Fire smoke and lungs: what you're really breathing

In brief

• Wildfire smoke isn't just soot — it contains PM2.5, PM10, carbon monoxide, VOCs, PAHs, and heavy metals, each with distinct health effects.
• PM2.5 particles are fine enough to pass from the lungs into the bloodstream, increasing the risk of heart attack, stroke, and chronic lung disease.
• In July 2026, Airparif measured approximately 400 µg/m³ of PM2.5 near Fontainebleau — more than 26 times the WHO 24-hour limit of 15 µg/m³.

Most people view wildfire smoke as a temporary nuisance — something that stings the eyes and smells like a campfire. This is wrong. The health risks of wildfire smoke are real, measurable, and sometimes permanent. The 2026 wildfire season in France brutally demonstrated this.

This article explains exactly what smoke contains, what it does to your body, and when you should stop treating it as background noise.

What is wildfire smoke made of?

Wildfire smoke is not a single substance. It is a dynamic chemical mixture that varies depending on what is burning — pine forest, oak grove, homes, vehicles — and the fire's temperature. The EPA describes it as a complex mixture of gases and particles comprising hundreds of distinct compounds.

Here's what matters for your health.

PM2.5 and PM10 — the particulate fraction that reaches your blood

Particulates are the primary health threat from wildfire smoke.

• PM10 (particles ≤ 10 micrometers): mainly retained in the nose, throat, and upper airways. Irritating, but largely filtered by natural defenses.
• PM2.5 (particles ≤ 2.5 micrometers): these bypass all upper airway defenses and reach the alveoli — the tiny sacs where gas exchange occurs. From there, the finest fraction can pass directly into the bloodstream.

Wildfire PM2.5 is dominated by organic carbon and soot carbon — carbon-rich particles resulting from incomplete combustion. They carry other toxic compounds adsorbed to their surface, acting as a delivery vehicle for the rest of the smoke.

The 2021 WHO guidelines set the safe 24-hour PM2.5 limit at 15 µg/m³. During the Fontainebleau fires in July 2026, Airparif measured hourly concentrations of approximately 400 µg/m³ at the Recloses station. This is not a rounding error. It is a figure that puts vulnerable people in immediate danger.

Carbon Monoxide (CO) and Nitrogen Oxides

Carbon monoxide forms whenever organic matter burns with insufficient oxygen. It binds to red blood cell hemoglobin with an affinity 200 to 250 times greater than oxygen, thus depriving tissues of O₂. At low concentrations: headaches, fatigue, decreased cognitive function. At high concentrations near an active fire front: loss of consciousness.

Nitrogen oxides (NOₓ) — especially NO₂ — form when combustion temperatures are high. They irritate the respiratory tract, reduce lung function, and, with prolonged exposure, increase susceptibility to respiratory infections.

Volatile Organic Compounds (VOCs) and Polycyclic Aromatic Hydrocarbons (PAHs)

Wildfire smoke contains hundreds of VOCs, including benzene, formaldehyde, acrolein, and acetaldehyde. These are not trace amounts: benzene, a known human carcinogen, has been measured at high concentrations in smoke plumes miles from the source.

PAHs form when organic matter burns at high temperatures. Several of them — including benzo[a]pyrene — are classified as probable or known carcinogens by the International Agency for Research on Cancer (IARC). They attach to PM2.5 particles, meaning they travel deep into the lungs with them.

Heavy metals from burned structures and vehicles

When a fire crosses the wildland-urban interface — homes, cars, industrial buildings — the composition of the smoke changes radically. Studies have detected high concentrations of lead, zinc, copper, manganese, arsenic, and chromium in smoke from structural fires.

Even in purely forest areas, soil disturbance and the combustion of bark and wood release particles of aluminum, iron, and silicon. These metals contribute to oxidative stress in lung tissue and, with repeated exposures, to systemic inflammation.

How wildfire smoke damages your body

Understanding the composition is one thing. Understanding what it actually does inside is another.

The respiratory system — from irritation to chronic lesions

The initial effects are immediate and obvious: cough, throat irritation, shortness of breath, wheezing. These are your airways reacting to acute chemical aggression. In most healthy adults, these symptoms disappear once exposure ends.

But the damage doesn't stop at irritation. Wildfire PM2.5 triggers inflammatory responses in the alveoli. With repeated or prolonged exposure, this inflammation can:

• Worsen existing asthma and trigger attacks
• Accelerate the progression of COPD
• Increase susceptibility to respiratory infections (including pneumonia)
• Cause bronchitis — acute, or chronic with prolonged exposure

A 2021 study published in Nature Communications showed that wildfire PM2.5 might have greater respiratory effects than equivalent concentrations of PM2.5 from other sources, likely due to their unique organic composition and higher oxidative potential.

