5: Biological Effects Flashcards
What is the annual background dose of radiation that Canadians receive?
1.2 - 3.2 mSv
What is the radioisotope that is found in ALL living creatures?
Carbon-14
How is carbon-14 formed?
Cosmic rays interacting with the atmosphere
What are somatic effects?
Effects experienced by exposed individual (other than reproductive cells)
What are genetic effects?
Passed from parent to child causes by mutations in sperm/egg cells
What is acute exposure?
Exposure to a large dose in a short amount of time
What is chronic exposure?
Irradiation over long period of time at lower intensity levels
What are short term/prompt somatic effects?
Evident short time after exposure (hours, days, weeks)
What are long term/delayed effects?
Don’t become apparent until years, decades or generations after exposure
What are stochastic effects?
Associated with chronic exposure with no known minimum threshold.
(Show up years after exposure, increased levels more likely, do not affect severity/effect.)
What are non-stochastic effects?
Below a known threshold effects do not occur, appear in cases of high exposure levels and become more severe as exposure increases.
What is the ratio of red to white cells?
600:1
Red blood cells carry oxygen where?
Carry oxygen to respiratory organs and collect carbon dioxide to bring back to respiratory organs
White blood cells combat infection, but too many cause what?
Leukaemia
Alpha particles and gamma rays have same amount of what?
Energy
What do alpha particles do inside the body?
Deposit all of its energy in very small volume of tissue.
What do gamma rays do inside the body?
Spread energy over larger volume.
Alpha particles are approximately how much bigger than Beta particles?
7000x bigger
Who is most affected by radiation?
Fetus/embryo
Why are children more affected by radiation?
They’re growing, so more cells are dividing and there’s a greater opportunity to disrupt the process.
What kind of radiation are burns caused by?
Localized acuren exposure to high levels.
Radiation sickness is from what kind of exposure?
Acute exposure.
What happens when one gets radiation sickness?
Entire body absorbs a dose of at least 1 Gy.
(6+ Gy to whole body are not treatable - often lead to death 2 days to several weeks after)
Early symptoms: nausea/vomiting
Higher doses: ulcers, dizziness, hair loss
What is a mutation due to radiation?
Chromosomes containing the genetic blueprint are passed down for generations UNLESS genetic mutation caused by external factor.
What is a genetic mutation?
A permanent change in DNA sequence.
Mutations inherited from a parent if mutation was present in sperm/egg cells.
What are somatic mutations?
NOT passed down to next generations.
Occurred at some point in life due to environments factors OR if mistake was made when DNA replicated itself during cell division.
What are radiation effects from an embryo?
Can occur just after fertilization if woman is exposed while pregnant.
Effects: smaller head/brain size, poorly formed eyes, abnormally slow growth and intellectual disability.
What is the most sensitive period for radiation effects to an embryo?
9th day of the 6th week after conception (organs are developing)
What are cataracts?
Clouding of the lens = image is blurred.
What is the definition of cancer?
Uncontrolled growth of abnormal cells.
Abnormal change in nucleus of a cell initiates uncontrolled, rapid cell multiplication forming malignant tumours.
When do tumours grow?
When normal cells suffer from DNA mutation, multiplying with unusual restrictions.
Cancer from radiation especially affects what organs?
Blood forming organs.
What is the recovery period?
Time required for damage to tissues be repaired by inherent repair mechanisms.
What is the latent period?
Time between initial exposure and when effects become evident.
What happens to people exposed to 5 Sv of acute radiation exposure?
Death to 50% of people within 30 days
What happens to people exposed to 8-10 Sv of acute radiation exposure?
Death to most
What happens to people exposed to 10+ Sv of acute radiation exposure?
Death is certain within an hour
Who is the ICRP and when were they formed?
International Commission on Radiological Protection - 1928
What does the ICRP do?
Provides recommendations based on the current understanding of science of radiation exposure and effects.
ICRP 2010 supports 3 main principles:
- Justification - only use if leads to a positive benefit
- Optimization of Protection - exposure kept to ALARA
- Dose Limitation - max dose must not pose a risk to person greater than working in a safe environment
What is MPD?
Maximum permissible dose - follows recommendations from ICRP, CNSC establishes limits
MPD for non-NEW in 1 year?
1 mSv
MPD for NEW over a year?
50 mSv
For 2 Gy of gamma radiation, what is the weighing factor?
One
For 2 Gy of alpha radiation, what is the weighing factor?
20
What are the main sources of background/natural radiation?
Cosmic radiation (sun/outer space) and terrestrial radiation (radioactive elements in Earth’s crust)
What’s the difference between internal and external exposure?
Internal: ingesting radioactive material and external: exposed to radiation
MPD for a pregnant NEW after she notifies her boss in writing?
4 mSv
Max permissible yearly dose for a NEW on: skin, hands & feet, lens of eye
Skin: 500 mSv
Hands & Feet: 500 mSv
Lens of Eye: 150 mSv
What is LD50?
Approx 5 Sv — acute radiation exposure = death to 50% people exposed in 30 days
0-250 mSv of acute exposure?
No injury evident/biological defects
1-2 Sv of acute exposure?
Radiation sickness
What organs/tissues have highest sensitivity?
Blood forming organs (spleen, bone marrow, lymph nodes) AND sex organs, lens of eye, digestive/respiratory system
What tissues are radiation resistant?
Connective tissues (muscles, tendons, ligaments), fat and bone, nerves and brain
What 2 elements are naturally occurring in the Earth’s Crust?
Uranium and thorium
