Lead's one of the most ancient toxins known to humanity.
It's even blamed for bringing down the Roman Empire by leaching into drinking water and poisoning the leadership.
Now, 1,500 years later, lead in water has sparked a national state of emergency in Flint, Michigan. Officials there are accused of ignoring an ongoing problem that sent lead coursing into the water supply serving 99,000 people, including pregnant women and young children.
Here are some of the health effects that lead's known to cause:
Developmental delay and learning difficulties
Unborn babies and very young children are most vulnerable to the effects of lead. The heavy metal destroys nerve cells, including developing brain tissue. One team of researchers found in 2008 that exposure to lead might even cause criminal behavior. These effects cannot be reversed.
Loss of appetite and weight loss
Kids stop thriving, stop eating, and not only become too thin but feel tired from the effects. Babies exposed to lead don't grow at normal rates.
Vomiting and stomach pain
Lead poisoning usually causes subtle, long-term effects but acute lead poisoning can cause vomiting, stomach pain and constipation. Treatment called chelation therapy can pull high levels of lead from the blood but cannot reverse damage that's already occurred.
High blood pressure
Lead's most dangerous to children but high doses can raise blood pressure in adults, damage the kidneys, cause numbness in the fingers and toes and joint pain, too.
In adults, lead can cause brain damage that affects memory and causes mood disorders.
Lead can cause sperm to become abnormal and can cause miscarriages.
Sources of lead:
Lead pipes, copper pipes soldered with lead and brass plumbing fixtures soldered with lead can release lead into tap water. This has happened more than once when changes in disinfection or the release of corrosive chemicals into a city's water supply breaks down coatings inside pipes and releases lead.
Lead-based paints have been banned for use in homes, toys and household furniture since 1978 but lead-based paint remains in many older homes and can flake off. Kids can chew the paint chips or ingest the dust and get lead poisoning.The centers for Disease Control and Prevention estimates that 24 million U.S. homes contain deteriorated lead-based pain that can flake off.
Some older pottery glazes contain lead and it can get into food.
Many traditional remedies contain lead. Some notorious sources include babawsan, a Chinese remedy used to soothe fussy babies; ghasard, used as a tonic in India and azarcon, a Hispanic remedy for stomach upset and teething babies.