Showing papers by "Margot Tirmarche published in 2006"

Residential radon and lung cancer – detailed results of a collaborative analysis of individual data on 7148 persons with lung cancer and 14 208 persons without lung cancer from 13 epidemiologic studies in Europe

Abstract: Objectives: Studies seeking direct estimates of the lung cancer risk associated with residential radon exposure lasting several decades have been conducted in many European countries. Individually these studies have not been large enough to assess moderate risks reliably. Therefore data from all 13 European studies of residential radon and lung cancer satisfying certain prespecified criteria have been brought together and analyzed. Methods: Data were available for 7148 persons with lung cancer and 14 208 controls, all with individual smoking histories and residential radon histories determined by long-term radon gas measurements. Results: The excess relative risk of lung cancer per 100 Bq/m3 increase in the observed radon concentration was 0.08 [95% confidence interval (95% CI) 0.03-0.16; P=0.0007] after control for confounding. The dose-response relationship was linear with no evidence of a threshold, and it remained significant when only persons with observed radon concentrations of <200 Bq/m3 were included. There was no evidence that the excess relative risk varied with age, sex, or smoking history. Removing the bias induced by random uncertainties related to radon exposure assessment increased the excess relative risk of lung cancer to 0.16 (95% CI 0.05-0.31) per 100 Bq/m3. With this correction, estimated risks at 0, 100, and 400 Bq/m3, relative to lifelong nonsmokers with no radon exposure, were 1.0, 1.2, and 1.6 for lifelong nonsmokers and 25.8, 29.9, and 42.3 for continuing smokers of 15-24 cigarettes/day. Conclusions: These data provide firm evidence that residential radon acts as a cause of lung cancer in the general population. They provide a solid basis for the formulation of policies with which to manage risk from radon and reduce deaths from the most common fatal cancer in Europe.

Cancer consequences of the Chernobyl accident: 20 years on

Abstract: 26 April 2006 marks the 20th anniversary of the Chernobyl accident. On this occasion, the World Health Organization (WHO), within the UN Chernobyl Forum initiative, convened an Expert Group to evaluate the health impacts of Chernobyl. This paper summarises the findings relating to cancer. A dramatic increase in the incidence of thyroid cancer has been observed among those exposed to radioactive iodines in childhood and adolescence in the most contaminated territories. Iodine deficiency may have increased the risk of developing thyroid cancer following exposure to radioactive iodines, while prolonged stable iodine supplementation in the years after exposure may reduce this risk. Although increases in rates of other cancers have been reported, much of these increases appear to be due to other factors, including improvements in registration, reporting and diagnosis. Studies are few, however, and have methodological limitations. Further, because most radiation-related solid cancers continue to occur decades after exposure and because only 20 years have passed since the accident, it is too early to evaluate the full radiological impact of the accident. Apart from the large increase in thyroid cancer incidence in young people, there are at present no clearly demonstrated radiation-related increases in cancer risk. This should not, however, be interpreted to mean that no increase has in fact occurred: based on the experience of other populations exposed to ionising radiation, a small increase in the relative risk of cancer is expected, even at the low to moderate doses received. Although it is expected that epidemiological studies will have difficulty identifying such a risk, it may nevertheless translate into a substantial number of radiation-related cancer cases in the future, given the very large number of individuals exposed.

Lung Cancer Attributable to Indoor Radon Exposure in France: Impact of the Risk Models and Uncertainty Analysis

