Most respiratory symptoms have resolved 9 years after PM_2.5 exposure from the Hazelwood coal mine fire

In 2014, a coal mine fire in regional Australia exposed the local community to 6 weeks of hazardous fine particulate matter less than 2.5 µm in diameter (PM_2.5). We investigated longitudinal associations between PM_2.5 exposure and respiratory symptoms over 9 years postfire.

In 2016-2017 (wave 1, W1), 4,056 exposed and unexposed adult residents completed surveys, including validated questionnaires for respiratory symptoms. Individual PM_2.5 exposures were estimated using modeled smoke data and time-location diaries. Respiratory symptoms were followed up 4-, 7-, and 9 years postmine fire (W2, W3, and W4) in a weighted random subsample of 519 participants (346 exposed) oversampled for people with asthma. Longitudinal associations between mine fire PM_2.5 and respiratory symptoms were assessed using mixed-effects logistic regression, adjusting for age, sex, socioeconomic factors, smoking, occupational exposures, and self-reported chronic respiratory diseases diagnosed premine fire.

Several patterns were observed. PM_2.5 exposure was associated with elevated wheeze across the survey waves, and the associations tended to be higher among participants with premine fire asthma. Dyspnea (nocturnal and resting) increased at the first survey wave but was not detectable afterwards. Chest tightness and chronic cough had detectable increases at follow-up (W2 for both, W3 for chest tightness), but attenuated in the following surveys. No effects were detectable for chronic phlegm or nasal symptoms.

While there was some variation over time, exposure to mine fire-related PM_2.5 was no longer associated with chest tightness, dyspnea, and chronic cough 9 years postmine fire. The exception was wheeze, where effects of PM_2.5 exposure persisted 9 years later, particularly in people with asthma.