Phthalates

Phthalates 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.

Phthalates, also known as phthalate esters, are the dialkyl or alkyl aryl esters of 1,2-benzenedicarboxylic acid. The name phthalate is derived from phthalic acid + -ate. When added to plastics, they 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, about 400,000 tons (one billion pounds) of them are produced 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 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, 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.

Health effects

Phthalates are controversial because many phthalates have shown hormonal activity in animal studies. Studies on animals involving large amounts of phthalates have shown damage to the liver, the kidneys, the lungs and the developing testes. Since phthalate molecules are not chemically bound to the polymer where they are used as plastisizers, a significant migration is possible. The plastics industry insists that phthalates pose no risk to humans since people are exposed to extremely small amounts of phthalates. In September 2004, the European Union came to an agreement to ban the use of some pthalate plasticisers in children's toys: Three phthalates - DNIP, DIDP and DNOP - will be banned in any toys or other articles for children under three that can be put in the mouth. Three other pthalates were classed as toxic to reproduction - DEHP, BBP and DBP - and will be banned in all toys.

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

A 2005 study made headlines when it reported that phthalates may mimic the female hormone oestrogen, and cause "feminisation" of baby boys.

In the study by the University of Missouri in Columbia, urine samples were collected from pregnant women in four United States cities. All of the women 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. There was also a correlation between heightened residue levels and smaller penis sizes. The testes of boys with smaller penises were more likely to have testes that didn't descend properly into the scrotum.

The reaction of the public to the results study has been criticized[1] (http://www.stats.org/record.jsp?type=news&ID=503). Critics claim that the methodology used, including a small, homgenous study group that was not pulled from a wide variety of regions, can not be used to definatively claim widespread problems related to phthalates. The crticism also states that the media overstated the findings in the report.

Refernces

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• Swan, S.H. 2004. Phthalates in pregnant women and children. e.hormone 2004 conference. Oct. 27-30. New Orleans.

External links

• phthalates.org (http://www.phthalates.org/)
• Phthalates and Human Health (http://www.rppi.org/peg2.html)
• A mass spectral guide for quick identification of phthalate esters (http://www.iscpubs.com/articles/al/a9911kum.pdf) (pdf)
• The Association between Asthma and Allergic Symptoms in Children and Phthalates in House Dust: A Nested Case-Control Study (http://ehp.niehs.nih.gov/members/2004/7187/7187.html)
• 'Gender-bending' chemicals found to 'feminise' boys (http://www.newscientist.com/article.ns?id=dn7440), New Scientist, 27 May 2005.
• Ubiquitous Chemical Associated with Abnormal Human Reproductive Development (http://www.sciam.com/article.cfm?articleID=000240B8-30B1-1296-B0B183414B7F0000&ref=sciam&chanID=sa003), Scientific American, 27 May 2005.da:Ftalat

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