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Acid rain:

Precipitation (rain, snow, sleet, or hail) that contains high levels of dilute sulfuric or nitric acids. Acid rain is produced when water combines with sulfur dioxide and various nitrogen oxides in the atmosphere. The burning of fossil fuels (especially gasoline and high-sulfur industrial fuels) is thought to be the main cause, but some natural sources (volcanic gases and forest fires) may also contribute to acid rain. Acid rain can contaminate drinking water, endanger wildlife and vegetation, and damage buildings and monuments.



A water-soluble and sour chemical compound that produces positive ions in solution. An acid is the opposite of a base; together, an acid and a base neutralize each other and react to form water and a salt. Common vinegar, for example, is a weak acid.



Occurring over a short period of time, usually a few minutes or hours. An acute exposure can result in short-term or long-term health effects.


Adverse health effect:
A change in body function or cell structure that might lead to disease or health problems.


Agency for Toxic Substances and Disease Registry (ATSDR):

An agency of the U.S. Department of Health and Human Services. ATSDR's mission is to prevent exposure and adverse human health effects and diminished quality of life associated with exposure to hazardous substances from waste sites, unplanned releases, and other sources of pollution in the environment. The agency's functions include public health assessments of waste sites, health consultations concerning specific hazardous substances, health surveillance and registries, response to emergency releases of hazardous substances, applied research in support of public health assessments, information development and dissemination, and education and training concerning hazardous substances.


Air pollution:

Unhealthy particles and gases in the air that harm people, animals, plants, and even objects such as buildings and statues. Air pollution can be present as a solid, liquid, or gas. Acid rain is an example of gases and liquids mixing with otherwise clean air.


Air Quality Index (AQI):

The AQI is EPA’s index for reporting daily air quality.  It indicates how clean or polluted your air is, and what associated health effects might be a concern.  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. For each of these pollutants, EPA has established national air quality standards (NAAQS) to protect public health.


Air Quality System (AQS):

The Environmental Protection Agency’s Air Quality System (AQS) database contains measurements of air pollutant concentrations in the 50 United States, plus the District of Columbia, Puerto Rico, and the Virgin Islands. The measurements include both criteria air pollutants and hazardous air pollutants. 


Air toxic (Also Hazardous air pollutant or Toxic air pollutant):

Any air pollutant that is likely to cause serious or irreversible long-term health effects in humans. Air toxics may cause cancer, developmental effects, reproductive problems, neurological disorders, and genetic mutations. They include pollutants for which a national ambient air quality standard does not exist.


Ambient air:

Open air or outdoor air. Ambient air is a blanket of gases surrounding the earth. At ground level, air is a mixture of invisible and odorless gases, mostly nitrogen and oxygen, with smaller amounts of water vapor, argon, carbon dioxide, neon, helium, and hydrogen.



A substance measured in the laboratory. A chemical for which a sample (such as water, air, or blood) is tested in a laboratory. For example, if the analyte is mercury, the laboratory test will determine the amount of mercury in the sample.


Area source:

Also Nonpoint source. Any small source of human-generated air pollution that is released over a relatively small area but that cannot be classified as a point source. Area sources may include vehicles and other small engines, small manufacturing companies, dry cleaners, gas stations, and household activities such as wood burning. Individual area sources may not release much pollution, but the cumulative effect of many area sources may be significant.



A naturally occurring element widely distributed in the earth's crust. In the environment, arsenic is combined with oxygen, chlorine, and sulfur to form inorganic arsenic compounds. Arsenic in animals and plants combines with carbon and hydrogen to form organic arsenic compounds. Inorganic arsenic compounds are mainly used to preserve wood. Organic arsenic compounds are used as pesticides, primarily on cotton plants. 



A mineral fiber that can pollute air or water and cause cancer or asbestosis when inhaled. EPA has banned or severely restricted its use in manufacturing and construction. 



A serious, chronic lung disease that causes the airways (bronchial tubes) to become narrow and makes it hard to breathe. Asthma attacks are often caused by environmental triggers, such as molds, dust mites, and tobacco smoke.


