A lot of people use laundry detergents that contain optical brighteners. Their purpose is to make the clothes brighter or whiter than they are. They remain on the clean clothes as a covering of microscopic fluorescent particles. Optical brighteners are synthetic chemicals that make fabrics appear to glow in the presence of ultraviolet light and make us think that our clothes are very clean. A lot of optical brighteners are derived from benzene which is quite dangerous substance. Benzene do not break down in the environment and stays in the water where it poisons the fish and other aquatic life.