*Flame Retardants: New and Old Environmental Contaminants DOI: http://dx.doi.org/10.5772/intechopen.104886*

**Table 2.**

 *Chemical structure and physicochemical properties of novel brominated flame retardants.*

DBDPE does not show acute toxicity in rats or rabbits: the median lethal dose (LD50) is greater than 5000 and 2000 mg/kg of bw, respectively [69]. However, subchronic and chronic exposure of mice and rats to DBDPE disrupt the endocrine system and alter thyroid hormone homeostasis, respectively [73, 74].

Ecotoxicological studies on aquatic organisms have shown acute DBDPE toxicity to water flea: 48 h EC50 is 19 μg/l. Besides that, zebrafish (*Danio rerio*) exposure to 12.5 and 25 μg/l DBDPE raises hatched larva mortality and reduces the zebrafish egg hatching rate [69]. Assessment of acute TBB and TBPH genotoxicity in fathead minnow revealed DNA damage in liver cells after oral exposure [75]. Exposure to TBB also increases zebrafish embryo mortality and malformation (LC50 = 7.0 mg/l). Zebrafish exposure to 20 mg/l TBPH (highest tested dose) has no adverse effects. **Table 3** summarizes the environmental occurrence and biological effects of the main classes of brominated flame retardants.

NBFRs used as an alternative to banned BFRs have frequently been detected in countless environmental compartments, with evidence of persistence under natural conditions—their physicochemical properties resemble the properties of banned BFRs. However, evidence of NBFR toxicity is lacking, and there is no legislation about them. Nevertheless, their in vitro and in vivo ecotoxicity to diverse organisms has been verified [22, 60, 62]. Therefore, finding new compounds that act as FRs and which are safer than older FRs like BFRs to human and environmental health is essential. Phosphorus-based flame retardants (PBFRs), which have already been used for over 150 years, could be suitable alternatives for BFRs [6].
