Indoor radon exposure and excess of lung cancer mortality: the case of Mexico-an ecological study.

Radon is a radioactive gas that can migrate from soils and rocks and accumulate in indoor areas such as dwellings and buildings. Many studies have shown a strong association between the exposure to radon, and its decay products, and lung cancer (LC), particularly in miners. In Mexico, according to published surveys, there is evidence of radon exposure in large groups of the population, nevertheless, only few attention has been paid to its association as a risk factor for LC. The aim of this ecological study is to evaluate the excess risk of lung cancer mortality in Mexico due to indoor radon exposure. Mean radon levels per state of the Country were obtained from different publications and lung cancer mortality was obtained from the National Institute of Statistics, Geography and Informatics for the period 2001-2013. A model proposed by the International Commission on Radiological Protection to estimate the annual excess risk of LC mortality (per 105 inhabitants) per dose unit of radon was used. The average indoor radon concentrations found rank from 51 to 1863 Bq m-3, the higher average dose exposure found was 3.13 mSv year-1 in the north of the country (Chihuahua) and the mortality excess of LC cases found in the country was 10 ± 1.5 (range 1-235 deaths) per 105 inhabitants. The highest values were found mainly in the Northern part of the country, where numerous uranium deposits are found, followed by Mexico City, the most crowded and most air polluted area in the country. A positive correlation (r = 0.98 p < 0.0001) was found between the excess of LC cases and the dose of radon exposure. Although the excess risk of LC mortality associated with indoor radon found in this study was relatively low, further studies are needed in order to accurately establish its magnitude in the country.

Solid cancer risk dependence on the Pasquill-Gifford atmospheric stability classes in a radiological event.

In a radiological event, the lack of preliminary information about the site of explosion and the difficulty in predicting the accurate path and distribution of radioactive plumes makes it difficult to predict expected health effects of exposed individuals. So far, in such a health evaluation, radiation-induced stochastic health effects such as cancer are not included. The Pasquill-Gifford atmospheric classes generally allow connecting atmospheric stability with dispersion of radioactive contaminants to the environment. In this work, an environmental release of radioactive Cs-137 was simulated and the resulting relative risk for solid cancer incidence among the affected population calculated. The HotSpot health physics code was used to simulate the radioactive atmospheric dispersion and calculate the Total Effective Dose Equivalent (TEDE), which was then used to estimate the relative risk of cancer incidence. The main results from this work suggest that the relative cancer risk and atmospheric stability classes are linked by differences in the TEDE. Such a finding may support triage, because it adds additional information on the potentially affected population at the early stages of an emergency response.

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.

Quantitative health impact of indoor radon in France.

Radon is the second leading cause of lung cancer after smoking. Since the previous quantitative risk assessment of indoor radon conducted in France, input data have changed such as, estimates of indoor radon concentrations, lung cancer rates and the prevalence of tobacco consumption. The aim of this work was to update the risk assessment of lung cancer mortality attributable to indoor radon in France using recent risk models and data, improving the consideration of smoking, and providing results at a fine geographical scale. The data used were population data (2012), vital statistics on death from lung cancer (2008-2012), domestic radon exposure from a recent database that combines measurement results of indoor radon concentration and the geogenic radon potential map for France (2015), and smoking prevalence (2010). The risk model used was derived from a European epidemiological study, considering that lung cancer risk increased by 16% per 100 becquerels per cubic meter (Bq/m3) indoor radon concentration. The estimated number of lung cancer deaths attributable to indoor radon exposure is about 3000 (1000; 5000), which corresponds to about 10% of all lung cancer deaths each year in France. About 33% of lung cancer deaths attributable to radon are due to exposure levels above 100 Bq/m3. Considering the combined effect of tobacco and radon, the study shows that 75% of estimated radon-attributable lung cancer deaths occur among current smokers, 20% among ex-smokers and 5% among never-smokers. It is concluded that the results of this study, which are based on precise estimates of indoor radon concentrations at finest geographical scale, can serve as a basis for defining French policy against radon risk.

The conversion of exposures due to radon into the effective dose: the epidemiological approach.

