22. GIS and Atmospheric Diffusion Modeling for Assessment of Individual Exposure to Dioxins Emitted from a Municipal Solid Waste Incinerator

The most potent dioxin congener (2,3,7,8-TCDD) is classified as a human carcinogen. Municipal solid waste incinerators (MSWI) are one of the major sources of dioxins and are therefore a cause of public concern. Blood dioxin levels are considered the best estimates of actual exposure, but they are costly and technically difficult to gather from individuals and to measure consistently. However, dioxins are good candidates for a combined GIS-modeling-based approach to simulate the ways in which they propagate in the environment, and the exposures that occur as a result. Dioxins are released into the air by a few known industrial point sources, and their environmental concentrations can therefore be estimated through plume modeling. Furthermore, they are known to be resistant to environmental and biological degradation, and accumulate in soils. We conducted a sequential epidemiologic investigation in the vicinity of a MSWI with high dioxin emission levels (Besançon, France). Contours of modeled ground-level air concentrations were used to assign a dioxin exposure category for any inhabitant of the town. Exposure accuracy was assessed through dioxin measurements from soil samples. In a mixed individual/ecological case-control study, a higher risk for non-Hodgkin lymphoma was found among individuals living in the area with the highest dioxin concentration (odds ratio 2.5, 95% confidence interval 1.4–4.5). The replication of these findings at the nationwide level added further evidence. GIS and exposure modeling can be considered innovative and appropriate for the assessment of dioxin exposure, moving from source identification to personal exposure estimates using environmental surrogates.