Uranium carcinogenicity in humans might depend on the physical and chemical nature of uranium and its isotopic composition: results from pilot epidemiological study of French nuclear workers.

OBJECTIVE: To study the cancer risk related to protracted, low-dose exposure to different industrial uranium compounds, paying attention to their isotopic composition and solubility. METHODS: Two thousand and ninety-seven workers employed at the AREVA NC uranium processing plant (France) were followed up for mortality from 1960 to 2006. Historical exposure to uranium and other carcinogenic chemical and physical pollutants was assessed on the basis of the plant-specific job-exposure matrix. For each type of uranium, Cox regression models stratified on sex and calendar period, and adjusted for socioeconomic status and potentially confounding co-exposures were used to estimate hazard ratios (HRs) for mortality from lung cancer (53 deaths) and lymphatic and hematopoietic tissue malignancies (21 deaths). RESULTS: We observed that exposure to reprocessed uranium entails increasing risks of mortality from lung cancer and lymphatic and hematopoietic malignancies (the most significant HR being respectively 1.14 (95% CI: 1.00-1.31) and 1.20 (95% CI: 1.01-1.43) per unit of a time-lagged log-transformed continuous exposure scores), and that the HRs tend to increase with decreasing solubility of the compounds. CONCLUSION: Our results suggest that uranium carcinogenicity may depend on isotopic composition and solubility of uranium compounds. This study is the first to show the carcinogenic effect of slowly soluble reprocessed uranium on two uranium target organs. This finding is consistent with data from epidemiological and experimental studies on similar compounds but need to be confirmed in the more powerful dose-response analysis.

[Low doses of ionizing radiation and risk of cardiovascular disease: A review of epidemiological studies]. / Irradiations à faibles doses et risque de pathologie cardiovasculaire : revue des études épidémiologiques.

BACKGROUND: While cardiovascular risks associated with high level of ionizing radiation are well-established, long-term effects of low and medium levels of exposure, between 0 and 5 gray (Gy), on the cardiovascular system are debated. METHODS: Available literature was reviewed considering various populations, such as survivors of atomic bombs, nuclear workers, Chernobyl liquidators, radiologists and radiological technologists and patients exposed for medical reasons. RESULTS: A significant increased risk of cardiovascular diseases associated with low doses of ionizing radiation was observed in 13 studies among the 27 analyzed. The ischemic heart diseases risk was detailed in 16 studies and seven of them showed a significant increase. The cerebrovascular risk was significantly increased in five studies among the 12 considered. CONCLUSION: Some epidemiological and experimental data are clearly in favour of an increased cardiovascular risk associated with exposure to low doses. However, given the multifactorial origin of cardiovascular diseases and the lack of a clear pathophysiologic mechanism, epidemiological results have to be carefully interpreted. Further research should be conducted in this area.

[Mortality in nuclear workers of the French electricity company: period 1968-2003]. / Cohorte des travailleurs du nucléaire à Electricité de France: mortalité des agents statutaires sur la période 1968-2003.

BACKGROUND: We conducted a mortality study on a cohort of French nuclear workers employed at Electricité de France (EDF). A first cancer mortality analysis had covered the period 1968-1994. This paper presents results from a mortality analysis including nine additional years of follow-up to cover workers employed from 1968 to 2003. METHODS: The cohort includes 22393 workers, 97% of whom are males. Employment data were updated using the EDF personnel file. Vital status was ascertained using the French National Registry of Population, and further completed using EDF personnel and pension files. Causes of death were obtained from the National registry of causes of death. Standardised Mortality Ratios (SMR) were computed using national rates as references. Variations of all causes and all cancers SMRs were studied according to demographic and occupational characteristics. RESULTS: At the study end point (31/12/2003), 74% of workers are still in active employment. Only 0.3% of workers are lost to follow-up. The median duration of follow-up is 20 years. Causes are ascertained for 96% of deaths. The total number of deaths is 874, 307 of which are cancer deaths. SMRs for all causes and cancers show a significant deficit compared to the French national mortality. No significant excess was observed for any of the cancer sites studied. Non-significant excesses are observed for pancreatic, pleural, kidney and brain cancer. Significant variations of all causes SMRs according to age at study entry and attained age are observed. Significant variations of all causes and all cancers SMRs according to diploma at employment are observed, with a reduced SMR for a higher level of diploma. CONCLUSION: There is a significant deficit of mortality compared to the general population, reflecting a strong Healthy Worker Effect. Although nine years of follow-up were added, this cohort is made up of young workers, most of whom are still in active service. Regular updating of the follow up of this cohort is planned, aiming for an occupational health surveillance of workers occupationally exposed to ionizing radiation in France.

