biological effects of radiation

1. Guided By :- Prepared By :-
Dr. Badruddeen Abu Raihan Shams
Associate Professor(Jr. Pharm. D , 2nd
1700100350

2. TOPIC
BIOLOGICAL EFFECTS OF RADIATION

3. Radiation
Radiation can be defined as the transmission of energy
from a body in the form of waves or particles.
Examples include heat or light from the sun,
microwaves from an oven, X rays from an x-ray tube,
and gamma rays from radioactive elements

4. Radiation is not only emitted during radiation therapy, but also
from microwaves, cell phones, computers, and so on. Radiation
is a type of energy that occurs naturally and can even be man-
made. When the radiation is from the Sun or outer space, then it
is called cosmic radiation, and when it comes from minerals in
the Earth it is called terrestrial radiation. 13% of all radiation
present is man-made. 12% is produced by X-ray and MRI
machines, and 1% is produced by nuclear industries. Man-made
radiation is more harmful as compared to natural ones because
it is more concentrated.

5. Types of Radiation
Radiation is often categorized as either ionizing or non-
ionizing depending on the energy of the radiated
particles.
( On the basis of energy of radiated particles )

6. Ionizing Radiation
 Ionizing radiation is radiation that carries enough energy to
detach electrons from atoms or molecules, thereby ionizing
them
 Ionizing radiation carries more than 10 eV energy, which is
enough to ionize atoms and molecules, and break chemical
bonds.
 Ionizing radiation consisting of particles, X-rays, or gamma
rays with sufficient energy to cause ionization in the medium
through which it passes.

7. Non-ionizing Radiation
 Non-ionizing radiation refers to any type of electromagnetic
radiation thatdoes notcarryphoton energytoionizeatoms or
molecules.
 Non-ionizing radiation consists of electric & magnetic fields,
UVrays,infrared, Laser rays,Microwave,Ultrasoundwaves.

8. Mechanism of action
There are two theories exist to understand the mechanism
of action.
 Target theory
 Indirect action theory

9. Target theory
 This theory proposes that radiant energy acts by direct
hits on target molecules within the cells e.g. DNA. This
can lead to Mutation, Genetic or Cancerous
predisposition, Inhibition of cell division, Cell death,
Damage to cell membrane or enzymes.
 Radiant energy, charged particles cause injury with this
method.

10. Indirect action theory
 This theory proposes that the radiant energy exerts its
effect by producing free radicals within the cells e.g. H°,
OH-, H2O2, HO2. There free radicals may interact with
them and can cause damage to cell membrane, nucleic
acids, enzymes and even may cause cell death.
 Radiant energy, gamma and X-rays act by this
mechanism.

11. Biological effects of Radiation
 The harmful effects caused to human beings and other
living beings due to their exposure to radiation is called as
biological effects of radiation.
 High radiation doses tend to kill cells, while low doses
tend to damage or alter the genetic code (DNA) of
irradiated cells.

12. Biological effects of radiation on living cells may result in
three outcomes:
1. Injured or damaged cells repair themselves, resulting in
no residual damage
2. Cells die, much like millions of body cells do every day,
being replaced through normal biological processes; or
3. Cells incorrectly repair themselves resulting in a
biophysical change.

13. Some tissues and tumors are more sensitive to radiation than
other.
 Sensitive tissues: - Lymphoid, hemopoietic, spermatogonic,
ovarian follicle.
 Sensitive tumors: - Leukaemia, lymphoma, seminoma,
dysgerminoma,
 Resistant tissues: - Bones, cartilage, muscles, peripheral
nerves.
 Resistant tumors: - gliomas, sarcomas, melanoma,
osteosarcoma.

14. Effects of Radiation on Cells
Biological effect begins with the ionization of atoms. The
mechanism by which radiation causes damage to human
tissue, or any other material, is by ionization of atoms in
the material. Ionizing radiation absorbed by human tissue
has enough energy to remove electrons from the atoms
that make up molecules of the tissue.
( Ionizing radiation )

15. The following are possible effects of radiation on cells:
• Cells are undamaged by the dose : - Ionization may form
chemically active substances which in some cases alter the
structure of the cells. These alterations may be the same as
those changes that occur naturally in the cell and may have
no negative effect.
• Cells are damaged, repair the damage and operate
normally: - Some ionizing events produce substances not
normally found in the cell. These can lead to a breakdown of
the cell structure and its components. Cells can repair the
damage if it is limited. Even damage to the chromosomes is
usually repaired. After this cell operate normally.
Contin....

16. • Cells are damaged, repair the damage and operate
abnormally : - If a damaged cell needs to perform a function
before it has had time to repair itself, it will either be unable to
perform the repair function or perform the function incorrectly
or incompletely. The result may be cells that cannot perform
their normal functions or that now are damaging to other cells.
These altered cells may be unable to reproduce themselves or
may reproduce at an uncontrolled rate. Such cells can be the
underlying causes of cancers.
• Cells die as a result of the damage : - If a cell is extensively
damaged by radiation, or damaged in such a way that
reproduction is affected, the cell may die. Radiation damage to
cells may depend on how sensitive the cells are to radiation.
Contin....

