West Virginia, Kentucky, Louisiana, Florida and Mississippi ranked lowest on the 50-state scorecard produced by the Commonwealth Fund, a foundation that advocates for health care improvements. Climate change poses a severe threat to public health, leading health organizations have warned. Poor air quality, for example, contributes to between 100,000 and 200,000 excess U.S. deaths per year. Arizona and California had the poorest air quality, most likely driven by ground-level ozone, wildfire smoke and dust, the researchers said. They used the federal air quality index, which estimates levels of five main air pollutants, to score the states on air quality.