Polybrominated Diphenyl Ethers in Human Placentas in the United States
thesisposted on 22.02.2015 by Yulin Xia
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
This thesis provides a large data set on the levels of PBDEs in human placenta in the United States under the National Children’s Study (NCS),. A total of 43 placentas were collected at University of Rochester (UR), University of California Davis (UCD), and Medical College of Wisconsin (MCW). Each placenta was sampled at different collection times up to 96 hours after the delivery, resulting in a total of 169 tissue samples. The median of the total BDEs (BDE 28+33, 47, 66, 85, 99, 100, 153, 154, 183, 209) in the 42 placentas is 330 pg/g wet wt (42.6–1723 pg/g wet wt). The total concentration of tri- to heptaBDEs is lower than that first reported by Dassanayake et al. in 2009, but the concentration of BDE 209 is 56% higher. The levels of tri- to heptaBDEs, as well as BDE 209, are significantly higher than those reported from Europe and Japan. The PBDE levels approximately follow a log-normal distribution. Among the ten congeners measured, BDE 47 is the most abundant, followed by BDEs 153, 99, 100, and 209. The congener distribution pattern is similar in placentas collected from all three collection sites. Among the three sites, the concentration of the total BDEs from UCD is statistically significantly higher than that from UR and MCW at p = 0.1 level. With regard to collection time effect, the percent change in the total BDEs is in the range of -9.0% to 15.8% up to 72 hours after the initial sample collection. Storing a placenta for 96 hours has led to more significant changes in PBDE levels. Mixed effects models with placenta chosen as a random effect to count for its uniqueness were developed in this thesis. The models demonstrate no linear relationship between the total BDEs concentration and the collection time. In addition, no interaction between collection time and location is observed. These findings along with the large data set provide opportunities to further study the association between prenatal exposure to PBDEs and health effects in children.