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Glossary of Terms

Defining Potentially Unfamiliar Words and Terms

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  1. Action level: The level of a contaminant which, if exceeded, triggers treatment or other requirements that a water system must follow. 
  2. Acute health effect: An effect occurring within hours or days that may result from exposure to certain contaminants, for example, 
      carbon monoxide poisoning.
  3. Acute myocardial infarction: More commonly known as a heart attack. A medical condition that occurs when the blood supply to a
      part of the heart is interrupted. The resulting blood or oxygen shortage causes damage and potential death of heart tissue.
  4. Admission date: The date of admission to the hospital.
  5. Adverse health effect: A change in body function or cell structure that may lead to a disease.
  6. Age adjusted: A measure that has been statistically modified to minimize the effect of different age distributions in the different
  7. Age-group: People grouped together based on age.
  8. Air pollution: The presence of substances in the air that are either present in an environment where they do not belong or present at
      levels greater than they should be.
  9. Air Pollution and Health: An Environmental Information System (APHEIS): A public health surveillance system in 26 European cities.
10. Air quality: A measure of what chemicals, particulate matter, or biological materials may be in the air.
11. Air Quality Index (AQI): An index for reporting daily air quality. It tells you how clean or polluted your air is and what associated health
      effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing
      polluted air. EPA calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution
      (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide.
12. Air Quality System (AQS): A database that contains ambient air pollution data collected by EPA, state, local, and tribal air pollution
      control agencies from thousands of monitoring stations.
13. Air toxics: Air pollutants known or suspected to cause cancer or other serious health effects, such as reproductive and birth defects,
      or adverse environmental effects.
14. Ambient Air: Air that is outside, not inside, of a building
15. Amyotrophic Lateral Sclerosis (ALS): ALS is a neurodegenerative disease that affects both upper and lower motor neurons. This
      disease is characterized by the progressive deterioration and loss of these motor neurons. The loss of nerve stimulus to specific
      muscles results in atrophy and progressive weakness that leads to paralysis.
16. Anencephaly: Anencephaly is a birth defect that affects the closing of the neural tube during pregnancy. The neural tube is a narrow
      channel that folds and closes during the third and fourth weeks of pregnancy to form the brain and spinal cord. Anencephaly occurs
      when the portion of the neural tube that forms the brain does not close. This results in the baby lacking parts of the brain, skull, and
      scalp. Read more about anencephaly.
17. Aquifer: A natural underground layer, often of sand or gravel, that contains water.   
18. Arsenic: A silver-gray or white metallic element of the periodic table of elements. It is a naturally occurring metal that is found in the
      Earth’s crust.
19. Asthma: A disease that affects the lungs, causing repeated episodes of wheezing, breathlessness, chest tightness, and nighttime or
      early-morning coughing.
20. Autism: The most common condition in a group of disorders known as autism spectrum disorders (ASDs). ASDs are developmental
      disabilities defined by significant impairments in social interaction and communication and the presence of unusual behaviors and
      interests. Many people with ASDs also have unusual ways of learning, paying attention, or reacting to different sensations. 
21. Autoimmune diseases: A group of more than 80 diseases in which the body’s immune system attacks its healthy cells. These
      diseases can affect many parts of the body.


  1. Benchmark: A standard by which other things can be measured. It sometimes means the best or most desirable value of the variable. 
  2. Biomonitoring: The direct measurement of people’s exposure to toxic substances in the environment by measuring the substances or
      their metabolites in human specimens, such as blood or urine. 
  3. Birth defect: A problem that happens as a baby develops in the mother’s body. A birth defect may affect how the body looks, works, or
      both. Some birth defects are so serious they can cause a baby to die; others are very minor problems that can be easily repaired. 
  4. Birth weight: The first weight of the newborn obtained after birth.
  5. Bladder cancer: Cancer that forms in tissues of the bladder, the organ that stores urine. 
  6. Blood lead level (BLLs): A measure of lead in the body. It is traditionally reported as the number of micrograms of lead per deciliter of
      blood (µg/dL) 
  7. Blood lead level test date: The date blood was taken for a blood lead level test. When this date is not available, it refers to the earliest
      date from the following: date blood sample was tested, date of blood lead result report, or date the blood sample was received by
  8. Blood lead test result: A quantifiable value or values below the method limit of detection from a blood lead test reported in micrograms
      per deciliter (µg/dL). 
  9. Breast cancer: A quantifiable value or values below the method limit of detection from a blood lead test reported in micrograms per
      deciliter (µg/dL). 
10. Bronchitis: An inflammation of the airways to the lungs. It causes a cough that produces a lot of mucus, shortness of breath, and
      chest tightness.


