Definitions

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Arsenic: Semi-Metal. Causes skin, lung, bladder, and kidney cancer in both sexes and with prostate cancer in men. Inorganic arsenic also is associated with numerous noncancer conditions, including gastrointestinal, vascular, neurologic, blood system, endocrine, respiratory, skin, reproductive, and developmental effects. Metal has been detected at the SSFL.

Asbestos: Mineral. The primary cause of mesothelioma, a rare cancer of the mesothelium, the membrane that covers and protects most of the body’s internal organs. Mesothelioma symptoms may not appear until 30 to 50 years after asbestos exposure. Mineral has been detected at the SSFL.

Alpha Particles Alpha particles are released from the nucleus of radioactive atoms during the process of radioactive decay. Materials that emit alpha particles are called alpha emitters, though they may emit other types of radiation as well. Alpha particles generally have a high level of energy and consist of two protons and two neutrons with a positive charge of 2. Because they are relatively heavy (in nuclear terms), alpha particles can travel only a few inches through air and can be stopped by clothing, the outside layer of skin, a sheet of paper, or other paper-thin material. As a result, alpha emitters are not a health hazard so long as they are not inhaled, ingested, or otherwise taken into the body. If alpha-emitting radioactive materials are taken into the body, they will deliver all their energy directly to a small volume of the tissue where they deposit. For example, some alpha emitters are "bone seekers" because of their chemical characteristics and may become part of the bone structure where they will deposit all their energy. Others may concentrate in body organs such as the kidneys, liver, lungs, and spleen. The primary objective in dealing with alpha emitters is contamination control, and the prevention of inhalation and ingestion because they are considered internal hazards. (DTSC Removal Action Work Plan, PDF page 251)

Americium-241: Multiple Radiation Emitter. It poses a more significant risk if ingested (swallowed) or inhaled. Once in the body, it tends to concentrate in the bone, liver, and muscle. Americium can stay in the body for decades and continue to expose the surrounding tissues to radiation, increasing the risk of developing cancer. Radionuclide has been detected at SSFL.

Background cleanup standard (aka 100% cleanup) ensures that anything brought to the SSFL is taken away from the SSFL. An extensive $41.5 million U.S. EPA $$ study was done to determine pre-exisiting background levels of radiation levels (hence background) in the area and to conduct a radiological survey of Area IV and the Northern Buffer Zone The US. EPA found over 500 samples of elevated radioactivity, in some case thousands of times above background. The AOC stated that only radiation above the background level would be remediated.’

Beta Particles Beta particles are tiny charged particles like electrons emitted from the nucleus of radioactive atoms and have an electric charge of negative 1. Beta particles can travel up to several feet through air, but can still be stopped by clothing, several layers of skin, a sheet of plastic, or thin metal. Although they can penetrate the surface layers of human skin, beta particles do not have the energy required to penetrate and expose the internal organs. Surface skin burns, similar to sunburn, can result from high exposure to beta radiation. If beta emitters are taken into the body, they will deliver their energy throughout the tissues and organs where they deposit. The primary objectives in dealing with beta emitters are contamination control, avoiding exposure to uncovered skin areas and the eyes, and prevention of inhalation and ingestion. An additional issue associated with beta emitters in relatively large quantities is the secondary X-ray radiation that can be generated when the beta particles interact with high atomic-mass materials (for example, lead and steel). As a result, plastics and aluminum are preferred shielding for beta emitters. (DTSC Removal Action Work Plan, PDF page 251)

Benzene: Chemical. May contribute to an increased risk of childhood leukemia. Benzene is a contaminant that has been detected at SSFL.

Bioaccumulation: the gradual buildup of toxins over time.

Biological half-lives: How long it takes the body to eliminate radioactive material.

Cesium-137: Multiple Radiation Emitter. Exposure to Cs-137 can increase the risk for cancer because of the presence of high-energy gamma radiation. Internal exposure to Cs-137 through ingestion or inhalation allows the radioactive material to be distributed in the soft tissues, especially muscle tissue, which increases cancer risk. Half-life is 30 years, hazardous-life is 600 years. Radionuclide has been detected at SSFL.

Cobalt-60: Gamma Emitter. External exposure to Co-60 can increase cancer risk. Most Co-60 that is ingested is excreted in feces; however, a small amount is absorbed by the liver, kidneys and bones. Cobalt-60 absorbed by the liver, kidneys, or bone tissue can cause cancer from internal exposure to gamma radiation. Radionuclide has been detected at SSFL.

Curium-243/244: Multiple Radiation Emitter. Typically quite insoluble and adheres very tightly to soil particles. This metal is very dangerous. It can accumulate in the liver, lungs, and bones and cause cancer. Radionuclide has been detected at SSFL.

