Sounds absolutely ridiculous to me. I suppose I could imagine where it could be possible for more dust to enter a zoom lens than a prime but I would have to see persuasive proof of that; but to say that more dust can then get to the CCD is a bit much.
It seems to me to be another case of the old prime lens bigots finding one more thing to attack about zoom lenses. i see a lot of bandwidth devoted to prime lens advocates screaming about low quality zooms - of which there are, no doubt, some. Interestingly, I have had the opportunity to work with several respected and talented professionals in the past two years and they ALL shoot almost exclusively with various zooms.
There, I have been wanting to let loose with that rant for some time .