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Glossary Acceptable daily intake (ADI): The daily dosage of a drug or a chemical residue that appears to present no appreciable risk to health during the entire lifetime of a human being. Age-adjusted cancer incidence or mortality: The incidence or mortality rate for cancer, adjusted for differences in the age distribution of the populations being compared, i.e., the study population and a standard reference population. Anticarcinogen: A substance that inhibits or eliminates the activity of a carcinogen. Antimutagen: A substance that inhibits or eliminates the activity of a mutagen. Antioxidant: A substance that retards oxidation. Examples include vitamin C, vitamin E, and butylated hydroxyanisole (BHA). Benign tumor: A tumor that is confined to the territory in which it arises, i.e., it does not invade surrounding tissue or metastasize to distant organs. These tumors can usually be excised by local surgery. Bioassay: A test in which living organisms are used. Cancer: Any of the various types of malignant neoplasms. See malignant tumor, neoplasm. Carcinogen: A chemical, physical, or biological agent that increases the incidence of cancer. Carcinoma: Cancer in an epithelial tissue, including external epithelia (mainly skin and linings of the gastrointestinal tract, lungs, and cervix) and internal epithelia (which line glands such as the breast, pancreas, and thyroid). Cocarcinogenesis: A general term that refers to augmentation of tumor induction. Cohort: 1. A group of people with a defined history of exposure who are studied for a specific length of time to determine cancer in- cidence or mortality. 2. A group of individuals born within the same time period (usually within 5 or sometimes 10 years of each 447 G-1
44X Glossary other). Such groups are called "birth cohorts." The diseases among individuals in one birth cohort followed throughout their lifetimes may be different from those in another, implying differences in exposures to factors causing disease. Complete carcinogen: An agent that can act as both initiator and promoter. Comutagen: A nonmutagenic substance that enhances the activity of a mutagen or imparts mutagenic activity to another nonmutagenic substance. Contaminant: A substance that is present in foods or feed but is not intentionally added. Delaney Clause: Legislation passed by the U.S. Congress in 1958 that forbids the addition to food any additives shown to be carcinogenic in any species of animal or in humans. Diet: The total composition of ingested food, including nutrients, naturally occurring contaminants, and additives. Dietary factors: Substances that are present in or characteristics that are associated with the diet; for example, the amount of total fat, dietary fiber, the ratio of saturated versus unsaturated fat, and the method of cooking. Environment: Anything external to humans, i.e., lifestyle factors and anything to which humans are exposed, including all forms of radia- tion and substances eaten, drunk, and inhaled. See lifestyle factors. Epidemiology: The study of the distribution of diseases and their determinants in human populations. Epigenetic: As used in reference to cancer, an effect that does not directly involve a change in the sequence of bases in DNA. Dietary fiber: Generic name for plant materials that are resistant to the action of normal digestive enzymes. Food additive: Any substance that is added to food, either directly or indirectly. Food disappearance data or per capita intake. Crude estimates of food or nutrients available for consumption by a specified population; based on food production, imports, exports, etc. They do not reflect the amount consumed since approximately 20% of the food is probably dis- carded, wasted, or spoiled. In the absence of data on actual food consumption, however, it may be the closest approximation of the per capita dietary intake of that population. G-2
Glossary 449 Genotoxicity: The quality of being damaging to genetic material. Hyperplasia: An increase in the number of cells in a tissue or organ. Incidence: The number of new cases of a disease expressed as a rate, i.e., the number of new cases of a disease occurring in a given population during a specific period, divided by the total number of persons at risk of developing the disease during that same period. Initiator: An external stimulus or agent that produces a cell that can become malignant under certain conditions. Initiation events may be mutational changes in a cell's genetic material, where the change is initially unexpressed and causes no detectable alteration in the cell's growth pattern. The change is considered to be irreversible. Latency or latent period: The interval between the first exposure to a carcinogenic stimulus and the appearance of a clinically diagnosable tumor. For a disease like cancer, which usually involves a sequence of steps over a long period, the term latent period may be ambiguous. Leukemia: Cancers of the blood-forming organs, characterized by abnormal proliferation and development of leukocytes (white- blood cells) and their precursors in the blood, lymph, bone marrow, and lymph glands. Lifestyle factors: Identifiable and quantifiable parameters of living (e.g., diet, smoking, drinking, hobbies) that are useful in distinguishing population groups for epidemiological studies. Lymphoma: A cancer of cells of the immune system (e.g., lymphocytes), where the tumor is confined to lymph glands and related tissues, such as the spleen. Malignant tumor: A tumor with the potential for invading neighboring tissue and/or metastasizing to distant body sites, or one that has already done so. Melanoma: Malignant melanoma is a cancer of the cells that produce the pigment melanin. Menarche: The age at which menstruation begins. Metaplasia: The abnormal transformation of an adult (mature), fully differentiated tissue of one kind into differentiated tissue of another kind. Metastasis: The spread of a malignancy to distant body sites by cancer cells transported in blood or lymph circulation.
