M. Auge Consultant hydrogeologist, Buenos Aires, Argentina

ABSTRACT: A regional map of 1:3.000.000 was elaborated with the lines of threshold of 0.05 and 0.1 mg L−1 of dissolved As, in the groundwater of the Buenos Aires province. The map shows that 87% of the provincial territory (267,000 km2) has groundwater that exceeds the standard of 0.05 mg L−1 recommended for drinking water and only 13% (40,000 km2) of its total area (307,000 km2) account with underground water suitable for human consumption. Fortunately, around 91% of the total population of the province of Buenos Aires is placed in areas where As in groundwater is less than 0.05 mg L−1 and, therefore, the water is drinkable according to the existing regulations.