In tissues, lead behaves like other heavy-metal poisons. When lead ions are bound to an enzyme, the enzyme will likely cease to function. The principal sources of lead contamination now seem to be lead-based painted surfaces in old buildings and soldered joints in plumbing systems. The phasing out of leaded gasoline has resulted in a drastic drop in average lead blood levels. Mild formsof lead poisoning produce nervousness and mental depression.
More severe cases can lead to permanent nerve, brain, and kidney damage.