A Method for Determining Organ Dose from External Exposure Monitoring Data Timothy D. Taulbee, James W. Neton, and Larry J. Elliott U.S. Department of Health and Human Services (DHHS), Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), 4676 Columbia Parkway MS: R-45, Cincinnati, Ohio 45226 Energy Interval Estimation Exposure Geometry INTRODUCTION RESULTS • Problem: • Problem: 1.Photon exposures typically cover 1.Organ dose is dependent on • Organ dose is needed for a a wide range of energies. exposure geometry. • Large variances in Dose compensation decision under the Conversion Factors can result United States Energy Employees 2.Organ dose conversion 2.Typical work environment can due to monitoring methodology. Occupational Illness coefficients are tabulated for result in multiple exposure Compensation Program Act discrete energies. geometries. Organ dose (EEOICPA) of 2000. conversion coefficients are 1.60 ) DT/Hp(10) M 1.40 3.Probability of Causation DT/Exposure (R) tabulated for discrete energies. /D T • To determine organ dose from calculations used in the NIOSH 1.20 monitoring data, Dose Conversion Interactive RadioEpidemioligical 3.Of the six exposure geometries 1.00 Factors (DCFs) are needed. Program (NIOSH-IREP) use presented in ICRP Publication 0.80 three photon energy intervals 74, only four are of primary • Dose Conversion Factors are based on Radiation Effectiveness interest in occupational dose. 0.60 dependent on: Factors (REFs). 0.40 •Organ of Interest (Cancer 0.20 • Solution: An average dose Dose ConversionFactor (D 30-250 keV Photons - AP Geometry) - AP Photons keV 30-250 Location) – Photons < 30 keV conversion factor can be developed 0.00 •Radiation Monitoring Method – Photons 30-250 keV using a time weighted average Bone Marrow Lung Breast (Female) •Photon Energy – Photons > 250 keV approach. •Exposure Geometry DCF D , E = w DCF D , E + w DCF D , E + • Solution: Calculate average dose ( M γ )W AP ( M γ )AP PA ( M γ )PA • Computational methodology w DCF D , E w DCF D , E conversion factor by integrating ROT ()M γ ROT + ISO ()M γ ISO should be from most specific METHOD over energy interval and dividing by information to least. the energy range. Facility Job Geometry TWA ISO 75% • Generally, monitoring Monitoring Device Conversion 0.250 General Laborer AP 25% methodology and energy f (E)dE Uranium Facility ∫ Lung Dose - Gy AP 75% spectrum are known more • Problem: DCF (D ,E ) 0.030 0.695 Machinist M γ ,0.030−0.250MeV = = ISO 25% precisely than exposure Range Hp(10) Gy 1.ICRP Publication 74 Organ AP 50% Fuel Handler geometry. Dose Conversion Coefficients ROT 50% Reactor use a non measurable quantity 1.4 ROT 75% Reactor Operator • Same methodology can be of free-air KERMA. 1.2 ISO 25% applied to neutron monitoring. AP 90% 1.0 Glovebox Chemist 2.Measured Radiation Exposure Chemical ROT 10% 0.8 or Dose quantities include: Separations ROT 50% Security Guard • Exposure (Roentgen (R)) 0.6 ISO 50% CONCLUSIONS (10) - AP Geometry p 0.4 • Ambient Dose Equivalent /H T D (H*(10)) 0.2 • Example of Work Specific Dose • Personal Dose Equivalent Lung Dose Conversion Factor 0.0 Conversion Factor (same cancer • Published information can be (Hp(10)) 0.01 0.1 1 10 and energy interval) used to convert monitored film Photon Energy (MeV) badge and dosimeter results into • Solution: Organ dose is 1.4 • Lung Cancer Dose Conversion organ doses relatively easily. determined by first converting 1.2 Factor measured dose to free-air 1.0 Organ Dose/Exposure (D /D ) • Using this methodology the KERMA and then applying DCFs T M 0.8 30-250 keV photons (Eγ) magnitude of the differences in ICRP 74. between monitored external dose 0.6 1 DT 1.Glovebox Chemist and organ dose can be evaluated DCF( DM ,Hp(10 ) D ) = × 0.4 → T /Exposure - AP Geometry DCF(D ,E ) = 0.965 Gy/100R and accounted for in external H (10 ) K T M γ W p a D 0.2 dose reconstruction. Lung Dose Conversion Factor K a 0.0 2.Security Guard 0.01 0.1 1 10 DCF(D ,E ) = 0.702 Gy/100R Photon Energy (MeV) M γ W.