TABLE 6.

Studies linking exposure to polybrominated diphenyl ethers and microbiota changes.

References	Animal model	PBDE dose	Microbiota changes	Health effects
Studies in animals
Chen et al. (2018b)	Zebrafish	PBDE mixture (DE-71) (5 ng/L)	• Higher relative abundance of Firmicutes and Bacteroidetes in the gut of male fish, but a lower Firmicutes/Bacteroidetes ratio was observed. • DE-71 led to decreased Bacteroidetes in the gut of female fish with a higher Firmicutes/Bacteroidetes ratio. • Mycoplasma, Ruminiclostridium, unclassified Firmicutes sensu stricto and Fusobacterium were not detected in the gut of male and female fish.	• In males, an alteration in intestinal health was observed due to exposure to DE-71, which led to disruptions of the neural signaling, of the integrity of the epithelial barrier, inflammatory response, oxidative stress and antioxidant capacity, as well as disruptions of the detoxifying capacity. • In females, the physiological activities of the intestine remained unchanged.
Wang et al. (2018)	Mice	PBDE-47 (0, 0.002 and 0.2 mg/kg)	• Exposure resulted in decreased abundance of Bacteroidetes and Proteobacteria and in an increase of Actinobacteria at the phylum level. • Exposure resulted in increased abundance of Candidatus_Saccharimonas, Ruminococcaceae_UCG-013, Staphylococcus, Gemella, Eubacterium_nodatum_group, Corynebacterium_1 and Paenalcaligenesen and in a decrease in the abundance of Turicibacter and Anaerotruncus at the genus level.	• High fat diet-induced obesity increased as a result of the exposure to BDE-47. • Steatosis of the liver, disturbances in glucose homeostasis, metabolic dysfunction, and altered levels of gene mRNAs involved in lipid metabolism were found in mice fed high-fat diet and exposed BDE-47.
Li et al. (2017)	Male C57BL/6 mice	PBDE-47 (10–100 μmol/kg) and PBDE-99 (10–100 μmol/kg)	_	• Absence of gut microbiome increased PBDE-99-mediated upregulation of many genes involved in drug metabolism and it also affected hydroxylation of PBDEs. • Exposure to PBDE increased unconjugated bile acids in multiple bio-compartments in a gut microbiota-dependent manner.
Studies in humans
Laue et al. (2019)	Children	PBDE-47, PBDE-99, PBDE-100, PBDE-153 (environmental exposure)	• Exposure to PBDE-99 was associated with a decrease in uncultured bacteria within the Ruminococcaceae NK4A214 group and exposure to PBDE-47 led to differences in Ruminococcus 2.	_

PBDEs: Polybrominated diphenyl ethers; DE-71: PBDE mixture; PBDE-47: 2, 2′, 4, 4′-tetrabromodiphenil ether; PBDE-99: 2, 2′, 4, 4′, 5-pentabromodiphenil ether; PBDE-100: 2,2′,4,4′,6-pentabromodiphenyl ether; PBDE-153: 2,2′,4,4′,5,5′-Hexabromodiphenyl ether.