, this study investigated the radioactivity of 137Cs and 40K contamination in edible wild mushrooms in China. Study objects and methods. The objects of the research were edible wild mushrooms collected during 2014 to 2016, from the Inner Mongolian and Yunnan regions of China. To obtain an insight into any environmental impacts to distant regions of mainland Asia, the mushrooms were analyzed for 137Cs activity. In parallel, the natural activity of 40K was also determined and used to estimate the content of total K. The topsoil underneath the mushrooms was also investigated from a few sites in Bayanhushu in Inner Mongolia in 2015. Results and discussion. The results showed that in 4 to 6 mushrooming seasons after the accident, mushrooms from both regions were only slightly contaminated with 137Cs, which implied negligible consequences. The activity concentrations of 137Cs in dried caps and whole mushrooms in 63 of 70 lots from 26 locations were well below 20 Bq kg–1 dry weight. Two species (Lactarius hygrophoroides L. and Lactarius volemus L.), from Jiulongchi in Yuxi prefecture showed higher 137Cs activities, from 130 ± 5 to 210 ± 13 Bq kg–1 dw in the caps. 40K activities of mushrooms were around two- to three-fold higher. A composite sample of topsoil (0–10 cm layer) from the Bayanhushu site (altitude 920 m a.s.l.) in Inner Mongolia showed 137Cs activity concentration at a low level of 6.8 ± 0.7 Bq kg–1 dw, but it was relatively rich in potassium (40K of 595 ± 41 Bq kg–1 and total K of 17000 ± 1000 mg kg–1 dw). Conclusion. Wild mushrooms from the Yunnan and Inner Mongolia lands only slightly affected with radioactivity from artificial 137Cs. Lack of 134Cs showed negligible impact from Fukushima fallout. Ionizing radiation dose from 137Cs in potential meals was a fraction of 40K radioactivity. The associated dietary exposure to ionizing irradiation from 137Cs and 40K contained in mushrooms from the regions studied was considered negligible and low, respectively. Mushroom species examined in this study are a potentially good source of dietary potassium.

Effect of drying, blanching, pickling and maceration on the fate of 40K, total K and 137Cs in bolete mushrooms and dietary intake

The effects of blanching, blanching and pickling and maceration on the leaching of ¹³⁷Cs and ⁴⁰K from the flesh of three edible bolete mushroom species-Boletus edulis, Leccinum scabrum and Leccinum versipelle-were investigated. Significant (p < 0.05) decreases in activity were observed but varied depending on the treatment. Relative to fresh mushrooms, blanching decreased the activity concentration of ¹³⁷Cs by 15 ± 13%, and of ⁴⁰K, by 16 ± 7%, but blanching and pickling (vinegar) reduced activity more effectively, by 55 ± 8% and 40 ± 20% respectively. The corresponding losses of ¹³⁷Cs and ⁴⁰K through maceration of dried, powdered mushrooms were 38 ± 11% and 35 ± 14% ww, respectively. These results indicate that traditional domestic processing methods may not be as efficient at excluding ¹³⁷Cs radioactivity as shown in some other studies. The activity concentration of ¹³⁷Cs in a typically sized (100 g) portion of a processed mushroom (sourced from nearshore regions of the southern Baltic Sea coast near Gdańsk in 2015) meal was projected to be low, i.e. in the range of 0.51 to 12 Bq kg^-1 ww. The corresponding effective dose of ¹³⁷Cs from blanched, blanched and pickled and macerated mushrooms per capita was also assessed to be low, from 0.001 to 0.010 μSv. Nutritionally, the median concentration of potassium (330 mg) in 100 g portions of blanched or pickled mushrooms would account for around 7% of the adequate adult daily intake.

