Browsing by Author "Archer, Edward"

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    Androgen controlled secondary sexual characters in the male African clawed frog, Xenopus laevis, as potential biomarkers for endocrine disruptor contaminants (with special reference to fungicides) in aquatic systems
    (Stellenbosch : Stellenbosch University, 2014-04) Archer, Edward; van Wyk, Johannes, Hendrik; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Endocrine disrupting contaminants (EDCs) coming from households, industrial parks, wastewater (sewage) treatment and agricultural areas have been shown to pollute our freshwater systems. These contaminants may disrupt early development and reproductive systems in freshwater organisms (fish, frogs and crocodile species) as well as humans. Agricultural pesticides are shown as a large contributor to endocrine disruption activity in water catchment areas through spray drift, runoff, and/or groundwater leeching. Although South Africa is recognized as the largest consumer of agricultural pesticides in Africa, few studies have been undertaken to assess the prevalence and impact of endocrine disorders activities of pesticides in local freshwater systems. Recent studies have suggested that various agricultural pesticides, especially fungicides, might have adverse effects on the male endocrine system. There is therefore a need to test for a wider range of endocrine disrupting activities (mechanisms) in environmental waters other than conventional estrogenic (feminising) activities. Furthermore, there is a need to establish biomarkers in endemic species (bio-indicators) to show endocrine disruption in vertebrates (therefore also apply to humans). The specific objectives of the study were to: (1) describe and confirm the use of androgen-controlled breeding glands in male African clawed frogs (Xenopus laevis) as a biomarker for (anti)androgenic endocrine disruption activity (Chapter 2), (2) to investigate the premature development of breeding glands in X. laevis tadpoles (pre-metamorphic) and young froglets (post-metamorphic) (Chapter 2), (3) to investigate the disruption of male reproductive traits in adult X. laevis frogs by exposure to substances disrupting two different anti-androgenic endocrine disruption pathways (Chapter 3), (4) screen for (anti)androgenic activity of individual and binary mixtures of pesticides, which are regularly used in agricultural areas in the Western Cape Province of South Africa (Chapter 4), and (5) to test for (anti)androgenic and estrogenic endocrine disrupting activities by making use of in vitro assays as well as adult male X. laevis frogs collected from selected ponds surrounded by vineyards and fruit orchards in the Stellenbosch Winelands. The present study confirmed that male breeding glands can serve as biomarkers for (anti)androgenic endocrine disruption and that male reproductive and secondary sexual characteristics can be disrupted through two different biochemical control pathways. The study also confirmed that the expression of androgen-regulated breeding glands can be stimulated in pre-metamorphic tadpoles and immature, post-metamorphic frogs, and can thus be used for (anti)androgenic testing. The rapid testing and predictive value of an in vitro recombinant yeast screen for androgen receptor binding inhibition of selected individual or binary mixtures of pesticides was also confirmed. However, the current study showed that the predicted in vitro (anti)androgenic activity did not always correspond with in vivo (anti)androgenic biomarker outcomes. This It also confirmed that single-cell in vitro assays can be used as a first-level prediction for (anti)androgenic activities of individual or mixtures of agricultural pesticides. This study provides a better understanding for potential mixture interactions of commonly used agricultural pesticides, the hormonal control of secondary sexual characteristics in male frogs and the use of reproduction biomarkers to study long-term effects of endocrine disruptors in local water supplies.
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    Interaction of pharmaceutical & personal care products (PPCPs) and endocrine disrupting contaminants (EDCs) with microbial communities in South African wastewater treatment works and environmental waters
    (Stellenbosch : Stellenbosch University, 2018-03) Archer, Edward; Wolfaardt, Gideon M.; Van Wyk, Johannes H.; Kasprzyk-Hordern, Barbara; Stellenbosch University. Faculty of Science. Dept. of Microbiology.
