(NewsNation) — Increased smoke from wildfires is reversing decades of clean air progress achieved by regulating pollution, a new study found.

The study, published in Nature, used ground and satellite data to identify the impact of smoke on air quality.

Researchers found smoke rolled back about a quarter of the progress gained over decades of work to reduce pollutants in the air using the Clean Air Act.

Some states were more affected than others, with the West being most impacted by fires in the region. However, many other parts of the U.S. have also seen the impact of wildfire smoke from fires in Canada that drifted down to cities, covering them in a haze.

Scientists attributed human-driven climate change as one factor fueling wildfires. Wildfire smoke is not regulated, though the Biden administration has pushed for more prescribed burns and projects to thin and clear debris that can increase the size of wildfires.

Wildfire smoke can impact human health, particularly for those who are vulnerable due to respiratory or other chronic health conditions.