Exposure to arsenic from drinking water increases risk of ischemic heart
disease and more so in smokers, according to a new study published in the
British Medical Journal.
Arsenic is a
natural element on earth and enters the drinking water supplies from natural
deposits. Arsenic has been classified as a group-1 human carcinogen. But its
effect on other diseases is yet to be established.
High levels of
arsenic exposure (>500 µg/L) in drinking water have been related to
increased cardiovascular disease risk. But, several studies have reported
positive associations between arsenic exposure at lower concentrations (<300
µg/L) and mortality from coronary heart disease and hypertension. In addition,
studies have cited that the risks associated with arsenic exposure for skin
lesions, bladder cancer, and lung cancer are higher among smokers. Studies
examining the potential interaction between arsenic exposure and cigarette
smoking in the risk of cardiovascular disease, however, are lacking.
of groundwater with arsenic in Bangladesh has been recognized as a massive
public health hazard. An estimated 57 million people have been chronically
exposed to groundwater with arsenic concentrations exceeding the WHO standard.
To evaluate the
health effects of such exposure, a cohort study in Araihazar, Bangladesh (where
groundwater is contaminated by arsenic) was conducted where 11,746 participants
were selected on the basis
of using drinking water from wells exposed to arsenic
concentrations from 0.1 µg/L to 864
µg/L (mean 99 µg /L). This helped evaluate the cardiovascular effects of
exposure at low to moderate concentrations.
underwent a physical examination. Urine samples were also taken and tested for
levels of arsenic. This procedure was repeated at two year intervals for an
average of 6.6 years.
for age, gender, smoking status and education level, a dose-response relation
between arsenic exposure and deaths from heart disease at a lower level of
arsenic exposure than previously reported, was found. There were
460 deaths in the follow-up period, out of which 198 were from cardiovascular
diseases, 85 were from cerebrovascular disease, 104 from ischemic heart disease
and rest from other diseases.
The risk of dying
from heart disease associated with arsenic exposure was consistently higher in
smokers compared with never smokers, suggesting that the cardiovascular effects
of arsenic exposure, even at moderate levels, are increased by smoking.
'As cardiovascular disease leads to about a third of the
mortality in the world, a small increased risk associated with arsenic exposure
would translate into a large number of excess deaths in the exposed population
and could be of major importance to public health', say the authors.
They concluded - 'There was a synergistic effect between
cigarette smoking and arsenic exposure at moderate or high levels on mortality
from ischemic heart disease and other heart disease. These findings suggest the
cardiovascular effects of arsenic exposure at moderate levels, which is further
potentiated by smoking'.
Arsenic poses far
higher health risks than any other known element. Water contaminated with
arsenic is tasteless, looks crystal clear, and boiling the water only
concentrates the arsenic in it.
: Yu Chen at al "Arsenic exposure from
drinking water and mortality from cardiovascular disease in Bangladesh:
prospective cohort study" BMJ 2011; 342