Phthalates

Phthalates, or phthalate esters, are a group of chemical compounds that are mainly used as plasticizers (substances added to plastics to increase their flexibility). They are chiefly used to turn polyvinyl chloride from a hard plastic into a flexible plastic.

Properties
Phthalate esters are the dialkyl or alkyl aryl esters of 1,2-benzenedicarboxylic acid; the name phthalate derives from phthalic acid. When added to plastics, phthalates allow the long polyvinyl molecules to slide against one another. The phthalates show low water solubility, high oil solubility, and low volatility. The polar carboxyl group contributes little to the physical properties of the phthalates, except when R and R' are very small (such as ethyl or methyl groups). They are colorless, odorless liquids produced by reacting phthalic anhydride with an appropriate alcohol (usually 6 to 13 carbon).

As of 2004, manufacturers produce about 400,000 tons (800 million pounds or 363 million kilograms) of phthalates each year. They were first produced during the 1920s, and have been produced in large quantities since the 1950s, when PVC was introduced. The most widely used phthalates are di-2-ethyl hexyl phthalate (DEHP), diisodecyl phthalate (DIDP) and diisononyl phthalate (DINP). DEHP is the dominant plasticizer used in PVC, due to its low cost. Benzylbutylphthalate (BBzP) is used in the manufacture of foamed PVC, which is mostly used as a flooring material. Phthalates with small R and R' groups are used as solvents in perfumes and pesticides.

Phthalates are also frequently used in nail polish, fishing lures, adhesives, caulk, paint pigments, and sex toys made of so-called "jelly rubber." Some vendors of jelly rubber sex toys advise covering them in condoms when used internally, due to the possible health risks. Other vendors do not carry jelly rubber sex toys, in favor of phthalate-free varieties. The Dutch office of Greenpeace UK sought to encourage the European Union to ban sex toys that contained phthalates.

Health effects
Phthalates are controversial because high doses of many phthalates have shown hormonal activity in rodent studies. Studies on rodents involving large amounts of phthalates have shown damage to the liver, the kidneys, the lungs, and the developing testes. On the other hand, one Japanese study involving juvenile primates (marmosets) did not observe testicular effects (Tomonari et al, The Toxicologist, 2003). Research published in 2006 by Joint Research Centre, Institute for Health and Consumer Protection, and European Chemicals Bureau has found that two of the suspected dangerous phthalates banned by EU legislation - diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) - show no risks to human health or the environment for any current use.

2004 - a joint Swedish-Danish research team found a very strong link between allergies in children and the phthalates DEHP and BBzP.

2004 - On the other hand, a study by Children's National Medical Center and George Washington University found no adverse effects in adolescents who had been exposed to phthalates as neonates. The study measured both physical characteristics and chemical characteristics of the subjects.

2005 - study reported that phthalates may mimic the female hormone oestrogen (see xenoestrogens), and cause "feminisation" of baby boys. Phthalates and Baby Boys: Potential Disruption of Human Genital Development. Barrett JR. Environ Health Perspect. 2005 Aug; 113(8): A542.

In the study by the University of Missouri in Columbia, urine samples were collected from pregnant women in four United States cities. All were found to have levels of phthalate residues in their urine. Upon birth of the children whose mother's urine had been previously measured, the genital features and anogenital distance were measured and correlated with the residue levels in the mother's urine. In boys, the highest levels of residue were seven times more likely to have a shortened anogenital distance.

However, in a study by The George Washington University School of Medicine in Washington, D.C, it was found that adolescents exposed to significant quantities of DEHP as neonates showed no significant adverse effects on their physical growth and pubertal maturity. There was no correlation between heightened residue levels and smaller penis sizes.

The reaction of the public to the results study has been criticized by STATS, a non-profit research organization affiliated with George Mason University. Critics claim that the methodology used, including a small, homogeneous study group that was not pulled from a wide variety of regions, cannot be used to definitively claim widespread problems related to phthalates. The criticism also states that the media overstated the findings in the report.

2006 - Two of the most commonly used phthalates (DINP and DIDP) are declared "safe" at current levels of use by EU research scientists. Environmental impact, chronic and acute health effects in consumers (both adults and infants) and in chemical workers, have all been assessed and found to pose no risk. The rigorous EU risk assessments, which include a high degree of conservatism and built-in safety factors, have been carried out under the strict supervision of the European Commission and provide a clear scientific evaluation on which to judge whether a particular substance can be safely used. The research is the culmination of ten years of study into the suspect phthalates and goes against the previous conclusions and precautionary measures adopted by the EU government.

The authors of a study of Finnish boys with undescended testis hypothesized, based on their findings, that exposure to a combination of phthalates and anti-androgenic pesticides may have contributed to their condition.

2007 - a cross-sectional study of U.S. males conducted by researchers at Rochester School of Medicine and Dentistry concluded that urine concentrations of four phthalate metabolites correlate with waist size and three phthalate metabolites correlate with the cellular resistance to insulin, a precursor to Type II diabetes. The authors note the need for follow-up longitudinal studies.