Polyvinyl chloride (PVC), a thermoplastic resin, is among the top three most widely used plastics in the world. PVC is used in a diverse number of applications. Some of these include construction materials, packaging materials, and water transportation pipes. PVC is also heavily used in internal automobile parts: up to 80% of internal automobile parts are composed of PVC. PVC is made by a polymerization reaction of the monomer vinyl chloride.

                                                                     Wypych, George, Handbook of Plasticizers, 2004.

Figure 1 Polymerization reaction of PVC.

A phthalate ester, di(2-ethylhexyl) phthalate (DEHP), is often added as a PVC plasticizer to impart flexibility. Plasticizers function by interfering with the crystalline structure of the PVC matrix, so that the PVC chains can slip past one another. Refer to figure 2 below. Commercial PVC plastics contain up to 40% by weight of DEHP.

                                                          Wypych, George, Handbook of Plasticizers, 2004.

Figure 2 Diagram showing plasticization.

With 3-4 million tones of DEHP being produced annually, the phthalate is causing increasing alarm as a pollutant in many countries. 95% of DEHP produced is used as PVC plasticizers. The general population is exposed to DEHP since PVC is used in such diverse application and that DEHP is leaches through consumer products. DEHP, bound by only weak van der Waals forces, is not chemically bound to PVC and so is prone to leaching into the environment. DEHP emission occurs during plastic production, use, and after disposal. Once disposed of, DEHP does not undergo significant physio-chemical degradation.

In medical applications, DEHP can leach out from the materials and travel into the media. There has been increasing concern regarding how DEHP exposure impacts human health through medical procedures such as intravenous therapy, enteral and parenteral nutrition support, blood transfusion, hemodialysis, and extracorporeal membrane oxygenation, and how exposure impacts the environment and wildlife through leaching from water pipes and landfills. Though DEHP is suggested to be of low acute toxicity, long-term exposure may have an adverse effect on human health. Studies of risk assessment have shown that DEHP has critical effects on fertility, endocrine system, kidneys and development. The Food and Drug Administration has issued a report acknowledging that PVC medical devices are a concern to critically ill infants.  Furthermore, studies suggest that chemicals with the ability to disrupt the endocrine system are a potential threat to the health of humans, aquatic animals, and wildlife. For aquatic organisms, there have been several cases of documentation on the adverse effects of DEHP on Daphnia and fish species.  Another DEHP study has pointed towards the perturbation of normal metabolism in liver, heart, testes, adrenal gland, and brain in mammals such as rats, rabbits, and pigs.

The adverse effects of DEHP pose potential environmental and health risks through leaching, making DEHP harmful in terms of production, use, and disposal. To address the source of the problem, we hoped to reduce emissions of DEHP by finding suitable, safe, and biodegradable alternative PVC plasticizers.