Soot pollution consists of tiny droplets or particles in the air. The smallest particles are no more than 2.5 microns wide—30 times smaller than the width of a human hair. These tiny particles, also called PM2.5 or particle pollution, are easily inhaled and can become embedded in our lungs and pass directly into the bloodstream.

Soot can come from a wide variety of sources. One of the largest sources of soot pollution is the burning of fossil fuels by coal-fired power plants, industrial facilities, and combustion engines. Particle pollution is also emitted by wildfires, agriculture, vehicle tires/road dust, and volcanic eruptions.

Particle pollution is one of the leading causes of premature death worldwide. Researchers estimate that in 2018, more than 8 million people died from fossil fuel pollution—that means air pollution from burning things like coal and diesel accounted for about a fifth of deaths worldwide.

Soot can affect our health in many other ways too; it can contribute to asthma attacks, respiratory illness, lung cancer, impaired immune health, heart attacks and strokes, metabolic disorders like diabetes, preterm birth and low birth weight, and nervous system impacts, including cognitive effects.

Communities of color and economically disadvantaged communities bear a disproportionate burden of the health impacts from soot, as they often live near pollution sources like high-traffic roads and heavily polluting industrial facilities. Older adults, people with certain chronic health conditions, and people who spend a lot of time outside, like outdoor workers, are also at higher risk for adverse impacts from PM2.5. Black communities with greater exposure to air pollution have higher than average childhood asthma rates, and Black children have a 500% higher mortality rate from asthma than white kids.

EPA sets standards for common air pollutants that affect our health, including soot pollution. These are called the National Ambient Air Quality Standards, or NAAQS (rhymes with “snacks”). In proposing NAAQS for soot pollution, EPA relies on scientific guidance from the Clean Air Scientific Advisory Committee (CASAC).

The 2024 soot protections are the first update to the PM2.5 NAAQS since 2012. In the last decade, scientists have learned a lot more about how dangerous soot pollution is for our health. That’s why we will stand up to protect the new rule from rollbacks by the Trump administration and continue to call for strengthening the daily soot standards to protect our families’ and communities’ health.