So, what is the link between lead exposure and heart disease? But only 20% of Americans now smoke, while lead exposure is more common, affecting 90% of people in the study. Of these, at least 256,000 occurred from cardiovascular disease - a number suggesting lead exposure could be a far greater cause of death than initially thought.
Metin Avkiran, associate medical director at the British Heart Foundation, added: "This study adds to the substantial evidence that exposure to lead can have long-term consequences". However, this new study finds that low-level lead exposure (between 1-5 micrograms of lead per deciliter of blood) increases the risk of premature death, especially from cardiovascular disease.
Lead was added to petrol until the 1990s to boost engine compression, and was also widely used to improve the performance of household paint before being banned in the USA in 1978 and the European Union in 1992 "after concerns over the effects it was having on the environment and children's brains", adds the paper.
"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 ( 0.24 mol/L), which is the current action level for adults in the United States of America, are associated with cardiovascular mortality", they added.
Lead was undetectable in the blood of almost one in 10 of the volunteers tested. Of these, 1,801 were from CVD and 988 were from heart disease.
Using these data, the team calculated that blood lead levels higher than 1 μg/dL are responsible for around 412,000 deaths in the US each year.
People with higher lead exposure were 37-percent more likely to die prematurely from any cause.
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". And adult exposure to lead even at levels so low that they've been considered relatively benign is actually deadly enough to be considered a leading cause of death in the US.
"Lead represents a leading cause of disease and death, and it is important to continue our efforts to reduce environmental lead exposure", Lanphear said.
"Currently, low levels of lead exposure are an important, but largely ignored risk factor for deaths from cardiovascular disease".
"A key conclusion to be drawn from this analysis is that lead has a much greater effect on cardiovascular mortality than previously recognized", wrote Philip J. Landrigan, MD, MSc, in a related editorial.
Researchers said that it was possible these risk factors could confound the research and that scientists were unable to adjust for some other critical factors that contribute to cardiovascular disease, including air pollution. "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".