Why have I still got symptoms after exposure to landscape fire smoke?

Published: June 14, 2023

Landscape fires are an increasing threat to people with asthma. Australia experienced devastating landscape fires between October 2019 and February 2020. These fires caused 26 deaths, destroyed 2,448 homes, and destroyed 5.5 million hectares of land. Individuals with asthma were particularly affected, and many had ongoing symptoms. What can we learn from the Australian experience? This study examined the role of laryngeal hypersensitivity in persistent symptoms and poor asthma control in individuals with asthma and prolonged landscape fire smoke exposure.  

Published in The Journal of Allergy and Clinical Immunology: In Practice, Vertigan and colleagues conducted a cross sectional study of individuals with asthma recruited from severe asthma registries, who were exposed to landscape fire smoke during the 2019-2020 fire period.  Participants provided their primary residential location during the landscape fire period and addresses and dates for up to three additional locations where they resided during the landscape fire period. In addition, participants completed the Laryngeal Hypersensitivity Questionnaire and answered questions about symptoms, asthma control, healthcare utilization, and impact during the landscape fire period, as well as during the two month follow up period. Particulate matter of less than or equal to 2.5um in diameter (PM2.5) concentration levels were measured using fixed site monitors. For each participant, the daily PM2.5 concentration levels at their location over the 152-day study period were averaged to obtain their mean daily PM2.5 (μg/m³) exposure. These data were derived from the Centre for Air pollution, energy and health Research (CAR) data platform (https://cardat.github.io).  

All participants were exposed to high levels of PM2.5 for prolonged periods during the 152 day fire period. Twenty percent of participants had laryngeal hypersensitivity. During the fire period, participants with laryngeal hypersensitivity had more symptoms, asthma exacerbations, and healthcare utilization, and reduced capacity to participate in everyday activities. During the follow-up period, participants with laryngeal hypersensitivity had more symptoms, poorer asthma control, and increased short acting beta agonist use, demonstrating increased symptom burden. These highlight a potential economic impact of laryngeal hypersensitivity for both the individual with asthma and the healthcare system.  

When treating patients with asthma and smoke-induced symptoms, clinicians may consider whether laryngeal hypersensitivity is contributing to the symptoms before escalating asthma treatment, and assess this using the Laryngeal Hypersensitivity Questionnaire. Spontaneous resolution of symptoms may not occur when exposure to landscape fire smoke is removed. Finally, pre-screening patients with asthma for laryngeal hypersensitivity might identify those at risk of poorer asthma control in the event of exposure, and facilitate employment of early risk mitigation strategies to avoid exposure, optimise asthma control, and employ vocal hygiene measures https://toolkit.severeasthma.org.au/resources/infographics/.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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