Late Deterministic and Stochastic Radiation Effects on Organ Systems

Question 1

Late Effects

Radiation-induced damage at the ___ level may lead to measurable ___ and ___ damage in the living organism as a whole later in life. These outcomes are called ___ effects and are the ___-term results of ___ exposure.

Examples of measurable late biologic damage
• ___
• ___
• ___ mutations

Answer 1

Late Effects

Radiation-induced damage at the cellular level may lead to measurable somatic and genetic damage in the living organism as a whole later in life. These outcomes are called late effects and are the long-term results of radiation exposure.

Examples of measurable late biologic damage
• Cataracts
• Leukemia
• Geneticmutations

Question 2

Epidemiology

A “science that deals with the ___, ___, and ___ of ___ in a population.” (Travis, 1989)
Studies consist of ___ and ___ analysis of data, such as the incidence of ___ within groups of people.

Studies include the risk of ___-induced cancer.

The incident rates at which these ___-related ___ occur are determined by comparing the ___ incidence of ___ occurring in a human population with the incidence of ___ occurring in an ___ population.

___ factors are then determined for the general human population.

Answer 2

Epidemiology

A “science that deals with the incidence, distribution, and control of disease in a population.” (Travis, 1989)
Studies consist of observations and statistical analysis of data, such as the incidence of disease within groups of people.

Studies include the risk of radiation-induced cancer.

The incident rates at which these irradiation-related malignancies occur are determined by comparing the natural incidence of cancer occurring in a human population with the incidence of cancer occurring in an irradiated population.

Risk factors are then determined for the general human population.

Question 3

Radiation Dose-Response Relationship

Radiobiologists engaged in research have a common goal to establish relationships between ___ and ___-response to predict the ___ of occurrence of ___ in human populations that have been exposed to ___ levels of ___ radiation.

Radiation dose-response relationship is demonstrated ___ through a ___ that maps the observed effects of radiation ___ in relation to the dose of radiation ___.
As radiation dose escalates, so do most ___.

Variables, or numbers, in a dose-response curve are plotted along the axes of the graph to demonstrate the relationship between the dose ___ (___ axis) and the biologic ___ observed (___ axis). The curve is either ___ or ___ and depicts either a ___ dose or a ___ dose.

Answer 3

Radiation Dose-Response Relationship

Radiobiologists engaged in research have a common goal to establish relationships between radiation and dose-response to predict the risk of occurrence of malignancies in human populations that have been exposed to low levels of ionizing radiation.

Radiation dose-response relationship is demonstrated graphically through a curve that maps the observed effects of radiation exposure in relation to the dose of radiation received.
As radiation dose escalates, so do most effects.

Variables, or numbers, in a dose-response curve are plotted along the axes of the graph to demonstrate the relationship between the dose received (horizontal axis) and the biologic effects observed (vertical axis). The curve is either linear or nonlinear and depicts either a threshold dose or a nonthreshold dose.

Question 4

Radiation Dose-Response Curves

Answer 4

Radiation Dose-Response Curves

Question 5

Threshold and Nonthreshold Relationships

Threshold: a point at which a ___ or ___ to an ___ stimulation first occurs

With reference to ionizing radiation, threshold means that ___ a certain radiation level or dose, ___ biologic effects are observed.

Biologic effects begin to occur only when the ___ level or dose is ___.

Nonthreshold indicates that ___ radiation dose has the capability of producing a ___ effect.

If ionizing radiation functions as the ___, and the biologic effect it produces is the ___, and if a ___ relationship exists between radiation dose and a biologic response, ___ biologic effects will be caused in living organisms by even the ___ dose of ionizing radiation.

No radiation dose can be considered absolutely ___.

Answer 5

Threshold and Nonthreshold Relationships

Threshold: a point at which a response or reaction to an increasing stimulation first occurs

With reference to ionizing radiation, threshold means that below a certain radiation level or dose, no biologic effects are observed.

