This Glossary has been prepared to give you a brief definition of the most
commonly used terms.
ACUTE or ACUTE EXPOSURE
An acute exposure is one that took place over a short period of time - hours or days.
Acute may also be used to refer to the short-term effects of exposure to radiation.
ALPHA PARTICLE or ALPHA RADIATION
Alpha particles are positively charged particles made up of two protons and two
neutrons. The particles lose their energy quickly and do not penetrate the surface of
your skin if you are exposed externally. Alpha particles can enter the body through a cut
in the skin, by ingestion, or inhalation. Alpha-emitting radioactive substances are
harmful once inside the body. Uranium-238 and plutonium-239 are sources of alpha
radiation.
ANIMAL STUDY
For ethical and practical reasons, many experiments cannot be conducted on humans.
Laboratory experiments are conducted on animals to provide information that may be
useful in predicting how humans respond to similar exposures or conditions.
ASSOCIATION or RELATIONSHIP or CONNECTION
A relationship, generally demonstrated by statistical test, between an exposure and a health effect. It does not necessarily imply cause and effect.
ATOM
The atom is the basic component of all matter. It is the smallest part of an element and
has all the chemical properties of that element. Atoms are made up of protons and
neutrons (in the nucleus) and electrons.
ATOMIC VETERAN
This refers to military personnel exposed to atomic radiation during the period of
atmospheric atomic bomb testing from 1945 to 1963. An estimated 300,000 people are
considered atomic veterans, including U.S. military personnel exposed at Hiroshima
and Nagasaki during the American occupation of Japan following the detonation of the
atomic bombs.
ATSDR
Agency for Toxic Substances and Disease Registry
AUTOANTIBODIES
Proteins that act against the protection mechanisms within one's own body.
AUTOIMMUNE DISEASE or AUTOIMMUNE DISORDER
An autoimmune disease is a disease caused by the immune system attacking the cells of
one's own body rather than attacking foreign cells, such as germs.
AUTOIMMUNE HYPOTHYROIDISM
Autoimmune hypothyroidism: An autoimmune disease that prevents the thyroid from
producing enough thyroid hormone.
AUTOIMMUNE THYROIDITIS
Damage to the thyroid caused when the body's immune system attacks and destoys cells in the thyroid. This can be radiation induced. If this damage is significant enough, a person may develop signs and symptoms due to hypothyroidism. However, there may be no signs or symptoms. When there are no signs or symptoms of hypothyroidism, autoimmune thyroiditis is generally not a cause for concern from
producing enough thyroid hormone.
BACKGROUND RADIATION
Background radiation refers to the amount of radiation to which a person is exposed
from natural sources. Natural sources of background radiation include radioactive
substances in the soil, cosmic radiation originating in outer space, and naturally
occurring radionuclides deposited in the human body. On average, a person in the United States gets a dose to the thyroid of approximately 100 millirad per yer from background radiation.
BEIR V
The latest National Research Council's Committee on Biological Effects of Ionizing
Radiations is known as BEIR V. The Committee's report is Health Effects of Exposure to
Low Levels of Ionizing Radiation.
BENIGN
Benign refers to the non-cancerous character of a growth in the body.
BENIGN TUMOR OR BENIGN GROWTH
A non-cancerous, yet abnormal growth. Benign tumors usually grow slowly and do not spread to other parts of the body. Benign tumors are usually
not referred to as cancer.
BETA PARTICLES OR BETA RADIATION
Beta particles are fast moving electrons which are negatively charged particles. Beta
radiation can penetrate a few millimeters in human tissue before losing all of its energy.
Beta particles may also interact with living tissue by entering from inside the body through breathing contaminated foods. Iodine-131, phosphorus-32, and strontium-90 are all sources of beta radiation.
BIAS
In epidemiology, this term does not refer to an opinion or a point of view. Bias is the result of some systematic flaw in the design of a study, the collection of data, or in the analysis of data. Bias is not a chance of occurrence.
BIOACCUMULATION
The build-up in an organism of a substance found in its environment.
BIOLOGICAL HALF-LIFE
This is the amount of time it takes for the human body to eliminate 50 percent of a
radioactive substance through natural excretory functions: urination, defecation,
exhalation, and perspiration.
BIOSTATISTICIAN
A scientist who uses statistical processes and methods to analyze biological data is a
biostatistician. Statistics is a branch of mathematics dealing with the collection, analysis,
interpretation, and presentation of large quantities of numerical facts.
BODY BURDEN
The amount of radioactive material in a person's body.
CANCER
Cancer refers to a malignant growth, capable of invading surrounding tissue or
spreading to other parts of the body.