Mortality risk in the French cohort of uranium miners: extended follow-up 1946-1999.

OBJECTIVES: This paper presents the risk of death from lung cancer and from other causes of death for the French cohort of uranium miners through 1999 and estimates associations with radon exposure. METHODS: The cohort includes men employed as uranium miners for at least 1 year between 1946 and 1990. For each miner, vital status and cause of death were obtained from the national registry, and radon exposure was reconstructed for each year. Standardised mortality ratios were computed with national mortality rates as references. Exposure-risk relationships were estimated by Poisson regression, with a linear excess relative risk (ERR) model and a 5-year lag. RESULTS: The cohort included 5086 miners and 153 063 person-years of exposure. The mean duration of follow-up was 30.1 years. In all 4140 miners exposed to radon, the average cumulative exposure was 36.6 working level months (WLM). There were 1411 deaths of miners <85 years of age. The miners did not differ significantly in overall mortality from the general male population. The analysis confirmed an excess risk of lung cancer death (n = 159; SMR = 1.43; 95% CI: 1.22 to 1.68), which increased significantly with cumulative radon exposure (ERR per 100 WLM = 0.71; 95% CI: 0.29 to 1.35). The ERR per unit exposure was much higher after 1955, when the accuracy of exposure measurement improved substantially (ERR per 100 WLM = 2.00; 95% CI: 0.91 to 3.65). A significant excess of kidney cancer deaths was observed (n = 20; SMR = 2.0; 95% CI: 1.22 to 3.09), which was not associated with cumulative radon exposure. No excess was observed for other causes of death, except silicosis (n = 23; SMR = 7.12; 95% CI: 4.51 to 10.69). CONCLUSIONS: The analysis confirmed the excess risk of death from lung cancer associated with low radon exposure. An excess risk of death from kidney cancer was also observed, apparently not associated with cumulative radon exposure.

[Development of a job exposure matrix for the epidemiological follow-up of workers in the French nuclear industry]. / Construction d'une matrice emplois--expositions pour le suivi épidémiologique des travailleurs de l'industrie nucléaire en France. Résultats d'une étude pilote.

BACKGROUND: A pilot study was carried out in the AREVA NC Pierrelatte nuclear facility in order to investigate a possible carcinogenic effect of internal radiation exposure among nuclear workers in France. The objective of this study was to develop a method for retrospective reconstruction of the occupational exposure to internal radiation from uranium and associated chemical exposures. METHODS: A plant- and period-specific job exposure matrix (JEM) was designed. Job groups and exposure agents groups including uranium compounds and other chemical agents known as being carcinogenic, mutagenic or toxic were defined by an expert committee. Exposure was evaluated by active and retired workers included in the evaluator committee. A quantitative assignment of quantity and frequency of handling (both coded from 0 to 3) was performed for each agent groups using a method derived from the Delphi technique. RESULTS: In all, 23 experts and 353 evaluators participated to the JEM elaboration. A final JEM involved 232 "job-periods" presenting throughout the plant period 1960-2006 and 22 exposure agents groups in use at the plant. Six of them involved uranium compounds classified by their blood-transferability and toxicity characteristics. A first validation of the JEM by experts in radiological protection and industrial hygiene showed an acceptable internal consistency. CONCLUSION: In the context of missing past exposure measurement data, the plant- and period-specific job exposure matrices may be considered as a valid alternative for exposure estimation. This method may be applied to other nuclear plants and offers allowance to investigate a possible carcinogenic effect of internal radiation exposure among nuclear workers.

