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 While these elements occur naturally in the earth's crust, certain
metals can also appear at unsafe levels in drinking water, food, and
air as a result of agricultural and industrial practices, mining,
and smoking, the research team notes in The BMJ. Copper and lead,
for example, can seep into drinking water from corroded pipes, while
arsenic and cadmium can accumulate in groundwater due to runoff from
factories and crop irrigation systems and are also found in
cigarette smoke.
For the analysis, researchers examined data from 37 earlier studies
with a total of almost 350,000 participants. Overall, about 13,000
people had heart attacks, bypass surgery or other events related to
heart disease and about 4,200 had a stroke.
Compared to people with the lowest levels of arsenic exposure, those
with the highest exposure were 30 percent more likely to develop
cardiovascular disease. The highest levels of lead exposure were
tied to a 43 percent higher risk, top levels of cadmium were linked
to 33 percent higher risk and the greatest level of copper exposure
was associated with 81 percent higher risk.
"These findings reinforce the fact that environmental exposures are
equally important (beyond conventional behavioral risk factors such
as physical activity or diet) for cardiovascular risk, and should
not be ignored," said lead author Dr. Rajiv Chowdhury of the
University of Cambridge in the UK.
Researchers also looked at mercury but didn't find a connection to
cardiovascular disease. This doesn't mean mercury is harmless,
Chowdhury said by email.
"Mercury can also be a marker of fish consumption, it is possible
that the association between mercury and cardiovascular disease in
these studies which we included may have been somewhat confounded by
comparative benefits of fish intake," Chowdhury added.
Accumulation of toxic metals in the body can lead to metal poisoning
and what's known as oxidative stress, said study co-author Sara
Shahzad, also of the University of Cambridge.
As the body uses oxygen, it produces by-products called free
radicals that can damage cells and tissues. The damage by oxygen
free radicals is known as oxidative stress.
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"Oxidative stress is essentially an imbalance between the production
of free radicals and the ability of the body to counteract or
detoxify their harmful effects through neutralization by
antioxidants," Shahzad said by email. "This can consequently affect
the cardiovascular and nervous systems, kidneys, eyes and brain."
Previous research has linked the metals in the study to an increased
risk of cancer, especially at higher exposures over longer periods
of time. But by pooling results from several smaller studies, the
current analysis offers fresh evidence of their potential to also
contribute to heart disease, the authors conclude.
The studies in the analysis were not controlled experiments designed
to prove whether or how exposure to metals in the environment might
directly cause heart attacks or strokes. It's also possible that
factors like poverty, food and housing quality could impact both the
risk of metal exposure and the risk of cardiovascular disease.
There's not much most people can do to avoid environmental exposure
to toxic metals, Chowdhury said. Limiting exposure requires
government action to restrict activities that cause pollution and to
encourage remediation when metals are released into the environment
as a result of agricultural or industrial practices.
"To minimize the exposure to these toxic metals, the government
should enforce legislation to control the industrial effluents and
sewage discharge leading to hazardous contamination," Chowdhury
said. "In addition, people should be given awareness about common
sources of toxic metals in their food, drink and environment to
minimize the exposure."
SOURCE: https://bit.ly/2NiVai9 and https://bit.ly/2Q8Y1ZI The BMJ,
online August 29, 2018.
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