text: A particle which is not obviously a consecrated host does not have the sign of the sacrament  and therefore is not the Presence  .
  Therefore Christ is not being stepped on .  The sign is not recognizeable.
  I agree if in the hand in which I have just received communion I see a very small particle I would treat it as the Presence since it may or may not be such and I have no way of knowing .
  Remember it takes intention to commit sin as well as to do good  .
  And in a church building those white specks could be any number of things .   Scrupulosity is a torture which the Savior never saw as healthy  . Nor should we .