Extended analysis of solid cancer incidence among nuclear industry workers in the UK 1955-2011: comparison of workers first hired in earlier and later periods.

To address points arising from the recent study of nuclear workers in the USA and the International Nuclear Workers Study (INWORKS), concerning the difference in solid cancer risk estimates between those first hired in earlier and later calendar years, subsidiary analyses were conducted on a cohort of 172 452 workers in the National Registry for Radiation Workers (NRRW) from the UK. A total of 18 310 incident first primary solid cancer cases were registered in the period from 1955 until 2011 in the NRRW cohort and workers accrued 5.25 million person-years of follow-up. Incidences rates of all solid cancers combined, lung cancer and solid cancer excluding lung cancer were examined in terms of external radiation doses in the full cohort and in a sub-cohort of workers who had no record of internal exposure monitoring and were defined by the periods of first hire before and after the beginning of the years 1960, 1965 and 1970. All analyses were carried out using Poisson Regression. These analyses demonstrated that only for lung cancer between the pre-1965 and post-1964 periods is there strong evidence for a difference in the risks using the NRRW full cohort. In the other calendar period breakdowns and for the other cancer groups, there is no clear evidence of differences in the risks. The NRRW estimation of risks between recent and early workers is not generally consistent with the US workers cohort or the INWORKS evaluations that later hired workers are at much higher solid cancer risk than earlier hired workers, although INWORKS contains a significant part of the latest updated NRRW cohort as well as the US data. The conclusion that the INWORKS and US study data demonstrate a real difference in excess solid cancer risk from external radiation exposure between earlier and later workers is premature. The results presented here should also be treated with caution because of the limited corroborating evidence from other published studies. Information on internal doses, neutron doses as well as non-radiation factors such as smoking and asbestos exposure would be needed to make definitive inferences.

Shape of radiation dose response relationship for ischaemic heart disease mortality and its interpretation: analysis of the national registry for radiation workers (NRRW) cohort.

Statistically significant increases in ischemic heart disease (IHD) mortality with cumulative occupational external radiation dose were observed in the National Registry for Radiation Workers (NRRW) cohort. There were 174 541 subjects in the NRRW cohort. The start of follow up was 1955, and the end of the follow-up for each worker was chosen as the earliest date of death or emigration, their 85th birthday or 31 December 2011. The dose-response relationship showed a downward curvature at a higher dose level >0.4 Sv with the overall shape of the dose-response relationship best described by a linear-quadratic model. The smaller risk at dose >0.4 Sv appears to be primarily associated with workers who started employment at a younger age (<30 years old) and those who were employed for more than 30 years. We modelled the dose response by age-at-first exposure. For the age-at-first exposure of 30+ years old, a linear dose-response was the best fit. For age-at-first exposure <30 years old, there was no evidence of excess risk of IHD mortality for radiation doses below 0.1 Sv or above 0.4 Sv, excess risk was only observed for doses between 0.1-0.4 Sv. For this age-at-first exposure group, it was also found that the doses they received when they were less than 35 years old or greater than 50 years old did not contribute to any increased IHD risk.

Effects of radiation on respiratory disease mortality: analysis of the national registry for radiation workers in United Kingdom.