Work by the Harvard T.H. Chan School of Public Health (2023) showed that the cardiorespiratory effects of smoke particles can persist for several months after a fire ends — even in people who seemed to recover quickly.

Cardiovascular effects (PM2.5 enters the blood)

This is the part most people don't expect. Smoke inhalation symptoms like coughing resemble a lung problem. But PM2.5 is also a cardiovascular problem.

The finest particles — ultrafines under 0.1 µm — cross the alveolar membrane and enter the general circulation. Once in the blood, they trigger:

• Oxidative stress and systemic inflammation
• Endothelial dysfunction (damage to blood vessel walls)
• Hypercoagulability — the blood becomes more prone to clotting

Result: an increased risk of heart attack, stroke, arrhythmia, and heart failure. The American Heart Association's journal Circulation (2022) confirmed that wildfire PM2.5 is linked to cardiovascular morbidity and mortality, with the elderly and those with heart conditions being most at risk.

The American College of Cardiology reported in June 2025 that repeated wildfire exposures can progressively increase the risk of heart failure — each fire season adding to the cumulative cardiovascular load.

Eyes, skin, and neurological effects

Smoke doesn't only enter through the lungs.

• Eyes: conjunctivitis, burning, and tearing are common. Prolonged exposure can worsen dry eye.
• Skin: fine particles and VOCs can cross the skin barrier, contributing to oxidative damage and aggravating eczema or psoriasis.
• Neurological effects: emerging research links smoke exposure to cognitive impairment, anxiety, and depression. Ultrafine particles could reach the brain via the olfactory nerve or general circulation. A study published in PNAS in 2024 established associations between wildfire PM2.5 and an increase in neurological hospitalizations.

Long-term exposure versus acute episodes

A bad day of smoke is not equivalent to experiencing an entire fire season.

Acute episodes (a few hours to a few days): reversible irritation, asthma attacks, cardiovascular stress events. Dangerous for vulnerable groups; manageable for a healthy adult with the right precautions.

Repeated or prolonged exposure (weeks, months, or several seasons): cumulative lung damage, accelerated COPD progression, increased lifetime cancer risk from PAHs and benzene, and increasing cardiovascular burden. The Yale School of Public Health (2024) established that long-term exposure to wildfire smoke is associated with a higher risk of death from cardiorespiratory causes.

The distinction matters for knowing how to react — but both call for action.

Who is most at risk?

Wildfire smoke harms everyone. But not everyone in the same way.

Children and the elderly

Children breathe more air per kilogram of body weight than adults, their lungs are still developing, and they spend more time outdoors. Exposure during lung development can have lasting consequences on respiratory capacity.

Elderly individuals (65 and older) more often have underlying cardiovascular or respiratory conditions, and their bodies are less able to compensate for the oxidative stress triggered by PM2.5.

People with asthma, COPD, or heart conditions

If you already have asthma, wildfire smoke is a reliable trigger. PM2.5 and VOCs inflame already sensitized airways, and even moderate levels can cause severe exacerbations.

COPD patients have reduced lung reserve. What a healthy person experiences as discomfort can push a COPD patient into respiratory failure.

Patients with cardiovascular disease accumulate risks: systemic inflammation due to PM2.5 acts on already weakened vessels and heart muscle.

Pregnant women

Exposure to wildfire smoke during pregnancy is associated with an increased risk of premature birth, low birth weight, and impaired fetal lung development. The placenta does not fully protect the fetus from the systemic inflammation triggered by PM2.5. French health authorities (ARS) explicitly included pregnant women in their recommendations for at-risk groups during the 2026 season.

Outdoor workers and athletes

Outdoor workers — construction, agriculture, green spaces — have no choice but to be outside. Prolonged exposure during a smoke episode can be equivalent to dozens of cigarettes in terms of particles inhaled during a single workday.

Athletes form a counter-intuitive at-risk group. During intense exercise, respiratory rate increases 10 to 20 times compared to rest. A runner training during a smoke episode inhales far more PM2.5 than a person sitting down. The risk of wildfire smoke on athletes' health is often underestimated, precisely because they feel fit.

Real data: smoke levels in France in 2026

The summer of 2026 turned France into a full-scale experiment on air quality in a wildfire context. Figures from monitoring networks were alarming.

Fontainebleau: PM2.5 peak at ~400 µg/m³ (WHO limit: 15 µg/m³)

On the night of July 13-14, 2026, as fires ravaged over 1,900 hectares of the Fontainebleau forest south of Paris, Airparif's Recloses (Rural South-East) station recorded hourly PM2.5 and PM10 concentrations of approximately 400 µg/m³.

