How leaded gasoline could be linked to crime rates
Published Thursday, March 7, 2013 9:31AM EST
There have been many theories about what causes spikes in violent crime, including everything from drug use, to social cuts, to changes in the justice system. But could the answer be in the polluted air we breathe?
Economist Rick Nevin has a theory that the rise and fall of the use of lead in gasoline can account for rising and falling rates of violent crime both in Canada and countries all around the world.
His theory has been met with its fair share of skepticism; with “correlation does not mean causation” being the typical response. But his theory is nevertheless an intriguing one. Nevin proposes that after the Second World War, there was a sudden surge of cars on the road, all using leaded gasoline. Then, about 20 years later, around the mid-1960’s, countries in Europe and North America experienced spikes in rates of violent crime.
When leaded gasoline started to be phased out in the 1970s, crime rates began a sharp decline about 20 years later, when the children born as unleaded gas became the norm reached adulthood.
Nevin has been trying to bring his theory to the fore for some time now, but admits his first paper, published in the journal Environmental Research, has been largely ignored. But Nevin says he has found the same link between leaded gas and crime rates in nine separate countries, with the correlation remaining strong in each of them.
Now, thanks in part to an article in Mother Jones magazine earlier this year, Nevin is pleased to see that many are starting to give the theory a second look.
“When my first study was published in 2000, it looked just as the U.S. and that, to be honest, was widely ignored even though the relationship was extremely strong,” Nevin told CTV’s Canada AM Thursday from Washington.
“In 2007, I published my analysis that showed the same relationship in nine nations and that has received a little bit more attention.”
The biological explanation for Nevin’s theory makes sense. It’s widely known that lead exposure can seriously affect brain development. The metal has been linked to lower IQ and difficulty managing aggression, and difficulty with decision-making.
Nevin proposes that children pick up the lead from both leaded gasoline and leaded paint by coming into contact with contaminated dust.
“Children, through normal hand-to-mouth activity when they’re crawling, pick up this lead-contaminated dust that’s settled from gasoline lead,” he says.
“That enters their bloodstream in that first year of life when their brains are in a critical stage of development.”
Then, about 20 years later, rates of property crimes and violent crime start to peak. Nevin says these patterns hold not only at the national level, but even at regional levels: increases in lead relate to increases in crime, while decreases in lead relate to later decreases in crime.
“In every single country that I’ve looked at, we see exactly the same pattern,” he says.
U.S. and Canada experienced much earlier rises in crime rates that Europe, Nevin proposes, because our continent used a disproportionate share of gas after the Second World War compared to Europe, which was still recovering from the war and therefore had fewer cars on the road.
Likewise, the U.S. and Canada started to reduce the use of tetraethyl lead in their gas in the 1970s, while Europe kept their’s high for longer. As a result he says, our crime rates fallen ever since much quicker than Europe’s.
“My analysis shows that from 1962-2002, the rise and fall of lead emissions from gasoline and the associated rise and fall of in children’s blood lead levels explain about 80 to 90 per cent of the variation across those four decades in Canadian crime rates,” Nevin says.
What’s more, he says, crime rates since his 2002 study was published have continued to fall, just as he predicted.
“I think what is finally forcing people to take a more serious look at this is that I now have eight, nine, 10 years of data after the analysis after 2002,” he says, “and the crime rates in every country are falling into place more or less exactly where the earlier lead exposure rates anticipated that they would.”