Chronic exposure to volcanogenic carbon dioxide and radon: how does it affect lung function and DNA in oral epithelial cells of the inhabitants in hydrothermal areas

Hydrothermal areas are potentially hazardous to humans, as volcanic gases such as carbon dioxide (CO₂) and radon (²²²Rn) are continuously released from soil diffuse degassing. Even though many studies have established an association between exposure to anthropogenic air pollution and changes in lung function and, that radon exposure is estimated to be the second leading cause of lung cancer, the health risks of exposure to these elements in hydrothermal areas remain poorly known.

We investigated the association of chronic exposure to volcanogenic soil diffuse degassing with restrictive and chronic obstructive (COPD) respiratory defects and with DNA damage. A cross-sectional study was designed to evaluate the human lung function and the DNA damage in the buccal epithelial cells of individuals chronically exposed to carbon dioxide and indoor radon in a volcanic area (Furnas volcano, Azores, Portugal) with a hydrothermal system. A total of 150 individuals inhabiting the hydrothermal area (study group) and a reference group of 383 individuals inhabiting a non-hydrothermal area were considered to study the lung function; to study the DNA damage, buccal epithelial cells were collected from a sub-selection of 33 individuals inhabiting the volcanic area and from 49 individuals inhabiting the non-hydrothermal area. Lung function [FEV₁ (forced expiratory volume in 1 sec), FVC (forced vital capacity) and Tiffeneau-Pinelli index (FEV₁/FVC ratio)] were measured by spirometry test. Indoor radon was measured with Ramon 2.2 detectors. DNA damage was measured by micronucleus cytome assay. Data were analyzed with logistic regression models, adjusting for confounding factors (age, gender, body mass index, smoking status, and asthma). 

The prevalence of restrictions in the study group was significantly higher than in the reference group (10% vs. 2.87%, respectively; p<0.001). Similarly, the prevalence of COPD in the study group was significantly higher than in the reference group (33% vs. 12%, respectively; p<0.001). Chronic exposure to volcanogenic soil diffuse degassing was significantly associated with a higher prevalence of respiratory restrictions and exacerbation in COPD severity. The risk of having a restrictive respiratory defect was significantly increased in the study group (3.55 times higher) when compared to the reference one. Similarly, the risk of COPD exacerbation was significantly increased in the study group (3.96 times higher). Indoor radon concentration correlated positively with the frequency of micronucleated cells (rs=0.325, p=0.003) and revealed to be a risk factor for the occurrence of micronucleated cells in the inhabitants of the hydrothermal area (RR= 1.71; 95% CI, 1.2–2.4; p=0.003).

These findings reinforce the need for further studies with human populations living in these areas and, may assist health officials in advising and keeping up with these populations to prevent and minimize the risk of respiratory diseases and DNA damage caused by genotoxic elements.

 

Keywords: Volcanic gases, volcanism, genotoxicity; micronuclei; biomonitoring.