Drinking water consumption patterns among adults—SMS as a novel tool for collection of repeated self-reported water consumption

Studies have shown that the average drinking water consumption ranges between 0.075 and 3 L/day for adults with both national and regional differences. For exposure assessment of drinking water hazards, country-specific drinking water consumption data including sources of the consumed water may therefore be warranted. To estimate the amount and source of drinking water consumed among adults in Sweden, we collected self-reported estimates using both traditional methods (telephone interviews, web questionnaire) and a novel method (Short Message Service, SMS questionnaires) in a population from an average sized Swedish municipality. Monthly SMS questionnaires were sent out during one year to obtain longitudinal information as well. SMS showed to be a promising tool for collecting self-reported consumption, as most citizens could participate and the method showed high response rate. Data collected via the SMS questionnaire shows an average consumption of cold tap water of 4.9 glasses/24 h (one glass=200 ml), while the average estimates of cold tap water collected by the traditional methods range from 4.5 to 7.0 glasses/24 h. For statistical distributions, the mean daily consumption of cold tap water for the population was best fitted to a gamma distribution. About 70% of the cold tap water is consumed at home. Based on the results from the SMS study, we suggest using 1 l/day for the average adult population and 2.5 l/day for high consumers for risk assessment of cold tap water consumption. As 46% of the tap water consumed is heated, we suggest using 1.85 l/day for total tap water consumption.