450 Glossary Modifier: A substance that can alter the course of carcinogenesis. Morbidity: The condition of being diseased, or the incidence or prevalence of some particular disease. The morbidity rate is equivalent to the incidence rate. Mortality: The number of overall deaths, or deaths from a specific disease, usually expressed as a rate, i.e., the number of deaths from a disease in a given population during a specified period, divided by the average number of people exposed to the disease and at risk of dying from the disease during that time. Mutagen: A chemical or physical agent that interacts with DNA to cause a permanent, transmissible change in the genetic material of a cell. Multiple myeloma: A malignant neoplasm of plasma cells usually arising in the bone marrow. Also called myelomatosis. Neoplasm: A new growth of tissue with the potential for uncontrolled and progressive growth. A neoplasm may be benign or malignant. Nutrient: A component of food (e.g., protein, fat, carbohydrates, vitamins, minerals) that provides nourishment for growth and maintenance of the organism. Nutrition: The sum of the processes by which an organism utilizes the chemical components of food (which may or may not be synthesized in vivo) through metabolism to maintain the structural and biochemical integrity of its cells, thereby ensuring its viability and repro- ductive potential. Papilloma: A benign epithelial neoplasm. Per capita intake: See food disappearance data. Permissible residue: The quantity of a residue (e.g., a pesticide residue in or on a food crop) permitted when the product is first made available for consumption. The value may be calculated from the ADI (See acceptable daily intake). Precancerous lesion: A lesion or visible abnormality that has a significant probability of later developing into cancer. Prevalence (point prevalence): The number of existing cases of a dis- ease, usually expressed as a proportion, i.e., number of cases of a disease in a given population at a specified time, divided by the estimated number of eligible persons in the population at that same time. G-4
Glossary 451 Promoter: An agent that causes an initiated cell to produce a tumor after prolonged exposure. Promotion events or, more generally, late events can occur only in "initiated" cells and are somewhat reversi- ble. Discontinuation of exposure to a promoter before tumor develop- ment may prevent the appearance of a tumor. Pyrolysis: The decomposition of a substance by heat. Recommended Dietary Allowance (RDA): The level of intake of essential nutrients that is adequate to meet the nutritional needs of practically all healthy persons, as judged by the Committee on Dietary Allowances of the Food and Nutrition Board, National Research Council. Risk: As used in epidemiological sections of this report, risk refers to the probability of occurrence of a disease (cancer) in a given population. Relative risk: An estimate obtained by dividing the incidence of cancer in the exposed group by the incidence in the corresponding unexposed or control group. Sarcoma: Cancers of various supporting tissues of the body (e.g., bone cells, blood vessels, fibrous tissue cells, muscle). Synergism: When two or more substances enhance each other's effects, achieving more than the sum of their individual effects. Threshold dose: A non-zero dose below which exposure is safe and not associated with risk. Tolerance level: The maximum level or concentration of a drug or chemical that is permitted in or on food at a specified time during slaughter (or harvesting), processing, storage, and marketing up to the time of consumption by an animal or human being. Transformed cell: A cell that has undergone both initiation and promotion and has the potential for leading to the develoment of a neoplasm. Tumor: An uncontrolled and progressive growth of tissue. A neoplasm. It encompasses both benign and malignant neoplasms, but occasionally may refer merely to a swelling of tissue. Unintentional residue or contaminant: The residue of a compound in feed or food resulting from circumstances not intended to protect the feed or food against attack by infectious or parasitic diseases. The residue may be acquired during any phase in the growth, produc- tion, processing, or storage of feed or food. G-5