Background:Exposures to high-dose ionizing radiation and high-dose rate ionizing radiation are established risk factors for childhood acute leukemia (AL). The risk of AL following exposure to lower doses due to natural background radiation (NBR) has yet to be conclusively determined.Methods:AL cases diagnosed over 1990–2009 (9,056 cases) were identified and their municipality of residence at diagnosis collected by the National Registry of Childhood Cancers. The Geocap study, which included the 2,763 cases in 2002–2007 and 30,000 population controls, was used for complementary analyses. NBR exposures were modeled on a fine scale (36,326 municipalities) based on measurement campaigns and geological data. The power to detect an association between AL and dose to the red bone marrow (RBM) fitting UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) predictions was 92%, 45% and 99% for exposure to natural gamma radiation, radon and total radiation, respectively.Results:AL risk, irrespective of subtype and age group, was not associated with the exposure of municipalities to radon or gamma radiation in terms of yearly exposure at age reached, cumulative exposure or RBM dose. There was no confounding effect of census-based socio-demographic indicators, or environmental factors (road traffic, high voltage power lines, vicinity of nuclear plants) related to AL in the Geocap study.Conclusions:Our findings do not support the hypothesis that residential exposure to NBR increases the risk of AL, despite the large size of the study, fine scale exposure estimates and wide range of exposures over France. However, our results at the time of diagnosis do not rule out a slight association with gamma radiation at the time of birth, which would be more in line with the recent findings in the UK and Switzerland.Citation:Demoury C, Marquant F, Ielsch G, Goujon S, Debayle C, Faure L, Coste A, Laurent O, Guillevic J, Laurier D, Hémon D, Clavel J. 2017. Residential exposure to natural background radiation and risk of childhood acute leukemia in France, 1990–2009. Environ Health Perspect 125:714–720; http://dx.doi.org/10.1289/EHP296

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High-dose ionizing radiation is an established risk factor for childhood central nervous system tumors (CNST) but the role of low doses remains debated. In particular, there are few studies of natural background radiation (NBR, gamma radiation and radon) and childhood CNST, and their results are inconclusive. This study aimed to investigate the association between NBR exposure and childhood CNST in France, over the period 2000-2012, based on data from the French national registry of childhood cancers. 5,471 childhood CNST cases, and their municipality of residence at diagnosis, were recorded, and municipality NBR exposures were estimated by cockriging models, using NBR measurements and additional geographic data. The standardized incidence ratios (SIR) per unit variation of exposure were estimated with Poisson log-linear regression models. NBR exposures were considered at the time of diagnosis, and cumulatively from birth to diagnosis. In an exploratory analysis, the cumulative brain dose due to NBR was used. Overall, there was no significant association between NBR exposure and childhood CNST, but an association was suggested for pilocytic astrocytomas with NBR levels at diagnosis: SIR = 1.12 (1.00,1.25) per 50 nSv/h for gamma radiation, and SIR = 1.15 (1.01,1.32) per 100 Bq/m3 for radon). Upward trends for this subtype were also suggested with the cumulative exposures to gamma radiation and radon separately. The results for the total brain dose were similar to those for the cumulative exposure to gamma radiation. Adjustment for socio-demographic factors did not change the findings. Conclusions: Our study was based on high quality incidence data, large numbers of CNST cases, and validated models of assessment of NBR exposures. However, we could not disentangle the possible role of each type of radiation in the association with pilocytic astrocytomas, even though gamma radiation may be more implicated than radon, given its physical properties.