On 1 January 2006, a new U.S. drinking water standard of 10 µgarsenic/L will come into effect [U.S. Environmental ProtectionAgency (EPA) 2001a). We strongly support the U.S. EPA’s decisionto lower the allowable limit of As in drinking water from 50 µg/L to10 µg/L because it promises to reduce the risk of an array of adversehealth outcomes attributable to As exposure, notably various cancersand cardiovascular and neurologic diseases. Throughout the United States, but particularly in the northeast-ern and southwestern states, where drinking water sources are mostlikely to exceed the 10 µg/L limit, public agencies responsible forwater quality are preparing for the arrival of the new standard in avariety of ways. In 2001, the U.S. EPA estimated that the arseniccontent of water provided by roughly 5% of U.S. community watersupplies exceeded 10 µg/L (U.S. EPA 2001b); in these cases, theintroduction of water-treatment facilities will be required to bringsystems into compliance. Although this will be expensive, the ever-increasing evidence that waterborne arsenic is a menace to publichealth—including new findings that it impacts children’s intellectualfunctioning (Wasserman et al. 2004)—warrants the cost. A significant segment of the U.S. population at risk, however,relies on individual household wells for their drinking water.Groundwater studies conducted by the U.S. Geological Survey(Focazio et al. 1999) imply that nearly 8% of domestic wells exceedthe new As standard. Here, the responsibility for water treatmentlies with the homeowner. Simple over-the-counter filtration systemsare not effective for removing As from tap water. Rather, more elab-orate technologies costing several thousand dollars (e.g., reverseosmosis systems) are required. For those who can afford it, the costof installing such systems to protect family health is small, but forthose who are economically disadvantaged, a water treatment sys-tem to remove As (and other potentially harmful elements) may notbe a high priority. To help alleviate the situation, testing of house-hold water for As should become part of the building-inspectionprocess that preceeds the sale of a home, allowing for the cost forwater treatment to be factored into the transaction.In comparison to the situation in Bangladesh and other develop-ing nations, the U.S. problem is small and readily solvable. Althoughestimates vary, perhaps as many 100 million rural inhabitants ofBangladesh and other affected South Asian countries drink untreatedwell water with As concentrations that can exceed the Bangladeshstandard of 50µg/L by more than an order of magnitude. A singlevisit to a severely affected region of Bangladesh can be a life-alteringexperience, as the skin lesions associated with the consumption ofAs-contaminated water are evident, even in young children. Whenone realizes that skin lesions are but a visible manifestation of a widersyndrome that damages multiple internal organ systems, the magni-tude of the arsenic problem becomes even more unsettling. The extent of the problem, coupled with the relative economicplight of the country, drives home the need for a more significantresponse by developed nations—and the donor community—to assistBangladesh as it works toward achieving a safe water supply. Despitecontinued efforts by the government of Bangladesh, scientists,industry, and other governmental and nongovernmental organiza-tions, large-scale removal of arsenic from groundwater or humanpathogens from surface water appears to be an exceedingly difficultobjective to achievein the near future. A temporary solu-tion appears to be athand in thousands of affected villages, but residents are often notaware of it. Deeper aquifers are typically low in As. Over the pastseveral years, the World Bank–sponsored Bangladesh ArsenicMitigation Water Supply Project (BAMWSP) has conducted a mas-sive field-testing campaign for arsenic of over 5 million wells acrossthe most affected half of the country (BAMWSP 2005). By andlarge, these results have been accurate and probably already have ledmany households to switch from their As-contaminated well to aneighboring low-As well (van Geen et al. 2002). The testingcampaign, however, did not address the needs of the many house-holds that could not switch to a safe well because of geographic orsocial constraints. The BAMWSP data could also be useful by guiding the installa-tion of community wells to those deeper aquifers that are low in As.In collaboration with scientists from Bangladesh, research conductedby a number of international groups has shown that extraction ofdrinking water from such aquifers (but not large-volume pumpingfor irrigation water, which could lead to contamination of the deeperaquifers) is feasible and likely to be sustainable in a majority of vil-lages in Bangladesh [British Geological Survey/Department of PublicHealth Engineering (BGS/DPHE) 2001; Zheng et al., in press]. Theuse of community wells that tap these deeper aquifers has beenextensive in 50 villages of Araihazar upazila, where health, Earth, andsocial scientists of Columbia University have been conducting basicresearch with support from the Superfund Basic Research Program(van Geen et al.2003). The valuable BAMWSP arsenic data, which have been compiledwith information about well location and depth, should be used in aconcerted effort to target aquifers for the installation of communitywells across a larger portion of Bangladesh. Although coupling theinstallation of these community wells to complex piped-water sup-ply systems, as currently favored by the World Bank, should be alonger-term goal, it may slow the process in the short term. In the significant number of villages where the BAMWSP datado not unambiguously identify a safe depth, exploratory drillingwill be needed (Gelman et al.2004; van Geen et al.2004). A teamsupported by the Earth Institute at Columbia University is pilotinga cell phone–based system to provide access to the BAMWSP data-base from any village in Bangladesh and to update the database asnew wells are installed. This approach will allow communities todetermine the local depth of low-As aquifers and empower themto make an informed decision concerning the eventual placementof a safe community well. All who are involved in As mitigationshould make available and advertise, at the village level, localtesting for As. Of the 6,000 wells within a 25-km2area that we tested in2000–2001, roughly 1,000