This happens because, once ammonia is abundant in the air, as it is in this region, the amount of haze-forming nitrate depends less on how much NOx is emitted and far more on how "oxidizing" the atmosphere is, that is, how actively sunlight and reactive chemicals convert pollutants into particles. "Our data show that visibility in this region is no longer just a story about NOx and vehicle exhaust – industrial solvent vapors are now writing a big part of that story, and controlling them is essential to seeing clearer skies again," says corresponding author Prof. Ta-Chih Hsiao.