This section contains definitions that will help you understand technical and environmental terms used throughout this site as well as in the links provided. Use the index below to help you navigate through the terms. The definitions below have been compiled through numerous governmental and non-governmental sources. Of these sources, the majority of terms were obtained from Merriam-Webster's Collegiate Dictionary and the U.S.A. Environmental Protection Agency's Terms of Environment
Terms Beginning With:
A
Abiotic: Refers to the non-living components of the environment. Climate is an example of an abiotic factor.
Acute Exposure: A single exposure to a toxic substance which may result in severe biological harm or death. Acute exposures are usually characterized by short-term impacts leading to more subtle impacts, as compared to longer, or chronic, exposure over a period of time.
Acute Toxicity: The ability of a substance to cause severe biological harm or death soon after a single exposure or dose. Also, any poisonous effect resulting from a single short-term exposure to a toxic substance.
Adsorption: Removal of a pollutant from air or water by collecting the pollutant on the surface of a solid material.
Advisory: A non-regulatory document that communicates risk information to those who may have to make risk management decisions. Advisories are generally a precautionary method used to protect individuals from health hazards. For instance, fish advisories warn against the consumption of fish from certain lakes due to excessive contamination of fish tissue.
Air Pollutant: Any substance in air that could harm humans, other animals, vegetation, or material. Pollutants may include almost any natural or artificial composition of airborne matter. They may be in the form of solid particles, liquid droplets, gases, or in some combination thereof. Generally, they fall into two main groups:
(1) those emitted directly from identifiable sources (primary pollutants) and;
(2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents, with or without photoactivation.
Air Quality Criteria: The levels of pollution and lengths of exposure above which adverse health and welfare effects may occur.
Air Quality Standards: The level of pollutants prescribed by regulations that are not be exceeded during a given time in a defined area.
Ambient Air: Any unconfined portion of the atmosphere: open air, surrounding air.
Anaerobic: Living, active, occurring, or existing in the absence of free oxygen.
Anthropogenic: Of, relating to, or resulting from the influence of human beings.
Anthropogenic Source: Sources of pollution resulting from human activities.
Area Source: Any source of air pollution that is released over a relatively small area but which cannot be classified as a point source. Such sources may include vehicles and other small engines, small businesses and household activities, or biogenic sources such as a forest that releases hydrocarbons.
Atmosphere: The whole mass of air surrounding the Earth.
Autotrophic: Describes organisms which do not eat other life forms, but derive carbon for metabolic synthesis from carbon dioxide, such as plants. Many such organisms are eaten by other organisms.
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B
Background Level:
The concentration of a substance in an environmental media (air, water, or soil) that occurs naturally and is not the result of human activities.
Bioaccumulation: The process by which chemical substances are accumulated by organisms from exposure to water, sediments, or soil directly or through consumption of food containing the chemicals.
Bioaccumulation Factor (BAF): The ratio of the concentration of a given compound in the tissues of an organism and its concentration either in the media in which the organism lives or in the tissues of biota on which the organism feeds.
Bioavailable: The fraction of the total chemical in the surrounding environment that can be taken up by organisms. The chemical may be dissolved or reversibly bound to particles in water, air, sediment, or soil, or contained in food items.
Bioconcentration: The process by which contaminants are directly taken up by organisms from the medium in which they live.
Biogeochemical: Of or relating to the partitioning and cycling of chemical elements and compounds between the living and nonliving parts of an ecosystem.
Biomagnification: The increase in tissue concentrations of accumulated chemicals from one trophic level to the next (i.e., organisms contain higher concentrations of the substance than their food sources).
Biomethylate: To introduce a chemical, functional group called a methyl group (containing 1 carbon and 3 hydrogen atoms) into a molecule via a biological process.
Biosphere: The portion of the Earth and its atmosphere that can support life.
Biotic: Refers to the living components of the environment, such as plants, animals and microorganisms.
Body Burden: The amount of a chemical stored in the body at a given time, especially a potential toxin, as the result of exposure.
Budget: A quantity (as of energy or matter) involved in, available for, or assignable to a particular situation; also : an account of gains and losses of such a quantity.
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C
Carcinogen: Any substance that can cause or aggravate cancer.
Cation: A molecule which has a positive electrostatic charge.
Chemical Compound: A distinct substance formed by the union or two or more elements in definite proportion by weight.
Chronic Toxicity: The capacity of a substance to cause long-term poisonous health effects in humans, animals, fish and other organisms.
Chronic Exposure: Exposure to a substance over a long period of time.
