Sunlight-induced degradation of fluoroquinolones in wastewater effluent: Photoproducts identification and toxicity

Initial hazard screening for genotoxicity of photo-transformation products of ciprofloxacin by applying a combination of experimental and in-silico testing

Ciprofloxacin (CIP) is a broad-spectrum antibiotic found within μg/L concentration range in the aquatic environment. It is a known contributor of umuC induction in hospital wastewater samples. CIP can undergo photolysis to result in many transformation products (TPs) of mostly unknown toxicity. The aims of this study were to determine the genotoxicity of the UV mixtures and to understand the possible genotoxic role of the stable TPs. As such, CIP and its UV-irradiated mixtures were investigated in a battery of genotoxicity and cytotoxicity in vitro assays. The combination index (CI) analysis of residual CIP in the irradiated mixtures was performed for the umu assay. Further, Quantitative Structure-Activity Relationships (QSARs) predicted selected genotoxicity endpoints of the identified TPs. CIP achieved primary elimination after 128 min of irradiation but was not completely mineralized. Nine photo-TPs were identified. The irradiated mixtures were neither mutagenic in the Ames test nor genotoxic in the in vitro micronucleus (MN) test. Like CIP, the irradiated mixtures were umuC inducing. The CI analysis revealed that the irradiated mixtures and the corresponding CIP concentration in the mixtures shared similar umuC potentials. QSAR predictions suggested that the TPs may be capable of inducing chromosome aberration, MN in vivo, bacterial mutation and mammalian mutation. However, the experimental testing for a few genotoxic endpoints did not show significant genotoxic activity for the TPs present as a component of the whole mixture analysis and therefore, further genotoxic endpoints may need to be investigated to fully confirm this.

Photosensitized Degradation of 17β-estradiol and 17α-ethinylestradiol: Role of Humic Substances Fractions

Photodegradation of 17α-ethinylestradiol (EE2) and 17β-estradiol (E2) was investigated under simulated solar radiation. Photodegradation kinetics in the absence and presence of humic substances (HSs) fractions (humic acids [HAs], fulvic acids [FAs], and XAD-4), were compared. Although all three fractions were responsible for a noticeable increase on photodegradation rates, the effects were greater for FA and XAD-4. Half-life time decreased from 46 and 94 h (direct photodegradation) for EE2 and E2, respectively, to 6.4, 2.1, and 2.7 h (for EE2) and 5.7, 2.9, and 3.1 h (for E2) in the presence of HAs, FAs, and XAD-4, respectively. The XAD-4 fraction results were similar to those of FAs, which is considered the most photochemically active fraction of HSs. Studies were also conducted in organic matter-rich environmental water matrices. After 5 h, photodegradation ranged from 44 to 94% for EE2 and from 27 to 95% for E2, compared with 16% for EE2 and 6% for E2 in ultrapure water. The maximum photodegradation was obtained in an estuarine water sample, known to be rich in FAs and XAD-4 fractions and poor in HAs, showing that not only is the presence of organic matter an important factor for the photodegradation increase, as also the type of organic matter is determinant.

Molecular mechanism on two fluoroquinolones inducing oxidative stress: evidence from copper/zinc superoxide dismutase

The combination of molecular and cellular analysis suggested that the structural and functional alterations of Cu/Zn-SOD were closely associated with increased risk of oxidative stress initiated by both CPFX and ENFX.