Autism/Autism spectrum disorders (ASDs):

A group of developmental disabilities that are caused by unusual brain development. People with ASDs tend to have problems with social and communication skills. Many people with ASDs also have unusual ways of learning, paying attention, or reacting to different sensations. ASDs begin during childhood and last throughout a person's life.



Background level:
An average or expected amount of a substance or radioactive material in a specific environment, or typical amounts of substances that occur naturally in an environment.
A birth defect is a problem that happens while the baby is developing in the mother’s body.  Most birth defects happen during the first 3 months of pregnancy. A birth defect may affect how the body looks, works, or both.  It can be found before birth, at birth, or anytime after birth.  Most defects are found within the first year of life.  Some birth defects (such as cleft lip or clubfoot) are easy to see, but others (such as heart defects or hearing loss) are found using special tests (such as x-rays, CAT scans, or hearing tests).  Birth defects can vary from mild to severe.  
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. Biomonitoring measurements are the most health-relevant assessments of exposure because they indicate the amount of the chemical that actually gets into people (from all environmental sources (e.g., air, soil, water, dust, food) combined, rather than the amount that may get into them. 
CDC random digit dial telephone survey performed on a state-by-state basis.  The BRFSS is designed to question randomly-selected, non-institutionalized people ages 18 and older about health and behavioral issues.  Topics include: Demographics; General health measures (health status, health insurance, quality of life and care giving, height, weight); Health conditions (such as diabetes, high blood pressure, high cholesterol, oral health, asthma, cardiovascular disease, arthritis); Risk behaviors such as smoking, alcohol use, physical inactivity, diet, excess weight ; Health services utilization(breast , cervical, prostate, or colorectal cancer screenings and influenza or pneumoccocal vaccinations.) 


Abandoned, idle, or underused industrial or commercial sites that raise concern in nearby communities that any expansion or redevelopment could contaminate the environment. 





A natural element in the earth's crust. It is usually found as a mineral combined with other elements such as oxygen (cadmium oxide), chlorine (cadmium chloride), or sulfur (cadmium sulfate, cadmium sulfide). All soils and rocks, including coal and mineral fertilizers, contain some cadmium. Most cadmium used in the United States is extracted during the production of other metals like zinc, lead, and copper. Cadmium does not corrode easily and has many uses, including batteries, pigments, metal coatings, and plastics. 



Any one of a group of diseases that occur when cells in the body become abnormal and grow or multiply out of control. 


Cancer cluster:

Defined as a greater-than-expected number of cancer cases that occurs within a group of people in a geographic area over a period of time. 


Carbon monoxide (CO):

A criteria air pollutant.  Carbon monoxide is a colorless, poisonous gas formed by burning, especially fuels such as gasoline, oil, and wood. Breathing too much carbon monoxide interferes with the body's absorption of oxygen and therefore is espectially dangerous for people with respiratory and heart disease. 



Any substance that causes or aggravates cancer.


CT Electronic Disease Surveillance System (CEDSS):

A CT web-based disease surveillance application that implements a National Electronic Disease Surveillance System (NEDSS)-based logical data model to support the CT Department of Public Health (CT DPH) public health surveillance system.  Upon completion, the system will allow for electronic capture of disease data, case assignment and tracking, addition of public health case investigation data and data export. 



Occurring over a long period of time (more than 1 year).


Cluster investigation:
A review of an unusual number, real or perceived, of health events (for example, reports of cancer) grouped together in time and location. Cluster investigations are designed to confirm case reports; determine whether they represent an unusual disease occurrence; and, if possible, explore possible causes and contributing environmental factors.


Coarse particles:

See Particulate matter



The process of burning. Many important air pollutants, such as sulfur dioxide, nitrogen oxides, and small particles, are the products the combustion of fuels such as coal, oil, gasoline, and wood. 



The amount of one substance dissolved or contained in a unit amount of another substance, or the relative proportions of two or more quantities in a mixture. Sea water, for example, contains a higher concentration of salt than does fresh water. Concentrations, which may be expressed in various ways, are often described in terms of a component's percentage by weight or volume. Very low concentrations, such as those of various substances in the atmosphere, are commonly expressed in parts per million (ppm).


