The measurement of total iodine concentration in tap water samples across Israel revealed a decrease in the present-day iodine status compared with the data from literature sources . In sample groups with lower iodine concentration, we also observed lower Mg concentration, higher Ca/Mg ratio, and lower water hardness, which indicates a higher percentage of DSW in the final water blend supplied to consumers. The hourly and annually dynamics of iodine concentration in the tap water of big cities were found to be relatively