INTRODUCTION Oral bioaccessibility - the fraction of soil contaminant that dissolves in the human gastrointestinal tract - can be evaluated using various chemical extraction tests, some of which are designed to mimic biochemical conditions. As for any other partial extraction tests, bioaccessibility can be expected to be influenced not only by the soil parameters, but also by the characteristics of the contamination, such as the metal speciation, the contamination aging, etc. Here, we try to relate bioaccessibility measurements to factors that can only be obtained when the sampled soils are surveyed and mapped at a regional scale. The factors we consider are the type of industrial activity responsible for soil contamination in industrialized areas, the land-use, and the regional level of contaminant concentrations. The question which we address is whether a fixed bioaccessibility value can be proposed for risk-based approach of contaminated land or a variable bioaccessibility value must be considered in order to take into account regional differences. To substantiate our conclusions about the influence of these factors on bioaccessibility measurements, chemical sequential extraction tests were also performed on the same soil samples. MATERIALS AND METHODS In the course of the POLLUSOL 2 survey, 237 topsoil samples have been collected in urban parks, vegetable gardens and forests within several industrial areas of Wallonia (South Belgium). The in-vitro oral bioaccessibility test used in this study is Unified BARGE Method (UBM). We looked at the ‘stomach’ compartment of the test for the 237 samples, and at the ‘stomach and intestine’ compartment for a subset of 178 samples. Analysis of the extracts for eight trace metal elements (As, Cd, Co, Cr, Cu, Ni, Pb, Zn) was carried out by ICP-AES. Total metal contents were measured by aqua regia extraction and ICP-AES. The sequential extraction was performed on a subset of 103 samples out of the 237 using the modified three-step BCR extraction procedure, whose purpose is ...