  1. Cancer: A disease in which cells in the body grow uncontrollably. It is often named for the part of the body where it starts, even if it
      spreads to other body parts later.
  2. Cancer Cluster: A greater-than-expected number of cancer cases that occurs within a group of people in a geographic area over a
      period of time. A person may expect that a cancer cluster exist when several loved ones, neighbors, or coworkers are diagnosed with
      cancer. However, what appears to be a cluster may actually reflect the expected number of cancer cases within the group or area.
      When considering the possible existence of a cancer cluster in your area, it is important to remember a few key facts: 1) cancer is a
      common disease, affecting about one in four people in their lifetime; 2) the term cancer refers not to a single disease, but instead to a
      group of related yet different diseases; 3) a cancer cluster may be due to chance alone, like the clustering of balls on a pool table; and
      4) an apparent cancer cluster is more likely to be genuine if the cases consist of one type of cancer, a rare type of cancer, or a type of
      cancer that is not usually found in an age group.
  3. Carbon monoxide (CO): An odorless, colorless gas that can cause sudden illness and death. CO is found in combustion fumes, such
      as those produced by cars and trucks, small gasoline engines, stoves, lanterns, burning charcoal and wood, and gas ranges and
      heating systems.
  4. Carbon monoxide detectors: A device that detects the presence of the toxic gas carbon monoxide (CO), a colorless and odorless
      compound produced by incomplete combustion and lethal at high levels.
  5. Carbon monoxide poisoning: Illness that results from exposure to carbon monoxide. The most common symptoms are headache,
      dizziness, weakness, nausea, vomiting, chest pain, and confusion. 
  6. Cardiovascular disease: A class of diseases that involves the heart or the blood vessels, including coronary heart disease,
      hypertension, stroke, and rheumatic heart disease. 
  7. Case-crossover analysis tool (C-CAT): A computer program used to estimate the short-term health effects of air pollution. 
  8. Cerebrovascular disease: Range of disorders in which an area of the brain is temporarily or permanently affected by a loss of blood
      supply involving one or more blood vessels.
  9. Chart: A type of information graphic that shows information in a tabular form. Charts are often used to aid comprehension of large
      quantities of data and the relationship between different parts of the data.
10. Chemical contaminants: Chemicals in the environment that cause harm or discomfort to humans or other living organisms or that
      damage the environment.
11. Child Match: The process of "de-duplicating" the Child Lead Poisoning Prevention Program (CLPPP) data file so that each child is
      counted only once. For example, one child could be accidentally entered twice, but more importantly for our purposes, a child could
      have more than one test. We want to count only one child and only one test for that child.
12. Childhood cancer: Defined two different ways: cancers occurring before age 15 or cancers occurring before age 20 
13. Childhood lead poisoning: Illness that results from exposure to lead. Lead poisoning can affect nearly every system in the body. It
      can cause learning disabilities, behavioral problems, and, at very high levels, seizures, coma, and even death.
14. Childhood leukemia: Cancer of the white blood cells that occurs during childhood. It is the most common type of childhood cancer 
15. Chronic health effect: A health condition that develops and persists over a long period of time.
16. Classification by exposure gradient: A health condition that develops and persists over a long period of time.
17. Clean Air Act: Under this law, EPA sets limits on how much of a pollutant can be in the air anywhere in the United States.
18. Cleft Lip with or without Cleft Palate: A cleft lip is an opening in the upper lip. The opening in the lip can be a small slit in the lip or a
      large opening that goes through the lip into the nose. A cleft palate is an opening in the roof of the mouth, called the palate. A cleft
      palate can occur when the two sides of the palate do not come together correctly. Read more about cleft lip and cleft palate.
19. Cleft Palate without Cleft Lip: A cleft palate is an opening in the roof of the mouth, called the palate. A cleft palate can occur when
      the two sides of the palate do not come together correctly. Read more about cleft palate 
20. Cluster: Cases of disease or health-related condition, which are closely grouped in time and/or place. This term usually refers to
      cancer and birth defects. (See related term: Cancer Cluster.)
21. Common Assessment level: The concentration selected by a hydrologist and applied to water-quality data that have variable
      laboratory reporting levels for a specific compound. The common assessment level is applied to data received from the laboratory and
      is applied subsequent to the laboratory reporting level. Concentrations reported by the laboratory below the common assessment level
      are considered as "non-detections" in the calculation of statistics. The highest laboratory reporting level for each constituent through
      time was used for the common assessment level (µg/L = micrograms per liter; mg/L = milligrams per liter; pCi/L, picocuries per liter).
22. Community Multiscale Air Quality Model (CMAQ): A model in which emission and meteorological data are run through computer
      code that simulates physical and chemical processes in the atmosphere to provide estimated concentrations of pollutants.
23. Community Water System (CWS): A public water system that serves year-round residents of a community, subdivision, or mobile
      home park that has at least 15 service connections or an average of at least 25 residents.
24. Concentration: Amount of a hazardous substance in a sample.
25. Confidentiality: private or secret
26. Contaminant: A substance that is either present in an environment where it does not belong or present at levels that might cause
      harmful health effects. 

27. Content Workgroup (CWG): A workgroup of the CDC National Environmental Public Health Tracking Program tasked to define  
      appropriate core data and measures to track.


