1. RAD 315 RADIOBIOLOGY AND RADIATION PROTECTION
WHOLE BODY RADIATION

2. Syndrome Signs and symptoms experienced by irradiated mammal
Total body syndrome
Radiation syndrome

3. Acute exposure Given in minutes Total body or almost total body
External radiation – penetrating
Doses quoted in cGy for x or gamma radiation
Lower doses would be needed for same effect if high LET radiation is used

4. Survival time Is dependent on dose Expressed as mean survival time
Varies between species
Lethal dose: LD x/z is the dose needed to
kill x% in z number of days
Females are more resistant
Very young and very old are more sensitive

5. LD50/30 for different species
Human – 300 cGy
Monkey
Dog
Rabbit
Rat/mouse
Frog
Goldfish

6. Data Has been established from: Animal experiments
Hiroshima and Nagasaki
Marshall Island fallout
Nuclear accidents
Medical exposure

7. Total body exposure
After total body exposure, the animal exhibits three main stages of response:
Prodromal
Latent
manifest

8. prodromal the early symptoms that occur initially after exposure.
Occurs for minutes to days
Nausea, vomiting, diarrhea
Severe PRS usually means poor survival

9. Latent Occurs for hours to weeks after exposure
No major symptoms (latent)

10. Manifest illness Hours to weeks after exposure
Symptoms reflect the systems of the body that has been damaged

11. Body systems affected There are three body systems affected:
Bone marrow GI
CNS
So there are basically three types of death at three different levels, depending on dose
Each has its own PRS

12. Survival time See graph page 139
Derived from experiments with a variety of species
Is dose dependent between 2 – 10 Gy and after 100 Gy
Not dose dependent between 10 – 100 Gy
There is overlapping of syndromes present after exposure. Table shows PRIMARY cause of death.

13. Los Alamos in 1958 Major accidental exposure to an individual
3900 – 4900 cGY from neutrons and gamma rays
Immediate shock and loss of consciousness
No lymphocytes after 8 hours
Dead in 35 hours.

14. CNS syndrome
Death occurs within hours as a result of neurological and cardiovascular breakdown.
Associated dose: > 5,000 cGy
PRS :
Immediate diarrhea
Fever
Hypertension
Loss of consciousness

15. CNS syndrome Manifest symptoms: Disorientation Loss of coordination
Respiratory distress
Diarrhea
Seizures
coma

16. CNS syndrome Prognosis: two days at most
Person does not live long enough to get GI and bone marrow symptoms

17. GI syndrome Prior to Chernobyl, little was known about GI syndrome
Death occurs in matter of days due to destruction of intestinal mucosa.
Associated dose: 1000 cGy
Threshold dose: 600cGy (LD100 = 600 to 1000 cGy)

18. GI syndrome PRS: N, V, D Manifest Symptoms: Prognosis: about 10 days
Dehydration
Weight loss
exhaustion
Prognosis: about 10 days

19. Bone Marrow Syndrome
Possible death due to damage of blood forming organs (bone marrow)
Associated dose: 250 to 500 cGy
PRS: N, V, fatigue

20. Bone Marrow Syndrome Manifest symptoms (occurs after about 3 weeks):
Chills
Fatigue (RBC)
Infection (WBC)
Hemorrhage (platelets)
Prognosis: possible death in about one month from infection and hemorrhage

21. Bone Marrow Syndrome 100 – 300 cGy : bone marrow may recover
400 – 600cGy: few survivors
1000 cGy : no survivors
LD50 for humans is taken as cGy
Survival can be improved with bone marrow transplants and modern medical care.

22. Radiation effects on the embryo and fetus
Classic effects:
Lethal effects induced by relatively small doses if before or immediately after implantation in the uterine wall
Malformations when irradiated during organ formation
Growth disturbances without malformation at all stages of fetal development

23. Embryo and fetus
Miscellaneous effects on various body structures and functions.
Main factors of importance are dose and stage of development

24. Fetal development Pre – implantation Major organogenesis Fetal stage
Conception to day 10: all cells highly undifferentiated
Major organogenesis
Day 10 to 6 weeks : differentiation begins
Fetal stage
6 weeks to birth

25. Pre - implantation Increased prenatal death
Most sensitive stage to lethal effects
If embryo survives, it grows normally in utero and afterwards.
Few, if any, abnormalities are produced at this stage
In mouse: 5 – 15 cGy can kill fertilized eggs

26. Major organogenesis Increased neonatal death Decreased prenatal death
Principle effect is production of congenital structural abnormalities
In mouse: 200cGyn can result in 100% abnormalities.

27. Major organogenesis
Contrary to what is seen in animals, radiation induced malformations of body structures other than CNS are uncommon in humans
Why is this so?
Animal experiments are controlled and exact, but not with humans
Human organogenesis is 1/15 gestation period. In mice it is 1/3.
CNS org. takes longer time in humans

28. Major organogenesis CNS malformations: Microcephaly Hydrocephaly
Micropthalmia
Mental retardation

29. Fetal stage
A variety of effects have been observed in animals: liver, kidney, bone marrow
After fairly high doses: sterility, cancer
High doses would be needed to kill the fetus at this period
Permanent growth retardation

30. Experience in humans
Medical exposures during the early part of the last century
Survivors in Japan

31. generalizations
Large doses (>250cGy) before 2-3 weeks, are not very likely to produce severe abnormalities but embryo deaths are likely.
4 – 11 weeks: severe abnormalities of many organs
11 – 16 weeks:
Eye, skeletal, genital organ abnormalities

32. generalizations 16 – 20 weeks: some CNS abnormalities
After 30 weeks gross structural abnormalities not likely, but there could be functional abnormalities.
Hiroshima: 30/1600 mental retardations after exposure at 8 – 15 weeks. This is higher than normal.

33. summary
Moderate doses of radiation can cause catastrophic effects on the developing embryo and fetus
Effects depend on stage, dose and doserate
Gestation is divided into:
Preimplantation – 0 to 9 days
Organogenesis – 10 days to 6 weeks
Fetal stage – 6 weeks to term

34. summary Principle effects are: Growth retardation
Embryonic, neonatal or fetal death
Gross congenital malformation

35. summary LD50 is lowest during preimplantation
Peak incidence of malformations occurs when fetus is irradiated during organogenesis
Malformations other than CNS is uncommon in humans
Data from Japan shows that microcephaly can result from air dose of 10 – 19 R

36. summary
From medical x-ray exposure: low doses of in utero exposure can lead to an increase in cancer incidence in the first 10 – 15 years of life by a factor of 1.5 – 2
No comparable increase was seen in Japanese survivors
MPD to fetus is 0.5 rem per gestation period