PURPOSE: While some evidence of an effect of radiation exposure on respiratory disease at low dose levels has now emerged, there is heterogeneity in the risks between different studies and countries. In this paper, we aim to show the effect of radiation on three different sub-types of respiratory disease mortality through the analysis of the NRRW cohort in UK. MATERIALS AND METHODS: The NRRW cohort consisted of 174,541 radiation workers. Doses to the surface of the body were monitored using individual film badges. Most of the doses are associated with X-rays and gamma rays and to a less extent of beta and neutron particles. The overall mean 10-year lagged lifetime external dose was 23.2 mSv. Some workers were potentially exposed to alpha particles. However, doses from internal emitters were not available for the NRRW cohort. 25% of male workers and 17% of female workers were identified as being monitored for internal exposure. The Poisson regression methods for grouped survival data with a stratified baseline hazard function were used to describe the dependence of the risk on cumulative external radiation dose. The disease was analyzed by the following subgroups: Pneumonia (1066 cases including 17 cases of influenza), COPD and allied disease (1517 cases) and other remaining respiratory diseases (479 cases). RESULTS: There was very little radiation effect on pneumonia mortality, but evidence of a reduction in mortality risk for COPD and allied disease (ERR/Sv= -0.56, 95%CI: -0.94, -0.06; p = .02) and an increase in risk for other respiratory disease mortality (ERR/Sv = 2.30, 95%CI: 0.67, 4.62; p = .01) with increasing cumulative external dose were observed. The effects of radiation were more prominent amongst workers monitored for internal exposure. The reduction in mortality risk of COPD and allied disease per cumulative external dose was statistically significant for the radiation workers monitored for internal exposure (ERR/Sv= -0.59, 95%CI: -0.99, -0.05; p = .017) but not significant among the workers who were not monitored (ERR/Sv= -0.43, 95%CI: -1.20, 0.74; p = .42). A statistically significant increased risk was observed for other respiratory diseases among monitored radiation workers (ERR/Sv = 2.46, 95%CI: 0.69, 5.08; p = .019), but not among unmonitored workers (ERR/Sv = 1.70, 95%CI: -0.82, 5.65; p = .25). CONCLUSION: The effects of radiation exposure can be different depending on the type of respiratory disease. No effect was seen in pneumonia; a reduction in mortality risk of COPD, and increased mortality risk of other respiratory diseases were observed with cumulative external radiation dose. More studies are needed to verify these findings.

Extended analysis of solid cancer incidence among the Nuclear Industry Workers in the UK: 1955-2011.

Radiation worker studies provide direct estimates of cancer risk after protracted low-dose exposures to external X-ray and gamma-ray irradiations. The National Registry for Radiation Workers (NRRW) started in 1976 and has become the largest epidemiological program of research on nuclear workers in the UK. Here, we report on the relationship between solid cancer incidence and external radiation at the low-dose levels in 172,452 NRRW cohort members of whom (90%) were men. This study is based on 5.25 million person-years of follow-up from 1955 through the end of 2011. In the range of accumulated low doses two-thirds of workers have doses of less than 10 mSv. This study is an updated analysis of solid cancer incidence data with an additional 10 years of follow-up over the previous analysis of the NRRW cohort (NRRW-3). A total of 18,310 cases of solid cancers based on a 10-year lag were registered and of these 43% of the solid cancer cases occurred during the latest 10 years. Poisson regression was used to investigate the relationship between solid cancers risk and protracted chronic low-dose radiation exposure. This study demonstrated for solid cancers a rapid decrease of risk at high external doses that appeared to be driven by the workers who were monitored for potential exposure to internal emitters and who had also received relatively high external doses. Among cohort members only exposed to external radiation, a strong association was found between external dose and solid cancers (ERR/Sv = 0.52, 95% CI: 0.11; 0.96, based on 13,199 cases). A similar pattern is also seen for lung cancer. Excluding lung cancer from the grouping of all solid cancers resulted in evidence of a linear association with external radiation dose (ERR/Sv = 0.24, 95% CI: 0.01; 0.49, based on 15,035 cases), so suggesting some degree of confounding by smoking. Statistically significantly increasing trends with dose were seen for cancers of the colorectal, bladder and pleura cancer. Some of these results should be treated with caution because of the limited corroborating evidence from other published studies. Information on internal doses as well as non-radiation factors such smoking would be helpful to make more definitive inferences.

Radiation risks of lymphoma and multiple myeloma incidence in the updated NRRW-3 cohort in the UK: 1955-2011.

The effect of external radiation on lymphoma, including non-Hodgkin lymphoma (NHL), Hodgkin lymphoma (HL) and multiple myeloma (MM) incidence was evaluated in the National Registry for Radiation Workers based upon the third analysis cohort but with an additional 10 years of follow-up. The study includes 172 452 workers, of whom (90%) were men with 5.25 million person-years of follow-up from 1955 through to the end of 2011. A total of 711 cases of NHL, 113 cases of HL and 279 cases of MM were registered. Poisson regression was used to estimate the excess relative risk per unit of cumulative exposure to ionising radiation. A statistically significant association was found between radiation dose and the incidence of NHL and MM. There was no evidence of radiation associated excess risk for HL. The reported associations are based on a very small proportion of exposed workers, in particular among workers with cumulative doses above 0.5 Sv so should be treated with caution, further investigations are necessary to confirm our results.

A 10-year follow-up study of yearly indoor radon measurements in homes, review of other studies and implications on lung cancer risk estimates.

