Phthalates, or phthalate esters, are esters of phthalic acid and are mainly used as plasticizers (substances added to plastics to increase their flexibility, transparency, durability, and longevity). Phthalates are manufactured by reacting phthalic anhydride with alcohol(s) that range from methanol and ethanol (C1/C2) up to tridecyl alcohol (C13), either as a straight chain or with some branching. They are divided into two distinct groups, with very different applications, toxicological properties, and classification, based on the number of carbon atoms in their alcohol chain. They are used primarily to soften polyvinyl chloride (PVC). Lower-molecular-weight phthalates (3-6 carbon atoms in their backbone) are being gradually replaced in many products in the United States, Canada, and European Union over health concerns.[citation needed] They are replaced by high-molecular-weight phthalates (those with more than 6 carbons in their backbone, which gives them increased permanency and durability). In 2010, the market was still dominated by high-phthalate plasticizers; however, due to legal provisions and growing environmental awareness and perceptions, producers are increasingly forced to use non-phthalate plasticizers.
Phthalates are used in a wide range of common products, and are released into the environment. There is no covalent bond between the phthalates and plastics; rather, they are entangled within the plastic as a result of the manufacturing process used to make PVC articles.They can be removed by exposure to heat or with organic solvents. Due to the ubiquity of plastics (and therefore plasticizers) in modern life, the vast majority of people are exposed to some level of phthalates, and most Americans tested by the Centers for Disease Control and Prevention have metabolites of multiple phthalates in their urine.Phthalate exposure may be through direct use or by indirect means through leaching and general environmental contamination. Diet is believed to be the main source of di(2-ethylhexyl) phthalate (DEHP) and other phthalates in the general population.Fatty foods such as milk, butter, and meats are a major source. In studies of rodents exposed to certain phthalates, high doses have been shown to change hormone levels and cause birth defects.