142For water systems in the 25 states that reported arsenic data to the EPA, we have calculated two
estimates of average long-term levels: one is a very conservative estimate, the other our best
estimate, based on what we believe to be the most reasonable analytical techniques (details on
how we arrived at the estimates are included with the charts).
The table below shows the lifetime risks of dying of cancer from arsenic in tap water, based on
the National Academy of Sciences' 1999 risk estimates.
Arsenic Level in Tap Water
(in parts per billion, or ppb)Approximate Total Cancer Risk
(assuming 2 liters consumed/day)0.5 ppb 1 in 10,0001 ppb 1 in 5,0003 ppb 1 in 1,6674 ppb 1 in 1,2505 ppb 1 in 1,00010 ppb 1 in 50020 ppb 1 in 25025 ppb 1 in 20050 ppb 1 in 100Arsenic Diabetes
New research findings from the National Health and Nutrition Examination Survey suggest that
exposure to levels of arsenic commonly found in drinking water may be a risk factor for type 2
diabetes. The findings suggest that millions of Americans may be at increased risk for type 2
diabetes based on the level of arsenic in their drinking water.
Data on the nearly 800 participants in the study for which urinary arsenic concentrations were
available, indicated that urine levels of arsenic were significantly associated with the prevalence of
type 2 diabetes.
After splitting the subjects into 5 groups based on the level of arsenic in their urine, the researchers
determined that those in the highest category were more than three and one-half times more likely
to have diabetes. The strength of arsenic as a risk factor for diabetes is similar to other factors such
as obesity.
Inorganic arsenic in drinking water at concentrations higher than 100 parts per million has been
linked to type 2 diabetes in studies that took place in Taiwan, Mexico, and Bangladesh where
drinking water is commonly contaminated with high levels of arsenic. The US drinking water
standard is currently 10 parts per million, but most people on private wells have not had their water
tested and aren’t required to. The researchers estimate that about 13 million Americans live in
areas where public water systems exceed the EPA standard for arsenic and this number does not
included private wells and water systems.