Biological Effects of Ionizing RadiationBiological Effects of Ionizing Radiation

Stochastic Somatic EffectsStochastic Somatic Effects

Radiation induction of cancerRadiation induction of cancerLectureLecture

IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

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IntroductionIntroduction

Stochastic health effects of radiation Stochastic health effects of radiation as one of the types of health effectsas one of the types of health effects

Stochastic health effects:Stochastic health effects: Radiation-induced cancersRadiation-induced cancers Hereditary effectsHereditary effects

Sources of data:Sources of data: AnimalsAnimals Cohorts of exposed peopleCohorts of exposed people

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ContentContent

SStochastic effectstochastic effects definition, description, explanation, methods of definition, description, explanation, methods of

detectiondetection

Latent periodsLatent periods Sources of data for investigation of stochastic Sources of data for investigation of stochastic

effectseffects animal and human dataanimal and human data

Observations of radiation-induced cancers Observations of radiation-induced cancers bone, leukaemia, lung, liver, thyroid)bone, leukaemia, lung, liver, thyroid)

Stages and description of oncogenesisStages and description of oncogenesis

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OverviewOverview

CCancer is the most important health ancer is the most important health effect of ionising radiationeffect of ionising radiation

Radiation-induced cancers are well Radiation-induced cancers are well studied and documentedstudied and documented

Oncogenesis induced by radiationOncogenesis induced by radiation Individual cancer can not be define Individual cancer can not be define

as caused by radiation exposureas caused by radiation exposure

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Ionising Radiation and HumanIonising Radiation and HumanCellular LevelCellular Level

Normal repair of damage

Daughter cells die

Cell dies from damage

No repair or non-identicalrepair before reproduction

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Stochastic Health Effects: Stochastic Health Effects: DefinitionDefinition

A radiation-induced health effect, A radiation-induced health effect, generally occurring without a threshold generally occurring without a threshold level of dose, whose probability is level of dose, whose probability is proportional to the dose and whose proportional to the dose and whose severity is independent of the doseseverity is independent of the dose Stochastic effects may be somatic effects or Stochastic effects may be somatic effects or

hereditary effects, and generally occur without hereditary effects, and generally occur without a threshold level of dosea threshold level of dose

Examples include cancer and leukaemiaExamples include cancer and leukaemia

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Stochastic Stochastic Health Health EffectsEffects If the cell is not killed but the genome is If the cell is not killed but the genome is

changed, it may give rise to a mutated cell changed, it may give rise to a mutated cell cloneclone

From one of these cells through the chain From one of these cells through the chain of possible several mutations after many of possible several mutations after many years the first cancer cell can appearyears the first cancer cell can appear

If any cell, capable of dividing,If any cell, capable of dividing, is hit by is hit by radiation, a cancer may ariseradiation, a cancer may arise

Cancer and hereditary effects are the Cancer and hereditary effects are the stochastic effects of radiationstochastic effects of radiation

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Stochastic Health EffectsStochastic Health Effects (Cont’d) (Cont’d)

No threshold dose existsNo threshold dose exists Assumed no safe dose Assumed no safe dose Late appearance (years)Late appearance (years) Latency period:Latency period:

Several years for cancerSeveral years for cancer Hundreds of years for hereditary effectsHundreds of years for hereditary effects

Probability increases with Probability increases with the the dosedose Degree of severity doesDegree of severity doesn’n’t increase t increase

with with the the dosedose

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Latent period for radiation-Latent period for radiation-induced cancersinduced cancers

Solid cancersSolid cancersLeukemiaLeukemia

Years after exposureYears after exposure

Exc

ess

can

cer

inci

den

ceE

xces

s ca

nce

r in

cid

ence

6 12 18 24 30 366 12 18 24 30 36

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Stochastic Health EffectsStochastic Health Effects (Cont’d) (Cont’d)

Dose response is Dose response is believed to be believed to be more more or less linearor less linear

DoseDose rate may have rate may have a slight effects on a slight effects on the probability of the probability of effecteffect

Dose

Pro

bab

ilit

y of

eff

ect

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Stochastic health effects:Stochastic health effects:methods of detectionmethods of detection

Indistinguishable from “spontaneous Indistinguishable from “spontaneous cancerscancers

No method for identification of the No method for identification of the appearance of this effect of ionizing appearance of this effect of ionizing radiation in individualsradiation in individuals

Increase in occurrence of stochastic Increase in occurrence of stochastic effect can be proved with effect can be proved with epidemiological method only epidemiological method only

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Radiation induced cancer: animal Radiation induced cancer: animal datadata

SufficientSufficient LimitedLimited InadequateInadequate No dataNo data No evidenceNo evidence

(negative)(negative)

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Radiation induced cancer: human Radiation induced cancer: human evidenceevidence

SufficientSufficient LimitedLimited InadequateInadequate No dataNo data No evidence (negative)No evidence (negative)

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Sources of Data on Human Effects Sources of Data on Human Effects of Radiation Overexposureof Radiation Overexposure Occupational exposureOccupational exposure

Early radiologist and medical physicistsEarly radiologist and medical physicists Ra-dial paintersRa-dial painters U-miners, nuclear industry workersU-miners, nuclear industry workers

