Why is arsenic poisoning appearing now? Part of the reason is increased dependence on well water, but some villages have had wells for centuries with no problem. One theory is that excessive withdrawals now lower the water table during the dry season, exposing arsenic-bearing rocks to air, which converts normally insoluble salts to soluble oxides. When aquifers are refilled during the next rainy season, dissolved arsenic can be pumped out. Health workers estimate that the total number of potential victims in India and Bangladesh may exceed 200 million people. But with no other source of easily accessible or affordable water, few of the poorest people have much choice. Although few places in North America have as high groundwater arsenic content as West Bengal, there are worries that millions of Americans also are exposed to dangerously high levels of this toxic element. In 1942, the U.S. Government set the acceptable level o arsenic in drinking water at 50 micrograms per liter (50 parts per billion or ppb). Although this standard was set before the connection between arsenic and cancer was understood, it has never been revised. Recent studies suggest that the risks of certain kinds of cancer from a lifetime of drinking water with 50 ppb of arsenic may be as high as 1 in 100, or 10,000 times the normally accepted threshold for acceptable risk. Repeated attempts to lower the standard to 10 ppb have been met with resistance from public officials and private water supply owners, who complain that it would cost too much to upgrade their systems. The government has no business, they maintain, in telling us what we can or cannot drink.