Biological Effects of Ionizing Radiation Stochastic Somatic Effects Radiation risk Lecture IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

Add module code number and lesson title2 Introduction l Risk of radiation-induced cancers is the main value which can evaluate the radiation harm on human l Many studies have been published which have calculated risks of radiation-induced cancer for different populations: n predominantly on information derived from the A-bomb survivors but supplemented by information from other epidemiological studies n most risks have been calculated for the general population, although a number of reports have also given risks for workers

Add module code number and lesson title3 Content l D ose-response relationship l Absolute and relative risk models l Dose and dose rate effectiveness factors l ICRP risk factors l Fatal and non-fatal cancers

Add module code number and lesson title4 Overview l Cancer is the most important health effect of ionising radiation l Radiation-induced cancers are well studied and documented l Risk is the value to evaluate the probability of radiation-induced cancer

Add module code number and lesson title5 Dose-response: problems to assess ? Range of inference Observable range Dose Response (probability)

Add module code number and lesson title6 Dose-response relationship

Add module code number and lesson title7 Risk – what is it? l Risk of stochastic consequence is the probability of it occurrence

Add module code number and lesson title8 Absolute risk AR – absolute (excess) risk when person is exposed in the age а for all ages t = а + L (L – latency period) (D) – mortality rate in the age t from radiation- induced cancer due to exposure in the dose D at the age а (D) – mortality rate in the age t from radiation- induced cancer due to exposure in the dose D at the age а (о) – mortality rate in the age t from spontaneous cancer (о) – mortality rate in the age t from spontaneous cancer

Add module code number and lesson title9 Relative risk RR – relative risk, which is constant for all ages t > а + L (L – latency period) a - age of exposure (D) – mortality rate in the age t from radiation- induced cancer due to exposure in the dose D at the age а (D) – mortality rate in the age t from radiation- induced cancer due to exposure in the dose D at the age а (о) – mortality rate in the age t from spontaneous cancer (о) – mortality rate in the age t from spontaneous cancer

Add module code number and lesson title10 Risk models: additive and multiplicative l The additive (absolute) risk model: radiation will induce cancer independently of the spontaneous rate after a period of latency, variations in risk may occur due to sex and age at exposure l The multiplicative (relative) risk model: the excess (after latency) is given by a constant factor applied to the age dependent incidence of natural cancers in the population

Add module code number and lesson title11 Exposure Plateau length Age Conditional probability rate Additive risk model

Add module code number and lesson title12 ExposurePlateau lengthAge Conditional probability rate Multiplicative risk model

Add module code number and lesson title13 Dose and dose rate effectiveness factor (DDREF) l Reason for use: n Risk coefficients for radiation-induced cancer are mainly based on population groups exposed at high doses and high dose rates n Studies showed that radiation damage increases with dose n We need assumption to reduce effectiveness of radiation in inducing cancer in man at low doses and low dose rates

Add module code number and lesson title14 DDREF values SourceDDREF ICRP NCRP UNSCEAR 1986 up to 5 UNSCEAR NRPB BEIR ICRP

Add module code number and lesson title15 Risk of fatal cancer, % Gy -1 Organ Risk projection model MultiplicativeAdditive Red bone marrow All cancers except leukaemia Bladder Breast Colon Lung Myeloma Ovary Esophagus Stomach Reminder Total7.14.5

Add module code number and lesson title16 Lifetime fatal cancer risks in populations* SourcePopulation Fatal cancer risk, Sv -1 UNSCEAR a BEIR III 1980 USA UNSCEAR 1988 Japan b NRPB 1988 UK c BEIR V 1990 USA7.9 ICRP nations 10.0 d for all ages. both sexes, associated with exposure to low LET *- for all ages. both sexes, associated with exposure to low LET radiation at high doses and high dose rates, based on a multiplicative projection model

Add module code number and lesson title17 Risk for fatal cancers, Sv -1, ICRP 1991 Organ or tissue PopulationWorkers Bladder3024 Red bone marrow 5040 Bone surface 54 Breast2016 Colon8568 Liver1512 Lung8568 Esophagus3024 Ovary108 Skin22 Stomach11088 Thyroid86 Reminder5040 Total500400

Add module code number and lesson title18 Probability Coefficients for fatal and non-fatal radiation-induced cancers Exposedpopulation Fatal cancer Non-fatal cancer Adult workers only Whole population (all age groups)

Add module code number and lesson title19 Absolute risk coefficient of radiation-induced thyroid cancer Study Average thyroid dose, Gy EAR/10 4 person-years- Gy, CI A-bomb survivors (Ron, et al, 1995, Thomson et al, 1994) ( ) Pooled analysis of 7 studies (Ron et al, 1995) ( ) Thyroid cancer in Belarus, Russia, Ukraine after Chernobyl (Jacob et al., 1998) ( ) Cancer in Belarus after Chernobyl (Buglova et al., 1997) Cancer in Ukraine after Chernobyl (Lihtarev et al., 1999) ( )

Add module code number and lesson title20 Summary l This lecture presented materials about radiation risk l The following topics were covered in the lecture: dose-response relationship, absolute and relative risk models, dose and dose rate effectiveness factors, ICRP risk factors, fatal and non-fatal cancers l Comments are welcomed

Add module code number and lesson title21 Where to Get More Information l UNSCEAR, Sources and Effects of Ionizing Radiation, 2000 Report to the General Assembly with Scientific Annexes, United Nations, New York, 2000 l International Commission on Radiological Protection. Publication N 60. Recommendations of the International Commission on Radiological Protection. - Oxford: Pergamon Press, 1991 l IAEA Regional Basic Professional Training Course on Radiation Protection. September-October, Germany, Training materials l IAEA Training Course at IPSN. Medical Emergencies in Case of Radiological Accidents. November Training materials