There have been concerns about the health effects of lead in lead smelting towns such as Port Pirie in South Australia, but a new study has looked at the link between lead exposure and violent crime.

In an Australian-first study, researchers from Macquarie University in Sydney tested the link between environmental lead and violent crime by examining air samples from six NSW suburbs — Lane Cove, Rydalmere, Rozelle, Earlwood, Port Kembla and Boolaroo — over 30 years.

They then looked at crime data to see if exposure during childhood was related to rates of assault 15-24 years later.

And when they took into account other factors that contributed to criminal behaviour, such as education levels and household income, the researchers found that lead in air concentrations accounted for 29.8 per cent of the variance in assault rates 21 years later in those six suburbs.

They concluded there was a strong positive relationship between lead in air levels and subsequent crime rates, which had important implications for public health in Australia and globally.

“That is a massive amount — it’s about a third,” lead author Mark Taylor, a professor of environmental science, told news.com.au.

“The results are really robust because we relied not only on data that we’ve collected personally, but data that we’ve mined from various government sources and archives.

“It’s the first time anybody’s done this at this scale and with this amount of detail.”

Prof Taylor said the study, which was published in the journal Environmental Health, built on existing evidence that lead exposure increased impulsivity.

“We know that lead affects the brain in that it reduces the size of the frontal cortex, and damage to the frontal cortex is associated with decision making and in increase in impulsivity, which then is associated with crimes of aggression,” he said.

So the researchers looked at crime statistics related to aggressive crimes such as assault, domestic assault and assault of police.

But they also looked at fraud — a non-aggressive and non-impulsive crime — as a discriminate variable.

Cars are one of three historic causes of lead exposure among Australians.Source:News Limited

“Fraud, by contrast, is a premeditated crime and it showed no relationship, or a very weak relationship, to the variation of lead in air,” Prof Taylor said.

“So we could see that the rise and fall in assault rates associated very strongly, taking into account social demographic variables, to the rise and fall of lead in air.”

Lead paint, leaded petrol and mining and smelting emissions have historically been the three most dominant sources of lead exposure in Australia.

The study found that car emissions were responsible for lead in air at Earlwood, Rozelle, Lane Cove and Rydalmere, but in Port Kembla and Boolaroo, it was from local smelting operations.

“So when you look at the data, you can see that Port Kembla and Boolaroo have very high lead in air rates and also very high assault rates,” Prof Taylor said.

“The lead in air is much greater in concentration than the metropolitan suburbs, because the source is much more significant — that is, it’s coming from smelters.”

The study was also carried out on state and national levels. Researchers found similarly strong positive correlation between petrol lead emissions and death by assault rates in NSW and Victoria, the two most densely populated states with the highest petrol emission rates.

“The study showed quite clearly that for every 2000 additional tonnes of lead emitted in NSW, that was associated with one additional death. That is very significant for the person who suffered that consequence,” Prof Taylor said.

While the Macquarie University study does not definitively prove lead exposure can also lead to violent behaviour, including violent crimes, it has long been linked to health and development problems.

Australian health authorities say lead exposure is on the decline, largely due to the restriction of lead in petrol, paint, toys and cosmetics, but there have been serious concerns about toxic metal contamination in lead smelting and mining towns such as Port Pirie in South Australia, Mount Isa in Queensland and Broken Hill in NSW.

Prof Taylor believes lowering lead exposure would be generally beneficial in all cases.

“What this [report] tells us is that we need to be more cognisant about the emissions of newer toxic metal to the environment because of the consequences for later life,” Prof Taylor said.

“We know that there are significant consequences for early childhood development, that’s well established.

“The emerging paradigm is that there are significant and life long consequences from early life exposure to toxic metal — lead being one of them — and if we’re to apply an appropriate cautionary approach to protect the children, we need to perhaps revisit the appropriate standards for lead in air, lead in soil, along with other [toxic] metals, in order to make sure our children are not adversely affected as they grow into adulthood.”