  1. Data element: A specific piece of data, such as an observation or aggregate of individual observations, needed to calculate a value of
      a measure. 
  2. Data limitations: Specific information related to the quality or completeness of the data that will help you understand it correctly.
  3. Data source: An organization or information system providing data for tracking.  
  4. Data suppression: Preventing public display of information to protect personal information.
  5. Demolitions: A building or other structure intentionally destroyed or torn down.
  6. Developmental disability: A diverse group of severe chronic conditions caused by mental and/or physical impairments. People with
      developmental disabilities have problems with major life activities such as language, mobility, learning, self-help, and independent living.
  7. Discharge date: The date of discharge from hospital 
  8. Disease definitions: The set of symptoms or laboratory/clinical test results that lead to a diagnosis.
  9. Disinfectant: A chemical, commonly chlorine, chloramines, or ozone, or a physical process, such as ultraviolet light, that inactivates
10. Disinfection by-products: A family of chemicals that form when disinfectants, such as chlorine used in water treatment, react with
      bromide and/or naturally occurring organic matter in the water, for example, decomposing plant material.
11. Down Syndrome (Trisomy 21): Down syndrome is a condition in which a baby is born with an extra chromosome. Chromosomes are
      small "packages" of genes in the body. They determine how a baby’s body forms during pregnancy and how, as the baby grows in the
      womb and after birth, the baby’s body functions. Normally, a baby is born with 46 chromosomes. Babies born with Down syndrome
      have an extra copy of one of these chromosomes. This extra copy changes the body’s and brain’s normal development and causes
      developmental and physical problems for the baby. Read more about Down Syndrome.
12. Drinking water: Water that is intended for human consumption and other domestic uses.
13. Drinking water compliance: The act of meeting all state and federal drinking water regulations.
14. Drinking water contaminant: The act of meeting all state and federal drinking water regulations.
15. Drinking water exemption: State or EPA permission for a water system not to meet a certain drinking water standard. An exemption
      allows a system additional time to obtain financial assistance or make improvements in order to come into compliance with the
      standard. The system must prove that (1) there are compelling reasons (including economic factors) why Maximum Contaminant Level
      or Treatment Technique cannot be met; (2) the system was in operation on the effective date of the requirement, and (3) the
      exemption will not create an unreasonable risk to public health. The state must set a schedule under which the water system will
      comply with the standard for which it received an exemption 
16. Drinking water monitoring: Testing that water systems must perform to detect and measure contaminants. A water system that does
      not follow EPA's monitoring methodology or schedule is in violation and may be subject to legal action.
17. Drinking water supply: Water available for drinking 
18. Drinking water supply distribution system: A network of pipes used to carry treated water from the treatment plant to customers'
      plumbing systems 
19. Drinking water treatment technique: A required process intended to reduce the level of a contaminant in drinking water.
20. Drinking water variance: State or EPA permission not to meet a certain drinking water standard. The water system must prove that
      (1) even while using the best available treatment method it cannot meet a Maximum Contaminant Level because of the characteristics
      of the raw water and (2) the variance will not create an unreasonable risk to public health. The state or EPA must review and allow
      public comment on a variance every three years. States can also grant variances to water systems that serve small populations and
      which prove that they are unable to afford the required treatment or an alternative water source or to otherwise comply with the
21. Drinking water violation: A failure to meet any state or federal drinking water regulation.
22. Drinking water vulnerability assessment: An evaluation of drinking water source quality and its vulnerability to contamination by
      pathogens and toxic chemicals.
23. Dust: A cloud of finely powdered earth or other matter in the air.


  1. Ecologic linkage: In epidemiology, a relationship based on co-location in time and place. Analysis occurs at the group rather than
      individual level.
  2. EHIS: Environment and Health Information System of the World Health Organization/Regional Office for Europe
  3. Elevated blood lead level: A child with one venous blood specimen =10 mg/dL, or any combination of two capillary and/or unknown
      blood specimens =10 mg/dL drawn within 12 weeks of each other. 
  4. Emergency department: A hospital or primary care department that provides initial treatment to patients with a broad spectrum of
      illnesses and injuries, some of which may be life-threatening and requiring immediate attention 
  5. Entry point to the Distribution System (EPTDS): This is the point where the treated water enters the drinking water distribution
  6. Environmental data: Many different kinds of environmental data exist. Some provide concentrations of chemicals or other substances
      and in the land, water, or air that people might be exposed to; the data are used to evaluate exposures to these chemicals. Other data
      provide information about events or facilities that might cause possible environmental exposures but do not provide enough detail to
      evaluate exposures. These data are often used to make decisions or set priorities for future environmental health data gathering or
      regulatory activities. 
  7. Environmental hazard: A substance or situation in the environment that might adversely affect human health. People can be exposed
      to physical, chemical, or biological toxins from various environmental sources through air, water, soil, and food.
  8. Environmental health: The branch of public health that is concerned with understanding how the environment affects human health.
      The environment is the air we breathe, our water, our surroundings, and our food; it is the chemical, physical, and biological toxins that
      have contact with us everyday. Understanding how we interact with the environment is complicated, as is understanding how the
      environment may affect our health.
  9. Environmental justice: The fair treatment and meaningful involvement of all people regardless of race, national origin, color or income
      when developing, implementing and enforcing environmental laws, regulations and policies. Fair treatment means that no group of
      people, including a racial, ethnic, or socioeconomic group, should bear more than its share of negative environmental impacts. 
10. Environmental monitoring: The measurement of a material in the environment at regular time intervals. Monitoring for contaminants
      often involves collecting an environmental sample, such as stream water, preparation of the sample in the laboratory, and analysis of
      the prepared sample.
11. Environmental public health: Focuses on the relationships between people and their environment, promotes human health and well-
      being, and fosters a safe and healthful environment
12. Environmental public health indicator: Provides information about a population’s health status with respect to environmental
      factors. It can be used to assess health or a factor associated with health, such as a risk factor or an intervention, in a specified
      population through direct or indirect measures
13. Environmental public health tracking: Environmental public health tracking is the ongoing, systematic collection, integration,
      analysis, interpretation, and dissemination of data from environmental hazard monitoring, and from human exposure and health
      effects surveillance.
14. Environmental tobacco smoke: Secondhand smoke or tobacco smoke inhaled by someone who is close to a smoker.
15. EPA: United States Environmental Protection Agency 
16. EPA Health advisory (water): An EPA document that provides guidance and information on contaminants that can affect human
      health and that may occur in drinking water, but which EPA does not currently regulate in drinking water.
17. Epidemiology: The study of the distribution and determinants of health- related states or events in a population; the study of the
      occurrence and causes of health effects in humans.
18. Estimated exposure: An assessment or approximation of the contact of an individual or group with a particular substance.
19. Ethnicity: A term that represents a group based on their cultural and social affiliation, common history and origin, and sense of
      identification with the group.
20. Exposure: Contact with a substance by swallowing or breathing or by direct contact such as through the skin or eyes. Exposure may
      be short term, intermediate duration, or long term.
21. Exposure pathway: The route a substance takes from where it began, its source, to its end point and how people can come into
      contact with or get exposed to it.


