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

Add module code number and lesson title2 Introduction l Stochastic health effects of radiation as one of the types of health effects l Stochastic health effects: n Radiation-induced cancers n Hereditary effects l Sources of data: n Animals n Cohorts of exposed people

Add module code number and lesson title3 Content l S tochastic effects n definition, description, explanation, methods of detection l Latent periods l Sources of data for investigation of stochastic effects n animal and human data l Observations of radiation-induced cancers n bone, leukaemia, lung, liver, thyroid) l Stages and description of oncogenesis

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 Oncogenesis induced by radiation l Individual cancer can not be define as caused by radiation exposure

Module 265 Ionising Radiation and Human Cellular Level Normal repair of damage Daughter cells die Cell dies from damage No repair or non-identical repair before reproduction

Add module code number and lesson title6 Stochastic Health Effects: Definition l A radiation-induced health effect, generally occurring without a threshold level of dose, whose probability is proportional to the dose and whose severity is independent of the dose n Stochastic effects may be somatic effects or hereditary effects, and generally occur without a threshold level of dose n Examples include cancer and leukaemia

Module 267 Stochastic Health Effects l If the cell is not killed but the genome is changed, it may give rise to a mutated cell clone l From one of these cells through the chain of possible several mutations after many years the first cancer cell can appear l If any cell, capable of dividing, is hit by radiation, a cancer may arise l Cancer and hereditary effects are the stochastic effects of radiation

Module 268 Stochastic Health Effects (Cont’d) l No threshold dose exists l Assumed no safe dose l Late appearance (years) l Latency period: n Several years for cancer n Hundreds of years for hereditary effects l Probability increases with the dose l Degree of severity doesn’t increase with the dose

Add module code number and lesson title9 Latent period for radiation- induced cancers Solid cancers Leukemia Years after exposure Excess cancer incidence

Module 2610 Stochastic Health Effects (Cont’d) l Dose response is believed to be more or less linear l Dose rate may have a slight effects on the probability of effect Dose Probability of effect

Add module code number and lesson title11 Stochastic health effects: methods of detection l Indistinguishable from “spontaneous cancers l No method for identification of the appearance of this effect of ionizing radiation in individuals l Increase in occurrence of stochastic effect can be proved with epidemiological method only

Add module code number and lesson title12 Radiation induced cancer: animal data l Sufficient l Limited l Inadequate l No data l No evidence (negative)

Add module code number and lesson title13 Radiation induced cancer: human evidence l Sufficient l Limited l Inadequate l No data l No evidence (negative)

Add module code number and lesson title14 Sources of Data on Human Effects of Radiation Overexposure l Occupational exposure n Early radiologist and medical physicists n Ra-dial painters n U-miners, nuclear industry workers l Medical overexposure l A-bomb victims l Overexposure due to nuclear weapons test l Accidents l Inhabitants of high natural background areas

Add module code number and lesson title15 Radiation-induced cancer: sources of data Type or localization of cancer Population groups Leuke- mia Thyroid gland LungBreastBoneSkin A-bomb survivors ++++ Ra-dial painters + Early radiologists + U-miners+ Exposed in a nuclear accident +

Add module code number and lesson title16 Multistage cellular development in oncogenesis l Phases of oncogenesis; n Initiation n Promotion n Progression

Add module code number and lesson title17 Phases of cancer induction and manifestation

Add module code number and lesson title18 Cancer deaths attributable to A-bombs In survivors of Hiroshima and Nagasaki A-bombing 7827 persons died of cancer in : ObservedExpectedExcess(%) All tumors (4.4) Leukaemia (35.0) All cancers (5.4)

Risk of Leukemia Depending on the Age at Exposure to A-bombs

Add module code number and lesson title20 Radiation-induced bone cancer l Study group: n Persons exposed by 224 Ra and 226 Ra s painters of luminous dials s radium chemists s persons treated with radium salts for a supposedly therapeutic effect l Increased incidence of bone sarcoma was observed

Add module code number and lesson title21 Radiation-induced lung cancer l Study group: n Underground miners working in Czechoslovakia. Canada, United States of America and Sweden exposed to 222 Rn and its decay products l The increase in mortality has been correlated with air concentrations of radon in different mines and the duration of exposure l Many additional factors were influencing the incidence of lung cancer

Add module code number and lesson title22 Radiation-induced liver cancer l Study group: n Patients undergone diagnostic radiology with thorotrast l Observations: n Increased risk of liver tumors and leukemia

Add module code number and lesson title23 Thyroid cancer among exposed due to Chernobyl accident children of Belarus

Add module code number and lesson title24 Summary l This lecture presented materials about radiation induction of cancer l The following topics were covered in the lecture: stochastic effects (definition, description, explanation, methods of detection), latent periods, sources of data for investigation of stochastic effects (animal and human data), observations of radiation-induced cancers (bone, leukaemia, lung, liver, thyroid), stages and description of oncogenesis l Comments are welcomed

Add module code number and lesson title25 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 IAEA Training Course at Emergency Medical Preparedness and Response. Medical Education and Inter-Regional Harmonization Program for Nuclear Accident Preparedness. September, 1999, Budapest, Hungary, Training materials 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