Lead is a naturally occurring toxic metal found in the earth’s crust. Its widespread use has resulted in extensive environmental contamination, human exposure and significant public health problems in many parts of the world.
Important sources of environmental contamination include; mining, smelting, manufacturing and recycling activities and, in some countries, the continued use of leaded paint and leaded gasoline.
More than three quarters of global lead consumption is for the manufacture of lead-acid batteries for motor vehicles. Lead is, however, also used in many other products, for example, pigments, paints, solder, stained glass, crystal vessels, ammunition, ceramic glazes, jewellery, toys and in some cosmetics and traditional medicines.
Drinking water delivered through lead pipes or pipes joined with lead solder may contain lead. Much of the lead in global commerce is now obtained from recycling.
Young children are particularly vulnerable to the toxic effects of lead and can suffer profound and permanent adverse health effects, particularly affecting the development of the brain and nervous system.
Lead also causes long-term harm in adults, including increased risk of high blood pressure and kidney damage. Exposure of pregnant women to high levels of lead can cause miscarriages, stillbirths, premature birth and low birth weight, as well as minor malformations. People can become exposed to lead through occupational and environmental sources.
This mainly results from: l Inhalation of lead particles generated by burning materials containing lead, such as during smelting, informal recycling, stripping leaded paint and using leaded gasoline. Others are ingestion of lead-contaminated dust, water (from leaded pipes), food (from lead-glazed or lead-soldered containers).
The use of some traditional cosmetics and medicines can also result in lead exposure. Young children are particularly vulnerable because they absorb four to five times as much ingested lead as adults from a given source.
Moreover, children’s innate curiosity and their age-appropriate hand-to-mouth behaviour result in their mouthing and swallowing lead-containing or lead- coated objects, such as contaminated soil or dust and flakes of decaying lead- containing paint.
This route of exposure is magnified in children with persistent and compulsive cravings to eat non-food items, who may, for example pick away at, and eat, leaded paint from walls, door frames and furniture.
Exposure to lead-contaminated soil and dust resulting from battery recycling and mining has caused mass lead poisoning and multiple deaths in young children in Senegal and Nigeria.
Deadly effects of lead Once lead enters the body, it is distributed to organs such as the brain, kidneys, liver and bones. The body stores lead in the teeth and bones where it accumulates over time.
Lead stored in bone may be remobilised into the blood during pregnancy, thus exposing the foetus. Undernourished children are more susceptible to lead because their bodies absorb more lead if other nutrients, such as calcium, are lacking.
Children at highest risk are the very young (including the developing foetus) and the impoverished. Lead exposure also causes anaemia, hypertension, renal impairment and poisoning to the reproductive organs.
The neurological and behavioural effects of lead are believed to be irreversible. There is no known safe blood lead concentration. But it is known that, as lead exposure increases, the range and severity of symptoms and effects also increases.
The successful phasing out of leaded gasoline in most countries has resulted in a significant decline in population- level blood lead concentrations.
World Health Organisation (WHO) response
WHO has identified lead as one of 10 chemicals of major public health concern, needing action by member states to protect the health of workers, children and women of reproductive age. It is developing guidelines on the prevention and management of lead poisoning.