Biologic effects begin to occur only when the threshold level or dose is reached.

Nonthreshold indicates that any radiation dose has the capability of producing a biologic effect.

If ionizing radiation functions as the stimulus, and the biologic effect it produces is the response, and if a nonthreshold relationship exists between radiation dose and a biologic response, some biologic effects will be caused in living organisms by even the smallest dose of ionizing radiation.

No radiation dose can be considered absolutely safe.

Question 6

Linear Nonthreshold Curve

Answer 6

Linear Nonthreshold Curve

Question 7

Risk Model Used to Predict Cancer Risk and Genetic Damage in Human Populations

Committee on the Biological Effects of Ionizing Radiation (BEIR) 1980
Most ___ effects (e.g., ___) and ___ (hereditary) effects at ___ dose levels from low-___ radiation, such as the type of energy used in ___ radiology, appear to follow a ___-___ ___ curve.

BEIR (1990) Revised risk estimates indicated that the risk of radiation exposure was about ___ to ___ times ___ that previously projected. Currently the committee recommends the use of the ___ ___ curve of radiation dose-response for most types of ___ . ____-___ ___ curve implies that the biologic response to ionizing radiation is ___ proportional to the dose received.

BEIR Committee believes the ___-___ ___ curve is a more accurate reflection of ___ ___ and ___ effects at ___- dose levels from low-___ radiation.
___, ___ cancer, and ___ damage are presumed to follow the LQNT curve.

Answer 7

Risk Model Used to Predict Cancer Risk and Genetic Damage in Human Populations

Committee on the Biological Effects of Ionizing Radiation (BEIR) 1980
Most stochastic effects (e.g., cancer) and genetic (hereditary) effects at low dose levels from low-LET radiation, such as the type of energy used in diagnostic radiology, appear to follow a linear-quadratic nonthreshold curve.

BEIR (1990) Revised risk estimates indicated that the risk of radiation exposure was about three to four times greater that previously projected. Currently the committee recommends the use of the linear nonthreshold curve of radiation dose-response for most types of cancer. Linear nonthreshold curve implies that the biologic response to ionizing radiation is directly proportional to the dose received.

BEIR Committee believes the linear-quadratic nonthreshold curve (LQNT) is a more accurate reflection of stochastic somatic and genetic effects at low- dose levels from low-LET radiation.
Leukemia, breast cancer, and heritable damage are presumed to follow the LQNT curve.

Question 8

Risk Model Used to Predict High-Dose Cellular Response

Deterministic effects of significant radiation exposure such as skin ___ and ___ depression may be demonstrated graphically through the use of a ___ ___ dose-response curve.

Biologic response does not occur ___ a specific dose level.

Laboratory experiments on animals and data from human populations observed after ___ ___ doses of radiation provided the foundation for this curve.

Answer 8

Risk Model Used to Predict High-Dose Cellular Response

Deterministic effects of significant radiation exposure such as skin erythema and hematologic depression may be demonstrated graphically through the use of a linear threshold dose-response curve.

Biologic response does not occur below a specific dose level.

Laboratory experiments on animals and data from human populations observed after acute high doses of radiation provided the foundation for this curve.

Question 9

Risk Model Used to Predict High-Dose Cellular Response

___ or ___-shaped (nonlinear)

___ curve of radiation

Dose-response relationship generally employed in radiation therapy to demonstrate ___-dose ___ response to the radiation within ___ locations, such as ___, lens of the ___, and various types of ___ cells.

Different effects require different ___ doses.

Tail of the curve indicates that limited recovery occurs at ___ radiation doses.

At the highest radiation doses, the curve gradually ___ off and then veers ___, because the affected living specimen or tissue ___ before the observable effect ___.

Answer 9

Risk Model Used to Predict High-Dose Cellular Response

Sigmoid or S-shaped (nonlinear)

Threshold curve of radiation

Dose-response relationship generally employed in radiation therapy to demonstrate high-dose cellular response to the radiation within specific locations, such as skin, lens of the eye, and various types of blood cells.