The risks and dose conversion coefficients for residential and occupational exposures due to radon were determined with applying the epidemiological risk models to ICRP representative populations. The dose conversion coefficient for residential radon was estimated with a value of 1.6 mSv year-1 per 100 Bq m-3 (3.6 mSv per WLM), which is significantly lower than the corresponding value derived from the biokinetic and dosimetric models. The dose conversion coefficient for occupational exposures with applying the risk models for miners was estimated with a value of 14 mSv per WLM, which is in good accordance with the results of the dosimetric models. To resolve the discrepancy regarding residential radon, the ICRP approaches for the determination of risks and doses were reviewed. It could be shown that ICRP overestimates the risk for lung cancer caused by residential radon. This can be attributed to a wrong population weighting of the radon-induced risks in its epidemiological approach. With the approach in this work, the average risks for lung cancer were determined, taking into account the age-specific risk contributions of all individuals in the population. As a result, a lower risk coefficient for residential radon was obtained. The results from the ICRP biokinetic and dosimetric models for both, the occupationally exposed working age population and the whole population exposed to residential radon, can be brought in better accordance with the corresponding results of the epidemiological approach, if the respective relative radiation detriments and a radiation-weighting factor for alpha particles of about ten are used.

Lung cancer incidence associated with radon exposure in Norwegian homes. / Lungekreftforekomst knyttet til radoneksponering i norske boliger.

BACKGROUND: Radioactive radon gas is generated from uranium and thorium in underlying rocks and seeps into buildings. The gas and its decay products emit carcinogenic radiation and are regarded as the second most important risk factor for lung cancer after active tobacco smoking. The average radon concentration in Norwegian homes is higher than in most other Western countries. From a health and cost perspective, it is important to be able to quantify the risk of lung cancer posed by radon exposure. MATERIAL AND METHOD: We estimated the radon-related risk of lung cancer in Norway based on risk estimates from the largest pooled analysis of European case-control studies, combined with the hitherto largest set of data on radon concentration measurements in Norwegian homes. RESULTS: Based on these estimates, we calculate that radon is a contributory factor in 12 % of all cases of lung cancer annually, assuming an average radon concentration of 88 Bq/m3 in Norwegian homes. For 2015, this accounted for 373 cases of lung cancer, with an approximate 95 % confidence interval of 145 ­ 682. INTERPRETATION: Radon most likely contributes to a considerable number of cases of lung cancer. Since most cases of radon-associated lung cancer involve smokers or former smokers, a reduction of the radon concentration in homes could be a key measure to reduce the risk, especially for persons who are unable to quit smoking. The uncertainty in the estimated number of radon-associated cases can be reduced through a new national radon mapping study with an improved design.

Radon as a risk factor of lung cancer

Radon is the second leading cause of lung cancer after smoking. Indoor radon concentration poses a significant and potentially subject to the prevention risk factor of lung cancer development. The paper present the history of studies assessing occupational and indoor radon exposure and an impact of international organizations for raise public and political awareness about the consequences of long term exposure to residential radon, resulting in the European Directive 2013/59/Euratom of 5 December 2013 laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation.

[Ecological-hygienic evaluation of the environment of territories being adjacent to decultivated uranium mines].

On the territory of Kazakhstan there are uranium deposits, many ofwhich are in mothballed since times of perestroika. Often, the mines are flooded and represent a "time-delay bomb". Inside of mines various there are accumulated gases of both organic and inorganic nature, periodically thrown out and adversely affecting on the health of local populations. The aim of the study was the investigation of the state of the environment of Esilsky district of the Akmola region by common pollutants and chemicals. As the basic variable for the investigation of ambient air there was accepted the maximum one-time concentration of suspended substances, phenol, nitrogen dioxide, sulfur dioxide. The results were evaluated in relation to the MPC for the analyzed substance in the air according to maximal single MPC (MPCms) and daily average MPC (MPCda). The content of metals in the water was determined with the use of spectrophotometer PD-303S. Evaluation of the results was executed in relation of the MPC of substances in water, by means of the comparison with the requirements of Federal standards for drinking water, samples from drinking water sources. There were executed calculations of the overall index of water pollution (IWVgen), the index of water pollution by heavy metals (IWVhm). Chemical analysis of soil was carried out with the use of spectrophotometer PD- 303S (Japan), the photometer expert-003 "Ekoniks". Evaluation of the results was carried out with the respect to the MPC in the soil, the toxicity of all components. Summarizing soil pollution index was evaluated for metals contained in the soil at the level of more than or equal to 1 MAC. The settlement Krasnogorskiy and the village of Kalachi were found to be characterized by a low level of air pollution, increased rigidity of drinking water exceeded the maximum permissible concentrations of copper by 3.45 times and chloride by 1.17 times in the soil cover.

