Reproductive and developmental toxicity following exposure to organophosphate ester flame retardants and plasticizers, triphenyl phosphate and isopropylated phenyl phosphate, in Sprague Dawley rats
Shannah K. Witchey, Vicki Sutherland, Brad Collins, Georgia Roberts, Keith R. Shockley, Molly Vallant, Jeff Krause, Helen Cunny, Suramya Waidyanatha, Eve Mylchreest, Barney Sparrow, Robert Moyer and Mamta Behl
DOI:
https://doi.org/10.22427/NTP-DATA-002-02974-0007-0000-1
Publication
Abstract
Two organophosphate flame retardants (OPFR), triphenyl phosphate (TPHP) and isopropylated phenyl phosphate (IPP), have been detected in environmental samples around the world. Human exposure primarily occurs via oral ingestion with reported higher concentrations in children compared to adults. Currently, there are no data to evaluate potential risk from exposure to either TPHP or IPP during fetal development. These short-term perinatal studies in rats aim to provide preliminary toxicity data for TPHP and IPP, including information on transfer to fetus/offspring and across the pup blood brain barrier. In separate experiments, TPHP or IPP were administered via dosed feed at concentrations 0, 1000, 3000, 10,000, 15,000 or 30,000 ppm to time-mated Hsd:Sprague Dawley® SD® rats from gestation day (GD) 6 through postnatal day (PND) 28; offspring were provided dosed feed at the same concentration as their dam (PND28-PND 56). TPHP and IPP-related toxicity resulted in removal of both 30,000 ppm groups on GD12 and 15,000 ppm IPP group after parturition. Body weight and organ weights were impacted with exposure in remaining dams. Reproductive performance was perturbed at ≥10,000 ppm TPHP and all IPP exposure groups. In offspring, both TPHP and IPP-related toxicity was noted in pups at ≥10,000 ppm as well as reduction in bodyweights, delays in pubertal endpoints, and/or reduced cholinesterase enzyme activity starting at 1000 ppm TPHP or IPP. Preliminary internal dose assessment indicated gestational and lactational transfer following exposure to TPHP or IPP. These findings demonstrate that offspring development is sensitive to 1000 ppm TPHP or IPP exposure.
Figures
Figure 1. Study design summary
Studies examining perinatal exposure to TPHP or IPP followed the same study design outline though conducted separately.
- Figure 1 (77 KB)
Figure 2. Mean body weight of (A) TPHP and (B) IPP exposed F0 dams during gestation and lactation
Graphs depict mean ± SEM.
- Figure 2 (93 KB)
Figure 3. Mean food consumption of (A) TPHP and (B) IPP exposed F0 dams during gestation and lactation
Graphs depict mean ± SEM.
- Figure 3 (59 KB)
Figure 4. Mean body weight (g) of male and female offspring, (TPHP (A and B) and IPP (C and D), respectively
Graphs depict mean ± SEM.
- Figure 4 (115 KB)
Figure 5. Blood AChE and BChE activity in dams and pups exposed to TPHP (A and B) or IPP (C and D)
Each point represents group mean as percent of control (control = 100%). TPHP dams n=10 (except 15000 ppm n=8), male offspring n=7-8/group and female offspring n=7-8/group. IPP dams n=9-10/group, male offspring n=10 (except 3000 ppm n=7) and female offspring n = 8-11/group.
- Figure 5 (55 KB)
Figure 6. Brain AChE and BChE activity in male and female offspring exposed to TPHP (A and B) or IPP (C and D)
Each point represents group mean as percent of control (control = 100%). TPHP dams n=10 (except 15000 ppm n=8), male offspring n=7-8/group and female offspring n=7-8/group. IPP dams n=9-10/group, male offspring n=10 (except 3000 ppm n=7) and female offspring n = 8-10/group.
- Figure 6 (51 KB)
Figure 7: Mean concentrations of TPHP (A and B) and IPP components (C and D) during gestation and lactation
Due to toxicity, no samples were collected from dams in 10,000 ppm IPP group on PND 4. TPHP and IPP GD18 and PND 4 samples n=3/group. This was a preliminary study and no statistical analysis was performed.
- Figure 7 (50 KB)
Figure 8. Concentration of TPHP (A) and IPP (B) isomers in plasma and brain of PND 28 offspring
Due to toxicity, no samples were collected for the 10,000 ppm IPP group and only 1000 IPP isomer concentrations reported. In IPP exposed animals, plasma TPHP isomer concentration fell below detection. TPHP samples n=5-6/group and IPP n=8-10/group. This was a preliminary study and no statistical analysis was performed.
- Figure 8 (34 KB)
Tables
Table 1. Structure of Compounds and Percent composition in IPP mixture
The IPP mixture is composed of TPHP and phenyl phosphate with mono-, bis- and tris- isopropyl side chains.
- Table 1 (142 KB)
Table 2. Mean TPHP and IPP reproductive performance and litter parameter
†† Significant trend at p≤0.01.
* Significantly different from control at p≤0.05;
**p≤0.01.
a. Includes 3 pregnant animals per group removed on GD 18 and PND 4 for biological sampling from 0, 1000 and 10,000 ppm dose groups for biological sampling.
b. Calculated as the number of litters divided by the number of pregnant females (excluding those taken for biological sampling)
c. Values were not available (NA) due to early termination of the groups
- Table 2 (19 KB)
Table 3. Offspring males and females balano-preputial separation and vaginal opening
a. Mean analysis, litter mean ± SE
b. No animals in the 15,000 ppm TPHP achieved BPS or VO during time of examination
c. Only one animal in 10,000 ppm TPHP achieved vaginal opening during time of examination. No statistical analysis able to be completed.
†Significant trend at p≤0.05, †† p≤0.01.
*Significantly different from control at p≤0.05;
**p≤0.01
BW=body weight; BPS=balanopreputial separation; VO=vaginal opening
- Table 3 (16 KB)