To put this in context:

• WHO PM2.5 24-hour recommendation: 15 µg/m³
• French information/recommendation threshold (PM10): 50 µg/m³/day
• Fontainebleau peak: ~400 µg/m³ — more than 26 times the WHO limit, 8 times the French alert threshold

Airparif confirmed the exceedance of the daily information threshold and published a special bulletin. The smoke plume, pushed by light northeasterly winds, affected a large part of Île-de-France.

Gironde and Landes: PM10 alert thresholds exceeded

At the end of July 2026, fires in Gironde and Landes caused a second major smoke episode in the southwest. Bordeaux recorded PM2.5 peaks above 300 µg/m³ on July 26. The Atmo Nouvelle-Aquitaine network confirmed exceedances of the PM10 alert threshold (80 µg/m³/day) at several stations.

The ARS Nouvelle-Aquitaine issued health recommendations urging residents — particularly at-risk groups — to limit outdoor activities, keep windows closed, and avoid physical exertion.

What these numbers mean for your health

These are not abstract statistics. At 400 µg/m³ of PM2.5:

• Healthy adults will experience eye and throat irritation, coughing, and decreased lung function within a few hours.
• Asthmatics and COPD patients face a high risk of acute exacerbation requiring medical attention.
• Children and the elderly should be considered in immediate danger and remain indoors.
• Everyone experiences cardiovascular stress related to PM2.5 entering the bloodstream.

The 2026 situation in France is not an anomaly. Climate projections show longer and more intense fire seasons in Southern and Central Europe. This is the new normal.

At what PM2.5 level should you act?

Knowing the numbers is only useful if you know what to do with them.

WHO thresholds and French regulatory thresholds

Current French regulatory limits are significantly more permissive than WHO recommendations. The new European air quality directive adopted in 2024 will tighten them to 10 µg/m³ annual average by 2030 — still double the WHO target.

Action table based on PM2.5 level

At 50 µg/m³ — France's own alert threshold — even healthy adults should limit their outdoor exposure. At the levels recorded near Fontainebleau and Bordeaux in 2026, the only sensible response is to treat the outdoor air as a dangerous environment.

A surgical mask or cloth face covering does not filter PM2.5. Effective protection requires a respirator rated FFP3 (European standard) or N100/P100 (American standard), which filters ≥ 99% of particles in the relevant size range.

FAQ

What are the main symptoms of smoke inhalation to watch for?

The most common immediate symptoms are coughing, throat irritation, shortness of breath, wheezing, and stinging or watery eyes. More severe signs — chest tightness, difficulty breathing, accelerated heart rate, confusion — require medical attention. Symptoms can appear several hours after exposure and persist for several days.

Is wildfire smoke more dangerous than typical urban pollution?

Data suggest yes, for an equivalent concentration of PM2.5. Wildfire PM2.5 has a higher organic carbon content and a greater oxidative potential than typical urban PM2.5, which could cause more cellular damage per microgram inhaled. It also carries a larger load of VOCs and PAHs.

How far from a fire does smoke remain dangerous?

Very far. During the Gironde fires in 2022, smoke was detected above Paris — more than 500 km away. PM2.5 particles can remain suspended for several days and travel thousands of kilometers. If your local sensor indicates high PM2.5, the source could be a fire hundreds of kilometers away.

Do N95 or FFP2 masks protect against wildfire smoke?

N95 and FFP2 masks filter ≥ 95% of airborne particles and offer real protection against PM2.5. However, FFP3 or N100/P100 masks (≥ 99–99.97% filtration) offer superior protection, especially during prolonged outdoor exposure or for individuals with respiratory conditions. Fit matters as much as the rating: a poorly fitted N95 provides far less protection than its specification suggests.

Can children wear an anti-pollution mask during a smoke event?

Yes, but the mask must be specifically sized and approved for children. Adult masks do not seal properly on a child's face, negating most of the filtration benefit. During severe episodes, the priority for young children should be to stay indoors, with windows sealed, and if possible, a HEPA air purifier running.

Protect your lungs when the air becomes unbreathable

You can't choose the outdoor air quality, but you can choose what you breathe. The R-PUR Nano range filters particles down to 0.05 µm — well beyond the FFP3 threshold — and includes an activated carbon layer against VOCs, benzene, and smoke odors. Protection designed to be worn every day, not just in emergencies.

Useful Resources

• WHO — Global Air Quality Guidelines 2021
• Airparif — Fontainebleau Fires 2026
• EPA — Wildfire Smoke: A Complex Mixture
• EPA — Health Effects Attributed to Wildfire Smoke
• Circulation (AHA, 2022) — Wildfire PM2.5 and Cardiovascular Risk
• Harvard T.H. Chan SPH (2023) — Persistent Cardiorespiratory Effects
• Yale SPH (2024) — Long-term Exposure and Mortality
• EEA Climate-Adapt — Wildfire Smoke in Europe
• Airparif — Air Quality Regulations in France
• Copernicus — Extreme Wildfires and Air Pollution Levels