Dioxin concentrations in the atmosphere over Seveso

During the Seveso accidental, a substantial amount of the 2,3,7,8-tetrachlo rodibenzo-p-dioxin (TCDD) isomer, released into the atmosphere by a reactor explosion, spread over a large area surrounding the ICMESA factory. The mo st contaminated soil was collected and stored in a safe landfill, while in the less contaminated area, the upper soil was mixed with the uncontaminate d underlying layers to lower the dioxin concentration to the safety level. As a result of these activities, low but measurable levels of 2,3,7,8-TCDD remained in the soil of the area involved in the accident. Twenty years lat er, it is reasonable to assume that due to the extremely long half-life of 2,3,7,8-TCDD in the environment, the order of magnitude of residual dioxin concentration in the surface soil near Seveso should not be substantially d ifferent. To explore whether, or not, the mobilization of soil particles co ntributes to the atmospheric concentration of dioxin in this area, air samp les were collected from four sites in the Seveso area and one site in Milan (taken as a control) using high-volume air samplers. The preliminary resul ts, obtained over a short period of time, showed that the composition of th e: atmospheric dioxin isomers mixture in the atmosphere over Seveso were no t significantly different from that of the control area. This suggests that there is no major contribution of the 2,3,7,8-TCDD- enriched local soil to the dioxin content of the local atmosphere. To confirm these results, long -term collection of air samples is ongoing.