30
K. Kuroda and J. Kobayashi
results showed that there was no considerable risk to human health, as the RQs of the
selected individual compounds were generally below 0.01 (Jiang et al. 2019; Sharma
et al. 2019). An exceptional case was groundwater in Patancheru, India, where very
high concentrations of antibiotics (e.g., up to 14 μg/L for ciprofloxacin), presumably
resulting from insufficiently treated industrial effluents, may induce the development
of antibiotic-resistant bacteria (Fick et al. 2009). A subsequent study of quinolone
resistance (qnr) genes in the region (Rutgersson et al. 2014) showed no apparent
correlation between the qnr genes in villager fecal samples and the fluoroquinolone
antibiotic concentration in the groundwater. Nevertheless, qnr genes were prevalent
in the fecal samples of residents from all investigated Indian villages, apparently
reflecting the broad usage of fluoroquinolone antibiotics in that country. With regard
to the ecological risk, on the other hand, compounds such as caffeine, triclocarban,
triclosan, and several antibiotics (e.g., sulfamethoxazole) can pose a medium to high
risk to sensitive species such as algae (Fick et al. 2009; Peng et al. 2014; Sharma
et al. 2019; Yao et al. 2017).
1.8 Concluding Remarks and Future Challenges
This chapter provided a comprehensive review of the occurrence, sources, and fate
of PPCPs and ASs in Asian groundwater. The review consisted of 23 studies from
six countries (China, India, Japan, Korea, Singapore, and Vietnam). The concluding
remarks and future challenges may be summarized as follows.
1. The number of studies on PPCPs and ASs in Asian groundwater has been rapidly
increasing over the last few years. Nevertheless, the number and diversity of the
studied countries remain low and have not significantly increased. For example,
the publications since 2017 are on China (4), India (2), Korea (1), and Japan
(this chapter), with Korea being the only new country represented. Moreover,
there have been no studies on Southeast Asia (except for Vietnam) or Middle
Eastern Asia. Asia consists of more than 50 countries, with great diversity in its
geographic, socio-economic, and environmental conditions. As groundwater is a
major source of drinking water in many Asian regions, more studies are needed
on the occurrence and sources of PPCPs and ASs, and on their potential risks, in
many different countries and regions.
2. The surveyed groundwater was mostly taken from shallow wells (typically <
30 mbgl). While, in many studies, shallow groundwater was most vulnerable to
pollution by PPCPs and ASs, deep groundwater was also contaminated to some
extent in a few countries, partly due to excessive pumping of deep wells (Kuroda
et al. 2012; Lapworth et al. 2012). Since hydrogeological heterogeneity is often
prominent in young Asian sedimentary aquifers, future studies could focus more
on the occurrence of PPCPs and ASs in deep aquifers in various hydrogeological
settings, which will facilitate better understanding of local hydrology and aquifer
vulnerability. Determination of suitable groundwater markers and tracers in each
K. Kuroda and J. Kobayashi
results showed that there was no considerable risk to human health, as the RQs of the
selected individual compounds were generally below 0.01 (Jiang et al. 2019; Sharma
et al. 2019). An exceptional case was groundwater in Patancheru, India, where very
high concentrations of antibiotics (e.g., up to 14 μg/L for ciprofloxacin), presumably
resulting from insufficiently treated industrial effluents, may induce the development
of antibiotic-resistant bacteria (Fick et al. 2009). A subsequent study of quinolone
resistance (qnr) genes in the region (Rutgersson et al. 2014) showed no apparent
correlation between the qnr genes in villager fecal samples and the fluoroquinolone
antibiotic concentration in the groundwater. Nevertheless, qnr genes were prevalent
in the fecal samples of residents from all investigated Indian villages, apparently
reflecting the broad usage of fluoroquinolone antibiotics in that country. With regard
to the ecological risk, on the other hand, compounds such as caffeine, triclocarban,
triclosan, and several antibiotics (e.g., sulfamethoxazole) can pose a medium to high
risk to sensitive species such as algae (Fick et al. 2009; Peng et al. 2014; Sharma
et al. 2019; Yao et al. 2017).
1.8 Concluding Remarks and Future Challenges
This chapter provided a comprehensive review of the occurrence, sources, and fate
of PPCPs and ASs in Asian groundwater. The review consisted of 23 studies from
six countries (China, India, Japan, Korea, Singapore, and Vietnam). The concluding
remarks and future challenges may be summarized as follows.
1. The number of studies on PPCPs and ASs in Asian groundwater has been rapidly
increasing over the last few years. Nevertheless, the number and diversity of the
studied countries remain low and have not significantly increased. For example,
the publications since 2017 are on China (4), India (2), Korea (1), and Japan
(this chapter), with Korea being the only new country represented. Moreover,
there have been no studies on Southeast Asia (except for Vietnam) or Middle
Eastern Asia. Asia consists of more than 50 countries, with great diversity in its
geographic, socio-economic, and environmental conditions. As groundwater is a
major source of drinking water in many Asian regions, more studies are needed
on the occurrence and sources of PPCPs and ASs, and on their potential risks, in
many different countries and regions.
2. The surveyed groundwater was mostly taken from shallow wells (typically <
30 mbgl). While, in many studies, shallow groundwater was most vulnerable to
pollution by PPCPs and ASs, deep groundwater was also contaminated to some
extent in a few countries, partly due to excessive pumping of deep wells (Kuroda
et al. 2012; Lapworth et al. 2012). Since hydrogeological heterogeneity is often
prominent in young Asian sedimentary aquifers, future studies could focus more
on the occurrence of PPCPs and ASs in deep aquifers in various hydrogeological
settings, which will facilitate better understanding of local hydrology and aquifer
vulnerability. Determination of suitable groundwater markers and tracers in each