Modeling of respiratory system dysfunction among nuclear workers: a preliminary study

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/m³ compared to those exposed to less than 50Bq/m³. 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.

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/m3 compared to those exposed to less than 50Bq/m3. 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.

Associations between ambient particle radioactivity and lung function

Previous studies have suggested increased risk of respiratory diseases and mortality following short-term exposures to ionizing radiation. However, the short-term respiratory effects of low-level environmental radiation associated with air pollution particles have not been considered. Although ambient particulate matter (PM) has been reproducibly linked to decreased lung function and to increased respiratory related morbidity, the properties of PM promoting its toxicity are uncertain. As such, we evaluated whether lung function was associated with exposures to radioactive components of ambient PM, referred to as particle radioactivity (PR). For this, we performed a repeated-measures analysis of 839 men to examine associations between PR exposure and lung function using mixed-effects regression models, adjusting for potential confounders. We examined whether PR-lung function associations changed after adjusting for PM2.5 (particulate matter≤2.5 μm) or black carbon, and vice versa. PR was measured by the USEPA's radiation monitoring network. We found that higher PR exposure was associated with a lower forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). An IQR increase in 28-day PR exposure was associated with a 2.4% lower FVC [95% confidence interval (CI): 1.4, 3.4% p < 0.001] and a 2.4% lower FEV1 (95% CI: 1.3, 3.5%, p < 0.001). The PR-lung function associations were partially attenuated with adjustment for PM2.5 and black carbon. This is the first study to demonstrate associations between PR and lung function, which were independent of and similar in magnitude to those of PM2.5 and black carbon. If confirmed, future research should account for PR exposure in estimating respiratory health effects of ambient particles. Because of widespread exposure to low levels of ionizing radiation, our findings may have important implications for research, and environmental health policies worldwide.

Radon and COPD mortality in the American Cancer Society Cohort

Although radon gas is a known cause of lung cancer, the association between residential radon and mortality from non-malignant respiratory disease has not been well characterised. The Cancer Prevention Study-II is a large prospective cohort study of nearly 1.2 million Americans recruited in 1982. Mean county-level residential radon concentrations were linked to study participants' residential address based on their ZIP code at enrolment (mean ± SD 53.5 ± 38.0 Bq · m(-3)). Cox proportional hazards regression models were used to estimate adjusted hazard ratios (HR) and 95% confidence intervals (CI) for non-malignant respiratory disease mortality associated with radon concentrations. After necessary exclusions, a total of 811,961 participants in 2,754 counties were included in the analysis. Throughout 2006, there were a total of 28,300 non-malignant respiratory disease deaths. Radon was significantly associated with chronic obstructive pulmonary disease (COPD) mortality (HR per 100 Bq · m(-3) 1.13, 95% CI 1.05-1.21). There was a significant positive linear trend in COPD mortality with increasing categories of radon concentrations (p<0.05). Findings suggest residential radon may increase COPD mortality. Further research is needed to confirm this finding and to better understand possible complex inter-relationships between radon, COPD and lung cancer.

Manganese superoxide dismutase is not protective in bovine pulmonary artery endothelial cells at systemic oxygen levels

Bovine pulmonary artery endothelial cells (BPAEC) are extremely sensitive to oxygen, mediated by superoxide production. Ionizing radiation is known to generate superoxide in oxygenated aqueous media; however, at systemic oxygen levels (3%), no oxygen enhancement is observed after irradiation. A number of markers (cell growth, alamarBlue, mitochondrial membrane polarization) for metabolic activity indicate that BPAEC maintained under 20% oxygen grow and metabolize more slowly than cells maintained under 3% oxygen. BPAEC cultured in 20% oxygen grow better when they are transiently transfected with either manganese superoxide dismutase (MnSOD) or copper zinc superoxide dismutase (CuZnSOD) and exhibit improved survival after irradiation (0.5-10 Gy). Furthermore, X irradiation of BPAEC grown in 20% oxygen results in very diffuse colony formation, which is completely ameliorated by either growth in 3% oxygen or overexpression of MnSOD. However, MnSOD overexpression in BPAEC grown in 3% oxygen provides no further radioprotection, as judged by clonogenic survival curves. Radiation does not increase apoptosis in BPAEC but inhibits cell growth and up-regulates p53 and p21 at either 3% or 20% oxygen.