Dust probably is the least likely reason for few flowers. A plant's age is a factor, too much fertilizer is another, cold injury to the flower bud is another reason, pruning can be a factor too. Drought in one year can affect the number of flowers the next year. Diseases should also be considered.
You should also know that when this tree gets about 25 years old or older, it will begin to brak apart. The tree has very narrow branch crotches so they are weak and break easily in high winds or under heavy snow and ice loads.