Risk of lung cancer and residential radon in China: pooled results of two studies

Studies of radon-exposed underground miners predict that residential radon is the second leading cause of lung cancer mortality; however, case-control studies of residential radon have not provided unambiguous evidence of an association. Owing to small expected risks from residential radon and uncertainties in dosimetry, large studies or pooling of multiple studies are needed to fully evaluate effects. We pooled data from 2 case-control studies of residential radon representing 2 large radon studies conducted in China. The studies included 1050 lung cancer cases and 1996 controls. In the pooled data, odds ratios (OR) increased significantly with greater radon concentration. Based on a linear model, the OR with 95% confidence intervals (CI) at 100 Becquerel/cubic-meter (Bq/m(3)) was 1.33 (1.01,1.36). For subjects resident in the current home for 30 years or more, the OR at 100 Bq/m(3) was 1.32 (1.07,1.91). Results across studies were consistent with homogeneity. Estimates of ORs were similar to extrapolations from miner data and consistent with published residential radon studies in North American and Europe, suggesting long-term radon exposure at concentrations found in many homes increases lung cancer risk.     

Potential lung cancer risk from indoor radon exposure

The contribution of radon daughter exposure to excess lung cancer in underground miners is universally accepted. These miners received exposures from tens to thousands of WLM in a relatively few years. Although the miners were also exposed to other noxious agents in mines, the appearance of the excess lung cancer mortality in several types of mines and the increase with increasing exposure provide convincing evidence of the role of radon as the carcinogen. It is conceivable that exposures to radon at an average concentration of one to two pCi/liter, the levels for a majority of homes, might not produce excess lung cancers. This would require that a lifetime exposure at low concentrations produce a different response from that of a few years at higher levels for the miners. This is unlikely but not impossible. The current environmental epidemiology is of varying quality. The better studies may give some answers in a few years. These studies are more likely to establish an upper limit of risk than to provide an exposure-response model. Present risk estimates cannot be used accurately in estimating the overall lung cancer risk to the US population, since there are no good data on average exposure and exposure distribution. For example, the number of homes above the EPA guideline of four pCi/liter may range from two million to 10 million. An estimate of the actual radon exposure in the US may be forthcoming from a planned EPA survey, but these data will not be available for a few years. In the conservative tradition of radiation protection, indoor radon exposures in homes are estimated to produce a number of excess lung cancers in the population. One estimate by the NCRP is about 10,000 deaths per year in the US, for an average annual estimated exposure of 0.2 WLM (about one pCi/liter). The National Academy of Sciences (BEIR IV) estimates 13,000 deaths for the same exposure, and the EPA's estimate is 5,000 to 20,000.     

Residential radon and lung cancer in never smokers. A systematic review

Radon exposure is considered the second cause of lung cancer and the first in never smokers. We aim to assess the effect of residential radon exposure on the risk of lung cancer in never smokers through a systematic review applying predefined inclusion and exclusion criteria. 14 Studies were included. Some of them point to a relationship between residential radon and lung cancer while others show no association. Further studies are necessary to test this association and to assess if other risk factors such as environmental tobacco smoke could modify the effect of residential radon exposure on lung cancer.     

云南曲靖肺癌高发区氡气浓度与肺癌发病率的关系

目的:探讨肺癌高发区氡气浓度与肺癌发病率是否存在相关性.方法:采用中国辐射防护研究所生产的RLM-L型连续测氡仪,分别对处于宣威、富源肺癌高发区的7个农民肺癌家庭进行氡气监测.同期对宣威肺癌高发区的3个办公区、肺癌低发区的2个农民肺癌家庭以及曲靖麒麟区肺癌低发区的4个健康人口家庭共16个点进行氡气浓度监测.结果:宣威、富源肺癌高发区中6个点氡气浓度均远远超过国家环境标准的200 Bq/L,赋有"世界肺癌村"之称的来宾镇虎头村,其村北、村西、村南3个肺癌家庭氡气浓度也相对较高,但均小于200 Bq/L;其余7个监测点包括1个肺癌高发区、3个肺癌低发区的肺癌家庭以及麒麟区3个健康家庭氡气浓度均低于50 Bq/L.结论:宣威、富源不同地区氡气浓度与肺癌发病率存在一定相关性,氡气浓度高则肺癌发病率也高.宣威、富源肺癌高发病率除了与其特有的环境地理因素、遗传、基因易感性等相关外,也与氡气污染有关.     