Radiocaesium in Tricholoma spp. from the Northern Hemisphere in 1971-2016

A considerable amount of data has been published on the accumulation of radiocaesium (¹³⁴Cs and particularly, ¹³⁷Cs) in wild fungi since the first anthropogenically influenced releases into the environment due to nuclear weapon testing, usage and subsequently from major accidents at nuclear power plants in Chernobyl (1986) and Fukushima (2011). Wild fungi are particularly susceptible to accumulation of radiocaesium and contamination persists for decades after pollution events. Macromycetes (fruiting bodies, popularly called mushrooms) of the edible fungal species are an important part of the human and forest animal food-webs in many global locations. This review discusses published occurrences of ¹³⁴Cs and ¹³⁷Cs in twenty four species of Tricholoma mushrooms sourced from the Northern Hemisphere over the last five decades, but also includes some recent data from Italy and Poland. Tricholoma are an ectomycorrhizal species and the interval for contamination to permeate to lower soils layers which host their mycelial networks, results in a delayed manifestation of radioactivity. Available data from Poland, over similar periods, may suggest species selective differences in accumulation, with some fruiting bodies, e.g. T. portentosum, showing lower activity levels relative to others, e.g. T. equestre. Species like T. album, T. sulphurescens and T. terreum also show higher accumulation of radiocaesium, but reported observations are few. The uneven spatial distribution of the data combined with a limited number of observations make it difficult to decipher any temporal contamination patterns from the observations in Polish regions. When data from other European sites is included, a similar variability of ¹³⁷Cs activity is apparent but the more recent Ukrainian data appears to show relatively lower activities. ⁴⁰K activity in mushrooms which is associated with essential potassium, remains relatively constant. Further monitoring of ¹³⁷Cs activity in wild mushrooms would help to consolidate these observations.

Radiocaesium Contamination of Mushrooms at High- and Low-Level Chernobyl Exposure Sites and Its Consequences for Public Health

We compare the specific activities of 137Cs and 40K in stipes and caps of three different common mushroom species (Xerocomus badius, Russula ochroleuca and Armillariella mellea) measured at the Czech Chernobyl hot spot in the Opava area (Silesia) and at a low-exposed site at the Beskydy mountains in 2011. The highest values of 137Cs were found in caps of Xerocomus badius and Russula ochroleuca in the Opava area (11.8 and 8.77 kBq/kg, respectively). The source of 137Cs was verified by the measurement of the 134Cs/137Cs ratio. Based on our results, we estimate an effective dose per year due to radiocaesium intake in the two investigated areas for Xerocomus badius, one of the most popular edible mushrooms in the Czech Republic. In 2011, the effective dose reached the maximum value of 0.102 mSv in the Opava area and 0.004 mSv at the low-exposed site at the Beskydy mountains. Therefore, it does not represent a significant risk for public health.

Long-term variation of 90Sr and 137Cs in environmental and food samples around Qinshan nuclear power plant, China

Environmental radioactivity monitoring in the surroundings of nuclear facilities is important to provide baseline data for effective detection in case of any radioactive release in the region. In this work, we report for the first time the long-term monitoring data of ¹³⁷Cs and ⁹⁰Sr in environmental and food samples around Qinshan nuclear power plant in 2012–2019. The distribution levels, temporal variations and source terms of ¹³⁷Cs and ⁹⁰Sr in the investigated samples were discussed. The annual effective dose (AED) for the local population from the ingestion of foods was also evaluated. Peak values of ⁹⁰Sr and ¹³⁷Cs concentrations and ¹³⁷Cs/⁹⁰Sr activity ratio were observed in total atmospheric deposition in 2016 and some water and food samples in the following years. This seems to be associated to an additional radioactive input, mostly likely from the operational release of a local facility. This demonstrates that ⁹⁰Sr and ¹³⁷Cs, especially the ¹³⁷Cs/⁹⁰Sr activity ratio, are sensitive indicators for detecting potential radioactive releases. Nevertheless, overall ⁹⁰Sr and ¹³⁷Cs activity concentrations measured during 2012–2019 in this work were at the background levels with average AED far below the internationally permissible limit and recommendation.

