NZ children’s exposure to lead linked to lower IQs, job prospects


New Zealand was much later than other nations in banning lead from petrol
New Zealand was much later than other nations in banning lead from petrol
Middle-aged Kiwis could have lower IQs and poorer job prospects because the country was slow to ban lead from petrol

Car and truck exhaust fumes from the era of leaded petrol could be to blame for some middle-aged Kiwis having lower IQs, job histories and social standing, according to research released today.

Researchers at the long-running, world-leading Dunedin Study project (see below) said high levels of lead in New Zealand cities in the 1970s and 1980s appeared to be responsible for a loss of intelligence and occupational standing among today’s adults.

New Zealand was 20 years later than other countries in removing lead additives from petrol – it was not outlawed until 1996 – and critics blame oil industry lobbyists, complicit politicians and uninformed bureaucrats for the ”tragedy”.

Until now, the long-term effects of lead exposure were unknown due to a lack of research, Dunedin Study associate director Professor Terrie Moffitt said.

“In the 1980s, the Dunedin Study, guided by Professor Phil Silva, was influential in making New Zealanders aware that lead might be harmful to children,” Moffitt said.

Just over half the 1000-plus study participants, born in 1972 or 1973, had a blood-lead test when they were 11. By the age of 38, those with more than 10 micrograms of lead per decilitre of blood had IQs more than 4 points lower than their peers with less lead.

The findings, published in the Journal of the American Medical Association today, suggest children exposed to high levels of lead in petrol ended up getting lower skilled jobs as a result

The same group also had lower IQs at age 38 than they did when they were children.

Moffitt said the data came from an era when high levels of lead were viewed as normal, and not dangerous, for children.

Lead is a powerful neurotoxin that can build up in children’s bloodstreams and settle into bones, teeth and soft tissue.

According to the research, the highest levels of lead particles were found in roadside soil, due to vehicles emitting lead-laden exhaust as they drove by.

Children playing outside near roads either inhaled lead-laden dust or swallowed small amounts of leaded soil.

“Lead exposure is very rare in Kiwi children today. But the findings suggest the importance of keeping up our vigilance against other environmental pollutants,” she said.


Unique and world-leading, the University of Otago Medical School has been following the lives of 1037 people born in Dunedin’s Queen Mary Hospital between April 1972 and 1973 in what’s officially called “the Dunedin Multidisciplinary Health & Development Study.”

The latest phase of research begins in April, when participants begin to turn 45.

Participants are interviewed and undergo a variety of tests every five years. This includes people who have since moved away from the city.

Most international studies for issues such as Alzheimer’s Disease begin with participants aged 50 and 60 and researchers have no information on their earlier experiences, diet, health, relationships, employment history etc.

The Dunedin Study has generated more than $NZ12.5m from overseas funding agencies which are keen to use its research.

It has yielded more than 1200 research articles, reports and books on topics such as child health, injury prevention, infertility and the links between drug abuse and adult psychosis.


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