Wildfire smoke has reversed US progress toward ozone air quality, study finds

Since 2015, fires have undone years of effort to reduce ozone levels, underscoring a growing public health crisis

The highly destructive wildfires that have battered the US and North America in recent years have significantly increased emissions and been linked to tens of thousands of premature deaths, but their impact on air quality is greater than previously known, according to new research.

A study published in Science on Thursday found that, since 2015, wildfires have reversed US progress toward ozone air quality standards, as the worsening pollution caused by wildfire smoke has undone years of efforts to reduce emissions. Ground-level ozone (O3) is created when pollutants from cars, refineries and industrial sources react with sunlight, according to the Environmental Protection Agency.