United States         Office of
Environmental Protection    Public Affairs (A-107)       March 1988
Agency            Washington DC 20460      OPA-87-017



Glossary of


Environmental  Terms

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Introduction
This glossary of environmental and related terms replaces  "Common Environmental
Terms," published by the Environmental Protection Agency in 1974 and revised in 1978. It is
designed to give the user an explanation of the more commonly used environmental terms
appearing in EPA publications, news releases and other Agency documents available to the
general public, students, the news media, and Agency employees. The terms and definitions
in this publication were selected to give the user a general sense of what a term or phrase
means in relatively non-technical language, although it was obviously necessary to use some
scientific terminology.
  The terms selected for inclusion came from previously published lists, internal glossaries
produced by various programs, and specific suggestions made by many Agency programs
and offices. The chemicals and pesticides selected for inclusion were those most frequently
referred to in Agency publications or which are the subject of major EPA regulatory or
program activities.
  Definitions or information about substances or program activities not included in this
glossary may be found in EPA libraries or scientific/technical reference documents or may be
obtained from the various program offices.
  The definitions do not constitute  the Agency's official use of terms and phrases for
regulatory purposes. Nothing in this document should be construed to in any way alter or
supplant any other federal document. Official terminology may be found in the laws and
related regulations as published in such sources as the Congressional Record and the Federal
Register.
  Users with suggestions for future editions should write to the Publications Division, Office
of Public Affairs, A-107, USEPA Washington DC, 20460.

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A Administrative Order On Consent: A legal agreement signed by EPA and an
individual, business, or other entity through which the violator agrees to pay
Abatement: Reducing the degree or intensity of, or eliminating, pollution. for correction of violations, take the required corrective or cleanup actions, or
Abandoned Well: A well whose use has been permanently discontinued or refrain from an activity. It describes the actions to be taken, may be subject to a
which is in a state of disrepair such that it cannot be used for its intended comment period, applies to civil actions, and can be enforced in court.
Administrative Procedures Act A law that spells out procedures and require-
ments related to the promulgation of regulations.
ABEL EPA’s computer model for analyzing a violator’s ability to pay a civil
penalty. Adsorption: 1. Adhesion of molecules of gas, liquid, or dissolved solids to a
Absorption: The passage of one substance into or through another; e.g:, an surface. 2. An advanced method of treating wastes in which activated carbon
operation in which one or more soluble components of a gas mixture are removes organic matter from wastewater.
dissolved in a liquid. Adulterants: Chemical impurities or substances that by law do not belong in a
food, or in a pesticide.
Acceleratoc In radiation science, a device that speeds up charged particles
such as electrons or protons. Advanced Waste Water Treatment: Any treatment of sewage that goes
Accident Site: The location of an unexpected occurrence, failure or loss, either beyond the secondary or biological water treatment stage and includes the
at a plant or along a transportation route, resulting in a release of hazardous removal of nutrients such as phosphorus and nitrogen and a high percentage
ria ls. of suspended solids. (See primary, secondary treatment.)
Acclinia.tizatlon: The physiological and behavioral adjustments of an organ- Advisory A non-regulatory document that communicates risk information to
ism to changes in its environment. persons who may have to make risk management decisions.
Acetyickoline: A substance iii the human body having important Aeration: A process which promotes biological degradation of organic water.
neurotransmifter effects on various internal systems; often used as a broncho- The process may be passive (as when waste is exposed to air), or active (as
when a mixing or bubbling device introduces the air).
constrictor.
Aeration Tank: A chamber used to inject air into water.
Acid Deposition: A complex chemical and atmospheric phenomenon that
occurs when emissions of sulfur and nitrogen compounds and other sub- Aerobic: Life or processes that require, or are not destroyed by, the presence of
stances are transformed by chemical processes in the atmosphere, often far oxygen. (See: anaerobic.)
from the original sources, and then deposited on earth in either a wet or dry Aerobic Treatment Process by which microbes decompose complex organic
form. The wet forms, popularly called “acid ram,” can fall as rain, snow, or compounds in the presence of oxygen and use the liberated energy for
fog. The dry forms aie acidic gases or particulates. reproduction and growth. Types of aerobic processes indude extended aera-
Add Rain: (See: acid deposition) tion, trickling filtration, and rotating biological contactors.
Action Levels: 1. Regulatory levels recommended by EPA for enforcement by Aerosol: A suspension of liquid or solid particles in a gas.