Different effects require different minimal doses.

Tail of the curve indicates that limited recovery occurs at lower radiation doses.

At the highest radiation doses, the curve gradually levels off and then veers downward, because the affected living specimen or tissue dies before the observable effect appears.

Question 10

Somatic Effects

When living organisms that have been exposed to radiation sustain biologic damage, the effects of this exposure are classified as ___ (i.e., ___) effects.

The classification of ___ effects may be subdivided into:
• ___ effects: The probability that the effect happens depends upon the ___ dose, but the ___ of the effect does not.
• Example: Occurrence of ___

• ___ effects: Both the ___ and the ___ of the effect depend upon the dose.
• Example: A ___

Answer 10

Somatic Effects

When living organisms that have been exposed to radiation sustain biologic damage, the effects of this exposure are classified as somatic (i.e., body) effects.

The classification of somatic effects may be subdivided into:
• Stochastic effects: The probability that the effect happens depends upon the received dose, but the severity of the effect does not.
• Example: Occurrence of cancer

• Deterministic effects: Both the probability and the severity of the effect depend upon the dose.
• Example: A cataract

Question 11

Somatic Effects

Answer 11

Somatic Effects

Question 12

Late Somatic Effects

Are consequences of radiation exposure that appear ___ or ___ after such exposure.

Effects may result from:
• Previous ___- or ___-body acute exposure
• Previous ___ radiation doses
• ___-term ___-level doses sustained over ___ years

These late effects can be directly related to the ___ received. Such ___ developing changes to the body from radiation exposure are therefore classified as ___ ___ ___ effects.

Late responses in the body to radiation exposure that do not have a ___ occur in an arbitrary or probabilistic manner and have a severity that does not depend on dose and are classified as ___ ___ effects.

Answer 12

Late Somatic Effects

Are consequences of radiation exposure that appear months or years after such exposure.

Effects may result from:
• Previous whole- or partial-body acute exposure
• Previous high radiation doses
• Long-term low-level doses sustained over several years

These late effects can be directly related to the dose received. Such slow developing changes to the body from radiation exposure are therefore classified as late deterministic somatic effects.

Late responses in the body to radiation exposure that do not have a threshold occur in an arbitrary or probabilistic manner and have a severity that does not depend on dose and are classified as late stochastic effects.

Question 13

Risk Estimate for Contracting Cancer from Low-Level Radiation Exposure

___-level doses are a consideration for patients and personnel exposed to ionizing radiation as a result of ___ imaging procedures.

No conclusive proof exists that ___-level ionizing radiation exposure below ___ Sievert (Sv) causes a significant increase in the risk of ___.

Risk may be negligible or even ___

Answer 13

Risk Estimate for Contracting Cancer from Low-Level Radiation Exposure

Low-level doses are a consideration for patients and personnel exposed to ionizing radiation as a result of diagnostic imaging procedures.

No conclusive proof exists that low-level ionizing radiation exposure below 0.1 Sievert (Sv) causes a significant increase in the risk of malignancy.

Risk may be negligible or even nonexistent

Question 14

Categories of Adverse Health Consequences Requiring Study at Low-Levels of Exposure

Using all data available on ___ radiation exposure, members of the scientific and medical communities determined that three categories of adverse health consequences require study at ___-levels of exposure.

• ___ induction
• Damage to the ___ from irradiation in ___
• ___ (hereditary) effects

Answer 14

Categories of Adverse Health Consequences Requiring Study at Low-Levels of Exposure

Using all data available on high radiation exposure, members of the scientific and medical communities determined that three categories of adverse health consequences require study at low-levels of exposure.

