Modified One-Generation Study:

F₀ exposure began on GD 6 and was continual. At weaning on PND 28, F₁ offspring were assigned to the reproductive performance (up to 2/sex/litter, when available), prenatal (1/sex/litter), or subchronic cohort (1/sex from 10 litters). Upon sexual maturity, F₁ mating and pregnancy indices were evaluated. In the prenatal cohort, F₂ prenatal development (litter size, fetal weight, and morphology) was assessed on GD 21. In the reproductive performance cohort, littering indices, F₂ viability, and growth were assessed until PND 28. The likelihood of identifying potential EHMC-induced adverse effects (similarity and magnitude thereof) at any phase of growth or development was increased by examining related endpoints and multiple pups within a litter throughout life, across cohorts, and across generations.

EHMC did not induce overt F₀ or F₁ maternal toxicity or affect mating or pregnancy indices. Dam feed consumption and body weights were slightly lower during lactation in the 6,000 ppm group. EHMC exposure at 6,000 ppm was associated with significantly decreased F₁ and F₂ preweaning mean body weights, with an onset at approximately PND 13, consistent with the beginning of pup feed consumption. Significantly decreased F₁ preweaning mean body weights were observed in males and females exposed to 3,000 or 6,000 ppm, whereas only F₂ male and female preweaning mean body weights of the 6,000 ppm group were significantly decreased relative to their respective control groups. Although mean body weight gains of males (PND 28–105) and females (PND 28– 91) in all EHMC-exposed groups were similar to those of the respective control groups, postweaning F₁ male and female mean body weights of the 6,000 ppm group were significantly decreased by 5%–14% relative to the respective control animals. Both male and female mean body weights of the 3,000 ppm groups were significantly decreased by approximately 5% on PND 28, but by PND 56, their mean body weights were comparable to those of the control groups. Lower F₁ postweaning body weights were not associated with concurrent lower feed consumption. EHMC intake by F₀ females in the 1,000, 3,000, and 6,000 ppm EHMC groups, based on feed consumption and dietary concentrations from GD 6 through GD 21, was approximately 70, 207, and 419 mg/kg/day, respectively; from LD 1 through LD 13, EHMC intake was approximately 161, 475, and 920 mg/kg/day, respectively. EHMC intake by the F₁ generation postweaning (PND 28 through PND 91) in the 1,000, 3,000, and 6,000 ppm groups was approximately 80, 242, and 491 mg/kg/day (males) and 87, 263, and 528 mg/kg/day (females), respectively. EHMC intake by the adult F₁ females in the 1,000, 3,000, and 6,000 ppm groups was approximately 73, 220, and 435 mg/kg/day (GD 0 through GD 21) and 139, 418, and 842 mg/kg/day (LD 1 through LD 13), respectively.

EHMC exposure did not alter anogenital distance or areola/nipple retention. The timing of weaning weight-adjusted vaginal opening (VO) and balanopreputial separation (BPS) was significantly delayed by approximately 2.1 days and 2.2 days, respectively, in the 6,000 ppm group. F₁ rats exposed to 6,000 ppm EHMC displayed slightly more time in estrus.

Reproductive performance (fertility and fecundity) was not affected by EHMC exposure. The numbers of live fetuses and pups were not affected. EHMC exposure was not associated with any effects on fetal weight or the incidences of external, visceral, or skeletal malformations. The 6,000 ppm group did exhibit a higher combined fetal incidence of lumbar 1 rudimentary rib variants (approximately 10% versus 4% in the control group).

In the subchronic cohort, no gross findings, changes in organ weights, or histopathological findings were attributed to EHMC exposure.

Conclusions:

Under the conditions of this modified one-generation (MOG) study, there was no evidence of reproductive toxicity of 2-ethylhexyl p-methoxycinnamate (EHMC) in Hsd:Sprague Dawley^® SD^® rats at exposure concentrations of 1,000, 3,000, or 6,000 ppm. Mating and littering were not affected significantly by EHMC exposure.

Under the conditions of this MOG study, there was equivocal evidence of developmental toxicity of EHMC in Hsd:Sprague Dawley^® SD^® rats based on the observed postnatal effects on body weight that showed some indication of recovery by study end, delays in postnatal day 28-adjusted vaginal opening and balanopreputial separation, which could have been influenced by the apparent transient effects on body weight, and time in estrus was slightly longer in EHMC-exposed females relative to that of the control group. No other signals consistent with alterations in estrogenic, androgenic, or antiandrogenic action were observed. EHMC exposure did not induce any specific fetal malformations.