Distribution of geogenic arsenic in European topsoil and potential concerns for food safety

Arsenic (As) is naturally present in trace amounts in most soils and poses a public health risk when elevated in topsoil due to potential accumulation in agricultural products. Europe has several regions with natural As enrichment in soils, but since soil analyses are limited to individual soil samples, information on the spatial distribution has been lacking. This study uses expert-based machine learning to create a high-resolution map of As exceeding 20 mg/kg in European topsoil based on ∼4100 data points of the Geochemical Mapping of Agricultural and Grazing Land Soil in Europe (GEMAS) dataset and 15 environmental variables. The resulting pan-European probability map delineates areas with high soil arsenic concentrations due to natural processes. The study finds that 11.7 % of grassland and 3.9 % of cropland in Europe have arsenic levels above this threshold, with France, Spain, the Western Balkans, and mountain areas most affected. Commonly grown crops in these areas include wheat, maize, rapeseed, and fodder crops. Our research links elevated arsenic levels to areas with low soil water erosion. SHapley Additive exPlanations (SHAP) analysis was used to identify key predictors, which may also be relevant in other regions globally. The high-resolution As map offers valuable insights for agricultural and health professionals and policy-makers.