Water samples collected from 129 wells in seven of the nine sub-divisions of Ulaanbaatar were analyzed by inductively coupled plasma mass spectrometry (ICP–MS) using Clean Lab methods. The levels of many trace elements were found to be low with the average concentrations. The levels of uranium were surprisingly elevated (mean, 4.6 μg/L; range < 0.01–57 μg/L), with the values for many samples exceeding the World Health Organization's guideline of 15 μg/L for uranium in drinking water. Local rocks and soils appear to be the natural source of the uranium. The levels of uranium in Ulaanbaatar's groundwater are in the range that has been associated with nephrotoxicity, high blood pressure, bone dysfunction and likely reproductive impairment in human populations. We consider the risk associated with drinking the groundwater with elevated levels of uranium in Ulaanbaatar to be a matter for some public health concern and conclude that the paucity of data on chronic effects of low level exposure is a risk factor for continuing the injury to many people in this city.
► We analyzed water samples from wells across the city of Ulaanbaatar, Mongolia for total uranium along with arsenic, manganese, cobalt, zinc, selenium, cadmium and lead. ► We found that compared to other trace metals and metalloids, the levels of uranium were surprisingly elevated with the values for many samples exceeding the World Health Organization’s guideline for drinking water. ► Local rocks and soils appear to be the natural source of the uranium. ► The health risk associated with drinking the groundwater with elevated levels of uranium in Ulaanbaatar should be a matter for some concern. ► The contamination of groundwater with uranium may be more prevalent in other parts of the world than is generally realized.