Summary of historical terrestrial toxicity data for the brominated flame retardant tetrabromobisphenol A (TBBPA): effects on soil microorganisms, earthworms, and seedling emergence.

This article summarizes historical and recent research on the terrestrial toxicology of tetrabromobisphenol A (TBBPA). Despite its ubiquitous use and presence in the environment, little published data is available to evaluate the terrestrial ecotoxicity of TBBPA. The purposes of this paper are to enable broad access to a series of TBBPA ecotoxicity tests (nitrogen transformation, earthworm survival/reproduction, and seedling emergence/growth) that were conducted in support of regulatory risk assessments, and to summarize available research in the terrestrial toxicity of TBBPA. In these studies, no significant effect of TBBPA on nitrogen transformation was observed up to the highest concentration [1000 mg/kg dry weight (d.w.) soil]. The no-observed-effect concentrations (NOECs) for seedling emergence ranged from 20 to 5000 mg/kg d.w. Sensitivities were soybeans < corn ≈ onion ≈ tomato < ryegrass < cucumber; the most sensitive endpoints being seedling dry weight and height. The 28-day earthworm mortality NOEC was > 4840 mg/kg d.w. The most sensitive terrestrial endpoint was earthworm reproduction with a half maximal effective concentration (EC50) of 0.12 mg/kg d.w. soil. Based on this sensitive terrestrial endpoint, the EU derived a predicted no-effect concentration (PNEC) for soil of 0.012 mg/kg wet weight soil (EU 2008). We did not identify a more sensitive/lower point of departure for terrestrial toxicity endpoints in the published literature. On the basis of this PNEC, the EU concluded there was potential risk for environmental effects near TBBPA manufacturing sites, but no additional risk provided that no sewage sludge was applied to agricultural land (EU 2008).

Comparison of the recyclability of flame-retarded plastics.

Mechanical recycling of plastics from waste from electrical and electronical equipment (WEEE) is increasingly expected by regulators and demanded by original equipment manufacturers (CEMs); however, mechanical recycling is generally recognized to be the most economically costly and technically challenging method of recovering WEEE plastics. With 12% of WEEE plastics requiring the use of flame-retardants in order to ensure appropriate levels of consumer fire safety, there is a distinct need for data from comparative tests on recyclability of various flame-retarded plastics. Ten commercially available flame-retarded plastic grades commonly used in electronic equipment (eight "halogen-free" grades and two grades containing brominated flame-retardants (BFRs)) were subjected to two different recycling scenarios. A standard recycling scenario was carried out by repeatedly extruding the materials and an accelerated hydrolysis scenario was carried out to study the influence of humidity from air during use on the process. Both, virgin and recycled materials were tested for a potential formation of polybrominated dibenzodioxins/furans (PBDD/Fs), their mechanical properties were assessed and the fire safety rating was determined. Results indicate that none of the tested materials showed a potential to form the PBDD/Fs regulated by the German Chemicals Banning Ordinance. The halogen-free plastic grades showed a significant deterioration of mechanical properties after recycling, whereas those plastics containing BFRs were able to pass all test criteria, thus maintaining their original properties. With respect to the fire safety rating, none of the eight tested halogen-free plastic grades could maintain their fire safety rating after five recycling loops, whereas both BFR plastics continued to achieve their fire safety ratings. Therefore the tested BFR containing plastic materials showed superior recycling properties compared to the tested halogen-free plastic grades with respect to all investigated parameters.