Dispersion modeling as a dioxin exposure indicator in the vicinity of a municipal solid waste incinerator: a validation study.

Whether low environmental doses of dioxin affect the general population is the matter of intense debate and controversy. In a previous study, we found a 2.3-fold risk for non-Hodgkin lymphoma associated with residence in areas classified as highly exposed to dioxin emitted from a municipal solid waste incinerator (MSWI) (Besançon, France). The main limitation lay within the use of a first-generation Gaussian-type dispersion model as a proxy for dioxin exposure, since its accuracy had not been assessed before. The aim of this study was to validate this geographic-based exposure through PCDD/F measurements from soil samples. PCDD/F concentration, pH, organic carbon concentration, cation exchange capacity, and geomorphology and ecology features were assessed for 75 sampling points. In simple terrain (i.e. northeast of the MSWI), a significant association was highlighted between modeled dioxin ground-level air concentrations and log-transformed measured dioxin soil concentrations with a strong gradient across exposure categories. Conversely, in a complex topography situation (i.e. southwest of the MSWI), the model overpredicted ground-level air concentrations, particularly in the high exposure zone. First-generation modeling provided a reliable proxy for dioxin exposure in simple terrain, reinforcing the results of our case-control study. However, a more advanced atmospheric diffusion model should have been used for refined assessment in complex terrain.