Message from the NSTF Executive Director


Toxic heavy metals – weighty health burdens

In this year of the Periodic Table of Chemical Elements, the National Science and Technology Forum (NSTF) hosted presentations and discussions about various elements/minerals/commodities in relation to society during three discussion forums. These were covered in the recent a Business Report supplement, in which a wall chart of the Periodic Table was also reproduced for use by learners, students and teachers.

The presentations of our speakers are so rich in thought-provoking content that it is worth viewing the slides and videos on the website: here and there.  Twelve of the speakers were cited in the newspaper. There were some speakers who had to be omitted, not because of lesser quality but due to the limits of space. In this piece the focus is on heavy metals, particularly on lead, its health hazards, mine waste and South African Medical Research Council (SAMRC) research including the identification of toxic metals lurking in commonly used cooking pots. The latter research is in progress and was presented by Professor Renee Street of the Environment & Health Research Unit at the SAMRC, who was one of the speakers whose presentation was omitted from the newspaper feature.

The role of government

It is important for governments to ensure healthy environments and prevent people from coming into contact with toxic metals. Researchers play a crucial role in identifying hazards but governments have to take appropriate action in response. In South Africa we are fortunate that such research is being done and that the legislation provides for remedial action and stipulates punishable offences. The problem, as is so often the case, is that too little action is carried out in line with the good intentions of the promulgated legislation. Remedial action to curb the harm caused by abandoned mine waste also takes a long time.

The South African government is aware of the environmental and health concerns associated with derelict and abandoned mines. It is also aware of the need for clean air free from harmful particulate matter. The legislation and regulations are in place to address these issues, but does the implementation of well-formulated measures actually take place and to what extent? Is a holistic approach followed, linking the mine residue areas with the health risks and then testing and treating all residents?

In the case of mine rehabilitation, legislation requires applicants wishing to mine in an area to make “financial provision for the rehabilitation, closure and ongoing post decommissioning management of negative environmental impacts”. Although the government has also been addressing the clean-up of mine dumps in Gauteng, it has to be done incrementally to manage the costs involved. However, the ongoing health crises associated with mine dumps are also the government’s responsibility. Housing should be planned in such a way that people no longer live next to the abandoned mines or mine tailings, and this does not always happen.

The Department of Environmental Affairs (DEA) says in a report (paragraph 10.5.1) on its website:

“Elevated Particulate Matter concentrations still occur in various parts of the country, exceeding the South African annual PM10 ambient air quality standard especially in residential areas. Elevated PM10 concentrations in excess of air quality limits are also recorded by some industrial monitoring sites. Most of the exceedances of the PM10 annual standard occur in the priority areas, so re-affirming the decisions to declare such areas as priority zones.

“National government has set a target that by 2020, air quality in all low-income settlements should be in full compliance with ambient air quality standards. Particulate matter is therefore a national concern due to exceedances of the National Ambient Air Quality Standards (NAAQS), which are designed for the protection of the environment and human health.”

(Particulate matter refers to harmful microscopic particles suspended in the air).


Lead (Pb) – atomic number 82 – is extremely useful, but deadly. It is a metal that has been used by humankind for at least five millennia. It is so versatile and has so many applications in long established technologies as well as new ones, that it is a major commodity, with countries competing for a share in world production. South Africa currently produces around 40 000 tons, and ranks about 14th among lead producers in the world.

Lead’s multitude of uses over the ages included many innovative technologies that have meant progress and improvement for various societies and humankind as a whole. These included tablets for writing, lead being soft enough to scratch, plumb lines to determine depth of oceans, and water pipes during the time of the Roman Empire.

Being invisible as particulate matter in the air and dust, or disguised in a variety of metals melted together, or in paint, people are not overly concerned by its presence, if they are aware of its severely harmful effects at all. However, only 100 mg/m3 of air is regarded as ”immediately dangerous to life and health”. (The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that are “likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment”. Examples include smoke or poisonous gases.)

In the US, children’s exposure to lead is still – to this day – an issue that demands attention. The report of a national workshop – Eliminating Lead Risks in Schools and Child Care Facilities: A United and Urgent Call to Action for Children, in 2018 – refers to the great strides of progress that have been made in the US with the ban on lead in petrol and in most paints. However, children’s exposure to lead continues through peeling paint and even through drinking water. An urgent appeal was made to the authorities to address these problems.

Why is lead so highly toxic?

Lead interferes with enzyme functioning. It mimics or displaces metals that play an important role in enzymatic reactions, such as calcium, iron and zinc. High levels of calcium and iron are critical for resisting lead poisoning, while people who have shortages of these minerals are more vulnerable to the effects of lead. By mimicking calcium, lead gains access to the brain, and destroys neurons by attacking their myelin sheaths and interferes with neurotransmission routes.

Lead may cause miscarriage in pregnant women, and reduce fertility levels in men.

