Lead constitutes 0.002% of the Earth’s crust, and in nature it exists mainly as lead sulphide. Lead has become widely distributed in the biosphere
only in the past few thousand years, almost entirely as the result of human activity (National Research Council, 1972). Once lead is introduced into
the environment, it persists. The average person has less than 10 micrograms per deciliter, or 100 parts per billion, ppb, of lead in their blood.  People who have been exposed to an unusual amount of lead will have blood lead levels higher than 200 ppb—most clinical symptoms of lead poisoning begin at around 100 ppb. The effect on children's mental/cognitive abilities has been noted at very low levels.
Lead poisoning epidemiology and demographics
Alcohol withdrawal epidemiology and demographics
Hepatotoxicity epidemiology and demographics
Alcoholism epidemiology and demographics
Lead poisoning laboratory findings
Heat stroke epidemiology and demographics
Alcohol withdrawal diagnostic criteria
Alzheimer's disease epidemiology and demographics