THURSDAY, May 5 (HealthDay News) -- Even moderate levels of arsenic in drinking water increases the risk for heart disease, a new study suggests.

Arsenic is a naturally occuring element found in the earth's crust. High concentrations of arsenic in groundwater pose a public health threat to millions of people worldwide, according to the study.

To assess the risk from moderate exposure to arsenic, researchers studied nearly 12,000 men and women in Araihazar, Bangladesh, where groundwater is contaminated with arsenic.

The researchers measured arsenic levels in wells used for drinking water by the participants, who also gave periodic urine samples that were tested for arsenic. Participants were followed for about 6.6 years.

The death rate from cardiovascular disease was 271 per 100,000 person years among people who drank water with moderate levels of arsenic (12 to 864 parts per billion, or ppb), compared with 214 per 100,000 person years among people who drank water with low levels of arsenic (less than 12 ppb).

Nearly 30 percent of the deaths among the study participants can be attributed, in part, to moderate levels of arsenic in drinking water, according to the researchers.

They also found that current and former smokers had a higher risk of dying from heart disease associated with arsenic compared with people who never smoked.

This suggests that smoking intensifies the cardiovascular effects of arsenic exposure, even at moderate levels.

The study was published online May 5 in the British Medical Journal.

Previous studies suggest that arsenic can induce hardening of the arteries (atherosclerosis).

More information

The U.S. Agency for Toxic Substances and Disease Registry has more about arsenic.