Designing quantitative structure activity relationships to predict specific toxic endpoints for polybrominated diphenyl ethers in mammalian cells

Deriving aquatic life criteria for PBDEs in China and comparison of species sensitivity distribution with TBBPA and HBCD

Polybrominated diphenyl ethers (PBDEs) are important industrial brominated flame retardants. PBDEs have raised great concerns for their persistence, bioaccumulation, and harm to aquatic life and human health. Pentabromodiphenyl ether (PeBDE), octabromodiphenyl ether (OcBDE), and decabromodiphenyl ether (DeBDE) are three main commercial PBDEs congeners. In this study, published ecotoxicity data of these three PBDEs congeners for Chinese freshwater species were collected, and several acute and chronic toxicity tests for the three PBDEs congeners were performed. Using the derivation method for aquatic life criteria developed by the United States Environmental Protection Agency (USEPA), we determined that the criterion maximum concentration (CMC) for PeBDE, OcBDE and DeBDE for protection of freshwater organisms were 0.0492 mg/L, 0.197 mg/L and 0.239 mg/L, respectively. The criterion continuous concentration (CCC) for PeBDE, OcBDE and DeBDE were 0.0103 mg/L, 0.0224 mg/L and 0.0267 mg/L, respectively. The results provided a good reference for the derivation of PBDEs' water quality criteria and a basis for ecological risk assessment of PBDEs. In addition, the results of species sensitivity distribution comparison showed that the toxicity rank of five brominated flame retardants was TBBPA > PeBDE > OcBDE > DeBDE > HBCD.

Carcinogenic activity of pentabrominated diphenyl ether mixture (DE-71) in rats and mice

•

Pentabrominated diphenyl ether (PBDE) mixture was a multispecies carcinogen causing liver tumors in male and female rats and mice.

•

Hras or Ctnnb1 mutations characterized the PBDE-induced liver tumors.

•

PBDE-induced liver tumors increased with increasing PBDE exposure.

Pentabrominated diphenyl ether (PBDE) flame retardants have been phased out in Europe and in the United States, but these lipid soluble chemicals persist in the environment and are found human and animal tissues. PBDEs have limited genotoxic activity. However, in a 2-year cancer study of a PBDE mixture (DE-71) (0, 3, 15, or 50 mg/kg (rats); 0, 3, 30, or 100 mg/kg (mice)) there were treatment-related liver tumors in male and female Wistar Han rats [Crl:WI(Han) after in utero/postnatal/adult exposure, and in male and female B6C3F1 mice, after adult exposure. In addition, there was evidence for a treatment-related carcinogenic effect in the thyroid and pituitary gland tumor in male rats, and in the uterus (stromal polyps/stromal sarcomas) in female rats. The treatment-related liver tumors in female rats were unrelated to the AhR genotype status, and occurred in animals with wild, mutant, or heterozygous Ah receptor. The liver tumors in rats and mice had treatment-related Hras and Ctnnb mutations, respectively. The PBDE carcinogenic activity could be related to oxidative damage, disruption of hormone homeostasis, and molecular and epigenetic changes in target tissue. Further work is needed to compare the PBDE toxic effects in rodents and humans.

Modification of PBDEs (BDE-15, BDE-47, BDE-85 and BDE-126) biological toxicity, bio-concentration, persistence and atmospheric long-range transport potential based on the pharmacophore modeling assistant with the full factor experimental design

In this study, the properties of AhR binding affinity, bio-concentration factor, half-life and vapor pressure were selected as the typical indicators of biological toxicity, bio-concentration, persistence and atmospheric long-range transport potential for polybrominated diphenyl ethers (PBDEs), respectively. A three-dimensional pharmacophore modeling assistant with a full factor experimental design for each property was used to reveal the significant pharmacophore features and the substituent effects to obtain reasonable modified schemes for the selected target PBDEs. Finally, the performances of the persistent organic pollutant (POP) properties, the synthesis feasibility and the fire resistance of the modified compounds were evaluated. The most influential pharmacophore feature for all POP properties was the hydrophobic group, especially the vinyl and propyl groups. Modified compounds with two additional hydrophobic groups exhibited a better regulatory performance. The average reduction in the proportions of the four POP properties for the modified compounds (except for 3-phenyl-BDE-15) was 70.60%, 52.44%, 47.04% and 70.88%. In addition, the energy and the C-Br bond dissociation enthalpy of the four typical PBDEs were higher than those of the modified compounds (except for 3-phenyl-BDE-15), indicating the synthesis feasibility and the lower energy barrier of the modified compounds to release Br free radicals to provide fire resistance.