Standards for arsenic in drinking water: Implications for policy in Mexico.

Global concern about arsenic in drinking water and its link to numerous diseases make translation of evidence-based research into national policy a priority. Delays in establishing a maximum contaminant level (MCL) to preserve health have increased the burden of disease and caused substantial and avoidable loss of life. The current Mexican MCL for arsenic in drinking water is 25 µg/l (2.5 times higher than the World Health Organization (WHO) recommendation from 1993). Mexico's struggles to set its arsenic MCL offer a compelling example of shortcomings in environmental health policy. We explore factors that might facilitate policy change in Mexico: scientific evidence, risk communication and public access to information, economic and technological resources, and politics. To raise awareness of the health, societal, and economic implications of arsenic contamination of drinking water in Mexico, we suggest action steps for attaining environmental policy change and better protect population health.

Assessment of Managed Aquifer Recharge Site Suitability Using a GIS and Modeling.

We completed a two-step regional analysis of a coastal groundwater basin to (1) assess regional suitability for managed aquifer recharge (MAR), and (2) quantify the relative impact of MAR activities on groundwater levels and sea water intrusion. The first step comprised an analysis of surface and subsurface hydrologic properties and conditions, using a geographic information system (GIS). Surface and subsurface data coverages were compiled, georeferenced, reclassified, and integrated (including novel approaches for combining related datasets) to derive a spatial distribution of MAR suitability values. In the second step, results from the GIS analysis were used with a regional groundwater model to assess the hydrologic impact of potential MAR placement and operating scenarios. For the region evaluated in this study, the Pajaro Valley Groundwater Basin, California, GIS results suggest that about 7% (15 km2) of the basin may be highly suitable for MAR. Modeling suggests that simulated MAR projects placed near the coast help to reduce sea water intrusion more rapidly, but these projects also result in increased groundwater flows to the ocean. In contrast, projects placed farther inland result in more long-term reduction in sea water intrusion and less groundwater flowing to the ocean. This work shows how combined GIS analysis and modeling can assist with regional water supply planning, including evaluation of options for enhancing groundwater resources.