Natural radioactivity and total K content in wild-growing or cultivated edible mushrooms and soils from Galicia (NW, Spain)

The radioactive isotope, ⁴⁰K, of naturally occurring potassium (0.012%) is present in the Earth's crust in a low percentage of all potassium, leading to its presence in almost all foodstuffs. The impact of ⁴⁰K activity concentrations was assessed in wild and cultivated edible mushrooms and in growing substrates. Samples were analysed by gamma spectroscopy. In the wild mushroom species, the average activity concentration of ⁴⁰K was 1291 Bq kg^-1 dry weight (dw), approximately 140 Bq kg^-1 fresh weight (fw), with a range of average values per species from 748 in Lactarius deliciosus to 1848 Bq kg^-1 dw in Tricholoma portentosum. The cultivated species presented an average value of 1086 Bq kg^-1 dw; and the soils, compost of cultivation and wood of substrate are 876, 510 and 59.4 Bq kg^-1 dw, respectively. The total K content reached a maximum of 59,935 mg kg^-1 dw in T. portentosum. The transfer factors (TF > 1) suggested that mushrooms preferentially bioconcentrated ⁴⁰K. Cantharellus cibarius, Craterellus tubaeformis, Hydnum repandum and T. portentosum by most TF could be considered as bioindicators of ⁴⁰K. Taking into account that the annual radiation dose of ⁴⁰K due to the average consumption of mushrooms analysed (0.15 μSv/year) is very low, it can be concluded that the consumption of these mushrooms does not represent a toxicological risk for human health. Finally, according to the total K content, from the nutritional point of view, these mushrooms could be considered as a potential source of potassium for the human diet.

Radiocesium in Shiitake mushroom: Accumulation in living fruit bodies and leaching from dead fruit bodies

In this paper, cesium (Cs) accumulation by the saprophytic fungus Lentinula edodes (Shiitake) was investigated to contribute to the elucidation of radiocesium-cycling mechanisms in forest environments. Although the ¹³⁷Cs in the mushroom bed before culture was bioavailable, the transfer factor (TF) of Cs (¹³³Cs and ¹³⁷Cs) from the mushroom bed to fruit bodies was low (approximately 1) and the TFs of K (5) and Na (1.5) were higher. Cs and K concentrations in fruit bodies at different maturity stages were almost constant. The concentration ratio of Cs/K is constant in the pileus regardless of the pileus tissues. These results demonstrate that Shiitake non-specifically accumulates Cs while accumulating the essential element K and provide evidence that no selective Cs accumulation (or binding) sites exist within the Shiitake fruit body. Furthermore, the present results show that most accumulated Cs quickly leaches out from the dead fruit body with exposure to water. The leached Cs was largely adsorbable on clay minerals, suggesting that the Shiitake fruit body likely contains Cs in the cation form.

137Cs and 40K activities and total K distribution in the sclerotia of the Wolfiporia cocos fungus from China

The activity concentration of ¹³⁷Cs and ⁴⁰K and total K content in the sclerotia of the Chinese medicinal fungus Wolfiporia cocos collected mainly from Yunnan province of China during the period 2013-2015 were investigated. W. cocos in Yunnan is collected from the wild and is cultivated in field conditions and the wood substrate used is derived from the local pine (Pinus yunnanensis Franch.) logs from neighborhood forests. The outer part of sclerotia was found to be richer than the inner one in both ¹³⁷Cs and ⁴⁰K with median values of 7.3 and 3.2 Bq kg^-1 dry weight (dw) for ¹³⁷Cs, 220 and 140 Bq kg^-1 dw for ⁴⁰K. The median K concentrations were 6800 mg kg^-1 dw in the outer and 3700 mg kg^-1 dw in the inter parts. No statistically significant correlation was found for activity concentrations between the inner and outer parts, both for ¹³⁷Cs and ⁴⁰K (p > 0.05). Using the median activities of ¹³⁷Cs, the nominal values of effective dose (mSv) for exposed adults annually consuming 50 g of sclerotia, were estimated at 0.0035 mSv and 0.084 mSv (outer part), and 0.0020 mSv and 0.040 mSv (inner part) per capita, respectively. Sclerotia of W. cocos seemed to be a relatively good source of K.

