REB Activities Related to Assessment of Bioterrorism Involving Radiation Most of the dosimetry work that is carried out at REB has direct or indirect applications to the assessment of radiation doses from bioterrorism events involving radiation. Accurate assessment of doses permits accurate projections of long-term cancer risks to be made. Examples of completed and continuing REB activities relevant to bioterrorism follow. During this fiscal year, a web-based calculator for estimating individual radiation dose and thyroid cancer risk from I-131 in nuclear weapons testing fallout has been developed and made available to the public on the NCI website. In addition, a draft report of a Congressionally-mandated feasibility study on exposure from global fallout has been revised for final submission to Congress. Ongoing REB studies include: (1) The development of a joint U.S./Russian methodology for assessment of radiation doses from nuclear weapons fallout. (2) Archiving, and putting into electronic form, historical radiological monitoring data on releases from nuclear weapons testing around the world. (3) The corroboration of analytical dosimetry estimates via biodosimetry measurements. (4) The estimation of radiation doses received by persons affected by the Chernobyl accident. (5) Participation in programs of international agencies, e.g., the International Atomic Energy Agency and the International Agency for Research on Cancer, related to the assessment of radiation doses following the dispersion of radioactive materials; and (6) The preparation of a monograph describing how dosimetry methods are applied in the assessment of medical, occupational, and environmental radiation doses. Assuming an appropriate influx of funds and personnel, the following studies could be initiated: (1) The development of a database of stable chromosome aberrations for unexposed people, in order to separate, after a radiological/nuclear event, the people who were mildly exposed from those with a baseline level. (2) A study of the effects from single or multiple low-dose exposure on the number and type of chromosome aberrations. (3) The preparation of a web-based calculator to estimate doses and cancer risks from exposure to radionuclides other than I-131 (Sr-90, Cs-137, Pu-239, etc.) in nuclear weapons fallout and possibly from other kinds of releases or exposure scenarios. (4) In collaboration with CDC, the preparation of a manual of measures to be taken soon after a radiological/nuclear event in view of an epidemiologic study. (5) The organization of training in radiation sciences of personnel involved in the mitigation of radiological/nuclear events.