Lecture 8

Question 1

Radiation life-shortening?

Answer 1

1-5% reduction in remaining life expectancy per Sv for acute exposure

Question 2

Life shortening has been observed in

Answer 2

US radiologists * and the A-bomb survivors

Question 3

life shortening also attributed to?

Answer 3

cancer and cancer with age specific diseases.

Question 4

Life shortening for Mouse study displays?

Answer 4

increased relative risk with increased radiation dose.

Question 5

Effects of IR on embryo?

Answer 5

pre- and neo-natal death *growth retardation *abnormalities *post-natal induction of cancer

Question 6

In utero effects

Answer 6

• cells are more sensitive to IR than adults

- Larger life expectancy through adverse effects

Question 7

The three stages of embryonic development?

Answer 7

The preimplantation
Organogenesis
fetal

Question 8

Preimplantation stage

Answer 8

-Stage of conception until fetilised egg attaches to uterus wall 0-9 days
Pre-natal death is most common in this stage
-0.05Gy can kill
LD 50/30=1

Question 9

The peak incidence of abnormalities is during what stage?

Answer 9

Organogenesis (10 days to 6 weeks)
CNS very sensitive
0.2Gy can increase some abnormalities
LD 50/30=1.5

Question 10

Possible effects of organogenesis?

Answer 10

Malformation of organs

Small head size

Intrauterine growth retardation

Question 11

Fetal stage?

Answer 11

LD 50/30 is 2-3Gy
(growth stage)
8-16 weeks
Nervous system may be affected and carcinogenesis

Question 12

Threshold for mental retardation?

Answer 12

0.2 Fy

Question 13

Observed shift in IQ is?

Answer 13

30 points per Gy during sensitive period

Question 14

Natural incidence of fatal childhood cancer is?

Answer 14

1 in 2000 people
200-250 deaths for under 10 yrs/10mSv
1-2 Leukaemia

Question 15

Total cancer induction period is?

Answer 15

20 yrs but leukaemia risk is doubled during in utero stage

Question 16

A absorbed dose of 0.1 Gy to an embryo (organogenesis) can result in?

Answer 16

pre natal death or IQ loss

Question 17

Risks of in-utero irradiation

Answer 17

0-2 wks Spontaneous abortion
2-10wks-Abnormality
2-15wks-Mental retardation
0-9mon-Cancer, growth retardation, genetic

Question 18

Are there any genetic effects?

Answer 18

In humans no data

Question 19

No human data because of?

Answer 19

• long life cycle (we live too long)
• studies require large populations > 1 million
• too few offspring
• large incidence of naturally occurring genetic damage

Question 20

Is there evidence of heritable mutations in humans

Answer 20

Yes

Question 21

Summary of Megamouse experiment?

Answer 21

Different gene loci have different rates of induction of mutation

2. Mutation frequency is dose-rate dependent and sex dependent
3. The time between irradiation and conception is important
4. Magnitude of the effect depends upon the stage of sex cell irradiated

Question 22

Are males or females more sensitive on average?

Answer 22

Male
At high dose rates 1Gy/min same
as it decreases males more sensitive

Question 23

A delay in conception following irradiation means what?

Answer 23

reduces the effect of irradiation, due to repair (6 months)

Question 24

Are later stages of male and female sex cells more sensitive?

Answer 24

Mature sex cells by a factor of 5

Question 25

Doubling dose?

Answer 25

Doubles spontaneous rate
mutations per million 10mSv
(relative risk 1Gy)
(absolute risks 100 mutations/ 10mSv for future generations and 60 per million per 10mSv) mutations for working age population)

Question 26

Sundry effects of IR?

Answer 26

Sterility
cataract formation
skin damage
epilation