Incidence rates of chronic lymphocytic leukemia in US states are associated with residential radon levels.

AIM: Environmental risk factors for chronic lymphocytic leukemia (CLL) have not been consistently identified. An etiologic role for ionizing radiation in CLL is controversial. Because most of the ionizing radiation to which individuals are exposed comes from radon at home, we examined CLL incidence rates in relation to residential radon levels. METHODS: We used population-based rates for CLL for US states from 2007 to 2011 and measurements of residential radon made by the US Environmental Protection Agency. RESULTS: Incidence rates for CLL were significantly correlated with residential radon levels among whites (both genders together and each gender separately; p < 0.005) and among blacks (p < 0.05). CONCLUSION: We speculate that radon increases CLL risk and that the mechanisms may be similar to those by which radon causes lung cancer.

Lung cancer risk from radon exposure in dwellings in Sweden: how many cases can be prevented if radon levels are lowered?

PURPOSE: Residential exposure to radon is considered to be the second cause of lung cancer after smoking. The purpose of this study was to estimate the number of lung cancer cases prevented from reducing radon exposure in Swedish dwellings. METHODS: Measurements of indoor radon are available from national studies in 1990 and 2008 with 8992 and 1819 dwellings, considered representative of all Swedish dwellings. These data were used to estimate the distribution of radon in Swedish dwellings. Lung cancer risk was assumed to increase by 16% per 100 becquerels per cubic meter (Bq/m(3)) indoor air radon. Estimates of future and saved cases of lung cancer were performed at both constant and changed lung cancer incidence rates over time. RESULTS: The arithmetic mean concentration of radon was 113 Bq/m(3) in 1990 and 90 Bq/m(3) in 2008. Approximately 8% of the population lived in houses with >200 Bq/m(3). The estimated current number of lung cancer cases attributable to previous indoor radon exposure was 591 per year, and the number of future cases attributable to current exposure was 473. If radon levels above 100 Bq/m(3) are lowered to 100 Bq/m(3), 183 cases will be prevented. If levels >200 Bq/m(3) are lowered to 140 Bq/m(3) (mean in the present stratum 100-200 Bq/m(3)), 131 cases per year will be prevented. CONCLUSIONS: Although estimates are somewhat uncertain, 35-40% of the radon attributed lung cancer cases can be prevented if radon levels >100 Bq/m(3) are lowered to 100 Bq/m(3).

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.

Lung cancer mortality and radon concentration in a chronically exposed neighborhood in Chihuahua, Mexico: a geospatial analysis.

This study correlated lung cancer (LC) mortality with statistical data obtained from government public databases. In order to asses a relationship between LC deaths and radon accumulation in dwellings, indoor radon concentrations were measured with passive detectors randomly distributed in Chihuahua City. Kriging (K) and Inverse-Distance Weighting (IDW) spatial interpolations were carried out. Deaths were georeferenced and Moran's I correlation coefficients were calculated. The mean values (over n = 171) of the interpolation of radon concentrations of deceased's dwellings were 247.8 and 217.1 Bq/m(3), for K and IDW, respectively. Through the Moran's I values obtained, correspondingly equal to 0.56 and 0.61, it was evident that LC mortality was directly associated with locations with high levels of radon, considering a stable population for more than 25 years, suggesting spatial clustering of LC deaths due to indoor radon concentrations.

