"More than 100 million people are exposed to underground water with high concentrations of arsenic," says Chih-Hao Wang, M.D., lead author. "Chronic arsenic poisoning, called arseniasis, is an emerging epidemic in Asia. Our results indicate that long-term arsenic exposure may lead to the progression or acceleration of carotid artery disease and most likely generalized artery disease in humans."

The researchers studied 199 men and 264 women in an area of Taiwan with a high prevalence of arseniasis and high rates of blackfoot disease, a unique form of peripheral vascular disease that begins with coldness or numbness in the lower extremities and progresses to dry gangrene and spontaneous amputation. Subjects in the study were recruited from earlier investigations by the Blackfoot Disease Study Group. Scientists have measured the amount of arsenic in well water in the region since the early 1960s.

Based on those measurements and detailed questionnaires given to the subjects, the researchers calculated the duration and amount of arsenic exposure for each individual. They directly measured the atherosclerotic plaque in each subject's carotid arteries with ultrasound.

Three indices of long-term exposure to arsenic - how long someone consumed artesian well water, the average arsenic concentration in that water, and the cumulative arsenic exposure - were significantly associated with prevalence of carotid atherosclerosis in a dose-dependent relation.

Researchers divided subjects into three groups based on arsenic exposure levels and found that those with the highest exposure had three times the risk of atherosclerosis as people who were not exposed to arsenic. Those in the mid-range of exposure had double the risk of someone who was not exposed to arsenic.
"From the strong dose-dependent relationship, we conclude that long-term arsenic exposure is an independent risk factor for atherosclerosis and that carotid atherosclerosis is a novel marker for arseniasis," the researchers write.