Lead and The Environment


Some materials are so commonplace that we take them for granted. One of
those materials is a grayish metal that has been with us for thousands of years.
That metal is lead, still one of the world\'s most useful substances, and one
that never ceases to find a role in human society.

Lead has the atomic symbol of Pb (for plumbum, lead in Latin). The
atomic number for lead is 82 and the atomic mass is 207.19 AMU. It melts at
about 327.502 oC and boils at 1740 oC. Lead is a heavy, ductile, soft, gray
solid. It is soluble in nitric acid and insoluble in water. It is found in North,
Central and South America, Australia, Africa and Europe. In modern times, lead
has found a wide range of uses, and world demand for lead and its products has
steadily increased. Lead\'s usefulness stems from the metal\'s many desirable
properties: softness, high density, low melting point, ability to block
radiation, resistance to corrosion, readiness to form alloys and chemical
compounds, and ease of recycling. Its versatility, as well as its physical and
chemical properties, accounted for its extensive use. Lead can be rolled into
sheets which can be made into rods and pipes. It can also be molded into
containers and mixed with other metallic elements.

Lead was used in ancient times for making coinage, art objects and water
pipes. One of the first known toxic substances, lead was used by the Romans for
lining aqueducts and in glazes on containers used for food and wine storage; and
it is suspected to have resulted in widespread lead poisoning. Members of the
famous Franklin Expedition to the Northwest Passage in the mid-1840s met a
similar fate, being poisoned from lead in solder, widely used at the time to
seal tins used to store foods. Until recently, one of the most significant uses
was an anti-knock additive in gasoline. In the 1970s and 1980s, steps were taken
to reduce the use of leaded gas. By 1990, these actions had virtually eliminated
the use of lead in gasoline. Lead is also one of the best and earliest examples
of recycling about 55 percent of the lead used in Canada comes from recycled
material.

One particular category of toxic tort is injury caused by exposure to
lead-based paint. The hazards of lead-based paint have been known since the
early 1900s, when the use of lead in the manufacture of paint was banned in
Australia. The lead mining and lead pigment industries in the United States were
able, however, to forestall the banning the use of lead in the manufacture of
paint until 1978, when it (finally) became illegal in our nation. Lead poisoning
occurs only when too much lead accumulates in the body. Generally, lead
poisoning occurs slowly, resulting from the gradual accumulation of lead in the
bone and tissue after repeated exposures. However, it is important to note that
young children absorb 50% of a lead ingestion, while adults absorb only 10%.

The greatest risk of injury from lead poisoning is to children under the
age of seven, whose developing bodies and brains are sensitive to even small
amounts of lead, which can leave children with subtle but irreversible injury
that does not appear until many years after the exposure to lead. The kinds of
injuries lead causes in children include: learning disabilities, brain damage,
loss of IQ points and intellect, academic failure, neuropsychological deficits,
attention deficit disorder, hyperactive behavior, antisocial (criminal) behavior,
neurological problems, encephalopathy (brain swelling), major organ failure,
coma, and death. These injuries can be life-threatening or can prevent a child
from realizing his or her scholastic, vocational, and financial potential, or
from becoming a self-sufficient adult.

To confirm lead poisoning, the best test is a venous blood lead level.
If the blood lead level is below 25 g/dL, then a serum ferritin level and other
iron studies can be used to determine if iron deficiency anemia exists. With an
elevated blood lead level of 50 ug/dL, the conclusion is that the boy is lead-
poisoned. In this case, the child should be referred for appropriate chelation
therapy immediately.

One particular category of toxic tort is injury caused by exposure to
lead-based paint. The hazards of lead-based paint have been known since the
early 1900s, when the use of lead in the manufacture of paint was banned in
Australia. The lead mining and lead pigment industries in the United States were
able, however, to forestall the banning the use of lead in the manufacture of
paint until 1978, when it (finally) became illegal in our nation. Lead