Individuals who are exposed to low to moderate levels of arsenic over many years may have a greater risk of developing cardiovascular disease and dying of cardiovascular problems than individuals with less exposure, according to a study published today in the Annals of Internal Medicine. The findings are likely to stoke concerns about long-term arsenic exposure in the United States through drinking water, as well as rice and other dietary staples containing the substance.
It is well established that high levels of arsenic exposure can cause illness. Studies conducted have suggested that individuals exposed to high levels of arsenic in drinking water (more than 100 μg/L) are at greater risk of peripheral artery disease, coronary heart disease, stroke, and atherosclerosis, according to the study’s authors. But less is known about the health effects of chronic low- or mid-level exposure.
To examine the relationship between lower levels of arsenic exposure and health, the researchers examined cardiovascular health and arsenic levels in urine samples from 3575 American Indian men and women participating in the Strong Heart Study. These participants were between the ages of 45 and 74 years and lived in Arizona, Oklahoma, North Dakota, or South Dakota. They were first examined in 1989-1991 and were followed up through 2008. The researchers found that those with the highest levels of arsenic in their urine were more likely to develop cardiovascular disease and more likely to die as a result of cardiovascular disease than participants with lower levels of arsenic in their urine.
The health effects of exposure to low to moderate levels of arsenic is a particular concern in many small rural US communities, where well water arsenic levels may exceed the Environmental Protection Agency standard of 10 μg/L or less. At the time the study was conducted, the authors said, arsenic levels in public drinking water ranged from less than 10 to 61 μg/L in Arizona, less than 10 μg/L in Oklahoma, and from less than 1 to 21 μg/L in the Dakotas. The authors concluded that drinking water was a likely source of arsenic exposure in Arizona and the Dakotas, while arsenic in grains and other foods were likely the primary source of exposure in the other communities examined.
“These findings support the importance of low to moderate arsenic exposure as a cardiovascular risk factor with no apparent threshold,” the authors said.
The findings may have some wider implications as well, as the US Food and Drug Administration (FDA) and other scientists are currently weighing the long-term risks of low-level exposure to arsenic from rice. A recent FDA analysis of more than 1300 rice and rice product samples found that average arsenic levels ranged from 0.1 to 7.2 μg per serving, levels the agency said are too low to cause immediate or short-term health concerns. But the agency continues to assess the long-term health effects of these levels of exposure.