Is House Dust the Missing Exposure Pathway for PBDEs? An Analysis of the Urban Fate and Human Exposure to PBDEs

TLDR

PBDE body burdens in North America are up to 20 × higher than in Europe, with some individuals exhibiting 10–100 × median levels, yet the causes remain unclear. The study estimates emissions and fate of ΣPBDEs (excluding BDE‑209) in a 470 km² area of Toronto, Canada, using the Multi‑media Urban Model (MUM‑Fate). Using measured and modeled concentrations of indoor/outdoor air, soil, dust, and food, the authors estimated exposure pathways via soil, dust, dietary ingestion, and inhalation. Fate calculations show that 57–85 % of outdoor PBDE emissions originate in Toronto and are mainly removed by advection, while inadvertent dust ingestion is the dominant exposure route for toddlers to adults (and for nursing mothers to infants via milk), with dietary intake of animal and dairy products as the next major source and dust ingestion potentially increasing exposure nearly 100‑fold for high‑intake toddlers and occupational scenarios.

Abstract

Polybrominated diphenyl ether (PBDE) body burdens in North America are 20 times that of Europeans and some "high accumulation" individuals have burdens up to 1−2 orders of magnitude higher than median values, the reasons for which are not known. We estimated emissions and fate of ΣPBDEs (minus BDE-209) in a 470 km2 area of Toronto, Canada, using the Multi-media Urban Model (MUM-Fate). Using a combination of measured and modeled concentrations for indoor and outdoor air, soil, and dust plus measured concentrations in food, we estimated exposure to ΣPBDEs via soil, dust, and dietary ingestion and indoor and outdoor inhalation pathways. Fate calculations indicate that 57−85% of PBDE emissions to the outdoor environment originate from within Toronto and that the dominant removal process is advection by air to downwind locations. Inadvertent ingestion of house dust is the largest contributor to exposure of toddlers through to adults and is thus the main exposure pathway for all life stages other than the infant, including the nursing mother, who transfers PBDEs to her infant via human milk. The next major exposure pathway is dietary ingestion of animal and dairy products. Infant consumption of human milk is the largest contributor to lifetime exposure. Inadvertent ingestion of dust is the main exposure pathway for a scenario of occupational exposure in a computer recycling facility and a fish eater. Ingestion of dust can lead to almost 100-fold higher exposure than "average" for a toddler with a high dust intake rate living in a home in which PBDE concentrations are elevated.