Evaluation of the risks incurred by the public residing in the proximity of an area contaminated with radium 226 Saint Nicolas d'Aliermont
Pierre VERGER, A. DELORAINE, F. MANSOTTE, Philippe HUBERT
1998 Annual Conference (Risk analysis : opening the process) Paris, 11-14/10/1998, Vol 1, p. 547-557
In 1992, the social and sanitary services of the "département" Seine maritime requested and financed an evaluation of the risks incurred by the public residing in the vicinity of a former dial factory, at Saint Nicolas d'Aliermont. This request followed the detection of elevated levels of radioactivity on the factory site and on a nearby building-site, due to contamination with radium 226. Radium 226 is an alpha emitter that concentrates in bone after incorporation. Its main decay products, from the point of view of internal contamination, are radon 222, a radioactive gas, polonium 210 and lead 210. Paint containing radium 226 was used in the dial industry during the first half century. Excess risks of bone sarcomas and head carcinomas occuring many years later have been demonstrated in female radium dial workers. During the 1960s and 1970s, radium was replaced by tritium, which is less radiotoxic. The dial factory, which closed in 1989, had used paint containing radium 226 from 1945 to 1970. The factory was located on two different sites, some parcels of which were sold in1981 and 1988 and on which dwellings were built. In 1992, approximately 160 persons including 70 children lived in these homes. Interviewing several inhabitants and former workers revealed that children had played on one of the sites where radioactive wastes (contaminated paints, dials, etc.) had been deposited or buried. Various environmental measurements carried out in 1993 and 1994 showed several hot spots scattered on both sites of the factory. Dose rates reaching 50 to 100 times the natural background were measured, and significant concentrations of radium 226 were found in several soil samples. Due to the limited number of measurements and to the lack of individual retrospective information on exposure of the residents, two exposure scenarios were distinguished : one pessimistic taking into account the highest measures of radioactivity and the other, more moderate. The evaluation, carried out for an adult and a 5 year-old child, took into account the various possible exposure pathways (external radiation, ingestion of contaminated food and soil, dust inhalation). Information on lifestyle was sought from the scientific literature when possible (e.g., food consumption, soil ingestion), but assumptions also had to be made, for example, to quantify the time spent outdoors or the amount of home-produced food consumed. Results of the quantification are presented, relative to spontaneous rates, for all cancers and specific organs (lung, bone and bone marrow) and are discussed in the light of the various assumptions for the quantification. The relevance of an epidemiological follow-up of the residents is also discussed.