Cancer Incidence Rates in Eddy and Lea Counties

New Mexico, 1970-1994

Issued: April 6, 1998

LIST OF TERMS

Bias: Systematic errors in collecting, analyzing, or interpreting data.

Binomial Distribution: A frequency distribution of probability of an attribute that is dichotomous (binary). Binomial distributions approach normal distributions for large sample sizes.

Cancer: A group of diseases characterized by the rapid, uncontrolled growth of cells. When a cell becomes cancerous, it ceases to react normally to signals from the body and begins to rapidly multiply and destroy healthy tissue. If this growth is not stopped by treatment such as surgery, radiation therapy, or chemotherapy, the cancer can be fatal.

In Situ: A cancer growth that is confined to the epithelial layer at site of origin.

Invasive: A cancer growth that has spread to the epithelial membrane to invade the other tissues of the organ of origin.

Malignant: A cancer growth that may become invasive or metastatic, and may be fatal.

Metastatic: A cancer growth that has spread beyond the organ of origin by direct extension or through the lymphatic system or blood vessels.

Cancer Cluster: Cancers occurring in a group, where the group is defined by some characteristic that the people with cancer or the cancers themselves have in common (e.g. age, sex, residence, occupation or place of work, health behavior, date of diagnosis, and location of cancer).

Cancer Incidence Rate: The number of new cases of cancer occurring during a specified period of time, divided by the population of concern (the population in which the cancers occurred). Cancer incidence rates among adults are reported per 100,000 people per year in this report, and among children per 1,000,000 people per year.

Age-Adjusted: Cancer incidence rates calculated with a population that is weighted so that its age distribution is the same as the age distribution of a designated standard population, allowing for the comparison of incidence rates for multiple communities. Many cancers are age-related in that as people age they are more likely to develop cancer. Age-adjusting is used to ensure that age does not affect cancer incidence rates.

Age-Specific: Cancer incidence rates calculated directly, using the age distribution of the population of interest. This method is used to assess the incidence of cancer among people in defined age groups.

Baseline: Cancer incidence rates calculated before an event occurs that may affect these rates.

Moving Average: Moving average cancer incidence rates are derived by calculating the mean of incidence rates of a specified time period. The resulting rates are plotted on a graph at the middle year of the time period. Moving averages are used to minimize the sharp fluctuations characteristic of incidence rates for small populations.

Cancer Mortality Rate: The number of deaths from cancer occurring during a specified period of time, divided by the population of concern (the population in which the deaths from cancer occurred).

Carcinogen: An agent or substance that induces cancer.

Confidence Interval: A range of values that encompass the true value of a measure of effect or association. Ninety-five percent confidence intervals estimate the range of values for which there is a 95% certainty that they encompass the true rate. Confidence intervals are a function of both standard deviation and standard error.

Confounding: Effects of factors, beyond those studied, that are associated with, or responsible for, the results of a study.

Curie (Ci) (nanocurie): A measure of activity (i.e., the number of atoms of a radioactive material that disintegrate per second). Curies were originally used to describe the decay of radium. One curie equals 3.7 x 1010 disintegrations per second. One nanocurie equals 3.7 disintegrations per second.

By Ethnicity: Belonging to a particular cultural group that may share a social, as well as genetic, history. Ethnicities may be self-defined. The race category white includes the ethnicities Hispanic white and non-Hispanic white.

Hispanic White: Of Spanish, Mexican, Latino, Chicano, etc. origin excluding individuals who are of non-white racial groups.

Non-Hispanic White: Of Caucasian, Anglo, European, etc. origin; not of Spanish, Mexican, Latino, Chicano, etc. origin.

Half-Life: A measure of the speed of disintegration of a radioactive material. The half-life of a substance is the time in which half of its unstable nuclei have disintegrated, or decayed, and half still remain.

Normal Distribution: A frequency distribution of probability of an attribute for which highs and lows around an average value are equally common. Normal distributions follow symmetrical (bell-shaped) curves and are highest in the middle at the mean.

Nuclide: A general term applicable to all atomic forms of an element. Nuclides are characterized by their atomic number (number of protons), neutron number (number of neutrons), and energy state.

Poisson Distribution: A frequency distribution of probability used to describe rarely or randomly occurring events. The Poisson distribution is used to approximate the binomial distribution.

Radiation: Energy emitted from a source.

Electro-magnetic: Energy emitted as a result of the acceleration of electric charges and the interaction of associated electric and magnetic fields. Some researchers believe that exposure to electro-magnetic energy, such as that emitted by electric appliances and power lines, may increase the risk of developing certain cancers.

Ionizing: Energy that causes ionization (i.e., the displacement of electrons from atoms or molecules, thereby producing charged particles).

Radionuclide: A type of atom that loses particles and energy through the process of radioactivity, and decays or transforms into other elements.

Random Variation: The concept that an event occurred by chance, rather than by other factors.

Resource Conservation and Recovery Act (RCRA): The federal law which establishes a system for controlling solid and hazardous wastes from their generation to disposal.

Standard Deviation (of the mean): A quantification of the dispersion of values to either side of the middle of a normal curve.

Standard Error (of the mean): A measurement of the variability of the mean as an estimate of the mean's true value.

Stratify: To divide a sample into homogeneous categories. This is a technique used to eliminate the effect of confounding on study results associated with particular characteristics of the sample.

Waste:

Hazardous: A solid, liquid, or gaseous chemical material of negligible economic value that poses a potential hazard to human health or the environment when improperly managed. Hazardous wastes, as defined by the US Environmental Protection Agency, usually possess at least one of four characteristics: 1) ignitability, 2) corrosivity, 3) reactivity, and 4) toxicity.

Mixed: Waste contaminated by radioactive and chemically hazardous materials.

Radioactive: A solid, liquid, or gaseous material of negligible economic value that contains radionuclides in excess of threshold quantities defined by regulation.

Transuranic: Waste contaminated with radioactive nuclides that are heavier than uranium (i.e., above uranium on the periodic table) and have half-lives longer than 20 years. In addition, transuranic waste emits radiation at levels higher than 100 nanocuries per gram of waste.

WIPP: Acronym for the Waste Isolation Pilot Plant.