Biomonitoring chromium contamination in urban and rural topsoils from Leicestershire, England

A monitoring study was performed to characterise the risks ofchromium (Cr) in Leicestershire, England. A total of 106 wild-growing mushrooms were collected from Leicester city and Bradgate Park (a nearby rural park). Cr was monitored via ICP-MS in cleaned/dried/homogenised and appropriately mineralised mushrooms [LoD=1.012 µg/g dry weight (dw)]. Cr was also monitored in 850 topsoils collected across Leicestershire and processed as composite samples via ICP-MS after acid/microwave digestion (LoD=3.683 µg/g). Cr was detected in 92.2% of the topsoil samples and 47.1% of the mushroom samples [median and range, in µg/g dw; 0.863 (1.012-19.466)], showing significant distribution across the four ordinal directions in which Leicestershire was divided [SE (1.908) > NW (1.738) > NE (0.987) > SW (<LoD); Peto–Prentice test, χ2(2)=12.4, p-value=0.002]. These results might suggest some level of Cr pollution in Leicestershire, as they are higher than the proposed reference interval for wild mushrooms that grow in unpolluted areas (0.5-5 µg/g dw). A similar distribution of Cr was found in the monitored topsoils. The highest concentration was found in those collected in the southeast and the lowest in the southwest quadrant (123.137 vs. 20.947 µg/g). Moreover, significantly higher levels were found in topsoils collected in the urban area (median and range, in µg/g; Peto–Prentice test, χ2(1)=1.1, p-value=9x10-4): 82.542 (3.683-196.795) vs. 32.806 (3.683-265.069). This difference might be attributed to different anthropogenic sources, such as vehicles. All bioconcentration factor values were lower than one, suggesting a low bioaccumulation of Cr in the wild mushrooms species collected in Leicestershire. Toxic risks derived from oral, inhalation, and dermal exposure to Cr from topsoils in the four urban ordinal directions (NW=1.95E-01, NE=1.40E-01, SW=2.53E-01, SE=4.30E-02) were lower than one, suggesting a minimal risk for Leicester’s population. However, speciation analysis would be needed to rule out carcinogenic risks of exposure to hexavalent Cr.