Ionizing radiation 1

Question 1

how much of ionizng radiation is natural ?

Answer 1

> 80% - of what we are exposed to daily

Question 2

what are different sources of radiation exposure ?

Answer 2

radon 
cosmic rays
terrestrial
internal 
medical 
other

Question 3

what is radon ?

Answer 3

causes most of the natural exposure

its a gas present in rocks, soil, water and air

Question 4

how are we exposed to cosmic rays ?

Answer 4

produced in the galaxy and from the sun

Question 5

when does your exposure to cosmic rays increase ?

Answer 5

at higher altitudes

• pilots are exposed to more of them
• pilots are thought to be exposed to about 20mSv per year

Question 6

what is ionizing radiation ?

Answer 6

its a physical toxic agent

Question 7

what is an example of a food containing lots of radioactive material ?

Answer 7

bananas because they contain lots of potassium

Question 8

what does it mean by internal exposure to radiation ?

Answer 8

we are radioactive

• we contain carbon-14 and K-40
• sufficient amounts in the body to account for 10% of daily exposure

Question 9

what is uranium-238 principally found in and what does it degrade into ?

Answer 9

principally in rock

converted to Ra-226 then to Ra-222 then to lead

Question 10

when were x-rays discovered ?

Answer 10

1895 by roentgrn

Question 11

what did becquerel observe ?

Answer 11

in 1896 he noticed that uranium salts emit radiation

- due to radioactive isotope

Question 12

what did bergonie and tribondeau discover in 1906 ?

Answer 12

stem/immature cells are more sensitive than fully differentiated cells
younger tissues and organs are more radiosensitive than their adult equivalents
tissues and organs with the highest metabolic activity are the most radiosensitive
cells with the fastest rates of division are most sensitive- epithelial cells

Question 13

what did workers with ionizing radiation discover ?

Answer 13

workers discovered that radioactive material could cause harm when handled
- they causes red sore skin and blisters and it also damaged their eyes

Question 14

when are you most sensitive to ionizing radiation ?

Answer 14

most sensitive as a fetus, then your sensitivity decreases to adulthood and then sensitivity increases in the elderly

Question 15

what did muller show ?

Answer 15

1927- showed that ionizing radiation is mutagenic in fruit flies

Question 16

what was discovered in the 1940s?

Answer 16

discovery that ionizing radiation results in free radical generation via hydrolysis of water and that oxygen is a radiosensitizer
- proved the effects of ionizing radiation are caused indirectly

Question 17

what happened in 1945?

Answer 17

atomic bombs - caused 100000 deaths

Question 18

what happened in the 1950/60s?

Answer 18

atmosphere testing of nuclear weapons and windscale fire

- windscale fire was when the military reactor caught fire and released a lot of radiation

Question 19

what happened in 1970/80s?

Answer 19

3 mile island and chernobyl
- chernobyl disaster was when the reactor exploded and release a lot of radiation, 50 people died

• russian authorities didnt provide antidote potassium iodide quickly enough

Question 20

what can radium paint do ?

Answer 20

it glows in the dark so was used to paint the dials of watches

• used to produce luminous instruments in WW1
• it contains Ra-226 which gives off alpha particles which damage osteoblasts
• women using this paint in ww1 in the us used to use fine paint brushes which they licked to produce a fine tip and this caused them to suffer serious necrosis of jaw bone and many suffered cancer later in life
• radium concentrates in bone

Question 21

what is 1 gray (Gy)?

Answer 21

1 joule of energy absorbed per kg of tissue

Question 22

what varies with radiation type ?

Answer 22

biological effects

- same absorbed dose of x-rays and alpha particles produces different levels of damage

Question 23

what tissue is more likely to absorb ionizing radiation ?

Answer 23

dense tissue such as bone

Question 24

how much more damaging are alpha particles compared to x-rays ?

Answer 24

20x more damaging per unit of absorbed dose

Question 25

what affects the biological damage ionizing particles can cause ?

Answer 25

size- the bigger it is the more likely it will interact with particles in cells
kinetics- slower it is the more likley it will interact with particles in cells

therefore alpha particles more readily interact with particles in cell - they are only dangerous to use internally because they cant penetrate the skin due to the dead cells (striatum corneum )

Question 26

what does it mean by linear energy transfer?

Answer 26

probability that a collision will occur

Question 27

what is 1 sievert (Sv)?

Answer 27

dose that produces the same biological effect as 1 Gy of x-rays

Question 28

what distances do alpha particles travel before they cause damage ?

Answer 28

about 4 cm in the air before they collide with another particles and disperse energy
in the body it travels ony 40 micrometers before interactionn

Question 29

what are the 2 components of ionizing radiation ?

Answer 29

electrical magnetic radiation-

Question 30

what is 1 Sv equal to ?

Answer 30

1Gy * Wt

• x rays, gamma rays and beta particles have a Wt=1
• protons have a Wt=2
• neutrons have a variable Wt between 5-20 depending on kinetic energy
• alpha particles hvae a Wt=20

Question 31

what does the radiolysis of water produce ?

Answer 31

produces hydroxyl radicals- small lipid solule highly diffusable
- they are very powerful oxidising agents
can produce hydrogen peroxide, superoxide anions and electrons are released

Question 32

how are reactive oxygen species detoxified ?

Answer 32

• SUPEROXIDE DISMUTASE= copper-zincSOD and manganeseSOD present in mitochondria - this produces hydrogen peroxide from 2 oxygen molecules and 2 hydrogen molecules
• CATALASE= present in peroxisomes converts hydrogen perioxide into water and oxygen
• GLUTATHIONE peroxidases- present in most compartments of the cell - firstly reacts hydrogen peroxide with antioxidant GSH to produce water and GSSG- then GSSG reacts with NADPH and hydrogen ion to re-produced GSH

Question 33

What do anti-oxidant scavengers do ?

Answer 33

present in the aqueous phase of the cell - GSH and ascorbic acid
- these react with free radicals to minimise free radical damage
in the lipid phase- vit E and carotenoids- present in cell membranes

Question 34

what is the oxygen paradox ?

Answer 34

we need oxygen for life
oxygen is toxic to cells because mitochondria are a source of ROS
- the electron transport chain is not 100% efficient electrons leak producng superoxide anions which can then produce hydrogen peroxide in cells

Question 35

what damage can free radical ROS do to DNA ?

Answer 35

it can cause single or double strand breaks- these are difficult to repair without altering fidelity of DNA

• this can lead to mutations that can lead to teratogenesis or cancer
• this can lead to cell death and then radiation syndrome

Question 36

what are the 2 components of the effects of ionising radiation ?

Answer 36

DETERMINISTIC- threshold dose and severity increases with exposure
-severity and frequency increases with exposure up to a max effect
STOCHASTIC- have no threshold, probability of effect increases with dose but not with severity-effects increase in a linear manner with exposure, this implies no safe limit

Question 37

what are the examples of deterministic and stochastic effects of ionising radiation ?

Answer 37

deterministic - radiation sickness, damage to skin and cataracts

stochastic- genetic damage and cancer and teratogenesis