* Lead is a
cumulative toxicant that affects multiple body systems and is
particularly harmful to young children.
* Lead in the body is distributed to the brain, liver, kidney and
bones. It is stored in the teeth and bones, where it accumulates
over time. * Human exposure is usually assessed through the
measurement of lead in blood.
* Lead in bone is released into blood during pregnancy and becomes a
source of exposure to the developing fetus.
* There is no known level of lead exposure that is considered safe.
* Lead exposure is preventable.
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, leaded gasoline, and
leaded aviation fuel. 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, lead crystal
glassware, 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 miscarriage,
stillbirth, premature birth and low birth weight, as well as minor
malformations.
Sources and routes of exposure
People can become exposed to lead through occupational and
environmental sources. This mainly results from:
inhalation of lead particles generated by burning materials
containing lead, for example, during smelting, recycling, stripping
leaded paint, and using leaded gasoline or leaded aviation fuel; and
ingestion of lead-contaminated dust, water (from leaded pipes), and
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 4–5
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
from decaying lead-containing paint. This route of exposure is
magnified in children with pica (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 Nigeria, Senegal and other countries.
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
remobilized into the blood during pregnancy, thus exposing the
fetus. 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 fetus) and the impoverished.
Health effects of lead poisoning on children
Lead can have serious consequences for the health of children. At
high levels of exposure, lead attacks the brain and central nervous
system to cause coma, convulsions and even death. Children who
survive severe lead poisoning may be left with mental retardation
and behavioural disorders. At lower levels of exposure that cause no
obvious symptoms, and that previously were considered safe, lead is
now known to produce a spectrum of injury across multiple body
systems. In particular lead can affect children’s brain development
resulting in reduced intelligence quotient (IQ), behavioural changes
such as reduced attention span and increased antisocial behaviour,
and reduced educational attainment. Lead exposure also causes
anaemia, hypertension, renal impairment, immunotoxicity and toxicity
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. Even blood lead concentrations as low as
5 µg/dL, once thought to be a “safe level”, may be associated with
decreased intelligence in children, behavioural difficulties, and
learning problems.
Encouragingly, the successful phasing out of leaded gasoline in most
countries, together with other lead control measures, has resulted
in a significant decline in population-level blood lead
concentrations. There are now only 3 countries that continue to use
leaded fuel.
Burden of disease from lead exposure
The Institute for Health Metrics and Evaluation (IHME) has estimated
that, based on 2015 data, lead exposure accounted for 494 550 deaths
and loss of 9.3 million disability-adjusted life years (DALYs) due
to long-term effects on health. The highest burden is in low- and
middle-income countries. IHME also estimated that lead exposure
accounted for 12.4% of the global burden of idiopathic developmental
intellectual disability, 2.5% of the global burden of ischaemic
heart disease and 2.4% of the global burden of stroke.
WHO response
WHO has identified lead as 1 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.
WHO has made available through its website a range of information on
lead, including information for policy makers, technical guidance
and advocacy materials.
WHO is currently developing guidelines on the prevention and
management of lead poisoning, which will provide policy-makers,
public health authorities and health professionals with
evidence-based guidance on the measures that they can take to
protect the health of children and adults from lead exposure.
Since leaded paint is a continuing source of exposure in many
countries, WHO has joined with United Nations Environment Programme
to form the Global Alliance to Eliminate Lead Paint. This is a
cooperative initiative to focus and catalyse efforts to achieve
international goals to prevent children’s exposure to lead from
leaded paints and to minimize occupational exposures to such paint.
Its broad objective is to promote a phase-out of the manufacture and
sale of paints containing lead and eventually eliminate the risks
that such paints pose.
The Global Alliance to Eliminate Lead Paint is an important means of
contributing to the implementation of paragraph 57 of the Plan of
implementation of the World Summit on Sustainable Development and to
resolution II/4B of the Strategic Approach to International
Chemicals Management (SAICM), which both concern the phasing out of
lead paint. The elimination of lead paint will contribute to the
achievement of Sustainable Development Goal target 3.9: By 2030
substantially reduce the number of deaths and illnesses from
hazardous chemicals and air, water, and soil pollution and
contamination; and target 12.4: By 2020, achieve the environmentally
sound management of chemicals and all wastes throughout their life
cycle, in accordance with agreed international frameworks, and
significantly reduce their release to air, water and soil in order
to minimize their adverse impacts on human health and the
environment.