[The methods of assessment of health risk from exposure to radon and radon daughters].

The critical analysis of existing models of the relationship dose-effect (RDE) for radon exposure on human health has been performed. Conclusion about the necessity and possibility of improving these models has been made. A new improved version ofthe RDE has been developed. A technique for assessing the human health risk of exposure to radon, including the method for estimating of exposure doses of radon, an improved model of RDE, proper methodology risk assessment has been described. Methodology is proposed for the use in the territory of Russia.

On the informative value of community-based indoor radon values in relation to lung cancer.

BACKGROUND: Radon is a radioactive gas and a major risk factor for lung cancer (LC). METHODS: We investigated the dose-response relationship between radon and LC risk in the International Lung Cancer Consortium with 8927 cases and 5562 controls from Europe, North America, and Israel, conducted between 1992 and 2016. Spatial indoor radon exposure in the residential area (sIR) obtained from national surveys was linked to the participants' residential geolocation. Parametric linear and spline functions were fitted within a logistic regression framework. RESULTS: We observed a non-linear spatial-dose response relationship for sIR < 200 Bq/m3. The lowest risk was observed for areas of mean exposure of 58 Bq/m3 (95% CI: 56.1-59.2 Bq/m3). The relative risk of lung cancer increased to the same degree in areas averaging 25 Bq/m3 (OR = 1.31, 95% CI: 1.01-1.59) as in areas with a mean of 100 Bq/m3 (OR = 1.34, 95% CI: 1.20-1.45). The strongest association was observed for small cell lung cancer and the weakest for squamous cell carcinoma. A stronger association was also observed in men, but only at higher exposure levels. The non-linear association is primarily observed among the younger population (age < 69 years), but not in the older population, which can potentially represent different biological radiation responses. CONCLUSIONS: The sIR is useful as proxy of individual radon exposure in epidemiological studies on lung cancer. The usual assumption of a linear, no-threshold dose-response relationship, as can be made for individual radon exposures, may not be optimal for sIR values of less than 200 Bq/m3.

Lung cancer mortality attributable to residential radon: a systematic scoping review.

After smoking, residential radon is the second risk factor of lung cancer in general population and the first in never-smokers. Previous studies have analyzed radon attributable lung cancer mortality for some countries. We aim to identify, summarize, and critically analyze the available data regarding the mortality burden of lung cancer due to radon, performing a quality assessment of the papers included, and comparing the results from different countries. We performed a systematic scoping review using the main biomedical databases. We included original studies with attributable mortality data related to radon exposure. We selected studies according to specific inclusion and exclusion criteria. PRISMA 2020 methodology and PRISMA Extension for Scoping Reviews requirements were followed. Data were abstracted using a standardized data sheet and a tailored scale was used to assess quality. We selected 24 studies describing radon attributable mortality derived from 14 different countries. Overall, 13 studies used risk models based on cohorts of miners, 8 used risks from residential radon case-control studies and 3 used both risk model options. Radon geometric mean concentration ranged from 11 to 83 Becquerels per cubic meter (Bq/m3) and the population attributable fraction (PAF) ranged from 0.2 to 26%. Studies performed in radon prone areas obtained the highest attributable mortality. High-quality publications reported PAF ranging from 3 to 12% for residential risk sources and from 7 to 25% for miner risk sources. Radon PAF for lung cancer mortality varies widely between studies. A large part of the variation is due to differences in the risk source used and the conceptual description of radon exposure assumed. A common methodology should be described and used from now on to improve the communication of these results.

Regression models for the effects of exposure rate and cumulative exposure.

Epidemiologic studies that collect detailed exposure histories often incorporate this information into a regression model through a time-dependent cumulative exposure metric. This summary metric obscures variations in exposure rates among people and within persons over time. To disentangle the effects of cumulative exposure and exposure rate, one standard approach is to simultaneously model both cumulative exposure and average exposure rate. We propose an alternative regression model that uses a person's detailed exposure history information to describe the effect of the history of exposure increments on the relative hazard function. We illustrate this approach using data from a cohort study of radon exposure and lung cancer mortality among uranium miners. Compared with a standard cumulative exposure-average exposure rate model, our proposed approach yielded somewhat stronger evidence that the radon-lung cancer mortality association is modified by exposure rate. At low exposure rates, the estimated excess relative hazard per 100 working-level months was 0.63 (95% confidence interval = 0.32-1.37) under the standard approach, whereas under the proposed approach it was 1.23 (0.53-3.76). The proposed approach may provide better understanding of relationships between a protracted exposure and disease and is readily implemented using existing statistical software.

