Laineygal,
http://www.belgard.biz/docs/Efflorescence-brochure.pdf
Ironically from the Belgarde site, the link discusses efflorescence, and more direct ways of removing it.
https://www.ephenry.com/Common/efflorescence_popup.htm
from EP henry, which I am installing (just 100 sq ft to go - yah!) also references the same ICPI document.
BTW, a number of my pavers already have it as I have been loading them off the pallets. Therefore, I would think Polysand is not the cause.
Time and tide will hopefully take care of it.