"Our study calls into question the assumption that specific toxicants, like lead, have 'safe levels, '" Bruce Lanphear, a professor at Simon Fraser University and the lead author on the paper, said in a statement.
Stemming the risk requires a range of public health measures, Lanphear said in a journal news release, such as "abating older housing, phasing out lead-containing jet fuels, replacing lead-plumbing lines and reducing emissions from smelters and lead battery facilities".
"No studies have estimated the number of deaths in the United States of America attributable to lead exposure using a nationally representative cohort, and it is unclear whether concentrations of lead in blood lower than 5 μg/dL, which is the current action level for adults in the United States of America, are associated with cardiovascular mortality", the researchers explain.
Of that figure, exposure to the toxic metal may be an "important, but largely overlooked" risk factor behind the 256,000 annual cardiovascular disease deaths in the country, the authors found.
"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", Lanphear said.
More than 4,400 people died in the period - and the tenth with the highest level of lead in their blood were 37 per cent more likely to be among them than the tenth with the least.
However, they acknowledged the use of a single baseline lead value to predict outcomes over the following 20 years was not ideal; serial measurements may have been more informative.
The new Lancet study estimates that deaths from lead exposure approach the levels attributable to smoking, which kills 483,000 Americans each year.
Metin Avkiran, associate medical director at the British Heart Foundation, said: "This study adds to the substantial evidence that exposure to lead can have long-term consequences. The information that emerges from this reassessment will increase understanding of lead's contribution to mortality from non-communicable diseases, could foster collaboration between the environmental and chronic disease research communities, guide realignment of cardiovascular disease prevention strategies, and ultimately save lives".
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". A recent study tells about the health hazards of lead exposure for the people's health. The average blood lead level was 2.7 μg/dL, and a total of 3,632 study participants had a level of 5 μg/dL or higher.
They were not, however, able to factor out the possible impact of exposure to arsenic or air pollution.
During the observation, which took more than 20 years, 4422 people died prematurely, out of which more than 1800 died from cardiovascular diseases and approximately 1,000 from ischemic heart disease.