Abstract
Humans and wildlife are vulnerable to the toxicity of semi-volatile and persistent organic pollutants such as polychlorinated biphenyls (PCBs). Neither the distribution of these pollutants nor their seasonal variation has ever been determined in the Buffalo River. Thus, the occurrence and concentration of 19 PCBs was assessed in King William’s Town (KWT), Izele (IZ), Zwelitsha (ZW), Maden (MD), Mdantsane (MSN) and Buffalo River estuary (BRE), all on the Buffalo River in the Eastern Cape Province of South Africa. Water samples were subjected to liquid-liquid extraction for PCBs, after which the compounds were separated and quantified on gas chromatography with electron capture detection. The PCBs differ in concentration from below detection limit (BDL) to 482 ng·L−1 in summer and BDL to 2 383 ng·L−1 in autumn. While the order of congeners increases during the summer from KWT > IZ > ZW > MD > MSN > BRE, the distribution in autumn followed the order BRE > IZ > ZW > KWT > MSN > MD. The total levels of PCBs at all the sites during summer were below the World Health Organization (WHO) permissible level of 500 ng·L−1 recommended for humans, but were exceeded at all the sampling sites in autumn except at MD. The evaluated risk with respect to cancer was lower than the acceptable threshold (10-6), whereas hazard quotients were slightly higher than the maximum threshold (of 1) stated by the United States Environmental Protection Agency (USEPA). The compounds are known to be toxic to humans and animals. The results appear to show that the exposure levels of the compounds were safe for humans and animals. Further studies are recommended in order to make a definitive conclusion.
Highlights
Anthropogenic activities are the major source of persistent organic pollutants (POPs)
The Buffalo River, which is approx. 126 km long has its source in the Amathole Mountains and has 4 impoundments along its course, namely, Laing, Maden, Rooikrantz and Bridle Drift dams, providing water, nutritional and other economic benefits for communities such as King Williams Town, Zwelitsha and Mdantsane townships through which it passes before draining into the Indian Ocean in East London through its estuary
The surrogate recoveries for Polychlorinated biphenyls (PCBs) in the samples were between 55% and 95% but ranged from 70% to 92% in the double-distilled water
Summary
Anthropogenic activities are the major source of persistent organic pollutants (POPs). They are resistant to photolytic, biological and chemical breakdown. They are highly toxic, characterized by long persistence in the environment, low solubility in water, and are lipophilic (Wong et al, 2005). POPs are usually volatile and are transported in the environment in low amounts through movement in water and air, besides migration with animals (Vosloo and Bouwman, 2005). They are basically classified into 3 categories: pesticides, industrial chemicals and by-products (El-Shahawi et al, 2010). PCBs are used for fluid heat exchange in electrical transformers and capacitors (Lu et al, 2015; Huang et al, 2014; El-Shahawi et al, 2010), and create hazards to human and environmental health owing to their tendency to bioaccumulate and biomagnify in food production processes (Ozcan et al, 2009; Ramos et al, 1995; Derouiche et al, 2007; Rissato et al, 2006; Salem et al, 2014; Grimm et al, 2015; Kampire et al, 2017)
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