FDA and USDA when pesticide residues occur in food or feed commodities for Afterburnec In incinerator technology, a burner located so that the combus-
reasons other than the direct application of the pesticide. As opposed to tion gases are made to pass through its flame in order to remove smoke and
“tolerances which are established for residues occurring as a direct result of odors. It may be attached to or be separated from the incinerator proper.
proper usage, action levels are set for inadvertent residues resulting from
previous legal use or accidental contamination. 2. In the Superftmd Agent Orange: A toxic herbicide and defoliant which was used in the Vietnam
heexistenceofacontaminantconcentrationin the environmenthigh enough conflict, It contains 2,4,5-trichiorophenoxyacitic acid (2,4,5-1) and 2-4 di-
to warrant action or trigger a response under SARA and the National Oil and chiorophenoxyacetic acid (2,4-D) with trace amounts of dioxin.
Hazardous Substances Contingency Plan. The term can be used similarly in Agglomeration: The process by which precipitation particles grow larger by
other regulatory programs. (See: tolerances.) collision or contact with doud partides or other precipitation partides.
Activated Caibon A highly adsorbent form of carbon used to remove odors Agglutination: The process of uniting solid partides coated with a thin layer of
and toxic substances from liquid or gaseous emissions. In waste treatment itis adhesive material or of arresting solid partides by impact on a surface coated
used to remove dissolved organic matter from waste water. It is also used in with an adhesive.
motor vehicle evaporative control systems. Agricultural Pollution: The liquid and solid wastes from farming, includirigt
Activated Sludge: Sludge that results when primary effluent is mixed with runoff and leaching of pesticides and fertilizers; erosion and dust from pio-
bacteria-laden sludge and then agitated and aerated to promote biological wing. animal manure and carcasses; crop residues, and debris.
tieatment. This speeds breakdown of organic matter in raw sewage undergo- Airborne Particulates: Total suspended particulate matter found in the atmos-
ing secondary waste treatment. phere as solid partides or liquid droplets. Chemical composition of particu-
Active Ingredient In any pesticide product, the component which kills, or lates varies widely, depending on location and time of year. Airborne particu-
otherwise controls, target pests. Pesticides are regulated primarily on the basis lates indude: windblown dust, emissions from industrial processes, smoke
of active ingredients. from the burning of wood and coal, and the exhaust of motor vehides.
Acute Exposure: A single exposure to a toxic substance which results in severe Airborne Release: Release of any chemical into the air.
biological harm or death. Acute exposures are usually characterized as lasting Air Changes Per Hour (ACH): The movement of a volume of air in a given
no longer than a day. period of time; if a house has one air change per hour, it means that all of the air
Acute Toxicity The ability of a substance to cause poisonous effects resulting in the house will be replaced in a one-hour period.
in severe biological harm or death soon after a single exposure or dose. Also, Air Contaminant Any particulate matter, gas, or combination thereof, other
any severe poisonous effect resulting from a single short-term exposure to-a than water vapor or natural air. (See: air pollutant.)
toxic substance. (See: chronic toxicity, toxicity.)
Air Curtain: A-method of containing oil spills. Air bubbling through a per-
Adaptation: Changes in an organism’s stnretw or habit that help it adjust to , forated pipe causes an upward water flow that slows the spread of oil. It can
its surroundings. - also be used to stop fish from entering polluted water.
Add-on Control Device: An air pollution control device suck as carbon adsor- . Air Mass: A widespread body of air that gains certain meteorological or
her or incinerator which reduces the pollution in an exhaust gas. The control polluted characteristics—e.g., a heat inversion or smogginess—while set in
device usually does not affect the process being con n lied-and thusis “add- One location. The characteristics can change as it moves away.
on technology as opposed to a scheme to control pôllutiop through making
Air Monitoring: (See: monitoring)
some alteration to the basic process. .,.
Adhesloit Molecular attraction which holds the surfaces of timisubstan s - Air Pollutant Any substance in air which could, if in high enough concentra-
tion, harm man, other animals, vegetation, or material. Pollutants may in-
contact.
dude almost any natural or artificial composition of matter capable of being
Administrative Ordec A legal document signed by EPA directing an in airborne. They may be in the form of solid particles, liquid droplets, gases, or
dividual, business, or other entity to take corrective action or refrain from an combinations of these forms. Generally, they fall into two main groups: (1)
activity. It describes the violations and actions to be taken, andicanbeenforced those emitted directly from identifiable sources and (2) those produced in the
in court Such orders may be issued, for example. as a result of ‘ is ’a air by interaction between two or more primary pollutants, or by reaction with
tive complaint whereby the respondent is ordered to pay a penalty for viola- normal atmospheric constituents, with or without photoactivation. Exclusive
tioro of a statute. of pollen, fog, and dust, which are of natural origin, about 100 contaminants
2 -

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have been identified and fall into the following categories: solids, sulfur
compounds, volatile organic chemicals, nitrogen compounds, oxygen com-
pounds, halogen compounds, radioactive compounds, and odors.