CARCINOGEN
This is an agent that may cause cancer. Ionizing radiations are physical carcinogens;
there are also chemical and biologic carcinogens. Biologic carcinogens may be external
(such as a virus) or internal (such as genetic defects).
CASE-CONTROL STUDY
A case-control study is a common type of epidemiologic study. Two groups of people are
selected based on the presence or absence of a disease or specific health problem of
interest. Individuals in one group have the disease or health problem; individuals in
the other group do not. Information is collected in the same way from individuals in
both groups regarding specific exposures they have experienced in the past, and/or
personal characteristics that might have caused the disease. The two groups are then
compared to determine the degree to which the exposures or characteristics of interest
are related to the development of the disease or health problem under study.
CDC
Centers for Disease Control and Prevention
CHANCE
A situation in which something happens unpredictably without discernable human intention or observable cause.
CHROMOSOME
One of 46 bodies in the human cell nucleus that is the bearer of genes. Genes transmit
and determine inherited characteristics.
CHRONIC EXPOSURE
A chronic exposure is one that occurred over a long period of time - weeks, months or
years.
CLINICAL STUDY
A clinical study is any human study involving clinical information or conducted in a
clinical setting.
COHORT STUDY
A study involving a group of people who either have or do not have a certain factor,
such as exposure to a disease-causing agent. Such studies are usually used to compare
disease rates.
COMPUTER MODEL
A series of mathematical formulas that a computer uses to analyze information rapidly. Computer models are used to estimate what has happened or predict what might happen in the real world.
CONFIDENCE LIMITS
The highest and lowest boundaries in a confidence interval. As used here, a confidence interval accounts for the possibility that different groups of individuals might have different risk estimates even if they have the same range of dose estimates. Because there is uncertainty in risk estimates that are made for different radiation dose levels, scientists often include a confidence interval with a risk estimate.
CONFOUNDING FACTORS
Any characteristic that makes it difficult to compare two or more
distinct groups in an epidemiologic study. Confounding factors can mask a health
effect so that the relationship of the effect and the exposure is not recognized. They can
also make it appear as though there is
an effect when, in fact, none exists.
CONTAMINATED or CONTAMINATION
See Radioactive Contamination
COSMIC RADIATION or COSMIC RAYS
Ionizing radiation that originates from our sun and other stars in the universe. Cosmic rays are
penetrating bundles of energy like gamma rays, but most are filtered out by the earth's
atmosphere. The higher in altitude we go (e.g. mountains, jets), the more we can be
exposed to them. Cosmic rays are part of background radiation.
CRITICAL MASS
The amount of nuclear fuel needed for a chain reaction to take place is the critical mass.
For example, about 22 pounds of uranium-235 and 11 pounds of plutonium-239 are
necessary for a chain reaction.
CUMULATIVE EFFECT
Cumulative effect refers to the idea that chronic exposure to radiation increases the
danger of cancer and leukemia because there is an increase in the total amount of
radiation delivered to a particular tissue. The risk of disease from radiation exposure results from the total, or cumulative, dose received from all sources.
CURIE (abbreviated Ci)
A curie is a measure of radioactive material. It measures the number of atoms that
decay each second. One curie is 37 billion atoms undergoing decay each second. Hanford
released approximately 725,000 curies of iodine-131 between 1944 to 1957. In contrast, the 1979
accident at the Three Mile Island nuclear power plant in Pennsylvania was estimated to
have released between 15 to 24 curies of radioactive iodine-131. A "nanocurie" is one
billionth of a curie. A "picocurie" is one trillionth of a curie.
DATA
Data are factual information used as a basis for reasoning, discussion or calculation.
DECAY
See RADIOACTIVE DECAY
DELAYED EFFECT or DELAYED HEALTH EFFECT
A health effect of radiation exposure which does not become apparent for months, years or several decades or more after the exposure occurs.
DISEASE RATE
The rate at which disease occurs in a population. It is usually expressed as the number of cases per 100,000 people per year. Rates (rather than raw numbers) are needed to compare the disease experience of populations at different times, different places, or among different groups of people. (Same as
MORBIDITY RATE.
DNA
Deoxyribonucleic acid, or DNA, is the highly complex part of each cell that carries all
genetic characteristics of the total organism.
