► New methodology to identify metal transfer from soil to snails. ► Internal concentration of reference (CIRef) for snails are identified for six trace elements. ► The soil parameters influence the bioavailability and transfer of metals to snails. ► The sum of excess of transfer (SET) allows the ranking of site priority management. Current soil quality evaluation does not include an assessment of metal bioavailability to organisms. However, sentinel soil-dwelling invertebrates can be used for such an assessment. This study aims to establish the modulating soil parameter of metal bioavailability to snails and a procedure for ranking field sites (n=9; 43 plots) based on the evaluation of the transfer of metals to the land snails used as indicators of metal zooavailability. Multivariate regressions identify soil pH, organic carbon and iron oxides influence cadmium, chromium, copper, lead and zinc zooavailability to snails underlining the need to consider other parameter than total soil concentration during bioavailability assessment. However, for As, no influence of soil parameter on it bioavailability to snails was identified. Internal Concentrations of Reference (CIRef) of Cd, Pb, As, Cr, Cu and Zn were determined in Cantareus aspersus that were caged on unpolluted plots. CIRef allow for the identification of contaminated sites. CIRef have revealed unexpected metal transfer on some “unpolluted” sites and a lack of transfer on some contaminated sites, thus confirming the necessity for biological measures to evaluate metal mobility. The Sum of Excess of Transfers (SET) index ranked the industrially impacted sites as the top priorities for management. We recommend that the SET methodology be used for future environmental risk assessment. By highlighting real metal transfers and considering the numerous parameters influencing environmental bioavailability, the snails watch provides information on environmental quality.