RELATED GENES IN LUNG CANCER TISSUES ASSOCIATED WITH RESIDENTIAL HIGH RADON EXPOSURE

As science and technology have been getting more and more improvement, people begin to pay more attention on their environment, especially the natural radiation. Epidemiological studies on underground miners showed that the inhalation of radon progeny is associated with an increased risk of lung cancer[1]. Radon in dwellings is the dominant source of exposure to ionizing radiation in most countries[2]. It was assessed that 10%~15% of residential lung cancer may be associated with radon[3]. The…     

p53 Mutations in lung cancer associated with residential radon exposure.

Unusual mutation patterns in lung tumors among underground miners have been indicated, suggesting radon-specific alterations in the genome, but the data are not consistent. To investigate the association between residential radon exposure and p53 mutations in lung tumors, we performed a study on cases from a nation-wide population-based investigation in Sweden. Our study included 83 nonsmoking lung cancer cases and 250 smoking lung cancer cases, diagnosed 1980-1984, with a time-weighted average radon exposure over 140 Bq/m3 or up to 50 Bq/m3. Radon was measured in dwellings occupied by the study subjects at some time since 1947. Information on smoking habits and other risk factors was obtained from questionnaires. After exclusions because of the initiation of treatment or insufficient material, the p53-status of 243 tumors was determined using PCR-single-stranded conformation polymorphism analysis and sequencing determination of exons 5-8. The overall mutation prevalence was 23.9%. An increased mutation prevalence was suggested among those with high exposure to residential radon [odds ratio (OR), 1.4; 95% CI, 0.7-2.6], especially among nonsmokers (OR, 3.2; 95% CI, 0.7-15.5), but no specific mutational pattern was indicated. Furthermore, the mutation prevalence seemed to be higher among smoking lung cancer cases than among nonsmoking cases (OR, 2.1; 95% CI, 0.9-5.0), and particularly among those smoking less than 10 cigarettes per day. It may be concluded that residential exposure to radon seems to contribute to a higher mutation prevalence of the p53 gene in lung tumors.     

Case-control study of residential radon and lung cancer among New Jersey women

To evaluate the association of indoor radon exposure with lung cancer risk, yearlong alpha track detector measurements of radon were conducted in dwellings which had been occupied for at least 10 years by 433 New Jersey female lung cancer cases and 402 controls who were subjects in a larger population-based study. Adjusted odds ratios were 1.1 (90% confidence interval, 0.79-1.7), 1.3 (90% confidence interval, 0.62-2.9), and 4.2 (90% confidence interval, 0.99-17.5) for exposures of 1.0-1.9, 2.0-3.9, and 4.0-11.3 pCi/liter, respectively, relative to exposures of less than 1.0 pCi/liter, showing a significant trend (1-sided P = 0.04) with increasing radon concentration. The trend was strongest among light smokers (less than 15 cigarettes/day, 1-sided P = 0.01). The trend for lung cancer risk with estimated cumulative radon exposure was slightly weaker (1-sided P = 0.09). The increase in relative risk for each unit of cumulative exposure, 3.4% (90% confidence interval 0.0-8.0%) per working level month, was consistent with the range of 0.5-4.0% per working level month generally reported for underground miner studies, supporting the extrapolation of the occupational data to the residential setting. However, the possibility of selection biases, the small number of high exposures, and other uncertainties necessitate caution in interpretation of these data.     

Residential radon exposure and lung cancer: an overview of published studies.