  1. Family Educational Rights and Privacy Act (FERPA): A law that protects the privacy of student education records.
  2. Fecundity: The physical ability of a woman or couple to conceive and carry a child to term birth. For the purpose of this Web site,
      fecundity and fertility are often used interchangeably. 
  3. Fertility: The ability to conceive a child. For the purpose of this Web site, fecundity and fertility are often used interchangeably. 
  4. Finished Water: Water that has been treated and is ready to be delivered to customers.
  5. Fish advisory: A state-issued warning that cautions people about eating contaminated fish caught in local waters.


  1. Gastroschisis: A birth defect in which a portion of an infant’s intestines protrude out of the body through a small hole in the body wall
      beside the umbilical cord. The body wall defect can be small or large and other organs such as the liver can be involved. Read more
      about Gastroschisis  
  2. Geographic Information System (GIS): A system for capturing, storing, analyzing, and managing geographic data. 
  3. Gestational age: A baby's age in number of weeks since conception.
  4. Graph: A visual representation of data that displays the relationship among variables. Graphs are especially useful for showing broad
      trends in the data.  
  5. Ground water: The supply of fresh water found beneath the Earth's surface, usually in aquifers, which is often used for supplying
      wells and springs.
  6. Ground water contamination: Any physical chemical, biological, or radiological substance or matter in ground water.


  1. Haloacetic acid-5 (HAA5): The sum of five regulated haloacetic acids (monochloro-, dichloro-, trichloro-, monobromo-, dibromo-).
      These are another widely occurring classes of disinfection byproducts formed during disinfection with chlorine and chloramine.
  2. Haloacetic acid-9 (HAA9): HAA5 (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid,
      dibromoacetic acid) plus bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, and tribromoacetic acid.
  3. Hazard: A factor or exposure that may adversely affect health. 
  4. Hazardous waste sites: A location where harmful substances have been released or discarded into the environment.
  5. Health data: Data that provide information about the occurrence of certain diseases and health conditions. 
  6. Health effect or health outcome: The disease or health problem itself, such as asthma attacks or birth defects.
  7. Health Insurance Portability and Accountability Act (HIPAA): A law requiring protection of personal health information.
  8. Healthy homes: Homes that are free from housing-related hazards and deficiencies that cause diseases and injuries.
  9. Heart attack: Also known as acute myocardial infarction. A medical condition that occurs when the blood supply to a part of the heart
      is interrupted. The resulting blood or oxygen shortage causes damage and potential death of heart tissue.
10. Heart disease: A broad term that includes several more specific heart conditions. The most common heart condition in the United
      States is coronary heart disease, which can lead to heart attack and other serious conditions.
11. Heavy metals: There are several definitions for "heavy metals". For Tracking, a heavy metal is defined as metallic chemical elements that has a relatively
      high density and is toxic at low concentrations. Heavy metals are natural components of the earths crust. Exposure to heavy metals may in through diet, the
      environment, medications, or specific occupations. As trace elements, some heavy metals (e.g. iron, copper, zinc) are essential to the human body. However,
      even these can cause harm at higher levels.
12. Herbicide: Chemicals used to control undesirable weeds and plants in agricultural, residential, and water environments.
13. Hospital transfers: A patient discharged from one facility and readmitted to a second facility on the same day.
14. Hospitalization/hospital admission: Condition of being placed or treated as a patient in a hospitalas an inpatient. Treatment as an out-patient is not
      considered hospitalization. For the hospitalization to beconsidered inpatient, the patient must stay in the hospital at least one night or more. 
15. Housing age: Measured by period in time when a house was built.
16. Hypoplastic Left Heart Syndrome: A heart condition that is present at birth, and often is called a congenital heart defect. It is a group of related defects that,
      together, mean that the left side of the heart is underdeveloped. Read more about Hypoplastic Left Heart Syndrome
17. Hypospadias: A birth defect among boys in which the opening of the urethra is located somewhere along the underside of the penis instead of at the tip. The
      urethra is the tube that carries urine from the bladder to the outside of the body. This defect occurs when the urethra does not complete its development
      during the pregnancy. Read more about Hypospadia