Consumption advisory:

A governmental warning advising people not to eat, or to eat only in limited quantities, certain foods, such as fish contaminated with mercury.


The Connecticut Department of Public Health issues a yearly advisory for decreasing fish consumption when chemical contaminant levels are unsafe. Fish from Connecticut waters are a good low cost source of protein. Unfortunately, fish can take up (bio-accumulate) chemicals such as mercury and polychlorinated biphenyls (PCBs) that may affect health. 



Any substance or material that enters a system (such as the environment) where it is not normally found.


Criteria Pollutants:

EPA uses six "criteria pollutants" as indicators of air quality, and has established for each of them a maximum concentration above which adverse effects on human health may occur. These six pollutants are: Ozone, Nitrogen Dioxide, Sulfur Dioxide, Particulate Matter (less than 10 microns), Lead, Carbon Monoxide.


Cumulative exposure:

The sum of exposures of an organism to a chemical over a period of time.




Detection limit:
The lowest concentration of a chemical that can reliably be distinguished from a zero concentration.


Developmental disabilities:

A diverse group of severe chronic conditions that are due to 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. Developmental disabilities begin anytime during development up to 22 years of age and usually last throughout a person’s lifetime. 



Any of a family of compounds known chemically as dibenzo-p-dioxins. Dioxin is considered highly toxic and may cause cancer or birth defects. Dioxins are created as by-products in many industrial processes.


Disinfectant byproducts:

A compound formed by the reaction of a disinfenctant such as chlorine with organic material in the water supply; a chemical byproduct of the disinfection process.


Domestic water use:

Using water for household purposes, such as drinking, preparing food, bathing, washing clothes and dishes, flushing toilets, or watering lawns and gardens. Also called residential water use. The water may be obtained from a public supply or may be self-supplied by a homeowner (such as by a well). 





The interacting system of living things and their nonliving environment.



A chronic and progressive disease in which the small air sacs in the lungs become abnormally large. Emphysema causes difficulty in breathing, coughing, and an increased susceptibility to infection; it can also increase the likelihood of heart disease. It is often associated with long-term cigarette smoking.


Endocrine disruptors:

Synthetic or naturally occurring chemicals that when absorbed into the body either mimic or block hormones and disrupt the body's normal functions. This disruption can happen through altering normal hormone levels, halting or stimulating the production of hormones, or changing the way hormones travel through the body, thus affecting the functions that these hormones control. Chemicals that are known human endocrine disruptors include diethylstilbesterol (the drug DES), dioxin, PCBs, DDT, and some other pesticides. Many chemicals, particularly pesticides and plasticizers, are suspected endocrine disruptors based on limited animal studies.


Environmental epidemiology:

The study of the effect on human health of physical, biological, and chemical factors in the external environment. Can include examining specific populations or communities exposed to different ambient environments to clarify the relationship between physical, biological, or chemical factors and human health.


Environmental hazards:

Situations or conditions in which something in the environment, such as radiation, a chemical, or other pollutant, can cause human illness or injury.


Environmental Information Exchange Network:

A new approach for exchanging environmental data among EPA and its state, tribal, and territorial partners. The Exchange Network electronically collects and stores accurate information, integrates information from across many disparate sources, and provides secure access to information in a timely manner. 


Environmental Public Health Tracking:

The ongoing collection, integration, analysis, and interpretation of data about environmental hazards, exposure to environmental hazards, and human health effects potentially related to exposure to environmental hazards. It includes dissemination of information learned from these data. 


Environmental toxicology:

Scientific analysis of the relationship between exposure to hazardous substances found in the environment and adverse health effects in people. 



Contact with a chemical by swallowing, breathing, or direct contact (such as through the skin or eyes). Exposure may be short term (acute) or long term (chronic). As part of its mission to protect human life and the environment, EPA conducts research to characterize, predict and diagnose human and ecosystem exposure to harmful pollutants and other conditions in the air, water, soil, dust and food. 




Fish consumption advisory:

See consumption advisory



Pesticide that kills fungi (including blights, mildews, molds, and rusts).



