## 2 Occurrence of PFCs in Water Bodies  
PFCs are introduced into the environment during their industrial production and application, as well as a result of leaching and their biotic or abiotic biodegradation of consumer products containing a perfluoroalkyl moiety [4; 16]. Moreover, the discharge of industrial effluent containing PFCs into the environment contributes significantly to the occurrence of PFCs in both surface and ground water. Consequently, these PFCs enter waste water treatment plants (WWTPs), making them the major source of PFCs to surface waters, as reported by [PERSON] et al. [4]. Generally, WWTPs have demonstrated to be ineffective in the removal of PFCs from aqueous streams. This is attributed to the C-F bond becoming more stable with an increasing replacement of hydrogen by fluorine at each bond, consequently making PFCs able to withstand any degradation process (i.e., photolytic and microbial) [4]. Recently performed studies [10; 14; 19] have indicated that drinking water is the major exposure pathway to PFCs in communities with contaminated water. Note that the degradation of fluorotelomer alcohols and perfluoroalkyl sulfonamides lead to the formation of PFAAs, consequently resulting in their occurrence in water bodies. As such, they are classified as PFAAs precursors [4]. Moreover, the persistence of PFAAs in aquatic ecosystems is ascribed to their chemical attributes, such as simultaneous hydrophobic-hydrophilic properties and low volatility [16; 20]. In their reviews of the occurrence and fate of PFCs in drinking water, [PERSON] et al. [4] and [PERSON] et al. [14] reported that, apart from PFOA and PFOS, there are other frequently detected PFCs, such as perfluorooctane sulfonamide, perfluorohexane sulfonic acid, perfluoroobutanoic acid, perfluorohexanoic acid, perfluorohexanoic acid, and perfluoronanoate acid. Despite the occurrence of the aforementioned PFCs in aquatic ecosystems, PFOA and PFOS have been detected frequently, recording the highest concentration ranging from \(\mu\)g/L to mg/L compared to any other PFCs reported with concentration levels ranging from pg/L to ng/L. Studies [4; 21] suggest that, due to the stringent regulations on PFOA and PFOS, there are other emerging fluorinated organics, such as polyfluoroalkyl phosphates, perfluorinated phosphinic acids, and perfluorinated phosphonic acids that have been detected in water bodies. However, the aforementioned phosphorus-containing fluorinated compounds are not explicitly accounted for in this current work. It is imperative to note that the concentration levels of PFCs in water bodies can be influenced by the location of the PFC point source from the water bodies. Studies conducted on the global distribution of PFCs have shown that higher levels of PFCs, particularly PFOA and PFOS, have been detected in industrialized areas [4; 20; 22]. Consequently, PFCs have been detected in treated water at an average concentration of 30 ng/L [4]. However, there has been a large variability in PFC concentration levels from tap water, as shown in Table 1. [PERSON] et al. [23] reported PFOA and PFOS concentrations ranging from 0.6 to 6.6 ng/L and 0.1 to 11 ng/L, respectively, for background contaminated tap water. On the other hand, [PERSON] et al. [24] reported PFOA and PFOS concentration ranges of 22 to 519 ng/L and 3 to 22 ng/L, respectively, for highly industrialized, and/or agricultural areas. As a matter of health concern, the USEPA issued a limit for PFOA and PFOS in drinking water of 70 ng/L, both individually and combined [10; 25]. Based on the reported PFOA and PFOS concentration levels present in Table 1, it is apparent that PFOA and PFOS in drinking water is below the 70 ng/L limit, at least for many regions apart from Africa. The high PFOA and PFOS concentrations in drinking water from the African region suggests that drinking water can cause imminent human health risk due to PFC contamination. Due to the occurrence of PFCs in tap water, [PERSON] et al.