Dose conversion of radon exposure according to new epidemiological findings.

In 1993, ICRP-65 recommended that dose conversion of radon exposure should be based on the comparison of detriments between radon exposure and effective dose. The lifetime detriment from the radon exposure was projected according to the epidemiological studies of uranium miners then available. The projection model (GSF) was multiplicative with temporal and age-at-exposure modification. Since 1993, new studies of uranium miners have appeared and many original studies were updated. In addition, projections of the risk have been improved by including further modifying factors as for instance in BEIR VI. New analyses were completed in the Czech and French studies of uranium miners with accurate estimates of exposures based on extensive radon measurements. The resulting estimates of excess absolute lifetime risk per unit exposure in working level months (WLM) from these models lead to dose conversion of 10 mSv WLM(-1) for the BEIR VI model and 8 mSv WLM(-1) for the joint Czech-French model in contrast to the conversion of 5 mSv WLM(-1) for the GSF model.

Cancer risk following alpha-emitter exposure.

The International Commission on Radiological Protection (ICRP) mandated a task group (Task Group 64) to review recently published epidemiological studies related to cancer risk and incorporated alpha emitters, and to evaluate whether the results might consolidate or challenge assumptions underlying the current radiation protection system. Three major alpha emitters were considered: radon and its decay products, plutonium, and uranium. Results came mainly from cohorts of workers, while for radon, major studies of the general population contributed to a better understanding of the risk of lung cancer at low and chronic exposure. Selection criteria for the review were: assessment of individual exposure of the target organ, long duration of the health survey, availability of attained age at end of follow-up, and adjustment for major co-factors. Task Group 64 is composed of members from ICRP Committees 1 and 2 (because epidemiological and dosimetric expertise were needed) and external experts. A first report (ICRP Publication 115) considered the risk of lung cancer related to inhalation of radon and its decay products. As the estimated excess risk per unit of exposure was higher by a factor of 2 compared with a previous ICRP estimate in 1993, Task Group 64 suggested a reconsideration of the reference levels for the workplace and for the general population. A second report, using the same standardised methodology (lung cancer baselines, population, life expectancy), will include estimation of the cancer risk of nuclear workers exposed to plutonium, focusing on the risk of lung cancer. A comparison of these risks with those of populations exposed to external gamma radiation alone will be made in the near future. For uranium, the results related to the organ-specific dose were too sparse to draw reliable conclusions, despite a recent publication. More research is needed on this topic.

The mandate and work of ICRP Committee 1 on radiation effects.

The aim of the International Commission on Radiological Protection (ICRP) is to protect humans against cancer and other diseases and effects associated with exposure to ionising radiation, and also to protect the environment, without unduly limiting the beneficial use of ionising radiation. As of the second half of 2017, four committees are contributing to the overall mission of ICRP, including Committee 1 (Radiation Effects). The role of Committee 1 includes consideration of the risks and mechanisms of induction of cancer and heritable disease; discussion of the risks, severity, and mechanisms of induction of tissue/organ damage and developmental defects; and review of the effects of ionising radiation on non-human biota at population level. This paper gives an overview of the recent activities of Committee 1, and discusses the focus of its active task groups.

External radiation exposure and mortality in a cohort of French nuclear workers.

