File photo: Published in The Lancet, the paper pointed the finger at fine particles of soot and dust, emissions of which are also stirring a health scare in parts of Asia, especially China.

London - A fall in the amount of lead in the atmosphere could explain a sharp decline in violent crime, researchers suggest.

Scientists found that cities where lead pollution was reduced experienced falling levels of robbery and violent crime around 20 years later.

Similarly, an increase in lead pollution prompted an increase in violence two decades later.

Researchers believe that exposure to toxic lead in the environment damages children’s brains and could make them more likely to commit violent crime when they grow up.

Lead has been shown to damage the brain, reducing IQ and affecting concentration levels.

US research looked at differences in children’s behaviour who were highly exposed to lead at a young age.

Separate studies found a statistical correlation between lead levels and violence in Chicago, Minneapolis, San Diego and other US cities.

Many cities in the US removed lead from petrol in the mid-1970s and from paint a decade earlier.

Violent crime began to fall in the 1990s and has continued to fall since.

But cities where lead levels remained high continued to experience higher levels of crime.

Researchers took other causes such as social, economic and legal factors into account, including drug use, poverty, policing effort and incarceration rates.

Professor Howard Mielke, of Tulane University in New Orleans, who has studied the effect of lead on children, said there was a “strong association” between criminal activity and lead in different parts of the city.

He told Radio 4’s Today programme: “The amount of lead in the environment... was particularly strongly related to both learning problems and then violence.”

Professor Mielke said police were even using the data on lead to target specific areas of New Orleans where they expected crime to be higher.

This would allow them to target resources at particular crime hot spots where lead poisoning had been higher in the past. Dr Alastair Hay, Professor of Environmental Toxicology at Leeds University said: “We know that lead exposure in children and infants, when the brain is developing, damages the brain, and we know that children who are exposed to lead have a lower IQ.

“These children tend to be more impulsive and find it more difficult to concentrate. What these studies are saying is that following exposure in infancy – the effect on the body seems to pre-dispose or is certainly strongly linked with violent behaviour in adulthood.”

Dr David Green, director of the Civitas think-tank, said environmental lead could be a factor in explaining the dramatic surge in crime in England and Wales in the late 80s, which peaked in 1993 – and the fall in crime in recent years.

“I would have expected to see a larger increase in crime with fewer police, particularly crimes which are influenced by having police on the streets such as violent punch-ups,” he added.

Across the Western world, crime rose from the mid-20th century before peaking in the early 90s and then falling back sharply.

Previous explanations for this change include decline in the use of crack cocaine, the rise of zero-tolerance policing and even the legalisation of abortion. - Daily Mail