• Cancer induction
• Damage to the unborn from irradiation in utero
• Genetic (hereditary) effects

Question 15

Summary of Major Types of Late Effects

• ___ (stochastic event)
• ___ (deterministic event)
• ___ effects (birth defects) (stochastic events)

Answer 15

Summary of Major Types of Late Effects

• Carcinogenesis (stochastic event)
• Cataractogenesis (deterministic event)
• Embryologic effects (birth defects) (stochastic events)

Question 16

Risk Estimates for Cancer

Exposure to ionizing radiation may cause ___ as a ___ ___ effect.

At ___ doses, the risk is measurable in exposed human populations.

At low doses, below ___ Sv, which includes groups such as ___ exposed individuals and virtually all ___ in diagnostic radiology, this risk is ___ directly measurable in population studies.
Reasons:

• The risk is overshadowed by other causes of ___ in humans
• The risk is ___

Answer 16

Risk Estimates for Cancer

Exposure to ionizing radiation may cause cancer as a late stochastic effect.

At high doses, the risk is measurable in exposed human populations.

At low doses, below 0.1 Sv, which includes groups such as occupationally exposed individuals and virtually all patients in diagnostic radiology, this risk is not directly measurable in population studies.
Reasons:

• The risk is overshadowed by other causes of cancer in humans
• The risk is zero

Question 17

Risk Estimates to Predict Cancer Incidence

May be given in terms of ___ risk or ___ risk caused by a ___ exposure to ionizing radiation (over and above background exposure).

Both models predict the number of ___ cancers, or cancers that would ___ have occurred in the population in question without the exposure to ionizing radiation.

Answer 17

Risk Estimates to Predict Cancer Incidence

May be given in terms of absolute risk or relative risk caused by a specific exposure to ionizing radiation (over and above background exposure).

Both models predict the number of excess cancers, or cancers that would not have occurred in the population in question without the exposure to ionizing radiation.

Question 18

Absolute Risk and Relative Risk Models

Answer 18

Absolute Risk and Relative Risk Models

Question 19

Epidemiologic Studies for Determining the Risk of Cancer

They suggest that although the radiation doses encountered in diagnostic radiology should be considered, the ___ to the patient of the information gained from an imaging procedure greatly ___ the minimal theoretical risk to the patient for developing ___ as a ___ late response to radiation exposure.

Answer 19

Epidemiologic Studies for Determining the Risk of Cancer

They suggest that although the radiation doses encountered in diagnostic radiology should be considered, the benefit to the patient of the information gained from an imaging procedure greatly exceeds the minimal theoretical risk to the patient for developing cancer as a stochastic late response to radiation exposure.

Question 20

Extrapolation of Cancer Risk from High-Dose to Low-Dose Data

Models used by researchers for extrapolation of risk from ___-dose to ___-dose data
• ___
• ___-___

1989 BEIR V report supported the ___-___ model for ___ only

For all other cancers the BEIR V Committee recommended adoption of the ___ model to fit the available data.

Answer 20

Extrapolation of Cancer Risk from High-Dose to Low-Dose Data

Models used by researchers for extrapolation of risk from high-dose to low-dose data
• Linear
• Linear-quadratic

1989 BEIR V report supported the linear-quadratic model for leukemia only

For all other cancers the BEIR V Committee recommended adoption of the linear model to fit the available data.

Question 21

Carcinogenesis

Cancer is the most important ___ ___ effect caused by exposure to ionizing radiation.

This effect is a ___ occurrence that does not seem to have a ___ and for which the severity of the disease is not ___- related.

Answer 21

Carcinogenesis

Cancer is the most important late stochastic effect caused by exposure to ionizing radiation.

This effect is a random occurrence that does not seem to have a threshold and for which the severity of the disease is not dose- related.

Question 22

Radiation-Induced Cancer

Laboratory experiments with animals and statistical studies of human populations exposed to ionizing radiation prove that radiation induces ___.

May take ___ or more ___ to develop in humans.

The ___ appearance of cancer induced by ionizing radiation does not appear ___ than a cancer caused by other agents.

Cancer caused by ___-level radiation is ___ to identify.

Human evidence of radiation carcinogenesis comes from epidemiologic studies conducted many years after subjects were exposed to ___ doses of ionizing radiation.