DOE
Department of Energy - A cabinet-level department of the United States government. It
is responsible for the development of nuclear weapons material (plutonium, uranium
and tritium). DOE also has responsibility for cleaning up nuclear and chemical wastes
that were generated by U.S. nuclear weapons programs, including the management of
the Hanford Site. DOE sponsors research and development of more efficient ways of
energy production. It was created in 1977 and took over the functions of the Energy
Research and Development Administration (ERDA). Prior to DOE and ERDA, the
Atomic Energy Commission (AEC) had the responsibility for the nuclear weapons
complex.
DOSE
Dose is the quantity of radiation or energy absorbed by the body. It is measured in
rad, millirad, Gray or milliGray.
DOSE EQUIVALENT
This is the measure that indicates the degree of biological damage caused by radiation.
Dose equivalent is measured in rems.
DOSE ESTIMATE
A calculation of the approximate amount of radiation absorbed by all or part of a person's body. When dose cannot be measured precisely (such as when the exposure happened in the past), a dose estimate is used.
DOSE RECONSTRUCTION
A scientific study that estimates doses to people from releases of radioactivity or other
pollutants. The reconstruction is done by determining how much pollution was
released, how people came in contact with it and the amount absorbed by all or part of their bodies.
DOSE-RESPONSE RELATIONSHIP
The observation that the amount of disease increases as the dose or level of exposure increases.
DOSIMETER
A device for measuring doses of radiation is a dosimeter.
DOWNWINDER
Downwinder is a commonly used term which refers to people living in the pathway of
radioactive emissions from a nuclear plant or from atomic bomb test sites.
EFFECTIVE DOSE EQUIVALENT (EDE)
A radiation dose to one part of the body does not have the same potential health effect
as a dose to another part. The EDE is used to put different types of radiation doses on an
equivalent basis in terms of their potential for causing damage.
EFFECTIVE HALF-LIFE
The effective half-life is a measurement based on both the physical and biological
half-lives of a radioisotope. It is the time required to reduce the radioactivity in a tissue
or organ by 50 percent, taking both physical and biological half-life into account.
ENDOCRINOLOGIST
An endocrinologist is a medical doctor who specializes in diseases and disorders of the
endocrine system (such as thyroid diseases and diabetes). The endocrine system refers to
glands in the body that release their products directly into the blood. The thyroid gland,
for example, releases thyroid hormone into the blood.
ENVIRONMENTAL EXPOSURE
Exposure to substances through the environment.
EPIDEMIOLOGY
The branch of medical science that deals with the frequency and distribution of disease
in human populations is known as epidemiology.
ETIOLOGY
Etiology refers to the cause or causes of disease.
EXPOSURE PATHWAYS
The ways in which a plant, animal or person is exposed to radioactivity or pollution. Key exposure pathways are air and water. Most exposures happen through breathing air, drinking water and/or eating foods that are contaminated, and by direct radiation.
EXTERNAL RADIATION or EXTERNAL EXPOSURE
Radiation exposure from a source outside the body. The term refers to
radiation, such as gamma rays and X-rays, that can penetrate human skin and thus
cause biological damage from outside the body. Compare to internal exposure.
FALLOUT
See NUCLEAR FALLOUT
FINE NEEDLE ASPIRATION
See THYROID FINE NEEDLE ASPIRATION
FIVE-YEAR SURVIVAL RATE
For cancer, the percentage of people (the number of people out of 100) diagnosed with cancer who have not died of cancer within five years of diagnosis.
FREE RADICALS
A highly reactive molecule that can damage cells and lead to cancer or other diseases.
FREEDOM OF INFORMATION ACT (FOIA)
A law of the United States intended to assure government openess and accountability.
It establishes that citizens have the right of access to federal agency records. Enacted in 1966,
the Act also defines specific kinds of information that the government can exempt from disclosure.
GAMMA RAYS or GAMMA RADIATION
A high-energy electromagnetic, ionizing radiation that comes from the nucleus of an
atom undergoing radioactive decay. Gamma rays are similar to medical X-rays but are emitted at very specific energies characteristic of their decaying atoms. Gamma rays penetrate body tissues and may damage cells. People exposed to the atomic bombings of Hiroshima and Nagasaki were exposed to gamma radiation. Cesium-137 is a source of gamma radiation.
GENE
A gene carries inherited characteristics from generation to generation.
GENETIC EFFECTS
A genetic effect is the result of exposure to radioactivity or substances that cause damage to the genes of a reproductive cell (sperm or egg) which can then be passed from one generation to another.
GENETIC INJURY or GENETIC DAMAGE
Genetic injury is harm to a person's genes which can be passed on to subsequent
generations.
GERM CELLS
Germ cells are reproductive cells - spermatozoa (sperm) in males and ova (eggs) in
women.
GONADS
Gonads are reproductive organs - testes in men and ovaries in women.
