vs 17 Precipitation data from the Quarterly Health Physics Reports of Atomic Energy of Canada, Limited. | , The source of the elevated tritium in this table is the thermonuclear _ testing carried out from 1952 through 1961. Tritium from the more recent thermonuclear tests has not yet appeared in precipitation samples. There is some variation in the excretion pattern of tritium with age following a single exposure. This has no effect in the case cf continuous exposure from the environment and the body burdens reflect the amount of . body water times the concentration in the environment. The geographical pattern of tritium in precipitation in the United States is available for 1963. The data are shown in the following table. Tritium in Precipitation-United States, 1963 Average (U. S. Geological Survey Data) ~ Palmer, Alaska Menlo Park, Calif. Salt Lake City 2950 Tritium Units 480 . 3670 Albuquerque 1870 Denver Lincoln, Neb. Madison, Wis. Bismark St. Louis Baton Rouge Boston Washington Ocala, Fla. San Juan 3110 2280 2510 4370 1560 830 1410 1130 620 ako Data from Stewart and Hoffman, Geological Survey Circular: 520 (1966) Carbon-14 (Natural and Man-made) Carbon-1h is produced in the atmosphere by cosmic-ray bombardment. The isotope has a long half-life (over 5000 years) and is mixed uniformly with the carbon compounds of living matter to give an activity of about 6 pCci/gren