Mortality and cancer incidence following occupational radiation exposure: third analysis of the National Registry for Radiation Workers

Mortality and cancer incidence were studied in the National Registry for Radiation Workers in, relative to earlier analyses, an enlarged cohort of 174 541 persons, with longer follow-up (to 2001) and, for the first time, cancer registration data. SMRs for all causes and all malignant neoplasms were 81 and 84 respectively, demonstrating a ‘healthy worker effect'. Within the cohort, mortality and incidence from both leukaemia excluding CLL and the grouping of all malignant neoplasms excluding leukaemia increased to a statistically significant extent with increasing radiation dose. Estimates of the trend in risk with dose were similar to those for the Japanese A-bomb survivors, with 90% confidence intervals that excluded both risks more than 2–3 times greater than the A-bomb values and no raised risk. Some evidence of an increasing trend with dose in mortality from all circulatory diseases may, at least partly, be due to confounding by smoking. This analysis provides the most precise estimates to date of mortality and cancer risks following occupational radiation exposure and strengthens the evidence for raised risks from these exposures. The cancer risk estimates are consistent with values used to set radiation protection standards

Dose–responses from multi-model inference for the non-cancer disease mortality of atomic bomb survivors

The non-cancer mortality data for cerebrovascular disease (CVD) and cardiovascular diseases from Report 13 on the atomic bomb survivors published by the Radiation Effects Research Foundation were analysed to investigate the dose–response for the influence of radiation on these detrimental health effects. Various parametric and categorical models (such as linear-no-threshold (LNT) and a number of threshold and step models) were analysed with a statistical selection protocol that rated the model description of the data. Instead of applying the usual approach of identifying one preferred model for each data set, a set of plausible models was applied, and a sub-set of non-nested models was identified that all fitted the data about equally well. Subsequently, this sub-set of non-nested models was used to perform multi-model inference (MMI), an innovative method of mathematically combining different models to allow risk estimates to be based on several plausible dose–response models rather than just relying on a single model of choice. This procedure thereby produces more reliable risk estimates based on a more comprehensive appraisal of model uncertainties. For CVD, MMI yielded a weak dose–response (with a risk estimate of about one-third of the LNT model) below a step at 0.6 Gy and a stronger dose–response at higher doses. The calculated risk estimates are consistent with zero risk below this threshold-dose. For mortalities related to cardiovascular diseases, an LNT-type dose–response was found with risk estimates consistent with zero risk below 2.2 Gy based on 90% confidence intervals. The MMI approach described here resolves a dilemma in practical radiation protection when one is forced to select between models with profoundly different dose–responses for risk estimates

Mortality and cancer registration experience of the Sellafield workers known to have been involved in the 1957 Windscale accident: 50 year follow-up

This paper studies the mortality and cancer morbidity of the 470 male workers involved in tackling the 1957 Sellafield Windscale fire or its subsequent clean-up. Workers were followed up for 50 years to 2007, extending the follow-up of a previously published cohort study on the Windscale fire by 10 years. The size of the study population is small, but the cohort is of interest because of the involvement of the workers in the accident. Significant excesses of deaths from diseases of the circulatory system (standardised mortality ratio (SMR) = 120, 95% CI = 103-138; 194 deaths) driven by ischaemic heart disease (IHD) (SMR = 133, 95% CI = 112-157, 141 deaths) were found when compared with the population of England and Wales but not when compared with the population of Northwest England (SMR = 105, 95% CI = 90-120 and SMR = 115, 95% CI = 97-136 respectively). When compared with those workers in post at the time of the fire but not directly involved in the fire the mortality rate from IHD among those involved in tackling the fire was raised but not statistically significantly (rate ratio (RR) = 1.11, 95% CI = 0.92-1.33). A RR of 1.11 is consistent with an excess relative risk of 0.65 Sv(-1) as reported in an earlier study of non-cancer mortality in the British Nuclear Fuels plc cohort of which these workers are a small but significant part. There was a statistically significant difference in lung cancer mortality (RR = 2.18, 95% CI = 1.05-4.52) rates between workers who had received higher recorded external doses during the fire and those who had received lower external doses. Comparison of the mortality rates of workers directly involved in the accident with workers in post, but not so involved, showed no significant differences overall. On the basis of the use of a propensity score the average effect of involvement in the Windscale fire on all causes of death was - 2.13% (se = 3.64%, p = 0.56) though this difference is not statistically significant. The average effect of involvement in the Windscale fire was - 5.53% (se = 3.81, p = 0.15) for all cancers mortality and 6.60% (se = 4.03%, p = 0.10) for IHD mortality though neither figure was statistically significant. This analysis of the mortality and cancer morbidity experience of those Sellafield workers involved in the 1957 Windscale fire does not reveal any measurable effect of the fire upon their health. Although this study has low statistical power for detecting small adverse effects, due to the relatively small number of workers, it does provide reassurance that no significant health effects are associated with the 1957 Windscale fire even after 50 years of follow-up

Mortality experience of male workers at a UK tin smelter.

