As per combining of corn, bees collecting dust.  The bees don't need  to be 
anywhere near the combines.  
 
Based on years of using bees as environmental sentinels, chemical samplers  
- we know that the body of  each flying bee is electrostatically  charged.  
Under a microscope, one can see dust particles, spores, bacteria  adsorbed 
(and yes, I meant to say adsorb rather than absorb) to the  cuticle.  We've 
even modeled uptake based on particle size and  charge.
 
For any chemical that adheres to dust, the route of exposure for bees is  
not simply pollen, nectar.  The dust itself (soils, re-entrained soil  dust, 
plumes from factories) may be as important in terms of exposure  levels or 
even more so than exposures from pollen or  nectar. 
 
That's certainly the case near industrial sources that emit plumes  
containing heavy metals.  In exclusion trials, we found that the majority  of the 
exposure of bees to materials like arsenic, cadmium, zinc, copper was  from 
the dusts that sorbed on their bodies.  The next highest route of  exposure, 
but still trivial compared to the direct dust exposure, was  pollen.  Nectar 
was a distant 3rd.
 
Also, even inert dusts can be hazardous to bees.  The spiracle aren't  well 
designed to shield the bee from dust, smothering.  And the materials  may 
act as dessicants and abrasives.  Mt St Helen's ash was mostly inert,  but it 
caused brood breaks and some adult bee losses.
 
 
Jerry

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