What Is Wildfire Smoke, and Why Should You Care?

Wildfire smoke has been one of the most harmful forms of air pollution we face in Sonoma County. As wildfires grow more intense and frequent due to climate change, exposure to wildfire smoke is becoming a major public health issue, even in communities far from the flames.

Wildfire smoke contains a toxic mix of gases and fine particles, including:

• PM2.5 – microscopic particles that can penetrate deep into the lungs and bloodstream (US EPA)

• Carbon monoxide – especially dangerous for people with heart conditions (AirNow)

• Volatile Organic Compounds (VOCs) – such as benzene and formaldehyde (NIH)

• Heavy metals and dioxins – when structures and synthetic materials burn (Environmental Health Perspectives)

• Black carbon – a short-lived but potent climate pollutant (Climate Central)

When homes, cars, and infrastructure burn, they release additional synthetic chemicals, plastics, and heavy metals into the air. This makes the smoke from today’s wildfires significantly more toxic than natural wood smoke alone (Harvard T.H. Chan School of Public Health).

How People Are Exposed

Smoke doesn’t respect boundaries. It can travel hundreds of miles, affecting communities far from the fire zone.

Ways people are exposed include:

• Breathing outdoor air during smoke events, especially without proper filtration or masks (US EPA)

• Indoor air contamination, especially in older or poorly sealed homes (EPA Science Inventory)

• Workplace exposure for outdoor laborers, farmworkers, and emergency responders (Cal/OSHA)

• Children in schools without adequate air filtration (UCSF News)

Wildfire smoke can enter homes through small cracks and HVAC systems. During major events, PM2.5 levels indoors can become dangerously high even when windows are closed (EPA Indoor Air Quality).

Known and Suspected Human Health Effects

Wildfire smoke has been linked to a wide range of serious health problems, especially for vulnerable populations.

Respiratory & Cardiovascular Effects

• Increased asthma attacks, COPD flare-ups, and respiratory ER visits (CDC)

• Reduced lung function, even in healthy adults (Stanford University, 2022)

• Higher risk of heart attacks and strokes during smoke events (New England Journal of Medicine)

Developmental and Immune System Effects

• Low birth weight and premature birth (Environmental Health Perspectives, 2021)

• Increased respiratory infections in children (NIH)

• Immune suppression and decreased vaccine response (NIEHS)

Mental Health and Cognitive Impacts

• Elevated anxiety, sleep disturbance, and PTSD symptoms during and after fire events (International Journal of Environmental Research and Public Health)

• Possible long-term neurological impacts of repeated exposure (NIEHS Superfund Research Program)

Exposure to wildfire smoke is also associated with increased COVID-19 susceptibility and severity, particularly among people with chronic respiratory conditions (Harvard Chan School, 2020).

Why This Matters for Our Communities and in Public Policy

Wildfire smoke is both a climate consequence and a climate driver—it not only results from worsening fire seasons but also contributes to them. Smoke releases large amounts of carbon dioxide and black carbon, exacerbating the very warming that fuels more fires (California Air Resources Board).

The burden of smoke exposure is not shared equally. Farmworkers, unhoused individuals, and low-income residents often face the highest exposure and have the fewest resources to cope. (California Department of Public Health – Office of Health Equity)

To protect public health, we urgently need:

• Clean air shelters and portable HEPA filters for homes and community spaces

• Worker protections during smoke events

• Climate policies that reduce fire risk, including forest stewardship and emissions reduction

• Health-based air quality alerts and forecasting for rural and vulnerable communities

Wildfire smoke is now the leading cause of air pollution in the western U.S. (Nature Communications, 2023). The science is clear, the impacts are serious, and the need for action is urgent.

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