It is very harmful for children, as the brain is developing and lead interferes in various ways, including synapse formation and neurochemical development.

An old lead mine in Zambia

Kabwe in Zambia has made South African news for the wrong reasons. See the recent Mail&Guardian and Daily Maverick articles.

A recent Human Rights Watch report on areas of Kabwe, Zambia, says that particularly high levels of lead are found where one third of the population lives. The areas in and around Kabwe are dusty, roads are untarred, and wind distributes the dust with its lead particles. With the rate of absorption of lead being four to five times higher in children than adults, the children in these areas are particularly vulnerable. They play outside in the dusty soil as there is no other place to play, breathing the contaminated air and getting the dust onto their hands and into their mouths.

Children who have absorbed high levels of lead and are not treated can suffer learning disabilities, behavioural problems and growth impairment. The brain and central nervous system are affected, as well as various other organs. The lead remains in the body indefinitely once it has accumulated. Adults’ health is also affected and lead can be transmitted from mother to baby in the womb and through breast milk.

The Kabwe mine is a legacy of colonialism. It was opened in 1904 and owned and run by British companies, until 1970 when it was nationalised by a newly independent Zambia. Anglo-American South Africa was involved from 1927. Smelter fumes had covered much of the surrounding soil with lead dust for decades. Now, 25 years after it closed, the lead levels in the area still exceed international standards by far. There are still tailings and other waste from the lead mine and smelter. A large waste dump known as “Black Mountain” is being used by small scale miners. Because of dusty environments, a shortage of water, as well as the fact that undernourishment increases the rate of lead absorption, the very poor are the worst affected by lead in the environment.

Efforts to control the dust, and test and treat the people, have been made by the Zambian government, but not sustained. Currently there is no chelation medicine for treating lead poisoning or lead test kits in stock in government-run health facilities in Kabwe. There is also a shortage of data to inform government action. Zambia’s health system does not collect data on lead poisoning, so there is no indication of the true extent of even the worst medical cases. Human Rights Watch has made recommendations to the Zambian Government in the report to address the problems of lead contamination.

But who are we to judge Zambia? Do our clinics have the necessary supplies to test for the effects of toxic metals in the environment? Is the required data captured on detrimental effects of metals in the environment? Dusty roads and yards are also most people’s reality in South Africa. And what are we doing about the very significant health hazards from mine tailings and abandoned mines around Johannesburg?

The Mail&Guardian referred to Kabwe as the most toxic town in Africa. I suspect that that is not true. Johannesburg or towns that make up Johannesburg, is surely an obvious contender for the title.

Lead poisoning – the silent epidemic in South Africa

Professor Renee Street of the Environment & Health Research Unit at the South African Medical Research Council (SAMRC) presented on the SAMRC’s research into heavy metals’ contamination at one of the NSTF discussion forums on chemical elements in March 2019. She spoke about lead in petrol, paint and in garden soils.

South Africa made progress by phasing out lead (tetraethyllead) in petrol by 1996, similar to and at about the same time as the United States and the European Union, who had gotten rid of it by 2000. The SAMRC’s efforts were critically important in South Africa’s case. Its research was presented to cabinet to recommend the complete phase out of leaded petrol. Ninety percent of South African children that were tested were found to have high blood levels of lead in the 1970s. SAMRC research confirmed that there was a decline in the lead blood levels of children since the introduction of unleaded petrol.

About 20% of homes in Johannesburg is estimated to have lead containing paint on their surfaces. In old and poorly maintained houses and buildings, the paint flakes off these surfaces and can cause lead contaminated dust, or end up in young children’s hands and mouths.

Garden soil in four areas of Johannesburg have also been shown by the SAMRC to be contaminated by both lead and arsenic. Bertrams is by far the worst in this regard. Riverlea was found to be the worst for arsenic contamination of garden soils.

Professor Angela Mathee, also of the Environment & Health Research Unit, SAMRC, participated in a lecture series of the Environmental Health Research Network. According to her presentation published online, entitled The ongoing struggle to get lead out of paint in South Africa, she said that lead poisoning is known as the silent epidemic”. It seems to be a wide-spread problem in our country but is not always diagnosed as it can only be confirmed by a specific blood test. In 2007 by far the majority of grade one children in a large sample of Johannesburg children had lead poisoning. Only about 15% had safe lead blood levels. Various studies had been done by the SAMRC, including playground equipment in Johannesburg and the lead content in enamel paints available in shops. 60% of the paint for sale had elevated lead levels and there were no warning labels. Only in 2009, regulations to control the use of lead in paint were promulgated under the Hazardous Substances Act 15 of 1973. Three years later, 40% of paints for sale still had elevated lead levels.

