Cytotoxic and Genotoxic Responses of Human Lung Adenocarcinoma Cells to Sequential Exposure to Household Dust Extract and Indoor Radon

Humans spend a substantial proportion of their time indoors, where exposure to environmental pollutants such as radon gas and particulate contaminants in household dust is common. While radon is a well-established risk factor for lung cancer, household dust may serve as a reservoir for a complex mixture of indoor and outdoor pollutants. However, the biological effects of such exposures, particularly under sequential conditions, remain incompletely understood. This study aimed to investigate the cytotoxic and genotoxic effects of sequential exposure to household dust extract followed by indoor radon using human lung adenocarcinoma (A549) cells as an in vitro model. Household dust samples from upper northern Thailand were extracted and applied to cells, followed by controlled radon exposure. Cellular responses were evaluated using cell viability assays, cytokinesis-block micronucleus (MN) formation assays, and Western blot analysis of oxidative stress-related (Nrf2/HO-1), DNA damage-related (γ-H2AX), autophagy-related (LC3), and inflammatory-related (IL-6) protein expression. Exposure to household dust extract was associated with reduced cell viability and increased MN formation, while radon exposure alone produced relatively modest effects under the present conditions. Sequential exposure to household dust extract followed by indoor radon was associated with increased oxidative stress-related responses and elevated DNA damage than either treatment alone under the present experimental conditions. A trend toward autophagy-related responses was also observed, and the overall findings may indicate possible combined biological responses under sequential exposure conditions. These findings suggest that sequential exposure may be associated with changes in oxidative stress-related pathways, DNA damage responses, and autophagy-related processes in this in vitro model. However, the results should be interpreted with caution as they are derived from a single cancer cell line and there are limitations to the in vitro exposure model. Further studies using additional cell models and in vivo systems are warranted to further clarify the potential biological and human health relevance of these findings.