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

Abstract

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.

Keywords: Edible fungi; Environment; Health; Metallic elements; Pollution; Soil.

Fig. 1

Natural normal- and log-normal distribution pattern of lanthanides in annual rings of pine (Pinus massoniana) growing in a REE mining area in China (A), substrates for farmed mushrooms (pine needle, corn combs and data palm tree leaves in Greece; (B) and forest topsoil from Kostryca in Belarus (C) (after Mędyk and Falandysz ; Koutrotsios et al. and Zhang et al. , respectively)

Fig. 2

Natural normal- and log-normal distribution pattern of lanthanides in forest topsoils from Serbia (XS), Germany (G), and Poland (PL) and in wild mushrooms (caps, stems, or whole) from Serbia, Germany, and Poland (after Mędyk and Falandysz ; Vukojević et al. and Zocher et al. , respectively)

Fig. 3

Natural normal- and log-normal distribution pattern of lanthanides in brown rice, tomatoes, pumpkin seeds, cheese, and muscle meat (after Danezis et al. and ; Joebstl et al. ; Spalla et al. and Tagami et al. , respectively)

Fig. 4

Natural normal- and log-normal distribution pattern of lanthanides in farmed (C. cylindracea and P. ostreatus) and wild mushrooms; whole saprotrophic and ectomycorrhizal species, caps of S. grevillei and in truffle (T. magnatum) (after Borovička et al. ; Koutrotsios et al. ; Mędyk and Falandysz , and Segelke et al. , respectively)

Fig. 5

The distribution of La, Ce, and ∑REE in mushroom species (as per Table 1) collected in Europe. Concentrations that appear overestimated are shown in red and originate from ICP-OES and/or some ICP-Quad-MS measurements