The role of effect-based methods to address water quality monitoring in South Africa: a developing country's struggle

The benefit of using in vitro bioassays to screen agricultural samples for oxidative stress: South Africa's case

Applied pesticides end up in non-target environments as complex mixtures. When bioavailable, these chemicals pose a threat to living organisms and can induce oxidative stress (OS). In this article, attention is paid to OS and the physiological role of the antioxidant defense system. South African and international literature was reviewed to provide extensive evidence of pesticide-induced OS in non-target organisms, in vivo and in vitro. Although in vitro approaches are used internationally, South African studies have only used in vivo methods. Considering ethical implications, the authors support the use of in vitro bioassays to screen environmental matrices for their OS potential. Since OS responses are initiated and measurable at lower cellular concentrations compared to other toxicity endpoints, in vitro OS bioassays could be used as an early warning sign for the presence of chemical mixtures in non-target environments. Areas of concern in the country could be identified and prioritized without using animal models. The authors conclude that it will be worthwhile for South Africa to include in vitro OS bioassays as part of a battery of tests to screen environmental matrices for biological effects. This will facilitate the development and implementation of biomonitoring programs to safeguard the South African environment.

The impact of pharmaceutical pollutants on daphnids - A metabolomic approach

Pharmaceuticals have been classified as emerging contaminants in the aquatic ecosystem, mainly due to their increased use and improper disposal. A significant range of pharmaceutical compounds and their metabolites have been globally detected in surface waters and pose detrimental effects to non-target organisms. Monitoring pharmaceutical water pollution relies on the analytical approaches for their detection, however, such approaches are limited by their sensitivity limit and coverage of the wide range pharmaceutical compounds. This lack of realism in risk assessment is bypassed with effect-based methods, which are complemented by chemical screening and impact modelling, and are able to provide mechanistic insight for pollution. Focusing on the freshwater ecosystem, in this study we evaluated the acute effects on daphnids for three distinct groups of pharmaceuticals; antibiotics, estrogens, and a range of commonly encountered environmentally relevant pharmaceutical pollutants. Combining several endpoints such as mortality, biochemical (enzyme activities) and holistic (metabolomics) we discovered distinct patterns in biological responses. In this study, changes in enzymes of metabolism e.g. phosphatases and lipase, as well as the detoxification enzyme, glutathione-S-transferase, were recorded following acute exposure to the selected pharmaceuticals. A targeted analysis of the hydrophilic profile of daphnids revealed mainly the up-regulation of metabolites following metformin, gabapentin, amoxicillin, trimethoprim and β-estradiol. Whereas gemfibrozil, sulfamethoxazole and oestrone exposure resulted in the down-regulation of majority of metabolites.

Molecular Responses of Daphnids to Chronic Exposures to Pharmaceuticals

Pharmaceutical compounds are among several classes of contaminants of emerging concern, such as pesticides, heavy metals and personal care products, all of which are a major concern for aquatic ecosystems. The hazards posed by the presence of pharmaceutical is one which affects both freshwater organisms and human health-via non-target effects and by the contamination of drinking water sources. The molecular and phenotypic alterations of five pharmaceuticals which are commonly present in the aquatic environment were explored in daphnids under chronic exposures. Markers of physiology such as enzyme activities were combined with metabolic perturbations to assess the impact of metformin, diclofenac, gabapentin, carbamazepine and gemfibrozil on daphnids. Enzyme activity of markers of physiology included phosphatases, lipase, peptidase, β-galactosidase, lactate dehydrogenase, glutathione-S-transferase and glutathione reductase activities. Furthermore, targeted LC-MS/MS analysis focusing on glycolysis, the pentose phosphate pathway and the TCA cycle intermediates was performed to assess metabolic alterations. Exposure to pharmaceuticals resulted in the changes in activity for several enzymes of metabolism and the detoxification enzyme glutathione-S-transferase. Metabolic perturbations on key pathways revealed distinct groups and metabolic fingerprints for the different exposures and their mixtures. Chronic exposure to pharmaceuticals at low concentrations revealed significant alterations of metabolic and physiological endpoints.