Occupational exposure to mercury during the demolition of the Chlorine-Soda plant in the industrial area of Venice

Teresio Marchì, Laura Visentin, Maria Gregio, Luigi Mazzuia, Giancarlo Magarotto


The present study is part of the project “Control of active or decommissioned industrial sites with high environmental pollution”, financed by the Veneto Region under the “Prevention of Veneto Regional Plan 2010 - 2012” and directed by the Venice Occupational Health Unit (SPISAL). The objective was to assess the exposure to mercury during the demolition of the Chlorine-Soda plant in the industrial area of Venice and to verify the effectiveness of the prescriptions given by SPISAL regarding the risk assessment methods and the preventive strategies. The production of chlorine (Cl2) and soda (NaOH) started in Venice in 1971. The process employed the mercury cathode electrolytic cells technology (Hgo) using Sodium chloride (NaCl) as a raw material. In order to sale the area, the owners have planned its decommission, making safe the plant by emptying lines, mercury recovery, drainage, washing and flushing. Parts of the plant have been cleaned to remove the mercury residual present in a not negligible quantity especially in correspondence of junctions or irregularities of the metallic surfaces. The processing have resulted in a significant organizational and operational effort by employing a considerable amount of economic and professional resources. The decommissioning took place between October 2010 and July 2012 and involved 3 companies and 34 employees. Work activities, as well as in the production department, were held in two contiguous confined areas provided with liquid and gaseous effluents processing. During the working progress SPISAL has prescribed improvements to the assessment of exposure in different tasks, to the most effective biological monitoring, to the protection of workers. This paper describes in detail the data on workers’ exposure to Mercury which proved to be particularly high, up to exceed the limit values. Data revealed also high levels of mercury in the urine of workers, often with concentrations higher than population limit and sometimes close to the biological exposure limit. The experience demonstrates the potential hazard of decommissioning of industrial plants in the past characterized by the presence of hazardous substances in the production process. The danger calls for a special effort to prevent the staff of site security and the public audit institutions.


Mercury; chlorine-soda plant; industrial sites decommissioning; risk assessment; occupational exposure

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