CHICAGO (Reuters) - Arsenic, a naturally occurring poison and carcinogen found in ground water, is strongly linked to adult-onset diabetes, U.S. researchers said on Tuesday.

Water runs down a sink in a file photo. Arsenic, a naturally occurring poison and carcinogen found in ground water, is strongly linked to adult-onset diabetes, U.S. researchers said on Tuesday. REUTERS/File

Odorless, tasteless, colorless and easily soluble in water or wine, arsenic has long been a feared poison. A heavy dose is detectable in a corpse, but researchers say small amounts of arsenic may sicken people gradually.

Dr. Ana Navas-Acien and colleagues at Johns Hopkins University in Baltimore found a “relatively strong” association between commonly found levels of arsenic in urine and type 2 diabetes in a study of American adults.

“It seems there is may be no safe level of arsenic,” Navas-Acien said in a telephone interview.

“Worldwide it’s a huge problem,” she said. “As water becomes a scarce resource, we need additional sources.”

Arsenic raises the risk for cancers of the bladder, lung, kidney, skin and, possibly, the prostate, Navas-Acien said.

The 20 percent of nearly 800 study participants who had the most arsenic in their bodies, a tolerable 16.5 micrograms per liter of urine, had 3.6 times the risk of developing late-onset diabetes than those in the bottom 20 percent, who had 3 micrograms per liter.

Levels of arsenic were 26 percent higher in people with late-onset, or type 2, diabetes than those without the disease, the study found.

The U.S. government sets a limit for drinking water at 10 micrograms of arsenic per liter, which is exceeded in the water consumed by 13 million Americans who mostly live in rural areas that rely on wells to bring up ground water, the researchers wrote in the Journal of the American Medical Association.

Arsenic contaminates drinking water for millions of people in Bangladesh, parts of Central Europe, Chile, Argentina and the western United States, where ground water is the source of drinking water and the land has higher concentrations of arsenic.

The U.S. Geological Survey has published maps on its Web site showing levels of arsenic contamination of ground water across the United States.

Overall, 7.8 percent of Americans are believed to have diabetes, although some do not know it. At least 90 percent of cases are the type 2 variety, in which the body loses its ability to use insulin properly.

Navas-Acien said arsenic may play a significant role in diabetes incidence, but it is difficult to say how much.

Arsenic can accumulate in the body, and can ruin the body’s ability to use insulin and perform the vital task of converting blood sugar into energy.

Normally, insulin fits into cells via molecular doorways called receptors, which in turn signal the cell to move glucose inside, but arsenic enters the cell and somehow blocks the activity.

Seafood is another source of arsenic, but the organic form found in shellfish and some fish has a carbon molecule attached and poses no risk to health, she said.

It is difficult to discern the difference between the harmful and benign forms of arsenic, though recent laboratory tests allow researchers to detect trace amounts that may pose risks to health, Navas-Acien said.