Arsenic contamination assessment 40 years after an industrial disaster: measurements and deposition modeling

On 26 September 1976 in Manfredonia (Italy), a mixture containing arsenic (As) compounds was released into the atmosphere due to an accident in a petrochemical plant. The aim of this work is reconstructing the extent of As contamination within the framework of an epidemiological study including both workers of the plant and residents in Manfredonia. Emission consisted of two fractions. One was a liquid solution mixed together with a solid material that hits the area of the plant and mainly affected the workers. The second fraction consisted of a cloud that was dispersed and transported by the wind beyond the plant area. Contamination within the plant has been accounted for using deposition data collected after the accident. Contamination outside the plant has been determined using a dispersion model. A comparison between predictions and measurements confirms that maximum contamination occurred 1.7 km away from the plant, but the area affected by the fallout was larger than it was supposed to be in the days following the accident. Providing a gradient in the contamination, predicted deposition maps are a relevant tool in the population exposure assessment, even if some uncertainty remains regarding establishing possible exposure routes via the food chain.