3. BIOLOGICAL EFFECT OF IONIZING RADIATION_RPO NOV 2023.pptx

BIOLOGICAL EFFECTS OF IONIZING RADIATION Mohd Khalid Matori Radiation Metrology Group Radiation Safety & Health Division Malaysian Nuclear Agency (Nuclear Malaysia) Quiz Objective Question 1. When lead aprons are employed, personnel monitoring devices should be worn: A. Outside the apron level of...

BIOLOGICAL EFFECTS OF IONIZING RADIATION Mohd Khalid Matori Radiation Metrology Group Radiation Safety & Health Division Malaysian Nuclear Agency (Nuclear Malaysia) Quiz Objective Question 1. When lead aprons are employed, personnel monitoring devices should be worn: A. Outside the apron level of the waist B. Inside or outside the apron level of the waist C. Outside the apron level of the neck D. Inside the apron level of the neck Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre STATISTIK KELULUSAN PEPERIKSAAN PERSIJILAN PEGAWAI PERLINDUNGAN SINARAN (PPS) BAGI JANUARI - OKTOBER 2017 Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Application of Radiation in Malaysia Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Learning Objectives i. To understand the mechanisms of radiation injury ii. To identify factors that may modify radiation effects iii. To provide understanding on biological and health effects of Ionizing Radiation iv. Assess and compare risks of radiation exposure Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre CONTENT S • Ionizing Radiation (IR) • Factors that may modify radiation effects  Physical Factors  Biological factors  Environmental factors • Biological Effects of Ionizing Radiation  Hereditary effects  Somatic effects • Health Effects of Ionizing Radiation  Stochastic effects  Deterministic effects • Acute Radiation Syndrome (ARS) • Radiation Injury Mechanism • Risk of Radiation to Pregnant Women • Summary Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre WHAT IS IONIZATION?  Ionization is the physical process of converting an atom or molecule into an ion by removing charged particles such as electrons Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre WHAT IS IONIZING RADIATION?  Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions  Examples of ionizing radiation (IR) are; I. Electromagnetic (EM) radiation (gamma and x-ray) II. Particulate radiations (alpha, proton, neutron, beta, and electrons) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre DO WE WANT TO BE LIKE THIS???? Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre INTRODUCTIO N  The final concern of radiation hazard is its effects on living things.  The biological effect of Ionizing radiation begins with the ionization of atoms of the cell molecules and culminates with possible damage to the individual  Damage cells may eventually cause cell death or induce the abnormal cell (mutation)  Biological Effects depend on the type, energy and dosage of the radiation, cellular type and stage etc.  There are repair mechanisms constantly present to repair cellular damage – including chromosome damage. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre BASIC STRUCTURE OF LIVING THINGS  Basic living things are make up of atoms (Eg., carbon, hydrogen, oxygen)  Atoms combined to make up molecules (Eg. protein, fats, carbohydrates, vitamins etc)  The molecules make up the human cells *The biological effect of IR begins with the ionization of atoms of the cell molecules  These cells make up tissues and organs Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre HUMAN BODY Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre LEVELS OF RADIATION EFFECTS Molecular Level Cellular Level Organ Level Whole Body Level Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre WHAT HAPPENS WHEN A RADIATION PASSES THROUGH YOUR The DNA inside yourBODY? body cell can be damaged Exposed to Radiation Our body consists of about 60 billion cells, in which the cells repeat to divide. And in the cell, there is the DNA. Radiation damages the DNA cell Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre WHAT HAPPENS TO THE DAMAGED DNA? Ionization by Radiation (electrolytic Development of DNA dissociation) DNA strand break Repair Complete Recover normal function Incomplete Possibility of future somatic/ hereditary effects Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre HISTORY OF IR RELATED TO BIOLOGICAL EFFECTS Sequence of Events 1895 Roentgen discovered X-ray for diagnostic purpose 1896 Becquerel discovered Radioactivity materials 1897 69 cases of skin injuries due over-exposure to X-rays 1900 Onward - First skin radiation induced cancer reported (1902) - evidence IR cause sterility, reduction in WBC, illnesses and death - Atomic bomb in Nagasaki and Hiroshima can obliterate mankind Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1900s: NEW DANGERS COME WITH DISCOVERIES/USES  69 cases of x-rays related injuries incl. repeated exposure in medical field  Edison co-workers died due to tumor-induced x-rays exposure in R&D,  Radium paint (glowing in the dark) killed 9 women in factories making watches in US  Patients drank radioactive radium water to treat gout  Misuse of nuclear technology as weaponry Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1900s: NEW DANGERS COME WITH DISCOVERIES/USES Radium girl a dial painter who suffered from radium induced sarcoma of the chin Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre MEDICAL X-RAYS – 1900s SOURCES OF INFORMATION FOR RADIATION EFFECTS  Occupational exposures (physicians & radiologists, uranium miners, workers in nuclear plants etc.)  