Background Between 1937 and 1991, Capper Pass and Sons Limited operated a tin smelter complex in North Humberside, UK, at which employees were potentially exposed to a number of substances, including lead, arsenic, cadmium and natural series radionuclides. Decommissioning and site clearance continued until 1995. Between 1967 and 1995 the company was a subsidiary of Rio Tinto plc.Aims The aim was to identify any significant excess, or deficits, in mortality among former employees that might be attributable to factors associated with occupation.Methods We defined a cohort of 1462 males who had been employed for at least 12 months between 1/11/1967 and 28/7/1995, followed-up through to 31/12/2001. The mortality of the cohort was compared against that expected for both national and regional populations.Results Mortality from all causes and all cancers did not differ from that expected. Mortality from ischaemic heart disease showed a deficit and mortality from lung cancer showed a statistically significant excess. Mortality from smoking related diseases other than lung cancer showed a non-significant deficit.Conclusions The pattern of lung cancer mortality is consistent with the hypothesis that the risk of lung cancer has been enhanced by occupational exposure to one or more carcinogens, the effect of which diminishes with time since exposure. The deficit in ischaemic heart disease may be attributed to a protective effect from manual labour. The results provide no evidence for attribution of other excess or deficits in mortality to factors associated with employment

Effets de la contamination chronique à l’uranium sur la mortalité : bilan d’une étude-pilote chez les travailleurs de l’industrie nucléaire en France

National audienceBackground This article presents the mortality data compiled among a cohort of workers at risk of internal uranium exposure and discusses the extent to which this exposure might differentiate them from other nuclear workers. Methods The cohort consisted of 2897 Areva-NC-Pierrelatte plant workers, followed from 1st January 1968 through 31st December 2006 (79,892person-years). Mortality was compared with that of the French population, by calculating Standardized Mortality Ratios (SMR) and 95% confidence intervals (CI95%). External radiation exposure was reconstructed using external dosimetry archives. Internal uranium exposure was assessed using a plant-specific job-exposure-matrix, considering six types of uranium compounds according to their nature (natural and reprocessed uranium [RPU] and solubility [fast-F, moderate-M, and slow-S]). Exposure-effect analyses were performed for causes of death known to be related to external radiation exposure (all cancers and circulatory system diseases) and cancer of uranium target-organs (lung and hematopoietic and lymphatic tissues, HLT). Results A significant deficit of mortality from all causes (SMR=0.58; CI95% [0.53-0.63]), all cancers (SMR=0.72; CI95% [0.63-0.82]) and smoking related cancers was observed. Non-significant 30%-higher increase of mortality was observed for cancer of pleura (SMR=2.32; CI95% [0.75-5.41]), rectum and HLT, notably non-Hodgkin's lymphoma (SMR=1.38; CI95% [0.63-2.61]) and chronic lymphoid leukemia (SMR=2.36; CI95% [0.64-6.03]). No exposure-effect relationship was found with external radiation cumulative dose. A significant exposure-effect relationship was observed for slowly soluble uranium, particularly RPU, which was associated with an increase in mortality risk reaching 8 to 16% per unit of cumulative exposure score and 10 to 15% per year of exposure duration. Conclusion The Areva-NC-Pierrelatte workers cohort presents a non-significant over-mortality from HLT cancers, notably of lymphoid origin, unrelated to external radiation exposure. The pilot study suggests an association between mortality from the HLT and lung cancers and exposure to slowly soluble RPU compounds. The results of this study should be investigated further in more powerful studies, with a dose-response analysis based on individual assessment of uranium absorbed dose to uranium-target organs.Position du problème. Plusieurs études ont été réalisées chez les travailleurs du nucléaire français sur les effets de l’exposition externe aux rayonnements ionisants (RI). Une étude-pilote des effets de l’exposition interne à l’uranium sur la mortalité a été lancée en 2005. Les résultats de cette étude sont présentés et comparés à ceux des autres études des travailleurs du nucléaire. Méthodes: La cohorte de 2897 travailleurs de l’établissement Areva-NC-Pierrelatte a été suivie du 1er janvier 1968 jusqu’au 31 décembre 2006 (79 892 personnes-années). Sa mortalité est comparée à celle de la population française en calculant les SMR (« Standardized Mortality Ratio ») et les intervalles de confiance à 95 % (IC95 %). L’exposition externe aux RI est reconstituée via les archives dosimétriques. L’exposition à l’uranium est reconstituée via une matrice emplois-exposition. Six types d’uranium sont considérés selon leur isotopie (uranium naturel et uranium issu du retraitement, URT) et leur solubilité (forte-F, modérée-M et faible-S). L’analyse du lien entre les expositions et la mortalité porte sur les causes de décès associées aux RI (cancers et maladies du système circulatoire) et les cancers des organes-cibles de l’uranium inhalé (poumons et tissus lymphatique et hématopoïétique, TLH). Résultats: La cohorte présente une sous-mortalité toutes causes (SMR = 0,58 ; IC95 % [0,53–0,63]), tous cancers (SMR = 0,72 ; IC95 % [0,63–0,82]) et cancers associés au tabagisme traduisant l’effet du travailleur sain. Un excès non significatif est observé pour les cancers de la plèvre (SMR = 2,32 ; IC95 % [0,75–5,41]), du rectum et des TLH, notamment le lymphome non hodgkinien (SMR = 1,38 ; IC95 % [0,63–2,61]) et la leucémie lymphoïde chronique (SMR = 2,36 ; IC95 % [0,64–6,03]). Aucune relation significative avec la dose cumulée externe n’est mise en évidence. Pour l’uranium faiblement soluble, notamment l’URT, une augmentation de risque de mortalité de 8 à 16 % par point de score d’exposition cumulée et de 10 à 15 % par année d’exposition est observée. Conclusion: La cohorte Areva-NC-Pierrelatte présente une surmortalité (non significative) par cancers des TLH, notamment d’origine lymphoïde, sans lien avec l’exposition externe aux RI. L’étude-pilote suggère un lien entre la mortalité par cancer des TLH et des poumons et l’exposition à l’URT faiblement soluble. Ce résultat doit être confirmé par d’autres études, plus puissantes, et par des analyses dose-réponse reposant sur le calcul de la dose absorbée à l’organe-cible de l’uranium