Methodology and results of the Nord-Cotentin radioecologicalstudy

Abstract

Epidemiological studies have shown a trend towards an excess number ofleukaemia cases in the region of Nord-Cotentin (France) where, in particular,the La Hague nuclear reprocessing plant is located. In 1997, it was suggestedthat the risk of leukaemia was associated with some aspects of lifestyle, inparticular, the consumption of local seafood and use of local beaches. Torespond to public concern, the French Ministries of the Environment and Healthdecided to commission complementary epidemiological studies and a detailedradioecological analysis. The radioecological study was entrusted to a groupof experts with various backgrounds (inspectors, governmental experts,operators, experts from non-governmental laboratories and foreignexperts) - the Nord-Cotentin Radioecology Group. Its principal objective wasto assess realistically the exposure to ionising radiation of young peoplefrom 0 to 24 years of age who had lived near the La Hague nuclear reprocessingplant and to estimate their risk of radiation-induced leukaemia from 1978through 1996, the period covered by the epidemiological studies. The Groupchose to use a three-stage approach: reconstruction of the population of youngpeople from 0 to 24 years who resided in the region between 1978 and 1996,assessment of their exposure to all sources of ionising radiation, andestimation of the risk of radiation-induced leukaemia attributable to thisexposure. The collective red bone marrow dose due to the discharges from thelocal nuclear facilities from Nord-Cotentin has thus been estimated atapproximately 0.5 man-Sv, which is less than 0.2% of the total exposure toionising radiation, including natural and medical sources and fallout fromatmospheric testing and the accident at Chernobyl. The number of cases ofradiation-induced leukaemia attributable to discharges from the local nuclearfacilities based on the estimated level of exposure was around 0.002 over thisperiod. This is the best estimate, in the current state of knowledge, of theincidence of radiation-induced leukaemia attributable to environmentalexposure to ionising radiation among the young people living in the vicinityof the La Hague reprocessing plant based on mean habits for the population.This estimate must be interpreted in the light of the limitations inherent inthe risk assessment process, and some participants in the Nord-CotentinRadioecology Group have expressed reservations about it. Nonetheless, thenumber of cases estimated here is low in comparison to the four cases ofleukaemia observed during the same period. It is thus very improbable thatexposure attributable to local nuclear facilities is implicated to any salientdegree in the elevated incidence of leukaemia observed in this region amongyoung people.