New research suggests that childhood exposure to lead could be linked to life-long mental health problems.
Using information from Otago University's Dunedin Study, research led by Duke University in the United States found that children with higher levels of lead in their blood were more likely to develop mental health issues and difficult personality traits.
It also found that childhood exposure to lead was associated with lower IQ, behavioural issues, hyperactivity and antisocial behaviour.
The Dunedin Study followed more than 1000 children from 11 years old who are now 38 years old and who grew up around leaded petrol.
Dunedin Study director Richie Poulton said lead exposure levels in New Zealand were much lower now than they were when the study participants were children.
He said while there may be a very small risk to mental health in adulthood following high levels of exposure to lead during childhood, the study needs to be replicated before more concrete conclusions can be drawn.