Lead exposure may be 'leading risk factor' for premature heart disease death
Low-level lead exposure from petrol, paint and old plumbing may be causing hundreds of thousands of premature deaths, a US study suggests.
Scientists estimated that each year 256,000 Americans die from heart disease due to traces of the toxic metal in the environment.
Lead was added to petrol until the 1990s to boost engine compression. Similarly, lead was once widely used to improve the performance of household paint before being banned in the US in 1978 and the EU in 1992.
Lead pipes, once extensively used in plumbing, can still be found in older properties.
Industrial emissions and contamination from lead smelting sites and batteries mean that some level of exposure to the metal continues.
Lead exposure is linked to high blood pressure, hardening of the arteries and coronary heart disease.
Lead researcher Professor Bruce Lanphear, from Simon Fraser University in Canada, said: "Our study estimates the impact of historical lead exposure on adults currently aged 44 years old or over in the USA, whose exposure to lead occurred in the years before the study began.
"Today, lead exposure is much lower because of regulations banning the use of lead in petrol, paints and other consumer products, so the number of deaths from lead exposure will be lower in younger generations. Still, lead represents a leading cause of disease and death, and it is important to continue our efforts to reduce environmental lead exposure."
The scientists analysed data from the Third Health and Nutrition Examination Survey (NHANES-III), a major study monitoring the health of US citizens.
Around 14,300 participants were followed for almost 20 years. All were given a medical examination at the start of the study that included a blood test for lead.
Lead readings ranged from less than one microgram per decilitre of blood to 56 micrograms.
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. The condition is caused by the heart's pumping muscle being starved of blood due to narrowed or blocked arteries.
Overall cardiovascular death risk was raised by 70% by higher levels of lead exposure, the study found.
Extrapolating the results, the researchers estimated that 28.7% of cases of annual premature heart disease death in the US could be attributed to lead - a total of 256,000 deaths per year.
The findings are reported in The Lancet Public Health journal.
Prof Lanphear added: "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 USA, particularly from cardiovascular disease.
"Estimating the contribution of low-level lead exposure is essential to understanding trends in cardiovascular disease mortality and developing comprehensive strategies to prevent cardiovascular disease.
"Currently, low levels of lead exposure are an important, but largely ignored risk factor for deaths from cardiovascular disease. Public health measures, such as abating older housing, phasing out lead-containing jet fuels, replacing lead-plumbing lines, and reducing emissions from smelters and lead battery facilities, will be vital to prevent lead exposure."
Tim Chico, Professor of Cardiovascular Medicine at the University of Sheffield, said: "This study suggests that lead, or factors that increase people's exposure to lead, causes thousands more deaths every year than we previously recognised."