Lung cancer risk due to radon in dwellings—evaluation of the epidemiological knowledge

Meta-analysis of case-control studies on the relationship between lung cancer and indoor radon exposure

Indoor exposure to natural radon is a factor that influences lung cancer risk worldwide. The present study includes a meta-analysis of epidemiological data on the relationship between lung cancer and indoor radon. Altogether, 31 case-control studies with 20,703 cases, 34,518 controls and 140 individual odds ratio (OR) estimates are included in the meta-analysis. Weighted median OR was calculated for five radon intervals. The following parameters were used for the weighting: standard error of OR, duration of radon concentration measurement, and relative number of controls in reference intervals. The dependence of the weighted median OR on the radon concentration was estimated applying linear non-threshold and threshold models. The results obtained suggest a significant linear no-threshold exposure-effect relationship for radon concentrations above 100 Bq/m³, with a slope of 0.14 (95% confidence interval 0.08-0.21) per 100 Bq/m³.

Meta-analysis of thirty-two case-control and two ecological radon studies of lung cancer

A re-analysis has been carried out of thirty-two case-control and two ecological studies concerning the influence of radon, a radioactive gas, on the risk of lung cancer. Three mathematically simplest dose-response relationships (models) were tested: constant (zero health effect), linear, and parabolic (linear-quadratic). Health effect end-points reported in the analysed studies are odds ratios or relative risk ratios, related either to morbidity or mortality. In our preliminary analysis, we show that the results of dose-response fitting are qualitatively (within uncertainties, given as error bars) the same, whichever of these health effect end-points are applied. Therefore, we deemed it reasonable to aggregate all response data into the so-called Relative Health Factor and jointly analysed such mixed data, to obtain better statistical power. In the second part of our analysis, robust Bayesian and classical methods of analysis were applied to this combined dataset. In this part of our analysis, we selected different subranges of radon concentrations. In view of substantial differences between the methodology used by the authors of case-control and ecological studies, the mathematical relationships (models) were applied mainly to the thirty-two case-control studies. The degree to which the two ecological studies, analysed separately, affect the overall results when combined with the thirty-two case-control studies, has also been evaluated. In all, as a result of our meta-analysis of the combined cohort, we conclude that the analysed data concerning radon concentrations below ~1000 Bq/m3 (~20 mSv/year of effective dose to the whole body) do not support the thesis that radon may be a cause of any statistically significant increase in lung cancer incidence.

Pooled Bayesian analysis of twenty-eight studies on radon induced lung cancers

The influence of ionizing radiation of (222)Rn and its progeny on lung cancer risks that were published in 28 papers was re-analyzed using seven alternative dose-response models. The risks of incidence and mortality were studied in two ranges of low annual radiation dose: 0-70 mSv per year (391 Bq m(-3)) and 0-150 mSv per year (838 Bq m(-3)). Assumption-free Bayesian statistical methods were used. The analytical results demonstrate that the published incidence and mortality data do not show that radiation dose is associated with increased risk in this range of doses. This conclusion is based on the observation that the model assuming no dependence of the lung cancer induction on the radiation doses is at least ∼90 times more likely to be true than the other models tested, including the linear no-threshold (LNT) model.

Lung cancer and environmental chemical exposure: a review of our current state of knowledge with reference to the role of hormones and hormone receptors as an increased risk factor for developing lung cancer in man

Lung cancer is a dominant cause of cancer mortality. The etiology of lung cancer is mainly related to cigarette smoking, airborne genotoxic carcinogens, and arsenic, but its sex-specific incidence suggests that other mechanisms, such as hormones, may also be involved in the process of carcinogenesis. A number of agents commonly present in the living environment can have dual biological effects: not only are they genotoxic / carcinogenic, but they are also hormonally active as xenoestrogens. This dualism may explain sex-specific differences reported in both types and incidence of lung cancer. In a novel approach to investigate the complexity of lung cancer, etiology, including systems biology, will be used as a tool for a simultaneous interpretation of measurable environmental and biological parameters. Using this approach, the etiology of human lung cancer can be more thoroughly investigated using the available data from oncology and environmental health. The information gained could be applied in the introduction of preventive measures, in personalized medicine, and in more relevant legislation, which should be adjusted to reflect the current knowledge on the complex environmental interactions underlying this life-threatening disease.