Air Pollution The presence of contaminant or pollutant substances in the air
that do not disperse properly and interfere with human health or welfare, or
produce other harmful environmental effects.
Air Pollution Episode: A period of abnormally high concentration of air
pollutants, often due to low winds and temperature inversion, that can cause
illness and death. (See: episode, pollution.)
Air Quality Control Region: An area—designated by the federal
government—in which communities share a common air pollution problem.
Sometimes several states are involved.
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
may not be exceeded during a specified time in a defined area.
Alachlor A herbicide, marketed under the trade name Lasso, used mainly to
control weeds in corn and soybean fields.
Alan Trade name for daminozide, a pesticide that makes apples redder,
firmer, and less likely to drop off trees before growers are ready to pick them. It
is also used to a lesser extent on peanuts, tart cherries, concord grapes, and
other fruits.
Aldlcarb: An insecticide sold under the trade name Temik. It is made from
ethyl isocyanate.
Algae: Simple rootless plants that grow in sunlit waters in relative proportion
to the amounts of nutrients available. They can affect water quality adversely
by lowering the dissolved oxygen in the water. They arefoodfor fish and small
aquatic animals.
Algal Blooms: Sudden spurts of algal growth, which can affect water quality
adversely and indicate potentially hazardous changes in local water chemis-
by.
Alpha Partide: A positively charged particle composed of 2 neutrons and 2
protons released by some atoms undergoing radioactive decay. The particle is
identical to the nudeus of a helium atom.
Alternate Method: Any method of sampling and analyzing for an air pollutant
which is not a reference or equivalent method but which has been demon-
strated in specific cases to EPA’s satisfaction to produce results adequate for
compliance..
Ambient Mn Any unconfined portion of the atmosphere: open air, surround-
ing air.
Ambient Air Quality Standards: (See: Criteria Pollutants and National
Ambient Air Quality Standards)
Anadromous: Fish that spend their adult life in the sea but swim upriver to
fresh-water spawning grounds to reproduce.
Anaerobic: A life or process that occurs in, or is not destroyed by, the absence
of oxygen.
Antagonism: The interaction of two chemicals having an opposing, or
neutralizing effect on each other, or—given some specific biological effect—a
chemical interaction that appears to have an opposing or neutralizing effect
over what might otherwise be expected.
Antarctic Ozone Hote’ : Refers to the seasonal depletion of ozone in a large
area over Antarctica.
Antibodies: Proteins produced in the body by immune system cells in re-
sponse to antigens, and capable of combining with antigens.
Anti-Degradation Clause: Part of federal air quality and water quality require-
ments prohibiting deterioration where pollution levels are above the legal
limit.
Antigen: A substance that causes production of antibodies when introduced
into animal or human tissue.
Aquifen An underground geological formation, or group of formations, con-
taining usable amounts of groundwater that can supply wells and springs.
Arbitration: A process for the resolution of disputes. Decisions are made by an
impartial arbitrator selected by the parties. These decisions are usually legally
binding. (See: mediation.)
Area of Review: In the UIC program, the area surrounding an injection well
that is reviewed during the permitting process to determine whether the
injection operation will induce flow between aquifers.
Area Source: Any small source of non-natural 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 fuel combustion engines.
Asbestosis: A disease associated with chronic exposure to and inhalation of
asbestos fibers. The disease makes breathing progressively more difficult and
can lead to death.
Asbestos: 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.
Ash: The mineral content of a product remaining after complete combustion.
A-Scale Sound Level: A measurement of sound approximating the sensitivity
of the human ear, used to note the intensity or annoyance of sounds.
Assimilation: The ability of a body of water to purify itself of pollutants.
Atmosphere [ ani: A standard unit of pressure representing the pressure
exerted by a 29.92-inch column of mercury at sea level at 45’ latitude and equal
to 1000 grams per square centimeter. (the) The whole mass of air surrounding
the earth, composed largely of oxygen and nitrogen.
Atomize: To divide a liquid into extremely minute particles, either by impact
with a jet of steam or compressed air, or by passage through some mechanical
device.
Attainment Area: An area considered to have air quality as good as or better
than the national ambient air quality standards as defined in the Clean Air Act.
An area may be an attainment area for one pollutant and a non-attainment area
for others.
Attenuation: The process by which a compound is reduced in concentration
over time, through adsorption, degradation, dilution, and/or transformation.
Attractant: A chemical or agent that lures insects or other pests by stimulating
their sense of smell.
Attrition: Wearing or grinding down of a substance by friction. A contributing
factor in air pollution, as with dust.
Autotrophic: An organism that produces food from inorganic substances.
