"...lead affects children’s brain development resulting in reduced intelligence quotient (IQ), behavioural changes such as reduced attention span and increased antisocial behaviour, and reduced educational attainment. Lead exposure also causes anaemia, hypertension, renal impairment, immunotoxicity and toxicity to the reproductive organs. The neurological and behavioural effects of lead are believed to be irreversible. "
http://www.who.int/mediacentre/factsheets/fs379/en/
Getting lead out of our environment is generally a good idea.
Lead is an actual poison.