Radiation and Human Health

Question 1

What are calculations of risk posed by irradiation based on?

Answer 1

Type of radiation
Energy the radiation leaves the body
Where in the body it remains

Question 2

What is absorbed dose a measure of?

How do alpha, beta and gamma energies relate?

Answer 2

Measure of the energy deposited by the radiation in the material that absorbs it.
in Joules/kg

Beta and gamma - Damage to biological tissue is generally proportional to the energy deposited.

Alpha - ionising energy decreases with distance from source.

Question 3

What does effective dose measure?

Answer 3

Effective dose takes into account that exposure can vary between different tissue types.

Question 4

Explain Deterministic effects

Answer 4

Radiation has a threshold dose.

Above this, frequency and severity increase with increasing dose.

Question 5

Explain Stochastic effects

Answer 5

Proportional relationship between radiation does and probability of occurrence.

Question 6

What is the statistical individual risk of fatal cancer?

Answer 6

5 x 10^-2 Sv-1

e.g., 1 million receive dose of 1Sv. 50,000 will get cancer.

Question 7

What doses will cause;

• Death within 2 days
• 50% chance of death
• Radiation sickness

Answer 7

• 40Gy
• 4Gy
• 1Gy

Question 8

What are the three suggested effects of low dose radiation exposure?

Answer 8

1. Radiation hormesis - beneficial effects at low dose.
2. Linear, no threshold (LNT) - current accepted hypothesis.
3. Enhanced risk - low level exposure enhances risk

Question 9

What is genomic instability?

Answer 9

Colonies of stem cells grown from irradiated parents, expressed generations later.

Question 10

What is the by-stander effect?

Answer 10

Cells near to irradiated cells exhibit chromosome damage.

Question 11

What does ionising radiation cause?

Answer 11

Causes non-specific disorganisation or injury of cells and tissues.

Question 12

What are the two types of radiation damage to chromosomes?

Answer 12

1. Indirect damage
   - Water molecules ionised (Radiolysis of water)
   - Break apart and from OH- radicals
   - OH- radical contains unpaired e- which reacts with DNA
2. Direct damage
   - DNA molecule struck by radiation, becomes ionised
   - Damaged

Question 13

What can happened once chromosomes are damaged by radiation?

Answer 13

• Cells can repair themselves if mild damage
• Damage sits inactive until other agents interact with cell
• Damage becomes cancer
• Cells stop functioning and die

Question 14

What are the most vulnerable cells?

Answer 14

Embryos, lymphatic system, bone marrow

Question 15

What are the characteristic of Radon? and health effects associated?

Answer 15

Rn-222

• Noble gas, chemically unreactive
• T1/2 = 4 days
• Decay product of U-238
• Alpha and gamma radiation
• Daughters: Pb-210 Po-210

Dangerous levels associated in igneous rocks containing uranium.
Escapes through concentrated void spaces and radon is denser than gas.
Can cause lung caner.

Question 16

How does Earths magnetosphere protect it?

Answer 16

Prevents charged particles (photons) from reaching the earth.
Acts as a protective barrier, attenuating radiation.

Question 17

What do air/clouds protect the earth from?

Answer 17

Shield us from neutrons, x-rays and gamma radiation from space.

Question 18

What are the Van-Allen Belts?

Answer 18

Two regions of intense radiation partially surrounding the earth.
Radiation form magnetically trapped particles.

Question 19

What are solar flares in space?

Answer 19

High radiation intensity events, difficult to avoid.

Would require additional protection.