Answer 22

Radiation-Induced Cancer

Laboratory experiments with animals and statistical studies of human populations exposed to ionizing radiation prove that radiation induces cancer.

May take 5 or more years to develop in humans.

The physical appearance of cancer induced by ionizing radiation does not appear different than a cancer caused by other agents.

Cancer caused by low-level radiation is difficult to identify.

Human evidence of radiation carcinogenesis comes from epidemiologic studies conducted many years after subjects were exposed to high doses of ionizing radiation.

Question 23

Radiation-Induced Cancer

Answer 23

Radiation-Induced Cancer

Question 24

Radiation-Induced Cancer

Answer 24

Question 25

Radiation-Induced Malignancies Occurence Rate in Survivors of Hiroshima and Nagasaki

Incidence of ___ has slowly ___ since the late 1940s and early 1950s.

Occurrence rates of other radiation-induced malignancies have continued to ___ since the late 1950s and early 1960s.

• Includes a variety of solid tumors such as ___, ___, ___, and ___ cancers

Answer 25

Radiation-Induced Malignancies Occurence Rate in Survivors of Hiroshima and Nagasaki

Incidence of leukemia has slowly declined since the late 1940s and early 1950s.

Occurrence rates of other radiation-induced malignancies have continued to escalate since the late 1950s and early 1960s.

• Includes a variety of solid tumors such as thyroid, breast, lung, and bone cancers

Question 26

Incidence of Breast Cancer in Japanese Women

Natural incidence of breast cancer
• In general, Japanese women have a ___ incidence of breast cancer than U.S. and Canadian women.

Radiation-induced breast cancer
• Studies of the female Japanese atomic bomb survivors provide strong evidence that ionizing radiation can ___ breast cancer.

• Incidence of breast cancer in these women ___ with radiation dose.
• Numerous studies of female survivors indicate a relative risk for breast cancer ranging from _:_ to as high as _:_.

Answer 26

Incidence of Breast Cancer in Japanese Women

Natural incidence of breast cancer
• In general, Japanese women have a lower incidence of breast cancer than U.S. and Canadian women.

Radiation-induced breast cancer
• Studies of the female Japanese atomic bomb survivors provide strong evidence that ionizing radiation can induce breast cancer.

• Incidence of breast cancer in these women rises with radiation dose.
• Numerous studies of female survivors indicate a relative risk for breast cancer ranging from 4:1 to as high as 10:1.

Question 27

Effectiveness of Ionizing Radiation as a Cancer-Causing Agent

Although studies from Hiroshima and Nagasaki confirm that high doses of ionizing radiation cause cancer, radiation is not a highly effective cancer- ___ agent.

Follow-up studies of approximately 82,000 atomic bomb survivors from 1950 to 1987
• Reveal an excess of only 250 cancer deaths attributed to radiation exposure; instead of the expected 4500 cancer deaths, 4750 actually occurred
• Means that of about every 300 atomic bomb survivors, __ died of a malignancy attributed to an average ___-body radiation dose of approximately ___ Sv

Answer 27

Effectiveness of Ionizing Radiation as a Cancer-Causing Agent

Although studies from Hiroshima and Nagasaki confirm that high doses of ionizing radiation cause cancer, radiation is not a highly effective cancer- causing agent.

Follow-up studies of approximately 82,000 atomic bomb survivors from 1950 to 1987
• Reveal an excess of only 250 cancer deaths attributed to radiation exposure; instead of the expected 4500 cancer deaths, 4750 actually occurred
• Means that of about every 300 atomic bomb survivors, 1 died of a malignancy attributed to an average whole-body radiation dose of approximately 0.14 Sv

Question 28

Radiation Dose and Radiation-Induced Leukemia

Epidemiologic data about the Hiroshima atomic bomb survivors

• Indicate the chance of contracting ___ as a result of exposure to radiation is directly ___ to the ___ of the radiation exposure
• Radiation-induced leukemia is assumed to follow a ___ ___ dose-response relationship compared with leukemia in a population that has ___ been exposed to ionizing radiation.

