United States
Environmental Protection
Agency
Office of Pesticides and
Toxic Substances TS-793
Washington D C 20460
x-sEPA
Lead—
what is it?
Why is lead
a problem?
Toxics Information
Series
Lead
The use of lead dates from the earliest civiliza-
tions of man. Lead coins and medallions recovered from
ancient Egyptian ruins, and lead water pipes from the
remains of imperial Rome are prime examples. The toxic
effects of lead in workers and others exposed to large
quantities are also well documented. But recent medical
research indicates that lead may cause serious adverse
health effects even at very low levels if exposure
occurs over prolonged periods.
The build-up"~b~f lead in the environment and its
continued use throughout the world has generated
scientific and public concern alike about the potential
dangers to the public's health. This Information
Bulletin describes the hazards of lead and what the U.S.
Environmental Protection Agency (EPA) and others are
doing to protect public health. '
Lead is a soft bluish or silvery grey heavy metal
usually found in sulfite deposites in association with
other minerals, particularly zinc and copper. Fourth
among non-iron metals in tonnage in the U.S., approxi-
mately 1.35 million metric tons were produced in 1976,
primarily during the smelting of zinc. Although some
uses of lead have decreased in recent years, this has
been offset by increased utilization in other
industries, causing lead production to remain relatively
stable. Fifty-four percent of the lead produced in this
country is used to lead storage batteries. Of the
remainder, approximately 21 percent goes into making
metal products such as solders, bearings, printed type,
brasses, etc.; 16 percent to gasoline antiknock
additives; 6 percent to ceramics and pigments; and 3
percent for miscellaneous uses. Because of its
industrial value, approximately 35 percent of the world
supply of lead comes from recycled products, primarily
batteries, and manufacturing scrap. Easily melted,
rolled cast and extruded, lead is also valuable for its
low heat, electrical and radioactive conduction and its
resistance to corrosion.
Lead is a problem because it causes serious adverse
health effects at both high and low levels of exposure,
and because man's use of the metal has made it widely
available in the environment.
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There is strong scientific evidence that long-term
global dispersion and accumulation of lead have
occurred. Studies in Greenland show that glacial ice
formed around 1750 has lead concentrations 25 times
greater than ice estimated to have been formed in about
800 B.C. From 1750, the concentration rose steadily
until about 1940, when it increased sharply. The most
recent ice layers examined (formed in about 1968) have a
lead concentration 400 times greater than natural
background levels.
As an element, lead cannot be broken down into less
toxic components by deliberate manipulation or by
natural forces. Once released into the environment, it
remains available to living organisms.
Redistribution of lead in the environment occurs
primarily through air emissions, most of which emanate
from the combustion of leaded gasoline. Airborne lead
emissions are also produced in the processing of lead
additives, the manufacture of storage batteries and
other industrial processes utilizing lead. Municipal
incinerators and coal-burning generators may also emit
lead. Lead enters waterways through municipal and
industrial waste water discharges, and is cleared from
the air by rain. However, because of the tendancy of
organic matter to firmly bind or attach to lead, it is
rapidly removed from water when it passes through soil
and bottom sediment. Lead may also be deposited in soil
directly from the air or in sewage sludge.
Plants absorb relatively small amounts of lead from
the soil and, in most cases, the absorbtion rate is very
low. High concentrations of lead may form from aerial
deposition of lead on plants near smelters. Animals, in
turn, retain the lead ingested with the plants. Another
source of contamination is the use of lead-contaminated
sewage sludge fertilizer on agricultural land, which
will influence the lead content of fruits and vegetables
(due to surface contamination) and grazing animals (due
to direct consumption of the sludge). In addition, the
way food products are packaged may affect the total lead
content. Canned foods, for example, have been found to
have considerably higher lead levels than do the same
items frozen or packed in glass.
Human exposure to lead occurs primarily through
inhalation of air and ingestion of lead-contaminated
food and water. Predictably, the highest lead levels
are found in population centers. Workers in lead
industries and persons living near dense automobile
traffic or in the vicinity of lead smelters are
generally exposed to appreciably higher quantities of
lead than others. Smokers may also inhale lead with
contaminated tobacco smoke, although little is known
about the concentrations of lead in tobacco. Man's
exposure to lead through water is generally low in
comparison with exposure through air and food.
The body's absorption and retention of lead from
environmental sources depends on the amount of lead
present, its physical and chemical state, and the age,
physical activity and health of the individual. Men
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engaged in heavy work breathe more air and eat more food
than sedentary individuals of the same weight, while a
child's intake of food and air is approximately equal to
that of middle-aged adults. Because of these variables,
scientists are unable to establish predictable daily
absorption rates. It is generally estimated, however,
that 35 percent of the lead inhaled is deposited in the
lungs, and 10 percent of lead ingested is absorbed by
the gastrointestinal tract.
Of the total amount of lead absorbed by the body,
five to six percent is contained in blood and soft
tissue; the rest is located in bones. This skeletal
concentration of lead increases throughout life, and is
released very slowly. The lead in blood and soft tissue
is discharged from the body more rapidly than that in
bone, but the exact rate has yet to be determined.
Blood lead levels (Pb-B) are considered useful
indicators of current and/or recent lead exposures, and
are often used to compare exposure rates among given
populations. Determination of the Pb-B levels at which
adverse health effects appear is also a useful tool in
gauging toxic exposure levels.
Lead causes both acute and chronic health effects,
depending on the amount of exposure. Acute effects
produced by exposure to large doses of lead have been
recognized since the mid-1800's. Acute poisoning
produces neurological, blood and kidney effects, all of
which may be accompanied by symptoms such as headache,
dizziness, insomnia, loss of appetite and a metallic
taste in the mouth.