The effects of different cooking modes on the 137Cs, 40K, and total K content in Boletus edulis (King Bolete) mushrooms

This study aimed to get an insight into the effects of household processing on the leaching behaviour of ¹³⁷Cs and ⁴⁰K from fresh, frozen and dried Boletus edulis (King Bolete) mushrooms. Three processes were investigated-blanching, blanching and pickling, and drying followed by grinding and soaking. The activity concentrations of ¹³⁷Cs and ⁴⁰K in the fresh unprocessed mushrooms were 270 Bq kg^-1 dry biomass (27 Bq kg^-1 whole weight) and 590 Bq kg^-1 db (59 Bq kg^-1 ww), respectively. Blanching of fresh mushrooms decreased ¹³⁷Cs activity by 55%, and ⁴⁰K activity by 34%, and blanching of deep-frozen mushrooms caused a reduction of 52% and 44% (db) (equivalent to whole weight reductions of 37% and 8.5%, and 67% and 22%, respectively). Blanching and pickling of fresh mushrooms decreased ¹³⁷Cs activity by 83% and ⁴⁰K activity by 87%, while blanching deep-frozen mushrooms resulted in decreases of 88% and 80% (db) (whole weight decreases of 77% and 81%, and by ~ 84% and 72%, respectively). This study confirms earlier reports that blanching of fresh or frozen mushrooms alone is not as efficient at removing ¹³⁷Cs as blanching followed by pickling. The study also shows that the initial rate of fruiting body disintegration and pre-preparation (comparing fresh, deep-frozen, or dried and ground) can have an impact on the leaching rate of the water soluble fraction of metallic elements.

An evaluation of the occurrence and trends in 137Cs and 40K radioactivity in King Bolete Boletus edulis mushrooms in Poland during 1995-2019

B. edulis, collected from 33 forested or woodland sites across Poland over 25 years since 1995, were analysed for radiocaesium. The results (137Cs activity range: 25 to 10,000 Bq kg-1 dry weight) provide a good indication of artificial radioactivity in this food material. The relatively higher levels detected in the earlier years, mostly in easterly location, is consistent with depositions from the projected Chernobyl incident (1986) fallout plumes. Nevertheless, the 137Cs concentrations during 1995-2010 were, on average, higher than those reported by other studies for Polish B. edulis over the period 1986-1994. The data concurs with the general hypothesis and observations that deposited 137Cs permeates slowly over time to deeper soil horizons which host the mycelial networks. This delay in availability shows that (apart from hotspots) higher contamination of fruiting bodies occurred around 10 to 20 years after the incident. Local consumers and recreational mushroomers were undoubtedly exposed, although reported 137Cs concentrations suggest that serious breaches of regulated levels were uncommon.

A Review of the Occurrence of Alpha-Emitting Radionuclides in Wild Mushrooms

Alpha-emitting radioisotopes are the most toxic among all radionuclides. In particular, medium to long-lived isotopes of the heavier metals are of the greatest concern to human health and radiological safety. This review focuses on the most common alpha-emitting radionuclides of natural and anthropogenic origin in wild mushrooms from around the world. Mushrooms bio-accumulate a range of mineral ionic constituents and radioactive elements to different extents, and are therefore considered as suitable bio-indicators of environmental pollution. The available literature indicates that the natural radionuclide 210Po is accumulated at the highest levels (up to 22 kBq/kg dry weight (dw) in wild mushrooms from Finland), while among synthetic nuclides, the highest levels of up to 53.8 Bq/kg dw of 239+240Pu were reported in Ukrainian mushrooms. The capacity to retain the activity of individual nuclides varies between mushrooms, which is of particular interest for edible species that are consumed either locally or, in some cases, also traded on an international scale. The effective radiation dose from the ingestion of this food can reportedly range from 0.033 µSv/kg dw to 26.8 mSv/kg and varies depending on the country. Following pollution events, such consumption may expose consumers to highly radiotoxic decay particles produced by alpha emitters.

