|
Most know that violent crime skyrocketed in the '60s and '70s. But what's puzzled researchers for more than a decade is why, starting in the early '90s, crime rates began dropping. Criminologists have credited everything from three-strikes laws to improved policing tactics. But as crime continued to drop throughout the U.S.—and Canada, France, New Zealand, and the rest of the world—it has led to speculation that there might be an environmental cause. For decades, lead (chemical symbol: Pb) has been linked to impaired brain development in children. However, new medical studies show that lead does more than degrade IQ and learning ability; it also hits areas of the prefrontal cortex that control aggression, emotion regulation, and impulse control. Degradation in these areas practically defines the profile of a violent young offender. Beginning after World War II, the most prominent source of lead exposure was tetraethyl lead, the key anti-knock ingredient in "ethyl" gasoline. During the postwar economic boom, fuel usage skyrocketed. New cars flew off dealer lots and high-octane ethyl sold for a quarter a gallon. Where did all the lead that spewed from millions of tailpipes end up? According to researchers like Jessica Wolpaw Reyes, a public health professor at Amherst College who published a study on the effects of childhood lead exposure, a significant amount of it was absorbed into the bloodstreams of children.
Fast-forward two decades, she says, and an entire lead-poisoned generation began to come of age. Some suffered little more than the loss of a few IQ points, but others—mostly those at higher risk of developing criminal tendencies to begin with—were pushed over the edge into lives of violence, which triggered the beginning of the crime wave in the mid-1960s. Lead exposure hit its zenith then, as measures to reduce pollution—such as the advent of the EPA and the widespread deployment of the catalytic converter—began a transition to unleaded gas. The unintended but beneficial consequence was that kids started growing up with lower levels of lead in their bodies. As adults, they no longer exhibited artificially heightened violent tendencies. And crime rates began falling in the '90s. But can this correlation between environmental lead levels and crime statistics prove causation? This is where the case against ethyl becomes a lead-pipe cinch: Different countries and states banned leaded gasoline at different times. Reyes and other researchers have found that every last one experienced a crime decline that mirrored its lead decline, beginning about 20 years after the phase out of leaded gas commenced. Howard Mielke, a research professor at Tulane University, even found correlations between crime rates and soil-lead levels at the neighborhood level in New Orleans. The good news is that the EPA banned leaded gasoline in on-road vehicles in 1996 following a 1973–1986 phase-down. By 1995, leaded fuel accounted for only 0.6 percent of total gasoline sales, and today it's been restricted to off-highway use. The not-so-good news is the residue left behind by decades of burning it. Plenty of lead remains in our soil, especially in cities where emissions were densest. Every construction site or drought kicks it up. Cleaning up contaminated soil won't be cheap, but the social payoff could be tremendous. A longer version of this article appeared in the January/February issue of MOTHER JONES  from Car and Driver Blog http://blog.caranddriver.com | |||
| | |||
| | |||
|
No comments:
Post a Comment