OBJECTIVE: To analyse the effect of external radiation exposure on the mortality of French nuclear workers. METHODS: A cohort of 29 204 workers employed between 1950 and 1994 at the French Atomic Energy Commission (Commissariat à l'Energie Atomique (CEA)) or at the General Company of Nuclear Fuel (COmpagnie GEnérale des MAtières nucléaires (Cogema, now Areva NC)) was followed up for an average of 17.8 years. Standardised mortality ratios (SMRs) were computed with reference to French mortality rates. Dose-effect relationship were analysed through trend tests and Poisson regression, with linear and log-linear models. RESULTS: The mean exposure to X and gamma radiation was 8.3 mSv (16.9 mSv for exposed worker population). A total of 1842 deaths occurred between 1968 and 1994. A healthy worker effect was observed, the number of deaths in the cohort being 59% of the number expected from national mortality statistics. Among the 21 main cancer sites studied, a statistically significant excess was observed only for skin melanoma, and an excess of borderline statistical significance was observed for multiple myeloma. A dose-effect relationship was observed for leukaemia after exclusion of chronic lymphoid leukaemia (CLL). The relative risk observed for non-CLL leukaemia, n = 20, was 4.1 per 100 mSv (90% CI 1.4 to 12.2), linear model and 2.2 per 100 mSv (90% CI 1.2 to 3.3), log-linear model. Significant dose-effect relationship were also observed for causes of deaths associated with alcohol consumption: mouth and pharynx cancer, cirrhosis and alcoholic psychosis and external causes of death. CONCLUSION: The risk of leukaemia increases with increasing exposure to external radiation; this is consistent with published results on other nuclear workers cohorts.

Lung cancer and use of cigarettes: a French case-control study.

A case-control study of 1,625 cases and 3,091 controls was conducted in France from 1976 to 1980 to compare the effects of different smoking habits, especially the use of filter cigarettes, tobacco types (light or dark), and the use of hand-rolled or manufactured cigarettes on the occurrence of lung cancer. All cases had histologically confirmed lung cancer; the controls were matched by sex, age, hospital of admission, and interviewer. The reported results concern only male nonsmokers and males who smoked (or had smoked) cigarettes exclusively, i.e., a total of 1,217 Kreyberg I and Kreyberg II cancer cases and 1,915 controls. Cigarette smoking was associated with both Kreyberg I and Kreyberg II cell categories although with different relative risks (RR) (17.2 and 3.6, resp.). Within the Kreyberg I category, RR were significantly increased (P less than .0001) with certain indices of duration and intensity of cigarette exposure, such as early age at first cigarette smoked, daily consumption, depth of inhalation, and duration of smoking. A significant difference in risk was found within the Kreyberg I category for nonfilter versus filter cigarette smokers (RR = 18.1 and 10.9, resp.) and dark versus light tobacco smokers (RR = 18.1 and 4.9, resp.) but not for hand-rolled versus manufactured cigarette smokers (RR = 19.8 and 16.0, resp.). When all the covariates were taken into account in a matched logistic regression, lung cancer risks for nonfilter versus filter cigarette smokers was RR = 1.23, for hand-rolled versus manufactured cigarette users RR = 1.22, and for dark versus light tobacco users RR = 1.94.

Radon and cancers other than lung cancer in underground miners: a collaborative analysis of 11 studies.

