It should be emphasized that monitoring coverage in soums varied between 30 and 100 per cent, depending on the aimag, except for Khentii (17 soums) and Bayankhongor (20 soums) Aimags, where no drinking water monitoring was performed in 2012. In 2015, in accordance with bacteriological indicators, 12.8 per cent of centralized and 28.1 per cent of decentralized water supply sources did not meet the drinking water quality standards. Calcium, magnesium, chloride and sulphate ion concentrations in the drinking water of 80 soums exceed the corresponding Mongolian National Standards and could affect public health in the region.