Dioxins: Chemical. Carcinogenic and can cause reproductive, developmental, immunological, and endocrine side effects. Chemical has been detected at SSFL.

ELCR: Excess lifetime cancer risks. According to EPA, the acceptable ELCR is 1 person in 1,000,000. This risk can also be written as 1eE-6, 1x10^-06, 1x10⁻⁶ or 10⁻⁶.

Gamma rays Gamma rays are electromagnetic radiation like sunlight (although with a much higher frequency and energy). Unlike alpha and beta radiation, gamma rays are not particles and have no mass, but are emitted from the nucleus of many radioactive materials during radioactive decay. Because gamma rays have no mass, but can have relatively high energy, they travel long distances, are very penetrating, and difficult to stop. Gamma rays from a source external to the body are able to expose the whole body, including internal organs. The primary objective in dealing with gamma emitters is shielding to prevent external exposure. In the event of inhalation or ingestion of gamma emitters, the whole body will be exposed. (DTSC Removal Action Work Plan, PDF page 251)

Half-life is the the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay. For example, cesium 137 has a 30 year half-life. A rule of thumb is that it takes ten half-lives for a substance to be essentially gone, so it will take 300 years for cesium 137 to fully decay. However, the “daughter products” of the decayed radioactive is commonly radioactive and dangerous as well. 20 half-lives are used to determine the overall hazardous life of a radioactive element, including the daughter products. Inside the body, these elements also have biological half-lives — how long it takes the body to eliminate them.

Hazardous-life: 20 half-lives are used to determine how long a radioactive element remains dangerous to human health.

Hazard Quotient (as used in SRAM) Unlike linear dose-response assessments for cancer, non-cancer risks are generally not expressed as a probability of an individual suffering an adverse effect. Instead, "risk" for non-cancer effects is typically quantified by comparing the exposure to the reference level via a ratio known as the “hazard quotient.” Exposure to contamination at or below the reference level (HQ=1) are not likely to be associated with adverse health effects. As exposures increase above the reference level (i.e., HQs increase above 1), the potential for adverse effects also increases. The HQ, however, should not be interpreted as a probability of adverse effects.

High-level radioactive waste: High level waste is the irradiated (“spent”) fuel from nuclear reactors, liquid and sludge from reprocessing irradiated fuel, and the solid into which it is converted.

Hydrazine: (monomethyl hydrazine): Chemical has been detected at SSFL.

Iodine 131: If a person ingests iodine 131 (milk from cows fed contaminated grass is the most common source), it is quickly taken up by the thyroid gland, particularly in children. Chemical has been detected at SSFL.

Ionizing radiation Ionizing radiation consists of energy in the form of particles or electromagnetic rays emitted from a source. It is referred to as ionizing because this type of radiation has the ability, when it contacts matter, to cause ionization (the displacement of electrons from within atoms of the contacted matter). This material contains unstable atoms that, because of their instability, emit radiation. Unstable means the atom’s nucleus has more energy than it can hold (because it contains excess neutrons) and emits radiation from the nucleus until the excess energy is gone. Materials containing unstable atoms that emit radiation are referred to as radioactive, and the process that results in the emission of nuclear radiation is referred to as radioactive decay (sometimes radioactive disintegration). The four primary types of ionizing radiation that we are generally concerned with are alpha and beta particles, and Xray and gamma-ray radiation. (DTSC Removal Action Work Plan, PDF page 250)

Lead: Metal. Linked with learning disabilities, infertility, cancer, and increased risk of heart attacks. Metal has been detected at the SSFL.

Low-level radioactive waste (also known as low-rad): An intentionally deceptive label for any radioactive waste besides spent nuclear fuel. Low-level radioactive material includes anything from from the insides of nuclear reactors to protective shoe covers.

Mercury: Metal. It is a suspected carcinogen for brain and central nervous system (CNS) cancers. Metal has been detected at the SSFL.

Midden: An archeological term for an ancient waste site which may consist of animal bone, human excrement, botanical material, mollusc shells, potsherds, lithics, and other artifacts and ecofacts associated with past human occupation.

Millirem (mrem) is a term that scientists use to describe how much radiation the body absorbs. For example, scientists estimate that we receive a dose of 620 mrem every year from natural (e.g., radon) and human-made (e.g., medical) radiation sources.

Natural attenuation is a cleanup method used by the EPA that allows contamination to remain onsite with the assumption it will naturally attenuate (a process of decay, evaporation, biodegradation, sorption, or dilution). It is the least protective cleanup...because by definition, there is no cleanup, the contamination is left onsite and monitored.

N-nitrosodimethylamine: Chemical. Volatile N-nitrosamines induce tumors in a variety of human organs, including the tongue, esophagus, lung, pancreas, liver, kidney and bladder. Chemical has been detected at SSFL.