Abstract: Radon is a chemically inert radioactive gas of natural origin, produced by the disintegration of uranium and radium located in the earth’s crust. Radon exposure, at various levels, is omnipresent for the general public. Radon inhalation is the main source of exposure to radioactivity for most people throughout the world [National Research Council’s (NRC) Committee on the Biological Effects of Ionizing Radiation (BEIR) 1999; National Council for Radiation Protection and Measurements 1984a, 1984b; U.S. Environmental Protection Agency (EPA) 2003; United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2000]. Most inhaled radon is rapidly exhaled, but the inhaled decay products—readily deposited in the lung epithelium—irradiate sensitive cells in the airways and thereby enhance the risk of lung cancer. In 1988, the International Agency for Research on Cancer (IARC) declared radon to be carcinogenic for humans (lung cancer) and classified as a group 1 carcinogen (IARC 1988), based on the results of experimental animal and epidemiologic studies, in particular among uranium miners. In 1988, the available results came from studies of high exposure levels. Extrapolation of this risk to the general population, who are exposed to lower levels in residential settings, raised numerous questions. In recent years, the average annual exposure of uranium miners has fallen to levels similar to the concentrations inhaled in some homes, and discussion today focuses on the transposition of the risk from occupational to general populations. Miners are almost all adult males, exposed in conditions different from residential exposure: they perform substantial amounts of heavy labor in an atmosphere polluted by dust and fumes. Several case-control studies of residential radon have tested the validity of this risk transposition in the past decade (Auvinen et al. 1996; Kreienbrock et al. 2001; Letourneau et al. 1994; Schoenberg et al. 1990), but lack of statistical power prevented most of them from showing a significant risk. To deal with this problem, several joint analyses have been conducted in recent years. They report a significant lung cancer risk after domestic radon exposure (Darby et al. 2005; Krewski et al. 2005; Lubin 2003). Scientists have used all of these data to assess the lung cancer risk associated with indoor radon. The principal risk assessments come from the United States, the United Kingdom, and Canada (BEIR 1999; Darby et al. 2005; Krewski et al. 2005). These studies have two principal methodologic problems. The first is related to the choice of the exposure–response relation and its use in the context of general population exposure. Past risk assessment studies generally used exposure–response relations derived from miners’ cohorts as recommended by BEIR (1990, 1999). The second methodologic problem involves the role of the uncertainty analysis in the risk assessment process. Uncertainty analysis is an essential step that is too seldom performed. The aim of this study was to assess the lung cancer risk associated with indoor radon exposure in France on the basis of French measurements and the major epidemiologic results available. Specifically, we applied several different exposure–response relations obtained from miners’ cohorts and from joint analyses of residential case-control studies to estimate the number of lung cancer deaths in 1999 that may have been associated with residential radon exposure. The analysis considers the variability of indoor radon exposure in France and allows the quantification of uncertainties related to each of the exposure–response relations.

Childhood leukemia incidence and exposure to indoor radon, terrestrial and cosmic gamma radiation.

Abstract: This study was undertaken to evaluate the ecological association between terrestrial and cosmic gamma radiation, indoor radon, and acute leukemia incidence among children under 15 y of age. From 1990 to 2001, 5,330 cases of acute leukemia were registered by the French National Registry of Childhood Leukemia and Lymphoma. Exposure to terrestrial gamma radiation was based on measurements, using thermoluminescent dosimeters, at about 1,000 sites covering all the "Departements." In addition, 8,737 indoor terrestrial gamma dose rate measurements covering 62% of the "Departements" and 13,240 indoor radon concentration measurements covering all the "Departements" were made during a national campaign. Cosmic ray doses were estimated in each of the 36,363 "Communes" of France. There was no evidence of an ecological association between terrestrial gamma dose (range: 0.22-0.90 mSv y) or total gamma dose (range: 0.49-1.28 mSv y) and childhood acute leukemia incidence, for acute myeloid leukemia (AML) or for acute lymphoblastic leukemia (ALL), in univariate or multivariate regression analyses including indoor radon. A significant positive association between indoor radon (range: 22-262 Bq m) and AML incidence among children was observed and remained significant in multivariate regression analyses including either terrestrial gamma dose [SIR per 100 Bq m = 1.29 (1.09-1.53)] or total gamma dose [SIR per 100 Bq m = 1.29 (1.09-1.53)]. The study showed no ecological association between terrestrial gamma radiation and childhood leukemia for the range of variation in gamma dose rates observed in France. The moderate ecological association between childhood AML incidence and indoor radon does not appear to be confounded by terrestrial gamma dose.

