Chapter 5 - Effects of Long Term Exposure to Radiation Flashcards
Epidemiology
The science that examines the incidence, distribution, and control of disease in a population
Relative Risk
a ratio of cancer incidence in an exposed population to that of an unexposed population:
observed cases / expected cases
What is the leading cause of radiation to Americans?
Radon
What percent of radiation to Americans comes from x-rays? From radon?
x-rays: 11%
radon: 54%
Absolute Risk
risk in terms of:
number of cases / 106 persons / rad / year
Excess Risk
the number of excess of unexpected cases:
observed cases - expected cases = excess risk
What does BEIR stand for and what risk model do they use?
Committee on the Biological Effects of Ionizing Radiation. They’re associated with the National Academy of Sciences. BEIR use the Relative Risk Model.
What are the 6 common malignancies stemming from radiation exposure?
- leukemia
- Skin carcinoma
- thyroid cancer
- breast cancer
- osteosarcoma
- lung cancer
What dose-response relationship does Leukemia have? What are the latent period and at-risk period?
- linear, nonthreshold
2. latent period is 4-7 years, at-risk is 15-20
What dose-response relationship does (radiation-induced) Skin Carcinoma have? What is the latent period?
- linear (?), threshold
2. 5-10 years
What dose-response relationship does Thyroid Cancer have? What is the latent period?
- linear, nonthreshold
2. 10-35 years
Thyroid Cancer accounts for ___% of the deaths attributed to radiation-induced malignancies.
12%
What dose-response relationship does Breast Cancer have? What is the latent period?
- linear, threshold (?)
2. 10-40 years
What is the absolute risk for Breast Cancer?
6 cases / 106 person / rad / year
What are the relative risk and absolute risk for Osteosarcoma?
relative risk: 122:1
absolute risk: 0.11 cases / 106 persons / rad / year
What experimental group was studied to gain data on radiation-induced Osteosarcoma? Why?
- watch-dial painters
- radium was incidentally ingested from the tips of paint brushes as the painters straightened the brushes with their mouths
What is the dose-response relationship for Osteosarcoma?
linear, quadratic
What experimental group was studied to gain data on radiation-induced Lung Cancer? What was the cause?
miners of uranium and pitchblende. 50% of those workers eventually died of lung cancer. Radon was the primary cause of exposure
What is the dose-response relationship for Lung Cancer? What is the absolute risk?
- linear, nonthreshold
2. 1.3 cases / 106 persons / rad / year
In animals, life-span shortening from radiation causes a reduction in parenchymal cells and blood vessels, and more connective tissue in organs. This is also called ________-_______ _____.
radiation-induced aging; these are normal aging processes sped up by exposure to radiation
Who did a radiation study on fruit flies? What year did this study happen?
Herman Muller, 1927
Doubling Dose definition and amount
- ) the dose of radiation required per generation to double the spontaneous mutation rate. (current rate is 6%)
- ) 0.5 - 2.5 Gy (lower is required for acute dose and higher is required for chronic dose)
What four factors affect an embryo’s response to radiation?
- total dose
- rate of dose
- quality of radiation
- stage of development
What are the six principle effects of irradiation to the fetus?
- prenatal or neonatal death
- congenital abnormalities
- growth impairment
- reduced intelligence
- genetic abnormalities
- cancer induction
What is the time frame for the Pre-Implantation stage? Radiation damage at this stage can cause what?
- from the joining of the sperm and egg to day 9
2. prenatal death
What is the most critical times of exposure in the Pre-Implantation stage? If there is a loss of a sex chromosome in a female, what is the disease called?
- 12 hours post conception and at 30-60 hours
2. Turner’s Syndrome
What is the time frame for the Major Ogranogenesis stage? At what point are the organs most vulnerable?
- between the 2nd wek and the 8th week
2. differs by organ system; most vulnerable when the system is at the peak differentiation
What is the time frame for the Fetal Growth Stage? Radiation damage at this stage can cause what?
- from day 45 to the end of term
2. these happen later in life but are caused by radiation: behavioral changes, reduced IQ, or cancer
Neoplasms are __ times more frequent in the 1st trimester when compared to the other two.
3x
What organ system is more susceptible to irradiation damage in humans? Why?
- Central Nervous System
2. the CNS takes longer to develop in humans meaning there is more opportunity for radiation damage
Stochastic Effects
- also called “statistical response”
- occur randomly in nature
- radiation increases probability of occurrence, but NOT the severity
- linear or linear quadratic nonthreshold
Nonstochastic Effects
- also called “deterministic effects”
- severity increases with increased dose
- not seen in diagnostic radiology, usually only observed in radiation accidents
- linear (?) threshold
- examples: cataracts, fibrosis, hematopoietic damage, and erythema
Radiation Hormesis
theory that ionizing radiation is benign at low levels of exposure and that doses of natural background radiation is beneficial.
**this theory has been rejected by U.S. National Research Council and the NCRP