GRAVES' DISEASE
Graves' disease: A form of hyperthyroidism (an over-active thyroid).
GRAY (abbreviated Gy)
A unit of measure of radioactive energy absorbed by all or part of the body. 1 Gray equals 100
rad.
GREEN RUN
A secret intentional release from Hanford of between 7,000 and 12,000 curies of iodine-131 to the air on December 2-3, 1949. This experiment was called the Green Run because it involved a processing run of nuclear fuel that had cooled for only a short time (16 days) and was, therefore,
green. This shorter cooling time meant that the iodine-131 had less time to decay to lower levels.
HALF-LIFE
A half-life is the amount of time it takes for a radioactive substance to decay by releasing
radioactive particles or waves, and to lose one-half of its radioactivity. Half-lives for
different substances vary from millionths of a second to billions of years. Iodine-131
has a half-life of eight days. At the end of eight days, half of the Iodine-131 becomes
stable xenon-131. After another eight days, half of the remaining Iodine 131 will decay into stable xenon-131, and so on. When an atom decays and becomes stable, it is no longer radioactive.
HASHIMOTO'S THYROIDITIS
An autoimmune disease of the thyroid. It is caused by lymphocytes entering the thyroid. The
disease causes goiters, tissue damage and hypothyroidism.
HEALTH EFFECT
The result of exposure to substances (such as radiation) that cause any harm to a person's health. It includes diseases, cancers, birth defects, genetic effects and death.
HEALTH PHYSICS
The profession that deals with radiation and health, and radiation protection standards.
(THE) HEALTHY WORKER EFFECT
Lower rates of disease in working populations compared to the general population. The work force is generally healthier than the population at large.
HEDR
Hanford Environmental Dose Reconstruction Project
HEDR STUDY AREA
A 75,000 square-mile area that the HEDR Project used to study exposure from Hanford's radioactive releases into the air. The area extends from central Oregon to northern Washington, and from the crest of the Cascade Mountains to the eastern edge of northern Idaho.
HHES
Hanford Health Effects Subcommittee
HHIA
Hanford Health Information Archives
HHIN
Hanford Health Information Network
HIBAKUSHA
The Japanese term for the World War II victims of the atomic bombs dropped on the
cities of Hiroshima and Nagasaki.
HORMESIS
Hormesis refers to the speculation, in radiation science, that there may be some
beneficial health effects from low-doses of ionizing radiation.
HOT PARTICLE
A small piece of material that is radioactive.
HOTSPOTS
An area where the concentration of contaminants is greater than in the surrounding area. Hot spots generally form because of variations in the wind and weather patterns and in the earth's surface (such as hills and valleys that cause air pockets).
HTDS
Hanford Thyroid Disease Study
HYPERPARATHYROIDISM
A condition caused by too much parathyroid hormone in the body. This results in the
body not being able to properly regulate the levels of calcium and phosphorus.
HYPERTHYROIDISM
Hyperthyroidism is a condition caused by an over-active thyroid gland which secretes
greater-than-normal amounts of thyroid hormones. Symptoms include nervousness, constant hunger, weight loss and tremors. Scientists do not believe hyperthyroidism is caused by radiation exposure.
HYPOTHYROIDISM
Hypothyroidism is a condition caused by too little thyroid hormone in the body. Symptoms include fatigue, weight gain, intolerance to cold, decreased appetite, constipation, hoarseness, menstrual irregularities, dry skin and hair changes.
IDA
Hanford Individual Dose Assessment Project
IMMUNE SYSTEM DISORDERS or IMMUNE DYSFUNCTIONS
These include allergic reactions and disruption of the immune surveillance system
whose prime function is to detect and eliminate diseased cells.
IN UTERO
In utero means in the uterus or womb.
INCIDENCE
A measure of the new cases (in the form of a count or rate) of a disease or condition that occur in a specified population within a certain period.
INGESTION DOSE PATHWAY
The parts of the food chain or water system that might add to radiation exposure from
eating food or drinking water is the ingestion dose pathway.
INSOLUBLE MATERIAL
It does not readily dissolve in a liquid (such as blood or water).
INTERNAL RADIATION or INTERNAL EXPOSURE or INTERNAL RADIATION EXPOSURE
Internal radiation exposure occurs when a radioactive substance is taken into the body
by eating, drinking or breathing. Compare to external exposure.
INTERNATIONAL RADIATION SIGN
These signs have a magenta colored "trefoil" (French for "three-leafed") symbol on a
yellow background. They are used to label containers, vehicles and areas that contain
radioactivity.