Naturally Occurring Radioactive Material (NORM) is defined by the EPA as, “Materials which may contain any of the primordial radionuclides or radioactive elements as they occur in nature, such as radium, uranium, thorium, potassium, and their radioactive decay products, such as radium and radon, that are undisturbed as a result of human activities."

Nickel-59:  Beta Emitter. Half-life of 75,000 years. Both nickel isotopes are present in wastes resulting from the reprocessing of spent nuclear fuel. The main health concern is associated with the increased likelihood of inducing cancer. Radionuclide has been detected at SSFL.

Nickel-63: Beta Emitter. Half-life of 96 years. Both nickel isotopes are present in wastes resulting from the reprocessing of spent nuclear fuel. Moderately toxic and may cause liver damage. The main health concern is associated with the increased likelihood of inducing cancer. Radionuclide has been detected at SSFL.

Non-ionizing radiation has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove electrons from atoms. Examples of this kind of radiation are radio waves, visible light and microwaves.

PCBs: Chemical. Hormone disruptors with effects on the immune, reproductive, nervous, and endocrine systems. Contaminant has been detected at SSFL.

Perchlorate: Chemical. Perchlorate accumulates in the thyroid gland and can block iodide transfer into the thyroid, resulting in iodine deficiency. Adequate iodide is crucial for neurological development. Chemical has been detected at SSFL.

Picocurie (pCi) is a term that scientists use to describe how much radiation and, therefore, how much tritium, is in the water. A pCi is a unit that can be measured by laboratory tests.

Plutonium-238/239/240: Alpha emitter. Low-energy x-ray emitter. Easily absorbed by tissue. Human exposure occurs mainly by breathing contaminated air or ingesting contaminated food or drink. When plutonium particles are inhaled and lodge in lung tissue, they continue to give off radiation internally. They can remain in the lungs or enter the gastrointestinal tract and the bloodstream. About 80 percent of the plutonium that enters the bloodstream goes either to the liver, bone or bone marrow, where it is retained for years, damaging tissue nearby. That damage may later develop into cancer. The half-life of plutonium-239 is about 24,000 years. Hazardous-life is 482,000 years. Radionuclide has been detected at SSFL.

Polycyclic Aromatic Hydrocarbons (PAHs): Chemical. Parents exposed to PAHS more likely to have children with leukemia. Contaminant has been detected at SSFL.

Parts Per Million (ppm): a measurement for contaminants. One part per million is approximately equal to one drop in 40 gallons. One milligram per cubic meter (mg/m3) is the same concentration in water as one microgram per liter (ug/L), which is about 1 ppb. *www.cfpub.epa.gov

Radiosensitive Cancers: Very radiosensitive cancers include thyroid, bone & joints, all leukemia, excluding chronic lymphocytic leukemia. Moderately radiosensitive include breast, lung & bronchus. Possibly radiosensitive cancers include esophagus, stomach, liver, brain & other nervous system, urinary bladder, other urinary system, salivary gland and parathyroid, and multiple myeloma.

Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. When it decays, a radionuclide transforms into a different atom - a decay product. The atoms keep transforming to new decay products until they reach a stable state and are no longer radioactive.

Radionuclides are elements that emit ionizing radiation.

RBSL: Risked based screening levels.

Recreational standard (aka risk based) assumes that the cleanup should only be protective enough to keep occasional visitors safe from the radioactive and chemical contamination. This could leave as much as 98% of the contamination on site permanently. This standard does not guarantee visitor protection, and it would continue to put local residents, some who live less than 0.25 miles away) at continued daily risk of exposure to radioactive and chemical contamination. 

Rem: A common unit used to measure radiation doses in the U.S. A dental X-ray is 0.0005 rem; a CT scan of the spine, 0.6 rem. According to the Environmental Protection Agency, people can start getting sick with a whole-body dose of 50 rem, death becomes “possible” at 400 rem, and nearly certain at 1,000 rem or more. In the United States, a power plant worker is limited to 5 rem per year, and the federal government tells local officials to advise residents to take shelter or leave if the residents’ dose is anticipated to reach 1 rem to 5 rem. In Europe and Asia, a unit called the sievert is more commonly used. One sievert equals 100 rem.

Rural residential cleanup standard (similar to the Agricultural standard) is a cleanup stringent enough that if a full time resident were to live on the site after the cleanup, and eat the produce grown there, that they would be safe from contamination health risks. This standard is similar to the background cleanup goals. This is also the zoning of local communities.

SRAM: Standardized Risk Assessment Method. This is the handbook for how Boeing will conduct their portion of the SSFL cleanup. The SRAM lists out all the contaminants of concern and lists the amount of remediation required for each, in order to meet their 2007 cleanup agreement. Currently the SRAM Version 2 is a scientific document that Parents vs SSFL supports. SRAM Version 3 is being pushed for by Boeing, it would leave the majority of the contamination on site.

