Evaluation of the toxicity of clozapine on the freshwater diatom Navicula sp. using the FTIR spectroscopy.

Clozapine is an often prescribed neuroactive pharmaceutical and frequently detected in the aquatic environments. However, its toxicity on low trophic level species (i.e., diatoms) and associated mechanisms are seldom reported. In this study, the toxicity of clozapine on a widely distributed freshwater diatom Navicula sp. was evaluated using the FTIR spectroscopy along with biochemical analyses. The diatoms were exposed to various concentrations of clozapine (0, 0.01, 0.05, 0.10, 0.50, 1.00, 2.00, 5.00 mg/L) for 96 h. The results revealed that clozapine reached up to 392.8 µg/g in the cell wall and 550.4 µg/g within the cells at 5.00 mg/L, suggesting that clozapine could be adsorbed extracellularly and accumulated intracellularly in diatoms. In addition, hormetic effects were displayed on the growth and photosynthetic pigments (chlorophyll a and carotenoid) of Navicula sp., with a promotive effect at concentrations less than 1.00 mg/L while an inhibited effect at concentrations over 2 mg/L. Clozapine induced oxidative stress in Navicula sp., accompanied by decreased levels of total antioxidant capacity (T-AOC) (>0.05 mg/L), in which, the activity of superoxide dismutase (SOD) (at 5.00 mg/L) was increased whereas the activity of catalase (CAT) (>0.05 mg/L) was decreased. Furthermore, FTIR spectroscopic analysis showed that exposure to clozapine resulted in accumulation of lipid peroxidation products, increased sparse ß-sheet structures, and altered DNA structures in Navicula sp. This study can facilitate the ecological risk assessment of clozapine in the aquatic ecosystems.

Transformation products of tetracyclines in three typical municipal wastewater treatment plants.

Antibiotics in the environment could undergo various processes with formation of transformation products, but little has been known about their occurrence and (eco)toxicological consequences. Here we investigated the occurrence and fate of nine transformation products of four tetracyclines (tetracycline, oxytetracycline, chlortetracycline and doxycycline) in three municipal wastewater treatment plants (WWTPs) in Guangzhou, China. The results showed the detection of all the tetracyclines and their transformation products in the WWTPs, with mean concentrations ranging from 17.8 ng/L (anhydrotetracycline) to 49.1 ng/L (oxytetracycline) in influent, 3.03 ng/L (tetracycline) to 6.94 ng/L (4-epi-chlortetracycline) in effluent, and 19.8 ng/g (isochlortetracycline) to 503 ng/g (4-epi-tertracycline) in sludge, respectively. The transformation products of tetracycline, oxytetracycline, chlortetracycline and doxycycline accounted for 73%-83%, 26%-52%, 70%-73% and 69%-74% of total concentrations, respectively. The aqueous removal rates of tetracyclines and their transformation products in the three WWTPs ranged from 18.4% (demethyl-chlortetracycline) to 93.7% (oxytetracycline). Mass balance analysis based on both aqueous and solid phase showed that their removals were mainly attributed to the sludge adsorption. Residual tetracyclines and their transformation products in the effluents would pose no obvious ecological risks to three aquatic organisms (green algae, daphnia and fish). However, 43.5% of sludge samples had high risks from these tetracyclines and transformation products, especially the compounds with poor biodegradability. The results from this study suggest that transformation products should be included in future environmental monitoring and control.

The effects of the chemotherapy drug cyclophosphamide on the structure and functioning of freshwater communities under sub-tropical conditions: A mesocosm study.

