Selected effects-directed assays in water quality monitoring

Abstract

Water in South Africa is limited and due to pollution, water of good quality is limited even more. Water is the core of existence, and for this reason it is of utmost importance to monitor and manage the freshwater quality. Chemical analyses alone are not sufficient enough to assess water quality because it will not provide the biological effect which the mixture of compounds would have on organisms exposed to water. It is also not possible to quantify every harmful compound that might be present. The present study used selected bioassays, in vitro and in vivo, to consider the value of these tools to assess water quality, including selected drinking water and environmental water samples. A small town in the Mpumalanga Province, South Africa, Wakkerstroom was the study area. It offered all types of water at one location because it was important to investigate the water quality of both drinking and environmental water. Thus water and sediment (where applicable) were collected: Potable water from a borehole and a tap in the residential area as well as bottled water sold under the Wakkerstroom brand represented the water fit for human consumption. The aquatic environment was represented by samples from rivers, dams, and various areas in the wetland which is located mostly west of the town. Samples were collected at the end of the dry season and at the end of the subsequent wet season. Water and sediment were chemically extracted with suitable methods to enrich samples for the in vitro assays. The in vivo assays were executed on the raw water and sediment and dilutions of thereof. The biological analyses measured endpoints in the MDA-kb2, H4IIE-luc, and HuTu 80 cell lines. These endpoints were: Receptor mediated activity via the aryl-hydrocarbon (AhR), androgen (AR), and glucocorticoid receptors (GR), oxidative stress biomarkers including reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), lipid peroxidation (LPO) and, non-neuronal acetylcholinesterase (AChE) activity. Viability assays were also run on the same cell lines. Commercially available in vivo assays were added when an opportunity presented itself and fairy shrimps (Thamnocephalus platyurus) and ostracods (Heterocypris incongruens) were used to evaluate water and sediment respectively for one sampling event. The biological endpoints measured were mortality and/or growth in inhibition. Biological effects mediated via the reporter gene assays were limited: xenobiotic metabolism via the AhR was seen only on two occasions. There was one instance of quantifiable androgen agonism: Wastewater treatment effluent and four events where androgen antagonism were determined. There were many statistically significant responses determined for the various oxidative stress endpoints and most biological endpoints were either increased or decreased in ROS or increased CAT. Both the cell lines used in the oxidative stress assays were equally responsive for the number of responses but not for the same samples. The AChE responses were limited and only the H4IIE-luc cells gave quantifiable results. The fairy shrimp in vivo assay indicated surprisingly high sensitivity towards the tap water which is likely due to the disinfectant by-products. The pharmaceuticals, personal care products and pesticides were chemically extracted from the water samples. The extractions were screened for the target compounds using an ultra-high-performance liquid chromatography connected to an UPLC-QTOF-MS. The chemical analyses were used to compliment the biological analyses to provide information on the chemical culprits that possibly added to the measured responses. Using biological and chemical analyses to compliment each other showed to be of importance as for some of the samples the chemical screening showed little to no results whereas the exact same samples showed responses to the biological analyses. Biological analyses deemed to be more informative on the effect the water quality would have on the environment and the organisms either living in that water using the water source for household purposes.