Researchers at the World Bank claim that lead in drinking water is responsible for more heart disease than smoking or bad diets.

Using blood tests from thousands of adults in 183 countries, they simulated the number of deaths from heart disease caused by lead — with their model saying 5.5million were caused by the heavy metal.

For comparison, smoking was linked to two million deaths from heart disease worldwide, while high cholesterol contributes to 2.6million.

Researchers based in Washington D.C. said their study was a ‘wake-up call’ to get lead out of the water supply, with 56 percent of Americans still drinking water contaminated with the heavy metal.

• The above map from pressure group the Natural Resources Defense Council (NRDC) shows populations served by drinking water with the highest levels of lead contamination. Florida had the highest concentration of lead piping, a separate study showed

• The above shows the number of lead service lines per state. A service line is a pipe that connects a home to the water mains. Every house has one

Heart disease is the leading cause of death globally, behind an estimated 8.9million deaths in 2019 alone.

It is also the leading cause of death in the US, according to the Centers for Disease Control and Prevention (CDC), behind 695,000 deaths per year.

Lead is an extremely toxic heavy metal that can accumulate in the body over time leading to a range of heart problems.

Florida has the most lead water pipes in the nation 

Even low exposures of the material to children could lead to brain damage and learning disabilities.

In babies and small children, it can also cause damage to the brain and central nervous system leading to language and speech problems and developmental delays.

The heavy metal leaches into drinking water from pipes made out of the heavy metal that are still in use in many countries, including the US.

These are mostly service pipes, or those connecting houses to the water mains, with the Biden Administration having unveiled a fund of $45billion to tackle the problem.

Houses in Florida are most likely to have a lead service pipe, studies suggeset, followed by those in Illinois and Ohio.

Lead causes heart disease by triggering high blood pressure, which happens because as the heavy metal builds up in the body it causes blood vessels to constrict reducing the amount of space blood has to flow through.

The metal can also cause this by damaging the kidneys, which can reduce blood pressure by filtering water and nutrients out of the bloodstream.

Lead is also known to cause arrhythmias, or an abnormal heartbeat, by interfering with nerves.

High blood pressure leads to heart disease by forcing the heart to work harder and raising the risk of damage to arteries, which can cause fatty plaques to build up.

For the study, published in Lancet Planetary Health, researchers looked at data from the Global Burden of Diseases (GBD) study published in 2019.

Previous research has only estimated deaths from lead exposure using figures on the number of adults suffering from high blood pressure.

But in this study, the researchers used a model that took into account other impacts that lead has on the heart — such as arrhythmias.

Results showed that ninety percent of deaths linked to lead exposure were in developing countries.

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  The above shows the leading causes of death globally in 2019, according to the World Health Organization

They also found children in developing countries were losing an average of six IQ points to damage from lead exposure.

This was six times higher than the previous figure and estimated to be costing the world $6trillion a year.

Environmental economist Bjorn Larsen who co-authored the study said that when they first saw the number it was so ‘enormous’ they ‘didn’t even dare whisper it’.

Campaigners described the study’s findings as a ‘wake-up call’ to the world to take action over lead exposure.

Richard Fuller, the president of Pure Earth, said the results suggested the impacts of lead may be even worse than first feared.

But experts — such as air pollution scientist Dr Roy Harrison from the University of Birmingham, UK — sought to pour cold water on the findings.

He said the results were ‘interesting’ but remained ‘subject to many uncertainties’.

He pointed out that the relationship between lead in blood and heart disease that the model used was based on a survey conducted in the United States, but that applying this to the whole world was a ‘huge leap of faith’.

The Natural Resources Defense Council — a US-based pressure group — estimated that between 2018 and 2020 56 percent of Americans drank from water systems with detectable levels of lead.