[Study of long-term water quality of stocked drinking water].

We examined changes in the quality of drinking water stockpiled under various conditions for emergency use. The results indicated that the change in the quality of the stocked water was influenced mainly by the preservation period and not by the amount of water in the bottle. To maintain water quality, the amount of residual chlorine is less important than using sufficiently sterilized water, bottles and caps in the bottling process. Washing the bottles with a small amount of boiling water was not sufficient to ensure complete inhibition of microbial growth.

Bacteriological and chemical evaluation of overseas mineral waters.

Overseas and imported mineral waters were subjected to visual examination, tested for standard plate count and heterotrophic bacteria, and also analyzed to determine the concentrations of several anions and cations. Some products showed turbidity or color, and several had standard plate count and/or heterotrophic bacteria. One imported natural mineral water product had a high level of standard plate count, and the levels differed with the lot. Tests for total coliform bacteria, Escherichia coli, fecal streptococci, and Pseudomonas aeruginosa were negative on additional testing of samples having standard plate counts of more than 100. The fluoride concentration of one European region sample exceeded the production standard of the Food Sanitation Act in Japan (raw water: less than 2 mg/L) and most of the products lacked the warning labels which are mandatory for fluoride concentrations over 0.8 mg/L. These results indicate that none of the raw water for mineral waters was seriously polluted, but insufficient sterilization of the bottle or cap or contamination with air-borne microbes during the production process was probably responsible for the pollution. Attention needs to be paid to fair labeling, such as no sterilization/no sterile filtration and high fluoride concentration.