I scoffed when I first heard about it, but then I read the article.
It's a bit of a long read, but fascinating and potentially very, very important.
Assuming that the studies it refers to are legit, then it is very compelling evidence that the dramatic rise in violent crime rates in the 60's, 70's and 80's and then the dramatic DROP in those same violent crime rates in the 90's and onwards is due to the increase in cars after WWII and all the leaded gasoline, and then the removal of lead from gasoline. It also means that America could potentially save hundreds of billions of dollars and reduce violent crime rate even further.
I know the first thing people will think: correlation, not causation. But apparently the correlation between removing lead from gasoline and violent crimes works city by city, state-by-state, and even nation-by-nation. These places removed lead from gas at different times, and of course they all had varying other factors, but removing the lead from gas still held up in the correlation with future drops in crime rates of a little over 20 years (the time it takes for a child to grow up and become a violent adult). In New Orleans they were even able to correlate lead levels in soils to violent crime rates to individual neighborhoods, and they matched up. Not only that, but every other theory (baby boom and it's echo, abortion and birth control availability, new policing methods, etc) does not correlate with the data showing the drop in violent crimes. Removing lead from gasoline goes correlate.
Not only that, but research shows that even small amounts of lead in the body leads to behaviors that we pretty much typify with more violent young people.
Hopefully more research will be done to follow up on this theory, because if true the USA and other countries could potentially reduce violent crimes, incarceration rates and costs, and help out their urban areas. It also makes you wonder about our problems with infertility, ADHD, autism, obesity, etc and whether or not there could be a simple answer based on certain kinds of environmental pollution.