It's even more amazing when you look at a satellite map of the city. It consists mostly of warehouses, industry and a rock quarry. You'd think they would want companies like Huy Fong Foods. https://maps.google.com/?q=Irwindale,+CA
The AQMD is one of the shadiest governmental agencies there is - apparently their main function is to demand enough shakedown money from SoCal businesses so they leave town.
See http://www.latimes.com/local/la-me-1110-sriracha-20131110,0,..., also posted in another comment on this thread.