The impact of the Hazelwood coal mine fire smoke exposure on asthma

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

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 PM2.5 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 PM2.5 was modelled and mapped to time-location diaries. The effect of exposure to PM2.5 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 PM2.5 was 7.2 [13.8] µg/m3. We did not identify evidence of association between coal mine fire PM2.5 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 PM2.5 from the Hazelwood coal mine fire was associated with any long-term impact on eosinophilic airway inflammation measured by FeNO levels.

This time the canary is the coal mine

See related article

Impact of Landscape Fire Smoke Exposure on Patients With Asthma With or Without Laryngeal Hypersensitivity

BACKGROUND

Individuals with asthma experienced severe and prolonged symptoms after the Australian 2019 to 2020 landscape fire. Many of these symptoms, such as throat irritation, occur in the upper airway. This suggests that laryngeal hypersensitivity contributes to persistent symptoms after smoke exposure.

OBJECTIVE

This study examined the relationship between laryngeal hypersensitivity and symptoms, asthma control, and health impacts on individuals exposed to landscape fire smoke.

METHOD

The study was a cross-sectional survey of 240 participants in asthma registries who were exposed to smoke during the 2019 to 2020 Australian fire. The survey, completed between March and May 2020, included questions about symptoms, asthma control, and health care use, as well as the Laryngeal Hypersensitivity Questionnaire. Daily concentration levels of particulate matter less than or equal to 2.5 μm in diameter were measured over the 152-day study period.

RESULTS

The 49 participants with laryngeal hypersensitivity (20%) had significantly more asthma symptoms (96% vs 79%; P = .003), cough (78% vs 22%; P < .001), and throat irritation (71% vs 38%; P < .001) during the fire period compared with those without laryngeal hypersensitivity. Participants with laryngeal hypersensitivity had greater health care use (P ≤ .02), more time off work (P = .004), and a reduced capacity to participate in usual activities (P < .001) during the fire period, as well as poorer asthma control during the follow-up (P = .001).

CONCLUSIONS

Laryngeal hypersensitivity is associated with persistent symptoms, reports of lower asthma control, and increased health care use in adults with asthma who were exposed to landscape fire smoke. Management of laryngeal hypersensitivity before, during, or immediately after landscape fire smoke exposure might reduce the symptom burden and health impact.

Long-term impacts of coal mine fire-emitted PM2.5 on hospitalisation: a longitudinal analysis of the Hazelwood Health Study

BACKGROUND

Little is known about the long-term health impacts of exposures to landscape fire smoke. We aimed to evaluate the association between exposure to coal mine fire-related particulate matter 2.5 μm or less in diameter (PM2.5) and hospitalisation in the 5 years following the 6-week Hazelwood coal mine fire in Australia in 2014.

METHODS

We surveyed 2725 residents (mean age: 58.3 years; 54.3% female) from an exposed and a comparison town. Individual PM2.5 exposures during the event were estimated using modelled PM2.5 concentrations related to the coal mine fire and self-reported location data. The individual exposure and survey data were linked with hospitalisation records between January 2009 and February 2019. Recurrent event survival analysis was used to evaluate relationships between PM2.5 exposure and hospitalisation following mine fire, adjusting for important covariates.

RESULTS

Each 10-µg/m3 increase in mine fire-related PM2.5 was associated with a 9% increased hazard [hazard ratio (HR) = 1.09; 95% confidence interval (CI): 1.01, 1.17] of respiratory hospitalisation over the next 5 years, with stronger associations observed for females (HR = 1.16; 95% CI: 1.06, 1.27) than males (HR = 0.99; 95% CI: 0.89, 1.11). In particular, increased hazards were observed for hospitalisations for asthma (HR = 1.43; 95% CI: 1.19, 1.73) and chronic obstructive pulmonary disease (HR = 1.14; 95% CI: 1.02, 1.28). No such association was found for hospitalisations for cardiovascular diseases, mental illness, injuries, type 2 diabetes, renal diseases or neoplasms.

CONCLUSIONS

A 6-week exposure to coal mine fire-related PM2.5 was associated with increased hazard of respiratory hospitalisations over the following 5 years, particularly for females.

Long-term impact of coal mine fire smoke on lung mechanics in exposed adults

BACKGROUND AND OBJECTIVE

In 2014, a 6-week-long fire at the Hazelwood coal mine exposed residents in the adjacent town of Morwell to high concentrations of fine particulate matter with an aerodynamic diameter < 2.5 μm (PM_2.5 ). The long-term health consequences are being evaluated as part of the Hazelwood Health Study.

METHODS

Approximately 3.5-4 years after the mine fire, adults from Morwell (n = 346) and the comparison town Sale (n = 173) participated in the longitudinal Respiratory Stream of the Study. Individual PM_2.5 exposure was retrospectively modelled. Lung mechanics were assessed using the forced oscillation technique (FOT), utilizing pressure waves to measure respiratory system resistance (Rrs) and reactance (Xrs). Multivariate linear regression was used to evaluate associations between PM_2.5 and transformed Rrs at 5 Hz, area under the reactance curve (AX5) and Xrs at 5 Hz controlling for key confounders.

RESULTS

There were clear dose-response relationships between increasing mine fire PM_2.5 and worsening lung mechanics, including a reduction in post-bronchodilator (BD) Xrs5 and an increase in AX5. A 10 μg/m³ increase in mine fire-related PM_2.5 was associated with a 0.015 (95% CI: 0.004, 0.027) reduction in exponential (Xrs5) post-BD, which was comparable to 4.7 years of ageing. Similarly, the effect of exposure was associated with a 0.072 (0.005, 0.138) increase in natural log (lnAX5) post-BD, equivalent to 3.9 years of ageing.

CONCLUSION

This is the first study using FOT in adults evaluating long-term respiratory outcomes after medium-term ambient PM_2.5 exposure to coal mine fire smoke. These results should inform public health policies and planning for future events.