305
Typically precursors of PFASs are transported through the atmosphere due to
their semi-volatile to volatile properties and consequently maybe break down to
PFCAs and PFSAs [11, 22]. The precursors of PFASs (such as FASAs, FTOH,
PAPs, FASEs) undergo through various pathways of transformation in the air or
under anaerobic or aerobic conditions in other environmental compartments [10,
22]. Furthermore, other intermediate products of degradation (i.e., FTALs, FTUALs,
FTUCAs, FTCAs) produced during both biotransformation and atmospheric transformation are extremely reactive [11, 23] and have revealed toxicity of both kinds,
i.e. acute and chronic to the aquatic green algae and invertebrates [24, 25]. The
transportation processes of end products of degradation occur principally in the
water phase but can also take place through gas-phase, sea spray, and atmospheric
particle-bound transport [26–28]. For distant areas, such as Arctic Ocean, PFASs
long-range transportation was predicted to be 1–2 times higher in the water phase as
compared to atmospheric transport [29, 30]. Nevertheless, still it is under discussion
whether the water phase transport or atmospheric transport is the pathway of transportation for ionizable PFASs, Moreover, for volatile, neutral PFASs most dominant
pathway of transportation to remote areas is gas-phase transport [31]. Various environmental conditions (e.g., salinity, content of organic carbon, temperature, and
atmospheric oxidants concentrations) are responsible for the environmental cycling
of PFASs and some of their inherent physicochemical properties. Furthermore,
functional groups and PFASs chain lengths also determine their degradation. Shortchain PFASs are more mobile in the aquatic environment and hydrophilic, while
long-chain PFASs have more hydrophobicity, therefore, have the ability to bind to
particles and show the potential of bioaccumulation [32, 33]. Sediments and oceans
are the largest sources of PFASs [30].
Exposure, Bioaccumulation, and Effects
in the Aquatic Ecosystem
PFASs possess a high affinity to bind to fatty acid-binding proteins and serum albumin which consequence in a tissue-dependent supply in biota [34]. Such as tissue
distribution for PFASs in a variety of species of freshwater fishes from Beijing,
China reduced from brain to muscle and blood over the liver. Furthermore, the
potential for bioaccumulation for PFASs is different for individual species and
organisms based on the physicochemical properties of PFASs, either it has linear or
branched chain or functional group and chain length [32, 35]. It has been revealed
that the rate of elimination based upon the structure of PFASs, e.g. the rate of elimination of branched isomers is faster than linear ones. Moreover, the elimination and
bioaccumulation of PFASs are also based on the gender, species, and status of
reproduction. PFASs exist in the environment universally, even in pristine areas, and
may also be biomagnified with the food chain [36]. The most dominant PFAS in
biota is PFOS (C8 fluorocarbon), and the concentration of PFOS enhances with the
food chain, exhibiting its high potential of bioaccumulation. Distinctly, bioaccumulation potential of perfluorooctanoate (PFOA; C7fluorocarbon) is low and is quite
18 Role of Perfluoroalkyl Substances as EDCs in Metabolic Disorders
Typically precursors of PFASs are transported through the atmosphere due to
their semi-volatile to volatile properties and consequently maybe break down to
PFCAs and PFSAs [11, 22]. The precursors of PFASs (such as FASAs, FTOH,
PAPs, FASEs) undergo through various pathways of transformation in the air or
under anaerobic or aerobic conditions in other environmental compartments [10,
22]. Furthermore, other intermediate products of degradation (i.e., FTALs, FTUALs,
FTUCAs, FTCAs) produced during both biotransformation and atmospheric transformation are extremely reactive [11, 23] and have revealed toxicity of both kinds,
i.e. acute and chronic to the aquatic green algae and invertebrates [24, 25]. The
transportation processes of end products of degradation occur principally in the
water phase but can also take place through gas-phase, sea spray, and atmospheric
particle-bound transport [26–28]. For distant areas, such as Arctic Ocean, PFASs
long-range transportation was predicted to be 1–2 times higher in the water phase as
compared to atmospheric transport [29, 30]. Nevertheless, still it is under discussion
whether the water phase transport or atmospheric transport is the pathway of transportation for ionizable PFASs, Moreover, for volatile, neutral PFASs most dominant
pathway of transportation to remote areas is gas-phase transport [31]. Various environmental conditions (e.g., salinity, content of organic carbon, temperature, and
atmospheric oxidants concentrations) are responsible for the environmental cycling
of PFASs and some of their inherent physicochemical properties. Furthermore,
functional groups and PFASs chain lengths also determine their degradation. Shortchain PFASs are more mobile in the aquatic environment and hydrophilic, while
long-chain PFASs have more hydrophobicity, therefore, have the ability to bind to
particles and show the potential of bioaccumulation [32, 33]. Sediments and oceans
are the largest sources of PFASs [30].
Exposure, Bioaccumulation, and Effects
in the Aquatic Ecosystem
PFASs possess a high affinity to bind to fatty acid-binding proteins and serum albumin which consequence in a tissue-dependent supply in biota [34]. Such as tissue
distribution for PFASs in a variety of species of freshwater fishes from Beijing,
China reduced from brain to muscle and blood over the liver. Furthermore, the
potential for bioaccumulation for PFASs is different for individual species and
organisms based on the physicochemical properties of PFASs, either it has linear or
branched chain or functional group and chain length [32, 35]. It has been revealed
that the rate of elimination based upon the structure of PFASs, e.g. the rate of elimination of branched isomers is faster than linear ones. Moreover, the elimination and
bioaccumulation of PFASs are also based on the gender, species, and status of
reproduction. PFASs exist in the environment universally, even in pristine areas, and
may also be biomagnified with the food chain [36]. The most dominant PFAS in
biota is PFOS (C8 fluorocarbon), and the concentration of PFOS enhances with the
food chain, exhibiting its high potential of bioaccumulation. Distinctly, bioaccumulation potential of perfluorooctanoate (PFOA; C7fluorocarbon) is low and is quite
18 Role of Perfluoroalkyl Substances as EDCs in Metabolic Disorders