A new study is bringing attention to a potential link between lead exposure and violent behaviour.
The base metal element lead, Pb, or more specifically, the lead-based chemical compound Pb(CH2CH3)4, was part of data from 90 US cities since the 1950s for researchers at the University of Tulane, New Orleans, who found that violent crimes rates mirrored lead emissions.
Researchers said violent crimes rose sharply around 20 years after the introduction of leaded gasoline and began to fall the same interval after it was phased out in the 1970s.
Lead can commonly be found in everyday items like pencils and lipstick. Also, it can be found in contaminated soils.
The US Environmental Protection Agency advises that any contact with the toxic element is dangerous.
The violence link is supported by a 2007 academic study which found close ties between lead and crime levels in 14 nations across the world. The study said children exposed to lead were more often arrested for violent crimes and "demonstrated association between developmental exposure to lead and adult criminal behavior."