BACKGROUND: Exposure to the radioactive gas radon and its progeny (222Rn and its radioactive decay products) has recently been linked to a variety of cancers other than lung cancer in geographic correlation studies of domestic radon exposure and in individual cohorts of occupationally exposed miners. PURPOSE: This study was designed to characterize further the risks for cancers other than lung cancer (i.e., non-lung cancers) from atmospheric radon. METHODS: Mortality from non-lung cancer was examined in a collaborative analysis of data from 11 cohorts of underground miners in which radon-related excesses of lung cancer had been established. The study included 64,209 men who were employed in the mines for 6.4 years on average, received average cumulative exposures of 155 working-level months (WLM), and were followed for 16.9 years on average. RESULTS: For all non-lung cancers combined, mortality was close to that expected from mortality rates in the areas surrounding the mines (ratio of observed to expected deaths [O/E] = 1.01; 95% confidence interval [CI] = 0.95-1.07, based on 1179 deaths), and mortality did not increase with increasing cumulative exposure. Among 28 individual cancer categories, statistically significant increases in mortality for cancers of the stomach (O/E = 1.33; 95% CI = 1.16-1.52) and liver (O/E = 1.73; 95% CI = 1.29-2.28) and statistically significant decreases for cancers of the tongue and mouth (O/E = 0.52; 95% CI = 0.26-0.93), pharynx (O/E = 0.35; 95% CI = 0.16-0.66), and colon (O/E = 0.77; 95% CI = 0.63-0.95) were observed. For leukemia, mortality was increased in the period less than 10 years since starting work (O/E = 1.93; 95% CI = 1.19-2.95) but not subsequently. For none of these diseases was mortality significantly related to cumulative exposure. Among the remaining individual categories of non-lung cancer, mortality was related to cumulative exposure only for cancer of the pancreas (excess relative risk per WLM = 0.07%; 95% CI = 0.01-0.12) and, in the period less than 10 years since the start of employment, for other and unspecified cancers (excess relative risk per WLM = 0.22%; 95% CI = 0.08-0.37). CONCLUSIONS: The increases in mortality from stomach and liver cancers and leukemia are unlikely to have been caused by radon, since they are unrelated to cumulative exposure. The association between cumulative exposure and pancreatic cancer seems likely to be a chance finding, while the association between cumulative exposure and other and unspecified cancers was caused by deaths certified as due to carcinomatosis (widespread disseminated cancer throughout the body) that were likely to have been due to lung cancers. This study, therefore, provides considerable evidence that high concentrations of radon in air do not cause a material risk of mortality from cancers other than lung cancer. IMPLICATIONS: Protection standards for radon should continue to be based on consideration of the lung cancer risk alone.

Ecological association between indoor radon concentration and childhood leukaemia incidence in France, 1990-1998.

The objective of this study was to evaluate the ecological association between indoor radon concentration and acute leukaemia incidence among children under 15 years of age in the 348 geographical units (zones d'emploi, ZE) of France between 1990 and 1998. During that period, 4015 cases were registered by the French National Registry of Childhood Leukaemia and Lymphoma. Exposure assessment was based on a campaign of 13 240 measurements covering the whole country. The arithmetic mean radon concentration was 85 Bq/m (range, 15-387 Bq/m) and the geometric mean, 59 Bq/m (range: 13-228 Bq/m). A positive ecological association, on the borderline of statistical significance (P=0.053), was observed between indoor radon concentration and childhood leukaemia incidence. The association was highly significant for acute myeloid leukaemia (AML) (P=0.004) but not for acute lymphocytic leukaemia (ALL) (P=0.49). The standardized incidence ratio (SIR) increased by 7, 3 and 24% for all acute leukaemia, ALL and AML, respectively, when radon concentration increased by 100 Bq/m. In conclusion, the present ecological study supports the hypothesis of a moderate association between indoor radon concentration and childhood acute myeloid leukaemia. It is consistent with most previous ecological studies. Since the association is moderate, this result does not appear inconsistent with the five published case-control studies, most of which found no significant association.

French population exposure to radon, terrestrial gamma and cosmic rays.

In France, natural sources account for most of the population exposure to ionising radiation. This exposure varies widely with area. Radon and gamma-ray exposure data come from national measurement campaigns; cosmic doses were calculated from city altitude. These data were corrected for season of measurement, housing characteristics and population density to study their relationship with health indicators. The crude average of indoor radon concentrations was 89 Bq m(-3), and the average corrected for season and housing characteristics was 83 Bq m(-3) (range over districts: 19-297). Weighting by district population density yielded a national average of 63 Bq m(-3). Gamma-ray dose rates averaged 55 nSv h(-1) (23-96) indoors and 46 nSv h(-1) (25-85) outdoors; corrections did not change the means. Corrected cosmic annual doses averaged 0.28 mSv (0.27-0.38). These corrections estimated the radiation exposure of the French population more accurately and represented its distribution well, thereby allowing its study as a cofactor in ecological studies.

[Radiation doses received by premature babies in the neonatal intensive care unit]. / Doses d'irradiation reçues par les prématurés en service de réanimation.