B
Background Level: In air pollution control, the concentration of air pollutants
in a definite area during a fixed period of time prior to the starting up or on the
stoppage of a source of emission under control. In toxic substances monitor-
ing, the average presence in the environment, originally referring to naturally
occurring phenomena.
BACT—Best Available Control Technology: A emission limitation based on
the maximum degree of emission reduction which (considering energy, en-
vironmental, and economic impacts and other costs) is achievable through
application of production processes and available methods, systems, and
techniques. In no event does BACT permit emissions in excess of those
allowed under any applicable Clean Air Act provisions. Use of the BACT
concept is allowable on a case by case basis for major new or modified
emissions sources in attainment areas and applies to each regulated pollutant.
Bacteria: (Singular: bacterium) Microscopic living organisms which can aid in
pollution control by consuming or breaking down organic matter in sewage. or
by similarly acting on oil spills or other water pollutants. Bacteria in soil, water
or air can also cause human, animal and plant health problems
Baffle Chamber. In incinerator design, a chamber designed to promote the
settling of fly ash and coarse particulate matter by changing the direction
and/or reducing the velocity of the gases produced by the combustion of the
refuse or sludge.
Baghouse Filten Large fabric bag, usually made of glass fibers, used to
eliminate intermediate and large (greater than 20 microns in diameter) parti-
cles. This device operates in a way similar to the bag of an electric vacuum
cleaner, passing the air and smaller particulate matter, while entrapping the
larger particulates.
Baling: Compacting solid waste into blocks to reduce volume and simplify
handling.
Ballistic Separator. A machine that sorts organic from inorganic matter for
composting.
Band Application: In pesticides, the spreading of chemicals over, or next to,
each row of plants in a field.
Banldng A system for recording qualified air emission reductions for later use
in bubble, offset, or netting transactions. (See: emissions trading.)
Bar Screen: In wastewater treatment, a device used to remove large solids.
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Barrier Coating(s): A layer of a material that acts to obstruct orprevent passage
of something through a surface that is to be protected, e.g. grout, caulk, or
various sealing compounds; sometimes used with polyurethane membranes
to prevent corrosion or oxidation of metal surfaces, chemical impacts on
various materials, or, for example, to• prevent soil-gas-borne radon from
movng through walls, cracks, or joints in a house.
Basal Application: In pesticides, the application of a chemical on plant stems
or tree trunks just above the soil line.
BEN: EPA ’s computer model for analyzing a violator’s economic gain from not
complying with the law.
Benthic Organism (Benthos): A form of aquatic plant or animal life that is
found on r near the bottom of a stream, lake or ocean.
Benthic Region: The bottom layer of a body of water.
Beryllium: Mi airborne metal that can be hazardous to human health when
inhaled. Itis discharged by machine shops, ceramic and propellant plants, and
Beta Partide An elementary particle emitted by radioactive decay, that may
cause skin burns. It is halted by a thin sheet of paper.
Bioaccumulative: Substances that increase in concentration in living organ-
isms (that are very slowly metabolized or excreted) as they breathe con-
taminated air, drink contaminated water, or eat contaminated food. (See:
biological magnification.)
Bioaseay Using living organisms to easure the effect of a substance, factor,
or condition by comparing before-and-after data. Term is often used to mean
cancer b (oassays.
Biochemical Oxygen Demand (BOO): A measure of the amount of oxygen
consumed in the biological processes that break down organic matter in water.
The greater the BOD, the greater the degree of pollution.
Biodegradable: The ability to break down or decompose rapidly under natural
conditions and processes.
Biological Control: In pest control, the use of animals and organisms that eat
or otherwise kill or out-compete pests.
Biological Magnification: Refers to the process whereby certain substances
such as pesticides or heavy metals move up the food chain, work their way
into a nver or lake and are eaten by aquatic organisms such as fish which in
turn are eaten by large birds, animals or humans. The substances become
concentrated in tissues or internal organs as they move up the chain. (See:
biosceumulative.)
Biological Oxidation: The way bacteria and microorganisms feed on and
decompose complex organic materials. Used in self-purification of water
bodies and in activated sludge wastewater treatment.
Biological Treatment: A treatment technology that uses bacteria to consume
waste. This treatment breaks down organic materials.
Biomam: All of the living material in a given area; often refers to vegetation.
Also called “biota”.
Bimnonitoring: 1.The use of living organisms to test the swtability of effluents
for discharge into receiving waters and to test the quality of such waters
downstream from the discharge. 2. Analysis of blood, urine, tissues, etc., to
measure chemical exposure in humans.
Biosphere: The portion of Earth and its atmosphere that can support life.
Bloetabilizen A machine that converts solid waste into compost by grinding
and aeration.