137Cs, 40K, and K in raw and stir-fried mushrooms from the Boletaceae family from the Midu region in Yunnan, Southwest China

The parallel batches of the same species and geographical origin mushrooms both raw and stir-fried were investigated to get an insight into the content and intake of ¹³⁷Cs, ⁴⁰K, and K from mushroom meals. The Boletaceae family species (Baorangia bicolor, Boletus bainiugan, Butyriboletus roseoflavus, Retiboletus griseus, Rugiboletus extremiorientalis, and Sutorius magnificus) were collected from the Midu County (Dali Bai Autonomous Prefecture) in 2018. The activity concentrations of ¹³⁷Cs in the caps of dried raw mushrooms were in the range 14 ± 1 Bq kg^-1 dry biomass (db) (R. griseus) to 34 ± 2 Bq kg^-1 db (R. extremiorientalis), and in stems from 16 ± 1 Bq kg^-1 db (B. bicolor and B. bainiugan) to 23 ± 1 Bq kg^-1 db (R. extremiorientalis). The mean activity concentration in the whole fruiting bodies in all six species was 18 ± 4 Bq kg^-1 db. The activity concentrations of ¹³⁷Cs were roughly the same in both dehydrated materials, stir-fried, and raw mushrooms, while the contents of ⁴⁰K and stable K were around 2- to 3-fold smaller in stir-fried than raw product. The raw and stir-fried mushrooms on a whole (wet) weight basis showed activity concentrations of ¹³⁷Cs in the range from 1.2 to 3.2 Bq kg^-1 ww (mean 1.9 ± 0.6 Bq kg^-1 ww) and 6.0 to 9.4 Bq kg^-1 ww (mean 7.0 ± 1.2 Bq kg^-1 ww), respectively. Evidently, when expressed on a whole (wet) weight basis, the cooked mushrooms showed on average around 3.5-fold greater activity concentration of ¹³⁷Cs when compared with raw mushrooms. The ¹³⁷Cs, ⁴⁰K, and total K enrichment in stir-frying (in a whole (wet) weight basis for the meal), confronted with the results for dehydrated raw and fried mushrooms, show the direct correlation with loss of mass (largely moisture) during the cooking procedure but not much of ¹³⁷Cs and ⁴⁰K. Edible wild mushrooms from Yunnan were little contaminated with radiocaesium. As assessed, the mean radioactivity dose from natural ⁴⁰K in around 9.3-fold exceeded the dose obtained for artificial ¹³⁷Cs from stir-fried mushroom meals, which both were very low doses.

Bolete mushroom Boletus bainiugan from Yunnan as a reflection of the geographical distribution of 210Po, 210Pb and uranium (234U, 235U, 238U) radionuclides, their intake rates and effective exposure doses

This pioneering study aimed to determine the activity concentrations of ²¹⁰Po, ²¹⁰Pb and uranium (²³⁴U, ²³⁵U, ²³⁸U) radionuclides in fruit bodies of wild bolete Boletus bainiugan Dentinger and to estimate its edible safety, which may give scientific evidence for the consumption of this species. The analyses were performed using alpha spectrometer after digestion, exchange resins separation and deposition. Measurement data were analysed and interpolation maps reflecting ²¹⁰Po, ²¹⁰Pb and uranium (²³⁴U, ²³⁵U, ²³⁸U) geographical distribution in Yunnan province (China) were presented. In addition, from the perspective of food safety, the possible related effective radiation dose to mushrooms consumers were estimated. The results indicated that ²¹⁰Po, ²¹⁰Pb and uranium (²³⁴U, ²³⁵U, ²³⁸U) radionuclides contents in B. bainiugan were significantly different with respect to geographical distribution, and their possible intake in a part of the region was considerably higher. A very interesting observation was done according to the values of ²³⁵U/²³⁸U activity ratio indicating the occurrence of uranium faction from the global fallout of nuclear weapon tests.

