Biological effects of radiation
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Ionizing radiation can damage biological molecules and tissues by removing electrons from atoms, breaking molecular bonds. This radiation damage occurs through direct interaction with radiation or indirectly via reactive oxygen species produced by radiolysis of water. DNA is particularly susceptible to radiation damage which can lead to mutations if not repaired. The type and severity of health effects from radiation exposure depends on dose and can include hematopoietic, gastrointestinal and central nervous system syndromes causing acute illness.
Biological effects of radiation
- 1. Biological effects of radiation RAFEEQ
- 2. Ionizing radiation absorbed by human tissue has enough energy to remove electrons from the atoms that make up molecules of the tissue. When the electron that was shared by the two atoms to form a molecular bond is dislodged by ionizing radiation, the bond is broken and thus, the molecule falls apart. This is a basic model for understanding radiation damage.
- 4. Radiation Causes Ionizations of: cells which may affect MOLECULEs which may affect TISSUES which may affect ORGANS which may affect THE WHOLE BODY
- 8. I I S-AT-S I I P P I I S-CG-S I I P P I I S-GC-S I I P P I I S-TA-S I I  DNA is the most important material making up the     chromosome and serve as the master blue print of the cell. DNA takes the form of twisted ladder Sides of ladder are alternating sugar and phosphate groups Branching off from each sugar group is four nitrogen bases,cytosine ,thymine ,adenine and guanine. Information carried by DNA is detrmined by the order of the base.
- 9. Relative Sensitivity of Cell and Tissue Types  Lymphocytes  Hematopoietic (Blood Forming)  Reproductive cells  Intestinal Epithelium  Skin  Nerve Cells  Muscle Tissue  Bone  Collagen
- 10. Cells tend to be radiosensitive if they have three properties: » Cells that have high division rate (the time between divisions) » Cells that have long dividing future (immature cells in early cellular life) » Cells that are unspecialized (cells which have a widely diverse future)
- 11. Because the human bodyis contains 80% water molecules, radiation interaction with water is the principal radiation interaction in the body. The ultimate damage occurs to the target molecule, DNA, which controls cellular metabolism and reproduction.
- 12. INTER ACTION WITH ATOM  When radiation interact with target atoms energy is deposited resulting ionisation or excitation  There are two interactions 1. DIRECT ACTION 2.INDIRECT ACTION Direct action :in this radiation directly interact with DNA and cause DNA damage. Indirect action:radiation interacts with water molecules causing  radiolysis and hence the formation of free radicals,which is toxic to the tissues
- 15.     Indirect Action in Detail H2O -> H2O+ + eH2O+ is an ion (electrically charged) H2O+ is also a free radical  unpaired electron in outer shell  very reactive  H2O + H2O +-> H3O+ + OH·  OH· (hydroxyl radical) is very reactive  OH * + OH * --------------------ïƒ H2O2 
- 16. Radiation Induced Decomposition of Water Within a Cell Most abundant molecule within humans: Water H 2O + H2 Incoming Radiation H H 2O + OH eWATER - Ho HO2 H2O2 OH o Production of free radicals within the cell can result in indirect effects
- 18. DNA damage  Radiation and ions from irradiation can alter the order of the base ,therefore causing the mutation or cell death.  When DNA is broken hydrogen bonds between the bases are broken and they may rejoin in different orders.  In human cells, we can have as many as a million individual instances of damage to DNA per cell per day.  It is remarkable that DNA contains codes that check whether the DNA is damaged or can repair itself.  It is like an auto check and repair mechanism. This repair ability of DNA is vital for maintaining the integrity of the genetic code and for the normal functioning of the entire organism.
- 19. Single strand break  Most likely efficiently repaired, with little, if any , long term consequences to the cell. Double strand break Difficult for the cell to repair. They show reasonable corelaiton with cell killing. If repair does not take place, the DNA chains can separate, with serious consequence to the life of the cell.