Childhood leukaemia incidence around French nuclear installations using geographic zoning based on gaseous discharge dose estimates

Abstract: The present study investigated for the first time the incidence of childhood leukaemia (1990–2001) around French nuclear installations using a geographic zoning based on estimated doses to the red bone marrow due to gaseous radioactive discharges. The observed number of cases of acute leukaemia (O=750) in 40 km2 centred on 23 French nuclear installations between 1990 and 2001 was lower than expected (E=795.01), although not significantly so (standardised incidence ratio SIR=0.94, 95% confidence interval=(0.88–1.01)). In none of the five zones defined on the basis of the estimated doses was the SIR significantly >1. There was no evidence of a trend in SIR with the estimated doses for all the children or for any of the three age groups studied. This study confirmed that there was no evidence of an increased incidence of childhood leukaemia around the 23 French nuclear sites.

Risk analysis of leukaemia incidence among people living along the Techa River: a nested case-control study.

Abstract: Large quantities of radioactive materials released over time from the Mayak nuclear weapons facility caused significant internal and external exposure for people living along the banks of the Techa River (Southern Urals, Russia). We conducted a nested case-control study in the Extended Techa River Cohort to determine whether the risk of leukaemia incidence increased with protracted exposure to ionising radiation or with other non-radiation risk factors. The study included 83 cases identified over 47 years of follow-up and 415 controls matched for sex, age at diagnosis, age (within a 5 year age group), and date of initial residence in the riverside area. External and internal doses have been calculated using the Techa River Dosimetry System 1996 (TRDS96). Conditional logistic regression was used to calculate odds ratios per Gray (OR/Gy) and 95% confidence intervals (95% CI). After excluding cases of chronic lymphoid leukaemia, the OR/Gy of total, external, and internal doses were 4.6 (95% CI: 1.7-12.3), 7.2 (95%CI: 1.7-30.0) and 5.4 (95%CI: 1.1-27.2), respectively. A history of solid tumour, either malignant or benign, before the leukaemia diagnosis was associated with a 2.5-fold increase in the leukaemia risk (95% CI: 1.1-5.9). Even though the analysis of confounders was less useful than expected because of missing data, multivariate analyses that took the exposure dose into account confirmed the association between leukaemia incidence and tumour history.

Childhood Leukaemia Incidence Around French Nuclear Installations Using Geographic Zoning Based on Gaseous Discharge Dose Estimates

Abstract: The present study investigated for the first time the incidence of childhood leukaemia (1990–2001) around French nuclear installations using a geographic zoning based on estimated doses to the red bone marrow due to gaseous radioactive discharges. The observed number of cases of acute leukaemia (O=750) in 40 km2 centred on 23 French nuclear installations between 1990 and 2001 was lower than expected (E=795.01), although not significantly so (standardised incidence ratio SIR=0.94, 95% confidence interval=(0.88–1.01)). In none of the five zones defined on the basis of the estimated doses was the SIR significantly >1. There was no evidence of a trend in SIR with the estimated doses for all the children or for any of the three age groups studied. This study confirmed that there was no evidence of an increased incidence of childhood leukaemia around the 23 French nuclear sites.

Down Syndrome Time-Clustering in January 1987 in Belarus: Link with the Chernobyl Accident?

Abstract: The Chernobyl accident (April 26, 1986) exposed a large part of the Belarus population to ionizing radiation. We analyzed the time trends of Down syndrome (DS) in Belarus to evaluate whether either brief exposure at high dose rates during the plume passage or continuous exposure at low doses and dose rates of the residents of contaminated areas had any detectable impact on DS prevalence at birth. DS data came from the Belarus National Registry of Congenital Malformations (1981-2001). We observed a significant peak of DS in January 1987 (26 cases observed and 9.84 expected; observed/expected ratio=2.64; 95% CI=1.72-3.76), but found no positive long-term time trends in contaminated or control areas. The time occurrence of the January peak, high dose rates during the plume passage and experimental data showing a radiosensitive phase of oogenesis around conception time in mammals suggest that the January peak may be linked to the Chernobyl plume.