Having made the switch from power to hand tools in the past 2 years, my non-scientific assessment is that I can do a great deal of sawing and planing without getting a layer of dust on every surface 4 feet away, as long as I dont blow away the dust, but sweep or vac it up.
If I were using a sander or a router without powered dust collection there would be dust everywhere even 12 feet away.
Just look at dust from a random orbit sander compared to a 12tpi backsaw under a loupe. The body is better equipped to rid itself of the larger dust.
Of course, woods that have greater toxicity present very different problems.
All this is merely the opinion of a person without any scientific or medical training.