Cyclophosphamide (CP) is a chemotherapy drug which is widely used in the treatment of neoplastic diseases and have often been detected in urban and hospital wastewater, and surface waters. However, at present the effects of CP on aquatic organisms and ecosystems are poorly understood. The main objective of the present study was to assess the effect of CP on the structure and functioning of a sub-tropical freshwater ecosystem (macroinvertebrates, zooplankton and phytoplankton) at environmental relevant concentrations. CP (0, 0.5, 5 and 50 µg/L) was applied weekly to 13,600 L mesocosms over a period of four weeks followed by a one month post exposure period. CP was found to dissipate much faster than previous reported in literature and the half-dissipation times were treatment dependent, being 2.2, 21.3 and 23.6 days in the lowest, middle and highest treatments respectively. Only treatment related effects were observed on the community structure at individual samplings with zooplankton (NOECcommunity = 0.5 µg/L) responding at lower concentrations than phytoplankton (NOECcommunity = 5 µg/L) and macroinvertebrates (NOECcommunity ≥ 50 µg/L). The dissolved organic carbon concentration was consistently higher in the 2 highest treatments, indicating a potential effect on food web interactions and/or the microbial loop. At the population level, consistent adverse effects were observed for the plankton taxa Pleuroxus laevis, Dissotrocha sp. and Oscillatoria sp. at all CP concentrations (NOEC <0.5 µg/L). Additionally, at the highest CP treatments 7% of all the taxa showed a clear short-term adverse effect. Based on comparison with literature data it can be concluded that these taxa have the highest CP sensitivity ever recorded and these findings indicate a potential CP risk to aquatic ecosystems at environmental relevant concentrations.

Imidacloprid treatments induces cyanobacteria blooms in freshwater communities under sub-tropical conditions.

Imidacloprid is one of the most used neonicotinoid insecticides all over the world and is considered as a contaminant of concern due to its high toxicity potential to aquatic organisms. However, the majority of the studies that have evaluated the effects of imidacloprid on aquatic organisms were conducted under temperate conditions. In the present study, a mesocosm experiment was conducted under sub-tropical conditions to assess the effects of imidacloprid on the structure (macroinvertebrates, zooplankton and phytoplankton) and functional endpoints of an aquatic ecosystem and to compare the results with similar temperate and (sub-)tropical mesocosm studies. Imidacloprid (0, 0.03, 0.3 and 3 µg/L) was applied to 13 mesocosms weekly over a period of 4 weeks, followed by a one month recovery period. At the community level a lowest NOECcommunity of 0.03 µg/L was calculated for the zooplankton, phytoplankton and macroinvertebrate communities. The highest sensitivity to imidacloprid (NOEC < 0.03 µg/L) were observed for Gerris sp., Diaptomus sp. and Brachionus quadridentatus. Imidacloprid induced population declines of the larger zooplankton species (Diaptomus sp. and Ostracoda) resulted in increased rotifer abundances and shifted the phytoplankton community to a graze resistant gelatinous cyanobacteria dominated ecosystem. These cyanobacteria blooms occurred at all different concentrations and could pose an important public health and environmental concern. Although there are some differences in species and community sensitivity between the present and the other (sub-)topical mesocosm studies, it can be observed that all show a similar general community response to imidacloprid. Under (sub-)tropical conditions, the toxic effects of imidacloprid occur at lower concentrations than found for temperate ecosystems.

Occurrence, fate and mass loading of benzodiazepines and their transformation products in eleven wastewater treatment plants in Guangdong province, China.

Benzodiazepines (BZDs) are one of the most widely prescribed psychoactive drugs, however their persistence in the receiving environment has raised great concerns about their potential ecological risks. Here we investigated the occurrence, fate and mass loading of 17 BZDs and their 3 transformation products in 11 wastewater treatment plants (WWTPs) in Guangdong province, China. A total of 10 BZDs and 1 transformation product were found in the WWTPs influents, effluents and excess sludge, with concentrations reaching up to 44.5 ng/L (clozapine), 27.1 ng/L (oxazepam) and 62.9 ng/g (clozapine), respectively. The overall removal efficiency varied widely from negative to complete removal in these 11 WWTPs. Mass balance analysis of two representative WWTPs (WWTPA and WWTPB) with different treatment processes showed that their removals were mainly attributed to the sludge adsorption and biodegradation/biotransformation. The total usage of detected BZDs was estimated to be 185 kg/y in Guangdong province, China, while the total emission was 143 kg/y. Based on sewage epidemiology method, the total back-estimated consumption and emissions of BZDs and their transformation products in one district of Guangzhou (WWTPC service area) were 1012 mg/d/1000 people and 10.1 mg/d/1000 people, respectively. The findings from this study demonstrate the persistence of BZDs in WWTPs and also provide basis for further investigation into the potential ecological risks from this group of chemicals.