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Endocrine Disrupting Chemicals

Author: Bettina Genthe and Maronel Steyn - CSIR

( Article Type: Explanation )

Along with Rachel Carson’s book the “Silent Spring” in 1962, came the realisation of the potential danger of certain chemicals to humans and the environment. She questioned people’s faith in technological advancement by exposing the hazards of the pesticide DDT. During the past two decades, there has been global recognition of the potential effects of a number of chemicals that are used during our daily activities. In South Africa some 10 years ago, the Water Research Commission (WRC) realised that most of the health-related water research done to date was largely based on microbiological water quality. This did not reflect global trends and subsequently included chemicals known as Endocrine Disrupting Chemicals (EDCs) into their research strategy. This resulted in the formation of the South African EDC Research Programme under the leadership of the WRC in 1999. In 2002, the WRC hosted the first Global Water Research Coalition (GWRC) workshop on EDCs in South Africa. Much effort has since been put in place to determine the presence and effects of these substances in our water system. EDCs can be natural or man-made and have the potential to alter the normal functioning of the endocrine system. The endocrine system is responsible for guiding the development, growth, reproduction and behaviour of both humans and animals.

An understanding of the human bodily functions and the role of the endocrine system is necessary to fully appreciate the effect EDCs have on a living organism. The endocrine system regulates processes as diverse as blood pressure, smooth muscle contraction, fluid balance and bone metabolism. For many of the systems, the setup is ‘programmed’ during foetal development. An abnormal environment during this critical stage can therefore result in permanent mis-programming.
To complicate our ability to measure endocrine disrupting effects, it has been found that these substances have transgenerational capabilities. This implies that our exposure to these chemicals may only manifest and become apparent in our children or grandchildren. Effects may also occur from exposure of the developing embryo in utero or from exposure of the progeny after birth. The effects can also be visible in all three generations, or the effects may only manifest years later. The question is – how do we deal with this and how do we manage exposure from now on? Chemicals suspected of being endocrine disruptors are typically pesticides, fertilisers, pharmaceuticals (e.g., birth control hormones), certain personal care products (e.g., shampoo, lotions, perfumes, cosmetics, sunblock), and some industrial substances (e.g., plasticisers, fabric softeners and cooling agents). These chemicals find their way into our environment and we are in contact with them through all the major exposure routes such as the air we breathe, the water we ingest, the food we eat, and through our skin.
Effects of these substances on animals have been widely published and include documented observations that range from subtle changes in physiology and sexual behaviour of wildlife species to permanently altered sexual differentiation; marked population decline in Baltic seals; eggshell thinning and altered gonadal development in birds of prey. There is still much debate surrounding the significance of evidence and linkage of these chemicals affecting human health. One cannot control human exposure, which makes it difficult to prove. To complicate things, high confidence epidemiological studies and hard scientific evidence are mostly lacking. It is assumed that if animals are affected, EDCs must be affecting humans too. In South Africa the evidence of EDCs in our water system has been widespread. Levels of EDCs in drinking water sources, equal to those reported to cause feminisation of certain fish species, have been reported. Drinking water from both groundwater and surface water sources, and sediment samples have been tested positive for a variety of these substances. Significant levels of selected endocrine disrupting chemicals were found in fat tissue of certain fish species and oestrogenic activity found in water. The most controversial and devastating results found to date are the impaired sperm quality and uro-genital birth defects found in DDT-sprayed areas of South Africa. It is therefore clear that these substances are present in our environment and we are exposed and affected by them on a daily basis. The extent of our exposure and the potential for risk of adverse effects in humans are not clearly visible yet, but are we prepared to risk not knowing? EDCs have recently received more attention with the publication of a world first pilot study done at a nature reserve in South Africa.
This is the most comprehensive study on EDCs to date. The CSIR plays a vital role in assessing the potential risk of these substances in water to human health and is currently working on a framework to develop guidelines for South Africa. Research projects about the occurrence of EDC during wastewater treatment, drinking water treatment and in soil are in progress, while several projects for analytical method developments are ongoing. South Africa finds itself in a unique position as we are currently on the forefront of research on this topic. We should therefore strengthen this programme to ensure we stay abreast of global developments. South Africa is one of only a few countries still using DDT to manage malaria, but we are now seeing health impacts from this so, soon there will be an international debate on the trade-off’s between reduced malaria versus increased urogenital defects in children and other reproductive disorders. We need to be proud of this national achievement and develop this programme further. Despite much progress made through the South African EDC Research Programme, much more work needs to be undertaken. Epidemiological studies need to be done to establish dose-response relationships. More research should be done to also establish the effects on systems other than the reproductive function of the human body. The effects of these chemicals within the human body need to be better understood. Priority should be given to the transgenerational capability of these substances, as well as the synergistic and antagonistic effects of exposure to a cocktail of these chemicals in our environment.