Lead
Lead is a lustrous, silvery
metal that tarnishes in the presence of air and becomes a dull bluish
gray. Soft and flexible, it has a low melting point (327 °C). Its chemical
symbol, Pb, is from plumbum, the Latin word for waterworks, because of
lead's extensive use in ancient water pipes. Itsatomic number is 82; its
atomic weight is 207.19.
Lead and lead compounds can be highly toxic
When eaten or inhaled. Although lead is absorbed very slowly into the
Body, its rate of excretion is even slower. Thus, with constant exposure,
Lead accumulates gradually in the body. It is absorbed by the red blood
Cells and circulated through the body where it becomes concentrated in
The soft tissues, especially the liver and kidneys. Lead can cause damage
In the central nervous system and apparently can damage the cells making
Up the blood-brain barrier that protects the brain from many harmful chemicals.
Symptoms
Of lead poisoning include loss of appetite, weakness, anemia, vomiting,
And convulsions, sometimes leading to permanent brain damage or death.
Children who ingest chips of old, lead-containing paint or are exposed
To dust from the deterioration of such paint may exhibit symptoms. Levels
Of environmental lead considered nontoxic may also be involved in increased
Hypertension in a significant number of persons, according to studies
Released in the mid-1980s. As a result, the U.S. Centers for Disease Control
In recent years have been revising downward the levels of environmental
Lead that it would consider safe. At one time, lead poisoning was common
Among those who worked with lead, but such workplace hazards have been
Largely curtailed.
Lead has been used by humans since ancient times.
It was used in ancient Egypt in coins, weights,
Ornaments, utensils,
Ceramic glazes, and solder. Lead is mentioned in the Old Testament. The
Romans conveyed drinking water in lead pipes, some of which are still in...