    ENGLISH ABSTRACT: Global surface waters are increasingly shown to be contaminated by anthropogenic chemical pollutants which, in turn exert potential lethal- and sub-lethal toxicity risks to the aquatic environment and humans. In particular, pollutants which are able to modulate endocrine system pathways, known as endocrine disrupting contaminants (EDCs) are of an emerging global concern. Treated wastewater discharge is a major contributing source of this pollution, with the recalcitrance and passage of various contaminants through wastewater treatment posing a risk to water security. This is highlighted as a critically important global challenge which need to be further addressed, especially for developing countries that are subjected to increased demands for clean water and sanitation services due to rapid population growth and urbanisation. Furthermore, routine monitoring and refinement of analytical methodologies for risk assessment are largely limited in the country, which points to the needed to assess the harmful impact of priority micro-pollutants in surface water systems. One of the aims of the present study was to assess the presence and fate of EDCs and other emerging contaminants (ECs) within a selection of South African wastewater treatment works (WWTWs) and associated environmental waters in order to refine the monitoring tools and methodology used for risk assessment approaches. Endocrine-disrupting activities generated by in vitro steroid hormone receptor binding assays, namely the yeast (anti)estrogen screen (YES/YAES), highlighted the complexity when dealing with environmental samples containing a mixture of analytes. Even though notable reductions of estrogenicity by the WWTWs were measured, some remaining loads in effluent receiving river waters remained above risk-based trigger values, therefore potentially compromising human- and aquatic health. Estimation of the potential toxic masking by analytes with anti-estrogenic effect/activity highlighted further refinement that will be needed evaluating potential endocrine disrupting activity when applying bioassays for risk assessment. Both diurnal as well as seasonal variation in endocrine disrupting activities were recorded and discussed. Also, treated wastewater effluent served as a diluting medium to lower estrogenicity within recipient river waters at some study sites, and highlighted the contribution of alternative pollution sources that may significantly impact the quality of river systems. Although EDCs are mostly assumed to be associated with steroid hormones, in the present study I conducted scoping studies at selected WWTWs and showed the extent of regularly-used pharmaceuticals & personal care products (PPCPs) and drugs of abuse (DOA) present within wastewater and surface waters - having variable degradation profiles during wastewater treatment. In particular, ECs which were highlighted as priority micro-pollutants, such as anti-epileptics, non-steroidal anti-inflammatory drugs (NSAIDs), opioids and anti-depressants showed moderate- to negative removal during wastewater treatment, even during advanced activated sludge treatment processes. Although all of these pollutants are known to undergo biological degradation, the present study recommended further refinement of current treatment processes to improve on the removal of such persistent ECs. The need to define the environmental impact of EC breakdown-products were also discussed, as their potential health risks are largely unknown. The dissertation also showed the value of urban water profiling to report on the use and abuse of licit and illicit DOA within communities connected to sewer networks at two study sites. Several prescription and over-the-counter (OTC) medications were detected within wastewater originating from domestic sewage, in particular opioids, an anaesthetic and anti-depressant drug – all of which are reported to be abused in South Africa, although limited statistics exist. For illicit DOA, the loads of cocaine, 3,4-methylenedioxymethamphetamine (MDMA), methamphetamine, heroin and the new psychoactive substance (NPS) mephedrone confirmed their consumption within the communities connected to the WWTWs, which were enriched by including the detection of their metabolic breakdown products, as well as enantiomeric profiling of the chiral drugs. The present study encapsulated the benefit of urban water profiling to address current- and emerging global challenges for environmental- and human sustainability. Incorporation of the research outputs from the current study during refinement of risk-based approaches in South Africa may greatly improve water reclamation and management strategies to ultimately safeguard this valuable commodity for driving community- and environmental resilience.
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    Pharmaceutical and personal care products (PPCPs) as endocrine disrupting contaminants (EDCs) in South African surface waters
    (South African Water Research Commission, 2017-10) Archer, Edward; Wolfaardt, Gideon M.; Van Wyk, Johannes H.
    Globally, water resources are under constant threat of being polluted by a diverse range of man-made chemicals, and South Africa is no exception. These contaminants can have detrimental effects on both human and wildlife health. It is increasingly evident that several chemicals may modulate endocrine system pathways in vertebrate species, and these are collectively referred to as endocrine disrupting contaminants (EDCs). Although the endocrine-disrupting effect of water pollutants has been mainly linked to agricultural pesticides and industrial effluents, other pollutants such as pharmaceuticals and personal care products (PPCPs) are largely unnoticed, but also pose a potentially significant threat. Here we present for the first time in a South African context, a summarised list of PPCPs and other EDCs detected to date within South African water systems, as well as their possible endocrine-disrupting effect in-vitro and in-vivo. This review addresses other factors which should be investigated in future studies, including endocrine disruption, PPCP metabolites, environmental toxicology, and antibiotic resistance. The challenges of removing EDCs and other pollutants at South African wastewater treatment works (WWTWs) are also highlighted. The need for focused research involving both in-vitro and in-vivo studies to detect PPCPs in water systems, and to delineate adverse outcome pathways (AOPs) of priority PPCPs to aid in environmental impact assessment (EIA), are discussed.