IODINE
Iodine is a chemical element in our diet with which thyroid hormone is made.
IODINE 131
One of several radioactive forms of iodine. Iodine 131 gives off beta radiation. It has a half-life of about eight days. Hanford released large amounts of iodine 131 in the process of producing plutonium for nuclear weapons. The HEDR Project concluded that iodine 131 accounted for more than 98 percent of the dose that most people received from Hanford�s radioactive releases to the air. The most likely health problems from exposure to iodine 131 are thyroid diseases, particularly benign thyroid tumors (or nodules). It is important to know that there are also beneficial medical uses of iodine 131, with an excellent safety record. These include using iodine 131 for diagnosis, and to treat hyperthyroidism and thyroid cancer.
IONIZING RADIATION
Radiation with enough energy to remove one or more electrons from atoms it encounters, creating ions inside living cells. (An ion is an atom that carries a positive or negative electrical charge.) Ionizing radiation leaves positively charged particles such as alpha and beta, and non-particulate forms such as X-rays and gamma radiation. These ions can damage key substances in cells, including the DNA. Such damage can lead to cancer or other defects.
ISOTOPES
Isotopes are different forms of the same chemical element, which have different numbers of
neutrons but the same number of protons in the nucleus of their atoms. A single element may have many isotopes. For example, stable iodine is iodine-127. Its radioactive isotopes include iodine-129 and
iodine-131.
LATE EFFECTS
See DELAYED EFFECT
occurs.
LATENT PERIOD or LATENCY PERIOD
The period of time between exposure to radiation and when its effects are detectable. For example, after exposure to a dose of radiation, there is a delay of a few to many years before cancers are detectable.
LEUKEMIA
A form of cancer of blood cells. The disease often results in a progressive
increase of white blood cells.
LINEAR EFFECT MODEL
A model of radiation health effects based on the theory that the damage per rad is
proportional. That is, the number of induced cancers is directly proportional to the dose
of radiation delivered, down to the lowest possible dose.
LINEAR-QUADRATIC EFFECT MODEL
A model of radiation health effects based on the theory that less damage occurs per rad is proportional. That is, the number of induced cancers is directly proportional to the dose of radiation delivered, down to the lowest possible dose.
LOS ALAMOS
Place in northern New Mexico where government scientists have designed and developed
nuclear weapons since 1943.
LYMPHOCYTE
A type of white blood cell that is primarily found in lymph nodes. Lymphocytes provide
protection against some kinds of infections.
LYMPHOPOIETIC NEOPLASM
A tumor consisting of lymphocytes. It can be either benign or cancerous.
MALIGNANT
Cancerous. a malignant tumor invades nearby tissue and is able to spread (metastasize) through the blood or lymph system to other parts of the body.
THE MANHATTAN PROJECT
This is the name of the United States Government scientific/military project, begun in
1942, that developed the world's first uranium reactor and the first atomic bomb.
Hanford was part of the Manhattan Project, producing plutonium used in the atomic
bomb dropped on Nagasaki, Japan.
MEDIAN or MEDIAN DOSE
The central estimate in a dose estimate range. Half the possible doses are above the median; half are below it. A person�s actual dose is more likely to be near the median than near the low or the high end of the dose estimate range.
MEDICAL MONITORING
A program to screen a group of people who are at risk for specific diseases or conditions and to refer individuals for additional evaluation and treatment, if needed. Monitoring does not include medical care. The ATSDR has proposed a medical monitoring program for people who were exposed as children to Hanford�s radioactive releases of iodine 131, who have an estimated median thyroid dose of 10 rad (10,000
millirad) or more, and who meet certain other criteria.
METASBOLISM
The physical and chemical processes in the body that make energy and nutrients available to cells. The thyroid gland makes hormones that control metabolism.
METASTASIS
Metastasis is the spread of cancer from the original site of the disease to another part of
the body.
MILLIGRAY (abbreviated mGy)
A milliGray is one one-thousandth (1/1,000) of a Gray. One milliGray equals 100
millirad. The HTDS will measure doses in milliGray.
MILLIRAD (abbreviated mrad)
One one-thousandth (1/1000) of a rad. To change a rad, divide by 1,000. A dental X-ray gives a thyroid dose of about 3
millirad. The Hanford IDA Project is providing thyroid dose estimates in
millirad.
MILLIREM (abbreviated mrem)
A millirem (mrem) is one-thousandth (1/1000) of a rem. See REM
The smallest unit of a substance which has all its characteristic chemical properties is
called a molecule.
MORBIDITY RATE
The morbidity rate is the rate at which people get a disease. It is usually expressed as the
number of cases per 100,000 people per year.
