MODELLING EXPOSURE TO THE INDUSTRIAL ACCIDENTAL RELEASE OF ARSENIC OCCURRED AT MANFREDONIA (ITALY) IN 1976: LESSONS LEARNED

On September 26th 1976 in Manfredonia (Italy), a mixture containing arsenic compounds was released into the atmosphere due to an accident in a fertilizer production plant. 39 years later, the municipality promoted an epidemiological study to investigate possible long-term health effects in the population. Aim of this work is to reconstruct dispersion of the cloud to estimate population exposure to the arsenic release. A participatory research approach was implemented with a group of citizens which supported every phase of the research, providing data and information on the event and territory. Cloud dispersion was simulated with the RAMS/CALMET/CALPUFF modeling system. Meteorological measurements and arsenic deposition data in soils around the town were used to test the model inputs. The modelling system is capable to reproduce the mean flow and dispersion with some uncertainties due to the hypothesis on the release characterization. Comparison with the deposition data shows that area affected by fallout is larger than it was supposed to in the days following the accident. This is partially confirmed by arsenic deposition data collected some months after the accident. The case study confirms the need to run a dispersion model during the early phase of an accident and to collect contamination data consequently. Otherwise, the real extension of contamination can be underestimated leading to a misclassification of exposure. Participatory approach allowed a better reconstruction both of meteorology and accident dynamic