Medical exposures – (radiation therapy etc.,)  Atomic bomb victims & survivors  Nuclear accidents  Background radiation (India & Brazil) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre FACTORS THAT MAY MODIFY RADIATION EFFECTS A. Physical Factors B. Biological factors C. Environmental factors Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre A. PHYSICAL FACTORS - which affect cells sensitivity to radiation 1. Types of radiation (particulate versus electromagnetic radiation) 2. Radiation dose (or total dosage) 3. Dose rate 4. Dose fractionation Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1. TYPES OF RADIATION EXPOSED  Radiation with high LET values cause more damage (eg. Alpha and neutron vs gamma and x-rays)  Radiation with deeper penetration eg. gamma and x-rays cause damage to internal organs compared to alpha and beta *In dosimetry, linear energy transfer (LET) is the amount of energy that an ionizing particle transfers to the material traversed per unit distance. It describes the action of radiation into matter. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 2. TOTAL RADIATION DOSAGE RECEIVED  The higher the dose received, the higher the likelihood of health effects  Partial body irradiation will usually results in milder effects on the whole body compared to a uniform irradiation of whole body for the same dose Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 3. DOSE RATE RECEIVED  If the dosage occurs over a number of days or weeks, the damage are often not as serious if a similar dose was received in a matter of minutes  Examples, - 10 Sv to whole body in short time delivery (acute radiation exposure) cause 100% death - 10 Sv in fractionated dose of 5 Sv within 48 hours cause <100% death - 10 Sv in small dose for over 50 years (chronic radiation exposure) cause no acute effect Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 4. DOSE FRACTIONATION  The same radiation rate but not all of them at one time, our body can repair the damage Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre B. BIOLOGICAL - Factors which affect cells sensitivity to radiation 1. Types of cells exposed 2. The age of the individual exposed 3. Part of the body exposed Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1. TYPES OF CELL  Cells are more sensitive if at high division rate  The higher the metabolic rate in a cell, the lower its resistance to radiation  Cells tend to be more sensitive if they are nonspecialised (eg . Skin, hair, fibroblast etc.)  Well nourished cells, or cell with a high level of oxygenation are more sensitive  Highly specialised and fully differentiated cells such as nerve tissue and muscle are least sensitive to radiation Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre The sensitivity of different types of cells in decreasing order  Lymphocytes (highly sensitive) - Found in spleen & lymph nodes to combat infection  Basal cells (high)  Actively dividing cells of the gonads, bone marrow, skin and the alimentary canal  Alveolar cells & bile duct duct cells (intermediate)  Alveolar cells absorb oxygen. Bile duct provide important enzyme  Endothelial cells & heart cells  will impair normal function of organ  Connective tissues & hepatocytes  Muscle & nerve cells (most resistant) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre The sensitivity of different types of cells in decreasing order Lymphocyt es Basal cells Alveolar cells Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre The sensitivity of different types of cells in decreasing order Endothelial cells Muscle & nerve cells Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 2. THE AGE OF THE INDIVIDUAL EXPOSED • As a person ages, cell division slows and the body is less sensitive to the effects of ionizing radiation • Radiation has more detrimental effects on children than adults Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 3. PART OF THE BODY EXPOSED • Extremities such as hands or feet are able to receive a greater amount of radiation with less resulting damage than blood forming organs housed in the torso Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre C. ENVIRONMENTAL - Factors which affect cells sensitivity to radiation  The presence of radiation sensitizers and protectors Eg. Oxygen concentration and the presence of various chemical modify effect of radiation Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Factors Factors That That May May Modify Modify Radiation Radiation Effects Effects Factors affecting CELLULAR responses Physical Factors Biological Factors