Respiratory symptoms after coalmine fire and pandemic: A longitudinal analysis of the Hazelwood Health Study adult cohort

Abstract

The aim of this study was to determine whether the effects of extreme but discrete PM2.5 exposure from a coal mine fire on respiratory symptoms abated, persisted, or worsened over time, and whether they were exacerbated by COVID-19. We analysed longitudinal survey data from a cohort residing near a 2014 coalmine fire in regional Australia. A 2016/2017 survey included 4,056 participants, of whom 612 were followed-up in 2022. Items included respiratory symptoms, history of COVID-19, and time-location diaries from the mine fire period, which were combined with geospatial and temporal models of fire-related PM2.5. Longitudinal effects of fire-related PM2.5 were examined using a mixed-effects logistic regression model. Exacerbation due to COVID-19 was examined using a logistic regression model. PM2.5 exposure was associated with chronic cough and possibly current wheeze, chest tightness, and current nasal symptoms 2-3 years post-fire, and chronic cough and current wheeze 8.5-9 years post-fire. Further, the association between PM2.5 and chronic cough and possibly current wheeze appeared to increase between the survey periods. While there were no detectable interactions between PM2.5 and COVID-19, PM2.5 exposure was associated with additional respiratory symptoms among participants who reported a history of COVID-19. In summary, medium-duration exposure to extreme levels of fire-related PM2.5 may have increased the long-term risk of chronic cough and current wheeze. While the COVID-19 pandemic started several years after the mine fire, contracting this illness may have exacerbated the effect of fire-related PM2.5 through development of additional respiratory symptoms.

Fig 1. Maps of Victoria illustrating location of the coalmine and distributions of fire related-PM_2.5 (February to March 2014) in the surrounding areas, highlighting exposure site Morwell and control site Sale; boundary data from the Australian Bureau of Statistics (source:https://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/1270.0.55.006July2011; copyright information: https://www.abs.gov.au/website-privacy-copyright-and-disclaimer#copyright-and-creative-commons) [45], coalmine boundary data from the Department of Primary Industries [46] and Department of Energy, Environment and Climate Action’s DataShare platform (source: https://datashare.maps.vic.gov.au/search?q=victorian%20coal%20fields; copyright information: https://www.deeca.vic.gov.au/copyright) [47], and modelled PM_2.5 data from Luhar et al. 2020 [4].

Fig 2. Effects of 10 µg/m³ increase in daily mean coalmine fire-related PM_2.5 on risk of respiratory symptoms at the initial 2016/17 survey (2–3 years post-fire), change between the two survey rounds (interaction term between fire-related PM_2.5 and survey round), and the long-term effect at the 2022 follow-up (8.5–9 years post-fire, estimated using linear combination of PM_2.5 and interaction term); faded points and intervals indicate non-significant effects.

Fig 3. Moderating effect of COVID-19 on relationship between daily mean coalmine fire-related PM_2.5 (10 µg/m³) and risk of respiratory symptoms at the 2022 follow-up survey (8.5–9 years post-fire, estimated using linear combination of PM_2.5 and interaction term); faded points and intervals indicate non-significant effects.