Assessing in-vitro estrogenic effects of currently-used flame retardants

•Flame retardants are designed to prevent the initiation and spread of fire and increasing in use.•Increasing incidence of disorders attributed to endocrine disruption correlated to increase use of chemicals.•Estrogenicity and anti-estrogenicity of current flame retardants measured by MCF-7 flow-cytometric proliferation assay.•Majority of compounds altered oestrogen function.•Estrogenicity and anti-estrogenicity likely mediated by receptor-independent and -dependent mechanisms respectively.

Flame retardants are chemicals that are added to nearly all manufactured materials. Additionally, there has been a steady increase in diseases resulting from endocrine-disruption with an aligned increase in use of chemicals. Given the persistence, potential bioaccumulation, limited toxicological understanding, and vast use of flame retardants, there is a need to investigate potential endocrine-disruptive activity associated with these compounds in an effort for better risk assessment. We therefore used the MCF-7 flow-cytometric proliferation assay in an effort to establish potential estrogen-disrupting effects of twelve currently-used flame retardants. Triphenyl phosphate, tris(1,3-dichloro-2-propyl) phosphate, tris(butyl) phosphate, hexabromocyclododecane, and tetrabromobisphenol A showed statistically significant estrogenic activity, with hexabromocyclododecane being the most potent of the five (EC20 of 5.5 μM). Tris(2-butoxyethyl) phosphate, tris(1,3-dichloro-2-propyl) phosphate, tri(2-chloroethyl) phosphate, tris(butyl) phosphate, hexabromocyclododecane, tetrabromobisphenol A, and tris(2,3,-dibromopropyl) isocyanurate harboured anti-estrogenic activity when co-treating with 17β-estradiol, with hexabromocyclododecane showing the highest potency (IC20 of 17.6 μM). Interestingly, some compounds showed both estrogenic and anti-estrogenic effects, indicating both receptor-dependant and -independent mechanisms attributed to some of these compounds, in line with other studies. Multiple currently-used flame retardants may therefore act as xenoestrogens and anti-estrogens, or alter estrogen homeostasis, which could affect endocrine function.

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