One of the best things to happen to cities and societies in the last 20 years is the dramatic decline of crime. Canada has reported one of the lowest crime rates since the 1970s. New York City, North America’s second largest city, reported the lowest homicide rate since police began tracking in 1963. The decline in crime also supports the strong growth of downtown living, which is losing it’s stigma as a dangerous place to live.
Why has crime declined so dramatically across North American cities? Mother Jones has a piece that argues convincingly that “gasoline lead is responsible for a good share of the rise and fall of violent crime over the past half century.” In the 1940s most Americans and Canadians began to use leaded gasoline to improve engine performance. This resulted in a huge increase of lead in the atmosphere. In every country, state and city where lead was banned, 23 years later crime would decline. No exceptions.
There is even evidence that large cities had higher crime rates than smaller cities because there were more cars and hence a higher concentration of lead in the atmosphere. In fact, since leaded gasoline was banned, big cities have become just as safe as small cities. The idea that bigger cities have more crime is now a myth.
How could lead exposure lead to a prolonged thirty year crime wave? As Kevin Drum writes “even moderately high levels of lead exposure are associated with aggressivity, impulsivity, ADHD, and lower IQ. And right there, you’ve practically defined the profile of a violent young offender.”
Now that we are preventing the release of lead through tailpipes, we need to focus on cleaning up all that lead that is in our soil and homes. As more people move into city centres, where lead concentrations remain the highest, this is becoming even more important. Measuring lead concentration in soil is easy. More cities should study, prepare and report on where the lead exists and make plans to remove it.