Human health effects of wildfire smoke report summary
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Purpose
Health Canada has carried out a study of the scientific evidence on the health effects of wildfire smoke. We'll use what we learned from this study to inform our health advice and actions related to wildfire smoke.
Wildfires are a major source of outdoor air pollution around the world. Wildfire smoke can affect air quality close to a fire, but also up to thousands of kilometres away due to the long-range transport of air pollution. We estimate that between 2013 and 2018 in Canada, the air pollutants in wildfire smoke contributed to:
- up to 240 deaths each year due to short-term exposure
- up to 2,500 deaths each year due to long-term exposure
- non-fatal health outcomes related to:
- asthma
- heart conditions
- other respiratory conditions
The estimated annual costs related to wildfire smoke in Canada in the same timeframe were:
- $410 million to $1.8 billion for short-term health effects
- $4.3 billion to $19 billion for long-term health effects
We expect climate change to increase how often wildfires happen and the length of the wildfire season. As such, research into the health effects of wildfire smoke is an area that continues to grow.
Background
Wildfires are defined as the uncontrolled burning of natural vegetation, like trees and plants. Smoke from wildfires contains water vapour, gases and particles. The amount of each can depend on:
- weather conditions, such as temperature and humidity
- what type of fire is causing the smoke, such as flaming versus smoldering
- what kind of vegetation is burning, such as:
- forests versus grasslands
- wet or green vegetation versus dead or dry vegetation
Researchers studying the potential health effects of wildfire smoke often assess exposure to wildfire smoke using fine particles (PM2.5).
Conclusions and considerations
The study concluded that exposure to wildfire smoke increases the risk of adverse health effects, including:
- premature death
- breathing difficulties, including worsening symptoms of asthma and chronic obstructive pulmonary disease
There is some evidence to show that wildfire smoke may also:
- negatively affect heart health
- cause reproductive and developmental effects, such as low birth weight
There is limited evidence that wildfire smoke can result in adverse mental health effects, such as:
- anxiety
- depression
- post-traumatic stress disorder (PTSD)
Some people may be more likely to be affected by wildfires and wildfire smoke, including:
- children
- people aged 65 years and older
- people with pre-existing health conditions
- pregnant people
- people who are at increased risk due to their:
- socio-economic status
- occupation, like wildland firefighters
- location, like those living in areas close to wildfires and wildfire smoke
To fully understand the potential health effects of wildfire smoke, there need to be more studies that consider:
- the combined effects of wildfire smoke and heat to health
- the health effects of different elements of wildfire smoke other than particulate matter (PM)
- the difficulty in differentiating between wildfire-PM2.5 and PM2.5 from all sources
- that research methods based on proximity to wildfires may not represent smoke exposure
- how individual changes in behaviour during a wildfire event could alter the results of a study
- For example, staying indoors or wearing a mask.
Climate change is expected to increase wildfire activity, including increasing the length of wildfire seasons and the frequency of wildfires. As such, it's necessary for there to be more studies to address these gaps in our knowledge.