According to the post in the New York Times last week, Deborah Blum claimed that arsenic seeps into groundwater could be poisoning to those who drink it.
Now, researchers are taking more attention to drinking water, from Southwestern states (e.g. Nevada) to upper Midwest and New England. Water in parts of the Central Valley of California has been be found to be tainted with arsenic as well. Here is a U.S. map, which bases on the U.S. Geological Survey, displays where there is arsenic in the drinking water. Check it out and get more idea about the water you are drinking and using now.