. . . . . . "Reconstructing Tritium ExposureUsing Tree Rings at LawrenceBerkeley National Laboratory,California" . "Annual tritium exposures were reconstructed using treecores from Pinus jeffreyi and Eucalyptus globulus near atritiated water vapor release stack. Both tritium (3H) andcarbon-14 (14C) from the wood were measured frommilligram samples using accelerator mass spectrometry.Because the annual nature of the eucalyptus tree rings wasin doubt, 14C measurements provided growth rates usedto estimate the age for 3H determinations. A 30-yr comparisonof organically bound tritium (OBT) levels to reported 3Hrelease data is achieved using OBT measurements fromthree trees near the stack. The annual average 3H, determinedfrom atmospheric water vapor monitoring stations, iscomparable to the OBT in proximal trees. For situationswithout adequate historical monitoring data, this measurement-based historical assessment provides the onlyindependent means of assessing exposure as comparedto fate and transport models that require prior knowledgeof environmental conditions and 3H discharge patterns." . . . . . . . . .