Medical overexposure Medical overexposure A-bomb victimsA-bomb victims Overexposure due to nuclear weapons Overexposure due to nuclear weapons

test test Accidents Accidents Inhabitants of high natural background Inhabitants of high natural background

areasareas

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Radiation-induced cancer: Radiation-induced cancer: sources of datasources of data

Type or localization of cancerType or localization of cancerPopulation Population

groupsgroupsLeuke-Leuke-

miamiaThyroid Thyroid glandgland

LungLung BreastBreast BoneBone SkinSkin

A-bombA-bomb survivorssurvivors

++ ++ ++ ++

Ra-dial paintersRa-dial painters ++

Early radiologistsEarly radiologists ++

U-minersU-miners ++

Exposed in a Exposed in a nuclear accidentnuclear accident ++

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Multistage cellular development in Multistage cellular development in oncogenesisoncogenesis

Phases of oncogenesis;Phases of oncogenesis; InitiationInitiation PromotionPromotion ProgressionProgression

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Phases of cancer induction and Phases of cancer induction and manifestationmanifestation

In itia tio n Mu ta te d C e lls

Elim ia tio n Re p a ra tio n

Pro g re ssio n

Pre -c a n c e r

No rm a l C e lls

Pro m o tio n

Min im a l C a n c e r

C lin ic a l C a n c e r

Sp re a d in g

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Cancer deaths attributable to A-bombsCancer deaths attributable to A-bombs

In 86572 survivors In 86572 survivors of Hiroshima and Nagasaki of Hiroshima and Nagasaki A-bombing A-bombing 7827 persons died of cancer in 7827 persons died of cancer in

1950-90:1950-90:

ObservedObserved ExpectedExpected ExcessExcess (%)(%)

All tumorsAll tumors 75787578 72447244 334334 (4.4)(4.4)

LeukaemiaLeukaemia 249249 162162 8787 (35.0)(35.0)

All cancersAll cancers 78277827 74067406 421421 (5.4)(5.4)

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

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Radiation-induced bone cancerRadiation-induced bone cancer

Study group:Study group: Persons exposed by Persons exposed by 224224Ra and Ra and 226226Ra Ra

painters of luminous dialspainters of luminous dials radium chemistsradium chemists persons treated with radium salts for a persons treated with radium salts for a

supposedly therapeutic effectsupposedly therapeutic effect

Increased incidence of bone Increased incidence of bone sarcoma was observedsarcoma was observed

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Radiation-induced lung cancerRadiation-induced lung cancer Study group:Study group:

Underground miners working in Underground miners working in Czechoslovakia. Canada, United States of Czechoslovakia. Canada, United States of America and Sweden exposed to America and Sweden exposed to 222222Rn and its Rn and its decay products decay products

The increase in mortality has been The increase in mortality has been correlated with air concentrations of radon correlated with air concentrations of radon in different mines and the duration of in different mines and the duration of exposureexposure

Many additional factors were influencing Many additional factors were influencing the incidence of lung cancerthe incidence of lung cancer

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Radiation-induced liver cancerRadiation-induced liver cancer

Study group:Study group: Patients undergone diagnostic Patients undergone diagnostic

radiology with thorotrast radiology with thorotrast Observations:Observations:

Increased risk of liver tumors and Increased risk of liver tumors and leukemialeukemia

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Thyroid cancer among exposed due to Thyroid cancer among exposed due to Chernobyl accident children of BelarusChernobyl accident children of Belarus

0

1

2

3

4

5

6

inci

denc

e pe

r 10

0000

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997

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SummarySummary This lecture presented materials about This lecture presented materials about

radiation induction of cancerradiation induction of cancer The following topics were covered in the The following topics were covered in the

lecture: stochastic effects (definition, lecture: stochastic effects (definition, description, explanation, methods of description, explanation, methods of detection), latent periods, sources of data for detection), latent periods, sources of data for investigation of stochastic effects (animal and investigation of stochastic effects (animal and human data), observations of radiation-human data), observations of radiation-induced cancers (bone, leukaemia, lung, liver, induced cancers (bone, leukaemia, lung, liver, thyroid), stages and description of thyroid), stages and description of oncogenesisoncogenesis

Comments are welcomedComments are welcomed

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Where to Get More InformationWhere to Get More Information UNSCEAR, Sources and Effects of Ionizing UNSCEAR, Sources and Effects of Ionizing

Radiation, 2000 Report to the General Assembly Radiation, 2000 Report to the General Assembly with Scientific Annexes, United Nations, New York, with Scientific Annexes, United Nations, New York, 20002000

IIAEA AEA Training Course at Emergency Medical Training Course at Emergency Medical Preparedness and Response.Preparedness and Response. Medical Education Medical Education and Inter-Regional Harmonization Program for and Inter-Regional Harmonization Program for Nuclear Accident Preparedness.Nuclear Accident Preparedness. September, 1999, September, 1999, Budapest, Hungary, Training materialsBudapest, Hungary, Training materials

IAEA IAEA Regional Basic Professional Training Course Regional Basic Professional Training Course on Radiation Protection. September-October, 1997. on Radiation Protection. September-October, 1997. Germany, Training materialsGermany, Training materials

IIAEA Training Course at IPSN. Medical Emergencies AEA Training Course at IPSN. Medical Emergencies in Case of Radiological Accidents. November 1998. in Case of Radiological Accidents. November 1998. Training materialsTraining materials