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which incorporate them into other products, via leaking from products during preparation, upon breakdown of foam products or by discarding products, via percolation from landfills, incineration, and reprocessing of waste products or attachment
onto the surface and interstices of dust particles [38]. Moreover, additive FRs are
more prone to contaminate the environment than their reactive counterpart [39].
Once an FR makes its appearance in the environment, it can spread via transportation in water or deposition into sediment or become airborne by settling upon pollens and dust particles to reach far sites from the manufacture unit. Accordingly,
FRs play a profound role in contamination of soil, water, air, and other ecosystems
vastly [40–42]. The brominated flame retardants are employed extensively owing to
their excellent performance, efficiency, and cost-effectiveness [43]. Hence, we will
further focus on the impact of FRs, with special focus on BFRs such as polybromodiphenyl ethers (PBDPEs) and polybrominated biphenyls (PBBPs) on endocrine
disruption and associated health issues pertaining to diabetes, obesity, oxidative
stress, and inflammatory responses.
Endocrine Disruption by FRs
According to the U.S. Environmental Protection Agency (EPA), “anendocrine disruptoris an exogenous agent that interferes with synthesis, secretion, transport,
metabolism, binding action, or elimination of natural blood-borne hormones that
are present in the body and are responsible for homeostasis, reproduction, and
developmental process” [5]. Several types of endocrine disruptors, also known as
exogenous substances, ranging from natural to synthetic origin have been identified
namely, tributyltin (TBT), diethylstilbestrol (DES), persistent organic pollutants
(POPs), bisphenol A, polybrominated diphenyl ethers (PBDPEs), polybrominated
biphenyls (PBBPs), parabens, and phytoestrogens [44]. Previous studies demonstrated that the exogenous substances discharged into the environment result in
injurious effects on human and animal health. Such harmful implications in humans
have been observed in the form of physiological disruption of the endocrine system,
which basically regulates metabolism through hormonal control to provide desired
level of energy and store it in the body as a fuel [44, 45]. Physiologically, EDCs act
by various mechanisms that may alter the hormonal and homeostasis systems. This
results in interference with nuclear/non-nuclear steroid hormone receptors, nonsteroid neurotransmitter receptors (for example, serotonin receptor, dopamine
receptor, and norepinephrine receptor), and orphan receptors. Enzymatic pathways
related to steroid synthesis and metabolism may also be disturbed by EDC’s exposure. Various other mechanisms that are important for endocrine and reproductive
systems have also witnessed disturbances by EDCs [5].
Since our environment, indoors and outdoors, is heavily polluted by industrial/
household waste and sewage, burning of litter in open places, automobile exhausts,
and many other sources, the exposure of humans and animals to environmental pollutants is inevitable. Increasing understanding of endocrinology and perturbation in
T. Hussain et al.
which incorporate them into other products, via leaking from products during preparation, upon breakdown of foam products or by discarding products, via percolation from landfills, incineration, and reprocessing of waste products or attachment
onto the surface and interstices of dust particles [38]. Moreover, additive FRs are
more prone to contaminate the environment than their reactive counterpart [39].
Once an FR makes its appearance in the environment, it can spread via transportation in water or deposition into sediment or become airborne by settling upon pollens and dust particles to reach far sites from the manufacture unit. Accordingly,
FRs play a profound role in contamination of soil, water, air, and other ecosystems
vastly [40–42]. The brominated flame retardants are employed extensively owing to
their excellent performance, efficiency, and cost-effectiveness [43]. Hence, we will
further focus on the impact of FRs, with special focus on BFRs such as polybromodiphenyl ethers (PBDPEs) and polybrominated biphenyls (PBBPs) on endocrine
disruption and associated health issues pertaining to diabetes, obesity, oxidative
stress, and inflammatory responses.
Endocrine Disruption by FRs
According to the U.S. Environmental Protection Agency (EPA), “anendocrine disruptoris an exogenous agent that interferes with synthesis, secretion, transport,
metabolism, binding action, or elimination of natural blood-borne hormones that
are present in the body and are responsible for homeostasis, reproduction, and
developmental process” [5]. Several types of endocrine disruptors, also known as
exogenous substances, ranging from natural to synthetic origin have been identified
namely, tributyltin (TBT), diethylstilbestrol (DES), persistent organic pollutants
(POPs), bisphenol A, polybrominated diphenyl ethers (PBDPEs), polybrominated
biphenyls (PBBPs), parabens, and phytoestrogens [44]. Previous studies demonstrated that the exogenous substances discharged into the environment result in
injurious effects on human and animal health. Such harmful implications in humans
have been observed in the form of physiological disruption of the endocrine system,
which basically regulates metabolism through hormonal control to provide desired
level of energy and store it in the body as a fuel [44, 45]. Physiologically, EDCs act
by various mechanisms that may alter the hormonal and homeostasis systems. This
results in interference with nuclear/non-nuclear steroid hormone receptors, nonsteroid neurotransmitter receptors (for example, serotonin receptor, dopamine
receptor, and norepinephrine receptor), and orphan receptors. Enzymatic pathways
related to steroid synthesis and metabolism may also be disturbed by EDC’s exposure. Various other mechanisms that are important for endocrine and reproductive
systems have also witnessed disturbances by EDCs [5].
Since our environment, indoors and outdoors, is heavily polluted by industrial/
household waste and sewage, burning of litter in open places, automobile exhausts,
and many other sources, the exposure of humans and animals to environmental pollutants is inevitable. Increasing understanding of endocrinology and perturbation in
T. Hussain et al.