Answer 28

Radiation Dose and Radiation-Induced Leukemia

Epidemiologic data about the Hiroshima atomic bomb survivors

• Indicate the chance of contracting leukemia as a result of exposure to radiation is directly proportional to the magnitude of the radiation exposure
• Radiation-induced leukemia is assumed to follow a linear nonthreshold dose-response relationship compared with leukemia in a population that has not been exposed to ionizing radiation.

Question 29

Radiation Dose and Radiation-Induced Leukemia

More recent reevaluation of the quantity and type of radiation that was released in the cities of Hiroshima and Nagasaki provides a better foundation for radiation dose and damage assessment.

Originally, ___ were credited with the damage in Hiroshima.

When more recent studies revealed that the ___-fueled bomb dropped on Hiroshima provided more ___ radiation exposure and less ___ exposure than previously believed, data on the survivors were updated to reflect this more accurate information.

Researchers established that ___ radiation and ___ each provided about ___% of the radiation dose inflicted on the population of Hiroshima.

Answer 29

Radiation Dose and Radiation-Induced Leukemia

More recent reevaluation of the quantity and type of radiation that was released in the cities of Hiroshima and Nagasaki provides a better foundation for radiation dose and damage assessment.

Originally, neutrons were credited with the damage in Hiroshima.

When more recent studies revealed that the uranium-fueled bomb dropped on Hiroshima provided more gamma radiation exposure and less neutron exposure than previously believed, data on the survivors were updated to reflect this more accurate information.

Researchers established that gamma radiation and neutrons each provided about 50% of the radiation dose inflicted on the population of Hiroshima.

Question 30

Radiation Dose and Radiation-Induced Leukemia

Inhabitants of Nagasaki, who were exposed to a ___ bomb, received only ___% of their exposure from ___ and ___% from ___ radiation.

Based on the revised atomic bomb data, radiation-induced leukemias and solid tumors in the survivors may be attributed predominantly to ___ radiation exposure.

Impact of atomic bomb dosimetry revision
There is a significant increase in cancer risk estimates for both ___ and ___ radiation.

Answer 30

Radiation Dose and Radiation-Induced Leukemia

Inhabitants of Nagasaki, who were exposed to a plutonium bomb, received only 10% of their exposure from neutrons and 90% from gamma radiation.

Based on the revised atomic bomb data, radiation-induced leukemias and solid tumors in the survivors may be attributed predominantly to gamma radiation exposure.

Impact of atomic bomb dosimetry revision
There is a significant increase in cancer risk estimates for both gamma and x-radiation.

Question 31

Evacuees from the Chernobyl Nuclear Disaster

Need for ___ studies

Evacuation of people within ___ hours after the accident

___ effects of the accident

Attempts by physicians to prevent ___ cancer in ___

• Administration of ___ ___ to children in Poland and other countries after the Chernobyl disaster

Incidence of ___ cancer and ___ cancer since the accident

Why early studies did not demonstrate a significant increase in the incidence of ___ after the accident

Subsequent findings

Need for continuing epidemiologic studies

The ___ project

Answer 31

Evacuees from the Chernobyl Nuclear Disaster

Need for follow-up studies

Evacuation of people within 36 hours after the accident

Worldwide effects of the accident

Attempts by physicians to prevent thyroid cancer in children

• Administration of potassium iodide to children in Poland and other countries after the Chernobyl disaster

Incidence of thyroid cancer and breast cancer since the accident

Why early studies did not demonstrate a significant increase in the incidence of leukemia after the accident

Subsequent findings

Need for continuing epidemiologic studies

The ETHOS project

Question 32

Life Span Shortening

___ studies, ___ studies

American ___

American ___ ___

Risk of dying from any type of ___ in technologists working before 1940

Risk of dying from any type of ___ in technologists working after 1940

Risk of dying from ___ in technologists working before 1950

Risk of dying from ___ in technologists working after 1950

Answer 32

Life Span Shortening

Animal studies, human studies

American radiologists

American radiologic technologists

Risk of dying from any type of cancer in technologists working before 1940

Risk of dying from any type of cancer in technologists working after 1940

Risk of dying from leukemia in technologists working before 1950

Risk of dying from leukemia in technologists working after 1950

Question 33

Cataractogenesis

There is a high probability that a single dose of approximately ___ Gy will induce the formation of ___.

