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.
AdvertisementHigh 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.
The contamination 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.
Participants 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.
After adjusting 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.
Source: Yu Chen at al "Arsenic exposure from drinking water and mortality from cardiovascular disease in Bangladesh: prospective cohort study" BMJ 2011; 342