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D
Dental Amalgam: An alloy of mercury with another metal (commonly silver) that is solid or liquid at room temperature according to the proportion of mercury present and is used especially in making tooth cements.
Dermal Toxicity: The ability of a toxic chemical to poison people or animals by contact with the skin.
Dry Deposition: The deposition of a substance in the atmosphere to land or water via adsorption onto particles that fall out of the air.
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E
Ecology: The relationship of living things to one another and their environment, or the study of such relationships.
Ecosystem: The interacting system of a biological community and its non-living environmental surroundings.
Effluent: Wastewater (treated or untreated) that flows out of a treatment plant, sewer, or industrial facility. Generally refers to wastes discharged into surface waters.
Element: An element is matter composed of similar atoms. Substances that cannot be broken down to simpler forms by chemical means are considered elementary.
Environment: The sum of all biotic and abiotic conditions affecting the life, development and survival of an organism or an ecological community.
Erosion: The wearing away of land surface by wind or water, intensified by land-clearing practices related to farming, residential or industrial development, road building or logging.
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F
Flux: A flowing or flow of energy or matter between different media.
Food Chain: A sequence of organisms, each of which uses the next, lower member of the sequence as a food source.
Food Web: The feeding relationships by which energy and nutrients are transferred from one species to another.
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G
Grasshopper Effect: Some substances can travel great distances around the globe through the atmosphere. Touching down on land, oceans and freshwater bodies, they then volatize or evaporate into the atmosphere once again, and travel once more to touch down in another spot until they ultimately gather in the colder climates.
Ground Water: The supply of fresh water found beneath the Earth's surface, usually in aquifers, which supplies wells and springs. Because ground water is a major source of drinking water, there is growing concern over contamination from leaching agricultural or industrial pollutants or leaking underground storage tanks.
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H
Habitat: The place where a population (e.g., human, animal, plant, microorganism) lives and its surroundings, both living and non-living.
Half-life:The time required for a pollutant to lose one-half of its original concentration. For example, the biochemical half-life of DDT in the environment is 15 years.
Heavy Metals: A group of toxic metallic elements and their compounds.
Heterotrophic: Refers to organisms which eat other life forms to acquire complex organic compounds of nitrogen and carbon for metabolism.
Hg: The symbol used to denote elemental mercury on the periodic table of elements.
Hg0: The chemical symbol used to denote mercury in its elemental, or uncharged, form.
Hg2+: The chemical symbol used to denote mercury in its positively charged (cationic), or reactive, state.
Hg(p): The symbol used to denote mercury attached onto or absorbed into a particle.
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I
Incineration: The destruction of waste by controlled burning at high temperatures.
Inorganic: Refers to chemical substances that do not contain carbon.
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L
Leachate: Water that has collected contaminants as it trickles through wastes or soils. Leaching may occur in farming areas, feedlots, and landfills, and may result in hazardous substances entering surface water, ground water, or soil.
Leaching: The process by which soluble constituents are dissolved and filtered through the soil by a percolating fluid (see: leachate).
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M
Mercury (Hg): Highly toxic heavy metal that can accumulate in the environment and living tissue.
Methyl Group: An alkyl group (CH3) derived from methane by removal of one hydrogen atom.
Methyl Mercury (MeHg): Any of various toxic compounds of mercury containing the complex CH3Hg- that often occur as pollutants which accumulate in living organisms (such as fish), especially in higher levels of a food chain.
Methylate: To introduce a chemical, functional group called a methyl group (containing 1 carbon and 3 hydrogen atoms) into a molecule, either biotically or abiotically.
Microgram: One microgram is equal to one millionth of a gram. Denoted by the symbol "µg".
Mole: The base unit of amount of pure substance in the International System of Units that contains the same number of elementary entities as there are atoms in exactly 12 grams of the isotope carbon 12.
Molecule: The smallest division of a substance that still retains or exhibits all the properties of the substance and is comprised of at least 2 atoms.
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N
Nanogram: One nanogram is equal to one billionth of a gram. Denoted by the symbol "ng"
Neurotoxin: Neurotoxins affect the central nervous system and and can cause brain damage.
Non-Point Sources: Diffuse pollution sources (i.e., without a single point of origin or not introduced into a receiving stream from a specific outlet). The pollutants are generally carried off the land by stormwater. Common non-point sources are agriculture, forestry, urban, mining, construction, dams, channels, land disposal, saltwater intrusion, and city streets.
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O
Organic: Refers to compounds containing carbon.
