Review of brominated flame retardants and polybrominated dibenzo-p-dioxins and dibenzofurans in eggs and contamination sources

The data on the concentrations of brominated flame retardants (BFRs) and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) in eggs from free-range chickens were reviewed and compiled including assignment to major sources. The highest levels of polybrominated diphenyl ethers (PBDEs) and PBDD/Fs in pooled eggs from free-range chickens were detected at sites where e-waste was burned, near waste incineration, metallurgical facilities and at landfills/dumps. The PBDD/F pattern indicated that PBDEs and Tetrabromobisphenol A (TBBPA) are the major sources for PBDD/F contamination in the eggs. Dioxin bio-assays like the DR CALUX are useful to screen for total dioxin toxicity (PCDD/Fs, dl-PCB, PBDD/Fs and mixed polybrominated-polychlorinated dibenzo-p-dioxins/furans (PXDD/Fs)). The robust and cheap bioassay approach is currently the only method which also quantifies the dioxin-like toxicity of the complex group of PXDD/Fs where instrumental analysis cannot quantify the dioxin toxicity.

A major source of human exposure to BFRs is eggs from chickens that have pecked particles from e-waste plastics or other waste/products treated with BFRs. When chickens ingest plastic particles containing contaminants, the latter are transferred to their eggs. This is similar to what has been documented for sea birds. The BFRs listed as persistent organic pollutants (POP) with the highest level detected were PBDEs and hexabromocyclododecane (HBCDD). HBCDD is mainly contained in expanded and extruded polystyrene (EPS/XPS) which can be easily pecked by chickens. This was likely the reason for several HBCDD contaminated eggs above 1000 ng/g fat and up to 18,321 ng/g fat. EPS/XPS insulation which contain 90 % of all HBCDD formerly produced (∼640,000 tonnes in ∼42 million tonnes of EPS/XPS) is partly also used as insulation in henhouses and other parts of farms and private houses. Since chickens like to peck at and eat the soft polymer, this can be a relevant exposure source. A wide range of novel BFRs (nBFR) were detected in chicken eggs. The nBFR with the highest levels and frequency detected was 1,2-Bis(2,4,6-tribromophenoxy)ethane (BTBPE). BTBPE was often found in eggs in the monitoring of the International Pollutants Elimination Network (IPEN) with levels frequently above 10 ng/kg fat and three samples above 100 ng/g fat, up to 221 ng/g fat. DBDPE was also frequently detected in eggs with a maximum concentration of 2077 ng/g fat at the sites where plastic waste is used as fuel in boilers/incinerators. Also, hexabromobenzene (HBBz) was frequently detected in eggs above 0.1 ng/g fat with highest level of 30.3 ng HBBz/g fat.

Recommendations for controlling BFR and PBDD/F exposure of chicken and eggs are provided including the listing of PBDD/F and PXDD/F in the Stockholm Convention, the better control of plastic containing BFRs including the prohibition of exports of e-waste and plastic wastes to developing countries, better control and environmentally sound management of ashes from waste incineration or metallurgical processes, the improvement of environmentally sound management of BFR containing plastic wastes, prevention of recycling POPs containing wastes, and the substitution of BFRs.