Comparison of Chemical and Microbial Contaminants in Tap and Bottled Water in a U.S.-Mexico Border Community

摘要

Bottled-water use is steadily increasing in the United States because of increased advertising by bottled-water purveyors and fear that municipal tap water might be contaminated. In Nogales, Arizona, some water purveyors have received drinking-water violations, but it is not clear whether local tap and bottled water differ in quality. The purpose of this study was to assess possible significant differences in the quality of municipal tap water and bottled water in Nogales. Water samples were collected from thirty homes and assayed for chemical and microbial contaminants regulated by the U.S. Environmental Protection Agency. Bottled water included small (0.5 L) and large (3.8 L), individually sealed water bottles as well as water purchased in reusable containers from self-service vending machines or from water stores. There were no significant differences in the concentration of chemical contaminants between tap and bottled water. Fecal coliforms were confirmed in 2/30 of tap- and 16/30 of bottled-water samples. Bottled water stored in reusable large containers (n=17) had the highest concentration of fecal coliforms, which were detected in 14 samples. Families who reported cleaning large reusable water containers with soap or hot water had significantly lower fecal coliforms (p=0.003) in their drinking water than those who rinsed with only water. Water samples collected directly from stores and sealed bottles contained no detectable coliforms, with the exception of one sample collected directly from a vending machine. Results suggest that secondary contamination in the home might contribute to higher levels of coliforms in water stored in reusable containers. These results are from grab samples and additional samples would be needed to understand fluctuations over time. Interventions can be implemented to educate families on keeping reusable water containers clean and on the quality of local tap water.