82
S. Mohapatra et al.
steroidal pharmaceuticals, including natural and synthetic hormones and xenoestrogens and androgens, are characterized by the presence of a phenolic ring, enabling
these molecules to have considerable solar light absorbance in the 254 nm range
(Chowdhury et al. 2011). Also, it is the presence of this phenolic moiety that causes
estrogenic activity by enabling them to bind to the estrogen receptor in cells of fishes
and other aquatic animals (Mishra et al. 2018). It is believed that the steroidal pharmaceuticals and hormones, such as 17α-ethinylestradiol (EE2) and 17β-estradiol (E2),
can undergo direct photolysis, resulting in cleavage of the phenolic ring (Chowdhury et al. 2011). This process is vital as the loss of the phenol ring can reduce the
inherent capability of the molecule to cause endocrine-disrupting effects (Li et al.
2016). However, 40–75 days were required for 50% degradation of estrone (E1),
E2, estriol (E3), and EE2 (Sornalingam et al. 2016) under direct solar irradiation.
For instance, Whidbey et al. (2012) conducted experiments under simulated solar
light for the hormones E2, EE2, E1, equilin (EQ), and equilenin (EQN) at a concentration of 10 μg/L each under direct and indirect photolysis conditions. Direct
photolysis experiments were conducted at a constant temperature, in a solar simulator, equipped with a Xe lamp and a UV filter to prevent wavelengths <300 nm.
Indirect photolysis experiments with added Suwannee River fulvic acid (10 mg/L)
led to faster degradation rates for E2, EE2, and EQ via the indirect photolytic pathway. While considerable removal of the steroids was observed through the direct
route, results of Yeast Estrogen Screen (YES) assay showed that direct photolysis of
E1 caused generation of estrogenic products, such as, Lumiestrone and others that
were not identified. On the other hand, in the presence of Suwannee River fulvic acid,
E1 underwent degradation via an indirect photolysis pathway and did not produce
Lumiestrone or any other estrogenic products. Similarly, androgenic steroidal pharmaceuticals, such as, boldenone and trenbolone have also been reported to undergo
direct photolysis, owing to their UV absorbance at 254 nm (Gryglik et al. 2010) and
testosterone, due to UV absorbance at 244 nm (Vulliet et al. 2010). Another example
is that of estriol (E3). In the presence of humic substances spiked ultrapure water,
its half-life varied between 5 and 10 h depending upon the concertation of humic
substances. Further, half-life times between 1.6 and 9.5 h were determined in surface
water samples, in which it was observed that the matrix composition contributed up
to 97% of E3 phototransformation, enabling higher efficiency of the indirect pathway in surface waters (Oliveira et al. 2016). Although steroids are susceptible to
direct photolysis, more effective removal with respect to elimination of endocrine
disruption effects (Cédat et al. 2016) and faster degradation rates (Leech et al. 2009;
Ren et al. 2017) may be achieved via the indirect pathway.
Most of the bench-scale studies showed an increase in photolysis efficiency with
variation in the type of irradiation, in the order: sunlight < UVA < UVB < UVC. For
example, 91.6% phototransformation of EE2 was achieved in 30 min under UVC
(Zhang et al. 2010). The efficiency of photolytic removal of the highly persistent EE2
was compared to its aerobic and anaerobic biodegradation in Lake Quinsigamond,
Massachusetts, USA, by Zuo et al. (2013). They reported that EE2 was present in
the lake at a concentration of ~ 11 ng/L, a concentration that is sufficient to cause
statistically significant feminization of male fishes in the lake. At this concentration,
S. Mohapatra et al.
steroidal pharmaceuticals, including natural and synthetic hormones and xenoestrogens and androgens, are characterized by the presence of a phenolic ring, enabling
these molecules to have considerable solar light absorbance in the 254 nm range
(Chowdhury et al. 2011). Also, it is the presence of this phenolic moiety that causes
estrogenic activity by enabling them to bind to the estrogen receptor in cells of fishes
and other aquatic animals (Mishra et al. 2018). It is believed that the steroidal pharmaceuticals and hormones, such as 17α-ethinylestradiol (EE2) and 17β-estradiol (E2),
can undergo direct photolysis, resulting in cleavage of the phenolic ring (Chowdhury et al. 2011). This process is vital as the loss of the phenol ring can reduce the
inherent capability of the molecule to cause endocrine-disrupting effects (Li et al.
2016). However, 40–75 days were required for 50% degradation of estrone (E1),
E2, estriol (E3), and EE2 (Sornalingam et al. 2016) under direct solar irradiation.
For instance, Whidbey et al. (2012) conducted experiments under simulated solar
light for the hormones E2, EE2, E1, equilin (EQ), and equilenin (EQN) at a concentration of 10 μg/L each under direct and indirect photolysis conditions. Direct
photolysis experiments were conducted at a constant temperature, in a solar simulator, equipped with a Xe lamp and a UV filter to prevent wavelengths <300 nm.
Indirect photolysis experiments with added Suwannee River fulvic acid (10 mg/L)
led to faster degradation rates for E2, EE2, and EQ via the indirect photolytic pathway. While considerable removal of the steroids was observed through the direct
route, results of Yeast Estrogen Screen (YES) assay showed that direct photolysis of
E1 caused generation of estrogenic products, such as, Lumiestrone and others that
were not identified. On the other hand, in the presence of Suwannee River fulvic acid,
E1 underwent degradation via an indirect photolysis pathway and did not produce
Lumiestrone or any other estrogenic products. Similarly, androgenic steroidal pharmaceuticals, such as, boldenone and trenbolone have also been reported to undergo
direct photolysis, owing to their UV absorbance at 254 nm (Gryglik et al. 2010) and
testosterone, due to UV absorbance at 244 nm (Vulliet et al. 2010). Another example
is that of estriol (E3). In the presence of humic substances spiked ultrapure water,
its half-life varied between 5 and 10 h depending upon the concertation of humic
substances. Further, half-life times between 1.6 and 9.5 h were determined in surface
water samples, in which it was observed that the matrix composition contributed up
to 97% of E3 phototransformation, enabling higher efficiency of the indirect pathway in surface waters (Oliveira et al. 2016). Although steroids are susceptible to
direct photolysis, more effective removal with respect to elimination of endocrine
disruption effects (Cédat et al. 2016) and faster degradation rates (Leech et al. 2009;
Ren et al. 2017) may be achieved via the indirect pathway.
Most of the bench-scale studies showed an increase in photolysis efficiency with
variation in the type of irradiation, in the order: sunlight < UVA < UVB < UVC. For
example, 91.6% phototransformation of EE2 was achieved in 30 min under UVC
(Zhang et al. 2010). The efficiency of photolytic removal of the highly persistent EE2
was compared to its aerobic and anaerobic biodegradation in Lake Quinsigamond,
Massachusetts, USA, by Zuo et al. (2013). They reported that EE2 was present in
the lake at a concentration of ~ 11 ng/L, a concentration that is sufficient to cause
statistically significant feminization of male fishes in the lake. At this concentration,