Result
Partial or complete loss of ___
Results of laboratory experiments with ___
Radiation-induced cataracts in humans follow a ___, ___ dose-response relationship

Evidence of human radiation cataractogenesis

Answer 33

Cataractogenesis

There is a high probability that a single dose of approximately 2 Gy will induce the formation of cataracts.

Result
Partial or complete loss of vision
Results of laboratory experiments with mice
Radiation-induced cataracts in humans follow a threshold, nonlinear dose-response relationship

Evidence of human radiation cataractogenesis

Question 34

Cataractogenesis

Answer 34

Cataractogenesis

Question 35

Embryologic Effects (Birth Defects)

Stages of gestation in humans
• ___
• ___
• ___ stage

Embryonic cell radiosensitivity during the ___ trimester of pregnancy
Embryonic cell radiosensitivity during the ___ and ___ trimesters of pregnancy
Embryonic effects resulting from the ___ nuclear power plant accident
• Review of fetal effects by ___
• International Chernobyl project
• Effects of ___-level ionizing radiation on the embryo-fetus

Answer 35

Embryologic Effects (Birth Defects)

Stages of gestation in humans
• Preimplantation
• Organogenesis
• Fetal stage

Embryonic cell radiosensitivity during the first trimester of pregnancy
Embryonic cell radiosensitivity during the second and third trimesters of pregnancy
Embryonic effects resulting from the Chernobyl nuclear power plant accident
• Review of fetal effects by UNSCEAR
• International Chernobyl project
• Effects of low-level ionizing radiation on the embryo-fetus

Question 36

Genetic (Hereditary) Effects

Biologic effects of ionizing radiation on ___ generations

___ of genetic (hereditary) mutations

Radiation-induced damage to the ___ molecule in the ___ or ___ of an adult

Natural ___ mutations

Resultant ___ disorders or ___

Mutagens responsible for ___ mutations

Radiation interaction with DNA ___

Cellular damage repair by ___

Incapacities of ___ genes

___ or ___ point mutations

Ionizing radiation as a ___ of genetic (hereditary) effects

Radiation-induced genetic effects in humans

Answer 36

Genetic (Hereditary) Effects

Biologic effects of ionizing radiation on future generations

Cause of genetic (hereditary) mutations

Radiation-induced damage to the DNA molecule in the sperm or ova of an adult

Natural spontaneous mutations

Resultant genetic disorders or diseases

Mutagens responsible for genetic mutations

Radiation interaction with DNA macromolecules

Cellular damage repair by enzymes

Incapacities of mutant genes

Dominant or recessive point mutations

Ionizing radiation as a cause of genetic (hereditary) effects

Radiation-induced genetic effects in humans

Question 37

Doubling Dose Concept

Doubling dose is the radiation dose that causes the number of ___ mutations occurring in a given generation to increase to ___ times their original number.

The radiation doubling equivalent dose for humans, as determined from studies of the children of the atomic bomb survivors of Hiroshima and Nagasaki, is estimated to have a mean value of ___ Sv.

Answer 37

Doubling Dose Concept

Doubling dose is the radiation dose that causes the number of spontaneous mutations occurring in a given generation to increase to two times their original number.

The radiation doubling equivalent dose for humans, as determined from studies of the children of the atomic bomb survivors of Hiroshima and Nagasaki, is estimated to have a mean value of 1.56 Sv.