Bieta: (See: biomass.)
Blotedmology: Techniques that use living organisms or parts of organisms to
produce a variety of products (from medicines to industrial enzymes) to
improve plants or animals or to develop microorganisms for specific uses such
as removing tonics from bodies of water, or as pesticides.
Blotic Community: A naturally occurring assemblage of plants and animals
that live in the same environment and are mutually sustaining and inter-
dependent
Black Lung: A disease of the lungs causedby habitual inhalation of coal dust.
Blackwater: Water that contains animal, human, or food wastes.
Bloom: A proliferation of algae and/or higher aquatic plants in a body of water;
often related to pollution, especially when pollutants accelerate growth.
BODS The amount of dissolved oxygen consumed in five days by biological
processes breaking down organic matter.
Bog: A type of wetland that accumulates appreciable peat deposits. Bogs
depend primarily on precipitation for their water source, are usually acidic and
rich in plant residue with a conspicuous mat of living green moss.
Boom: 1. A floatirig device used to contain oil on a body of water. 2. A piece of
equipment used to apply pesticides from ground equipment such as a tractor
or truck. (See: sonic boom.) -
Botanical Pesticide: A pesticide whose active ingredient is a plant produced
chemical such as nicotine or strychnine.
Bottle Bill: Proposed or enacted legislation which requires a returnable
deposit on beer or soda containers and provides for retail store or other
redemption centers 9uchlegislation is designed to discourage use of throw
away containers.
Bottom Land Hardwoods: Forested freshwater wetlands adjacent to rivers in
the southeastern United States. They are especially valuable for wildlife breed-
ing and nesting and habitat areas.
Brackish Water: A mixture of fresh and salt water.
Broadcast Application: In pesticides, the spreading of chemicals over an entire
area.
Bubble: A system under which existing emissions sources can propose alter-
nate means to comply with a set of emissions limitations; under the bubble
concept, sources can control more than required at one emission point where
control costs are relatively low in return for a comparable relaxation of controls
at a second emission point where costs are higher.
Bubble Policy: (See: emissions trading.)
Buffer Strips: Strips of grass or other erosion-resisting vegetation between or
below cultivated strips or fields.
Burial Ground (Graveyard): A disposal site for radioactive waste materials
that uses earth or water as a shield.
By-product: Material, other than the principal product, that is generated as a
consequence of an industrial process.
C
Cadmium (CD): A heavy metal element that accumulates in the environment.
Cancellation: Refers to Section 6(b) of the the Federal Insecticide, Fungicide
and Rodenticide Act (FIFRA) which authorizes cancellation of a pesticide
registration if unreasonable adverse effects to the environment-and public
health develop when a product is used according to widespread and com-
monly recognized practice, or if its labeling or other material required to be
submitted does not comply with FIFRA provisions.
Cap: A layer of day, or other highly impermeable material installed over the
top of a dosed landfill to prevent entry of rainwater and minimize production
of leachate.
Capture Effideacy The fraction of all organic vapors generated by a process
that are directed to an abatement or recovery device.
Carbon Adsorber: An add-on control device which uses activated carbon to
absorb volatile organic compounds from a gas stream. The VOCs are later
recovered from the carbon.
Carbon Dioxide (C02): A colorless, odorless, non-poisonous gas, which
results from fossil fuel combustion and is normally a part of the ambient air.
Carbon Monoxide (CO): A colorless, odorless, poisonous gas produced by
incomplete fossil fuel combustion.
Carboxyhemoglobin: Hemoglobin in which the iron is associated with carbon
monoxide (CO). The affinity of hemoglobin for CO is about 300 times greater
than for oxygen.
Carcinogen: Any substance that can cause or contribute to the production of
cancer.
Carcinogenic Cancer-produdng
Carrying Capacity: 1. In recreation management, the amount of use a recrea-
tion area can sustain without deterioration of its quality. 2. In wildlife manage-
ment, the maximum number of animals an area can support during a given
period of the year.
Cask A thick-walled container (usually lead) used to transport radioactive
material. Also called a coffin.
Catanadramous Fish that swim downstream to spawn.
Catalytic Converter: An air pollution abatement device that removes pollut-
ants from motor vehicle exhaust, either by oxidizing them into carbon dioxide
and water or reducing them to nitrogen and oxygen.
Catalytic Incinerator: A control device which oxidizes volatile organic com-
pounds (VOCs) by using a catalyst to promote the combustion process.
Catalytic incinerators require lower temperatures than conventional thermal
incinerators, with resultant fuel and cost savings.

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Categorical Exclusion: A class of actions which either individually or cumula-
tively would not have a significant effect on the human environment and
therefore would not require preparation of an environmental assessment or
environmental impact statement under the National Environmental Policy Act
(NEPA).
