The gases that cause the visible pollution, and smog in places like Los Angeles and Beijing and Hong Kong, are mainly suplhur dioxide and nitrous oxides. Catalytic converters fitted to motor vehicles are fitted to reduce the output of these gases.
They react chemically to cause sulphuric and nitric acids, and are nasty gases.
Carbon monoxide is a poisonous gas produced from many sources including petrol engine exhausts, less so from diesels. The reason for that is that carbon monoxide results from burning fuel with less than the ideal amount of oxygen needed to burn completely. Diesels by design, and in good condition, always have an excess of oxygen, so less carbon monoxide is produced. Petrol engines also exhale benzene which is a known carcinogen. It is not well-known that when lead was removed from petrol, the benzene output increased.
Carbon dioxide is chemically almost inert, and is the main cause of the greenhouse effect. It is not poisonous in the sense of toxic poisons. And it plays little part in causing visible smog for that reason.
Getting rid of carbon dioxide may change the greenhouse effect, but it will have no effect at all on the visible smog.
There is obviously much ignorance of even basic chemistry at government level. Carbon dioxide pollution is a meaningless phrase. Similarly, carbon-pollution is also a bit of an oddity, because pure carbon is mostly soot, which in the air soon falls harmlessly to the ground. The purest form of carbon is of course diamond.
The questions that needs to be asked is; Do we want to get rid of the greenhouse effect? And do we want to get rid of smog? The two are entirely different subjects.
