NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Di-isononyl Phthalate (DINP).
The National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR) conducted an evaluation of the potential for di-isononyl phthalate (DINP) to cause adverse effects on reproduction and development in humans. DINP is one of 7 phthalate chemicals evaluated by the NTP CERHR Phthalates Expert Panel. These phthalates were selected for evaluation because of high production volume, extent of human exposures, use in children's products, and/or published evidence of reproductive or developmental toxicity. DINP is a mixture of branched, C-9 phthalate isomers used to add flexibility to a wide variety of plastic products such as toys, garden hoses, flooring tiles, tarps, and pool liners. The results of this evaluation on DINP are published in a NTP-CERHR monograph which includes: 1) the NTP Brief, 2) the Expert Panel Report on the Reproductive and Developmental Toxicity of Di-isononyl Phthalate, and 3) public comments received on the Expert Panel Report. As stated in the NTP Brief, the NTP reached the following conclusions regarding the possible effects of exposure to DINP on human development and reproduction. First, although DINP could possibly affect human development if exposures are sufficiently high, there is minimal concern for DINP causing adverse effects to human reproduction or fetal development. There is no direct evidence that exposure of people to DINP adversely affects reproduction or development, but studies show that oral exposure of pregnant rats to high doses (500 and 1000 mg/kg bodyweight/day) of DINP can adversely affect fetal development. Effects on pup growth were noted in a 2-generation reproductive toxicity study in rats at doses of 143-285 mg/kg body weight/day. Human exposure information for DINP was not available but it was assumed that the general US population would be exposed to 3-30 mug/kg body weight/day, based upon the range of estimated exposures for DEHP, a more widely used phthalate. Second, based on estimates of exposure of children to DINP from mouthing toys and other objects, the NTP has minimal concern for developmental effects in children. After the expert panel meeting, a US Consumer Products Safety Commission panel estimated that the majority of children exposed to DINP had a "minimum to non-existent risk of injury" from mouthing toys. Children's exposure was estimated at 70-280 mug/kg body weight/day, a level 1000-fold lower than exposures resulting in developmental effects in rats. NTP-CERHR monographs are transmitted to federal and state agencies, interested parties, and the public and are available electronically in PDF format on the CERHR web site (http://cerhr.niehs.nih.gov) and in printed text or CD-ROM from the CERHR (National Institute of Environmental Health Sciences, P.O. Box 12233, MD EC-32, Research Triangle Park, NC; fax: 919-316-4511).