Metal(loid)s in urban and rural composite topsoils from Leicester and Leicestershire, UK: spatial patterns, enrichment and screening-level health assessment.
This area-level composite topsoil study found differing urban and rural metal(loid) patterns around Leicester, with precautionary screening calculations indicating child hazard indices above unity mainly from arsenic but no measured human exposure, cancer outcome, or pediatric-oncology endpoint.
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This area-level composite topsoil study found differing urban and rural metal(loid) patterns around Leicester, with precautionary screening calculations indicating child hazard indices above unity mainly from arsenic but no measured human exposure, cancer outcome, or pediatric-oncology endpoint.
Research significance
The record provides no therapeutic hypothesis or treatment evidence; at most, it supports the inference that confirmatory exposure assessment could identify environmental risk-management opportunities for children, but any relevance to cancer prevention is untested.
Source abstract
Urban green-space topsoils can retain persistent metal(loid) signatures from parent material, historical industry, traffic emissions, atmospheric deposition and reworked urban materials. This study assessed As, Be, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn in composite topsoils from Leicester and Leicestershire, United Kingdom, using an area-level geochemical screening design. Eighteen urban parks/open spaces and eight rural areas were sampled through 850 field increments. Within each area, the increments were pooled and homogenised to form one area-level composite, from which two separately identified laboratory samples were obtained, yielding 52 samples. These samples were subsequently subsampled for independent analytical processing, resulting in 102 valid analytical subsamples. Target elements were determined by inductively coupled plasma mass spectrometry after HNO₃/HCl pseudo-total digestion, except Fe, which was measured by atomic absorption spectrometry; Cd and Cr were treated as left-censored variables without substitution. Urban topsoils showed higher Cr, Cu and Zn, consistent with diffuse urban, traffic-related and historical land-use influences, whereas rural topsoils showed higher As and V, supporting stronger parent-material, clay/oxide or soil-matrix control. Atlas-normalised pollution index, enrichment factor and pollution load index values indicated mild to moderate enrichment, with the south-west quadrant showing the clearest cumulative signal and Cu and Pb the strongest Fe-normalised enrichment. Principal component analysis and Spearman correlation structure distinguished an Fe-As-V matrix-related component from enrichment-sensitive Cr-Cu-Pb/Ni/Cd/Zn behaviour. Screening-level health calculations identified child resident/public-access hazard indices above unity under precautionary assumptions, mainly because of As, while adult resident and worker hazard indices remained below unity. Pb screening ratios were below unity and estimated cancer risks fell within 10⁻⁶-10⁻4. These results provide composite-derived geochemical screening evidence, not a statutory contaminated-land assessment.