Uncertainty on long-term average radon concentration has a large impact on lung cancer risk assessment in epidemiological studies. The uncertainty can be estimated by year-to-year radon concentration variability, however few data are available. In Italy a study has been planned and conducted to evaluate year-to-year radon variability over several years in normally inhabited dwellings, mainly located in Rome. This is the longest study of this kind in Europe; repeat radon measurements are carried out for 10 years using LR-115 radon detectors in the same home in consecutive years. The study includes 84 dwellings with long-term average radon concentration ranging from 28 to 636 Bq/m3. The result shows that year-to-year variability of repeated measurements made in the same home in different years is low, with an overall coefficient of variation of 17%. This is smaller than most of those observed in studies from other European countries and USA, ranging from 15% to 62%. Influencing factors that may explain the differences between this study and other studies have been discussed. Due to the low yearly variability estimated in the present 10-year study, a negligible impact on lung cancer risk estimate for the Italian epidemiological study is expected.

Mortality from heart diseases following occupational radiation exposure: analysis of the National Registry for Radiation Workers (NRRW) in the United Kingdom.

Statistically significant increases in heart disease (HD) mortality with cumulative recorded occupational radiation dose from external sources were observed among 174 541 subjects, who were predominately exposed to protracted low doses over a number of years, and were followed up until the end of 2011 in the UK National Registry for Radiation Workers (NRRW) cohort. Amongst the subtypes of HD, the increasing trends with cumulative dose arose for ischaemic heart disease (IHD) and other HD (which includes pulmonary HD, valve disorders, cardiomyopathy, cardiac dysrhythmias, carditis, conduction disorder and ill-defined HD). For IHD, the increased mortality appears to be at least 20 years after first exposure and the excess risk peaked between 30 and 40 years after the first exposure. There was no evidence of excess risk of IHD mortality for cumulative radiation doses below 0.1 Sv. A categorical analysis also showed that the risk falls below the expected value based on a linear trend, for cumulative doses greater than 0.4 Sv; this smaller risk appears to be primarily associated with workers who started employment at a younger age and who were employed for longer than 30 years, reflecting possible healthy worker survivor effect. This analysis provided further evidence that low doses of radiation exposure may be associated with increased risk of IHD. For other HD, the data suggest an increased risk starting around 40 years after the first exposure. The risk was statistically significant raised only for cumulative doses above 0.4 Sv. However, the number of deaths in this group was small and the results need to be interpreted with caution.

Cancer mortality and incidence following external occupational radiation exposure: an update of the 3rd analysis of the UK national registry for radiation workers.

BACKGROUND: This study provides direct evidence of cancer risk from low dose and dose rate occupational external radiation exposures. METHODS: Cancer mortality and incidence were studied in relation to external radiation exposure in the National Registry for Radiation Workers. A cohort of 167,003 workers followed for an average of 32 years was analysed using Poisson regression methods. RESULTS: Mortality and incidence risks were significantly raised for the group of all malignant neoplasms excluding leukaemia (ERR/Sv mortality = 0.28; 90%CI: 0.06, 0.53, ERR/Sv incidence = 0.28; 90%CI: 0.10, 0.48) but with narrower confidence bounds compared with the previous analysis of this cohort reflecting the increased statistical power from the additional 10 years of follow-up information. The linear trends in relative risk for both mortality and incidence of these cancers remained statistically significantly raised when information relating to cumulative doses above 100 mSv was excluded (ERR/Sv mortality = 1.42; 90%CI: 0.51, 2.38 and ERR/Sv incidence = 1.18; 90%CI: 0.47, 1.92). CONCLUSIONS: This study improved the precision of the cancer risk estimates seen in the third analysis of the NRRW cohort. The overall results remain consistent with the risk estimates from the Life Span Study and those adopted in the current ICRP recommendations.

Radiation Risks of Leukemia, Lymphoma and Multiple Myeloma Incidence in the Mayak Cohort: 1948-2004.