Neurological effects; Symptoms of neurological
damage in acute poisoning include malaise, weakness,
nervous irritability, muscle and joint pain, and fine
V tremors. Severe lead poisoning can result in serious
brain damage leading to coma and death. Repeated
gj attacks of acute poisoning over many years in workers
has resulted in weakness of extensor muscles in arms and
V in legs which may progress to palsy.
j. Intestinal symptoms; Constipations and abdominal
"j cramping are classic signs of acute poisoning. Surgery
has occasionally been performed to relieve severe
abdominal pain.
Kidney disease; Two types of kidney disease have
^ been documented in acute poisoning. One is a reversible
structural and functional change in the kidney evidenced
by increased urinary excretion of amino acids, glucose
and phosphate. The second is an irreversible condition
seen particularly in workers with excessive lead
exposures for more than two or three years. This
condition is characterized by progressively more severe
structural changes leading to eventual kidney failure.
The increase of lead in the environment has focused
attention on the potential for widespread chronic lead
poisoning. Chronic poisoning from long-term, low level
exposure is evident in blood and neurological disorders.
Blood disorders; Lead interferes with the syn-
thesis of hemoglobin, resulting in anemia. Anemia
resulting from acute poisoning may also be accompanied
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What is the
government
doing about
this hazard?
by palloro Chronic lead poisoning produces the same
anemic conditions evidenced in acute poisoning,,
Furthermore, even at very low Pb-B levels before anemia
is evident? lead inhibits certain enzymes important in
the formation of blood components, especially in women
and children. The enzymes are just as important in men
but the effect of lead (inhibition of the enzymes) is
observed at lower exposure levels in infants, children,
and the fetus» Thus, pregnant women or women of
childbearing age need to be more cautious.
Neurological effects; The toxic effects of lead on
the nervous system vary with the duration and intensity
of exposure., In recent studies among workers exposed to
lead at their jobs, hearing, eye-hand coordination and
muscular strength and endurance were all affected by the
amount of lead in the body. Tremors and spychological
symptoms (hostility, aggression and anxiety) were also
evident indicating that brain and nerve damage may also
result from low-level exposure to lead.
Several Federal agencies have taken steps to reduce
the exposure of the general public to lead. As a result
of auto emission controls initiated by Congress in the
Clean Air Act Amendments of 1970, the use of lead
additives in gasoline is being phased out. EPA esti-
mates that 50 percent of the gas produced and used in
this country is now lead-free. Also, under the
authority of the Clean Air Act, EPA has set ambient air
quality and emission standards for industry.
EPA established effluent guidelines for -several
lead industries to control lead in water, under the
authority of the Clean Water Act. The Agency has also
proposed a water quality criteria which can be used as
the basis for further regulation of lead in water by the
Agency or individual states. Consideration is being
given to a recent National Academy of Sciences
recommendation to reduce the current drinking water
standard of 50 micrograms of lead per liter of water
(50ug/l) to 25ug/l. Lead and lead compounds have also
been listed as hazardous wastes under the Resource
Conservation and Recovery Act (RCRA), and EPA has
promulgated rules governing the management of hazardous
waste from the time of production to ultimate
disposalo The Agency also regulates the dumping of lead
wastes at sea.
The Food and Drug Administration (FDA) has
initiated a voluntary industrial program to reduce lead
levels in canned foods such as evaporated milk, juices
and baby foods. The Lead-Based Paint Poisoning
Prevention Act of 1973, administered jointly by the
Consumer Products Safety Commission (CPSC), the
Department of Health and Human Services, and the
Department of Housing and Urban Development, regulates
the use of lead paint on toys, furniture, cooking,
drinking and eating utensils, and in federally-assisted
housing. CPSC has set a level of 0.06 percent lead in
household paints, and proposes to assess the use of lead
in printing inks, particularly on gift wrapping paper,
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colored newspaper and candy wrappers. EPA, CPSC, and
FDA have developed a voluntary industrial standard for
lead on decorated glassware.
The present standard for occupational exposure to
airborne lead is 200 micrograms of lead per cubic meter
of air (200ug/m3). In 1978, the Occupational Safety and
Health Administration issued a new workplace standard of
lOOug/m , but it is being challanged in the courts
In Summary; Increased amounts of lead in the
environment pose serious health hazards, especially to
children. The Federal government has taken several
steps to reduce the public's exposure to lead, and is
pursuing additional measures to further reduce the lead
risk in this country. There are more than 30
regulations currently which limit exposure to lead
directly or indirectly.
CHILDREN AT RISK
Children are of particular concern in consideration
of lead exposure and effects. Preschool children are
exposed to special hazards from environmental sources of
lead. Young children frequently lick, chew or actually
eat foreign objects. Lead-based paints have long been
considered the major source of excessive lead intake in
young children. The consumption of dirt contaminated
with lead and the inhalation of polluted air during
outdoor play may also contribute to the extra body
burden of lead in children.
Lead may also affect unborn children whose mothers
are exposed to high concentrations during their
pregnancies or who have high body burdens. Lead is
readily transferred across the placenta and the
concentration of lead in the blood of newborn children
will be similar to that of their mothers.
Not only are children exposed to additional sources
of lead, but they tend to be more susceptible to the
toxic effects of lead, exhibiting symptoms at lower
levels of exposure than adults. Children are more sen-
sitive to lead anemia than adults, and young children
may experience subtle neurological damage without ever
exhibiting classical signs of juvenile lead brain
damage, such as loss of motor skills and speech. Learn-
ing ability may be impaired due to motor incoordination,
lack of sensory perception or inability to concentrate A
reversible, acute kidney disease has been found to be
more prevalent in children at lower Pb-B levels than in
adults, also.
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