Comment on "Worldwide basket survey of multielemental composition of white button mushroom Agaricus bisporus": The credibility of the concentration data reported for REE are questioned - are they reliable enough to be included in the database on nutrients in mushrooms?

Rare earth contamination of edible vegetation: Ce, La, and summed REE in fungi

The increasing and diversified use of rare earth elements (REE) is considered a potential source of pollution of environmental media including soils. This work documents critically overview data on the occurrence of REE in the fruiting bodies of wild and farmed species of edible and medicinal mushrooms, as this was identified as the largest published dataset of REE occurrence in foodstuff. Most of the literature reported occurrences of cerium (Ce) and lanthanum (La), but a number of studies lacked data on all lanthanides. The Ce, La, and summed REE occurrences were assessed through the criteria of environmental geochemistry, analytical chemistry, food toxicology, mushroom systematics, and ecology. Ce and La accumulate similarly in fruiting bodies and are not fractionated during uptake, maintaining the occurrence patterns of their growing substrates. Similarly, there is no credible evidence of variable REE uptake because the evaluated species data show natural, unfractionated patterns in accordance with the Oddo-Harkins' order of environmental lanthanide occurrence. Thus, lithosphere occurrence patterns of Ce and La as the first and the third most abundant lanthanides are reflected in wild and farmed mushrooms regardless of substrate and show that Ce is around twice more abundant than La. The current state of knowledge provides no evidence that mushroom consumption at these REE occurrence levels poses a health risk either by themselves or when included with other dietary exposure. Macromycetes appear to bio-exclude lanthanides because independently reported bioconcentration factors for different species and collection sites, typically range from < 1 to 0.001. This is reflected in fruiting body concentrations which are four to two orders of magnitude lower than growing substrates. KEY POINTS: •Original REE occurrence patterns in soils/substrates are reflected in mushrooms •No evidence for the fractionation of REE during uptake by fungi •Mushrooms bio-exclude REE in fruiting bodies.

A critical review of the occurrence of scandium and yttrium in mushrooms

Scandium (Sc) and Yttrium (Y) along with the other rare earth elements (REE) are being increasingly extracted to meet the escalating demand for their use in modern high technology applications. Concern has been voiced that releases from this escalating usage may pollute environments, including the habitats of wild species of mushrooms, many of which are foraged and prized as foods. This review collates the scarce information on occurrence of these elements in wild mushrooms and also reviews soil substrate levels, including forested habitats. Sc and Y occurred at lower levels in mushrooms (<1.0-1000 µg kg-1 dw for Sc and<1.8-1500 µg kg-1 dw for Y) compared to the corresponding range for the sum of the lanthanides in the same species (16-8400 µg kg-1 dw). The reported species showed considerably more variation in Y contents than Sc which show a narrow median distribution range (20-40 µg kg-1 dw). Data allowing temporal examination was very limited but showed no increasing trend between the 1970s to 2019, nor were any geographical influences apparent. The study of the essentiality, toxicity or other effects of REE including Sc and Y at levels of current dietary intake are as yet undefined. High intake scenarios using the highest median concentrations of Sc and Y, resulted in daily intakes of 1.2 and 3.3 μg respectively from 300 g portions of mushroom meals. These could be considered as low unless future toxicological insights make these intake levels relevant.

Scandium, yttrium, and lanthanide occurrence in Cantharellus cibarius and C. minor mushrooms

There is a dearth of data on rare earth elements (REE), yttrium and scandium in foods which extends also to baseline datasets for edible wild mushrooms, though this has started to change in the last decade. Concentrations and shale normalized patterns of REE and Y (REY) were studied by using inductively coupled plasma-quadrupole mass spectrometer in 22 pools (2235 specimens) of Cantharellus cibarius (Golden Chanterelle) collected in Poland and also a pool of C. minor (Small Chanterelle) (153 specimens) from Yunnan (Chinese Province). The total REY plus Sc varied in C. cibarius from 10 to 593 µg kg^-1 dw whereas that for the Yunnan's C. minor was 2072 µg kg^-1 dw. C. minor from Yunnan has higher REY and Sc compared to the C. cibarius. Sc concentrations in twenty C. cibarius pools were below 1 µg kg^-1 dw, but 17 and 27 µg kg^-1 dw were detected at the other two sites and 66 µg kg^-1 dw was detected in C. minor. The median Y content of C. cibarius and C. minor was 22 µg kg^-1 dw and 200 µg kg^-1 dw. The difference in REY and Sc concentrations and shale normalized patterns between mushrooms from Poland and Yunnan seems to reflect the regional difference in concentration and composition of these elements in the soil bedrock.

Letter to the editor: Comment on "multiannual monitoring (1974-2019) of rare earth elements in wild growing edible mushroom species in Polish forests" by Siwulski et al. https://doi.org/10.1016/j.chemosphere.2020.127173. A recurring question - What are the real concentrations and patterns of REE in mushrooms?

Siwulski et al. (2020) investigated the occurrence of the lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), scandium (Sc) and yttrium (Y) in 4 species of wild mushrooms, which were sampled over a 45 years period in Poland. The reported mean lanthanide concentrations for mushrooms were in the range from 539 to 1601 μg kg^-1 dry weight. These values are considered as highly elevated in the light of data published earlier for the same species, where the analytical results were assessed as not being biased by errors (these could arise from contamination of the samples with soil dust or unsuitable choice of analytical methodology including the use of unsuitable analytical instrumentation for measurement). It has long been established that the lanthanides are naturally distributed in ores, soil bedrock, soils, natural waters and plants in a pattern that reflects the Oddo-Harkins rule. This pattern is correspondingly reflected in fungi, including the same species and have been published earlier by other authors. However, when the individual lanthanide concentration data of B. edulis, I. badia, L. scabrum and M. procera from the study by Siwulski et al. are plotted, they do not display the expected sawtooth (zigzag) concentration pattern - in other words, the concentration data do not follow the Oddo-Harkins rule. Lanthanides are naturally found in very low concentration in foods including wild mushrooms. There is a striking lack of convergence in the results obtained for ICP-MS techniques, and the results obtained from ICP-OES measurement (as used by Siwulski et al.). If the reasons discussed here for anomalies in the reported lanthanides data hold true, how does this affect the data for other elements in mushrooms reported in the commented article?