Association between PM2.5 from a coal mine fire and FeNO concentration 7.5 years later

Abstract

Background and aim: There are few long-term studies of respiratory health effects of landscape fires, despite increasing frequency and intensity due to climate change. We investigated the association between exposure to coal mine fire PM_2.5 and fractional exhaled nitric oxide (FeNO) concentration 7.5 years later.

Methods: Adult residents of Morwell, who were exposed to the 2014 Hazelwood mine fire over 6 weeks, and unexposed residents of Sale, participated in the Hazelwood Health Study Respiratory Stream in 2021, including measurements of FeNO concentration, a marker of eosinophilic airway inflammation. Individual exposure to coal mine fire PM_2.5 was modelled and mapped to time-location diaries. The effect of exposure to PM_2.5 on log-transformed FeNO in exhaled breath was investigated using multivariate linear regression models in the entire sample and stratified by potentially vulnerable subgroups.

Results: A total of 326 adults (mean age: 57 years) had FeNO measured. The median FeNO level (interquartile range [IQR]) was 17.5 [15.0] ppb, and individual daily exposure to coal mine fire PM_2.5 was 7.2 [13.8] µg/m³. We did not identify evidence of association between coal mine fire PM_2.5 exposure and FeNO in the general adult sample, nor in various potentially vulnerable subgroups. The point estimates were consistently close to zero in the total sample and subgroups.

Conclusion: Despite previous short-term impacts on FeNO and respiratory health outcomes in the medium term, we found no evidence that PM_2.5 from the Hazelwood coal mine fire was associated with any long-term impact on eosinophilic airway inflammation measured by FeNO levels.

Keywords: Air pollution; Coal industry; Landscape fires; Particulate matter; Respiratory; Smoke.

Fig. 1

Percentage change in FeNO levels per 10 µg/m³ increase in mine fire PM_2.5 after 7.5 years. FeNO = Fractional exhaled nitric oxide (year: 2021) PM_2.5 = particulate matter with a median aerodynamic diameter ≤ 2.5 µm (year: 2014). Main model (entire sample) adjusted for potential confounders selected a priori including town (Morwell vs. Sale), sex, age, BMI, smoking, education, employment, occupational exposure, and any inhaled corticosteroid including combination inhalers. CI = confidence intervals. Preparation for FeNO assessment: excluding individuals who did not follow the preparation for FeNO assessment. Elderly: individuals ≥ 65 years. Obese: individual BMI ≥ 30 kg/m.². Smoking: current and former smokers. Socially disadvantaged: individuals with secondary education up to year 10 or unemployed/unable to work. Respiratory symptoms: individuals with chronic cough, chest tightness or nasal allergy in 2017. Atopic conditions: individuals with chest tightness, nasal allergy or self-reported doctor-diagnosed asthma. Respiratory diseases: individuals with doctor-diagnosed asthma or COPD (spirometry z-score < lower limit of normal)