Wildfires release significantly more pollutants into the atmosphere than previously thought, mainly due to gases that easily transform into harmful particles. This helps explain why wildfire smoke can have long-lasting and serious effects on air quality and human health.

New Data on Wildfire Emissions

As wildfires spread through forests, grasslands, and peatlands, they emit large amounts of gases and particles into the air. Recent studies show that pollution from such fires has been underestimated in the past. An article published in the journal Environmental Science & Technology by the American Chemical Society notes that wildfires and controlled burns worldwide likely emit much more air-polluting gases than previously assumed. The study also highlights regions where wildfire emissions overlap with pollution from human activities, creating particularly complex air quality challenges.

The Importance of Accounting for Different Organic Compounds

According to the study’s lead author, Luyin Huang, new estimates increase the reported emissions of organic compounds from wildfires by about 21%. This updated inventory provides a foundation for more accurate air quality modeling, health risk assessments, and climate policy analysis. Each year, wildfires burn vast areas of vegetation, releasing a complex mix of water vapor, ash, and carbon-based chemicals into the atmosphere.

Some of these chemicals are volatile organic compounds (VOCs), which easily exist as gases. Others only evaporate and become gases at higher temperatures and are classified as intermediate and semi-volatile organic compounds (IVOCs and SVOCs, respectively). Once in the air, these partially volatile compounds more readily form fine particles that can be harmful when inhaled, compared to VOCs.

Underestimated Chemicals in Smoke

Despite their importance, IVOCs and SVOCs are often missing from wildfire emission studies. Their abundance and chemical complexity make them difficult to measure, so many previous estimates focused mainly on VOCs. A research team led by Shuxiao Wang decided to include IVOCs and SVOCs alongside VOCs to better understand how wildfires affect air quality, human health, and the climate.

To do this, the team analyzed a global database tracking burned areas from forest, grassland, and peat fires from 1997 to 2023. They then gathered information on emissions of VOCs, IVOCs, SVOCs, and other organic compounds with extremely low volatility, released during the burning of various types of vegetation. When direct field measurements were unavailable, laboratory experiments were used to estimate the chemicals produced. All this data was combined to calculate annual wildfire emissions worldwide.

Global Figures and Key Pollution Regions

According to the estimates, wildfires released an average of 143 million tons of organic compounds into the atmosphere each year during the study period. This figure is about 21% higher than previous estimates, indicating that wildfire emissions—especially IVOCs and SVOCs—contribute more to air pollution than previously believed.

When comparing wildfire emissions to pollution from human activities, researchers found that anthropogenic sources generally produce more organic compounds overall. However, both sources emit similar amounts of IVOCs and SVOCs. The analysis also identified major emission hotspots, including equatorial Asia, northern Africa, and Southeast Asia. Scientists believe that air pollution in these regions is especially complex and requires different strategies to reduce emissions from both wildfires and human activities.