Incidence of all types of lymphatic and hematopoietic cancers, including Hodgkin's lymphoma, non-Hodgkin's lymphoma, multiple myeloma, acute and chronic myeloid leukemia (AML and CML respectively), chronic lymphocytic leukemia (CLL) and other forms of leukemia have been studied in a cohort of 22,373 workers employed at the Mayak Production Association (PA) main facilities during 536,126 person-years of follow-up from the start of employment between 1948 and 1982 to the end of 2004. Risk assessment was performed for both external gamma-radiation and internal alpha-exposure of red bone marrow due to incorporated Pu-239 using Mayak Workers Dosimetry System 2008 taking into account non-radiation factors. The incidence of leukemia excluding CLL showed a non-linear dose response relationship for external gamma exposure with exponential effect modifiers based on time since exposure and age at exposure. Among the major subtypes of leukemia, the excess risk of AML was the highest within the first 2-5 years of external exposure (ERR per Gy: 38.40; 90% CI: 13.92-121.4) and decreased substantially thereafter, but the risks remained statistically significant (ERR per Gy: 2.63; 90% CI: 0.07-12.55). In comparison, excess CML first occurred 5 years after exposure and decreased about 10 years after exposure, although the association was not statistically significant (ERR per Gy: 1.39; 90% CI: -0.22-7.32). The study found no evidence of an association between leukemia and occupational exposure to internal plutonium ERR per Gy 2.13; 90% CI: <0-9.45). There was also no indication of any relationship with either external gamma or internal plutonium radiation exposure for either incidence of Hodgkin or non-Hodgkin lymphoma or multiple myeloma.

Calculation of lifetime lung cancer risks associated with radon exposure, based on various models and exposure scenarios.

The risk of lung cancer mortality up to 75 years of age due to radon exposure has been estimated for both male and female continuing, ex- and never-smokers, based on various radon risk models and exposure scenarios. We used risk models derived from (i) the BEIR VI analysis of cohorts of radon-exposed miners, (ii) cohort and nested case-control analyses of a European cohort of uranium miners and (iii) the joint analysis of European residential radon case-control studies. Estimates of the lifetime lung cancer risk due to radon varied between these models by just over a factor of 2 and risk estimates based on models from analyses of European uranium miners exposed at comparatively low rates and of people exposed to radon in homes were broadly compatible. For a given smoking category, there was not much difference in lifetime lung cancer risk between males and females. The estimated lifetime risk of radon-induced lung cancer for exposure to a concentration of 200 Bq m(-3) was in the range 2.98-6.55% for male continuing smokers and 0.19-0.42% for male never-smokers, depending on the model used and assuming a multiplicative relationship for the joint effect of radon and smoking. Stopping smoking at age 50 years decreases the lifetime risk due to radon by around a half relative to continuing smoking, but the risk for ex-smokers remains about a factor of 5-7 higher than that for never-smokers. Under a sub-multiplicative model for the joint effect of radon and smoking, the lifetime risk of radon-induced lung cancer was still estimated to be substantially higher for continuing smokers than for never smokers. Radon mitigation-used to reduce radon concentrations at homes-can also have a substantial impact on lung cancer risk, even for persons in their 50 s; for each of continuing smokers, ex-smokers and never-smokers, radon mitigation at age 50 would lower the lifetime risk of radon-induced lung cancer by about one-third. To maximise risk reductions, smokers in high-radon homes should both stop smoking and remediate their homes.

Joint analysis of three European nested case-control studies of lung cancer among radon exposed miners: exposure restricted to below 300 WLM.

Analyses of lung cancer risk were carried out using restrictions to nested case-control data on uranium miners in the Czech Republic, France, and Germany. With the data restricted to cumulative exposures below 300 working-level-months (WLM) and adjustment for smoking status, the excess relative risk (ERR) per WLM was 0.0174 (95% CI: 0.009-0.035), compared to the estimate of 0.008 (95% CI: 0.004-0.014) using the unrestricted data. Analysis of both the restricted and unrestricted data showed that time since exposure windows had a major effect; the ERR/WLM was six times higher for more recent exposures (5-24 y) than for more distant exposures (25 y or more). Based on a linear model fitted to data on exposures <300 WLM, the ERR WLM of lung cancer at 30 y after exposure was estimated to be 0.021 (95% CI: 0.011-0.040), and the risks decreased by 47% per decade increase in time since exposure. The results from analyzing the joint effects of radon and smoking were consistent with a sub-multiplicative interaction; the ERR WLM was greater for non-smokers compared with current or ex-smokers, although there was no statistically significant variation in the ERR WLM by smoking status. The patterns of risk with radon exposure from the combined European nested case-control miner analysis were generally consistent with those based on the BEIR VI Exposure-Age-Concentration model. Based on conversions from WLM to time weighted averaged radon concentration (expressed per 100 Bq m), the results from this analysis of miner data were in agreement with those from the joint analysis of the European residential radon studies.