A possible link between presumed or measured household radon exposure and lung cancer is reviewed on the basis of published epidemiologic studies. Evidence of a link is reported as a result of studies in Sweden; findings are inconsistent elsewhere. A number of methodological problems were found. Many of the studies are ecological in design and are, therefore, primarily hypothesis generating. A number of studies lack any data on the number of lung cancers and are, therefore, difficult to evaluate. Some other studies provide results that are internally inconsistent. Of the case/control studies, there are many with minimal or no information on active and passive smoking, occupation, family history of cancer, and diet. The case/control studies are generally small in size and of low statistical power. Exposure classifications are nonstandardized, inconsistent in their findings, and often gross in their characterization of radon concentrations. Relatively few of the studies actually measured radon exposure. Some of the studies showed significant positive associations either with geological characteristics, water supply contamination, or house type. No significant associations were found with residence near uranium or radium processing waste. Where radon levels were measured, a relatively small percentage of studies found a statistically significant positive association with lung cancer. Overall, the evidence for an association between residential radon exposure and lung cancer is weak. There is a need for a more decisive case/control epidemiologic study of this problem.     

Residential radon and lung cancer risk: an updated meta- analysis of case-control studies

Background: Numbers of epidemiological studies assessing residential radon exposure and risk of lung cancerhave yielded inconsistent results. Methods: We therefore performed a meta-analysis of relevant published casecontrolstudies searched in the PubMed database through July 2011 to examine the association. The combinedodds ratio (OR) were calculated using fixed- or random-effects models. Subgroup and dose-response analyseswere also performed. Results: We identified 22 case-control studies of residential radon and lung cancer riskinvolving 13,380 cases and 21,102 controls. The combined OR of lung cancer for the highest with the lowestexposure was 1.29 (95% CI 1.10-1.51). Dose-response analysis showed that every 100 Bq/m3 increment inresidential radon exposure was associated with a significant 7% increase in lung cancer risk. Subgroup analysisdisplayed a more pronounced association in the studies conducted in Europe. Studies restricted to female ornon-smokers demonstrated weakened associations between exposure and lung cancer. Conclusions: This metaanalysisprovides new evidence supporting the conclusion that residential exposure to radon can significantlyincrease the risk of lung cancer in a dose-response manner.     

Indoor air pollution and risk of lung cancer among Chinese female non-smokers

Purpose

To investigate indoor particulate matter (PM) level and various indoor air pollution exposure, and to examine their relationships with risk of lung cancer in an urban Chinese population, with a focus on non-smoking women.

Methods

We conducted a case–control study in Taiyuan, China, consisting of 399 lung cancer cases and 466 controls, of which 164 cases and 218 controls were female non-smokers. Indoor PM concentrations, including PM₁, PM_2.5, PM₇, PM₁₀, and TSP, were measured using a particle mass monitor. Unconditional logistic regression models were used to calculate odds ratios (ORs) and 95 % confidence intervals after adjusting for age, education, annual income, and smoking.

Results

Among non-smoking women, lung cancer was strongly associated with multiple sources of indoor air pollution 10 years ago, including heavy exposure to environmental tobacco smoke at work (aOR = 3.65), high frequency of cooking (aOR = 3.30), and solid fuel usage for cooking (aOR = 4.08) and heating (aOR_{coal stove} = 2.00). Housing characteristics related to poor ventilation, including single-story, less window area, no separate kitchen, no ventilator, and rarely having windows open, are associated with lung cancer. Indoor medium PM_2.5 concentration was 68 μg/m³, and PM₁₀ was 230 μg/m³. PM levels in winter are strongly correlated with solid fuel usage for cooking, heating, and ventilators. PM₁ levels in cases are more than 3 times higher than that in controls. Every 10 μg/m³ increase in PM₁ is associated with 45 % increased risk of lung cancer.

Conclusions

Indoor air pollution plays an important role in the development of lung cancer among non-smoking Chinese women.     

中国肺癌流行病学

近50年来,世界上很多国家的肺癌发病率和死亡率呈急剧上升趋势。2002年全世界的肺癌新病例大约为135万,死亡118万,居恶性肿瘤第1位。根据我国居民死因调查的结果,肺癌死亡率从20世纪70年代中期至90年代初期的20年增加近1．5倍,是增长最快的恶性肿瘤。     

Residential radon exposure, diet and lung cancer: a case-control study in a Mediterranean region