Categorical Pretreatment Standard: A technology-based effluent limitation for
an industrial facility which discharges into a municipal sewer system. An-
alogous in stringency to Best Availability Technology (BAT) for direct dis-
chargers.
Cathodic Protection: A technique to prevent corrosion of a metal surface by
maldng that surface the cathode of an electrochemical cell.
Caustic Soda: Sodium hydroxide, a strong alkaline substance used as the
deaning agent in some detergents.
CBOD5: The amount of dissolved oxygen consumed in 5 days from the
carbonaceous portion of biological processes breaking down in an effluent.
The test methodology is the same as for BOD5, except that nitrogen demand is
suppressed.
Cells: l.In solid waste disposal, holes where waste is dumped, compacted,
and covered with layers of dirt on a daily basis. 2. The smallest structural part
of living matter capable of functioning as an independent unit.
Centrifugal Coliector: A mechanical system using centrifugal force to remove
aerosols from a gas stream or to de-water sludge.
Cesium (Cs): A silver-white, soft ductile element of the alkali metal group that
is the most electropositive element known. Used especially in photoelectric
cells.
Channelization: Straightening and deepening streams so water will move
faster, a flood-reduction or marsh-drainage tactic that can interfere with waste
assimilation capacity and disturb fish and wildlife habitats.
Characteristic Any one of the four categories used in defining hazardous
waste: ignitability, corrosivity, reactivity, and toxicity.
Chemical Oxygen Demand (COD): A measure of the oxygen required to
oxidize all compounds in water, both organic and inorganic.
chemical Treatment: Any one of a variety of technologies that use chemicals
or a variety of chemical processes to treat waste.
Chemosterilant: A chemical that controls pests by preventing reproduction.
chilling Effect: The lowering of the Earth’s temperature because of increased
particles in the air blocking the sun’s rays. (See: greenhouse effect)
Chlorinated Hydrocarbons: These include a class of persistent, broad-
spectrum insecticides, that linger in the environment and accumulate in the
food chain. Among them are DOT, aidrin, dieldrin, heptachlor, chlordane,
lindane, endrin, mirex, hexachloride, and toxaphene. Other examples indude
itE, used as an industrial solvent.
Chlorinated Solvent: An organic solvent containing chlorine atoms, e.g.,
methylene chloride and 1,1,1-trichioromethane which are used in aerosol
spray containers and in traffic paint.
chlorination: The application of chlorine to drinking water, sewage, or in-
dustrial waste to disinfect or to oxidize undesirable compounds.
Chlorinator: A device that adds chlorine, in gas or liquid form, to water or
sewage to kill infectious bacteria.
Chlorine-Contact Chamber. That part of a water treatment plant where
effluent is disinfected by chlorine.
Chiorofluorocarbons (CFCs): A family of inert, nontoxic, and easily liquifled
chemicals used in refrigeration, air conditioning, packaging, insulation, or as
sOlvents and aerosol propeliants. Because CFC5 are not destroyed in the lower
atmosphere they drift into the upper atmosphere where their chlorine com-
ponents destroy ozone.
Chiorosis: Discoloration of normally green plant parts, that can be caused by
disease, lack of nutrients, or various air pollutants.
Chromium: (See: heavy metals.)
Chronic Toxidty The capacity of a substance to cause long-term poisonous
human health effects. (See: acute toxicity.)
Clarification Clearing action that occurs during wastewater treatment when
solids settle out. This is often aided by centrifugal action and chemically
induced coagulation in wastewater.
Clasjfier:A tank in which solids aresettled to the bottom and are subsequently
removed as sludge.
Cleanup:. Actions taken. to deal with a release or threat of release of a
ha rdous substance that could affect humans andlor the environment. The
term deanup” is sometimes used interchangeably with the terms remedial -
action, removal action, response action, or corrective action. -
Gear Cut: A forest management technique that involves harvesting all the
trees in one area at one time. Under certain soil and slope conditions it can
contribute sediment to water pollution.
Cloning: In biotechnology, obtaining a group of genetically identical cells from
a single cell. This term has assumed a more general meaning that includes
making copies of a gene.
Closed-Loop Recycling: Reclaiming or reusing wastewater for non-potable
purposes in an enclosed process.
Coagulation: A clumping of particles in wastewater to settle out impurities. It
is often induced by chemicals such as lime, alum, and iron salts.
Coastal Zone: Lands and waters adjacent to the coast that exert an influence on
the uses of the sea and its ecology, or, inversely, whose uses and ecology are
affected by the sea.
Coefficient of Haze (COH): A measurement of visibility interference in the
atmosphere.
Coliform Index: A rating of the purity of water based on a count of fecal
bacteria.
