Indoor radon exposure and active and passive smoking in relation to the occurrence of lung cancer

Association Between Smoking and Lipid Profile in Men Aged 35 to 70 Years: Dose-Response Analysis

Dyslipidemia is linked to various health complications, including cardiovascular disease and inflammation. This study aimed to assess the association between smoking and lipid profile in the Tabari cohort population. Data from the Tabari Cohort Study involving 4,149 men were analyzed. A standardized questionnaire collected smoking history, while blood samples measured lipid levels and anthropometric measurements were recorded. Statistical analysis utilized chi-square tests and logistic regression, adjusting for potential confounders. The prevalence of smoking was 893 (21.52%; urban: 20.6%, mountainous: 23.8%, significant level: .024). The adjusted odds ratio (OR) of low high-density lipoprotein (HDL) among smokers 1.48 (95% confidence interval [CI]: 1.25-1.77, p < .001) was the same as non-smokers. The adjusted OR of high low-density lipoprotein (LDL) in men with 1 to 10, 11 to 20, and more than 20 cigarettes per day was 0.95 (95% CI: 0.73-1.25), 1.30 (95% CI: 0.99-1.71), and 2.64 (95% CI: 1.32-5.27) and low HDL was equal to 1.34 (95% CI: 1.06-1.68), 1.61 (95% CI: 1.26-2.05), and 2.24 (95% CI: 1.13-4.42) compared with non-smokers, respectively. The study findings indicate that smoking is associated with lower HDL levels, even after adjusting for potential confounders. The odds of low HDL and high LDL increases with higher smoking intensity. The low HDL and high LDL levels in individuals smoking over 20 cigarettes/day, respectively, show a 2.24-fold and a 2.64-fold increased odds compared to non-smokers. These findings highlight the importance of smoking cessation in relation to lipid profiles and related health risks.

Histologic Lung Cancer Incidence Rates and Trends Vary by Race/Ethnicity and Residential County

INTRODUCTION

Lung cancer incidence is higher among non-Hispanic (NH) blacks than among the NH white and Hispanic populations in the United States. However, national cancer estimates may not always reflect the cancer burden in terms of disparities and incidence in small geographic areas, especially urban-rural disparities. Moreover, there is a gap in the literature regarding rural-urban disparities in terms of cancer histologic type.

METHODS

Using population-based cancer registry data-Surveillance, Epidemiology and End Results and National Program of Cancer Registries data-we present age-adjusted histologic rates and trends by race/ethnicity and residential county location at the time of first cancer diagnosis. Rate ratios were calculated to examine racial/ethnic differences in rates. Annual percent change was calculated to measure changes in rates over time.

RESULTS

We found that declines in squamous cell carcinoma are occurring fastest in metropolitan counties, whereas rates of adenocarcinoma increased fastest in counties nonadjacent to metropolitan areas. Further, although NH black men have increased lung cancer incidence compared with NH white and Hispanic men in all geographic locations, we found that the degree of the disparity increases with increasing rurality of residence. Finally, we discovered that among women whose lung cancer was diagnosed when they were younger than 55 years, the incidence of squamous cell carcinoma and adenocarcinoma was higher for NH blacks than for NH whites.

CONCLUSIONS

Our results highlight disparities among NH blacks in nonadjacent rural areas. These findings may have significant impact for the implementation of smoking cessation and lung cancer screening programs.

Prediction of residential radon exposure of the whole Swiss population: comparison of model-based predictions with measurement-based predictions

Radon plays an important role for human exposure to natural sources of ionizing radiation. The aim of this article is to compare two approaches to estimate mean radon exposure in the Swiss population: model-based predictions at individual level and measurement-based predictions based on measurements aggregated at municipality level. A nationwide model was used to predict radon levels in each household and for each individual based on the corresponding tectonic unit, building age, building type, soil texture, degree of urbanization, and floor. Measurement-based predictions were carried out within a health impact assessment on residential radon and lung cancer. Mean measured radon levels were corrected for the average floor distribution and weighted with population size of each municipality. Model-based predictions yielded a mean radon exposure of the Swiss population of 84.1 Bq/m(3) . Measurement-based predictions yielded an average exposure of 78 Bq/m(3) . This study demonstrates that the model- and the measurement-based predictions provided similar results. The advantage of the measurement-based approach is its simplicity, which is sufficient for assessing exposure distribution in a population. The model-based approach allows predicting radon levels at specific sites, which is needed in an epidemiological study, and the results do not depend on how the measurement sites have been selected.

Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BACKGROUND

Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. We summarize evidence for various indices.

METHODS

Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Data were extracted on design, exposures, histological types and confounder adjustment. RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose-response. Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma ("squamous") and adenocarcinoma ("adeno").

RESULTS

287 studies (20 subsidiary) were identified. Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Relationships were somewhat stronger in later starting and larger studies. RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. Covariate-adjustment little affected RR estimates.

CONCLUSIONS

The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. This emphasises the causal nature of the relationship. Our results quantify the relationships more precisely than previously.

