The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings may not have been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by NTP in March 2009. For more information, see the Explanation of Levels of Evidence for Developmental Toxicity. The findings and conclusions for this study should not be construed to represent the views of NTP or the U.S. Government.
Diethylhexyl Phthalate, a widely used plasticizing agent, was evaluated for teratogenicity following maternal exposure. Timed-pregnant CD-1 mice were exposed to DEHP in the feed on gestational days 0 through 17 at levels of 0.15% (1500 ppm), 0.10% (1000 ppm), 0.05% (500 ppm), 0.025% (250 ppm) or 0.0% (0 ppm). These dose groups are referred to as DEHP-0.15, DEHP-0.10, DEHP-0.05, DEHP-0.025 or DEHP-0.0, respectively. Dams were weighed on gestational days 0, 4, 8, 12, 16 and 17 (immediately following sacrifice), and were observed for clinical signs of toxicity. Food and water were also measured on these days. At sacrifice on gestational day 17, maternal blood was taken for subsequent plasma zinc analysis, and dams were evaluated for body weight, liver weight, gravid uterine weight and status of uterine implantation sites (i.e., resorptions, dead fetuses, live fetuses). Live fetuses were dissected from the uterus, fetal blood was collected for subsequent plasma zinc analysis and fetuses were evaluated for live litter size, body weights, sex ratios and gross morphological abnormalities. All live fetuses were examined for visceral malformations employing the Staples' fresh tissue dissection method (Staples, 1974). Half of the fetuses were decapitated prior to dissection and the heads were fixed in Bouin's solution for freehand sectioning and examination (Wilson's Technique). All fetal carcasses were cleared and stained with Alizarin Red S and examined for skeletal malformations.
There was no maternal mortality in any dose group in this study. There was a significant dose-response trend toward reduced maternal body weight on gestational days 12, 16, and 17 but not gestational days 0 (prior to onset of exposure), 4 or 8, with the values from DEHP-0.10 and DEHP-0.15 dose groups significantly lower than in controls for gd 12, 16 and 17 weights. Maternal weight gain during gestation or treatment, was significant for trend with the values from the DEHP-0.10, and DEHP-0.15 dose groups lower than in controls. Gravid uterine weight exhibited a dose-related decrease with the values from DEHP-0.10 and DEHP-0.15 dose groups significantly lower than in controls. Maternal relative liver weight exhibited a dose-related increase with values for the DEHP-0.10 and DEHP-0.15 dose groups higher than for controls. Clinical signs of toxicity, which included piloerection, lethargy, and rough coat were seen in all DEHP dose groups in a dose-related manner. There were no dose-related differences observed in the number of corpora lutea or implantation sites per dam, nor in the percent preimplantation loss. The number and percent of resorptions, dead, nonlive (dead plus resorbed), and affected (nonlive plus malformed) per litter were all increased in a dose-dependent manner with the values for the DEHP-0.10 and DEHP-0.15 dose groups significantly higher than for controls for all of these parameters. Number of live fetuses and number of males or females per litter exhibited a dose-related decrease with the value for DEHP-0.10 and DEPH-0.15 groups significantly lower than in controls for total fetuses and females. For males per litter, only the DEHP-0.15 dose group value was reduced relative to controls. There were dose- related decreases in body weight for male and female fetuses combined and separately per litter; values for these three parameters were significantly reduced in the DEHP-0.15 dose group relative to controls. Female fetal body weight per litter was also reduced in the DEHP-0.10 group relative to controls. There were significant dose-related increases in the number and percentage of fetuses malformed per litter, and in the number or percentage of male or female fetuses malformed per litter. Plasma zinc analysis indicated no apparent differences between DEHP-exposed dams and fetuses and controls.
In conclusion, diethylhexyl phthalate in the feed was teratogenic to CD-1 mice exposed during the entire gestation period (gestational days 0 through 17), at dose levels which produced significant maternal and other fetal toxicity, i.e., 0.10% and 0.15%, and at a dose level which produced no significant maternal or other fetal toxicity (0.05% DEHP). Major malformations observed included external, visceral and skeletal defects. The no observable effect level for DEHP in this study was 0.025%, where there was no significant maternal or fetal toxicity, including teratogenicity.