  1. ID: Identification
  2. Identifiying information: Information that might reveal who someone is.
  3. Incidence: Number of new cases of illness occurring within a specific population over a period of time.
  4. Indicator: For Tracking, an indicator is one or more items,characteristics orother things that will be assessed and that provideinformation about a population»s
      health status, their environment, andother factors with the goal of allowing us to monitor trends, compare situations, and better understand the link between
      environment and health. It is assessed through direct and indirect measures (e.g. levels of a pollutant in the environment as a measure of possible exposure)
      that describe health or a factor associated with health (i.e., environmental hazard, age) in a specified population.Indicators are available within each Content
  5. Infant mortality rate: The number of deaths of infants, one year of age or younger, per 1,000 live births. 
  6. Infant mortality<: Death of an infant in the first year of life.
  7. Infertility: A condition occurring when a couple cannot get pregnant after one year of trying.
  8. Inorganic contaminants: Mineral-based compounds such as metals, nitrates, and asbestos. These contaminants are naturally-occurring in some water, but
      can also get into water through farming, chemical manufacturing, and other human activities. EPA has set legal limits on 15 inorganic contaminants in drinking
  9. Integrated pest management: A common sense, systems-based approach to managing pests that focuses on pest prevention; reduction; and elimination of
      the conditions that lead to pest infestation. Although it includes some standard pest control techniques, integrated pest management includes four specific
      components: inspection; monitoring; treatment; and evaluation.
10. International Classification of Diseases (ICD): A system produced by an internationally representative group that classifies diseases by giving each a
      unique code. 


  1. Land use: The human modification of natural environment or wilderness into built environment such as fields, pastures, and settlements.
  2. Lead: A naturally occurring bluish-gray metal found in small amounts in the earth's crust. Lead can be found in all parts of our environment. Much of it comes
      from human activities including burning fossil fuels, mining, and manufacturing.
  3. Leukemia: Cancer of the white blood cells.
  4. Low birth weight: A baby is considered to be of low birth weight when its weight is less than 5.5 lbs, or 2500 grams, at birth. For Tracking, low birth weight is
      measured among singleton births only.
  5. Lower Limb Reduction Defects: Lower limb reduction defects occur when a part of or the entire leg (lower limb) of a fetus fails to form completely during
      pregnancy. The defect is referred to as a "limb reduction" because a limb is reduced from its normal size or is missing. Read more about Lower Limb
      Reduction Defects
  6. Lung cancer: Cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small
      cell lung cancer, diagnosed based on how the cells look under a microscope.
  7. Lung disease: A broad term that refers to many disorders affecting the lungs. Lung disease includes diseases such as asthma, emphysema, and chronic
  8. Lymphoma: Cancer that starts in a part of the immune system called the lymphatic system, which is made up of lymph or lymphatic tissue.


   1. Maximum Contaminant Level (MCL): The highest level of a contaminant that EPA allows in drinking water. MCLs ensure that drinking water does not pose
       either a short-term or long-term health risk. EPA sets MCLs at levels that are economically and technologically feasible. Some states set MCLs which are 
       more strict than EPA’s.
   2. Maximum Contaminant Level Violation: Failure to keep a contaminant level in drinking water below its Maximum Contaminant Level.
   3. Mean: The average of a list of numbers by calculating the sum of all the members of the list and dividing by the number of items in the list.
   4. Measure: On the Tracking Network,a measure is asummary characteristic or statistic, such as a sum, percentage, or rate. Measures are available for each
   5. Measure of precision: Degree of certainty for a particular statistic.
   6. Memorandum of Understanding (MOU): A legal document that defines a relationship or agreement between departments, agencies or closely held
   7. Mercury: Mercury is a naturally occurring metal found throughout the environment. It exists in three forms: metallic or elemental mercury; inorganic mercury;
      and organic mercury. In its metallic form, it is the familiar shiny, silver-white odorless liquid used in thermometers. At room temperature, it can evaporate to
      form mercury vapor. When mercury combines with other elements such as chlorine, sulfur, and oxygen, it forms inorganic mercury or mercury salts. Organic
      mercury is formed when mercury combines with carbon. The most common organic mercury compound is methylmercury. Mercury enters the environment
      from the breakdown of rocks and soil, from volcanic activity, and from human activity such as mining and burning coal.
  8. Metadata: Metadata are "data about data". Metadata describe the content, quality, and context of a dataset and provide links to additional information such as
      quality assurance documents and data dictionaries. The Tracking Network contains metadata records for datasets used to create the Tracking Indicators and
      for datasets maintained by national, state, and local environmental health partners.
  9. Metropolitan Statistical Area (MSA): A contiguous area containing counties of relatively high population density, defined by the US Census Bureau.
10. Microorganisms: Tiny living organisms that can be seen only with the aid of a microscope. Some microorganisms can cause acute health problems when
      consumed in drinking water. Also known as microbes.
11. Morbidity: State of being ill or diseased. Morbidity is the occurrence of a disease or condition that alters health and quality of life.
12. Mortality: Death.
13. Multiple Sclerosis: A chronic, often disabling disease, that attacks the nervous system affecting the brain and spinal cord. It slows down or stops messages
      between the brain and the body leading to vision, muscular, coordination and balance, thinking, and memory problems.


