Microbiological groundwater quality and health indicators in Mexico City

Groundwater quality was evaluated in the southern and western zones of Mexico City, using bacterial indicators and pathogens. Water quality from 40 wells was related to rates of diarrheal disease with 995 individuals interviewed. The focus of this first study on environmental health indicators (EHI) was based on population data (e.g., drinking water supplies and basic sanitation) and displayed using a Geographic Information System (GIS). Sixty percent of the wells monitored comply with the Mexican drinking water standards; however, based on other microbial evidence, 95% of the wells did not provide good quality water for human consumption. No significant differences were detected among hydrogeological zones. When analyzing by microbial indicators, the southern area was shown to be statistically different (p < 0.01) from the western area of the city. The highest rates of diarrheal diseases were detected in the south; the lowest rates were observed in the west. Although wells in the western side of the city appeared to be more contaminated (54%) than in the south (40%), no significant association with health indicators was detected. These preliminary findings suggest ways to improve the potential of EHI, by framing epidemiological data and the use of GIS.