Background:Recent epidemiological results suggested an increase of cancer risk after receiving computed tomography (CT) scans in childhood or adolescence. Their interpretation is questioned due to the lack of information about the reasons for examination. Our objective was to estimate the cancer risk related to childhood CT scans, and examine how cancer-predisposing factors (PFs) affect assessment of the radiation-related risk.Methods:The cohort included 67 274 children who had a first scan before the age of 10 years from 2000 to 2010 in 23 French departments. Cumulative X-rays doses were estimated from radiology protocols. Cancer incidence was retrieved through the national registry of childhood cancers; PF from discharge diagnoses.Results:During a mean follow-up of 4 years, 27 cases of tumours of the central nervous system, 25 of leukaemia and 21 of lymphoma were diagnosed; 32% of them among children with PF. Specific patterns of CT exposures were observed according to PFs. Adjustment for PF reduced the excess risk estimates related to cumulative doses from CT scans. No significant excess risk was observed in relation to CT exposures.Conclusions:This study suggests that the indication for examinations, whether suspected cancer or PF management, should be considered to avoid overestimation of the cancer risks associated with CT scans.

The analyses in the extended follow-up strengthen the results previously observed among French uranium miners about their excess risk of mortality and its association with their occupational IR exposure.

This is the first combined analysis of major French cohorts of nuclear workers. Results were consistent with risks estimated in other nuclear worker cohorts and illustrate the potential of a further joint international study to yield direct risk estimates in support to radiation protection standards.

Objectives: The increasing use of CT scans in the paediatric population raises the question of a possible health impact of ionising radiation exposure associated with CT scans. The aim of this study was to describe the pattern of CT use in early childhood. Methods: In 14 major French paediatric radiology departments, children undergoing at least 1 CT scan before age 5, between 2000 and 2006, were included. For each examination, absorbed organ doses were calculated. Results: 43% of the 27 362 children in the cohort were aged less than 1 year during their first exposure, with 9% being aged less than 1 month. The mean number of examinations per child was 1.6 (range 1-43). The examinations included: head in 63% of the cases, chest in 21%, abdomen and pelvis in 8% and others in 8%. Brain and eye lenses received the highest cumulative doses from head examinations, with mean organ dose values of 22 mGy (maximum 1107 mGy) and 26 mGy (maximum 1392 mGy), respectively. The mean cumulative effective dose was 3.2 mSv (range 0.1-189 mSv). Conclusion: CT scan exposure in childhood is responsible for relatively high doses to radiosensitive organs. The rather large dose range according to the protocols used requires their optimisation. The cohort follow-up will study the risk of long-term radiation-induced cancer.

After the extension of the French cohort of uranium miners with the inclusion of workers employed in the Jouac mines, this article seeks to describe the new Jouac cohort and to estimate mortality risks, as well as to quantify their relation to radon exposure in this extended cohort. The Jouac cohort includes 458 miners hired by the Société des Mines de Jouac between 1957 and 2001. There is no measurement of radon exposure before 1978 and so no data were available. Consequently, only the post-1977 Jouac cohort (n = 314) has been included in the French cohort, creating an extended cohort of 5400 French uranium miners followed up from 1946 to 2007. Mortality analyses computed the standardised mortality ratios (SMRs). Excess relative risks (ERRs) were assessed using Poisson regression models. No evidence of a significant excess risk of overall mortality (n = 66, SMR = 0.93; 95% CI = 0.72-1.19) or any specific mortality was observed in the Jouac cohort. In the extended cohort, overall mortality did not increase, but a significant excess of deaths was observed for all cancers (SMR = 1.11, 95% CI = 1.03-1.19), lung cancer (SMR = 1.32, 95% CI = 1.14-1.51), and kidney cancer (SMR = 1.58, 95% CI = 1.01-2.35). Cumulative exposure to radon was 3.9 working level month (WLM) and 35.1 WLM in the post-1977 Jouac and extended cohorts, respectively. Cumulative radon exposure was significantly associated with an excess risk of death from lung cancer (ERR/100 WLM = 0.73, 95% CI = 0.32-1.33) and from cerebrovascular diseases (ERR/100 WLM = 0.42 95% CI = 0.04-1.04). In conclusion, the Jouac cohort is still a young cohort and its inclusion leads to slight modifications compared to previous analyses of the French cohort. The already known relation between radon exposure and lung cancer death as well as the excess risk of death from cerebrovascular diseases persisted in the extended cohort.

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The aim of this study was to assess the risk of lung cancer death associated with cumulative lung doses from exposure to α-particle emitters, including radon gas, radon short-lived progeny, and long-lived radionuclides, and to external γ rays among French uranium miners. The French "post-55" sub-cohort included 3,377 uranium miners hired from 1956, followed up through the end of 1999, and contributing to 89,405 person-years. Lung doses were calculated with the ICRP Human Respiratory Tract Model (Publication 66) for 3,271 exposed miners. The mean "absorbed lung dose" due to α-particle radiation was 78 mGy, and that due to the contribution from other types of radiation (γ and β-particle radiation) was 56 mGy. Radon short-lived progeny accounted for 97% of the α-particle absorbed dose. Out of the 627 deaths, the cause of death was identified for 97.4%, and 66 cases were due to lung cancer. A significant excess relative risk (ERR) of lung cancer death was associated with the total absorbed lung dose (ERR/Gy = 2.94, 95% CI 0.80, 7.53) and the α-particle absorbed dose (4.48, 95% CI 1.27, 10.89). Assuming a value of 20 for the relative biological effectiveness (RBE) of α particles for lung cancer induction, the ERR/Gy-Eq for the total weighted lung dose was 0.22 (95% CI: 0.06, 0.53).

The adverse health effects of radon on uranium miners, especially on their lungs, are well documented, but few studies have considered the effects of other radiation exposures. This study examined the mortality risks associated with exposure to radon, external γ rays and long-lived radionuclides (LLR) in the French "post-55" sub-cohort, which includes uranium miners first employed between 1956 and 1990 for whom all three types of exposure were assessed individually. Exposure-risk relationships were estimated with linear excess relative risk models and a 5-year lag time. The post-55 sub-cohort includes 3377 miners, contributing 89,405 person-years, followed up through the end of 1999 with a mean follow-up of 26.5 years. Mean cumulative exposure was 17.8 WLM for radon, 54.7 mSv for γ rays, and 1,632 Bq.m(-3).h for LLR. Among the 611 deaths observed, 66 were due to lung cancer. Annual individual exposures were significantly correlated. Increased mortality was observed for lung cancer (SMR = 1.30; 95% CI: 1.01, 1.65) and for brain and central nervous system (CNS) cancer (SMR = 2.00; 95% CI: 1.09, 3.35). Cumulative exposure to radon, γ rays and LLR was associated only with a significant risk of lung cancer. These new results could suggest an association between lung cancer and exposure to γ rays and LLR. They must nonetheless be interpreted with caution because of the correlation between the types of exposure. The calculation of organ doses received by each of these exposures would reduce the collinearity.