Environment & Health Research Unit

Levels of persistent toxic substances in South African delivering women and newborns

Human exposure to persistent toxic substances (PTS) in the living environment, which include toxic metals and persistent organic pollutants, can be from natural sources, current or past industrial activities and anthropogenic activities.

PTS have the ability to exert negative health effects that are often subtle, long-term, sometimes trans-generational and difficult to measure, even in large epidemiological studies. The most vulnerable periods for toxic impact of pollutants on human development are the embryonic and foetal stages, followed by early childhood. Most PTSs are known to affect reproductive health and pregnancy outcomes; reduce disease defense mechanisms, impact on children’s physical and mental development; and increase the risk of cancer. In addition, some of these substances are transmitted from the pregnant mother to the foetus via the umbilical cord and from mother to newborns during breastfeeding.

Several multidisciplinary international projects are currently investigating, firstly, the sources and levels of PTS in people residing in different geographical areas and secondly, ascertaining the relationship between the levels of these compounds and health.

The Arctic Monitoring and Assessment Programme (AMAP) was initiated in 1991 in eight arctic countries (Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden and the United States of America) bordering the circumpolar north. The study has produced comprehensive data on the presence of multiple contaminants in all ecosystem compartments, including humans. It also studied associated health effects in indigenous and other populations living in the Arctic and other areas of the northern hemisphere, and initiated studies of health effects and birth outcomes. Of particular concern is the accumulation of toxins in the food chain in areas where regional indigenous populations reside; these populations rely mainly on traditional and locally produced foods.

At present no comprehensive data exist on the levels of contaminants in ecosystems and humans in the southern hemisphere. South Africa, the southernmost part of Africa in the southern hemisphere, a developed as well as a developing country, is of particular importance to global research in the science of environmental pollutants and human health outcomes.

South Africa and other developing countries are experiencing a rise in informal mining (especially artisanal gold mining) and other fluctuating informal industrial activities that often take place within the living environments of communities. Furthermore, increased population migration and rapid urbanization, with its wide range of anthropogenic activities, may further contribute to environmental degradation and pollution. A high prevalence of infectious diseases (lung diseases, TB, HIV/AIDS) and endemic malaria in parts of the country make South Africa and other populations living in the developing countries of the southern hemisphere more susceptible to the toxic effects of pollutants present in the living environment.

Within this context and in response to the lack of comprehensive data on levels of PTS in populations residing in South Africa, a pilot project was designed and carried out under the auspices of AMAP, by the South African Medical Research Council and the University of Tromsø, Norway. The main objectives of the pilot study are to: (1) ascertain baseline levels of both toxic metals and persistent organic substances in delivering women and their newborns in selected geographical regions of South Africa, thought to have different types of environmental contamination; (2) identify areas of concern to enable the selection of the most appropriate sites for the comprehensive main study; and (3) build research capacity within collaborating institutions and countries.

Pilot studies in the southern hemisphere countries of Brazil and Australia are also underway.  

Geographical positions of pilot study sites within South Africa

Legend: Site 1=Rural; Site 2= Urban; Site 3=Industrial; Site 4=Atlantic Ocean; Site 5=Mining;
Site 6=Indian Ocean and malaria; Site 7=Inland malaria

For scientific articles on the study findings, please access the E&HRU publications list.

For more information please contact Prof Halina Röllin
Email: hrollin@mrc.ac.za

DDT and current use pesticides in mothers and children in a MALaria CONtrol area in South Africa, MALCON

Malaria is one of the world’s most serious tropical diseases and imposes very high human and economic costs in Africa, including South Africa. DDT has been used in South Africa since 1946 to control and eradicate malaria in malaria endemic regions. However, because of growing concern about possible toxic side effects of DDT use for vector control on the environment and humans, alternative chemical compounds were developed and used. This resulted in the campaign to replace DDT with other pesticides, thought to be less harmful.

Makeshift travelling laboratory

South Africa replaced DDT with pyrethroids in 1996. In a very short time, pyrethroid-resistant mosquitoes caused a localized malaria epidemic resulting in an increase of reported malaria cases from 4117 in 1995 to 64 622 cases in 2000 and a high death rate. The Stockholm Convention saw the urgent and immediate need for South Africa to re-introduce DDT in 2000 until viable, effective and affordable alternatives were found. At present malaria vectora are very successfully controlled by periodical indoor spraying with DDT in affected areas.

Under the South Africa and Norway Programme on Research Co-Operation, a project funded by the NRF is currently in progress that will measure levels of DDT metabolites and other commonly used pesticides in delivering women and cord blood in malaria control areas of South Africa. The project will also ascertain the possible health effects of DDT, as well as synergistic effects of exposure to multiple compounds. The results will inform policies at national level, the Stockholm Convention and the Roll Back Malaria Programme.

Mirriam Mogotsi and field workers at Manguzi Hospital, KwaZulu Natal

For more information, please contact Prof Halina Röllin
Email: hrollin@mrc.ac.za