Educational material to teach people about the hazards of lead was developed by the SAMRC and can  be found here:

An article in the South African Medical Journal of 2017 focused on lead exposure of workers at shooting ranges. The authors state that there is not enough research and information about lead exposure in Africa, although the dangers of lead exposure are well known. Both the workers tested and interviewed had extremely high levels of lead in their blood and experienced symptoms consistent with lead poisoning. One person had worked at a shooting range as cleaner for 22 years. The other had worked for only three years as administrator and instructor. He was 27 years old. His lead blood level was high enough to justify resignation for the sake of his health. Neither had ever been tested for blood levels before.

I think it is safe to say there is hardly any awareness of the poisonous nature of lead among the public in general, including those who work with lead every day.

Toxic heavy metals in artisanal 3-legged cooking pots in South Africa

A current study led by Professor Street is investigating toxic metals in artisanal cooking pots and what effect the leaching metals in the food could have on those who eat it. A commonly used alternative to the three-legged iron cooking pot is the cheaper version made mainly from aluminium. These seem to be commonly available across South Africa and such pots have been collected from five provinces for the study. Some makers of the pots have been observed and interviewed. Various scrap metals are melted together in home-made furnaces, and cast in soil moulds. The work is difficult and dangerous, with the makers probably having no protective gear and inhaling the fumes that are emitted during the process. Some of the pots collected have been analysed. Results vary and the study is ongoing. The dangerous metals contained in the pots definitely leach into food as it is cooked. Every time the cooking pot was boiled and tested, the deterioration from the previous test was evident. The levels of leaching lead in these pots is “frightening”, at about 149 micrograms, compared to the EU permitted level of 10 micrograms.

It is possible that most of such cooking pots found in South Africa are manufactured in Mozambique in the same manner as that practiced by the pot makers in South Africa. Scrap metal of various kinds and origins seem to be melted together to make the pots.

Mine dumps

Gold mine tailings (mine dumps) in Gauteng contain various heavy metals, including lead. Environmental contamination by toxic metals is a typical problem associated with mining worldwide. The metals are dissolved and carried away by run-off and ground water and can pollute streams, rivers, crop fields and pastures. The dust from mine tailings is distributed by wind, especially over the long term (as with Johannesburg’s mine dumps). Because mine tailings and their run-off are acidic (highly acidic around Johannesburg) metals are dissolved in the water and become bioavailable, thereby directly affecting living organisms. Plants can accumulate lead and if contaminated plants are eaten by humans or animals over a long period of time, the bioaccumulation can lead to serious health problems. During smelting of metals, air pollutants are released in great quantities, including suspended particulate matter which includes metals.

The Gauteng City Region Observatory (GCRO)’s research on derelict mines

The Gauteng City Region Observatory (GCRO) produces maps and research reports and “builds the data and analysis to help inform development in this region”. The GCRO report on Mining landscapes of the GCR was published in January 2018 and is well worth a read, for its information, insights and a photo essay on scrap metal collectors on Johannesburg mine dumps.

An occasional paper called Acid Mine Drainage and its Governance in the Gauteng City-Region was written by Kerry Bobbins for the GCRO in May 2015 as a precursor to the above report. This paper sets out the situation re Acid Mine Drainage (AMD) very clearly.

AMD contains heavy toxic metals which are transported wherever the AMD water seeps and flows. Contact with water containing AMD can directly affect people’s health. Heavy metals in AMD contaminated soil are also taken up by plants and transferred to humans and animals, causing severe health problems, placing agriculture and its industries at risk, and damaging ecosystems.

The legacy of spent mines is now a heavy burden on the government and taxpayers, including an increased burden on public healthcare.

The Department of Mineral Resources (DMR) identified a total of 6 152 ownerless and derelict mines. In 2011, the total cost of rehabilitation was estimated at R30 billion. Funds for rehabilitation were initially allocated by the DMR to the rehabilitation of 37 ownerless and derelict mines over three years. At least another 150 mines would have been funded in the three years up to 2018.

There have been many news reports on AMD over the years and awareness groups have sought to bring the effects of AMD in Gauteng to the attention of the authorities as a matter to be addressed with urgency, particularly when AMD decanted on the West Rand, causing damage as it flowed with the river. Government responded and the Department of Water Affairs (DWA) introduced measures, both short and long-term to deal with these issues.

Early in 2010 an Inter-Ministerial Committee (IMC) was formed to respond to decant in the Western Basin specifically, and the threat of AMD in the Gauteng City Region and South Africa more generally. The IMC appointed a Team of Experts (ToE) that included representatives from the Council for Geoscience, Council for Scientific and Industrial Research (CSIR), DWA, DMR, Mintek, Tshwane University of Technology, University of the Witwatersrand, and University of the Free State to investigate and make recommendations around the AMD crisis (PMG, 2011b). The ToE’s report was entitled Mine water management in the Witwatersrand Gold Fields with special emphasis on Acid Mine Drainage.


The opinions expressed above are those of the Executive Director, Jansie Niehaus, and do not necessarily reflect the views of the Executive Committee or members of the NSTF.