Hexabromocyclododecane Transfer from Flame-Retarded Curtains to Attached Dust

Abstract

Dust is potentially important as a medium of exposure to low- and semi-volatile organic compounds in the indoor environment. To examine the transfer of hexabromocyclododecane (HBCD) isomers to dust on the surface of flame-retarded curtains, a series of 196-day laboratory experiments were conducted using two types of curtains and attached dusts. Concurrently, the physicochemical properties (vapor pressure, water solubility, and octanol–water partition coefficient) of the HBCD isomers were measured because knowledge of the isomer-specific values of these properties is still limited. HBCD isomers migrated from curtains to dust on a timescale of about 20–50 days. The composition of HBCD, dominated by γ-HBCD in the curtains, was dominated by α-HBCD in the post-experiment dusts, probably because of the higher vapor pressure of α-HBCD compared to γ-HBCD. The initial HBCD contents of the two curtains were comparable, but the concentrations and profiles of HBCD isomers in the post-experiment dusts differed markedly, probably because differences between the texture, surface finishing of the treated fabrics, or both affected HBCD transfer to the attached dust. We hypothesized that HBCD vapor from the curtain was sorbed onto dust surface and then gradually diffused into the interior of the dust particles, and a mechanistic model based on this hypothesis qualitatively reproduced the observed HBCD concentrations in house dust.