Types of cells Type of radiation (LET, RBE), dose, dose rates, dose fractionation Activeness in cell division Stages in the cell cycle *RBE - relative biological effectiveness Environmental Factors Radiation Sensitizers and protectors, OER * OER - Oxygen Enhancement Ratio Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Human cell Cytoplasm - fluid-like substance where metabolism takes place, 75% water Cell membrane - control uptake/output of soluble substance Nucleus - DNA, Chromosomes and genes critical & strategic role in cell functions Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre RADIATION EFFECTS ON CELL NUCLEUS  Most radiosensitive part of the cell (difficult to fix a dose)  Inhibits the ability of the cell to divide by affecting the DNA and RNA Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre BIOLOGICAL EFFECTS OF IR  The biological effects of ionizing radiation on people may be divided into: 1. Hereditary effects (Kesan kebakaan) 2. Somatic effects Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Biological Biological Effects Effects (cont.) (cont.) Deterministic Effect SOMATIC Stochastic Effect BIOLOGICAL Dominant Hereditary Recessive Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1. HEREDITARY (GENETICS) EFFECTS OF IR  Hereditary effects affect the descendants of the exposed individuals  Significant only if the gonads (containing sperms/eggs) are irradiated  Studies has indicated that Genetic mutations can be passed on to all future generations  The child will inherit the properties of the damaged genes from the parents, grandparents, and even great-grandparent Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 2. SOMATIC EFFECTS  Somatic Effects are those effects experienced by the exposed individual Eg. Skin burn, hair lost, sterility etc.  Somatic cells are those cells in your body other than the reproductive cells  Depending on the dose exposure received, somatic effects can be divided into two; a). SHORT-TERM EFFECTS b). LONG TERM EFFECT Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre A. SHORT TERM OR PROMPT SOMATIC EFFECTS • Effects can be seen or felt in a short period of time (for example, 1 week) after acute radiation exposure • For example, skin inflammation results from acute exposure to high ionizing radiation (These effects are also deterministic in that they have a more or less a threshold below which they do not occur) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Patient A - Day 26 Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Radiation induced Angiosarcoma of the Breast Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre B). LONG TERM OR DELAYED SOMATIC EFFECT  Its long-term effects include cancer Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre HEALTH EFFECTS OF IONIZING RADIATION  Can be divided into two categories:1. Stochastic effects 2. Deterministic effects (Non-stochastic) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1. STOCHASTIC EFFECTS  Effects that occur by chance that is probabilistic in nature  Health effects which can occur at any level of radiation exposure i.e no threshold dose  Probability of its occurrence is proportional to the dose received  Usually associated with chronic radiation exposure (long- term effects)  Eg. Cancers and genetic effects Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Stochastic Stochastic Effect Effect Carcinogenesis Carcinogenesis -- The Theprocess processby bywhich whichnormal, normal,healthy healthycells cellstransform transforminto intocancer cancer cells cells  Carcinogenesis is an example of somatic stochastic effect.  Carcinogenesis may:  Occur after low dose exposure; and  The probability of malignancy increases with increase in dose.  In man there is a latent period between initiation and expression of effects. Latent period is about 8 years for induced leukemia and 2-3 time longer for solid tumor (eg lung and breast cancers).  Stochastic effect is influenced by LET and dose rate. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre CANSER CANSER RISK RISK ESTIMATES ESTIMATES Estimates of probabilities of occurrence for various types of cancer due to exposure to radiation Cancer Type Bone Marrow Bone surface Lung Thyroid Breast Colon TOTAL Probability of Fatal Cancer, 10-4 Sv-1 50 5 8 20 85 85 cont. … ICRP gave the value of 0.6 x 10 -2 Sv-1 year-1 for the risk of genetic effects due to exposure to radiation Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Risk Risk Estimates Estimates (cont.) (cont.) Cancer Type Stomach Bladder Oesophagus Liver Skin Gonad Others TOTAL Probability of Fatal Cancer, 10-4 Sv-1 110 30 10 50 2 30 15 500 x 10-4 Sv-1 Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre STOCHASTIC STOCHASTIC EFFECT EFFECT -- Hereditary Hereditary  Occurs in germinal cells of the gonads.  Radiation induces changes in genetic information (through mutation or chromosomal aberrations) and subsequently expressed in the next generation.  Stochastic hereditary effect may be divided into different categories based on severity of genetic effects.  