PURPOSE: Because of frequent radiological investigations performed in neonatal intensive care unit, a dosimetry study was carried out to assess the level of doses received by premature babies. MATERIALS AND METHODS: In vivo measurements were performed and effective doses were evaluated for single radiographs. Individual cumulative doses received over the period of stay were then estimated, for each premature baby entering the intensive care unit in 2002, taking into account the number of radiographs they underwent. RESULTS: On average, babies stayed for a week and more than one radiograph was taken per day. Results showed that, even if average doses per radiograph were relatively low (25 microSV), cumulative doses strongly depended on the length of stay, and can reach a few mSv. CONCLUSION: Even if doses per radiograph are in agreement with European recommendations, optimisation of doses is particularly important because premature babies are more sensitive to radiation than adults and because they usually undergo further radiological examinations in other services. On the basis of the results of this dosimetry study, the implementation of a larger study is being discussed.

[Indoor radon exposure and lung cancer risk. Results of an epidemiological study carried out in France]. / Exposition domestique au radon et risque de cancer du poumon.

INTRODUCTION: Several epidemiological studies have indicated an increased risk of lung cancer associated with indoor radon exposure. As part of a large European project, a hospital based case-control study was carried out in four regions of France: Auvergne, Brittany, Languedoc-Roussillon and Limousin. MATERIAL AND METHODS: Individual data on demographic characteristics, residential history, smoking and occupational exposures were collected during face-to-face interviews. Radon concentrations were measured in each dwelling occupied by the subject during the 30-year period prior to the interview. RESULTS: 486 cases and 984 controls were included in the study. After adjustment for age, sex, region, smoking history and occupational exposure, the risk of lung cancer increased by 4% per 100 Bq/m(3), when considering cumulative exposure in the 30 years prior to diagnosis. CONCLUSION: The study indicates a positive association between lung cancer risk and indoor radon exposure. The risk estimate per unit of exposure is in agreement with other recently published indoor case-control studies.

Estimating lung cancer mortality from residential radon using data for low exposures of miners.

Some recent estimates of lung cancer risk from exposure to radon progeny in homes have been based on models developed from a pooled analysis of 11 cohorts of underground miners exposed to radon. While some miners were exposed to over 10,000 working level months (WLM), mean exposure among exposed miners was 162 WLM, about 10 times the exposure from lifetime residence in an average house and about three times the exposure from lifetime residence at the "action level" suggested by the U.S. Environmental Protection Agency. The extrapolation of lung cancer risk from the higher exposures in the miners to the generally lower exposures in the home is a substantial source of uncertainty in the assessment of the risk of indoor radon. Using the pooled data for the miners, analyses of lung cancer risk were carried out on data restricted to lower exposures, either <50 WLM or <100 WLM. In the pooled data, there were 115 lung cancer cases among workers with no occupational WLM exposure and 2,674 among exposed miners, with 353 and 562 lung cancer cases in miners with <50 WLM and <100 WLM, respectively. Relative risks (RRs) for categories of WLM based on deciles exhibited a statistically significant increasing trend with exposure in each of the restricted data sets. In the restricted data, there was little evidence of departures from a linear excess relative risk model in cumulative exposure, although power to assess alternative exposure-response trends was limited. The general patterns of declining excess RR per WLM with attained age, time since exposure and exposure rate seen in the unrestricted data were similar to the patterns found in the restricted data. Risk models based on the unrestricted data for miners provided an excellent fit to the restricted data, suggesting substantial internal validity in the projection of risk from miners with high exposures to those with low exposures. Estimates of attributable risk for lung cancer (10-14%) in the U.S. from residential radon based on models from the unrestricted data were similar to estimates based on the data for miners receiving low exposures.

[Radon and cancer risk: epidemiological studies after occupational or domestic exposure]. / Radon et risque de cancer: études épidémiologiques après exposition professionnelle ou domestique.

