A new study published in *Science* finds that wildfire smoke is contributing to a reversal of US progress toward meeting ground-level ozone air quality standards. Researchers report that, since around 2015, ozone pollution has worsened in much of the continental United States, reversing gains made through efforts to reduce emissions. The study links the increase to emissions from wildfires as well as the transport of polluted air over long distances. Ground-level ozone forms when pollutants emitted from sources such as cars, refineries, and industrial activity react in the presence of sunlight. The authors conclude that wildfire-related emissions and smoke are undoing reductions that had been achieved through prior control measures. The findings are presented as evidence of a growing public health concern tied to worsening air quality during and after major fire events, with the smoke raising ozone levels beyond what would be expected from other trends alone. The research is led by University of Iowa scientists, and the results emphasize how climate-driven wildfire activity can affect air quality regulation and public health outcomes.