17. • Selective inhibition of cell proliferation is the most
important effect
• Damage ot cytoplasmic enzymes, macromolecules
and organelles
• Damage to DNA may lead to: -
➢ Oncogenic transformation
➢ Heritable genetic defect to children

18. Effects on organs and systems of
body
Dose of radiation
Acute radiation dose
 An acute radiation dose is defined as a large dose (10 rad or
greater, to the whole body) delivered during a short period of time
(on the order of a few days at the most). If large enough, it may
result in effects which are observable within a period of hours to
weeks.
 Acute doses can cause a pattern of clearly identifiable
symptoms (syndromes). These conditions are referred as Acute
Radiation Syndrome.

19.  Blood‐forming organ (Bone marrow) syndrome :-
(>100 rad) is characterized by damage to cells that divide at
the most rapid pace (such as bone marrow, the spleen and
lymphatic tissue). Symptoms include internal bleeding,
fatigue, bacterial infections, and fever.
 Gastrointestinal tract syndrome:-(>1000 rad) is
characterized by damage to cells that divide less rapidly
(such as the linings of the stomach and intestines).
Symptoms include nausea, vomiting, diarrhea, dehydration,
electrolytic imbalance, loss of digestion ability, bleeding
ulcers, and the symptoms of blood‐forming organ
syndrome.

20. CNS Syndrome :-(>5000 rad) is characterized by damage
to cells that do not reproduce such as nerve cells.
Symptoms include loss of coordination, confusion, coma,
convulsions, shock, and the symptoms of the blood
forming organ and gastrointestinal tract syndromes.

21. Other effects from an acute dose include
➢ 200 to 300 rad to the skin can result in the reddening of the skin
(erythema), similar to a mild sunburn and may result in hair loss due
to damage to hair follicles.
➢ 125 to 200 rad to the ovaries can result in prolonged or permanent
suppression of menstruation in about fifty percent (50%) of women.
➢ 600 rad to the ovaries or testicles can result in permanent
sterilization.
➢ 50 rad to the thyroid gland can result in benign (non-cancerous)
tumors.

22. Chronic Radiation dose
A chronic dose is a relatively small amount of radiation
received over a long period of time. The body is better
equipped to tolerate a chronic dose than an acute dose. The
body has time to repair damage because a smaller percentage
of the cells need repair at any given time. The body also has
time to replace dead or non‐functioning cells with new
healthy cells. This is the type of dose received as occupational
exposure.

23. Some radiation changes are as follows: -
i) Skin
➢ Post irradiation erythema (2-3 days)
➢ Post radiation edema (2-3 weeks)
➢ Epithelial blistering (4-6 weeks)
➢ Chronic radiodermatitis (Months / years)
➢ Skin cancers (years)
ii) Hemopoietic and lymphoid tissue
➢ Severe lymphopenia
➢ Severe neutropenia
➢ Bone morrow depression

24. iii)Lungs
➢ Fatal respiratory failure
➢ Marked pulmonary edema
➢ Radiation pneumonitis
iv)Gastrointestinal tract
➢ Loss of appetite, nausea, vomiting, diarrhoea
➢ Intestinal mucosal edema, hyperaemia, Ulcerations
➢ Intestinal mucosal atrophy, fabrosis.
v)Brain
It is relatively radioresistant in adult males. It shows focal
necrosis only with high doses of radiations.

26. Dose Effects
10-50 rads No obvious effects
50-100 rads Vomiting, Nausea, Fatigue, lymphopenia,
Neutropenia.
100-200 rads Vomiting, Nausea.
200-350 rads Severe gastrointestinal syndrome
350-550 rads GI+ Haeopoietic syndromes Death in 50%
cases
550-750 rads 100% deaths in 6 months
1000 rads Death within days
5000 rads Death within hours to days
Dose wise effects of radiations are as follows

27. Effects of Non-ionizing Radiation
 Laser rays: It may cause damage to lens, bone marrow,
endocrine glands and DNA.
 Microwave: thermal injuries , painful burn , cataracts(due
to exposure of high level of microwaves on eye)
 Ultrasound waves: It may alter nerve transmission.
*****

28. REFERENCES
Dr. Prakash S. Ghadi, Pathophysiology, career publication
(Division of Career Consultants, Nashik), page no: - 166-
170.
www.who.int/ionizing_radiation/about/what_is_ir/en/ind
ex.html.
http://www.srmuniv.ac.in/sites/default/files/downloads/BI
OLOGICAL_EFFECTS_OF_RADIATION.pdf
Christensen DM, Iddins CJ, Sugarman SL (February 2014).
"Ionizing radiation injuries and illnesses". Emerg Med Clin
North Am. Page no: 245–65.
All, E J (1 May 1976). "Radiation and the single cell: the
physicist's contribution to radiobiology". Physics in
Medicine and Biology. Page no: 347–359.