Meta-analysis of studies of passive smoking and lung cancer: effects of study type and continent

BACKGROUND

To calculate a pooled estimate of relative risk (RR) of lung cancer associated with exposure to passive smoking in never smoking women exposed to smoking spouses. This study is an updated meta-analysis that also assesses the differences between estimated risks according to continent and study type using meta-regression.

METHODS

From a total of 101 primary studies, 55 studies are included in this meta-analysis, of which, 7 are cohort studies, 25 population-based case-control and 23 non-population-based case-control studies. Twenty previously published meta-analyses are also reviewed. Fixed and random effect models and meta-regression are used to obtain pooled estimates of RR and P-value functions are used to demonstrate consistency of results.

RESULTS

The pooled RR for never-smoking women exposed to passive smoking from spouses is 1.27 (95% CI 1.17-1.37). The RR for North America is 1.15 (95% CI 1.03-1.28), Asia, 1.31 (95% CI 1.16-1.48) and Europe, 1.31 (1.24-1.52). Sequential cumulative meta-analysis shows no trend. There is no strong evidence of publication bias.

CONCLUSIONS

The abundance of evidence, consistency of finding across continent and study type, dose-response relationship and biological plausibility, overwhelmingly support the existence of a causal relationship between passive smoking and lung cancer.

Indoor radon and lung cancer risk in connecticut and utah

Radon is a well-established cause of lung cancer in miners. Residents of homes with high levels of radon are potentially also at risk. Although most individual studies of indoor radon have failed to demonstrate significant risks, results have generally been consistent with estimates from studies of miners. We studied 1474 incident lung cancer cases aged 40-79 yr in Connecticut, Utah, and southern Idaho. Population controls (n = 1811) were identified by random telephone screening and from lists of Medicare recipients, and were selected to be similar to cases on age, gender, and smoking 10 yr before diagnosis/interview using randomized recruitment. Complete residential histories and information on known lung cancer risk factors were obtained by in-person and telephone interviews. Radon was measured on multiple levels of past and current homes using 12-mo alpha-track etch detectors. Missing data were imputed using mean radon concentrations for informative subgroups of controls. Average radon exposures were lower than anticipated, with median values of 23 Bq/m3 in Connecticut and 45 Bq/m3 in Utah/southern Idaho. Overall, there was little association between time-weighted average radon exposures 5 to 25 yr prior to diagnosis/interview and lung cancer risk. The excess relative risk (ERR) associated with a 100-Bq/m3 increase in radon level was 0.002 (95% CI -0.21, 0.21) in the overall population, 0.134 (95% CI -0.23, 0.50) in Connecticut, and -0.112 (95% CI -0.34, 0.11) in Utah/Idaho. ERRs were higher for some subgroups less prone to misclassification, but there was no group with a statistically significant linear increase in risk. While results were consistent with the estimates from studies of miners, this study provides no evidence of an increased risk for lung cancer at the exposure levels observed.

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.

Passive smoking and lung cancer: a cumulative meta-analysis

OBJECTIVE

To review the epidemiological evidence for the association between passive smoking and lung cancer.

METHOD

Primary studies and meta-analyses examining the relationship between passive smoking and lung cancer were identified through a computerised literature search of Medline and Embase, secondary references, and experts in the field of passive smoking. Primary studies meeting the inclusion criteria were meta-analysed.

RESULTS

From 1981 to the end of 1999 there have been 76 primary epidemiological studies of passive smoking and lung cancer, and 20 meta-analyses. There were 43 primary studies that met the inclusion criteria for this meta-analysis; more studies than previous assessments. The pooled relative risk (RR) for never-smoking women exposed to environmental tobacco smoke (ETS) from spouses, compared with unexposed never-smoking women was 1.29 (95% CI 1.17-1.43). Sequential cumulative meta-analysed results for each year from 1981 were calculated: since 1992 the RR has been greater than 1.25. For Western industrialised countries the RR for never-smoking women exposed to ETS compared with unexposed never-smoking women, was 1.21 (95% CI 1.10-1.33). Previously published international spousal meta-analyses have all produced statistically significant RRs greater than 1.17.

CONCLUSIONS

The abundance of evidence in this paper, and the consistency of findings across domestic and workplace primary studies, dosimetric extrapolations and meta-analyses, clearly indicates that non-smokers exposed to ETS are at increased risk of lung cancer.

IMPLICATIONS

The recommended public health policy is for a total ban on smoking in enclosed public places and work sites.

