Role of residential radon in childhood leukaemia incidence : the Geocap program

Childhood acute leukaemia (AL) etiology is still largely unknown. The main environmental exposures currently investigated are exposures to pesticides, hydrocarbon, ionizing and non ionizing radiation. The Geocap program investigates potential links between Childhood AL and several environmental exposures, among which domestic exposure to radon. The Geocap approach consists in the comparison of residential exposure of children who suffer from AL in France to contemporaneous controls who are representative of the French population under the age of 15 years. Overall, 2 760 AL cases were recorded in the Inserm French National Registry of Childhood Haematological malignancies between 2002 and 2007. A random selection procedure led to gather yearly control groups (30 000 controls over the same period). IRSN mapped with an accurate geographic resolution (500 to 1000 m) the estimated geogenic radon potential (GRP), i.e. the capacity of geological units to produce radon and to facilitate its transfer to the atmosphere. A first work aimed at validating the GRP map by comparison with a national sample of radon concentration measurements carried out in 10 843 houses by IRSN between 1982 and 2003. Mean radon concentration increased along with growing GRP and this relation persisted after adjustment for known building characteristics (e.g.: material, floor). Preliminary results demonstrate the usefulness of the GRP for prediction of home exposure to radon and the added value of contextual information for such predictions will be further explored. Studying the statistical distribution of predicted radon concentration among the 30 000 Geocap controls will provide information on children exposure to radon in France. Finally, the comparison of this distribution to that observed among the AL cases will allow documenting further the association between radon exposure and AL incidence among children.