Oak Ridge Center for Risk Analysis collaborated with the National Cancer Institute (NCI) to develop a web-based Calculator for estimation of radiation doses and risk of thyroid cancer from exposure to radioactive iodine (I-131) in fallout from nuclear weapons tested at the Nevada Test Site (NTS).

The calculator is available on the NCI website (www.cancer.gov/I-131), in a special area dedicated to the effects of radioactive fallout. It can be accessed directly using the following address: http://ntsi131.nci.nih.gov/


The calculator allows individuals to estimate their I-131 exposure from nuclear weapons tests conducted from 1951 to 1962 at the NTS. Specialized input screens allow the user to enter a complex exposure history with multiple residencies, different sources of milk consumed, and different amounts of milk consumed for a given year. The personal data entered by users of the code is used to access the pre-calculated total doses to the thyroid gland from all nuclear NTS weapons tests and test series. Thyroid doses and their uncertainties can also be displayed for each test, and for each year of exposure.

The "thyroid risk" component provides estimates of NTS fallout-related lifetime risk of thyroid cancer. If a thyroid cancer was diagnosed, the calculator reports estimates of the assigned share (which is a measure of the probability that the cancer was induced by the past exposure to radiation in weapons fallout). The risk estimates are based on the excess relative risk coefficients recommended by the National Academies of Science's BEIR VII committee in their 2006 report.


The uncertainties in all the input parameters and model assumptions are expressed as probability distributions and propagated in real time using Monte Carlo simulation to produce alternative realizations of individual lifetime risk and probability of causation / assigned share (PC/AS). The final results are expressed as an upper and lower credibility bound and a central estimate.


Look-up Tables of Thyroid Doses and Risks of Thyroid Cancers


In addition to the on-line interactive dose and risk calculator, Oak Ridge Center for Risk Analysis produced a set of look-up tables containing estimates of doses and risks for eight representative birth cohorts and sixty-seven locations in eight regions around the continental United States. The look-up tables provided do not cover all possible exposure situations, but they can be used to estimate the general magnitude of a person's thyroid dose and risk of thyroid cancer from NTS fallout according to birth cohort, gender, given residence history, and given amount and type of milk consumed. These tables allow an easy comparison of doses and risks among individuals with different birth dates, genders and exposure histories. The look-up tables and the accompanying report is available in PDF format through the following link: Moore, A. G., Apostoaei, A. I., Thomas, B. A., and Hoffman F. O. Thyroid Doses and Risk of Thyroid Cancer from Exposure to I-131 from the Nevada Test Site. 2006

Development of an
​Interactive Dose/Risk Calculator for the
National Cancer Institute