Environmental lead linked to aggressive behaviour

Children who are exposed to higher levels of environmental lead are more likely in early adulthood to show increased aggressive behaviour and commit an assault that results in death, a new study led by Macquarie University researchers has found.

Lead exposure is known to increase impulsivity, and crimes of aggression are typically related to impulsive actions.

“The results indicate that measures need to be taken to lessen exposure to lead in areas where environmental air levels remain high, so as to avoid any long-term neurodevelopmental consequences,” said lead author Professor Mark Taylor.

In this study, the researchers investigated these relationships in Australian communities at suburb, state and national level.

To look at how air lead exposure levels in Australia during childhood were related to rates of assault 15–24 years later, the researchers first adjusted for socio-demographic factors that are also known to affect criminal behaviour, such as age, secondary school completion and household income.

They then compared the results among six NSW suburbs — and found that environmental lead level exposure during childhood was actually the strongest predictor of assault rates later in life.

“When comparing results between suburbs in New South Wales we found that for every additional microgram of lead in the air, assault rates 21 years later rose by 163 assaults per 100,000 persons,” said Professor Mark Taylor.

The analysis showed that concentrations of lead in the air accounted for 29.8% of the variance in assault rates seen 21 years after childhood exposure.

When looking at data at the state level, the findings were echoed in New South Wales and Victoria — the states with the largest populations and the highest population densities and petrol lead emissions. In these states, 34.6% and 32.6% of the variance in the rates of death by assault 18 years after exposure were revealed, respectively.

“While the correlation is weaker at state and national levels, there is still an observable correlation in the rate of assault,” said Professor Taylor.

“Overall, the data shows that at the more detailed suburb level, these relationships are very strong and are highly consistent even across different lead sources, social and demographic communities, and also time frames.”

The study, The relationship between atmospheric lead emissions and aggressive crime: an ecological study, was published in the Environmental Health journal.