Lead poisoning





Lead poisoning is a condition caused by increased levels of blood serum lead
levels. The average person has less than 10 micrograms per decaliter, or 10
parts per million, ppm, of lead in their blood serum. People who have been
exposed to an unusual amount of lead will have lead serum levels higher than
20 ppm - most clincal symptoms of lead poisoning begin at around 100 ppm.
The symptoms of lead poisning include reduced IQ and, in extreme cases, seizure.

Outside of occupational hazards, the majority of lead poisoning occurs in
children under age twelve. The main sources of poisoning are ingestion of
lead contaminated soil (this is less of a problem in countries that no
longer have leaded gasoline) and lead based paints. This is particlularly a
problem in older houses where the sweet tasting lead paint is likely to chip.

Once in the body, lead is biologically inactive – its toxic properties
come from lead's ability to mimic other biologicaly important metals, the
most notable of which are iron or zinc. Lead is able to bind to and interact
with the same proteins and molecules as iron, but after replacing iron,
those molecules function differently and fail to carry out the same reactions.

Most lead poisoning syptoms are thought to occur by interfering with an
essential enzyme Delta-aminolevulinic acid dehydratase, or ALAD. ALAD is a
zinc binding protein which is important in the biosynthesis of heme, the
cofactor found in hemoglobin. Genetic mutations of ALAD cause the disease
porphyria, a disease which was highlighted in the movie The Madness of King George.