Rad Bio: Unit 5 Exam

Late Effects

Appear months or years after exposure, principle late effects are malignancy and genetic effects; radiation protection guidelines are based on observed or suspected late effects

What dose response relationship does late effects follow?

Linear non-threshold

What is the tissue response of late effects?

Stochastic

Epidemiologic Studies

Studies of large numbers of people exposed to toxic substances

What are some late effect limitations?

Natural incidences, control group accuracy, statistical significance, isolation of other contributing factors and dosimetry estimates

What is another name for stochastic?

Probabilistic

Relative Risk

Observing large populations for late effects without any precise knowledge of the dose they were exposed to

What is the most used risk estimate model?

Relative risk

What is the dose response relationship of cataracts and skin cancers?

Nonlinear threshold

Relative risk equation

Observed cases (exposed)/expected cases (unexposed)

Excess Risk

The difference between the observed number of cases and the expected number of cases

Excess risk equation

Observed - expected

Absolute Risk

Very specific; must know at least 2 dose levels, X number of cases/ Gy population

What is the first sign on skin cancer caused by radiation?

Radiodermititis

Who was effected by cataracts due to radiation?

Atomic bomb survivors, radiation therapy patients and high energy physicists

Cyclotron

Machine capable of accelerating charged particles to very high energies

What is the acute dose threshold for cataracts?

.5 Gy

What is the chronic dose threshold for cataracts?

5-10 Gy

How do stochastic effects change with increasing dose?

Increase in frequency

What five groups of humans were exposed to high doses of ionzing radiation that demonstrate proof that radiation induces cancer?

• Radium watch painters

• Uranium miners

• Breast cancer patients

• Early medical radiation workers

• Atomic bomb survivors

Early medical workers had higher incidence of what 2 blood disorders?

Aplastic anemia and leukemia

Leukemia

Blood cancer that normally begins in the bone marrow and results in high numbers of abnormal blood cells 

What is the at risk period for leukemia?

20 years

What dose response relationship does thyroid cancer follow?

Linear nonthreshold

Why are the late effects of radiation from Chernobyl a world wide concern?

The wind travelled the radiation to 20 countries

What bones were most frequently affects by ingested radium?

Pelvis, femur and mandible

What radioactive substance contributed the most to Uranium minors development of lung cancer?

Radon

What is the 2nd leading cause of lung cancer?

Radon

What does radon heavily emit?

Alpha particles

What is the Environmental Protection Agency’s action guideline of radon in homes?

4 picocuries per liter

What is the most radiosensitive time of pregnancy?

First trimester

Which teratogenic effect is most probable in the preimplantation stage?

Fetal death

Preimplantation Stage

The first two weeks of pregnancy

Organogenesis Stage

Weeks 2-8 of pregnancy

What can occur in the first 2 weeks of pregnancy if exposed?

Prenatal death

What can occur in weeks 2-8 of pregnancy if exposed?

Skeletal, organ or CNS neurological abnormalities

Microcephaly

Head circumference 2x smaller; atomic bomb survivors and Marshall islanders

What can occur in weeks 8-15 in pregnancy if exposed?

Developmental delays

What can occur after 3 months of pregnancy if exposed?

Cancers

What are two principle late effects of radiation?

Malignancy and genetic effects

A relative risk of 1 means:

No effect

A relative risk of .5 means:

Radiation hormesis

A relative risk of 1.3 means:

Frequency 50% higher in irradiated populations

Skin cancer populations studied

• Early radiologists and technologist

• Radiation therapy patients

Leukemia populations studied

• Early radiologists

• Atomic bomb survivors

• Lab animals

• Ankylosing spondylithis patients

Thyroid cancer populations studied

• Chernobyl

• Ann Arbor and Rochestor series

• Rongelap Atoll

What is the at-risk period for most radiation induced cancers?

Lifetime

Bone cancer populations studied

• Radium watch dial painters

• Radium salt patients

Breast cancer populations studied

• Atomic bomb survivors

• Postpartum mastitis

• TB treatment

Lung cancer populations studied

• Uranium miners

• Bohemian miners

• Radon in homes

Liver cancer populations studied

• Thorotrast patients

BEIR

Biological Effects on Ionizing Radiation

What population was studied the most for microcephaly?

Atomic bomb survivors and Marshall Islanders

What population was studied the most for developmental delays?

Atomic bomb survivors

Genetic Effects

Radiation exposure to the germ cells that can be passed on to offspring