Relative Contribution of Residential and Occupational Radon Exposure to Lung Cancer Risk in Italian Bank Workers

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P-202 Introduction: Radon, a well known carcinogenic agent for humans lung, is a radioactive gas emerging essentially from soil so it represents a physical hazard for people working in underground rooms. Banks are characterised by an elevated number of underground floors and spaces, (strong-rooms, strong-box and safe-deposit rooms). The potential risk to bank workers is assessed in the present study combining occupational and residential radon exposure. Methods: Radon concentration was measured with Cr-39 dosimeters at annual and quarterly intervals in ground and underground floors of 134 bank buildings distributed among 7 regions in the North, Centre and South of Italy. Regional mean concentrations obtained in the National Residential Survey conducted by the National Institute of Health were considered as reference for residential exposure. The annual cumulative time typically spent by bank workers in underground and ground levels was estimated to be 120 hrs and 1880 hrs, respectively. The calculated cumulative annual occupational doses were compared to the corresponding residential area values. Lung cancer lifetime risk was then evaluated with a risk model (based on WHO standardization) involving a population life expectancy of 70 years, a lifetime working period between 18 and 65 years of age and a total of 2,000 working hours per year. Results: Without considering occupational exposure, maximum and minimum values of average lifetime risk were reached in the regions with respectively maximum and minimum average residential concentrations (119 and 35 Bq/m3 corresponding respectively to a lifetime risk of 14.7 · 10-3 and 4.4 · 10-3). The relative contribution of occupational exposure to overall lifetime risk was found to be proportionally high in regions with low residential concentrations, while occupational exposure may determine even a decreased overall lifetime risk in the areas with high residential concentrations. Significant absolute lifetime risk increase due to occupational exposure was only observed when very high concentrations were present at the underground levels (peak level = 2,564 Bq/m3). Consequently, organisational and technical interventions were adopted to reduce the maximum level to 500 Bq/m3, as prescribed by Italian legislation. Conclusions: The study confirmed that key determinants of occupational radon exposure for bank workers are represented by radon concentration in the premises and the work time spent in underground floors. The relative contribution of occupational exposure to individual lifetime cancer risk is also strictly dependent on the residential concentrations present in the area where the building is located.