Lung cancer in a Czech cohort exposed to radon in dwellings--50 years of follow-up.

The presented study reports lung cancer mortality in a cohort of 11 842 subjects exposed to high levels of radon covering the period 1961-2010. Exposure estimates were based on one year measurements of radon progeny in most houses of the study area (72%), missing values in the studied area were replaced by measurements in proxy houses (9%) and exposures outside the area (19%) were based on country radon mapping. Mean concentration of 448 Bq m(-3) in the study is higher than the country mean by a factor of 5. By 2010, a total of 293 lung cancers were observed. The risk is significantly related to cumulated exposure with ERR/100Bq m(-3) 0.11 (90%CI: 0.04 - 0.25). This value is consistent with the risk coefficients in other indoor studies and also with the risks observed among uranium miners. The present follow-up demonstrated that increased incidence of lung cancer depends mainly on exposure from previous 5-19 years. The relative risk of lung cancer in the present study derived from this model is 1.53 (90%CI: 1.39 - 1.69).

How to ensure that national radon survey results are useful for public health practice.

Exposure to radon gas increases the risk of lung cancer. Preliminary national survey data collected by Health Canada indicate that approximately 10% of households exceed the recommended federal long-term guideline of 200 Bq/m3. However, results to date have been reported for large geographic areas in broad measurement categories. Given that Health Canada recommends the most rapid remediation for buildings with the highest concentrations, such reporting makes it challenging for public health authorities to target interventions to communities at the highest risk. Here we use data from a survey in British Columbia to illustrate how improved spatial resolution and more refined concentration categories would be valuable for prioritizing the use of limited public health resources. We encourage Health Canada in future to provide more specific, community-level information that can be used to inform local policy and to engage building owners in radon testing and remediation.

Awareness and perceptions of the risks of exposure to indoor radon: a population-based approach to evaluate a radon awareness and testing campaign in England and Wales.

The current study aimed to evaluate the locally directed radon roll-out program that was conducted between 2001 and 2005 in England and Wales to increase radon awareness and testing rates. A representative sample of 1,578 residents aged 16 and older were interviewed who lived in radon-affected areas of 15 local authorities in England and Wales that were eligible for participation in the program. The study systematically sampled across participating and nonparticipating local authorities, "actionable" and "nonactionable" radon-affected areas, and geographic regions with different campaign histories (Wales, Southwest England, and the rest of England). As a multistage sampling strategy was used, the data were analyzed from a multilevel perspective. This study found that participants living in participating local authorities had higher levels of awareness and were more likely to have tested their home for radon than participants living in nonparticipating local authorities. Similar results were found for participants living in "actionable" areas as compared to those living in "nonactionable" radon-affected areas. The study further found that radon awareness and testing rates were the highest in Southwest England and the lowest in Wales. This study suggests that the radon roll-out program has been effective in raising awareness and testing rates, and that ongoing domestic radon campaigns in Southwest England may have raised radon awareness and testing in these areas, showing important reinforcement effects of multiple risk communication campaigns.

[Case-control study of lung cancer and combined home and work radon exposure in the town of Lermontov].

Relation between the risk of lung cancer and combined home and work indoor radon exposure was studied on the example of the population of Lermontov town (Stavropol Region, Russia). The town is situated in the former uranium mining area. Case (121 lung cancer cases) and control (196 individuals free of lung cancer diagnosis) groups of the study included both ex-miners and individuals that were not involved in the uranium industry. Home and work radon exposures were estimated using archive data as well as contemporary indoor measurements. The results of our study support the conclusion about the effect of radon exposure on the lung cancer morbidity.