Radiotoxic 210Po and 210Pb in uncooked and cooked Boletaceae mushrooms from Yunnan (China) including intake rates and effective exposure doses

The article presents results of a study on the radioactivity and exposure from a highly toxic alpha-radiation emitter polonium ²¹⁰Po, and beta emitter lead ²¹⁰Pb in several species of Boletaceae mushrooms and stir-fried mushroom meals from China. Edible mushrooms can efficiently concentrate some elements in flesh but little is known on highly toxic alpha- and beta emitters. In this study, the absolute values of radioactivity (Bq·kg^-1 dry weight) for ²¹⁰Po were in the range 2.0 ± 2.0 to 308 ± 9 in fresh species and 22.1 ± 1.2 to 142 ± 4 in a ready to eat meals, and for ²¹⁰Pb were 3.6 ± 0.5 to 51.8 ± 2.9 and 3.0 ± 0.14 to 9.6 ± 0.5, respectively. The studied batches of a corresponding species of mushrooms - raw and cooked - were not equivalent regarding the homogeneity of the composition. However the raw mushrooms (ingredient for any cooking), showed greater radioactivity in relation to stir-fried meals, and that can imply on a partial loss of nuclides. A daily portion of 100 g of stir-fried mushrooms could provide ²¹⁰Po and ²¹⁰Pb radiation in the range 0.2-2.1 μSv and 0.02-0.06 μSv, respectively. Assessed, the cumulative doses of exposure to ²¹⁰Po were 1.4-14 μSv in a week period and 75-722 μSv at annual timescale, and of ²¹⁰Pb amounted at 0.15-0.46 μSv and 8.3-24 μSv, respectively. The ²¹⁰Po can be possibly considered as a major source of ionizing radiation activity for persons with high mushroom meals consumption in SW Asia, while the number of available data is limited.

Artificial (137Cs) and natural (40K) radioactivity and total potassium in medicinal fungi from Yunnan in China

Evaluated has been radioactive contamination with ¹³⁷Cs in parallel to occurrence of ⁴⁰K and total K in 31 species of medicinal mushrooms from Yunnan, China. We chose species that were not previously studied. The activity concentrations of ¹³⁷Cs in the medicinal fungi in this study were low. The maximum values were 54 ± 4 Bq kg^-1 dry biomass (db) in caps and 48 ± 5 Bq kg^-1 db in stipes of saprotrophic fungus Gerronema xanthophyllum from the family of Tricholomataceae. Mushrooms with relatively higher activity concentrations of ⁴⁰K were among the non-polypore species but certain species from the genus Ganoderma such as G. applanatum, G. capense, G. philippii and G. sinense showed ⁴⁰K in the higher range of 900 ± 240 to 1400 ± 340 Bq kg^-1 db. The concentrations of total K in the fungal materials in this study were in the range from 2.9 ± 6.5 g kg^-1 db in Fomes rufolaccatus to 110 ± 6 g kg^-1 db in G. xanthophyllum. The species studied, which represented both some popular wood-decaying polypore fungi but also terrestrial forms from the herbal medicine of China, can be considered as little contaminated with ¹³⁷Cs and potentially good source of leachable K in extract and decoction or as a powdered form in capsules.

Extensive analysis of radiocesium concentrations in wild mushrooms in eastern Japan affected by the Fukushima nuclear accident: Use of open accessible monitoring data