Geographic information system (GIS):
A mapping system that uses computers to collect, store, manipulate, analyze, and display data. For example, GIS can show the concentration of a contaminant within a community in relation to points of reference such as streets and homes.

The Geographic Information Systems at the CT Department of Environmental Protection (DEP) play an important role in the DEP's mission of protecting and preserving the environment for present and future generations. DEP develops and maintains a statewide automated geographic storage and retrieval system that can rapidly integrate and analyze large amounts of spatial map and file data over any selected geographic area.  DEP also develops and shares geospatial information with federal, state, and municipal government agencies such as the U.S. Geological Survey, Environmental Protection Agency, Federal Emergency Management Agency, CT Department of Public Health, CT Department of Transportation, and the CT Office of Policy and Management. 


Health Insurance Portability and Accountability Act (HIPAA):

The Administrative Simplification provisions of the Health Insurance Portability and Accountability Act of 1996 (HIPAA) are intended to reduce the costs and administrative burdens of health care by making possible the standardized, electronic transmission of many administrative and financial transactions that are currently carried out manually on paper. 



Pesticide that kills weeds and other plants that grow where they are not wanted.



A chemical compound consisting only of hydrogen and carbon. Hydrocarbons, which occur naturally in petroleum, natural gas, coal, and wood, are often used as fuels. They are emitted into the air when the fuel does not burn or burns only partially. Hydrocarbons react in the presence of nitrogen oxides and sunlight to form ground-level ozone, a major component of smog. The most commonly tracked hydrocarbons are volatile organic compounds (VOCs).




Indoor air quality (IAQ):

The overall state of the air inside a building as reflected by the presence of pollutants, such as dust, fungi, animal dander, volatile organic compounds, carbon monoxide, and lead. 



A local reaction when tissue becomes irritated, injured, or infected. Inflammation is usually characterized by pain, redness, swelling, heat, and sometimes loss of function.



An indicator identifies and communicates a system's status.  An environmental public health indicator (EPHI) 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 (i.e., risk factor, intervention) in a specified population through direct or indirect measures.



Pesticides that kill insects and other arthropods.




Lead (Pb):

A soft, heavy, blue-gray metal. It occurs naturally in the earth’s crust, and human activities such as burning fossil fuels, mining, and manufacturing have spread it throughout the environment, including our homes and workplaces.  Lead is hazardous to human health. Lead can occur in the air as small particles, often from emissions from lead smelters and other metal-processing plants.  Lead exposure can also occur through:

  > Eating food or drinking water that contains lead; 

  > Swallowing or breathing chips or dust from lead-based paints;

  > Working in a job where lead is used; 

  > Using health-care products or folk remedies that contain lead;

  > Engaging in certain hobbies in which lead is used (for example, making stained glass).


Eating lead-based paint chips, chewing on objects painted with lead-based paint, or swallowing house dust or soil that contains lead are the most common routes of exposure to lead for small children.





A naturally occurring element that is found in air, water and soil. It exists in several forms: elemental or metallic mercury, inorganic mercury compounds, and organic mercury compounds. Elemental or metallic mercury is a shiny, silver-white metal and is liquid at room temperature. It is used in thermometers, fluorescent light bulbs and some electrical switches. When dropped, elemental mercury breaks into smaller droplets which can go through small cracks or become strongly attached to certain materials. At room temperature, exposed elemental mercury can evaporate to become an invisible, odorless toxic vapor. People can be exposed to elemental mercury vapor when products that contain mercury break and expose mercury to the air, particularly in poorly-ventilated spaces.Inorganic mercury compounds take the form of mercury salts and are generally white powder or crystals, with the exception of mercuric sulfide (cinnabar) which is red.


Inorganic mercury compounds have been included in products such as fungicides, antiseptics or disinfectants. Some skin lightening and freckle creams, as well as some traditional medicines, can contain mercury compounds.


Organic mercury compounds, such as methylmercury, are formed when mercury combines with carbon. Microscopic organisms convert inorganic mercury into methylmercury, which is the most common organic mercury compound found in the environment. Methylmercury accumulates up the food chain.



