That is what I suggest, and please note that the particles that I'm looking at, for example, are chemicals. Many of the contaminants in the air we are talking about are actually in the soil and the water, but because of the wind and the atmospheric processes, they have a chance to have an affect, not only locally but at a longer distance. Those are also chemicals.
One thing you mentioned that I would like to point out is that the contaminant you start with is not necessarily the contaminant you end up with. It undergoes chemical, physical, and photochemical transformation. Sometimes it's a deposit. Sometimes it's a nucleate, and so forth.