Dominant mutation: fatality may be expressed in the first generation.  Recessive mutation produces less effect to the first generation but more towards increasing the content of genetic damage in the general genetic pool. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre EFFECTS OF RADIATION ON HUMANS -Stochastic Effects Probability of Occurrence Dose Stochastic Dose Response Curve Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 2. DETERMINISTIC EFFECTS  Formerly known as Non-stochastic Effects  Severity of its effects is directly proportional to the size of the dose received  Has threshold dose below which they do not occur  Associated with acute radiation exposure  Eg. Erythema, skin burn, cataract formation, sterility, radiation sickness and death Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre EFFECTS OF RADIATION ON HUMANS -Deterministic Effects Threshold Threshold Dose dose Deterministic Dose Response Curve Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Example Deterministic Effects • For men, 2.5 Gy of radiation exposure to the testes will cause temporary sterility for 1-2 years • For women, 0.5 Gy exposure to the ovaries will cause temporary sterility and 4 Gy permanent sterility • Some of genetic damage – anemia, uncontrollable limb movements, eye cancer, mental deterioration, Down’s syndrome, muscular dystrophy and others Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Radiation Burn Skin graft 3 wk 4wk 11wk 13wk >21wk Pictures from Dr. Makoto Akashi Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Deterministic vs Stochastic Effects  Deterministic effects:  There exist threshold levels for deterministic effects.  Severity of its effect is proportional to the dose received.  Stochastic effects:  Occurrence of effect is probabilistic in nature. Example: cancer.  Probability of its occurrence is proportional to the dose received.  Threshold level of radiation dose does not exist for stochastic effect. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Stochastic Effect Health Effects of IR Deterministic Effect Health Health Effects Effects of of IR IR Partial Body Exposure - Eg, sterility, skin burn etc Whole body exposure - BM, GI and CNS syndrome Carcinogenic Carcinogenic effect effect (Stochastic (Stochastic effect) effect) Genetic Genetic Effects Effects Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre ACUTE RADIATION SYNDROME (ARS)  ARS, or radiation sickness, refer to the symptoms of radiation injuries due to acute radiation exposure  Radiation sickness include nausea, diarrhea, and vomiting due to extreme sensitivity of GI tract to high dose of radiation  Acute vs Chronic Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre ACUTE ACUTE RADIATION RADIATION SYNDROME SYNDROME (ARS) (ARS) ….CONT ….CONT • Caused by acute high dose exposure (> 0.5 Sv) to the whole body. • Usually due to external exposure. • The severity of the symptoms and the speed of onset after exposure are good indicators of the degree of radiation damage Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Acute Exposure to High Levels of Radiation Whole body Dose 0 – 250 mSv 250 – 1,000 mSv 1,000 – 3,000 mSv 3,000 – 6,000 mSv 10,000 mSv and higher Probable Effect No detectable injury Slight blood cell changes, possible nausea, serious effects unlikely. Nausea, vomiting, possible fatality but unlikely for healthy individuals Injury and disability certain, death likely for 50% of people within 60 days. Fatal to all people Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 4 4 STAGES STAGES IN IN ARS ARS 1. Prodromal Syndrome:  Classic symptoms include nausea, vomiting, possibly diarrhoea occurring within minutes days following exposure. Symptoms last from minutes - several days. 2. Latent Stage:  Where patient looks and feels healthy for few hours - weeks. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 4 4 STAGES STAGES IN IN ARS ARS (cont.) (cont.) 3. Manifest illness Stage:  Depends on the specific radiation syndrome (BMS, GIS, CNSS). Illness last between hours – months. 4. Recovery or Death Stage:  Patient either recovers or dies.  In case of CNSS there is no recovery and death within days of exposure. Recovery may occur for BMS although the LD30/60 is about 2.5 - 5 Gy. LD - Lethal Dose Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre ARS IS DIVIDED INTO 3 TYPES 1.Bone Marrow (BM) Syndrome; 2.Gastrointestinal (GI) Syndrome; and 3.Central Nervous System (CNS) Syndrome Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Acute Radiation following acute exposure to low LET uniform whole body radiation of human Syndrome being (ICRP #60) Whole body absorbed dose (Gy) 3-5 5-15 >15 Radiation syndrome Bone Marrow (BM) Syndrome Gastrointestinal (GI) Syndrome Central Nervous System (CNS) Syndrome Time of death after exposure (days) 30-60 10 – 20 1-5 Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1. Hematopoietic /Bone Marrow Syndrome Syndrome occurs following acute exposure to dose 3 to 5 Gy. • • Mild symptom may occur as low as 