A US study has shown the dramatic connection between atmosphere lead levels and violent crimes in later life. Mining communities that deal with high ‘air lead’ levels are likely to produce populations in later life who commit impulsive acts of crime and participate in violent behaviour the study finds. Children exposed to high lead levels also have increased participation injuvenile delinquency.
In the study, researchers compared the rates of ‘air lead’ pollution in six US cities from 1950 onwards with the levels of reported violent assaults in those same cities 22 years later.
The idea was to see if exposure to lead in early childhood had an effect on the propensity for people to commit violent and impulsive crimes later in life.
A strong correlation emerged from the data and Mark Taylor, Professor of Environmental Science at Macquarie University, says this research has implications for Australian communities, such as Broken Hill, that are dealing with high levels of lead exposure.
Professor Taylor says there is little surprise that a link was found between lead exposure in youth and violent assaults in early adult life, because of information found in previous studies, but the strength of the correlation was surprisingly high.
“(The researchers) were able to show that 90 per cent of the changes in the aggravated assault rate both in time and place… was explained by the rise and fall of air lead,” he said.
“Exposure to lead causes depressed IQ and lead poisoned children have profound impulse control problems and increased rates of juvenile delinquency.”
“When the correlation is so strong between the calculated atmospheric lead concentrations and the crime related outcomes in early adults it becomes very difficult to find alternative explanations.”
Studies of this nature haven’t been undertaken in Australia before but Professor Taylor says there is no reason to expect different results in this country and it would be valuable research.
“It hasn’t been done, it’s an interesting area and I think the fact that we make so much money from mining and the fact that we know that lead exposure is a serious problem (means) it warrants investigation.
The strong correlation between the increase and decrease of aggravated assaults with the rise and fall of lead air levels 22 years earlier was uniform across the six cities and throughout the 30 years of the study.
“They found from their study that for every metric ton of lead released 22 years previous, there was an increase of 1.5 aggravated assaults per 100,000 (people) that were reported,” Professor Taylor says.
If we apply those figures to Broken Hill by looking at the amount of air lead released into the city’s atmosphere in the 2010/11 reporting year (which was 11 tons), combined with the city’s population size of 20,000 people, it could be projected that around 3 more violent assaults will be reported in Broken Hill during the year 2033 than if zero lead pollution had been released over the same period.
Professor Taylor says the considerable sample size of the study, as well as the significant length of time from which the data was drawn, means the consistency of the high correlation between the lead exposure and reported violent assaults deserves to be further investigated.
Taylor also says more investigation is needed because of the study’s restrictions.
“(The study’s authors) note that there are some limitations to this study and those limitations are issues such as migration behaviour and, within the city, spatial variation lead exposure that would add uncertainty to the results.
“(But), even taking those into account, they still found that the correlation was really strong.”