16 Tritium (Natural and Man-made) ‘Tritium (H- 3) is produced in the atmosphere by cosmic rays. The. natural level is “ubout 16“pCi/Liter of surfuce water, also expressed as 5 tritium units. | , There are very few reported measurements of tritium in the body. The concentration of tritium in the body water follows the concentration of tritium in the environment and these latter measurements are readily available. The following table indicates the concentrations of tritium in precipitation for ' the one site with the longest history of measurement and the corresponding burdens of tritium that would be expected in man if the water is used for drinking. - Concentration of Tritium in Precipitation and Estimated Body Burden Year Natural Level - to 1952 1953. 4 (Ottawa, Canada) Precipitation (Tritium Units) 5 20 130 . pCi/liter** 16 64 416 - Body Burden (Picocuries ) . 700 2,700 17,000 5 6 ks rho Lh 48 . 6,000 19, 000 8 800 2,560 110,000 7 9 1960 1 2 3 4 5 6 7 8 110 350 140 180 900 3,000 1,600 900 500 400 200 352 1,120 448 576 2,880 9,600 5,120 2,880 1,600 1,280 640 15,000 | 47,000 19 ,000 2k ,000 120,000 400,000 200 , 000 120,000 67 ,000 54 , 000 27,000 *1 Tritium Unit equals 1 atom of tritium in 1018 atoms of hydrogen or 3.2 picocuries of tritium per liter of water. **For convenience of comparison, and not included in original table.