Many Western nations have experienced significant declines in crime in recent decades, but could the removal of lead from petrol explain that?
Working away in his laboratory in 1921, Thomas Midgley wanted to fuel a brighter tomorrow. He created tetraethyl lead – a compound that would make car engines more efficient than ever.
But did the lead that we added to our petrol do something so much worse? Was it the cause of a decades-long crime wave that is only now abating as the poisonous element is removed from our environment?
For most of the 20th Century crime rose and rose and rose. Every time a new home secretary took office in the UK – or their equivalents in justice and interior ministries elsewhere – officials would show them graphs and mumble apologetically that there was nothing they could do to stop crime rising.
Then, about 20 years ago, the trend reversed – and all the broad measures of key crimes have been falling ever since.
Offending has fallen in nations whose governments have implemented completely different policies to their neighbours.
If your nation locks up more criminals than the average, crime has fallen. If it locks up fewer… crime has fallen. Nobody seems to know for sure why.
But there are some people that believe the removal of lead from petrol was a key factor.
Lead can be absorbed into bones, teeth and blood. It causes kidney damage, inhibits body growth, causes abdominal pain, anaemia and can damage the nervous system. More than a century ago, a royal commission recommended to British ministers that women shouldn’t work in lead-related industry because of damage to their reproductive organs.
By the 1970s, studies showed that children could even be poisoned by chewing fingernails harbouring tiny flecks of old leaded paint from their homes and schools.
Studies have shown that exposure to lead during pregnancy reduces the head circumference of infants. In children and adults, it causes headaches, inhibits IQ and can lead to aggressive or dysfunctional behaviour.
If you want to understand the causes of crime – and be tough on them – you need to start with lead, says Dr Bernard Gesch, a physiologist at Oxford University who has studied the effect of diet and other environmental factors on criminals.