Bushfires appear to affect lung function of children with asthma

31 January 2023

Published by: https://www.healio.com

AUSTRALIA – Children with asthma exposed to bushfire smoke demonstrated a clinically important 5% mean decrease in forced vital capacity percent predicted, according to a study published in Pediatric Allergy and Immunology.

Carla Rebeca Da Silva Sena, PhD, research associate at The University of Newcastle and pediatric researcher at Hunter Medical Research Institute, and colleagues collected data from 129 children with asthma aged 4 to 16 years who had lung function tests during 212 visits to the outpatient childhood asthma clinic at John Hunter Children’s Hospital in New South Wales, Australia, between January 2019 and April 2020, when 5.5 million hectares of land were affected by wildfires in the state.

After collecting data on 36 days with bushfires and 176 days without bushfires, the researchers did not find any differences in Asthma Control Test scores between children tested on both occasions.

Mean levels of particulate matter at the 2.5 µm scale (PM2.5) reached 35.7 µg/m3(standard deviation [SD], 16.8) on days with bushfires compared with 8.3 µg/m3(SD, 3.2; P < .001) on days that did not have bushfires.

A mixed model revealed a mean decrease of 5% in forced vital capacity percent (FVC%) predicted among children with asthma who visited the clinic on days with bushfires, but this decrease was ameliorated after 10 minutes with bronchodilator administration (–3; 95% CI, –6.83 to 0.82).

Also, the researchers did not find any significant decrease in FEV1 or in FEV1/FVC ratio percent predicted.

When the researchers examined data from 59 children who had visits on days with and without a bushfire, they found that the bushfire day had comparable effects, although they did not reach significant levels (–4.36; 95% CI, –9.24 to 0.55).

The researchers also found a significant decrease in FVC% predicted (–0.19; 95% CI, –0.301 to –0.048) and FEV1% predicted (–0.14; 95% CI, –0.265 to –0.005) for each microgram per cubic meter increase in mean PM2.5concentrations on the day of the visit to the clinic when it was measured as a continuous independent variable.

Modeling indicated that exposure to 71.6 µg/m3 of PM2.5 on bushfire days, which the researchers called the highest mean concentration recorded, could lead to a 14% decrease in FVC% predicted and a 10% decrease in FEV1% predicted compared with the mean levels of 8.3 µg/m3 calculated for days without a bushfire.

Based on these findings, the researchers concluded that exposure to bushfires around the time of lung function testing was associated with a clinically important mean decrease of 5% in FVC% precited among children with asthma.


Erika M. Moseson, MD

This study from The University of Newcastle provides an important window into the impact of wildland fire (or “bushfire” in Australia) on children with asthma. Wildland fire generates a great deal of PM2.5, which is a driver of multiple adverse health impacts among people of all life stages, but children are especially vulnerable.

These tiny particles are a fraction of the size of a human hair. When we inhale, we bring them into the bloodstream, causing disease in multiple organs. We have ample evidence that there are increases in asthma attacks among children on days of poor air quality and elevated PM2.5 from other studies, including work that has previously been highlighted here.

This study indicates that even among children not in exacerbation arriving for regularly scheduled testing on days of high PM2.5, FVC has decreased. I agree with the authors that it is likely that this decrease in FVC may represent an increase in air trapping driven by inhaling the PM2.5.

I live in Oregon, and we have the dubious distinction of having had the worst air in the world because of wildfires a couple of times in the last several years. I am raising three children in air that has been rated as “Hazardous” or “Beyond Index” on the Air Quality Index.

As a lung doctor, what do I do when I know the potential lifelong complications of breathing PM2.5? I empathize with the parents of those children with asthma in this study. It must be a great source of worry to them to know that the air their children are breathing may be affecting their lung function. It is especially significant that this was picked up in such a relatively small sample of children.

So, what can doctors and health professionals do about this? First, we need to educate ourselves. I didn’t learn anything about particulate matter, ozone or air pollution in medical school or during my medical training. Part of the mission of Air Health Our Health is to ensure that we all know how air pollution can affect our health.

Fortunately, if you can talk about cigarettes with your patients, you can talk about PM2.5. The punchline is “Don’t light things on fire and breathe them into your lungs.” This applies whether we are talking about cigarettes, diesel, wildfires and more.

I host the Air Health Our Health podcast and interview a range of experts to educate clinicians, parents and the community at large on the health impacts of particulate matter, climate change, wildfires and more. Pediatricians and parents may be interested in the episode with Franziska Rosser, MD, MPH, a pediatric pulmonologist who researches the Air Quality Index, kids and how parents and pediatricians should use it.

Because this is not an individual-level problem, we in health care also need to educate our communities. We need to advocate for ways to decrease the climate change that is driving these wildland fires as well as also for resiliency measures. For example, we need to ensure that there is access to clean indoor air in the time of wildfires, knowing how to talk about HEPA filters with our patients and how to avoid or mitigate other sources of indoor air pollution, such as gas stoves.

I provided a brief introduction to Healio on the interaction of climate change and particulate matter on health in this Healio video from CHEST 2022. It is important for those in health care to learn how climate change and air pollution affect our health so we can work for cleaner air for all our patients.

Erika M. Moseson, MD
Pulmonary Section Chair, Legacy Emanuel Medical Center, Portland, Oregon
Host, Air Health Our Health Podcast
Past President, Oregon Thoracic Society
Member, Environmental Health Policy Committee, American Thoracic Society
American Lung Association Health Professional for Clean Air and Climate Action
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