0.3 Gy • Syndrome is caused by damages to the blood system and blood stem cells • Affects the production of white blood cells – Leukopenia – decrease ability to fight infection • Lowered platelet count causes hemorrhaging and slowing of the healing process • Death will occur after a few weeks (4-8 weeks) after exposure due to damage or death of the bone marrow, spleen and lymphatic tissues • Symptoms include nausea, vomiting, paleness, internal bleeding, fatigue, bacterial infection and fever Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 2. Gastrointestinal (GI) Syndrome  Full syndrome usually occurs following an acute total body gamma dose exposure of 5 to 15 Gy  Caused damages to the gastro-intestinal system  Affect the GI – Kill and stop the production of new epithelia cells of intestines.  Death will occur within one to two weeks after exposure due to excessive bleeding and destruction of the GI mucosa.  Symptoms appear in few hours - Patient will experience melaena (diarrhea with blood), nausea, vomiting, dehydration, bleeding ulcers, electrolyte imbalance, loss digestion ability and symptoms of bone marrow syndrome Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 3. Central Nervous System (CNS) Syndrome  Syndrome occur with dose exposure > 15 Gy  Death due to damages to central nervous system and heart muscle  Will lead to unconsciousness within minutes after exposure and death can result within hours to several days  Symptoms – Convulsion, motor incoordination, coma, & symptoms of GI and BM syndromes  Prognosis is 100% death within 1-5 days Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Radiation Radiation Injury Injury Mechanism Mechanism • Radiation effects begins at the physico-chemical level in cells. • Interaction of radiation with water is the main basis for biological effects. • Two type of radiation interactions:  Direct and  Indirect interactions • DNA is the primary radiation target. • Depending on the dose received by the cells, radiation can alter cell’s characteristics and functions, and may cause cell death. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre The Mechanism of Radiation Injury • • The main effect is caused by the alteration of DNA structure in human chromosome (mutation) The detrimental effect is either directly or indirectly Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 1. Direct Action • Ionizing radiation can cause excitation, ionisation and breakage of molecules such as DNA helix • Produced when the primary (initial) interaction of radiation is with the target atoms in the cell such as those in the DNA • 30% • Dominant with high LET radiation (alpha, neutron) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre 2. Indirect Action • Most common mode of injury (70%) • Interaction of radiation with water is the main basis for biological effects since cells contain almost 75-80% water • Formation of very reactive free radicals which can chemically attack target molecules in cells, such as DNA • Occurs with the dissociation (ionization) of water molecules in cells • Dominant with low LET radiation (x-ray, gama) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre (Indirect Action) (Direct Action) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre a.Initial Physical Stage • Ionization of water by radiation • Production of high speed electrons and leaving behind positively charged water molecules H2O H2O+ + e- Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre b. Physio-chemical stage • Interactions of the ions with water molecules produce new products H2O+ H+ + OH• (free radical) H2O + e- H2OH2O- H• + OHOH• + OH• H2O2 (hydrogen peroxide, oxidizing agent, can affect cells not damaged by radiation) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre c. Chemical stage • The free radicals attack the molecules which form the chromosomes eg., break the DNA helix Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre d. Biological stage • The chemical reactions can cause early death of cell, prevention or delay of cell division, or a permanent change which can be passed on to the daughter cells Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Effects on DNA from low LET radiation Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Effects on DNA from high LET radiation Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Chromosomal Structure due to Exposure to Gamma Radiation Normal Cell Cell receiving >50mSv Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre RISK OF RADIATION TO PREGNANT WOMEN Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Exposure to Zygote of pregnant women  Exposure of embryo aged 8 days - death & miscarriage. Estimated risk is 100% at 1 Sv  Embryo aged 9-15 days - mental retardation & physical disability. Estimated risk is 50% per every Sv  Exposure of fetus aged 8-15 weeks - reduction of IQ at the rate of 30 points per every Sv  Exposure of fetus to radiation at 16 weeks & above disturbance of growth of child, increase risk of leukemia/tumor/cancer. Estimated risk of 2% for