Mr. Thomas has expert capabilities in model development, risk analysis, uncertainty analysis, and database management.  Mr. Thomas has specific training in health physics and internal dosimetry concepts and calculation techniques, with more than 23 years of experience in performing quantitative uncertainty analyses.  


Mr. Thomas provided the primary programming efforts for two independent web-based versions of the Interactive RadioEpidemiological Program (IREP), one for the National Cancer Institute (NCI) and one for the National Institute 

of  Occupational Safety and Health (NIOSH).The NCI version of IREP is available at https://www.irep.nci.nih.gov/irep and the NIOSH version is available at https://www.niosh-irep.com/irep_niosh. He also prepared user’s guides for these computer programs. 

He has also been involved in programming the NCI Radiation Risk Assessment Tool (RadRAT) [http://irep.nci.nih.gov/radrat], for estimating the lifetime risk of cancer incidence for members of the U.S. population and other selected countries from exposure to ionizing radiation. Mr. Thomas has helped develop an internet-based computer code to support NCI’s efforts in disseminating quantitative information about the thyroid dose and future lifetime risk of thyroid cancer incidence from exposure to radionuclides in fallout following atmospheric nuclear bomb tests at the Nevada test site and other global sites.

Mr. Thomas is providing support to the National Aeronautics and Space Administration (NASA) for estimation of health risks due to exposures to space radiation. For NIOSH, Mr. Thomas has participated in development of an internal dosimetry computer code for analysis of bioassay data from exposure to plutonium and uranium.  Mr. Thomas investigated the transfer of risk between populations for EPA’s risk assessment methodology.


Mr. Thomas also provided support to the University of Utah to assist in the reconstruction of the models and assumptions used to calculate individual thyroid doses in the "Cohort Study of Thyroid Disease and Radioactive Fallout from the Nevada Test Site. The entire calculation was reprogrammed, based on the intent of the authors of the study.


Mr. Thomas was involved in a project with Lawrence Berkeley National Laboratory (LBNL) dealing with concerns over tritium releases to the atmosphere from the National Tritium Labeling Facility. Mr. Thomas was involved in modelling atmospheric releases at the LBNL site using the CALPUFF modeling system.


He participated in the Oak Ridge Dose Reconstruction Project, a large-scale project dealing with health risk and radiation dose estimation for members of the public exposed to historical releases of radionuclides from the Oak Ridge Reservation (ORR) at Oak Ridge, Tennessee. In this project, his responsibilities included the development of user-friendly models to quantify the uncertainties in the dose and risk estimates. Mr. Thomas performed quantitative uncertainty analyses for the Lower Watts Bar Reservoir in Oak Ridge, Tennessee; the Clinch River/Poplar Creek systems in Oak Ridge, Tennessee; and the Columbia River in Washington State.


E-mail Mr. Thomas at: brian@orrisk.com

Brian A. Thomas, M.S.

Senior Scientist