Crime of the century
Copley News Service

Some people think crime declined during the 1990s because of aggressive police work, tough sentencing guidelines and the construction of more prison cells.

But some scientists now have a more provocative explanation: They say crime may have declined in the 1990s because lead was removed from gasoline 20 years earlier.

The link between lead exposure and criminal behavior isn't as far-fetched as you might think. It was first noted as far back as 1943.

A new study, published last month in the medical journal PLoS Medicine, makes the strongest case to date for a relationship between childhood lead exposure and adult crime. Beginning in 1979, researchers in Cincinnati followed 250 people from birth to young adulthood. They found that prenatal and childhood exposure to lead was a strong predictor of future arrests, particularly arrests for violent crime.

The greater the exposure, researchers found, the stronger the association. That kind of proportional relationship is something scientists look for when trying to establish cause and effect. But the link between lead levels and violence was noted even in children with blood lead levels below what's considered poisoned - 10 micrograms per deciliter of blood.

Early exposure to lead is associated with lower IQ, less tolerance for frustration, hyperactivity and poor impulse control. Lead interferes with brain development in children and lowers levels of key neurotransmitters. Brain damage has been found at the lowest levels that can be monitored. Once that damage occurs, it is irreversible.

Last year, economist Jessica Wolpaw Reyes published research showing that the rise and fall of lead exposure rates among American children seems to match the rise and fall of violent crime - but with a 20 year time lag. That makes sense, because people in their late teens and early 20s statistically are more likely to commit crimes.

Today, lead paint is the cause of most childhood lead exposure. But before the switch to unleaded gasoline between 1975 and 1985, lead in gas was the primary source. Reyes used small variations in the lead content of gasoline from state to state to strengthen her conclusions.

If she's correct, the same effect should be found in other countries. That's exactly what researcher Rick Nevin found in an international study published in 2006.

Countries like Britain and Australia, which switched to unleaded gasoline only in the 1980s, are only just beginning to see a drop in violent crime rates, Nevin's study found. He tracked violent crime and lead content in gasoline in nine countries.

For much of the 19th and 20th centuries, children were exposed to high lead levels because no one knew the damage it was inflicting. That's a tragedy.

Today, we know better. Allowing it to continue is worse than tragedy, it's a crime.

Reprinted from the St. Louis Post-Dispatch.