The evaluation of cancer risk after exposure to radon is mainly based on the results of uranium miners follow-up. A cohort study on the French uranium miners has demonstrated an excess of lung cancer and of larynx cancer mortality. A linear dose-response relationship has been described between the excess relative risk of lung cancer and the cumulative exposure to radon (poisson regression). This study has contributed to a joint analysis of 11 cohorts of miners, the aim being a more precise evaluation of the different factors able to influence the dose-response relationship between radon and lung cancer mortality. These factors are: age at first exposure, attained age, time since exposure, the pattern of exposure over time and tobacco consumption. The extrapolation of the risk for the general public from the risk estimated after occupational exposure, has to be considered by taking in account several remarks: uranium miners are exposed, beside radon, to two other radiological components, gamma rays and long lived uranium dust, and to other substances specific of the mines, which are absent in the domestic environment but may with radon have an effect on the lung cancer risk. It was impossible to estimate directly, from these uranium miners data, the risk linked to radon for non-smokers and for female population. A case control-study is currently be carrying out in the French hospitals, in order to estimate the risk of lung cancer linked to the last 30 years of radon exposure in the dwellings.

[Indoor radon exposure and lung cancer risk: a review of case-control studies]. / Exposition domestique au radon et risque de cancer du poumon: bilan des études cas-témoins.

BACKGROUND: Radon is a radioactive gas that tends to accumulate in indoor environment. A causal relationship between lung cancer and radon exposure has been demonstrated in epidemiologic studies of miners. The objective of this paper is to present the results of case-control studies of lung cancer risk associated with indoor radon exposure. METHODS: Case-control studies published since 1990 are included in this review. This type of protocol is particularly well suited for studying the relationship between indoor radon exposure and lung cancer risk, taking into account possible confounding factors such as tobacco smoking. The characteristics and results of these studies are summarized. The limitations associated with each of these studies are also discussed. RESULTS: The results of available studies are relatively concordant and suggest a positive association between lung cancer risk and indoor radon exposure with an estimated excess relative risk of about 6 to 9% per 100Bq/m3 increase in the observed time-weighted average radon concentration. The order of magnitude of this estimation agrees with extrapolations from miners but some studies may suffer from inadequate statistical power. CONCLUSION: At present, efforts are underway to pool together the data from the existing studies of indoor radon. This pooling analysis with thousands of cases and controls will provide a more precise estimate of the lung cancer risk from indoor radon exposure and explore the effect of modifying factors, such as smoking.

[Uranium exposure and cancer risk: a review of epidemiological studies]. / Exposition à l'uranium et risque de cancer: une revue des études épidémiologiques.

OBJECTIVE: At the end of 2000, certain diseases including leukemia were reported among soldiers who participated in the Balkan and in the Gulf wars. Depleted uranium used during these conflicts was considered as a possible cause. Its radiotoxicity is close to that of natural uranium. This paper reviews the epidemiological knowledge of uranium, the means of exposure and the associated risk of cancer. METHODS: The only available epidemiological data concerns nuclear workers exposed to uranium. A review of the international literature is proposed by distinguishing between uranium miners and other workers of the nuclear industry. French studies are described in details. RESULTS: In ionizing radiation epidemiology, contamination by uranium is often cited as a risk factor, but the dose-effect relationship is rarely studied. Retrospective assessment of individual exposure is generally insufficient. Moreover, it is difficult to distinguish between uranium radiotoxicity, its chemical toxicity and the radiotoxicity of its progeny. A causal relation between lung cancer and radon exposure, a gas derived from the decay of uranium, has been demonstrated in epidemiological studies of miners. Among other nuclear workers exposed to uranium, there is a mortality deficit from all causes (healthy worker effect). No cancer site appears systematically in excess compared to the national population; very few studies describe a dose-response relationship. CONCLUSION: Only studies with a precise reconstruction of doses and sufficient numbers of workers will allow a better assessment of risks associated with uranium exposure at levels encountered in industry or during conflicts using depleted uranium weapons.