each Sv  Risk faced by children to cancer as a result of continues exposure is estimated to be 2.8x 10-2 per Sv Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Job Exposure of Fertile Women • NCRP - women who can get pregnant suggested not to receive radiation at work place exceeding 0.03 Sv (30mSv) as compared to radiation workers of 0.05 Sv (50 mSv) per year • For safety of fetus - 10 days rule - women who can get pregnant are allowed to undergo diagnostic radiology procedure/radiotherapy in the lower abdomen (inc. pelvis) only on the first 10 days after of onset menses (where probability of getting pregnant is minimum during this period) NCRP - The National Council on Radiation Protection and Measurements Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Effect of X-rays on Pregnancy (200 R) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Abnormalities in Experimental animal and human due to exposure to IR Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre SUMMARY OF RADIATION EFFECTS RADIATION EXPOSURE Chronic Exposure Acute Exposure Late Effects Early Effects Erythema Radiation Sickness Sterility Hereditary Effects Cataracts Cancer Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre CONCEPTS OF BIOLOGICAL EFFECTS OF IR : 1. IR produces chemically active charged and uncharged molecular fragments called ions (and free radicals) in material it penetrates, including human tissue 2. The biological effects of IR depend principally on the radiation dose or energy absorbed, the type of radiation, and the type and volume of biological cells exposed 3. There are two general categories of biological effects from ionizing radiation: somatic effects and hereditary effects 4. There are two categories of health effects from IR: Deterministic effects and Stochastic effects 5. No level of radiation exposure greater than zero can be considered completely without risk Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre RISK COMPARISON Cause life expectancy lost Alcohol 1 year Smoking 20 cig./day 6 year Natural hazard 7 days 15% O/weight 2 year Accidents 207 days Occupational exp. 51 days (3mSv/y) Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre TIPS Objective Question 1. Which of the following is the most sensitive to ionizing radiation? A.Fetus B.Child C.Adolescent D.Adult 2. Stochastic effect is…. 3. The degree of radiation injury on an individual depends on the followings EXCEPT… 4. The organ of the human body which is directly related to genetic effect when exposed to radiation is…… 5. Factors effecting somatic effects are …… i. total dose ii. Rate at which dose is administered iii. Part of the body irradiated iv. Age of individual A. i, iii and iv only B. ii, iii and iv only C. i, ii, iii and iv D. i, ii and iii only Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre TIPS Objective Question 6. The system of the body which is most sensitive to radiation exposure? A.Blood B.Reproductive C.Nervous D.Respiratory (Lungs) 7. Below are Acute Radiation Syndrome (ARS) EXCEPT? A.Bone Marrow Syndrome B.Gastrointestinal Syndrome C.Central Nervous System Syndrome D.Down Syndrome Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre TIPS Subjective Question 1. a) List three factors that can modify radiation effects? (3 marks) b) How does the type of radiation plays a role in modifying radiation effects? (5 marks) c) What are the terms used to explain radiation effect to human? (2 marks) Answer 1. a) i) Type of radiation ii) Dose and dose rate iii) Part of the body that is exposed b) Types of radiation is a factor that modify the radiation effects. Characteristic of alpha, beta, gamma and X-ray, and neutron will modify the radiation effect. Radiation with higher RBE and LET values will causes greater damage than those with lower RBE and LET. Example of high LET radiations are alpha and neutron. Examples of low LET radiations are X-rays and gamma rays. c) The term used to explain radiation effect to men are stochastic and non-stochastic or deterministic. Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre TIPS Subjective Question 2. a) What are the terms used to explain radiation effect to human? b) Choose one of the types and briefly describe its relation in term of late and acute effects of radiation exposure. 3. a) List three syndromes that can caused fatality and three nan-fatal acute exposure due to ionizing radiation b) Briefly describe one of the syndromes and its relation to exposure. 4. a) Why is the interaction of ionizing radiation with water molecules important in describing the radiation effect? b)Why is the indirect interaction of X and gamma radiation to cell more important as compared to direct interaction Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre TIPS Book to refer : Ismail Bahari & Mohd Yusof Mohd Ali, Managing Radiation Safety : Guide For Radiation Protection Officer, Mc Graw Hill Education Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre Thanks khalid_matori@nm.gov. my Pusat Latihan Nuklear Malaysia / Nuclear Malaysia Training Centre