Cars are a significant source, though in China "industry" is a bigger source per [0]. I'm not sure what the ration worldwide (and I didn't find a global number

Cars are a significant source, though in China "industry" is a bigger source per [0]. I'm not sure what the ration worldwide (and I didn't find a global number in the quick search that found the links I am posting). Crop residue burning also comes to mind as a source that would be particularly concentrated near... crops [1]. [0] https://www.acarindex.com/pdfler/acarindex-4786c244-1875.pdf https://www.acarindex.com/pdfler/acarindex-4786c244-1875.pdf [1] https://www.researchgate.net/publication/348764564_Estimation_of_Field-Level_NOx_Emissions_from_Crop_Residue_Burning_Using_Remote_Sensing_Data_A_Case_Study_in_Hubei_China https://www.researchgate.net/publication/348764564_Estimatio...