  1. National Ambient Air Quality Standards (NAAQS): Under the Clean Air Act, the EPA established limits for six air pollutants to protect public health and the
      environment. Those air pollutants are carbon monoxide, lead, nitrogen dioxide, particulate matter of 10 microns or less (PM10), particulate matter of 2.5
      microns of less (PM2.5), ozone, and sulfur dioxide.
  2. National Environmental Public Health Tracking Network: A Web-based, secure network of standardized electronic health and environmental data. 
  3. National Environmental Public Health Tracking Program: The Congressionally mandated national effort that will establish a network to enable the ongoing
      collection, integration, analysis, and interpretation of data about the following factors: (1) environmental hazards, (2) exposure to environmental hazards, and
      (3) health effects potentially related to exposure to environmental hazards.  
  4. Neonatal mortality: An infant death which occurs in the first 27 days of life. 
  5. Neurodegenerative disease: A disorder caused by deterioration of the nerve cells. 
  6. Nitrate: A water-soluble molecule made of nitrogen and oxygen.  
  7. Non-hodgkin's lymphoma: Any of a large group of cancers of the immune system. Non- Hodgkin's lymphoma begins when a type of white blood cells, either
      T- or B-cells, become abnormal. The cells then divide again and again, producing more abnormal cells. These cancers are often marked by enlarged lymph
  8. Non-Transient, Non-Community Water System (NTNC): A water system which supplies water to 25 or more of the same people at least six months per  
      year in places other than their residences. Some examples are schools, factories, office buildings, and hospitals which have their own water systems.


  1. Organic water contaminants: Carbon-based chemicals, such as solvents and pesticides, which can get into water through runoff from cropland or discharge
      from factories.  
  2. Overlay: Placing a layer of information on top of another layer to see how they are related.  
  3. Ozone: A pollutant that occurs in two layers of the atmosphere. In the stratosphere, ozone protects the earth from harmful ultraviolet rays. At ground-level,
      ozone is an air pollutant that can be harmful to human health and the environment. It is the principal component of "smog" and is produced from the action of
      sunlight on air contaminants from combustion sources including automobile exhausts. Ozone levels are most likely to be elevated on hot, sunny afternoons


  1. Particle pollution: A complex mixture of extremely small particles and liquid droplets. Particle pollution is made up of a number of components, including 
      acids, such as nitrates and sulfates, organic chemicals, metals, and soil or dust particles.  
  2. Particulate matter (PM2.5): Fine particles or droplets in the air that are less than 2.5 microns wide, or about 30 times smaller than human hair. Outside, they
      come primarily from motor vehicle exhausts, power plants, wild fires, manufacturing processes, and the reaction of gases in the atmosphere. Indoor sources
      include tobacco smoke, cooking, fireplaces, and candles.  
  3. Pathogen: A disease-causing organism.
  4. Perchloroethene (PCE): This is a volatile organic compound (VOC) also known as Tetrachloroethylene and Tetrachloroethene. It is a manufactured chemical
      used for dry cleaning and metal degreasing.
  5. Perinatal mortality: A fetal death of 28 weeks gestation or more and an infant death in the first 6 days of life.  
  6. Pesticide poisoning: Damage or illness that results from inhaling, absorbing, touching, or swallowing a pesticide.
  7. Pesticides: Any substance or mixture of substances intended for preventing, destroying, repelling, or controlling any pest: herbicides, fungicides, insecticides,
      and various other substances. 
  8. Polychlorinated Biphenyl (PCBs): Chemicals made up of as many as 209 chlorinated compounds that do not occur naturally. They can either be oily liquids
      or waxy solids that are odorless and range from colorless to yellow in color. These chemicals were used in hundreds of industrial and commercial applications
      including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; in pigments, dyes, and carbonless copy
      paper; and many other industrial applications. PCBs are toxic and have been banned for use in the U.S. since 1979.  
  9. Postneonatal mortality: A death which occurs between 28 days and a year of life. 
10. Poverty percent or rate: The percentage of people or families who are below poverty (12%–15% below federal poverty line).  
11. Preterm birth: Preterm birth is the birth of an infant at least three weeks before the due date (less than 37 weeks gestation). For Tracking, preterm births are
      measured among singleton births only. 
12. Prevalence: The number of existing cases of an illness in a defined population at a given point in period or time.  
13. Prevention: Proactive activities conducted to avoid health hazards and their consequences. 
14. Primacy State: A state that has the responsibility and authority to administer EPA’s drinking water regulations within its borders. The state must have rules
      at least as stringent as EPA’s.  
15. Primary diagnosis code: The first diagnosis field(s) of the coded clinical record. Presently, the code is represented by an ICD-10-CM code (the
      International Classification of Diseases, 10th Revision, Clinical Modification). 
16. Privacy: Health information privacy broadly refers to individuals’ rights to control the acquisition, use, or disclosure of their identifiable health data. 
17. Public health surveillance: The ongoing, systematic collection, analysis, and interpretation of health data. This activity also involves timely dissemination of
      the data and use for public health programs. 
18. Public notification: An advisory that EPA requires a water system to distribute to affected consumers when the system has violated MCLs or other
      regulations. The notice advises consumers what precautions, if any, they should take to protect their health. 
19. Public Water System (PWS): Any water system that provides water to at least 25 people for at least 60 days annually.


