photochemical smog

On the last day of too hot June, a photochemical smog warning was issued in Minato Ward.
Was the announcement made over the disaster prevention radio?
I am not sure if photochemical smog is the correct word in English, but it has been a long time since I last heard it.
It reminds me of the elementary school students in Kawasaki and Sagamihara City who used to fall ill.
I think the atmospheric environment has become much cleaner due in part to former Tokyo Governor Ishihara's diesel regulations.