Indoor Radon Exposure and COPD, Synergic Association? A Multicentric, Hospital-Based Case-Control Study in a Radon-Prone Area.

Background: COPD is a multifactorial disease which causes considerable mortality and morbidity worldwide. Previous studies assessing the possible relationship between indoor radon exposure and COPD have shown inconclusive results.

Methods: A multicentric, hospital-based, case-control study was conducted in a Spanish radon-prone area. COPD cases were confirmed by spirometry and controls were selected due to trivial surgery or procedures not related to tobacco consumption. All participants had to have lived for at least 15 years in the same dwelling. Radon measurements were conducted individually in dwellings using alpha-track detectors. Results were obtained using multivariate logistic regression.

Results: 189 cases and 747 controls took part. There was no significant association between residential radon concentrations and COPD onset with a OR of 1.12 (95%CI 0.41-3.06) for individuals exposed to more than 200Bq/m compared to those exposed to less than 50Bq/m. Heavy smokers seem to increase their COPD risk if exposed to higher radon concentrations vs those exposed to lower concentrations. There was a statistically significant synergy index between radon exposure and tobacco consumption, S-index 11.60 (95%CI 3.71-36.26). Indoor radon concentration was higher in never/light smokers with COPD compared to controls.

Conclusions: No association between indoor radon and COPD has been observed. However, there might be some effect modification on the COPD risk in heavy smokers when high radon exposure is present. This is supported by the additive synergy observed. Also, a possible association between indoor radon and COPD onset in never and light smokers needs to be further studied.