Arsenic, a naturally occurring poison and carcinogen found in ground water, is ply linked to adult-onset diabetes, U. S. researchers said on Tuesday. 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-Aeien and colleagues at Johns Hopkins University in Baltimore found a " relatively p " association between commonly found levels of arsenic in urine and type 2 diabetes in a study of American adults. " It seems there is maybe 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. the situation becomes even more serious. "
Arsenic raises the risk for cancers of the bladder, lung, kidney, skin and, possibly, the pros tate, 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.
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.
What can we infer from paragraph 3（）
A. Low level of arsenic seems to do no harm to human health
B. Different people have tolerance for different arsenic levels
C. There is a positive correlation between the risk for diabetes and the arsenic levels
D. Arsenic levels will be higher after people suffered from diabetes
