Some groups of brominated flame retardants are more toxic than others, and polybrominated diphenyl ethers (the PBDEs) are one of these groups. There are 209 different PBDEs and some of the most abundant PBDEs in animals are PBDE28, PBDE47, PBDE99, PBDE100, PBDE153, PBDE154 and PBDE 183.
These are the seven we analyse at NIFES, and which we refer to as total PBDE, or PBDE7. If people consume PBDEs, they accumulate in the blood and in women's breast milk.
The use of PBDEs has decreased since 2006, because, among other things, an international ban on PBDEs and octabrominated diphenyl ether (OBDE) was adopted. Hexabromocyclododecan (HBCDD) is another brominated flame retardant group that was banned in 2013.
Animal trials have shown that PBDEs interfere with animals ability to reproduce and affects brain development. HBCDDs can also have an adverse effect on fertility. Other types of brominated flame retardants that are less toxic can still be used. We know little at present about what effect these substances have on people.
We are exposed to the substances via the air and food. In seafood, these substances are found in fat fish, and there has been increased focus on PBDEs in Norway because high levels have been found in fish from lake Mjøsa, including in trout. These levels are now much lower than they were ten years ago. Brominated flame retardants are transferred from feed to the fish, and are therefore found in small quantities in farmed salmon. Neither an upper maximum level value nor a tolerable weekly intake have been stipulated for brominated flame retardants. The levels of PBDEs in farmed salmon are on the decrease.
Maximum levels in fish feed
NIFES analyses fish feed for PBDEs on an annual basis. The average level in feed shows a downward trend for PBDEs in fish feed. Since these substances accumulate in the fat of the fish, insignificant quantities are transferred to the environment as they remain in the fish. There is no maximum levles for brominated flame retardants in fish feed.