Sponsor: Water Research Commission
Leader: Dr WJ Muller
Staff: Mr AK Gordon, Ms N Ketse, Mr TJ Human
Students: Ms AJ Holland
Duration: April 2007 - March 2008 and April 2007 - May 2009
Aims and Objectives
Worldwide, the subject of endocrine disruptors is receiving much attention. Similarly, in South Africa, the Water Research Commission have funded several large research projects concerning endocrine disruptors in water, but mostly the focus of this research has been on the human health implications.
The WRC have funded 2 separate endocrine disruptor research projects at the UCEWQ.
Project 1: Development of an ecosystem risk assessment model to determine the risk of endocrine disrupting con-taminants in the water environment.
Although a range of biological effects have been reported in animal populations, including effects related to estrogenic responses, androgenic and antiandrogenic responses as well as developmental and growth effects related to thyroid disruption, to date, only few cases could establish a causal link between EDCs in freshwater systems and altered endocrine activity/function in exposed fish and amphibians. Although significantly more research is needed to establish such links in aquatic ecosystems, the problem of managing EDCs in environmental waters remains.
Although advances have been made in South Africa to assess the activity of EDCs in our aquatic environment, to date most efforts focussed on establishing and validating endpoints to be used in first and second tier testing and few studies focus on population effects in aquatic ecosystems. Since the potential EDC inputs into the aquatic environment have increased dramatically with increased agricultural activity and alien plant control programmes in river catchments, urgent risk assessment tools are needed to evaluate the impact of such activities on natural ecosystems. Therefore, developments in terms of ecological risk assessment strategies need to be researched. This project therefore aims to address the following key issues, considering data and approaches from both vertebrate and invertebrate studies:
- Assess the advances made in the development of ecological-based risk assessment models in terms of endocrine disrupting compounds in freshwater ecosystems.
- Assess the use of the precautionary principle (versus weight of evidence) in ecological risk assessments, as well as associated data requirements, with particular reference to endocrine disrupting compounds.
- Recommend an appropriate ecological risk assessment model or framework for application in South Africa.
- Endocrine disruption contaminants provide an excellent example of an environmental issue that has consequences for both human and ecological health.
This research project is a collaborative research initiative with Prof Hannes van Wyk, Stellenbosch University.
Project 2: Environmental assessment in an area where ongoing DDT spraying occurs
The negotiations and the signing of the Stockholm Convention in 2001 to limit or ban the releases of Persistent Organic Pollutants (POPs), thereby protecting human health and the environment, has focussed attention on the available knowledge of the environmental chemistry and ecotoxicology of these compounds. The effects of these compounds are due to the combination of being persistent, the ability to be transported over long distances, the potential to be bioaccumulated, and their toxicity to biological systems. DDT is one such POP, and currently attracts wide attention due to its use in malaria control. DDT is a toxic substance, and can therefore also cause deleterious effects. The effects are mostly sub-lethal, and in most cases cause and effect are derived from residue levels of DDT in various matrixes. Some effects though, are difficult to link with levels, as effects may only manifest at later life stages, not obviously linked to present DDT residue levels. This project was developed to provide links and contributions to another WRC project (K5/1674), by providing data and findings useful to that project. The data can also be used in the envisaged risk assessment to be undertaken by that project.
The general aim of this project is to determine the levels and possible effects of pesticide use (e.g. of DDT, used in malaria control) on various biological indicators. To this end, the following aims have been selected:
- To determine the levels of DDT in birds associated with malaria control and reference areas.
- To determine the possible endocrine disruption effects on small mammals.
- To determine the possible endocrine disruption effects on freshwater snails.
- To determine the possible endocrine disruption effects on frogs, and to analyse some samples for DDT presence and levels.
- To determine the possible endocrine disruption effects on riverine macroinvertebrates.
The contribution of the UCEWQ research team to this project is specifically to investigate the Impacts of endocrine disrupting compounds on other aquatic macroinvertebrates, as the effects are currently largely unknown and is emerging as a significant research area internationally. In this study, a comprehensive survey of aquatic macroinvertebrates in rivers occurring in areas where DDT spraying occurs will be used to provide an indication of the environmental water quality and potential impact to overall river health. Selected macroinvertebrates will also be collected for acetylcholinesterase bioassays, which have been successfully used in other studies to assess impacts of pesticide use. The investigation of these biomonitoring tools will contribute towards the development of a comprehensive research programme to investigate the use of aquatic macroinvertebrates as monitors of ecological health effects of EDCs for South Africa.
This research project is a collaborative research initiative with Prof Henk Bouwman, North West University.
Last Modified: Fri, 14 Aug 2015 11:30:37 SAST