Current Scenario of POPs
Exposure to POPs is known to cause serious health problems such as obesity, hormonal disruption, cancer, diabetes, cardiovascular diseases, and reproductive and neurological ailments, in addition to developing defects in women embryo . As per the World Flealth Organization (WHO), 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is the most toxic POP [4,13]. The US Environmental Protection Agency (EPA) describes dioxins as a major cause of cancer . Some POPs which have been recognized as of increasing concern worldwide are described here.
Polychlorinated Biphenyls (PCBs)
Polychlorinated biphenyls (PCBs) are commonly considered as the key representative of “industrial” POPs and have been produced in high volumes by the chemical and process industries . The high utility of PCBs is on account of their chemical stability. PCBs are used as coolants and insulators in transformers and capacitors, as plasticizers in paints and cements and as stabilizing additives in flexible polyvinyl chloride (PVC) coatings. Industrial POPs such as polybrominated diphenyl ethers (PBDEs) share some of the characteristics as PCBs, with respect to their sources and emissions. Although the production of PCBs peaked around the 1970s, the current annual production trends of PBDEs rival the historical peak of PCBs . PCBs are known to cause disturbances in thyroid hormone, sex steroid hormone and cortisol, resulting in behavioral and morphological changes [4,16].
Bisphenol A (BPA)
Bisphenol A (BPA) is a precursor to certain plastics such as polycarbonates and epoxy resins. BPA is used to protectively coat metal cans to prevent contamination and extend product shelf life. It is also added to many common products such as plastic eating utensils, toys, eyeglasses and office products. BPA is released into the environment, especially surface water, when these products go to landfills. It can be ingested or even absorbed through skin contact. BPA has been found to contaminate water supplies, dust and air, with the primary route of exposure being the leaching of BPA into food from incomplete polymerization of epoxy resins and polycarbonate plastic or the degradation of weak ester bonds that link BPA monomers .
Polycyclic Aromatic Hydrocarbons (PAHs)
Polycyclic aromatic hydrocarbons (PAHs) are non-polar, lipophilic organic compounds that are generally insoluble in water, thus limiting their mobility in the environment. PAHs are abundant around the globe. Two- or four-ringed PAHs volatilize to appear in the atmosphere in gaseous form . The predominant exposure of humans to PAHs occurs from burning solid fuels such as coal and biofuels for domestic requirements such as cooking and heating . Moreover, tobacco smoke is known to contribute about 90% of indoor PAH levels. The emissions from the transport sector can be a substantial outdoor source of PAHs in contributing to particulate air pollution . The concentration of PAHs in rivers and marine bodies may depend on various factors such as proximity to municipal and industrial discharge points, wind direction and distance from major urban roadways . Adverse effects of PAHs on human health include cancer, cardiovascular disorders, poor fetal growth, reduced immunity and poor neurological development.