Academic journal article Bulletin of the World Health Organization

Meta-Analysis of Residential Exposure to Radon Gas and Lung Cancer

Academic journal article Bulletin of the World Health Organization

Meta-Analysis of Residential Exposure to Radon Gas and Lung Cancer

Article excerpt

Objectives To investigate the relation between residential exposure to radon and lung cancer.

Methods A literature search was performed using Medline and other sources. The quality of studies was assessed. Adjusted odds ratios with 95% confidence intervals (CI) for the risk of lung cancer among categories of levels of exposure to radon were extracted. For each study, a weighted log-linear regression analysis of the adjusted odds ratios was performed according to radon concentration. The random effect model was used to combine values from single studies. Separate meta-analyses were performed on results from studies grouped with similar characteristics or with quality scores above or equal to the median.

Findings Seventeen case-control studies were included in the meta-analysis. Quality scoring for individual studies ranged from 0.45 to 0.77 (median, 0.64). Meta-analysis based on exposure at 150 Bq/[m.sup.3] gave a pooled odds ratio estimate of 1.24 (95% CI, 1.11-1.38), which indicated a potential effect of residential exposure to radon on the risk of lung cancer. Pooled estimates of fitted odds ratios at several levels of radon exposure were all significantly different from unity--ranging from 1.07 at 50 Bq/[m.sup.3] to 1.43 at 250 Bq/[m.sup.3]. No remarkable differences from the baseline analysis were found for odds ratios from sensitivity analyses of studies in which >75% of eligible cases were recruited (1.12, 1.00-1.25) and studies that included only women (1.29, 1.04-1.60).

Conclusion Although no definitive conclusions may be drawn, our results suggest a dose-response relation between residential exposure to radon and the risk of lung cancer. They support the need to develop strategies to reduce human exposure to radon.

Keywords Radon/adverse effects; Lung neoplasms/chemically induced; Environmental exposure; Residence characteristics; Households; Case-control studies; Cohort studies; Meta-analysis (source: MeSH, NLM).

Mots cles Radon/effets indesirables; Tumeur poumon/induit chimiquement; Exposition environnement; Caracteristiques habitat; Menages; Etude cas-temoins; Etude cohorte; Meta-analyse (source: MeSH, INSERM).

Palabras clave Radon/efectos adversos; Neoplasmas pulmonares/inducido quimicamente; Exposici6n a riesgos ambientales; Distribucion espacial; Hogares; Estudios de casos y controles; Estudios de cohortes; Meta-analisis (fuente: DeCS, BIREME).

Voir page 736 le resume en francais. En la pagina 737 fugura un resumen en espanol.

Introduction

The role of radon as a risk factor for lung cancer in occupational settings, such as underground mining, has been documented in several studies (1-4), whereas the risk associated with residential exposure to radon remains controversial. Radon-222--a ubiquitous radioactive gas--is present in the earth's crust and emerges from soils and rocks. It represents, with its progeny, one of the main sources of exposure to radioactivity in humans, as it emits alpha particles that may damage lung tissues after inhalation. Outdoor concentrations of radon generally are low; a cause for concern is the concentrations inside buildings, where radon can penetrate from subsoil, may be included in building materials, and may be found in water. Indoor concentrations of radon may vary depending on the concentration of radon in the soil; the permeability of the ground; and the construction, building materials, and ventilation of the house.

Attempts to extrapolate data from occupational studies to estimate the risk associated with residential exposure to radon have been criticized because of possible differences in levels of exposure between underground miners and people in the indoor environment and because of several other factors--e.g. possible effects of other concurrent lung carcinogens in miners, differences in particle size distribution, and differences in breathing rates (5-7). Findings of large-scale observational studies (particularly case-control studies) of the effects of residential exposure to radon in different countries have produced conflicting results--some confirm the data found in miners (8-13), while others could not find any association between exposure to radon and lung cancer (14-16). …

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