Ionising radiation 2

Question 1

what is the LNT model ?

Answer 1

linear no threshold model

• this refers to stochastic effects of ionising radiation
• there is no safe limit of exposure
• however this has been questioned due to the effects at chernobyl

Question 2

what are the prodromal effects caused by exposure to ionising radiation ?

Answer 2

anorexia, nausea, vomitting and diarrhoea
these can last hours
these effects occur due to acute cell death

Question 3

what occurs after the prodromal phase ?

Answer 3

latent phase- this lasts several days

- it depends on dose of radiation

Question 4

after the latent phase, overt illness occurs. what happens?

Answer 4

stop producing red blood cells so there is not enough circulating oxygen,
- start to haemorrhage due to platelets not being produced, vunerbale to infections due to WBCs
after this it is either recovery or death

Question 5

what level of exposure to ionising radiation has no one ever survived from even with treatment ?

Answer 5

greater than or equal to 100 Gys

Question 6

what biological effects occur between 1-10 Gy dose of radiation ?

Answer 6

haematological death - cells in bone marrow are most sensitive to ionising radiation

Question 7

what biological effects occur between 10-60 Gy dose of radiation ?

Answer 7

intestinal death

- epithelial cells are also sensitive - they have a high turnover rate in GIT

Question 8

what biological effects occur at 100Gy dose of radiation ?

Answer 8

CNS death

Question 9

what does LD50/30= 2.5-4.5Gy mean ?

Answer 9

without medical care doses of 2.5 to 4.5 Gy would be lethal after 30 days in 50% of patients

Question 10

what are the acute effects of radiation exposure on the skin ?

Answer 10

low level= erythema, temporary hair loss

high level= inflammation, desquamation (loss of skin), ulceration, permanent hair loss, cancer

Question 11

what are the acute effects of radiation exposure to the eyes ?

Answer 11

cell death in the lens leads to radiation-induced cataracts

Question 12

what are the acute effects of radiation exposure to the gonads ?

Answer 12

low level= temporary sterility in males and females

high level= permanent sterility in males and females

Question 13

what does cytogenetic effects mean ?

Answer 13

exposure to radiation can cause chromosomal damage

Question 14

to treat cancer, 20-80Gy is used which is significant greater than the LD50/30 but why does this not cause death ?

Answer 14

because doses are given separately to allow the body to recover and they are only given to a specific area of the body

Question 15

what are the long term effects of exposure to ionising radiation ?

Answer 15

cancers- most frequent are breast, thyroid( particularly for radon because it is readily taken up by the thyroid), lung, leukemias and alimentary tract

Question 16

what are the long term effects of ionising radiation on the foetus ?

Answer 16

growth impairment
reduced intelligence
congenital abnormalities 
prenatal or neonatal deaths 
cancer-leukemias

Question 17

what do the effects of ionising radiation on the foetus depend on ?

Answer 17

dependent upon time of exposure
- 3-8 weeks cataracts
- whole gestation for childhood leukemias
- 4-19 weeks for mental retardation
- 4-18 weeks- microencephaly 
-4-8 weeks- microphthalmia 
- 4-19 weeks growth retardation 
4-8 weeks skeletal defects

Question 18

where is the highest risk of exposure to radon gas ?

Answer 18

in areas with lots of granite rock

- contributes to about 50% of normal radiation we are exposed to

Question 19

how does radon gas cause damage ?

Answer 19

it can enter and accumulate in buildings and sources including soil, rock and building materials and water supplies
- it can be readily inhaled and it contains alpha particles so it is not dangerous to us externally but once its inhaled it is very dangerous

Question 20

what does it mean by ionising radiation might have hormetic effects ?

Answer 20

that at low levels it may have a protective effect against cancer