Di-isononyl phthalate (DINP)

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Di-isononyl phthalate (DINP), a variable mixture of 30 or more phthalate esters, is currently the most common plasticizer used in polyvinyl chloride (PVC) toys.[i]  Historically, a different phthalate, di-ethylhexyl phthalate (DEHP), was used more extensively in toys, but in the 1980s it was found to be an animal carcinogen.  Some manufacturers began to use DINP as a substitute, though long-term toxicity studies, developmental and reproductive studies were not available until the late 1990s.

            DINP is added to PVC toys to confer flexibility and softness, and is present often in high concentrations of 20-40% by weight or more.[ii]  As with all of the phthalates, DINP is not covalently bound in the chemical matrix of the PVC, so it can and does leach out under normal circumstances of use. Leaching is increased by heat, agitation, friction and impaction, all conditions that could possibly be reproduced when a child plays with or chews on a toy.  Leaching may also increase with age and conditions of storage of the toy.  Exposure to leached DINP is primarily oral.  DINP is not acutely toxic to humans or animals.   Oral exposure to DINP has been is associated with liver and kidney damage including cancers in adult rodents, and skeletal and genito-urinary tract damage in rodent pups exposed in utero.[iii]^,[iv],[v]  There is wide-spread disagreement about the risk to children who play with toys containing DINP.  Biomonitoring studies show that children 6-19 years old have metabolites of DINP in their urine, but studies of the younger children have not been done.[vi]  Surveys of toy content show that DINP has become the preferred phthalate used in PVC toys in recent years.[vii]^{,[viii],[ix],[x],[xi],[xii]}  Advocates for the use of DINP point out: that it improves toy safety by reducing the chance of breakage and injuries from sharp edges; that it is not acutely toxic to humans; that it is toxic in animal experiments at doses that are several orders of magnitude above estimated and documented exposures in children; that it is less toxic than other well studied phthalates such as DEHP (the plasticizer used in medical devices); that the mechanism of carcinogenesis in rodents is likely not relevant in humans; and that it has been used for decades without evidence of harm to children.[xiii]  Detractors of its use argue: that some exposure estimates predict oral exposures in children above levels approved by some governments; that data from biomonitoring of young children are scant; that precise knowledge of the toxicokinetics of DINP in children is unknown; that there is uncertainty about the effects of exposure to immature humans (in contrast to rodents); that they believe there are safer and equally well tested alternatives to PVC which would obviate the need to use any phthalates; and that as a precaution it should not be used in children's toys.[xiv]  In some countries, government agencies have responded to this controversy differently.  The EU instituted a temporary ban on the use of DINP and fiver other phthalates in toys in 1999, and made it permanent in 2005.[xv]  The US CPSC has denied petitions which would include a ban on DINP use in toys, and agency scientists recently published a risk assessment concluding that DINP used in toys does not represent a health hazard to children.[xvi] In some countries, industry has voluntarily agreed to stop using phthalates in teethers, pacifiers and toys intended for children under age 3.[xvii]  An unregulated  "phthalate-free" label has appeared on toys in the marketplace, but a study by USPIRG, a watchdog organization in the US, found that 6 of 8 toys tested contained measurable phthalates despite being labeled as phthalate-free, albeit some only in very low amounts.[xviii] 

            The case of DINP use in toys illustrates the dynamic and complex issues that are considered by consumers, governments and manufacturers with regard to chemical toy safety.  These include 1) industry's move to improve safety by making chemical substitutions, 2) persistent uncertainties about toxicity despite rich toxicity database, 3) scientific and regulatory disagreements about exposure estimates based on toy chemical content, leaching studies and assumptions in exposure models, 4) the power of consumer pressure for precautionary action, and 5) difficulties with unregulated labeling.

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[i]PVC Toy Information Center.  Available at  http://www.pvc-toys.com/index.asp?page=2  Accessed 25 May 2006

[ii]Babich MA, Chen S-B,  Greene MA, Kiss CT,  Porter WK,  Smith TP, Wind ML, and Zamula WW.  Risk assessment of oral exposure to diisononyl phthalate from children’s products.  Regulatory Toxicology and Pharmacology 2004:40(2);151-167.