  1. Race: The classification of humans into populations or groups on the basis of various sets of characteristics. The most commonly used categories are based
      on visible traits, such as skin color, facial features, hair texture, and self-identification. 
  2. Radionuclides: Any man-made or natural element that emits radiation and that may cause health problems, including cancer and birth defects, after many
      years of exposure through media such as drinking water and air. 
  3. Radon: A natural radioactive gas that you can not see, smell, or taste, but is extremely toxic.  
  4. Rapid Inquiry Facility (RIF): An automated mapping and analysis tool that provides an extension to ESRI® ArcGIS functions and uses both database and
      GIS technologies. The purpose of this facility is to rapidly address epidemiological and public health questions using routinely collected health and population
  5. Rate: A measure of the frequency with which an event occurs in a defined population. 
  6. Raw water: Water in its natural state, prior to any treatment for drinking. See related term: Source water. 
  7. Registry: Information system for documenting people with a common characteristic, such as a particular health condition. 
  8. Remote sensing data: Data from sensing devices, such as satellites, aircrafts, and spacecraft.  
  9. Reproductive health: Health of the male and female reproductive and sexual organs. The term is also applied to issues relating to the reproductive process,
      such as fertility, and pregnancy outcomes like infant mortality and preterm delivery. 
10. Research: A systematic investigation, including the design, implementation, testing and evaluation to contribute to the scientific literature. 
11. Resolution: Degree of detail that can be seen or shown. 
12. Respiratory health: Relating to the health of the lungs and the other parts of the of the respiratory system that affect our breathing. 
13. Risk: Potential or probability that an event will occur, such as danger or harm. 
14. Risk factor: An aspect of personal behavior or lifestyle, an environmental exposure, or a genetic characteristic that affects a person’s chance of getting a
      disease or other adverse health effect.


  1. Safe Drinking Water Act: Originally passed by Congress in 1974 to protect public health by regulating the nation's public drinking water system, SDWA
      authorizes the EPA to set national, health-based standards for drinking water to protect against both naturally-occurring and man-made contaminants that may
      be found in drinking water. EPA, states, and water systems then work together to make sure that these standards are met.
  2. Safe Drinking Water Information System/Federal: Contains information about public water systems and their violations of EPA's drinking water regulations,
      as reported to EPA by states. It does not contain specific sampling or monitoring data. 
  3. Safe Drinking Water Information System/State: A system that helps states manage the information necessary to supervise public drinking water systems.
      It houses three major categories of information: inventory, sampling, and monitoring data. 
  4. Sanitary survey: An on-site review of the water sources, facilities, equipment, operation, and maintenance of a public water systems for the purpose of
      evaluating the adequacy of the facilities for producing and distributing safe drinking water.  
  5. Secondary Drinking Water Standards: Non-enforceable federal guidelines regarding cosmetic effects, such as tooth or skin discoloration, or aesthetic
      effects, such as taste, odor, or color, of drinking water. These standards are recommended to water systems, but the systems are not required to comply.
  6. Sex ratio: For Tracking this is the ratio of males to females at birth among term single births.  
  7. Smoke: Smoke is created when air combines with the airborne solid and liquid particulates and gases that are emitted when a material undergoes
  8. Smoothing: The process of averaging a measure for an area based on information about that area and areas around it.  
  9. Soil: The top layer of the earth’s surface, consisting of rock and mineral particles mixed with organic matter. 
10. Sole Source Aquifer: An aquifer that supplies 50 percent or more of the drinking water of an area. 
11. Source Water: Water in its natural state, prior to any treatment for drinking.
12. Spatial correlation: The measure of the tendency for places that are near each other to have similar or dissimiliar characteristics. 
13. Spatial relationship: The measure of the distance between two locations. 
14. Spina Bifida (without Anencephaly): The most common birth defect in the United States. It is a type of neural tube defect. The neural tube is a narrow
      channel that folds and closes during the third and fourth weeks of pregnancy to form the brain and spinal cord. Spina bifida happens if the portion of the 
      neural tube that forms the spinal cord does not close completely during the first month of pregnancy.
15. State Environmental Health Indicators Collaborative (SEHIC): A group of state-level environmental health practitioners within the Council of State and
      Territorial Epidemiologists, CSTE, developing indicators for use within environmental health surveillance and practice.
16. Surface water: Water on the surface of the earth, such as in lakes, rivers, streams, ponds, and springs.  
17. Systemic Lupus Erythmatosis (SLE): An autoimmune disease with a number of possible symptoms including rash, sensitivity to light, ulcers in the mouth,
      arthritis, pleuritis, pericarditis, kidney problems, seizures and psychosis, blood cell abnormalities.


