NASA-backed study finds wildfire smoke has erased years of ozone progress across much of the US

Wildfires are now reshaping ozone pollution far from the flames

A NASA-supported study published in Science says wildfire smoke has become a major driver of ground-level ozone pollution across much of the contiguous United States. According to the findings, fires have offset nearly four years of ozone-control gains nationwide over the last decade, with larger setbacks in the West and Midwest.

The result broadens how wildfire damage should be understood. Smoke is often discussed in terms of visible haze and fine particles, but the study highlights a less obvious effect: the role of wildfire emissions in producing surface ozone, the pollutant better known as smog.

How smoke turns into an ozone problem

Wildfires release more than soot and ash. They also emit gases such as carbon monoxide, which can help create ground-level ozone when sunlight and other pollutants are present. As smoke plumes travel and mix with existing pollution, those reactions can unfold hundreds or even thousands of miles from the fire itself.

That makes ozone from wildfire smoke a regional and even cross-country air quality issue, not only a local one. Communities far from active fire zones can still experience unhealthy air because of atmospheric chemistry set in motion elsewhere.

NASA’s Earth Science team framed the study as an example of how satellite observations and ground monitoring can be combined to help air-quality managers respond to smoke that crosses state lines.

A new dataset sharpened the picture

To trace changes in surface ozone, researchers used deep learning to assemble what NASA described as a first-of-its-kind dataset estimating daily surface ozone from 2003 through 2024 on a kilometer-by-kilometer grid. That scale matters because ozone formation is spatially uneven, and wildfire impacts can shift quickly as smoke disperses and reacts in sunlight.

By combining observational data with machine-learning methods, the researchers were able to build a clearer long-term map of how wildfire activity is changing ozone exposure across the country. The conclusion is stark: gains made through traditional ozone-control measures have increasingly been counteracted by fire-driven pollution.

Why this matters for public health and agriculture

High in the atmosphere, ozone shields Earth from harmful ultraviolet radiation. Near the surface, it does the opposite of protecting life. Ground-level ozone can irritate lungs, worsen asthma and other respiratory disease, and raise risks for children, older adults, outdoor workers, and people with underlying conditions.

The damage is not limited to human health. Surface ozone is also harmful to plants and crops, which means wildfire-driven smog can carry agricultural consequences as well as medical ones.

The report arrives at a time when wildfire seasons in North America are already affecting communities well beyond traditional fire zones. Smoke events that once seemed episodic are becoming part of the baseline risk environment for air quality management.

The policy implication is broader than firefighting

The study does not suggest conventional emissions controls were ineffective. Instead, it shows they are increasingly being challenged by a growing source of pollution that behaves differently from tailpipes and smokestacks. Wildfires are now large enough, frequent enough, and chemically consequential enough to materially alter ozone trends.

That means air-quality planning may need to treat wildfire smoke as a structural part of ozone management rather than an exceptional disruption. NASA’s emphasis on Earth observations and decision support reflects that shift. If smoke can push ozone upward far from the burn area, regulators need tools that track atmospheric transport and chemistry across jurisdictions.

• The study says wildfires offset nearly four years of ozone-control gains in the US
• Setbacks were especially pronounced in the West and Midwest
• Wildfire smoke contributes to ozone through gases including carbon monoxide
• Researchers built a daily ozone dataset spanning 2003 to 2024 at kilometer-scale resolution

This article is based on reporting by science.nasa.gov. Read the original article.