Erin Davis/Axios Visuals Air quality is worsening in the Upper Midwest and Northern California, according to year-over-year data. Why it matters: Poor air quality can lead to long-term health problems ...

Flying through Bangkok's cloudless blue skies, a small aircraft sprays a white mist over a thick haze of pea soup smog below.

Southeast Asian cities were among five most polluted in the world on Friday according to air-monitoring organisation IQAir, ...