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For decades, families in communities around Johannesburg have been living close to huge gold mining waste dumps. For many residents the dust that is released there is just part of everyday life – but it can contain natural uranium compounds that come to the surface with the mined rock. A new study in the journal Environmental Geochemistry and Health (DOI: 10.1007/s10653-025-02874-2) reveals how this exposure is reflected in children’s hair.
The Witwatersrand Basin around Johannesburg hosts the world’s largest known gold deposits, which have been mined for 140 years. With the start of industrial mining, huge quantities of mined rock, which contain not only the precious metal but also toxic substances such as lead, arsenic, and uranium, were crushed and processed. Intensive gold mining resulted in large tailings dumps covering approximately 400 square kilometers across the Witwatersrand Basin.
“The dumps are often located directly in densely populated residential areas. It is known that toxic substances are carried in dust particles by wind, soil, and water right up to the houses, particularly in the dry season,” explains Dr. Susanne Sachs of the Institute for Resource Ecology at HZDR. “Earlier investigations by our project team uncovered increased levels of uranium in the hair samples of people living near waste dumps in the South African mining region.” It is known that people can come into contact with uranium via the air, water, soil, and food, especially vegetables and cereals, that have been grown in contaminated environments. The study published now investigates how people are exposed to uranium – particularly children living near gold mining dumps – and how much of this heavy metal enters their bodies. They are compared to children from regions where gold has never been mined.
Hair as an object of study – and what the samples reveal
To address this issue, the South African research team collected more than 400 hair samples from children in several communities close to mining dumps as well as in uncontaminated regions. Hair is particularly suitable for such tests, because it stores substances from the body throughout the entire growth phase – unlike blood that tends to reflect only very recent exposure.
“In the lab, we initially ground, homogenized and carefully cleaned the samples to remove any surface dust contaminants following a procedure jointly developed with our colleagues from the Wismut Laboratory in Seelingstädt. After acid digestion of the hair samples, our colleagues at VKTA used a high-precision mass spectrometry method that can reliably measure even the smallest amounts of trace elements,” says Sachs, explaining the test procedure. This approach is important because it differentiates between external input and substances that have actually been absorbed. In addition, the South African team collected information on the children’s age, gender and state of health as well as their living environment, proximity to tailings dumps, and other factors that could influence exposure.
The results reveal a clear pattern: children living in gold mining areas have higher average uranium levels in their hair than children from reference sites where no gold mining activities ever took place. The study also shows that not only the place where exposure occurs, but also gender and age are important factors influencing the concentrations of uranium in hair. At individual level, the study confirms what results of environmental measurements have been suggesting for some time: living in settlements in close proximity to gold mine tailings increases the risk of uranium uptake and has a noticeable impact on people’s everyday lives.
Significance for the communities affected
The values measured do not allow immediate conclusions to be drawn about the health impacts on individual children, for which a follow-up epidemiological study would be necessary. But the researchers emphasize the significance of the observation itself because it shows that exposure to uranium in the environment can lead to the enrichment of uranium in biological samples. In a region that has been shaped by gold mining for decades, the study delivers important information: due to increased environmental contamination, additional measures are required to monitor and reduce exposure to uranium in order to protect the people living there. “The study helps to reinforce communities’ awareness without stoking fears unnecessarily,” says Sachs.
This work is the result of a comprehensive joint project headed by the South African Medical Research Council (SAMRC) that was launched several years ago. In addition to HZDR, VKTA, the International Agency for Research on Cancer (IARC) (the cancer research agency of the World Health Organization), Wismut GmbH, and the South African North-West University in Vanderbijlpark, the University of Johannesburg, and the University of KwaZulu Natal were also involved in this project.
The research team considers this work to be an important step to better understanding the challenges facing mining areas and thus helping to protect the population’s health. It shows that industrial activity can lead to exposure to toxic substances in the course of people’s everyday lives and that scientific cooperation can help to develop pathways to a healthier, more secure future for the communities affected. More research is needed to understand whether the measured uranium levels in children lead to adverse health effects.
Publication:
B. Shezi, R. Street, V. Nkosi, F. Winde, H. Nuernberger, J. Schüz, S. Sachs, L. Zupunski, E. Ostroumova, J. Seibt, R. Bertheau, R. Husar, U. Czeslik, A. Mathee, Uranium concentration in children’s hair samples and residential soil samples near mine tailings facilities, in Johannesburg, South Africa, in Environmental Geochemistry and Health, 2025 (DOI: 10.1007/s10653-025-02874-2)
Additional information:
Dr. Susanne Sachs
Institute for Resource Ecology at HZDR
Phone: +49 351 260 2436 | Email: s.sachs@hzdr.de
Media contact:
Simon Schmitt | Head
Communications and Media Relations at HZDR
Phone: +49 351 260 3400 | Mob.: +49 175 874 2865 | Email: s.schmitt@hzdr.de
The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) performs – as an independent German research center – research in the fields of energy, health, and matter. We focus on answering the following questions:
• How can energy and resources be utilized in an efficient, safe, and sustainable way?
• How can malignant tumors be more precisely visualized, characterized, and more effectively treated?
• How do matter and materials behave under the influence of strong fields and in smallest dimensions?
To help answer these research questions, HZDR operates large-scale facilities, which are also used by visiting researchers: the Ion Beam Center, the Dresden High Magnetic Field Laboratory and the ELBE Center for High-Power Radiation Sources.
HZDR is a member of the Helmholtz Association and has six sites (Dresden, Freiberg, Görlitz, Grenoble, Leipzig, Schenefeld near Hamburg) with almost 1,500 members of staff, of whom about 700 are scientists, including 200 Ph.D. candidates.
Dr. Susanne Sachs
Institute for Resource Ecology at HZDR
Phone: +49 351 260 2436 | Email: s.sachs@hzdr.de
B. Shezi, R. Street, V. Nkosi, F. Winde, H. Nuernberger, J. Schüz, S. Sachs, L. Zupunski, E. Ostroumova, J. Seibt, R. Bertheau, R. Husar, U. Czeslik, A. Mathee, Uranium concentration in children’s hair samples and residential soil samples near mine tailings facilities, in Johannesburg, South Africa, in Environmental Geochemistry and Health, 2025 (DOI: 10.1007/s10653-025-02874-2)
https://www.hzdr.de/presse/uran_gold
Mine dump situated directly behind community homes, Witwatersrand Basin region.
Source: Angela Mathee
Copyright: Angela Mathee
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Mine dump situated directly behind community homes, Witwatersrand Basin region.
Source: Angela Mathee
Copyright: Angela Mathee
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