Content of manganese in the wild edible mushroom species of Agaricus bitorquis in the English city of Leicester.

Background and Aim: The aim was to assess the risks to manganese (Mn) present in wild edible mushrooms Agaricus bitorquis collected in Leicester city, England.

Methods: Twenty-two mushrooms were collected from an open green area close to St Augustine Road, a high-traffic area within Leicester. Species identification was confirmed by DNA barcoding using internal transcribed spacer 1/4 primers after extracting DNA from 100 mg of frozen homogenised ground mushroom material using a DNeasy Plant Mini Kit®. Mn was monitored by ICP-MS in cleaned/dried/homogenised mushrooms [LoD=0.529 mg/kg dry weight (dw)], and in 36 topsoil composite samples collected across the city.

Results: Mn was detected in all the samples; median and range in mg/kg dw were 10.541 (6.877-14.158). The distribution of Mn in mushroom tissues did not show statistical differences (p-value=0.1), although slightly higher levels were found in caps versus stipes (data provided as median and ranges in mg/kg dw: 10.541 (6.877-14.158) vs. 9.617 (3.665-17.154). These results agree with the literature reporting a higher accumulation of metals in the caps of wild edible mushrooms. Thus, a translocation factor of 1.096 was determined for Mn in the monitored mushrooms. Although the content of Mn in mushrooms would be minimally affected by its presence in topsoils (bioconcentration factor was lower than the unit), the levels monitored in composite topsoil samples [411.012 (253.066-730.977 mg/kg)] were studied. Non-carcinogenic risks quantified for the levels of Mn in topsoils were lower than the threshold, suggesting minimal risks to the population.

Conclusions: The levels of Mn were much higher than those detected in Agaricus bisporus species collected in a natural forest in eastern Poland (5.91 mg/kg dw), suggesting a potential contamination by Mn in the inner city of Leicester, which would be in agreement with other toxic metals monitored in these samples, such as cadmium and lead.