18
K. Kuroda and J. Kobayashi
while in the urban area only acesulfame was detected, and at very low levels (max.
0.49 ng/L). The X-ray contrast media were not detected in the groundwater, despite
their abundance in the surface waters and wastewater (maximum 4000 ng/L iohexol
in WWTP effluents).
1.4 Comparison of Selected Compounds Among Studies
This section compares the detection frequencies and concentrations of three antibiotics (ciprofloxacin, sulfamethoxazole, and trimethoprim; Table 1.3), six other pharmaceuticals (acetaminophen, caffeine, carbamazepine, crotamiton, diclofenac, and
ibuprofen; Table 1.4), three ACs (acesulfame, cyclamate, and sucralose), and a personal care product, DEET (Table 1.5), in Asian groundwater. The compounds were
selected based on their frequent and abundant occurrence across the studies, in more
than two Asian countries. It should be noted that the study objectives, site selection
criteria, and sample numbers were not consistent across the studies, which would
affect the detection frequencies and concentrations, as Lapworth et al. (2012) pointed
out. Each study had specific characteristics; for example, a reconnaissance study in a
large region or across multiple cities (e.g., Kuroda et al. 2012; Sharma et al. 2019), a
catchment-scale investigation (e.g., Tran et al. 2014b; Yang et al. 2018), or a local survey in specific sites such as landfill sites (Peng et al. 2014). The site selection criteria
also varied; and generally, in studies where the sampling sites are selected without
strict criteria, the detection frequencies of the compounds are significantly lower
than in studies where the sampling sites are selected as potentially contaminated
(Lapworth et al. 2012).
1.4.1 Antibiotics
Antibiotics are used as human and animal medicine to treat diseases caused by
microorganisms such as bacteria, fungi, or protozoa (Kümmerer 2009a) and are
heavily used in Asia (Van Boeckel et al. 2014). In China, for example, 162,000 tons
of antibiotics were administered in 2013, with human use accounting for 48%, and
the remainder being veterinary antibiotics (Dong et al. 2018). The environmental
release of antibiotic residues leads to resistant bacteria (Kümmerer 2009b), and the
spread of antibiotic-resistant bacteria in the environment has become a worldwide
concern (Michael et al. 2013). It is a particularly significant challenge in Asia since
wastewater containing antibiotics is often directly discharged into the environment
without sufficient treatment (Kumar et al. 2019; Lundborg and Tamhankar 2017;
Mutiyar and Mittal 2014). The occurrence of antibiotics and their resistant genes
in the environmental matrices have been actively examined in Asia (e.g., in China
(Qiao et al. 2018) and India (Philip et al. 2018))
K. Kuroda and J. Kobayashi
while in the urban area only acesulfame was detected, and at very low levels (max.
0.49 ng/L). The X-ray contrast media were not detected in the groundwater, despite
their abundance in the surface waters and wastewater (maximum 4000 ng/L iohexol
in WWTP effluents).
1.4 Comparison of Selected Compounds Among Studies
This section compares the detection frequencies and concentrations of three antibiotics (ciprofloxacin, sulfamethoxazole, and trimethoprim; Table 1.3), six other pharmaceuticals (acetaminophen, caffeine, carbamazepine, crotamiton, diclofenac, and
ibuprofen; Table 1.4), three ACs (acesulfame, cyclamate, and sucralose), and a personal care product, DEET (Table 1.5), in Asian groundwater. The compounds were
selected based on their frequent and abundant occurrence across the studies, in more
than two Asian countries. It should be noted that the study objectives, site selection
criteria, and sample numbers were not consistent across the studies, which would
affect the detection frequencies and concentrations, as Lapworth et al. (2012) pointed
out. Each study had specific characteristics; for example, a reconnaissance study in a
large region or across multiple cities (e.g., Kuroda et al. 2012; Sharma et al. 2019), a
catchment-scale investigation (e.g., Tran et al. 2014b; Yang et al. 2018), or a local survey in specific sites such as landfill sites (Peng et al. 2014). The site selection criteria
also varied; and generally, in studies where the sampling sites are selected without
strict criteria, the detection frequencies of the compounds are significantly lower
than in studies where the sampling sites are selected as potentially contaminated
(Lapworth et al. 2012).
1.4.1 Antibiotics
Antibiotics are used as human and animal medicine to treat diseases caused by
microorganisms such as bacteria, fungi, or protozoa (Kümmerer 2009a) and are
heavily used in Asia (Van Boeckel et al. 2014). In China, for example, 162,000 tons
of antibiotics were administered in 2013, with human use accounting for 48%, and
the remainder being veterinary antibiotics (Dong et al. 2018). The environmental
release of antibiotic residues leads to resistant bacteria (Kümmerer 2009b), and the
spread of antibiotic-resistant bacteria in the environment has become a worldwide
concern (Michael et al. 2013). It is a particularly significant challenge in Asia since
wastewater containing antibiotics is often directly discharged into the environment
without sufficient treatment (Kumar et al. 2019; Lundborg and Tamhankar 2017;
Mutiyar and Mittal 2014). The occurrence of antibiotics and their resistant genes
in the environmental matrices have been actively examined in Asia (e.g., in China
(Qiao et al. 2018) and India (Philip et al. 2018))