After the Fukushima Daiichi Nuclear Power Plant accident, there has been an increasing concern regarding the contamination of wild mushrooms with radiocesium (¹³⁴Cs and ¹³⁷Cs) in eastern Japan. In this study, we analyzed the radioactivity monitoring data of 3189 wild edible mushrooms of 107 species collected by the 265 local municipalities in eastern Japan to investigate the radiocesium levels in wild mushrooms. Results of the analysis showed that radiocesium concentrations in mushrooms were normalized with radioactivity deposition data from aircraft monitoring, and then we evaluated the effects of species, sampled location, sampling year and regional deviation between ¹³⁴Cs and ¹³⁷Cs activity of specimens using a hierarchical Bayesian approach considering spatial autocorrelation (an intrinsic CAR model). Normalized activity concentration by species ranged from 1.1×10^-4 to 2.3×10^-2 (m² kg^-1, fresh weight). As reported in previous studies, the mycorrhizal species tended to have higher radiocesium concentrations. Some saprophytic species (e.g. Pholiota lubrica) also had high concentrations. For the mushroom species that were also evaluated in the post-Chernobyl studies, we found that the same species had similar trends of absorption capacities. Our results indicate the extensive analysis of public monitoring data is helpful to understand the situation of mushroom contamination and evaluate the internal dose by ingestion of wild mushrooms according to species and areas.

137Cs and 40K in Cortinarius caperatus mushrooms (1996-2016) in Poland - Bioconcentration and estimated intake: 137Cs in Cortinarius spp. from the Northern Hemisphere from 1974 to 2016

Cortinarius caperatus grows in the northern regions of Europe, North America and Asia and is widely collected by mushroom foragers across Europe. This study shows that in the last three decades since the Chernobyl nuclear accident, C. caperatus collected across much of Northern Poland exhibited high activity concentrations of radiocaesium (¹³⁷Cs) - a long-lived radionuclide. The mushroom appears to efficiently bioconcentrate ¹³⁷Cs from contaminated soil substrata followed by sequestration into its morphological parts such as the cap and stipe which are used as food. The gradual leaching of ¹³⁷Cs into the lower strata of surface soils in exposed areas are likely to facilitate higher bioavailability to the mycelia of this species which penetrate to relatively greater depths and may account for the continuing high activity levels noticed in Polish samples (e.g. activity within caps in some locations was still at 11,000 Bq kg^-1 dw in 2008 relative to a peak of 18,000 in 2002). The associated dietary intake levels of ¹³⁷Cs have often exceeded the tolerance limits set by the European Union (370 and 600 Bq kg^-1 ww for children and adults respectively) during the years 1996-2010. Human dietary exposure to ¹³⁷Cs is influenced by the method of food preparation and may be mitigated by blanching followed by disposal of the water, rather than direct consumption after stir-frying or stewing. It may be prudent to provide precautionary advice and monitor activity levels, as this mushroom continues to be foraged by casual as well as experienced mushroom hunters.

Accumulation of U, Th, Pb, V, Rb, and Ag in wild mushrooms Macrolepiota procera (Scop.) Singer from Goč, Serbia

In this study, the content of U, Th, Pb, V, Rb, and Ag in 19 soil samples from unpolluted Goč Mountain area (Serbia) was determined. The same elements were determined in 19 Macrolepiota procera samples, separately for caps and stipes. Soil samples were subjected to the BCR sequential extraction procedure. Element contents were determined by inductively coupled plasma mass spectrometry (ICP-MS). Obtained soil values for U were in the range from 0.30 to 0.86 mg/kg and for Th from 1.7 to 13.2 mg/kg. These values are the first for background levels at unpolluted Goč area, and they are lower than the corresponding values for European unpolluted soil. The mean values in soil for Pb, V, Rb, and Ag were 27.6, 57.4, 15.8, and 0.76 mg/kg, respectively. PCA was applied to establish criteria for translocation of the analyzed elements between two parts of the mushroom. Efficient translocation for all elements except Ag as the main amount of the elements was found in caps. The mean content in the caps for U and Th was 4.3 and 63 μg/kg, respectively. Bioconcentration factors were much higher than 1 only for Rb and Ag. M. procera only weakly accumulates U and Th from soil in unpolluted areas. These findings indicate limited role of M. procera in the mycoremediation of the mentioned actinides.

