Radioactivity of spring water:
Water contains small amounts of radioactivity owing to the radioactive rocks it flows over and dissolves. As an example, the above graph displays the annual dose one would receive from a granitic spring water, supposing that one drinks a litre of this water every day for a whole year. This study shows that the contribution to the annual dose would be a fraction of millisievert (mSv) to be compared to the 2,4 mSv average dose due to natural radioactiviry.