Any substance produced by biological processes in the human body. In some cases, it is not possible to measure certain substances (for example, pesticides) in the human body to determine exposure to those substances, but instead it is possible to measure the secondary substance or metabolite that is created when the human body breaks down the primary substance.



This is simply "data about data". Metadata is the information about a data source, for example, a book contains information, but there is also information about that book such as the author and publisher - this is the metadata.



A chemical element that usually has a shiny surface, is generally a good conductor of heat and electricity, and can be melted or fused, hammered into thin sheets, or drawn into wires. The metals comprise about two-thirds of all known elements. Unlike nonmetals, metals form positive ions and basic oxides and hydroxides. Upon exposure to moist air, many metals react chemically with the oxygen of the atmosphere to form a metallic oxide, such asrust on exposed iron.



A unit of mass equal to one millionth of a gram.


Micron: A unit of length equal to one millionth of a meter.


Milligram: A unit of mass equal to one thousandth of a gram.


Mobile source:

A moving object that is a source of pollution. Mobile sources include road vehicles, such as cars, trucks, buses, and motorcycles, and nonroad vehicles, such as trains, planes, and gasoline-powered lawn mowers. A mobile source is distinguished from a stationary source or point source.




National Ambient Air Quality Standards (NAAQS):

Standards set by the EPA for all criteria pollutants. EPA has established primary standards to protect public health and secondary standards to protect other aspects of public welfare, such as preventing materials damage, preventing crop and vegetation damage, or assuring visibility.


National Electronic Disease Surveillance System (NEDSS):

A national initiative that promotes the use of data and information system standards to advance the development of efficient, integrated, and interoperable surveillance systems at federal, state and local levels.  It is a major component of the Public Health Information Network (PHIN). 



A compound containing nitrogen that can exist in the atmosphere or as a dissolved gas in water and which can have harmful effects on humans and animals. Nitrates in water can cause severe illness in infants and domestic animals. A plant nutrient and inorganic fertilizer, nitrate is found in septic systems, animal feed lots, agricultural fertilizers, manure, industrial waste waters, sanitary landfills, and garbage dumps.


Nitrogen oxide:

A criteria air pollutant. Nitrogen oxides (collectively known as NOx) are produced from burning fossil fuels, including gasoline and coal. Nitrogen oxides react with volatile organic compounds to form smog. Nitrogen oxides are also major components of acid rain. They may be harmful to the lungs and aggravate asthmatic symptoms. 


Nonattainment area:

A geographic area of the United States in which the level of a criteria air pollutant persistently exceeds the level allowed by the National Ambient Air Quality Standards (NAAQS). An area may have acceptable levels of one criteria air pollutant but unacceptable levels of one or more other criteria air pollutants; thus, an area can be both attainment and nonattainment at the same time. It has been estimated that 60% of Americans live in nonattainment areas.


Nonpoint source:

The source of runoff water coming from an area such as a yard, parking lot, pasture, or other urban or agricultural area.




Ozone (O3):

A criteria air pollutant. Ozone is a variety of the oxygen molecule that consists of three atoms of oxygen instead of the more common two atoms. It occurs in nature, for example, when lightning strikes. Ozone is also formed by a chemical reaction of nitrogen oxides and volatile organic compounds together with sunlight and warm temperatures. In the upper atmosphere, high concentrations of ozone act to shield the Earth from harmful ultraviolet radiation from the sun. Holes in the ozone layer allow excess radiation to reach the Earth's surface, which increases the risk of skin cancer in humans. At ground-level, ozone is often referred to as smog. Breathing too much ozone can damage lung tissue and aggravate respiratory problems like asthma and emphysema. High ozone levels are also harmful to plants, crops, and trees, as well as to materials like rubber and paints. Ozone is a widespread and serious urban air pollution problem.



Insecticides that contain chlorine.  These insecticides were commonly used in the past, but many have been removed from the market due to their health and environmental effects and their persistence (e.g. DDT and chlordane).



Pesticides that contain phosphorus; short-lived, but some can be toxic when first applied.




Part per billion (ppb):

Unit of measurement commonly used to express a contamination ratio, as in establishing the maximum permissible amount of a contaminant in water, land, or air.


