NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Di-n-Hexyl Phthalate (DnHP)

The National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR) conducted an evaluation of the potential for di-n-hexyl phthalate (DnHP) to cause adverse effects on reproduction and development in humans. DnHP 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. Available information indicates that DnHP is manufactured in relatively small amounts but occurs in a variety of commercial products including dip-molded products such as tool handles or dishwasher baskets, flooring, vinyl gloves, flea collars, and conveyer belts used in food processing. The results of this evaluation on DnHP are published in an NTP-CERHR monograph which includes: 1) the NTP Brief, 2) the Expert Panel Report on the Reproductive and Developmental Toxicity of DnHP, 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 DnHP on human development and reproduction. The scientific evidence was insufficient to reach a conclusion regarding the potential for DnHP to adversely affect human development or reproduction. There was very limited information on developmental and reproductive toxicity available to the panel. The panel evaluated only a single developmental toxicity study using a high dose (9,900 mg/kg body weight/day on gestational days 6-13) of DnHP. No live pups were delivered. In a reproductive study, effects on fertility were noted in all treatment groups (380-1,670 mg/ kg body weight/day). These studies provided sufficient information in experimental animals to conclude that DnHP is a reproductive and developmental toxicant at the doses tested. However, the treatment doses were high and these studies did not determine an exposure level at which no adverse effects occur. Human exposure information for DnHP was not available to the panel. However, the panel assumed that the US general 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. Thus, considering the inadequate quantitative information from the experimental animal studies and the inadequate human exposure data, the panel concluded there is insufficient information to reach a conclusion of the potential for DnHP to adversely affect human development or reproduction. NTP-CERHR monographs are transmitted to federal and state agencies, interested parties, and the public and are available in electronic 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).