Ischemic heart disease in nuclear workers first employed at the Mayak PA in 1948-1972.

Following an earlier study of incidence and mortality of ischemic heart disease (IHD) published in 2010, a second analysis has been conducted based on an extended cohort and five additional years of follow-up. The cohort includes 18,763 workers, of whom 25% were females, first employed at the Mayak PA in 1948-1972 and followed up to the end of 2005. Some of these workers were exposed to external gamma rays only, and others were exposed to a mixture of external gamma-rays and internal alpha-particle radiation. A total of 6,134 cases and 2,629 deaths from IHD were identified in the study cohort. A statistically significant increasing trend was found with total external gamma-ray dose in IHD incidence (ERR/Gy 0.099; 95% CI: 0.045-0.153) after adjusting for non-radiation factors. This value reduced slightly when adjusting for internal liver dose. There was no statistically significant increase trend for internal liver dose in IHD incidence. These findings were consistent with an earlier study. New findings in IHD incidence revealed a statistically significant decrease in IHD incidence among workers exposed to external gamma-rays doses of 0.2-0.5 Gy in relation to the external doses below 0.2 Gy. This decreased risk is heavily influenced by female workers. This finding has never been reported in other studies, and the results should be treated with caution. The findings for IHD mortality are similar to those results in the earlier analysis; there was no statistically significant trend with external gamma-ray dose or for internal liver dose after adjustment for external dose. The risk estimates obtained from these analyses of IHD incidence and mortality in relation to external gamma-rays in the cohort of Mayak workers are generally compatible with those from other large occupational radiation worker studies and the Japanese atomic bomb survivors.

Cerebrovascular diseases in nuclear workers first employed at the Mayak PA in 1948-1972.

Incidence and mortality from cerebrovascular diseases (CVD) (430-438 ICD-9 codes) have been studied in a cohort of 18,763 workers first employed at the Mayak Production Association (Mayak PA) in 1948-1972 and followed up to the end of 2005. Some of the workers were exposed to external gamma-rays only while others were exposed to a mixture of external gamma-rays and internal alpha-particle radiation due to incorporated (239)Pu. After adjusting for non-radiation factors, there were significantly increasing trends in CVD incidence with total absorbed dose from external gamma-rays and total absorbed dose to liver from internal alpha radiation. The CVD incidence was statistically significantly higher among workers with total absorbed external gamma-ray doses greater than 0.20 Gy compared to those exposed to lower doses; the data were consistent with a linear trend in risk with external dose. The CVD incidence was statistically significantly higher among workers with total absorbed internal alpha-radiation doses to liver from incorporated (239)Pu greater than 0.025 Gy compared to those exposed to lower doses. There was no statistically significant trend in CVD mortality risk with either external gamma-ray dose or internal alpha-radiation dose to liver. The risk estimates obtained are generally compatible with those from other large occupational studies, although the incidence data point to higher risk estimates compared to those from the Japanese A-bomb survivors. Further studies of the unique cohort of Mayak workers chronically exposed to external and internal radiation will allow improving the reliability and validating the radiation safety standards for occupational and public exposure.

Radon, smoking and lung cancer risk: results of a joint analysis of three European case-control studies among uranium miners.

A combined analysis of three case-control studies nested in three European uranium miner cohorts was performed to study the joint effects of radon exposure and smoking on lung cancer death risk. Occupational history and exposure data were available from the cohorts. Smoking information was reconstructed using self-administered questionnaires and occupational medical archives. Linear excess relative risk models adjusted for smoking were used to estimate the lung cancer risk associated with radon exposure. The study includes 1046 lung cancer cases and 2492 controls with detailed radon exposure data and smoking status. The ERR/WLM adjusted for smoking is equal to 0.008 (95% CI: 0.004-0.014). Time since exposure is shown to be a major modifier of the relationship between radon exposure and lung cancer risk. Fitting geometric mixture models yielded arguments in favor of a sub-multiplicative interaction between radon and smoking. This combined study is the largest case-control study to investigate the joint effects of radon and smoking on lung cancer risk among miners. The results confirm that the lung carcinogenic effect of radon persists even when smoking is adjusted for, with arguments in favor of a sub-multiplicative interaction between radon and smoking.

Two error components model for measurement error: application to radon in homes.

