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When there's a lot of outdoor wind and indoor traffic moving particles about, it is perfectly reasonable to suppose that some (perhaps a small minority) of particles will remain floating about in the air. The question then resolves to the potency of some given sample of material, and where the proportion of material is. I would suppose that the large bulk of material is on surfaces, while a minority is found in the ambient air. I propose that this hypothesis be tested by an experiment.
Another possible consideration: children, especially ambulatory small children, who are much closer to the ground, and much more apt to stick their faces and hands into everything. If particles eventually settle toward the ground perhaps taking their sweet time about it, then it is much more likely that small children will pick them up. Germane to all these considerations are the environments in which families and small children find themselves tightly confined at present: grocery stores.
