Esters of o-phthalic acid are widely distributed in the ecosystem. The phthalate acid esters (PAE's) are used as plasticizers in enormous quantities for a variety of industrial uses in the formulation of plastics. They are also used as solvents in certain industrial processes and as vehicles for pesticides and have been described as being among the most abundant man-made environmental pollutants. Plasticizers have been shown to elute at a constant rate from plastic products to the environment. Increasing chemical use needs a better understanding of how these pollutants may affect human health. In particular, certain members of this chemical class, such as di-[2-ethylhexyl]-phthalate (DEHP), have been shown to cause reproductive and developmental toxicity and are suspected to be endocrine disruptors.