# Chemicals from Brominated Flame Retardants: Analytical Methods, Occurrence, Transport and Risks
## 5 Risks Associated with BFRs and Associated Chemicals
### Categorization of BFRs  
Polybrominated Diphenyl Ethers (PBDEs)  
These are a class of chemicals known for their exceptional stability. They have a standard structure characterized by a brominated diphenyl ether with the chemical formula C\({}_{12}\)H(0-9)Br(1-10)O. This class includes 209 related compounds that differ based on the number and position of bromine atoms [109]. PBDEs are hydrophobic contaminants, meaning they are insoluble in water, and they possess a high log K\({}_{\text{ow}}\) value, indicating their tendency to bioaccumulate. Examples of PBDE formulations include Decabromodiphenyl ether (DecaBDE), Octabromodiphenyl ether (OctaBDE), and Pentabromodiphenyl ether (PentaBDE). The most common commercial mixture of PentaBDE consists of approximately 28% BDE-47 and BDE-99. The commercial formulations of OctaBDE typically contain between 11% and 22% BDE-197 and between 13% and 42% BDE-183. In contrast, DecaBDE mixtures are composed of more than 97% 3,3\({}^{\prime}\),4,4\({}^{\prime}\),5,5\({}^{\prime}\),6,6\({}^{\prime}\)-decabromodiphenyl ether (BDE-209) [110]. * Hexabromocyclododecane (HBCD) HBCD is a non-aromatic flame retardant extensively used in thermoplastic and styrene-based polymers. These polymers are integral in manufacturing packaging materials, pillows, construction items, automobiles, textiles, insulating boards, and electrical products [111]. Research indicates that HBCD is bioaccumulative, persistent, and hazardous, with the capability to persist in the environment for extended periods. It can disperse through various pathways, including air, plants, water, soil, animals, human skin, and even breast milk [112; 113; 114]. HBCD's toxicity is notable for its impact on developmental processes and neuroendocrine functions in organisms, making it a significant concern [110]. Numerous studies have established that HBCD acts as a hepatotoxicant, developmental neurotoxin, and endocrine disruptor in humans. * Tetrabromobisphenol (TBBPA) TBBPA decomposes into various byproducts such as bisphenol A, di- and tri-bromophenyl, and 2,4,6-tribromophenyl when exposed to UV irradiation. In contrast, PBDEs, including 3,3\({}^{\prime}\),4,4\({}^{\prime}\),5,5\({}^{\prime}\),6,6\({}^{\prime}\)-decabromodiphenyl ether (BDE-209), degrade in both organic and aqueous environments [115]. The chemical structure of TBBPA is primarily covalently bonded to polymers (approximately 90%), which reduces its potential for environmental leaching compared to other brominated flame retardants (BFRs) that act as additives [109; 111]. The International Agency for Research on Cancer (IARC) has classified TBBPA as a probable carcinogen [116]. TBBPA derivatives, especially ethers, are considered biologically active and may adversely affect human health [109]. Due to its high lipophilicity and low aqueous solubility, TBBPA tends to adsorb onto soil surfaces, increasing the risk of environmental contamination [117; 118; 119; 120; 121]. * Polybrominated Biphenyls (PBBs) PBBs are halogenated compounds in which one to ten hydrogen atoms in biphenyl are replaced with bromine atoms in various combinations. At room temperature, they typically appear as beige powders, white, or off-white substances. These compounds are used in numerous applications, including electronics, synthetic fibers, lacquers, and vehicle upholstery. PBBs are characterized by their high volatility and water insolubility, making them extremely stable and persistent in the environment [122]. In 1976, the United States banned PBBs after they were found in animal feed, leading to the exposure of millions of people through the consumption of contaminated food such as milk, meat, and eggs. The International Agency for Research on Cancer (IARC) has classified PBBs as \"possibly carcinogenic\" to humans. They were also banned in the European Union in 1984 [110]. * Novel Brominated Fire Retardants In response to legislative restrictions on traditional brominated flame retardants (BFRs) like PBDEs, novel brominated flame retardants (NBFRs) have been developed as alternatives.