in blood, breast milk, and fat tissues. Personnel associated with the manufacture of PBDE-containing products are exposed to highest levels of PBDEs. Bioaccumulation is of particular concern in such instances, especially for personnel in recycling and repair plants working on PBDE-containing products. People are also exposed to these chemicals in their domestic environment because of their prevalence in common household items. Studies in Canada have found significant concentrations of PBDEs in common foods such as salmon, ground beef, butter, and cheese. PBDEs have also been found at high levels in indoor dust, sewage sludge, and effluents from wastewater treatment plants. Increasing PBDE levels have been detected in the blood of marine mammals such as harbor seals. There is also growing concern that PBDEs share the environmental long life and bioaccumulation properties of polychlorinated dibenzodioxins. It is not known if PBDEs can cause cancer in people, although liver tumors developed in rats and mice that ate extremely large amounts of decaBDE throughout their lifetime. Lower-brominated PBDEs have not yet been tested for cancer in animals. The International Agency for Research on Cancer (IARC) has classified PBDE as a Group 3 carcinogen (not classifiable as to its carcinogenicity to humans) based on inadequate evidence of carcinogenicity in humans and inadequate or limited evidence in experimental animals. The EPA assigns the cancer category Group D (not classifiable as to human carcinogenicity) to mono-, di-, tri-, tetra-, penta-, hexa-, octa-, and nonaBDEs and reports “inadequate information” to classify the specific congeners 2,2’,4,4’-tetraBDE, 2,2’,4,4’,5-pentaBDE, and 2,2’,4,4’,5,5’-hexaBDE. However, EPA assigns a classification of “suggestive evidence of carcinogenic potential” for decaBDE. The Department of Health and Human Services has not classified PBDEs as carcinogens. The American Conference of Governmental Industrial Hygienists (ACGIH) has no data regarding cancer classifications for PBDEs. Case studies PBDEs have been shown to have hormone-disrupting effects, in particular, on estrogen and thyroid hormones. A 2009 animal study conducted by the US Environmental Protection Agency (EPA) demonstrates that deiodination, active transport, sulfation, and glucuronidation may be involved in disruption of thyroid homeostasis after perinatal exposure to PBDEs during critical developmental time points in utero and shortly after birth. The adverse effects on hepatic mechanism of thyroid hormone disruption during development have been shown to persist into adulthood. The EPA noted that PBDEs are particularly toxic to the developing brains of animals. Peer-reviewed studies have shown that even a single dose administered to mice during