Strontium-90: Beta Emitter. Strontium-90 can be inhaled, but ingestion in food and water is the greatest health concern. Once in the body, Sr-90 acts like calcium and is readily incorporated into bones and teeth, where it can cause cancers of the bone, bone marrow, and soft tissues around the bone. Radionuclide has been detected at SSFL. Half-life is 29 years, hazardous-life is 580 years.

Scatter: An archeological term for chipped rocks left from the creation of tools or weapons.

Trichloroethylene (TCE): Chemical. Strongly associated with kidney, liver, and biliary cancers, and is a suspected carcinogen for cervical cancer, Hodgkin and non-Hodgkin lymphomas, and leukemia. Chemical has been detected at SSFL.

Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM): is defined by the EPA as, "naturally occurring radioactive materials that have been concentrated or exposed to the accessible environment as a result of human activities such as manufacturing, mineral extraction, or water processing.” Many of the materials that are considered TENORM have only trace amounts of radioactivity and are part of our everyday landscape. However, some TENORM has relatively higher concentrations of radionuclides that can result in elevated exposures to radiation.

Thorium: Thorium is more abundant in nature than uranium. It is fertile rather than fissile, and can only be used as a fuel in conjunction with a fissile material such as recycled plutonium. Thorium-232 is naturally occurring. Thorium-238 is not found in nature. Thorium’s half-life is roughly 14 billion years.

Tritium: Beta Emitter. Cancer is the main risk from humans ingesting tritium. When tritium decays it spits out a low-energy electron (roughly 18,000 electron volts) that escapes and slams into DNA, a ribosome or some other biologically important molecule. And, unlike other radionuclides, tritium is usually part of water, so it ends up in all parts of the body and therefore can, in theory, promote any kind of cancer. But that also helps reduce the risk: any tritiated water is typically excreted in less than a month. Radionuclide has been detected at SSFL.

Uranium-235: Alpha Emitter. Ingestion of high concentrations of uranium can cause severe health effects, such as cancer of the bone or liver. Inhaling large concentrations of uranium can cause lung cancer from the exposure to alpha particles. Uranium is also a toxic chemical, meaning that ingestion of uranium can cause kidney damage from its chemical properties much sooner than its radioactive properties would cause cancers of the bone or liver. Radionuclide has been detected at SSFL.

Xrays: X-rays are electromagnetic radiation (similar to gamma rays) produced when high-speed electrons are slowed down rapidly upon striking a high-atomic-mass substance. They are produced in X-ray generating machines by directing a beam of electrons at a target material, and, as mentioned above, they can also be generated when beta particles (negatively charged particles like electrons) interact with high-atomic-mass materials. X-rays can be produced with a wide range of energies based on the energy of the electron beam and nature of the target material. As with gamma rays, the primary objective in dealing with X-rays is shielding to prevent external exposure. However, X-rays are not nuclear radiation (that is, emitted from the nucleus of a radioactive material), and as such there are no concerns with inhalation or ingestion. (DTSC Removal Action Work Plan, PDF page 251)

In progress:

Beryllium: Has been detected at the SSFL.

Chromium 51: Has been detected at the SSFL.

Phthalates: Chemical. Has been detected at SSFL.

REFERENCES

DEPARTMENT OF TOXIC SUBSTANCES CONTROL 1997-2007: Summary of Cancer Study and Exposure Assessment Activities related to the Santa Susana Field Laboratory (Rocketdyne) Site

ENVIRONMENTAL PROTECTION AGENCY, 2010: Final Radiological Characterization of Soils

ENVIRONMENTAL PROTECTION AGENCY, 2011: EPA Radiological Survey, EPA Radiological Background Study and accompanying statistical appendix found 291 soil samples with Cesium-137 contamination, at levels up to 1,000 times background, 153 samples had strontium-90, at levels up to 284 times background.

NEW YORK TIMES: Measuring Radioactive Elements and Their Effects on Human Cells

UCLA, 1999: Rocketdyne Chemical Study found that Rocketdyne workers who had high hydrazine exposures were about twice as likely as other Rocketdyne employees who worked at the site to die from lung and other cancers.

UCLA, 2006: Potential for Offsite Exposures Associated with Santa Susana Field Laboratory studied the potential exposure pathways investigated how contaminants might migrate from the Santa Susana Field laboratory to nearby communities. The study was headed by Dr. Yoram Cohen, Professor of Chemical Engineering and Director of the UCLA Center for Environmental Risk Reduction.

US DEPARTMENT OF LABOR: Office of Workers' Compensation Programs