Exposure to arsenic, lead, copper, and cadmium is associated with increased risk of cardiovascular disease and coronary heart disease, finds a comprehensive analysis of the evidence published today in The BMJ. An accompanying editorial by Ana Navas-Acien at the Columbia Mailman School of Public Health and colleagues points to metals as an important but neglected source of cardiovascular risk.
"Despite widespread distribution of toxic metal contaminants, technical reports from environmental and public health agencies often disregard the mounting evidence of associated cardiovascular risk," Navas-Acien and her co-authors write. "Similarly, metal exposures are neglected by the organizations that produce cardiovascular prevention guidelines."
The editorial calls the new meta-analysis an "important call for attention," adding that because metals are associated with cardiovascular disease even at relatively low levels of exposure, "population-wide strategies to minimize exposure can further contribute to overall cardiovascular prevention efforts."
In their meta-analysis, Sara Shahzad at the University of Cambridge and colleagues identified 37 separate studies involving almost 350,000 participants. A total of 13,033 coronary heart disease, 4,205 stroke and 15,274 cardiovascular outcomes were reported across the studies, which include several by Columbia Mailman Environmental Health Sciences Professors Navas-Acien and Joseph Graziano. Shahzad and colleagues conclude exposures to arsenic, lead, cadmium, and copper are associated with an increased risk of cardiovascular disease and death.
The editorial cites national surveys documenting a marked reduction in population exposure to lead and cadmium (the metals monitored for longest), which the authors say largely reflect public health policies on the control of tobacco, reduction of air pollution, remediation of hazardous waste, renovation of drinking water infrastructures, and banning of lead in gasoline. Concomitant with these reductions, cardiovascular mortality rates decreased by 43 percent; nearly a third of this decline is explained by a decline in lead and cadmium exposures.
However, Navas-Acien and co-authors highlight substantial sources of exposure today: widespread soil contamination; persistence of past uses (house paint and plumbing for lead); continuing industrial uses (plastics and batteries); and presence in tobacco and tobacco smoke, drinking water and ambient air, and dust near industrial and waste sites. Particularly, in low- and middle-income countries, including many countries in Africa and Asia, exposure to high levels of arsenic and lead "is still a serious threat to public health that requires urgent action," they write.
An emerging source of metals is electronic cigarettes, where exposure seems to be the heating coil, from where metals leach into the inhaled aerosol. (Navas-Acien is the co-author of a National Academies of Sciences, Engineering, and Medicine report on e-cigarettes published earlier this year.)
The BMJ editorial is authored by Navas-Acien, Columbia Mailman; Maria Tellez-Plaza, National Center for Epidemiology (Carlos III Health Institute) in Spain; and Eliseo Guallar, Johns Hopkins Bloomberg School of Public Health.