Oxidation: The removal of electrons from an element or compound.
Oxidation-Reduction: A chemical reaction in which one or more electrons are transferred from one atom or molecule to another.
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P
Pathway: The physical course a chemical or pollutant takes from its source to the exposed organism.
Persistence: Environmental persistence refers to the length of time a substance resides in environmental media and is usually defined in terms of half-life or residence time. A persistent substance degrades very slowly in the environment and therefore has a long half-life. Physical, chemical and biological processes that degrade a substance are considered in determining its half-life; dilution or transportation to other locations or media generally are not. For a substance to be considered persistent, it must meet a criterion in at least one medium.
Photochemical: Describes a process resulting from the chemical properties of radiant energy (for example, sunlight).
Piscivorous: Refers to organisms that consume fish.
Plankton: Microscopic floating or weakly self-propelled plants (phytoplankton) and animals (zooplankton) in aquatic ecosystems.
Point Source: A stationary location or fixed facility from which pollutants are discharged; any single identifiable source of pollution; e.g., a pipe, ditch, ship, ore pit, factory smokestack.
Pollutant: Generally, any substance introduced into the environment that adversely affects the usefulness of a resource or the health of humans, animals, or ecosystems.
Pollution: Generally, the presence of a substance in the environment that, because of its chemical composition or quantity, prevents the functioning of natural processes and produces undesirable environmental and health effects.
Pollution Prevention: The use of processes, practices, materials, products or energy that avoid or minimize the creation of pollutants and waste, and reduce overall risk to human and environmental health. Pollution prevention focuses on avoiding the creation of pollutants rather than trying to manage them after they have been created.
Pool: The quantity of a given substance found in an environmental "compartment", or media, such as the air, water, soil, or a given geographic area or feature.
Population: A group of interbreeding organisms occupying a particular space; the number of humans or other living creatures in a designated area.
ppm: Abbreviation for parts per million, describing the number of unit parts of a substance contained in a million unit parts of another substance.
Predation:The mode of life where the primary means for obtaining food is through the killing and eating of other creatures (prey).
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R
Reduction: The addition of electrons to an element or compound.
Residence Time: The duration of persistence of a mass or substance in a medium or place.
Route of Exposure: The avenue by which a chemical comes into contact with an organism, e.g., inhalation, ingestion, dermal contact, injection.
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S
Safe Water: Water that does not contain harmful bacteria, toxic materials, or chemicals, and is considered safe for drinking even if it may have taste, odor, color, and certain mineral problems.
Sediments: Soil, sand, and minerals that are suspended in water, or are being transported, or that settle in loose layers, typically as mud.
Sink: Place in the environment where a compound or material collects.
Smog: Air pollution typically associated with oxidants.
Sport Fish: Species like trout, salmon, or bass, caught for sport.
Surface Water: All water naturally open to the atmosphere (rivers, lakes, reservoirs, ponds, streams, impoundments, seas, estuaries, etc).
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T
Terrestrial: Of or relating to land as distinct from air or water.
Toxicity: The degree to which a substance or mixture of substances can harm humans or animals. Acute toxicity involves harmful effects in an organism through a single or short-term exposure. Chronic toxicity is the ability of a substance or mixture of substances to cause harmful effects over an extended period, usually upon repeated or continuous exposure sometimes lasting for the entire life of the exposed organism. Subchronic toxicity is the ability of the substance to cause effects for more than one year but less than the lifetime of the exposed organism.
Transboundary Pollutants: Air pollution that travels from one jurisdiction to another, often crossing provincial or international boundaries. Also applies to water pollution.
Trophic Levels: A functional classification of species that is based on feeding relationships (e.g., generally aquatic and terrestrial green plants comprise the first trophic level, herbivores comprise the second and carnivores comprise the third).
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U
ug: Abbreviation for microgram, meaning one one-millionth of a gram. Can be used, for example, to illustrate concentrations of a given substance in a medium, as in 5ug/l (five-millionths of a gram per litre) or 5 ug/g (five millionths of a gram per gram of another substance).
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V
Valence: The degree of combining power of an element as shown by the number of atomic weights of a univalent element (such as hydrogen) with which the atomic weight of the element will combine or for which it can be substituted or with which it can be compared.
Volatile: Any substance that evaporates readily.
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W
Watershed: The land area that drains into a stream; the watershed for a major river may encompass a number of smaller watersheds that ultimately combine at a common point.
Wet Deposition: The deposition of a substance in the atmosphere to land or water via rain or snow.
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