Lead exposure causes one in three cardiovascular deaths

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Researchers in the USA monitored lead levels in more than 14,000 Americans over 20 years and found that even very low levels - between one to five micrograms of lead per decilitre of blood - increases the risk of premature death. Of those, 1,801 died from cardiovascular disease and 988 passed away from heart disease.

Compared with people having low levels of lead in their blood, those with high levels of at least 6.7 micrograms were twice as likely to die from ischaemic heart disease, a condition where the heart is starved of blood due to narrowed or block arteries.

The study concluded that almost 30 percent of all deaths due to cardiovascular disease - basically, heart attacks and strokes - "could be attributable to lead exposure".

The study found that lead is common in a variety of common items including fuel, paint and plumbing and can even be found in certain foods, emissions from industrial sources, and contamination from lead smelting sites and lead batteries.

"What this study suggests is there's no apparent safe level" for adults, said the principal author of the study, Bruce Lanphear of Simon Fraser University, in Canada.

Of environmental lead exposure, he said: "If we took that seriously, without knowing anything more about genetics, without any more expensive drugs, we could much more strategically reduce deaths from heart disease, which is pretty hopeful, actually".

Lanphear analyzed earlier USA government research from the National Health and Nutrition Examination Survey (NHANES). All were given a medical examination at the start of the study that included a blood test for lead, with readings ranging from less than 1mg per decilitre of blood to 56mg.

Researchers estimated that 28.7 per cent of cases of annual premature heart disease death in the United States could be attributed to lead - a total of 256,000 deaths per year.

Overall cardiovascular death risk was raised by 70 per cent by higher levels of lead exposure, the study found.

The study said "the estimated number of deaths from all causes and cardiovascular disease that were attributable to concentrations of lead in blood were surprisingly large; indeed, they were comparable with the number of deaths from current tobacco smoke exposure".

A similar study would need to be conducted in Australia to confirm the extent of the association between lead exposure and heart disease, Dr Harvey noted.

Professor Kevin McConway, Emeritus Professor of Applied Statistics at the Open University, said: "The researchers make a very important point in their report - that it is more accurate to view this study as estimating how many deaths might have been prevented if historical exposures to lead had not occurred".

"Our study calls into question the assumption that specific toxicants, like lead, have "safe levels", and suggests that low-level environmental lead exposure is a leading risk factor for premature death in the U.S., particularly from cardiovascular disease", Professor Lanphear said.

The authors controlled for other factors that might contribute to cardiovascular disease, such as smoking, excessive alcohol consumption, poor diet and lack of exercise.