[iii] Butala JH, Moore MR, Cifone MA, Bankston JR and Astill B, Oncogenicity study of di(isononyl) phthalate in rats. Toxicologist 1996:30;202.

[iv] Butala JH, Moore MR, Cifone MA, Bankston JR and Astill B, Oncogenicity study of di(isononyl) phthalate in mice. Toxicologist 1997:36;173.

[v] Hellwig J, Freudenberger H, Jackh R. Differential prenatal toxicity of branched phthalate esters in rats.  Food Chem Toxicol 1997:35;501-512.

[vi]CDC.  Third National Report on Human Exposure to Environmental Chemicals. NCEH Pub. No. 05-0570.  Atlanta, Ga.  July 2005.  Phthalates,  Pg 253-284.  Available at  http://www.cdc.gov/exposurereport   Accessed 23 May 2006

[vii]Peters RJB Hazardous Chemicals in Consumer Products. TNO Netherlands Organisation for Applied Scientific Research.  September 2003

http://www.greenpeace.org/raw/content/international/press/reports/hazardous-chemicals-in-consume.pdf

[viii]Babich MA, Chen S-B,  Greene MA, Kiss CT,  Porter WK,  Smith TP, Wind ML, and Zamula WW.  Risk assessment of oral exposure to diisononyl phthalate from children’s products.  Regulatory Toxicology and Pharmacology  2004:40(2);151-167.

[ix]Peters RJB.  Chemical Additives in Consumer Products.  TNO-report R&I=A R 2005/066.  by TNO Environment and Geosciences: The Netherlands, 2005.

http://www.greenpeace.org/raw/content/international/press/reports/chemical-additives-in-consumer.pdf

[x]Cassidy A.  20^th Annual Toy Safety Survey, Trouble in Toy Land.  U.S. PIRG, Educational Fund, Washington DC,  Nov 2005  http://www.toysafety.net/2005/troubleintoyland2005.pdf

[xi] Harmon ME.  This Vinyl House; Hazardous Additives in Vinyl Consumer Products and Home Furnishings.  Greenpeace USA  May 2001.

[xii] Stringer R, Labunska I, Santillo D, Johnston P, Siddorn J, Stephenson A.  Concentrations of phthalate esters and identification of other additives in PVC children's toys.  Environ Sci & Pollut Res 2000:7;27-36.

[xiii]PVC Toys Information Center.  Available at  http://www.pvc-toys.com/index.asp?page=2   Accessed 23 May 2006

[xiv] Tickner J.  A Review of the Availability of Plastic Substitutes for Soft PVC in Toys.  Report Commissioned by Greenpeace International.  February 1999. 

[xv] Permanent ban of phthalates: Commission hails long-term safety for children’s toys.  Press release 05/07/2005.  Available at http://www.europa.eu.int/rapid/pressReleasesAction.do?reference=IP/05/838&format=HTML&aged=0&language=EN&guiLanguage=en  Accessed 23 June 2006

[xvi]Babich MA, Chen S-B,  Greene MA, Kiss CT,  Porter WK,  Smith TP, Wind ML, and Zamula WW.  Risk assessment of oral exposure to diisononyl phthalate from children’s products.  Regulatory Toxicology and Pharmacology  2004:40(2);151-167.

[xvii] Babich MA, Chen S-B,  Greene MA, Kiss CT,  Porter WK,  Smith TP, Wind ML, and Zamula WW.  Risk assessment of oral exposure to diisononyl phthalate from children’s products.  Regulatory Toxicology and Pharmacology  2004:40(2);151-167.

[xviii]Cassidy A.  20^th Annual Toy Safety Survey, Trouble in Toy Land.  U.S. PIRG, Educational Fund, Washington DC,  Nov 2005  http://www.toysafety.net/2005/troubleintoyland2005.pdf