  1. Temporal scale: Time period used for statistics. 
  2. Tetrachloroethylene or Tetrachloroethene: This is a volatile organic compound (VOC) also known as Perchloroethene (PCE). It is a manufactured chemical
      used for dry cleaning and metal degreasing.
  3. Tetralogy of Fallot: A heart condition that is present at birth, and often is called a congenital heart defect. This defect changes the normal flow of blood
      through the heart. Tetralogy of Fallot is a combination of four defects: (1) a hole in the wall between the ventricles (two lower chambers of the heart), called a
      ventricular septal defect; (2) narrowing of the tube that carries blood from the heart to the lungs, called pulmonary stenosis; (3) the aorta (the tube that carries
      oxygen-rich blood to the body) grows from both ventricles, rather than from the left ventricle only; and (4) a thickened muscular wall of the right ventricle,
      called right ventricular hypertrophy. Read more about Tetralogy of Fallot  
  4. Thyroid cancer: Cancer that forms in the thyroid gland, a butterfly-shaped organ at the base of the throat that makes hormones that help control heart rate,
       blood pressure, body temperature, and weight. Four main types of thyroid cancer are papillary, follicular, medullary, and anaplastic thyroid cancer. 
  5. Time trend: Monitoring change over time 
  6. Total Fertility rate: The number of births per 1,000 women of reproductive age.
  7. Total trihalomethanes (TTHM): TTHM is a sum of the concentration in milligrams per liter of the following disinfection byproducts: chloroform, bromoform,
      bromodichloromethane, and dibromochloromethane. 
  8. Toxin: A substance that is harmful to the body or environment. 
  9. Traffic: The movement of vehicles, ships, persons, etc., in an area, along a street, through an air lane, over a water route. 
10. Transient, Non-Community Water System (TNC): A water system which provides water in a place such as a gas station or campground where people do
       not remain for long periods of time. These systems do not have to test or treat their water for contaminants which pose long-term health risks because fewer
       than 25 people drink the water over a long period. They still must test their water for microbes and several chemicals.
11. Transposition of the Great Arteries (Vessels): A heart condition that is present at birth, and often is called a congenital heart defect.
      Transposition of the great arteries occurs when the two main arteries going out of the heart—the pulmonary artery and the aorta—are
      switched in position, or "transposed". Read more about Transposition of the Great Arteries 
12. Trichloroethylene or Trichloroethene (TCE): This is a volatile organic compound (VOC). It is a colorless liquid which is used as a
      solvent for cleaning metal parts. 
13. Turbidity: The cloudy appearance of water caused by the presence of tiny particles. High levels of turbidity may interfere with proper
      water treatment and monitoring


  1. Underground storage tanks (USTs): Containers for the storage of petroleum or hazardous substances that can harm the environment
      and human health if the USTs release their stored contents 
  2. United States Geological Survey (USGS): A government science organization that focuses on biology, geography, geology,
      geospatial information, and water. The organization is dedicated to the timely, relevant, and impartial study of the landscape, natural 
      resources, and natural hazards.
  3. Upper Limb Reduction Defects: Upper limb reduction defects occur when a part of or the entire arm (upper limb) of a fetus fails to
      form completely during pregnancy. The defect is referred to as a "limb reduction" because a limb is reduced from its normal size or is
      missing. Read more about Upper Limb Reduction Defects
  4. US National Oceanic and Atmospheric Administration (NOAA): A scientific agency focused on the conditions of the oceans and the


  1. Vital statistics: Data derived from certificates and reports of birth, death, fetal death, induced termination of pregnancy, marriage, and
      related reports
  2. Volatile organic compounds (VOCs): Organic compounds that easily become vapors or gases. Some are released from burning fuel,
      such as gasoline and coal. When released into the environment, these chemicals can cause damage to the soil and ground water and
      can contribute to air pollution.


  1. Water Distribution System: A network of pipes leading from a treatment plant to customers’ plumbing system
  2. Water sample: The water that is analyzed for the presence of EPA-regulated drinking water contaminants. Depending on the
      regulation, EPA requires water systems and states to take samples from source water, from water leaving the treatment facility, or from
      the taps of selected consumers 
  3. Water well: A hole drilled or bored into the earth to get water.
  4. Watershed: The land area from which water drains into a stream, river, or reservoir. 
  5. Wellhead Protection Area: The area surrounding a drinking water well or well field which is protected to prevent contamination of the