Coliform Organism: Microorganisms found in the intestinal tract of humans
and animals. Their presence in water indicates fecal pollution and potentially
dangerous bacterial contamination by disease-causing microorganisms.
Combined Sewers: A sewer system that carries both sewage and storm-water
runoff. Normally, its entire flow goes to a waste treatment plant, but during a
heavy storm, the storm water volume may be so great as to cause overflows.
When this happens untreated mixtures of storm water and sewage may flow
into receiving waters. Storm-water runoff may also carry toxic chemicals from
industrial areas or streets into the sewer system.
Combustion: Burning, or rapid oxidation, accompanied by release of energy
in the form of heat and light. A basic cause of air pollution.
Combustion Product: Substance produced during the burning or oxidation of
a material.
Command Post: Facility located at a safe distance upwind from an accident
site, where the on-scene coordinator, responders, and technical representa-
tives can make response decisions, deploy manpower and equipment, main-
tain liaison with news media, and handle communications.
Comment Period: Time provided for the public to review and comment on a
proposed EPA action or rulemaking after it is published in the Federal Regis-
ter.
Comminution: Mechanical shredding or pulverizing of waste. Used in both
solid waste management and wastewater treatment.
Comminuter. A machine that shreds or pulverizes solids to make waste
treatment easier.
Community Relations: The EPA effort to establish two-way communication
with the public to create understanding of EPA programs and related actions,
to assure public input into decision-making processes related to affected
communities, and to make certain that the Agency is aware of and responsive
to public concerns. Specific community relations activities are required in
relation to Superfund remedial actions.
Community Water System: A public water system which serves at least 15
service connections used by year-round residents or regularly serves at least 25
year-round residents.
Compaction: Reduction of the bulk of solid waste by rolling and tamping.
Compliance Coating: A coating whose volatile organic compound content
does not exceed that allowed by regulation.
Compliance Schedule: A negotiated agreement between a pollution source
and a government agency that specifies dates and procedures by which a
source will reduce emissions and, thereby, comply with a regulation.
Compost: A mixture of garbage and degradable trash with soil in which certain
bacteria in the soil break down the garbage and trash into organic fertilizer.
Composting: The natural biological decomposition of organic material in the
presence of air to form a humus-like material. Controlled methods of compost-
ing include mechanical mixing and aerating, ventilating the materials by
dropping them through a vertical series of aerated chambers, or placing the
compost in piles out in the open air and mixing it or turning it periodically.

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Conditional Registration: Under special circumstances, the Federal In-
sectidde, Fungicide, and Rodenticide Act (FIFRA) permits registration of
pesticide products that is “conditional” upon the submission of additional
data. These special circumstances mdude a finding by the EPA Administrator
thata new product or use of an existing pesticide will not significantly increase
the risk of unreasonable adverse effects. A product containing a new (pre-
viously unregistered) active ingredient may be conditionally registered only if
the Administrator finds that such conditional registration is in the public
interest, that a seasonable time for conducting the additional studies has not
elapsed, and the use of the pesticide for the period of conditional registration
will not present an unreasonable risk.
Confined Aquifen An aquifer in which ground water is confined under
pressure which is significantly greater than atmospheric pressure.
Consent Decree: A legal document, approved by a judge, that formalizes an
agreement reached between EPA and potentially responsible parties (PRPs)
through which PRPs will conduct all or part of a cleanup action ata Superfund
site; cease or correct actions or processes that are polluting the environment; or
otherwise comply with regulations where the PRP’s failure to comply caused
EPA to initiate regulatory enforcement actions. The consent decree describes
the actions PRP’s will take and may be subject to a public comment periàd.
Conservation: Avoiding waste of, and renewing when possible, human and
natural resources. The protection, improvement, and use of natural resources
according to principles that will assure their highest economic or social bene-
fits.
Contact Pesticide: A chemical that kills pests when it touches them, rather
than by being eaten (stomach poison). Also, soil that contains the minute
skeletons olcertain algae that scratches and dehydrates waxy-coated insects.
Cnnt. - L n Any physical, chemical, biological, or radiological substance or
matter that has an adverse affect on air, water, or soil.
Contingency Plan: A document set ing out an organized, planned, and coor-
dinated course of action to be followed in case of a fire, explosion, or other
acddent that releases toxic chemicals, hazardous wastes, or radioactive mate-
rials which threaten human health or the environment. (See: National Oil and
Hazardous Substances Contingency Plan.)
Contract Labs: Laboratories under contract to EPA, which analyze samples
taken from wastes, sod, air, and water or carry out research projects.
Contr ’ Long, narrow douds caused when high-flying jet aircraft disturb
the atmosphere.
