Wildfires are already burning in parts of Canada, and as they do, many communities are already facing the familiar thick haze as smoke drifts in.
Smoke from wildfires has already led Environment Canada to issue air quality warnings for much of Ontario. In Toronto, smoke led to the city briefly having the worst air quality in the world.
Anyone who has experienced wildfire smoke knows how it can leave you with a scratchy throat, stinging eyes and impact your lungs. However, smoke can also affect your brain. Tiny airborne pollutants found in smoke have been linked to increased risk of stroke, dementia and flare-ups in neurological diseases like multiple sclerosis (MS).
These effects can disproportionately impact older adults, people with disabilities, Indigenous Peoples and those living in low-income communities. This isn’t just about climate. It’s about equity, and health systems need to catch up.
Canada’s 2023 wildfire season was the worst on record, and as climate change worsens wildfires, it may be a sign of what’s to come.
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A direct path to the brain
Alongside harmful gases and heavy metals, wildfire smoke contains fine particulate matter, also known as PM2.5. These tiny particles can travel deep into your lungs, slip into your bloodstream and even reach your brain. Some even bypass the lungs entirely, entering the brain directly through the nose.
After entering the brain, these toxins can cause inflammation and stress, damage nerve cells and even accelerate cognitive decline. Studies have linked exposure to air pollution to an increased risk of stroke and dementia. Even short-term spikes in smoke exposure, like those during wildfires, lead to a surge in emergency visits for strokes, especially among people over 65.
A 2022 experiment had thousands of adults participate in an online attention task under smoky conditions. It found that just a three-hour spike in fine particulate matter, typical of a heavy smoke episode, led to measurably worse attention scores. This fits other evidence that breathing smoke makes people mentally foggy, forgetful or fatigued.
Wildfire smoke, dementia and MS
In 2024, a study found that chronic exposure to wildfire-related air pollution significantly increased the likelihood of someone being diagnosed with dementia. The risk was most pronounced in low-income communities, where people often have less access to clean air, health care and protective measures.
For people already living with neurological conditions like MS or Parkinson’s disease, the stakes are even higher. Exposure to fine particulate pollution has been linked with increased hospital admissions for MS relapses, particularly in young patients. Other research points to worsening symptoms of epilepsy and cognitive decline under extreme heat and polluted air conditions.
Despite these mounting risks, neurological health considerations have been largely absent from wildfire preparedness initiatives and public health responses. That needs to change.
If you want to stay informed about local smoke exposure, tools like AQmap can help you track PM2.5 levels in real time across Canada.
Some more impacted than others
Some face far greater risk from wildfire smoke than others, including older adults, those with pre-existing health conditions, people with lower socio-economic status, Indigenous populations, people residing in remote areas and children. This is a health equity issue as much as a medical one.
Each of these groups faces unique and compounding challenges during smoke events. For example, older adults are more vulnerable to the cardiovascular and neurological effects of smoke. They also face greater barriers to accessing filtered environments.
People with disabilities or chronic illnesses, including those with neurological conditions, often can’t relocate during smoke events and may rely on power-dependent medical devices that can fail during climate emergencies.
Low-income families are more likely to live in housing without proper air filtration or cooling. These same communities often face higher baseline rates of neurological disease.
Indigenous communities, more than 80 per cent of which are located near fire-prone areas, face recurring displacement, interruptions to care and disproportionate exposure to smoke each summer.
Children and adolescents are particularly susceptible to the harmful neurological effects of wildfires. Because their brains are still developing and they breathe more air per body weight than adults, children are especially vulnerable to harmful pollutants.
Studies have linked early-life exposure to fine particulate matter with an increased risk of neuro-developmental disorders, lower cognitive function and structural brain changes.
These populations aren’t just more exposed, they also have fewer resources to respond.
Rethinking Canada’s health systems
Recognizing these inequities, we are developing a climate-health equity framework for Canada, with a specific focus on neurological health. Our interdisciplinary team is asking: how can we build health systems that protect vulnerable brains during climate emergencies?
Health-care workers in Alberta Health Services have designed the Climate-Resilient Acute Care Clinical Operations Framework. This framework supports hospitals in becoming both greener and more resilient, ensuring care can continue during wildfires, floods and extreme heat events.
Importantly, it also centres the needs of equity-deserving populations, integrating climate adaptation into emergency care, supply chains, staffing and patient communication.
What needs to change?
Public awareness must expand beyond respiratory health. Neurological effects of smoke should be included in public health messaging, especially for high-risk groups.
Health systems must be climate-ready, with clean air shelters, evacuation protocols and services tailored to meet the needs of neurological patients.
Communities need support, from funding for air filtration to co-ordinated outreach during smoke events. Indigenous-led fire stewardship and community health initiatives should be part of national planning. Supporting Indigenous-led fire stewardship not only strengthens wildfire response but also respects Indigenous sovereignty and traditional ecological knowledge.
Clinicians must be empowered to address climate-related health risks. Training in environmental health, including its impact on the brain, is increasingly essential.
Wildfire season is back, and with it, an urgent need to protect more than just our lungs. The science is clear: breathing smoky air affects our minds, especially for those already facing health and social vulnerabilities.
Climate change is a brain health issue. Building a healthier, more equitable future requires us to treat it that way, starting now.
