Drinking water containing moderate levels of arsenic could increase the risk of heart disease, particularly among smokers.
A team of researchers from USA and Bangladesh tested the association between arsenic exposure and death from heart disease and assessed if cigarette smoking influenced the link.
Arsenic occurs naturally in the Earth’s crust, but high levels of the element in groundwater pose a public health threat to millions of people worldwide because exposure to it has already been associated with an elevated risk of heart disease.
Dr Yu Chen, of New York University School of Medicine, and Dr Habibul Ahsan, from the University of Chicago, led the study that involved 11,746 men and women in Araihazar, Bangladesh, where groundwater is contaminated by arsenic.
At the start of the study, participants were interviewed, underwent a physical examination and provided urine samples, which were tested for levels of arsenic.
This was repeated every two years for an average of 6.6 years.
Water samples were collected from 5,966 tube wells used for drinking to measure arsenic levels.
After adjusting for factors including age, gender, smoking status and education level, the authors found a there was a link to deaths from heart disease when exposed to lower levels of arsenic than previously reported.
The death rate for heart disease was 271 per 100,000 person years among individuals drinking water containing moderate levels of arsenic (12-864 parts per billion, or ppb) compared with 214 per 100,000 person years among those drinking water containing low levels of arsenic (less than 12ppb).
Writing in the British Medical Journal online, the authors estimate that almost 30 per cent of the deaths in the study population could be attributed, in part, to moderate levels of arsenic concentrations in well water.
In addition, the risk of dying from heart disease associated with arsenic exposure was consistently higher in current and former smokers compared with those who had never smoked.
This suggested that the cardiovascular effects of arsenic exposure, even at moderate levels, are further intensified by smoking, the authors claim.
In an accompanying editorial, Professors Allan Smith and Craig Steinmaus, from the University of California, Berkeley, USA, say that arsenic poses far higher health risks than any other known environmental exposure.
Where groundwater is used for drinking, clinicians should ask patients about their drinking water and, if it comes from a well, urge them to have it tested for arsenic, they add.
“It is too late to identify exposure after diseases caused by arsenic have been diagnosed, because many are fatal,” they conclude.
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