New research suggests that drinking arsenic-laden water can produce dangerous narrowing in the carotid artery, which channels blood through the neck to the brain. The newly identified arsenic risk joins a slew of health problems, including other cardiovascular conditions and several cancers, previously linked to consumption of the poisonous metal.
“Long-term arsenic exposure may lead to the progression or acceleration of carotid artery disease,” says Chien-Jen Chen of National Taiwan University in Taipei, a member of the study team.
The metal’s hormone-disrupting actions may underlie some of its poisonous effects (SN: 3/17/01, p. 164: Arsenic Pollution Disrupts Hormones). Other problems may result from growth that arsenic might trigger in tissues such as those that line artery walls, says Aaron Barchowsky of Dartmouth Medical School in Hanover, N.H.
Several U.S. states and parts of countries such as Bangladesh, Chile, and Taiwan have naturally high concentrations of arsenic in groundwater. Worldwide, more than 100 million people are exposed to high-arsenic water, Chen estimates. He and his colleagues have been studying arsenic’s health effects in southwestern Taiwan, where tainted wells provided people with drinking water for more than half a century before being phased out in the mid-1970s.
In the current study, Chen and his team questioned 436 people, all of whom had lived near arsenic-contaminated wells for at least 6 months. The researchers asked the volunteers about factors that could play a role in cardiovascular disease. Following the interviews, the researchers used ultrasound scanning to identify people whose carotid arteries exhibit atherosclerosis–vessel narrowing because of either plaque formation or vessel-wall thickening.
After accounting for other factors that affect the arteries–age, sex, blood pressure, cholesterol concentration in blood, diabetes, smoking, and alcohol use–the researchers found that both the duration and degree of exposure to high-arsenic well water correlates with an individual’s carotid artery showing atherosclerosis.
People who’d consumed high-arsenic water for 30 or more years were more than three times as likely to suffer from carotid atherosclerosis as were people who drank contaminated water for less than 15 years. Study participants who drank contaminated water for similar periods were about three times as likely to have carotid atherosclerosis if their well contained at least 0.70 milligram of arsenic per liter than if it contained less than 0.05 mg/l, the researchers report in the April 16 Circulation.
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Because ultrasound enabled the researchers to gauge the cardiovascular health of each participant–rather than only of those who had suffered strokes and other cardiovascular ills–the new study is more powerful than previous attempts to determine arsenic’s effect on arteries, says Allan H. Smith of the University of California, Berkeley. However, he says, follow-up studies are needed to confirm that arsenic-induced carotid atherosclerosis leads to cardiovascular disease.
Combined with previous studies by the Taiwanese team, the new research “clearly shows there is a cardiovascular risk associated with drinking arsenic-laden water,” says Barchowsky. Less clear has been the persistence of arsenic’s cardiovascular effects, he adds. Since use of arsenic-tainted wells in Taiwan ceased 2 decades before the team collected data for its study, it appears that health effects can persist long after exposure, he says.