Part per million (ppm):

Unit of measurement commonly used to express a contamination ratio, as in establishing the maximum permissible amount of a contaminant in water, land, or air.


Particulates, particulate matter (PM-2.5 and PM-10):

A criteria air pollutant. Particulate matter includes dust, soot, smoke, and other small solid particles found in the air or in emissions. Particulates are produced by many sources, including the burning of diesel fuels by trucks and buses, incineration of garbage, mixing and application of fertilizers and pesticides, road construction, industrial processes such as steel manufacture, mining operations, agricultural burning, and operation of fireplaces and wood stoves.


Particulates include both fine particles (PM-2.5), which come primarily from fuel combustion in cars and trucks, and coarse particles (PM-10), which result largely from vehicles traveling on unpaved roads. Particulate pollution can cause eye, nose, and throat irritation and other health problems. Exposure to fine particles is associated with heart and lung disease, increased respiratory symptoms and disease, decreased lung function, and even premature death. Exposure to coarse particles is primarily associated with the aggravation of respiratory conditions, such as asthma.



Any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest. Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides, and various other substances used to control pests. Under United States law, a pesticide is also any substance or mixture of substances intended for use as a plant regulator, defoliant, or desiccant.   


Persistent chemicals:

Chemicals, such as organochlorine compounds, that remain in the environment for a long time and can accumulate in the fat of people and animals exposed to them.


Point source:

Also Stationary source. A source of pollution that is stationary, or stays in one place. Some 24% of air toxics come from large stationary sources, such as chemical plants, oil refineries, and pulp and paper mills.


Primary standard:

A pollution limit set by the EPA for a criteria pollutant and based on health effects.


Polychlorinated biphenyls (PCBs):

Mixtures of synthetic organic chemicals with the same basic chemical structure and similar physical properties ranging from oily liquids to waxy solids. Due to their non-flammability, chemical stability, high boiling point and electrical insulating properties, PCBs 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 applications. More than 1.5 billion pounds of PCBs were manufactured in the United States prior to cessation of production in 1977. 


Public Health Information Network (PHIN):

CDC’s vision for advancing fully capable and interoperable information systems in the many organizations that participate in public health. PHIN is a national initiative to implement a multi-organizational business and technical architecture for public health information systems. 





A colorless, naturally occurring radioactive gas found in some soils or rocks.  


Radon-resistant construction:

Affordable and simple techniques that, when incorporated during construction of a new home, reduce indoor radon levels by preventing radon entry and providing a means for venting radon to the outdoors.




Secondary standard:

A pollution limit set by the EPA for a criteria pollutant and based on environmental effects such as damage to property, plants, visibility, etc.


Smog: A mixture of pollutants, principally ground-level ozone, produced by chemical reactions in the air. Smog can harm health, damage the environment, and hinder visibility. Major smog occurrences are often linked to heavy motor vehicle traffic, sunshine, high temperatures, and certain other weather conditions. Smog may develop far from the source of smog-forming chemicals (such as volatile organic compounds), since the chemical reactions that cause smog occur high in the air, as the prevailing winds carry the reacting chemicals from their sources.


Sulfur dioxide (SO2):

A colorless gas formed during the burning of fuels containing sulfur, such as coal. Breathing SO2 may irritate the respiratory system and aggravate asthmatic symptoms.





A cluster of databases on toxicology, hazardous chemicals, and related areas maintained by the National Library of Medicine.


Toxic Release Inventory (TRI):

EPA’s list of more that 600 designated chemicals that threaten health and the environment. Authorized under the Emergency Planning and Community Right-To-Know Act (EPCRA) of 1986, this system requires manufacturers to report releases of these chemicals to EPA and State governments. EPA compiles the data in an online, publicly accessible national computerized database. 




Volatile organic compounds (VOCs):

Substances containing carbon and various proportions of other elements, such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, and nitrogen; these substances easily become vapors or gases. VOCs are commonly found in gasoline, solvents (paint thinners, lacquer thinner, degreasers, and dry cleaning fluids), oil-based paints and inks, and consumer products, such as aerosol spray products. VOCs react with nitrogen oxides, sunlight, and heat to form ozone. Many VOCs are considered air toxics.