Identification of Brominated and Chlorinated Phenols as Potential Thyroid-Disrupting Compounds in Indoor Dusts

Abstract

Our previous study demonstrated that compounds in indoor dusts strongly inhibit thyroxine (T4) binding to the human thyroid hormone transport protein transthyretin (TTR) in vitro. Exposure assessment indicated that house dust is an important medium of exposure of children to TTR-binding compounds when binding potency and dust ingestion rates are high. Here, we used chemical fractionation with in vitro competitive human TTR-binding assay and GC-MS to analyze the TTR-binding compounds in a sulfuric-acid-treated dust extract. 2,4,6-Tribromophenol (TriBPh) and 2,3,4,5,6-pentachlorophenol (PeCPh) were potent TTR-binding compounds in all dust samples. 2,4,6-TriBPh- and 2,3,4,5,6-PeCPh-derived theoretical T4 equivalents (T4EQs), calculated arithmetically from the concentrations and relative potencies, accounted for about 40-70% of experimental T4EQs detected in indoor dusts, indicating that these compounds contributed strongly to the TTR-binding potency of indoor dust. Indoor sources of 2,4,6-TriBPh might be brominated flame retardants currently used in household materials such as electrical appliances. In contrast, the 2,3,4,5,6-PeCPh might be trace evidence of past use in agricultural chemicals and preservatives in indoor or outdoor environments, because its use has been banned since 1990 in Japan. 2,4,6-TriBPh and 2,3,4,5,6-PeCPh are ubiquitous potential thyroid-disrupting compounds in the home and work environments of Japan and other countries.

ANIMAL MODELS OF DISEASE: Feline hyperthyroidism: an animal model for toxic nodular goiter

“…As PBDEs migrate out of the flame-protected materials (e.g. plastics, textiles, furniture, or electronics), these chemicals end up in house dust as the natural sink (Suzuki et al 2008). Therefore, in addition to dietary sources of PBDEs, domestic cats living indoors and lying on the floor will normally collect dust in their fur and ingest these dust-enriched chemicals through grooming (Guo et al 2012, Johnson et al 2013.…”

Emerging Brominated Flame Retardants in the Environment

“…House dust from 19 houses and 14 offices collected from Japan in 2005 were analyzed for TBP [111]. TBP was a major phenolic component with higher concentrations in offices (median 90 ng/g, range 27-620 ng/g) than in houses (median 34 ng/g, range 16-130 ng/g).…”

“…2,4,6-TBP is also produced naturally by marine algae [106][107][108] and polychaetes [109]. It may also be formed metabolically from some PBDEs [110] and is a by-product in commercial BTBPE productions [111]. Thus there are multiple sources of TBP that may explain its presence in various environmental compartments.…”

Evaluation of Toxic Activities of Polycyclic Aromatic Hydrocarbon Derivatives Using In Vitro Bioassays

“…Among toxic PAH derivatives, PAH hydroxides are androgen antagonists 8) and PAH quinones induce the generation of reactive oxygen species (ROS). 9) Furthermore, polyhalogenated aromatic hydrocarbons (PHAHs), their hydroxylated derivatives 10) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) bind to thyroid hormone transporting protein, transthyretin (TTR) 11) and reduce the T4 level in rat blood plasma. 12) But the effects of PAH and PAH derivatives on the mechanisms is unknown, in spite of their high concentrations in the atmosphere suggesting large amount of human exposure.…”