Pesticide impact on human and environmental health

This programme addresses the impact of pesticides in the environment on human and environmental health. Projects are aimed at determining the risk and impact associated with pesticides contained in all relevant compartments of the environment such as water, sediment, soil, air and biota. Chemicals of interest include the persistent organic pollutants (POPs) persistent toxic substances (PTSs) and endocrine disrupter compounds (EDCs).

• Impact on human health is investigated by monitoring for pesticide residues in breast milk. This project addresses communities living in malaria endemic areas where intensive agricultural developments occur especially in the northern parts of KwaZulu-Natal.  The recent study has established the simultaneous presence of DDT, its metabolites and selected pyrethroids residues in breast milk from study area. The DDT levels detected in breast milk were lower than previous studies, but presence and levels of four different pyrethroids, with suspected presence of carbamates have added another level of complexity. This raise a concern based on toxicant interactions, which at this stage are not well understood. DDT’s risk-set, established through decades of research is acceptable, when compared with the deadly implications of malaria, especially when no other obvious alternative is available. Furthermore, breast feeding, remains safe under prevailing conditions.

• The extent of pesticide contamination of the water environment is monitored by residue analyses of water, sediment and biota samples. Results of monitoring are used to determine the risk of development of pesticide resistance in malaria vectors. Pesticides that have been detected include organochlorines, organophosphates, pyrethroids and carbamates. Results of the project confirm that selection pressure against development of resistance exists in the study area where resistant strains of mosquitoes were found. It is thus crucial to ascertain the relative contribution of the different insecticide classes to the development of resistance. The current study is focused on the establishment of the correlation between levels of insecticide residues detected in water environment and levels of resistance to these insecticides in collected mosquito vectors. The findings are of great concern and demonstrate severe consequences involved in designing an efficient, malaria vector control programme for malaria endemic areas of South Africa.

• The studies conducted under the programme centre on the rural, malaria-endemic areas of KwaZulu-Natal, South Africa. Pesticides are used extensively by local farmers and yet there is limited understanding of the principles of pesticide application and their fate in the environment. The communities are at great risk of direct exposure during application and also from the use of contaminated food and water sources. It was found that because of the poor availability of containers for carrying and storing water in rural areas, old pesticide containers are understandably always used for this purpose. PPRI action of providing clean new plastic containers and exchange for old containers is one way of minimizing the pesticide-poisoning threat to selected rural community. The projects are focused on sustainable rural livelihoods and the stakeholders include all local authorities and the community at large. The process of technology transfer and identification of training needs are identified through frequent communication with all stakeholders. Training provided concentrated on pesticide use and safety aspects as well as the potential risk of pesticides to human health and the environment.  
  

Research conducted in the programme was published as three papers:

1. Sereda, B.L, Meinhardt H.R. (2005). Contamination of the water environment in malaria endemic areas of KwaZulu-Natal, South Africa by agricultural insecticides. Bull.Environ.Toxicol. 75:539-537

2. Sereda B.L, Meinhardt H.R. (2005). Contamination of the water environment in malaria endemic areas of KwaZulu-Natal, South Africa by DDT and its metabolites. Bull. Environ.Toxocol.75: 538-545

3. Bouwman H.,Sereda B., Meinhardt H.M.(2006). Simultaneous presence of DDT and pyrethroids residues in human breast milk from a malaria endemic areas in South Africa. Environ. Poll. XX 1-16

Programme Manager: Barbara Sereda
Roodeplaat Campus
E-mail: seredab@arc.agric.za