In this paper, a simple model for analysing variability in radon concentrations in homes is tested. The approach used here involves two error components, representing additive and multiplicative errors, together with variation between-houses. We use a Bayesian approach for our analysis and apply this model to two datasets of repeat radon measurements in homes; one based on 3-month long measurements for which the original measurements were close to the current UK Radon Action Level (200 Bq m(-3)), and the other based on 6-month measurement data (from regional and national surveys), for which the original measurements cover a wide range of radon concentrations, down to very low levels. The model with two error components provides a better fit to these datasets than does a model based on solely multiplicative errors.

Uncertainties in radon related to house-specific factors and proximity to geological boundaries in England.

Data collected as a part of a survey on radon concentrations from about 40 000 dwellings in England for six contrasting geological units were analysed to evaluate the impact of house-specific factors (building characteristics and construction dates) and of proximity to geological boundaries. After adjusting for temperature and outdoor radon, geological unit, house type, double glazing and date of building were found to have a statistically significant influence on indoor radon concentrations and explained about 29 % of the total variation between dwellings in logarithmically transformed radon values. In addition, there were statistically significant differences in radon concentrations according to proximity to geological boundaries categories for most of the geological units, but no consistent pattern could be detected.

Review of relative biological effectiveness dependence on linear energy transfer for low-LET radiations.

Information on Japanese A-bomb survivors exposed to gamma radiation has been used to estimate cancer risks for the whole range of photon (x-rays) and electron energies which are commonly encountered by radiation workers in the work place or by patients and workers in diagnostic radiology. However, there is some uncertainty regarding the radiation effectiveness of various low-linear energy transfer (low-LET) radiations (x-rays, gamma radiation and electrons). In this paper we review information on the effectiveness of low-LET radiations on the basis of epidemiological and in vitro radiobiological studies. Data from various experimental studies for chromosome aberrations and cell transformation in human lymphocytes and from epidemiological studies of the Japanese A-bomb survivors, patients medically exposed to radiation for diagnostic and therapeutic procedures, and occupational exposures of nuclear workers are considered. On the basis of in vitro cellular radiobiology, there is considerable evidence that the relative biological effectiveness (RBE) of high-energy low-LET radiation (gamma radiation, electrons) is less than that of low-energy low-LET radiation (x-rays, betas). This is a factor of about 3 to 4 for 29 kVp x-rays (e.g. as in diagnostic radiation exposures of the female breast) and for tritium beta-rays (encountered in parts of the nuclear industry) relative to Co-60 gamma radiation and 2-5 MeV gamma-rays (as received by the Japanese A-bomb survivors). In epidemiological studies, although for thyroid and breast cancer there appears to be a small tendency for the excess relative risks to decrease as the radiation energy increases for low-LET radiations, it is not statistically feasible to draw any conclusion regarding an underlying dependence of cancer risk on LET for the nominally low-LET radiations.

Possible selection effects for radiation risk estimates in Japanese A-bomb survivors: reanalysis of acute radiation symptoms data.

An earlier analysis examined the possibility of bias in the Life Span Study (LSS) cohort by studying Japanese A-bomb survivors with bomb-related acute injuries and those without such injuries. The authors reported significantly higher radiation risks, both for cancers and non-cancers, among those survivors with acute injuries compared with those without. The risks were reported to be particularly large among survivors aged <10 or > or =55 years of age at the time of bombings. The aim of this paper is to examine these findings more closely using the LSS acute effects data. All the analyses were carried out using Poisson regression. Relative risk models were fitted with adjustment for sex and other factors. Significant differences in relative risk between survivors with epilation and burns and those without epilation and burns are found for leukaemia. There is also some evidence for heterogeneity in the leukaemia risk between survivors with two or more acute injuries and those with no injuries, but the evidence is disappeared when survivors with one or more injuries are compared with those without injuries. For solid cancers, cardiovascular disease and all deaths combined, the risks do not differ to a statistically significant extent between survivors with and without injuries. There is no statistically significant heterogeneity in risk across age-at-exposure categories for survivors with injuries. For all deaths combined, relative risk estimates and their uncertainties are significantly higher for survivors exposed at ages <10 years when compared with other exposure ages, but risks are not significantly raised for survivors exposed at > or =55 years of age. With the exception of leukaemia, the findings from the present work are inconsistent with those of Stewart and Kneale.

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.

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.