Wildfire ash is toxic and a serious health hazard

Ash from wildfires is more than just dust; it contains toxic particles from burned vegetation, building materials, and chemicals. Breathing in ash can have immediate and long-term effects on your health, including:

• Short-term effects: Coughing, throat irritation, and shortness of breath.
• Long-term effects: Prolonged exposure can increase the risk of respiratory diseases, heart disease, and even cancer due to carcinogenic compounds in the ash.

Certain populations, such as children, pregnant people, older adults, and those with pre-existing respiratory or heart conditions, are especially vulnerable.

Understanding the disconnect between AQI and wildfire ash

It’s a perplexing scenario: You check your local air quality map, and the Air Quality Index (AQI) shows a reassuring green, indicating “good” air quality. Yet, outside your window, ash is visible in the air or blanketing outdoor surfaces. How can the air quality appear fine while wildfire ash poses a very real health risk?

The discrepancy lies in how AQI is calculated. The AQI is calculated from measured levels of the five major air pollutants that are regulated by the Clean Air Act. Those include particle pollution of specific size ranges (PM10) and (PM2.5), as well as carbon monoxide, nitrogen dioxide, and sulfur dioxide gaseous pollutants. Wildfire ash particles are typically larger than the particle size range measured for the AQI (larger than PM10) and fall outside the range of what most air quality sensors can detect.

As Dr. Scott Epstein, an air quality assessment manager at AQMD, explains, “Windblown ash particles may be too large to be detected by air-quality instrumentation and not reflected in the Air Quality Index (AQI) map. Although the AQI may show green, hazardous ash may still be present in the air.” (1).

This is particularly relevant in wildfire-prone areas during strong winds, which can stir up ash from burn scars even after fires have been extinguished.

The unique health risks of wildfire ash 

The particulate matter pollutants incorporated into the AQI (PM10 and PM2.5) typically pose the greatest health threat because they can penetrate deeply into your lungs and bloodstream. Wildfire ash contains particles that are larger and can be seen with the naked eye. The body has natural defenses to prevent particles of this size from entering the lungs, but they can significantly irritate the eyes, nose, and throat (2).

If you see ash, avoid it, it’s a serious health concern

Wildfire ash is more than just a nuisance—it’s a toxic mixture of particles from burned vegetation, construction materials, and household items, many of which contain harmful chemicals and carcinogens. These particles can irritate your respiratory system and exacerbate conditions like asthma or heart disease. Even brief exposure to ash can lead to coughing, throat irritation, or difficulty breathing, particularly for vulnerable groups like children, older adults, pregnant people, and those with pre-existing health conditions. 

If you see ash outdoors, avoid disturbing it, as sweeping or blowing it into the air increases the risk of inhalation. Instead, take precautions to minimize contact, such as staying indoors, using and wearing a properly fitted mask if outdoor cleanup is unavoidable.

How to protect yourself from wildfire ash

Even if AQI maps show “good” or “moderate” air quality, visible ash or the smell of smoke is a clear indicator to take precautions. Here’s what you can do to stay safe (3)(4):

Before Wildfire Season: Be Prepared

1. Stay Informed:

• • Get real-time air quality alerts by downloading a free air quality app.
  • Check your air quality both indoors and outdoors with an air quality monitor.

2. Prepare Your Home:

• • Install high-efficiency (MERV 13 or higher) filters in your HVAC system.
  • Run an air purifier for wildfire smoke to create a “clean room” in your home.

3. Stock Up on Masks:

• • Keep a supply of face masks on hand to protect yourself when outdoors.

4. Plan Ahead for Medical Needs:

• • If you or a family member has asthma or other respiratory conditions, consult your doctor and have at least a five-day supply of medication.

5. Use Generators Safely:

• • If you plan to use a generator during power outages, place it outdoors, at least 20 feet from your home, to avoid carbon monoxide poisoning.

During a Wildfire: Minimize Exposure

1. Stay Indoors:

• • Close all windows and doors. If you have an HVAC system, run it with a clean filter and close the fresh air intake.

2. Create a Clean Room:

• • Use an air purifier in a frequently used room (like a bedroom or living room) to filter out harmful particles.

3. Limit Outdoor Activities:

• • Avoid going outside unless absolutely necessary. If you must go out, wear a properly fitted mask.

4. Avoid Adding Indoor Pollutants:

• • Refrain from burning candles, using fireplaces, or running gas stoves, as these can worsen indoor air quality.

After a Wildfire: Clean Up Safely

1. Use Protective Gear:

• • Wear goggles, gloves, and a mask when cleaning ash. Avoid direct skin contact.

2. Clean Gently:

• • Lightly mist ash with water before sweeping to avoid stirring it back into the air. Avoid using leaf blowers.

3. Dispose of Ash Properly:

• • Place ash in a sealed plastic bag and dispose of it with regular trash.

4. Wash Pets and Toys:

• • Remove ash from outdoor toys and pets to prevent them from bringing ash indoors.
    

The takeaway

While AQI maps are a helpful tool for tracking common air pollutants, they may not tell the full story—especially when it comes to wildfire ash. If you see ash in the air or on surfaces, take steps to protect yourself and your family.

By preparing your home, creating a clean indoor environment, and using protective equipment, you can reduce exposure to ash and safeguard your health—even when the AQI appears deceptively green.