Spray tans have become a more and more popular alternative to the harmful use of tanning beds, but now researchers are saying that the main ingredient is potentially harmful if inhaled.  Scientifically, the substance is known as dihydroxyacetone or DHA.  DHA is a simple sugar derived from the sugar cane plant. It works as a color additive used in cosmetics and is approved by the FDA for topical use.  The way it works is that the …