We performed a case-control study in Lazio, a region in central Italy characterized by high levels of indoor radon, Mediterranean climate and diet. Cases (384) and controls (404) aged 35-90 years were recruited in the hospital. Detailed information regarding smoking, diet and other risk factors were collected by direct interview. Residential history during the 30-year period ending 5 years before enrollment was ascertained. In each dwelling, radon detectors were placed in both the main bedroom and the living room for 2 consecutive 6-month periods. We computed odds ratios (ORs) and 95% confidence intervals (CIs) for time-weighted radon concentrations using both categorical and continuous unconditional logistic regression analysis and adjusting for smoking, diet and other variables. Radon measurements were available from 89% and 91% of the time period for cases and controls, respectively. The adjusted ORs were 1.30 (1.03-1.64), 1.48 (1.08-2.02), 1.49 (0.82-2.71) and 2.89 (0.45-18.6) for 50-99, 100-199, 200-399 and 400+ Bq/m(3), respectively, compared with 0-49 Bq/m(3) (OR = 1; 0.56-1.79). The excess odds ratio (EOR) per 100 Bq/m(3) was 0.14 (-0.11, 0.46) for all subjects, 0.24 (-0.09, 0.70) for subjects with complete radon measurements and 0.30 (-0.08, 0.82) for subjects who had lived in 1 or 2 dwellings. There was a tendency of higher risk estimates among subjects with low-medium consumption of dietary antioxidants (EOR = 0.32; -0.19, 1.16) and for adenocarcinoma, small cell and epidermoid cancers. This study indicates an association, although generally not statistically significant, between residential radon and lung cancer with both categorical and continuous analyses. Subjects with presumably lower uncertainty in the exposure assessment showed a higher risk. Dietary antioxidants may act as an effect modifier.     

Relationship of radioactive radon daughters and cigarette smoking in the genesis of lung cancer in uranium miners

This article documents the study of 383 cases of lung cancer in uranium miners and presents for the first time the relationship of radioactive radon gas and cigarette smoking. There is evidence that alpha radiation from radon gas at exposure levels above 465 working level months (WLM) is a strong contributor to the development of lung cancer. Cigarette smoking plays the most significant role in causing lung tumor; this is also noticed in nonminers who smoke cigarettes. A synergistic or additive effect of these two carcinogens is strongly suggested. The data indicate that small cell tumors develop in younger nonsmoking miners exposed to radon levels above 465 WLM. Lung cancers develop in smoking miners at lower levels of radon exposure than in nonsmoking miners. Based on an average mining experience of 15 years, there is substantial evidence that the present maximum allowable limit of 0.3 working levels (WL), or 4 working level months (WLM) per year, is safe, representing a margin of safety of approximately 10:1. Furthermore, a comparison of these data with the radon levels in some homes, averaging in the neighborhood of 0.025 WL, would indicate that health risks at these levels are negligible. It is suggested that 20 picocuries/liter, which equals 0.10 WL, be the maximum allowable level in homes.     

Indoor residential radon exposure and risk of childhood acute myeloid leukaemia.

Exposure to radon has been identified as a risk factor for lung cancer in uranium miners, but evidence of adverse health effects due to indoor radon exposure is inconsistent. Ecological studies have suggested a correlation between indoor radon levels and leukaemia incidence. We evaluated the risk associated with indoor residential radon exposure within a larger interview-based case-control study of risk factors for childhood acute myeloid leukaemia (AML). A total of 173 cases and 254 controls met the eligibility criteria, and information was collected through telephone interviews with parents and analysis of alpha-track radon detectors placed in the home for a period of 1 year. No association was observed between radon exposure and risk of AML, with adjusted odds ratios of 1.2 (95% confidence interval (CI) 0.7-1.8) for 37-100 Bq m(-3) and 1.1 (95% CI 0.6-2.0) for > 100 Bq m(-3) compared with < 37 Bq m(-3). Although there was an inverse association between radon level and AML risk among children < 2 years at diagnosis, among children > or = 2 years, AML risk was increased among those with higher radon exposure. The observed association after age 2 is most likely due to chance. Overall, there was no association between residential radon and risk of childhood AML.     

Global efforts inconquering lung cancer in China

Lung cancer, the most prevalent and deadly malignancy in the world, poses a particularly critical healthcare challenge to China due to the rapidly increasing new cases and the unique cancer genetics in...