Toxic chemicals can cause a variety of adverse health effects. Toxic substances such as arsenic, cadmium, lead and sulphuric acid contaminate water and soil, and affect human health. More than 50 000 tonnes of obsolete pesticides have been stockpiled in Africa contaminating tens of thousands of tonnes of soil. These obsolete pesticides represent a major threat for human health (NEPAD 2003). Low-level exposure to some chemicals present in industrial effluent or used as pesticides, such as PCBs, dioxins, and POPs such as DDT, may cause endocrine disruption, undermining disease resistance and affecting reproduction (MA 2006). They are also responsible for more acute health impacts, including poisoning. Persistent organic pollutants cause a range of health problems, even at low levels of exposure, including reproductive and developmental disorders, damage to the immune and nervous systems, and a range of cancers (Gordon and others 2004, MA 2006). Exposure during key phases of foetal development can be particularly damaging (IPEN 2002). Heavy metals pose serious threats, particularly to children and during foetal development (Gordon and others 2004). In Africa, between 18 and 24 per cent of children have concentrations of more than 10 micrograms per decilitre (µg/dl) of blood (Gordon and others 2004). Box 3 gives an overview of problems associated with lead contamination, with a special focus on mining in Central Province in Zambia.

Box 3: Lead poisoning and the tragedy of a mining boom

Lead exposure may come from contaminated air, water or food. Motor vehicle exhaust fumes from leaded fuel, smelters, lead manufacturing and recycling industries, waste sites (eg contaminated landfills), old lead water piping and lead-combining solders, and leaded paint are common sources of lead contamination. The amount of lead that may dissolve in water depends on acidity, temperature, water hardness and standing time of the water. Secondary pollution from industry can contaminate water through the effluents produced. Other sources include the use of lead-containing ceramics for cooking, eating or drinking. In some countries, people are exposed to lead after eating food from cans that contain lead solder in the seams.

In many mining centres, average atmospheric lead concentrations reach 0.3-0.5 µg/m3 and exceed 1 000 µg/g in dust and soils. The people of Kabwe, in Zambia, face a serious threat from lead and zinc mining activities. At its peak, Kabwe was the largest and richest lead mine in Africa. Unfortunately there were few pollution controls. The mine closed in 1994 and since then the town and province have not only faced growing economic hardship but also the risk of lead poisoning. The vegetation, water and soil are contaminated and about 90 000 children are at risk from lead poisoning. Concentrations of 5 µg/dl threaten brain development; in Kabwe, many children have concentrations exceeding 300 µg/dl. Average blood level is 60-120 µg/dl.

Lead can damage the nervous and reproductive systems, and the kidneys, and it can cause high blood pressure and anaemia. Lead accumulates in the bones and lead poisoning may be diagnosed from a blue line around the gums. Children are amongst the most vulnerable. Lead is especially harmful to the developing brains of foetuses and young children and pregnant women. Lead interferes with the metabolism of calcium and Vitamin D. High blood lead levels in children can lead to irreversible learning disabilities, behavioural problems and mental retardation. At very high levels, lead can cause convulsions, coma and death.

To address the problem of lead pollution in Kabwe, the Zambian government has adopted various programmes. There are proposals to either cover the mine dumps with vegetation or cap them with concrete to prevent air pollution. In 2003, the Zambian government asked 2 000 residents to vacate their canal-side homes so that the waterways could be dredged. However, for most residents, finding alternative accommodation is not a reality.

Preventive measures are clearly more appropriate than remedial measures. The World Health Organization (WHO) identifies the following options:

  • Environmental standards that remove lead from petrol/gasoline, paint and plumbing;
  • Removal of lead pipes, or flushing pipes with cold water each morning before drinking if they cannot be removed;
  • Enforcement of occupational health standards;
  • Surveillance of potentially exposed population groups, especially the vulnerable ones (small children, pregnant women, workers);
  • Water treatment;
  • Removal of lead solder from food cans;
  • Use of lead-free paint in homes; and
  • Screening of children for blood levels over acceptable limit and referral for medical care as necessary.

Source: UNEP/FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003

With growing production and consumption, and new economic development, the risks associated with chemical use will increase. This will place new demands on Africa’s chemical management institutions. In addition to intended environmental releases, there is also an increased risk of accidental releases and chemical-related accidents. Examples of hazardous incidents include the misuse of mercury in small-scale mining, PCBs in the electricity sector, DDT in the health sector and pesticides in the agricultural sector.

Box 4: Health and environmental effects of DDT on health and environment
  • DDT disturbs sexual development and behaviour in birds such as gulls.
  • The capacity of the immune system is impaired by DDT, and also by certain synthetic pyrethroids – pesticides that have been promoted as DDT alternatives.
  • The nervous system can suffer permanent damage from exposure during the foetal stage or early in life.
  • Lactation in women can be impaired by DDT – providing a possible link with oestrogen mimicry.

Source: Mörner and others 2002

These chemicals pose serious risks that are exacerbated by the lack of adequate access to information regarding safe handling, use and disposal of chemicals. See for example the risks associated with Lead in Box 3 and DDT in Box 4. Poverty and lack of access to information may exacerbate these negative impacts. In the context of scarce resources, chemical containers are often re-used by rural people for household purposes including the collection of water and can result in poisoning. More than 11 million poisoning cases by pesticides occur annually in Africa (NEPAD 2003), yet few African countries have specialized poison centres. In 2004, only ten African countries had poison centres, and none had more than five (Gordon and others 2004). Further, since agriculture is the main employer for women and children, they are the most exposed to chemical risks. In many cases, both for subsistence and commercial farming, producers and workers have insufficient knowledge about the health risks posed by chemicals and therefore fail to take adequate protective measures.


The chemical industry is dependent on raw materials including coal, gas, air, water, minerals and genetic resources. With increased production the demand for these resources will also increase. Promoting sustainable use of natural resources and the adoption of cleaner production must, therefore, be a focus of industrial management. The industry itself is increasingly recognizing this through, for example, environmental standards adopted by the International Standards Organization (ISO). Consumers are also increasingly demanding such integrated approaches.

Industrial processes require large amounts of water and energy. In non-OECD countries, the use of energy for chemical production has increased. Given the shift of the industry to developing countries there has also been a shift in the share of energy use in these countries from 20 per cent in 1971 to 43 per cent in 1998 (Buccini 2004). Increasing energy use also results in increased emissions of greenhouse gases (GHG) that contribute to climate change (see Chapter 2: Atmosphere). Specific threats posed by climate change and variability are discussed in Chapter 1: The Human Dimension (health), and Chapter 3: Land (food security). The chemicals industry accounts for one-quarter of the total releases of CO2 from industrial sector operations, although this amounted to only 4 per cent of the emissions from all sources in 1997 (Buccini 2004).