Millions of people across the world consume drinking water containing arsenic from inorganic sources, said the researchers in the August 20 issue of the Journal of the American Medical Association (JAMA).
In the United States, 13 million people drink tap water containing more than the US Environmental Protection Agency standard of 10 micrograms per liter of inorganic arsenic, the study said.
Earlier research established a link between exposure to high levels of inorganic arsenic in the public water supply or in the workplace and type 2, or adult-onset, diabetes, but little was known about the effects of low-level exposure, it said.
Ana Navas-Acien, of the Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, and colleagues studied 788 adults age 20 and older who had their urine tested for arsenic levels as part of a government-conducted 2003-2004 survey.
The researchers found that the 7.7 percent of the participants who had type 2 diabetes, after adjusting for other diabetes risk factors, had a 26 percent higher level of arsenic in their urine than those without the disease.
The study also found that 20 percent of the participants who had the highest arsenic levels in their urine (16.5 micrograms per liter) had 3.6 times higher risk of having type 2 diabetes than the 20 percent with the lowest level (3.0 micrograms per liter).
They concluded that arsenic could influence genetic factors that interfere with insulin sensitivity and other processes, or could contribute to oxygen-related cell damage, inflammation and cell death, which have also been related to diabetes.
"Given widespread exposure to inorganic arsenic from drinking water worldwide, elucidating the contribution of arsenic to the diabetes epidemic is a public health research priority with potential implications for the prevention and control of diabetes," the researchers said.
Odorless, colorless, tasteless and easily dissolved in water, arsenic is extremely poisonous at high levels.