A new study claims to have found a link between the high murder rates and the use of lead water pipes in some US cities. Scientists at Harvard and the University of California, Berkeley analysed homicide rates and the cities' use of lead pipes from 1921 and 1936.

Although the use of lead pipes was halted in the UK in 1970, many cities in the US still have lead pipes. Most notably in Flint, Michigan, where the lead contamination of the impoverished city's water supply has resulted in citizens filing a lawsuit against two Michigan State officials and an official at the City of Flint.

The lawsuit lists a number of health problems suffered by residents because of the "toxic" levels of lead which are up to 10 times the average. They include skin lesions, hair loss, high levels of lead in the blood, vision loss, memory loss, depression and anxiety.

The study was published by James J Feigenbaum of Harvard and Christopher Muller of the University of California, Berkeley in the journal Explorations in Economic History. It says that on average "cities that used lead water pipes had homicide rates that were twenty-four per cent higher than cities that did not".

Previous studies have said that the use of lead can lead to lower IQs amongst children and higher rates of violent crime after people were exposed to lead in air pollution. The report added that the acidity levels in the water can also change how much lead is dissolved in it — and how much is ingested.

The paper says: "Even if lead removal will not reduce crime, it will remove a dangerous toxin from the environment. Other strategies to reduce crime may not have similarly positive side effects.

"We found evidence broadly consistent with the prediction that more lead will leach into more acidic water and increase the homicide rates of cities with low-pH water and lead service pipes,"

The authors of the report do add that the link between lead and crime still needs to be researched. But despite further studies needing to take place they recommend the removal of all lead pipes from water systems.