MORTALITY RATE
The mortality rate is the rate at which people die from a disease, such as a specific type of
cancer. It is usually expressed as the number of deaths from the disease per 100,000
deaths per year.
MULTIPLE MYELOMA
A rare disease that occurs more frequently in men than women. It is characterized by anemia, bleeding,
recurrent infections and weakness. Ordinarily, it is regarded as a form of cancer that originates in bone marrow and involves mainly the bones.
MUTATION or MUTATED
Mutation means that a change has occurred.
NANOCURIE
One billionth of a curie (10-9). The abbreviation is nCi. The curie is a measurement of
radioactive decay. One curie equals 37 billion atoms decaying per second.
A neoplasm is a new and abnormal growth of tissue. A neoplasm can be cancerous or
non-cancerous. Cancerous neoplasms can be invasive, widespread or seeded.
Non-cancerous neoplasms can be localized and contained, but may harm other normal
tissue by local pressure or displacement.
NEURAL TUBE DEFECTS
The neural tube develops into the spinal cord and brain. Defects occur when the
neural tube fails to close completely during the early stages of pregnancy.
NIOSH
National Institute for Occupational Safety and Health
NO THRESHOLD PREMISE
This is the premise that there is no level below which exposure to radiation does not
increase the risk of cancer. Any dose of ionizing radiation can increase the risk of
developing cancer in many organs and tissues of the body.
NODULE
See THYROID NODULES
NON-IONIZING RADIATION
Non-ionizing radiation is not capable of removing an electron from an atom. This
includes visible, ultraviolet and infrared light, as well as radio waves.
NUCLEAR FALLOUT
Fallout is the descent of airborne particles of dust, debris, and radioactive substances.
About 200 different substances are formed from a nuclear bomb explosion. Millions of
curies of radioactivity in the form of dust and debris get carried into the upper
atmosphere by the mushroom cloud. Jet stream winds can carry fallout from bomb
blasts around the world within a few months.
NUCLEAR FISSION
Nuclear fission is the splitting of an atom which releases energy.
NUCLEUS
The nucleus is the center of an atom.
NUCLIDES
See RADIONUCLIDE
OCCUPATIONAL EXPOSURE
Exposure to substances at the workplace.
ODDS
A measure of the likelihood that an event will occur. For example, the odds of developing a certain disease.
ONCOLOGIST
An oncologist is a medical doctor who cares for patients with cancer.
ORGAN DOSE
Among the factors to consider in measuring radiation dose is whether a person received
a radiation dose to a single organ or to the whole body. For example, when iodine-131
enters the body, it mainly concentrates in the thyroid gland and gives a dose to this
organ.
PARATHYROIDS or PARATHYROID GLANDS
Any of four small glands next to or on the thyroid gland. The parathyroids secrete a hormone that helps control the balance between calcium and phosphorus in the body.
PLUTONIUM
A silvery-white radioactive metal that exists as a solid under normal conditions. It is produced when uranium absorbs a neutron. Small amounts of plutonium occur in nature, but large amounts have been artificially produced in nuclear reactors. Hanford produced plutonium for use in nuclear weapons. Most forms of plutonium have very long half-lives. For example, plutonium 239 (which Hanford produced) has a half-life of 24,100 years. Plutonium can cause cancer.
POWER
The probability that a study can distinguish between a true exposure-to-disease relationship and a coincidence. The power of a study depends on the size of a study population, the amount of radiation exposure and the number of cases of the disease under investigation.
PREVALENCE
The proportion of people who have a disease at a specific point in time.
PROSPECTIVE STUDY
A study in which two groups of people - one exposed and one unexposed - are followed
forward in time (prospective) to determine the possible linkage between exposure and
health effects.
PUBLIC HEALTH ACTIVITIES
Activities conducted to protect, promote or restore public health. The activities can include a number of programs and campaigns such as surveillance of disease, epidemiological studies, disease registries, collection of vital statistics, disease prevention programs, public and provider education, health inspections, and quality assurance activities.
RAD
A rad is a measure of the amount of energy absorbed by the body.
RADIATION
Energy in the form of particles or waves given off by certain atoms. Familiar forms of radiation are heat, light, radio waves and microwaves. Ionizing radiation is a very high-energy form of radiation. It is invisible and cannot be sensed without the use of special equipment. Ionizing radiation can cause cell damage.
RADIATION DOSE
See DOSE
RADIATION STANDARDS
A set of regulatory controls that limit exposure to radiation.
RADIOACTIVE
Something is radioactive when it gives off particles or rays from an atom's nucleus.
