The risk of acute myocardial infarction and arterial hypertension in a cohort of male employees of a Siberian Group of Chemical Enterprises exposed to long-term irradiation

Low- and moderate-dose non-cancer effects of ionizing radiation in directly exposed individuals, especially circulatory and ocular diseases: a review of the epidemiology

PURPOSE

There are well-known correlations between high and moderate doses (>0.5 Gy) of ionizing radiation exposure and circulatory system damage, also between radiation and posterior subcapsular cataract. At lower dose correlations with circulatory disease are emerging in the Japanese atomic bomb survivors and in some occupationally exposed groups, and are still to some extent controversial. Heterogeneity in excess relative risks per unit dose in epidemiological studies at low (<0.1 Gy) and at low-moderate (>0.1 Gy, <0.5 Gy) doses may result from confounding and other types of bias, and effect modification by established risk factors. There is also accumulating evidence of excess cataract risks at lower dose and low dose rate in various cohorts. Other ocular endpoints, specifically glaucoma and macular degeneration have been little studied. In this paper, we review recent epidemiological findings, and also discuss some of the underlying radiobiology of these conditions. We briefly review some other types of mainly neurological nonmalignant disease in relation to radiation exposure.

CONCLUSIONS

We document statistically significant excess risk of the major types of circulatory disease, specifically ischemic heart disease and stroke, in moderate- or low-dose exposed groups, with some not altogether consistent evidence suggesting dose-response non-linearity, particularly for stroke. However, the patterns of risk reported are not straightforward. We also document evidence of excess risks at lower doses/dose-rates of posterior subcapsular and cortical cataract in the Chernobyl liquidators, US Radiologic Technologists and Russian Mayak nuclear workers, with fundamentally linear dose-response. Nuclear cataracts are less radiogenic. For other ocular endpoints, specifically glaucoma and macular degeneration there is very little evidence of effects at low doses; radiation-associated glaucoma has been documented only for doses >5 Gy, and so has the characteristics of a tissue reaction. There is some evidence of neurological detriment following low-moderate dose (∼0.1-0.2 Gy) radiation exposure in utero or in early childhood.

[Markers of endothelial dysfunction in patients with arterial hypertension exposed to occupational irradiation of low intensity]

Aim To study the association between concentrations of endothelial dysfunction (ED) markers and arterial hypertension (AH) in people who were exposed to long-term action of "low-dose" ionizing radiation.Material and methods The study subjects were men of middle age (45-55 years) who were workers of the Siberian Integrated Chemical Plant with the length of service on the shop floor of at least 5 years. The subjects were divided into the main group (n=96) consisting of workers with grade 1-2 AH and the control group (n=48) consisting of arbitrarily healthy workers. Both groups contained workers who had been exposed to long-term occupational low-intensity irradiation (γ-radiation) and those not exposed to this irradiation. The study evaluated risk factors for cardiovascular diseases, presence of concomitant diseases, blood biochemistry (concentrations of glucose, high-sensitivity C-reactive protein (hsCRP), total cholesterol, low-density lipoproteins, high-density lipoproteins, triglycerides, creatinine, and ED markers, including endothelin, angiotensin II, von Willebrand factor, C-type natriuretic peptide, tissue plasminogen activator, tumor necrosis factor α (TNF-α), and homocysteine, major clinical data, total dose of external irradiation, and the content of 239Pu in the body.Results AH was associated primarily with excessive body weight and severity of atherogenic dyslipidemia and homocysteinemia. Higher plasma concentrations of TNF-α and a tendency to increasing hsCRP in the AH group, as distinct from the control group of arbitrarily healthy men, indicated a proinflammatory shift. The ED markers were related with clinical data of AH patients and associated with the lipid profile and increased blood concentrations of inflammatory mediators. The radiation exposure did not change the ED marker array in AH patients, which did not allow recommendation of the studied plasma indexes for detection of vascular endothelial injury in workers with AH of the Siberian Integrated Chemical Plant.Conclusion The study results evidenced the absence of adverse effects of long-term occupational exposure to low-intensity radiation on the vascular endothelium as evaluated by ED markers. In men aged 45-55 years, AH was associated primarily with excessive body weight, homocysteinemia, and atherogenic dyslipidemia.

Mortality from Circulatory System Diseases among French Uranium Miners: A Nested Case-Control Study

A significant association has been observed between radon exposure and cerebrovascular disease (CeVD) mortality among French uranium miners, but risk factors for circulatory system diseases (CSD) have not been previously considered. We conducted new analyses in the recently updated (through 2007) French cohort of uranium miners (n = 5,086), which included 442 deaths from CSD, 167 of them from ischemic heart disease (IHD) and 105 from CeVD. A nested case-control study was then set up to collect and investigate the influence of these risk factors on the relationships between mortality from CSD and occupational external gamma ray and internal ionizing radiation exposure (radon and long-lived radionuclides) in this updated cohort. The nested case-control study included miners first employed after 1955, still employed in 1976 and followed up through 2007. Individual information about CSD risk factors was collected from medical files for the 76 deaths from CSD (including 26 from IHD and 16 from CeVD) and 237 miners who had not died of CSD by the end of follow-up. The exposure-risk relationships were assessed with a Cox proportional hazard model weighted by the inverse sampling probability. A significant increase in all CSD and CeVD mortality risks associated with radon exposure was observed in the total cohort [hazard ratios: HRCSD/100 working level months (WLM) = 1.11, 95% confidence interval (1.01; 1.22) and HRCeVD/100 WLM = 1.25 (1.09; 1.43), respectively]. A nonsignificant exposure-risk relationship was observed for every type of cumulative ionizing radiation exposure and every end point [e.g., HRCSD/100WLM = 1.43 (0.71; 2.87)]. The adjustment for each CSD risk factor did not substantially change the exposure-risk relationships. When the model was adjusted for overweight, hypertension, diabetes, hypercholesterolemia and smoking status, the HR/100WLM for CSD, for example, was equal to 1.21 (0.54; 2.75); and when it was adjusted for risk factors selected with the Akaike information criterion, it was equal to 1.44 (0.66; 3.14). To our knowledge, this is the first study to use a uranium miner cohort to consider the major standard CSD risk factors in assessing the relationships between ionizing radiation exposure and the risk of death from these diseases. These results suggest that the significant relationship between CeVD risk and radon exposure observed in the total French cohort is probably not affected by the CSD risk factors. Extending the collection of information about CSD risk factors to a larger subsample would be useful to confirm this result.