210Po and 210Pb in forest mushrooms of genus Leccinum and topsoil from northern Poland and its contribution to the radiation dose

Wild growing mushrooms are traditional food items for man and also an important source of nutrients for small and big wildlife. Nevertheless, they can be species - specifically vulnerable for contamination with heavy metals and radionuclides. We studied a less known phenomenon of accumulation of highly toxic, the alpha-radiation emitter such as ²¹⁰Po and the beta emitter ²¹⁰Pb by three Leccinum mushrooms: orange oak bolete L. aurantiacum (Bull.) Gray (previous name Leccinum aurantiacum var. quercinum Pilát), foxy bolete L. vulpinum Watling and slate bolete L. duriusculum (Schulzer ex Kalchbr.) Singer. Fungal and soil materials were collected from areas of a different geochemical composition in the northern regions of Poland. In parallel evaluated was the risk to human consumer due to possible intake of ²¹⁰Po and ²¹⁰Pb with a mushroom meal. Results showed a heterogeneous distribution of ²¹⁰Po and ²¹⁰Pb activity concentrations within caps and stipes of fruiting bodies. Overall activity concentration for whole dried fungi material ranged from 0.59 ± 0.38 to 3.2 ± 0.2 Bq ²¹⁰Po kg^-1 and from 0.45 ± 0.04 to 3.1 ± 0.2 Bq ²¹⁰Pb kg^-1. Evaluation showed that Leccinum mushrooms consumed by locals in typical quantity of 0.5 kg (dry biomass) can contribute into annual effective radiation dose at 0.90-3.81 μSv from ²¹⁰Po decay and 0.31-2.14 μSv from ²¹⁰Pb decay, which is a small portion of the annual effective radiation dose of ²¹⁰Po and ²¹⁰Pb for human inhabiting the northern regions of Poland.

Mineral constituents in Leccinum scabrum from lowland locations in the central Europe and their relation to concentration in forest topsoil

Leccinum scabrum is an edible mushroom common in European regions in the northern hemisphere. Macro and trace mineral constituents such as Ag, Al, Ba, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, P, Rb, Sr and Zn were studied in L. scabrum and in the top soil collected from the same location underneath soil substratum. The "pseudo-total" and labile (extractable fraction of minerals) were measured to get insight into the levels, distribution between the morphological parts of fruiting bodies, potential for their bioconcentration by mushroom and evaluated for human exposure via consumption of the mushroom. The sampling sites include the Darżlubska Wilderness, Trójmiejski Landscape Park, Sobieszewo Island, Wdzydze Landscape Park and outskirts of the Kętrzyn town in Mazury from the norther part of Poland. Median values of K, Rb and P concentrations in dehydrated L. scabrum were for caps in range 27,000-44,000 mg kg^-1, 90-320 mg kg^-1 and 6,200-9,100 mg kg^-1, and followed by Mg at 880-1,000 mg kg^-1, Ca at 48-210 mg kg^-1 and Al at 15-120 mg kg^-1. The median concentrations of Cu, Fe, Mn and Zn in caps were in range 15-27 mg kg^-1 db 38-140 mg kg^-1, 5.3-27 mg kg^-1 and 130-270 mg kg^-1. For Ba and Sr, concentrations on the average were at ∼1 mg kg^-1, and almost equally distributed between the caps and stipes of the fruiting bodies. L. scabrum mushrooms were low in toxic Ag, Cd, Hg and Pb, for which the median values in dried caps from five locations were, respectively, in range 0.48-0.98 mg kg^-1 (cap to stipe index, Q_C/S, was 2.5-4.1), 1.0-5.8 mg kg^-1 (Q_C/S 2.9-3.8), 0.36-0.59 mg kg^-1 (Q_C/S 1.6-2.7) and 0.20-0.91 mg kg^-1 (Q_C/S 1.2-1.9). Substantial variations in the concentrations of the "pseudo-total" fraction (extracted by aqua regia) or labile fraction (extracted by 20% solution of nitric acid) of the elements determined in forest topsoils were noted between some of the locations examined. The elements K, P, Cd, Cu, Hg, Mn, Na, Rb and Zn can be considered as those which were bioconcentrated by L. scabrum in fruiting bodies, while the rates of accumulation varied with the sampling location.