- 20. SINGLE STRAND BRAKES RELATIVELY INCONSEQUENTIAL IN TERMS OF CELL KILLING. WILL BE EFFICIENTLY REPAIRED , WITH LITTLE, IF ANY, LONG TERM CONSEQUENCES TO THE CELL
- 21. DOUBLE STRAND BRAKES VERY DIFFICULT FOR THE CELL TO BE REPAIRED. CAN LEAD TO CELL KILLING. IF REPAIR DOESN’T TAKE PLACE, THE DNA CHAINS CAN SEPARATE. SERIOUS CONSEQUENCE TO CELL LIFE.
- 22. Base damage  The loss or a change of a base on the DNA chain results in the alteretion of the base sequence. Base sequence stores and transmits genetic information. It has nmajor consequences. Loss or change of base is considered a type of mutation.
- 25. Radiation syndrome  Hematopoietic Syndrome  •Prodromal Stage: Mild symptoms appear within a few hours and last for several days  •Latent Period: May last up to 4 weeks  •Manifest Illness: Vomiting, diarrhea, fatigue and fever – Decline in blood cells – Recovery in 2 to 4 weeks…May last up to 6 months  •Possible death due to infection, dehydration or hemorrhage
- 26. Gastrointestinal Syndrome •Prodromal Stage: Vomiting and diarrhea occur within hours and last up to one day •Latent Period: Lasts 3-5 days •Manifest Illness: Nausea, vomiting and diarrhea – Worsens to bloody stools •Death within 4 to 10 days after exposure primarily due to intestinal cell damage – Also damage to blood-forming tissue results in hemorrhaging and dehydration.
- 27. Central Nervous System Syndrome •Prodromal Stage: Severe nausea and vomiting within a few minutes – Nervousness, confusion, burning skin, vision loss, possible loss of consciousness •Latent Period: May last up to 12 hours, or not at all •Manifest Illness: Disorientation, loss of muscle control, breathing problems, seizures, coma •Death within a few days of exposure – due to increased fluid in brain (pressure) – Death occurs before hematologic and gastrointestinal symptoms appear
- 28. Total Body Response to Radiation  Acute Radiation Syndrome – full body exposure given in a few minutes.  3 stages of response: 1. Prodromal Stage: NVD stage (nausea, vomiting, diarrhea) 2. Latent Period: Feels well while undergoing biological changes 3. Manifest Stage: Full effects felt, leads to recovery or death
- 29. 3 Acute Radiation Syndromes Early Effects • • • Bone marrow syndrome: results in infection, hemorrhage & anemia Gastrointestinal syndrome: results in diarrhea, nausea & vomiting, fever Central nervous syndrome: results in convulsions, coma, & eventual death from increased intracranial pressure. CNS least sensitive in ADULTS – MOST sensitive in the FETUS
- 30. 3 Acute Radiation Syndromes Early Effects • • • Bone marrow syndrome: results in infection, hemorrhage & anemia Gastrointestinal syndrome: results in diarrhea, nausea & vomiting, fever Central nervous syndrome: results in convulsions, coma, & eventual death from increased intracranial pressure. CNS least sensitive in ADULTS – MOST sensitive in the FETUS
- 31. Total Body Response to Radiation  Acute Radiation Syndrome – full body exposure given in a few minutes.  3 stages of response: 1. Prodromal Stage: NVD stage (nausea, vomiting, diarrhea) 2. Latent Period: Feels well while undergoing biological changes 3. Manifest Stage: Full effects felt, leads to recovery or death
- 32. DOSE LIMITS  State Annual Limits  Occupationally Exposed Workers 5 rem/yr whole body, gonads  15 rem/yr lens  Non-occupationally exposed worker (and the general public) 0.1 rem /yr (100 mrem)
- 33.  Limit embryo/fetus dose equivalent to 500 mrem (0.5 rem) total.  2. Once a pregnancy becomes known limit embryo fetus dose equivalent to 50 mrem per month, excluding medical exposure
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