Models for retrospective quantification of indoor radon exposure in case-control studies

In epidemiologic studies on lung cancer risk due to indoor radon the quantification of individual radon exposure over a long time period is one of the main issues. Therefore, radon measurements in one or more dwellings, which in total have been inhabited by the participants for a sufficient time-period, are necessary as well as consideration of changes of building characteristics and ventilation habits, which influence radon concentration. Given data on 1-y alpha-track measurements and personal information from 6,000 participants of case-control studies in West and East Germany, an improved method is developed to assess individual radon exposure histories. Times spent in different rooms of the dwelling, which are known from a personal questionnaire, are taken into account. The time spent outside the house (average fraction 45%) varies substantially among the participants. Therefore, assuming a substantially lower radon exposure outside the dwelling, the residence time constitutes an important aspect of total radon exposure. By means of an analysis of variance, important determinants of indoor radon are identified, namely constant conditions such as type of house (one family house or multiple dwelling), type of construction (half-timbered, massive construction, lightweight construction), year of construction, floor and type of basement, and changeable conditions such as heating system, window insulation, and airing habits. A correction of measurements in former dwellings by factors derived from the analysis is applied if current living conditions differ from those of the participants at the time when they were living in the particular dwellings. In rare cases the adjustment for changes leads to a correction of the measurements with a factor of about 1.4, but a reduction of 5% on average only. Exposure assessment can be improved by considering time at home and changes of building and ventilation conditions that affect radon concentration. The major concern that changes in ventilation habits and building conditions lead to substantial errors in exposure (and therefore risk) assessment cannot be confirmed in the data analyzed.

Cancer risks from exposure to radon in homes

Exposure to radon and its decay products in mines is a well recognized risk of lung cancer in miners. A large number of epidemiologic studies from various countries are quite consistent in this respect even it the magnitude of the risk differs according to exposure levels. Indoor radon became a concern in the 1970s and about a dozen studies have been conducted since 1979, mainly of the case-control design. From first being of a simple pilot character, the designs have become increasingly sophisticated, especially with regard to exposure assessment. Crude exposure estimates based on type of house, building material and geological features have been supplemented or replaced by quite extensive measurements. Still, exposure assessment remains a difficult and uncertain issue in these studies, most of which indicate a lung cancer risk from indoor radon. Also a recent large scale study has confirmed a lung cancer risk from indoor radon. More recently there are also some studies, mainly of the correlation type, suggesting other cancers also to be related to indoor radon, especially leukemia, kidney cancer, and malignant melanoma, and some other cancers as well. The data are less consistent and much more uncertain than for indoor radon and lung cancer, however; and there is no clear support from studies of miners in this respect.

Residential radon exposure and lung cancer in Sweden

BACKGROUND

Residential radon is the principal source of exposure to ionizing radiation in most countries. To determine the implications for the risk of lung cancer, we performed a nationwide case-control study in Sweden.

METHODS

The study included 586 women and 774 men 35 to 74 years of age with lung cancer that was diagnosed between 1980 and 1984. For comparison, 1380 female and 1467 male controls were studied. Radon was measured in 8992 dwellings occupied by the study subjects at some time since 1947. Information on smoking habits and other risk factors for lung cancer was obtained from questionnaires.

RESULTS

Radon levels followed a log-normal distribution, with geometric and arithmetic means of 1.6 and 2.9 pCi per liter (60.5 and 106.5 Bq per cubic meter), respectively. The risk of lung cancer increased in relation to both estimated cumulative and time-weighted exposure to radon. In comparison with time-weighted average radon concentrations up to 1.4 pCi per liter (50 Bq per cubic meter), the relative risk was 1.3 (95 percent confidence interval, 1.1 to 1.6) for average radon concentrations of 3.8 to 10.8 pCi per liter (140 to 400 Bq per cubic meter), and it was 1.8 (95 percent confidence interval, 1.1 to 2.9) at concentrations exceeding 10.8 pCi per liter. The estimates of risk were in the same range as those projected from data in miners. The interaction between radon exposure and smoking with regard to lung cancer exceeded additivity and was closer to a multiplicative effect.

CONCLUSIONS

Residential exposure to radon is an important cause of lung cancer in the general population. The risks appear consistent with earlier estimates based on data in miners.

Childhood cancer mortality and radon concentration in drinking water in North Carolina

We explored the association between groundwater radon levels and childhood cancer mortality in North Carolina. Using data from two state-wide surveys of public drinking water supplies, counties were ranked according to average groundwater radon concentration. Age and sex-adjusted 1950-79 cancer death rates among children under age 15 were calculated for counties with high, medium, and low radon levels. Overall cancer mortality was increased in counties with medium and high radon levels. The strongest association was for the leukaemias, but risks were also suggested for other sites. These associations could be due to confounding or other biases, but the findings are consistent with other recent reports.

Radon and health

Radon and its daughter decay products are thought to be the cause of 5% of lung cancer in the UK. This assessment has been made by the National Radiological Protection Board (NRPB) after a national survey of radon levels in homes, when more houses than anticipated were found to have high levels, and after a reappraisal upwards of the effectiveness of radon and its daughter products in causing lung cancer. A review of the scientific evidence reveals no direct evidence to incriminate radon or its decay products at the levels found in our homes in lung cell carcinogenesis. The issue involves different scientific disciplines and is highly complex. Debate between scientists is required and more epidemiological studies of lung cancer and low radon exposure are necessary. Meanwhile the indirect evidence linking low levels of radon exposure to lung cancer is insufficient to warrant the remedial action proposed by the NRPB and accepted by the UK government.