This International Standard specifies a method to measure the 210Po activity concentration by alpha spectrometry in all kind of natural waters.The detection limit of this measurement depends on the volume of the sample, the counting time, the background count rate and the detection efficiency. In the case of drinking water, the analysis is usually carried out on the raw sample, without filtration or other pre-treatment.If suspended material has to be removed or analyzed, filtration at 0,45 ìm is recommended. The analysis of the insoluble fraction requires amineralisation step that is not covered by this International Standard (NF M 60-790-4(4)). In this cas