All contaminants of the air can be divided into two groups. what are they?

Air contaminants can be divided into two main groups: primary pollutants and secondary pollutants. Primary pollutants are directly emitted into the atmosphere from sources such as vehicles, industrial processes, or natural events, and include substances like carbon monoxide, sulfur dioxide, and particulate matter. Secondary pollutants, on the other hand, are formed through chemical reactions in the atmosphere, such as ozone and smog, which result from the interaction of primary pollutants with sunlight and other atmospheric components.