AHA: Toxic metal exposure threatens heart health, particularly in underserved communities
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Key takeaways:
- Complications of toxic metal exposure include ASCVD, ECG abnormalities, stroke and death.
- High lead, cadmium and arsenic levels were found in the soil and water of many historically underrepresented communities.
Toxic metals such as lead, cadmium and arsenic found in food and water represent a significant hazard CV health in the U.S., particularly among historically underrepresented communities, according to a scientific statement.
Together, the American Heart Association’s councils on epidemiology and prevention; CV and stroke nursing; lifestyle and cardiometabolic health; peripheral vascular disease; and kidney in CVD issued a call to action to reinforce regulatory measures to reduce population level exposure to toxic metals.
Data were derived from Lamas GA, et al. J Am Heart Assoc. 2023;doi:10.1161/JAHA.123.029852.
“The writing committee has, over many years of research, become concerned that there is convincing and robust population data that lead, cadmium and arsenic are toxic to the circulatory system, potentially causing coronary disease, peripheral artery disease, hypertension and stroke,” Gervasio A. Lamas, MD, chairman of medicine and chief of the Columbia University division of cardiology at Mount Sinai Medical Center and chair of the statement writing committee, told Healio. “It is frustrating that mainstream cardiology does not recognize this, because unlike age and sex, these are reversible risk factors. Each of the members of the writing committee had special areas of expertise, and we are indebted to the AHA for agreeing with our concerns, and releasing this scientific statement.”
The statement was published in the Journal of the American Heart Association.
Today, exposure to lead, cadmium and arsenic can be traced to a variety of sources:
- Modern-day lead exposure can be found in old paint, tobacco products, wheel weights, acid-lead batteries, contaminated foods, water pipes and drinking conduits, herbal remedies, toys, cosmetics, electronics and emissions from industrial facilities, incinerators and old heating systems.
- Cadmium can be found in nickel-cadmium batteries, pigments, plastic stabilizers, ceramics, glassware, construction and industrially produced fertilizers used to grow some root vegetables and green leafy plants.
- Inorganic arsenic is known to contaminate groundwater from private wells and community water systems and can be found in rice and beverages such as apple juice and wine.
Each toxic metal can be absorbed via the respiratory and gastrointestinal tracts, whereas arsenic can also be absorbed through dermal contact, according to the statement.
Gastrointestinal absorption of lead and cadmium may depend on systemic homeostasis of essential metals and bioavailability from dietary sources; however, absorption via respiratory tract is almost complete, as contaminated air easily crosses the alveolar-capillary membrane, the committee wrote.
Absorbed lead primarily accumulates in bone while cadmium accumulates in the kidneys, liver and other visceral organs where these metals can reside for decades, according to the statement.
Absorbed arsenic is methylated into mono- and dimethyl arsenic compounds and rapidly excreted from the body in urine. Arsenic metabolism is genetically determined, and women are generally more efficient at arsenic methylation compared with men, according to the statement.
“The half-life of lead and cadmium is long, in the 30-year range, so mitigation of exposure is very important. Filter your home drinking water — the filter has to say that metals are filtered,” Lamas told Healio. “In South Florida we live an air-conditioned life. Make sure that the AC filters will screen out the tiniest particles, PM2.5. Depending on where you live, inhaled particulate matter may have meta particles. Avoid smoking or exposure to tobacco smoke. Measure your patient’s lead levels and urine cadmium and arsenic and speak with patients if levels appear high. On an individual patient level, chelating drugs are effective in removing lead and cadmium from the body, and a clinical trial demonstrated a reduction in cardiac events a decade ago. A repeat clinical trial is ending and should have results soon. Finally, the body is more efficient at getting rid of arsenic, so one has to find and remove the exposure source, which is where filtering well water comes in.”
CV complications of toxic metal exposure
Absorbed lead, cadmium and arsenic can cause molecular and cellular changes including epigenomic effects on DNA methylation and histone modifications, chronic inflammation, impaired endothelial function and oxidative stress.
With epidemiologic evidence largely focused on studies of general populations, Lamas and colleagues posited that low to moderate levels of exposure to these toxic metals could be associated with preclinical ASCVD, heart rate variability, ECG abnormalities, ischemic heart disease, stroke, HF, cardiac function, peripheral artery disease and mortality.
“The mechanisms of toxicity are interesting, each toxic metal — arsenic is a metalloid, by the way — has unique toxicities, but they also all have in common that they replace other, essential elements in vital reactions, and ultimately interfere with normal metabolism,” Lamas told Healio. “The ability to identify a new series of risk factors is a great opportunity for public health, and drug development to improve the lives of our patients.”
With inductively coupled plasma mass spectrometry, the writing committee suggested possible urine biomarkers for assessment of toxic metal exposure as follows:
- 3.5 g/dL for lead exposure;
- 1 g/L for cadmium exposure; and
- 5 g/L for arsenic exposure.
“The best data come from the National Health and Nutrition Examination Survey (NHANES), a population-based study in the U.S. that is selected to represent the U.S. population,” Lamas told Healio. “In a study published in 2018, Bruce P. Lanphear, MD, and colleagues estimated that there were 410,000 deaths annually in the U.S. attributable to low-level lead exposure. Of these, 256,000 were from CVD, of which 185,000 were from ischemic heart disease. The estimates from cadmium and arsenic just add to these staggering numbers. And to think that these are preventable risk factors leaves a clinical cardiologist like me both shocked, and hopeful for the future.”
Racial/ethnic disparities in toxic metal exposure
The writing committee stated that, in the U.S., race/ethnicity highly correlate with residential location, and individuals living in underserved neighborhoods may be exposed to elevated levels of these toxic metals in drinking water and air due to proximity to environmental hazards; poor response to community complaints about toxic metal exposure; and inadequate enforcement of Environmental Protection Agency regulations.
Biomarker concentrations of toxic metals were generally higher in Black, Hispanic and Asian participants in National Health and Nutrition Examination Survey studies compared with white participants, especially for levels of cadmium and lead, according to the statement.
Lead was disproportionately found in the drinking water of neighborhoods populated by majority historically underrepresented groups, and arsenic was particularly high in the drinking water of American Indian and Hispanic communities compared with other racial/ethnic groups.
Moreover, urban areas in the U.S. with a greater proportion of people of historically underrepresented groups were also found to have higher concentrations of lead, cadmium and arsenic in the soil, according to the statement.
Those most affected by toxic metal exposure include “People who were alive in the time of leaded gasoline — before 1981 — in older homes that may have had lead paint, tobacco smokers — as tobacco plants are a rich source of cadmium — leaded and nickel cadmium battery workers, or anyone in the runoff water from a processing plant, communities with leaded water pipes, and some paints,” Lamas told Healio. “Arsenic is mostly found in well water. Lead exposure is often higher in low-income communities. These communities are more likely to have older housing and infrastructure, which may contain lead paint or lead pipes. Lack of resources for proper maintenance and renovation can exacerbate lead exposure in these settings. In effect, well over 90% of a cardiologists’ typical practice will have these metals in the blood or urine.”
Please see the AHA scientific statement for full details on the impact of toxic metals on CV health and mortality.
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