RADIOACTIVE CONTAMINATION
Radioactive materials spread over an area, equipment or an individual.
RADIOACTIVE DECAY
Radioactive decay is the process by which the atoms in radioactive substances release
energy. Radioactive decay produces a new substance which may or may not be
radioactive. For example, iodine-131 decays to non-radioactive (stable) xenon-131.
RADIOACTIVE MATERIALS
Materials that contain unstable (radioactive) atoms. Radioactive materials give off radiation when they decay.
RADIOACTIVITY
Radioactivity is the spontaneous release of radiation from the nucleus of an atom.
RADIOBIOLOGY
This is a branch of biology which deals with the interaction of biological systems and
radiant energy or radioactive materials.
RADIOISOTOPE
The radioactive form of an element that has all the chemical properties of the stable
form of the element is a radioisotope. The radioisotope undergoes radioactive decay.
RADIONUCLIDE or RADIOACTIVE ISOTOPE
An unstable form of an element that can decay and give off radiation. Each radionuclide has a distinct atomic weight number. For example, iodine 131 and iodine 129 are different radionuclides of iodine.
RADIOPHOBIA
This is a word used to describe the fear of radioactivity.
RADIOSENSITIVITY
Radiosensitivity describes how cells, tissues, organs and other organisms are sensitive
to, and can be harmed by radiation.
RADON
Radon is a colorless, odorless, radioactive gas which is heavier than air. It comes from
the decay of radium in soil. Radon lingers in low areas such as basements and crawl spaces
under buildings and can build up to high concentrations in unventilated areas. If
inhaled for long periods of time, it may cause lung cancer.
RATIO
A measure of association calculated by dividing one amount by another.
RELATIVE RISK or RISK RATIO
A ratio comparison of two risk estimates. Relative risk indicates the increased or decreased degree of risk among exposed subjects compared with unexposed persons. A relative risk of 1 indicates no association between the exposure and the disease. A relative risk of 2 indicates that the exposed group is twice as likely as the unexposed group to experience the health effect being studied.
REM
A rem reflects the radiation dose received by the body, after accounting for the potential
for harm from different types of radiation. To convert rads to rems, the number of rads
is multiplied by a number that reflects the potential for damage caused by a type of
radiation. For beta, gamma and X-ray radiation, this number is generally one. For
some neutrons, protons, or alpha particles, the number is twenty. A millirem (mrem)
is one-thousandth (1/1,000) of a rem.
REPRESENTATIVE DOSE ESTIMATE
A dose estimate for a typical or hypothetical individual who represents a larger group of people. This estimate is often based upon lifestyle factors.
RISK
The likelihood that an individual will get a certain disease in a specific period of time. A risk estimate usually measures risk in terms of probability: the number of chances in 100 that a person will get a disease.
RISK FACTOR
An aspect of personal behavior or lifestyle, an environmental exposure, or an inborn or inherited characteristic that is known from scientific evidence to be associated with a health effect.
SAMPLE SIZE
The number of participants in a research study. The larger the sample size in a research study, the more power the study has to detect an association between exposure and a health effect.
SCOPING STUDY
The use of preliminary information about environmental releases from a site to calculate
an upper estimate to guide further work. The study's aim is to estimate which contaminants contributed significantly to the public's dose.
SIEVERT
1 Sievert equals 100 rem. Abbreviation is Sv.
SOLUBLE MATERIAL
It readily dissolves in a liquid (such as blood or water).
SOMATIC EFFECTS
The effects of radiation exposure that result from damage to non-reproductive cells. If the number of cells which suffer somatic effects is great enough, then the damage becomes clinically observable.
SOMATIC INJURY
This is an injury to the body of a person exposed to radiation which is not passed on to
succeeding generations.
SOURCE TERM
Source term refers to the amount and type of radioactive material released into the
environment.
SPONTANEOUS ABORTION
Spontaneous abortion means a miscarriage.
STABLE
A substance that is not radioactive.
STATISTICS
Statistics is a branch of mathematics dealing with the collection, analysis, interpretation
and presentation of numerical data.
STATISTIC SIGNIFICANCE
The likelihood that an association bewtween exposure and disease risk that a study finds could not have occurred by chance alone. The statistical significance is assessed at the end of a study, after the results are
known.
STUDIES
Types of studies defined in this Glossary are animal, case-control, cohort, clinical and
prospective.
STUDY AREA
See HEDR study area.
