Long‐term effects of extreme smoke exposure on COVID‐19: A cohort study

• Published in: Respirology (Carlton, Vic.) Vic.), 2024-01, Vol.29 (1), p.56-62
• Main Authors: Lane, Tyler J., Carroll, Matthew, Borg, Brigitte M., McCaffrey, Tracy A., Smith, Catherine L., Gao, Caroline X., Brown, David, Poland, David, Allgood, Shantelle, Ikin, Jillian, Abramson, Michael J.
• Format: Article
• Language: English
• Subjects: Adult; Air Pollutants - adverse effects; air pollution; Air Pollution - adverse effects; Australia - epidemiology; Cohort Studies; COVID-19; COVID-19 - epidemiology; environmental and occupational health; Environmental Exposure - adverse effects; epidemiology; Humans; Particulate Matter - adverse effects; Particulate Matter - analysis; Regression analysis; Respiratory diseases; Risk factors; Smoke; Smoke - adverse effects; smoke exposure cohort study; Vaccination
• ISSN: 1323-7799; 1440-1843; 1440-1843
• DOI: 10.1111/resp.14591

Background In 2014, the Hazelwood coalmine fire shrouded the regional Australian town of Morwell in smoke and ash for 6 weeks. One of the fire's by‐products, PM2.5, is associated with an increased risk of COVID‐19 and severe disease. However, it is unclear whether the effect persisted for years after exposure. In this study, we surveyed a cohort established prior to the pandemic to determine whether PM2.5 from the coalmine fire increased long‐term vulnerability to COVID‐19 and severe disease. Methods From August to December 2022, 612 members of the Hazelwood Health Study's adult cohort, established in 2016/17, participated in a follow‐up survey that included standardized items to capture COVID‐19 cases, as well as questions about hospitalization and vaccinations. Associations were evaluated in crude and adjusted logistic regression models. Results A total of 268 (44%) participants self‐reported or met symptom criteria for having had COVID‐19 at least once. All models found a positive association, with odds of COVID‐19 increasing by between 4% and 30% for a 10 μg/m3 increase in coalmine fire‐related PM2.5 exposure. However, the association was significant in only 2 of the 18 models. There were insufficient hospitalizations to examine severity (n = 7; 1%). Conclusion The findings are inconclusive on the effect of coalmine fire‐related PM2.5 exposure on long‐term vulnerability to COVID‐19. Given the positive association that was robust to modelling variations as well as evidence for a causal mechanism, it would be prudent to treat PM2.5 from fire events as a long‐term risk factor until more evidence accumulates. Surveying a cohort established before the pandemic, we investigated long‐term COVID‐19 vulnerability due to coalmine fire smoke exposure. There was a positive but generally non‐significant association between PM2.5 and COVID‐19. It would therefore be prudent to treat extreme but discrete coalmine fire smoke as a long‐term COVID‐19 risk factor. See related editorial