Researchers are expressing hope for the future of Houston's breathable air, despite the city's poor rankings in the American Lung Association's 2019 'State of the Air' report. The report, released in April, ranked Houston ninth nationally for worst ozone pollution and 17th for particle pollution. Researchers say replacing at least 35 percent of Houston's gasoline cars and diesel trucks with electric vehicles by 2040 will reduce pollution and improve air quality by 50 percent.