SUBREGISTRY
Part of the National Exposure Registry. A registry is a system that collects, analyzes and interprets data on all new cases of a specific disease or condition for a specified time period and population. The ATSDR is developing an iodine 131 exposure subregistry to include a sample of the individuals born in three counties near Hanford between 1940 and 1951.
SUPRALINEAR EFFECT MODEL
This is a model of radiation health effects which proposes that more damage is caused
per rad at low doses than at higher doses. The theory is that high doses of radiation kill
cells outright, while lower doses of radiation weaken and damage cells which tend to
live on in an altered state.
TAB
Tribal Advisory Board
THRESHOLD HYPOTHESIS
This refers to the assumption that no radiation injury occurs below a specified dose.
THYROID or THYROID GLAND
The thyroid is a two-lobed gland lying at the base of the throat that produces hormones
essential for a variety of metabolic processes in the body. The thyroid secretes hormones that control body growth and metabolism. When iodine is ingested, much of it goes to the thyroid gland.
THYROID DOSE or THYROID DOSE ESTIMATE
The amount (or an estimate of the amount) of radiation, or energy, absorbed by the thyroid gland.
THYROID FINE NEEDLE ASPIRATION
This is a test often used when a thyroid nodule is found on the thyroid gland. Fine
needle aspiration (FNA) collects cells from the nodule to determine whether the nodule
is benign or cancerous.
THYROID FUNCTION TESTS
There are two standard blood tests commonly used to evaluate thyroid function: (1) the
measurement of thyroid hormone, referred to as T4, and (2) the measurement of
thyrotropin, or the thyroid-stimulating hormone commonly called TSH. TSH is a
hormone released by the pituitary gland near the brain that controls thyroid hormone
production. When the thyroid gland is not working properly, the pituitary releases large
amounts of TSH to try to stimulate the thyroid gland into producing thyroid hormone.
The TSH circulating in the blood stream thus indicates thyroid failure.
THYROID NODULES
Thyroid nodules are lumps in the thyroid gland which may be benign or cancerous.
"Cold nodules" are non-functioning lumps in the thyroid gland. "Hot nodules" refer to
overactive thyroid lumps. Upon detecting a nodule, it is important to diagnose the disease that has caused it. Benign thyroid tumors are often referred to as nodules.
THYROID NUCLEAR SCAN
This test measures the absorption of a radioactive substance by the thyroid gland. The
thyroid nuclear scan can help evaluate a thyroid nodule and can provide additional
information about how the thyroid is functioning.
THYROID PALPATION
The most common procedure for checking the thyroid gland is a simple physical
examination which consists of feeling the gland in the neck with the fingers, often as
the patient swallows water. Palpation can determine the size and texture of the gland
and can also detect larger nodules.
THYROID STIMULATING HORMONE (TSH)
Thyroid stimulating hormone is a pituitary gland hormone that increases thyroid
function.
THYROID ULTRASOUND SCAN
A thyroid ultrasound scan is a test which shows a picture of the structure of the thyroid
gland by sending sound waves into the thyroid and making a picture of the reflected
sound waves. The ultrasound scan can detect very small abnormalities in the gland.
TRACHEOESOPHAGEAL FISTULA
A birth defect that is an abnormal connection between the trachea (the windpipe) and the esophagus
(the part of the digestive tract that connects the mouth to the stomach).
TSP
Technical Steering Panel for the Hanford Environmental Dose Reconstruction Project
TUMOR
An abnormal mass of tissue in the body. Tumors can be benign or cancerous (malignant). Benign tumors do not spread to other parts of the body. Malignant tumors can invade nearby normal tissues and spread (metastasize) to other parts of the body. Malignant tumors grow faster than benign tumors. Cancer is the common name for all malignant tumors.
TUMOR REGISTRY
A collection of records on the tumors that have been treated at a particular hospital or within a geographical area.
UNCERTAIN or UNCERTAINTY
The lack of precise knowledge based on the amount and quality of evidence or data available.
UPTAKE
The absorption by a tissue of some substance and its permanent or temporary retention.
WHITE BLOOD CELL COUNT
A measurement of the number of white blood cells in a specific amount of blood. The
white blood cell count can be an indication of infection or other diseases.
WHOLE BODY DOSE or WHOLE BODY RADIATION
Radiation exposure to gamma rays from outside the body can give a radiation dose to
the entire body. Each organ receives approximately the same dose.
X-RAYS or X-RAY RADIATION
A form of radiation produced outside the nucleus of the atom. X-rays can penetrate human skin and pass through the body at the speed of light. As X-rays pass through the body, they may damage cells. The properties of X-rays are identical to gamma rays. Medical X-rays are artificial or machine-made
gamma rays.