ContourPlowing Farming methods that break ground following the shape of
the land In a way that discourages erosion.
Control Technique Guidelines (CrG): A series of EPA documents designed
to assist states in defining reasonable available control technology (RAC1) for
major soui of volatile organic compounds (VOC).
Conventional Pollutants Statutorily listed pollutants which are understood
well by scientists. These may be in the form of organic waste, sediment, acid,
bacteria and viruses, nutrients, oil and grease, or heat.
Conventional Systems: Systems that have been traditionally used to collect
municipal wastewater in gravity sewers and convey it to a central primary or
secondary treatment plant prior to discharge to surface waters.
Coolant A liquid or gas used to reduce the heat generated by power produc-
tionin nuclear reactors, electric generators, various industrial and mechanical
processes, and automobile engines.
Cooling Towec A structure that helps remove heat from water used as a
coolant; e.g., in electric power generating plants.
Core: The uranium-containing heart of a nuclear reactor, where energy is
released.
Corrosiem The dissolving and wearing away of metal caused by a chemical
reaction such as between water and the pipes that the water contacts, chem-
icals touching a metal surface, or càntact between two metals.
Couoeire:Achemieal agent that reacts with the surface of a material causing it
to deteriorate or wear away.
Cost-Effective Alternative: An alternative control or corrective method identi-
fied after analysis as being the best available in terms of reliability, per-
manence, and economic considerations. Although costs are one important
consideration, when regulatory and compliance methods are being con-
sidered,.sucls analysis does not require EPA to choose the least expensive
alternative. Forexample, when selecting a method for cleaning upa site on the
Superfund National Priorities List, the Agency balances costs with the long-
term effectiveness of the various methods proposed.
Cost Recovery: A legal process by which potentially responsible parties who
contributed to contamination at a Superfund site can be required to reimburse
the Trust Fund for money spent during any deanup actions by the federal
government.
Coven Vegetation or other material providing protection as ground cover.
Cover Material: Soil used to cover compacted solid waste in a sanitary landifil.
Crawl Space: In some types of houses, which are constructed so that the floor
is raised slightly above the ground, an area beneath the floor which allows
access to utilities and other services. This is in contrast to slab-on-grade or
basement construction houses.
Criteria: Descriptive factors taken into account by EPA in setting standards for
various pollutants. These factors are used to determine limits on allowable
concentration levels, and to limit the number of violations per year. When
issued by EPA, the criteria provide guidance to the states on how to establish
their standards.
Criteria Pollutants: The 1970 amendments to the aero Air Act required EPA
to set National Ambient Air Quality Standards for certain pollutants known to
be hazardous to human health. EPA has identified and set standards to protect
human health and welfare for six pollutants: ozone, carbon monoxide, total
suspended particulates, sulfur dioxide, lead, and nitrogen oxide.The term,
“criteria pollutants” derives from the requirement that EPA must describe the
characteristics and potential health and welfare effects of these pollutants. It is
on the basis of these criteria that standards are set or revised.
Cubic Feet Per Minute (CFM): A measure of the volume of a substance flowing
through air within a fixed period of time. With regard to indoor air, refers to
the amount of air, in cubic feet, thetis exchanged with indoor air in a minute’s
time, or an air exchange rate.
Cultural Eutrophication: Increasing rate at which water bodies “die” by pollu-
tion from human activities.
Cumulative Worldng Level Months (CWLM): The sum of lifetime exposure to
radon working levels expressed in total working level months.
Curie: A quantitative measure of radioactivity equal to 3.7 x 1010 disintegra-
tions per second.
Cutie-Pie: An instrument used to measure radiation levels.
Cyclone Collecton A device that uses centrifugal force to pull large particles
from polluted air.
D
DDT: The first chlorinated hydrocarbon insecticide (chemical name: Dichloro-
Diphsdyl-Trichlommethane). Ithasa half-life of 15 years and can collect in fatty
tissues of certain animals. EPA banned registration and interstate sale of DOT
for virtually all but emergency uses in the United States in 1972 because of its
persistence in the environment and accumulation in the food chain.
Data Call-In: A part of the Office of Pesticide Programs (OPP) process of
developing key required test data, especially on the long-term, chronic effects
of existing pesticides, in advance of scheduled Registration Standard reviews.
Data Call-In is an adjunct of the Registration Standards program intended to
expedite reregistration and involves the “calling in” of data from man-
ufacturers.
Dechlorination: Removal of chlorine from a substance by chemically replacing
it with hydrogen or hydroxide ions in order to detoxify the substances in-
volved.
Decibel (dB): A unit of sound measurement. In general, a sound doubles in
loudness for every increase of ten decibels.
Decomposition: The breakdown of matter by bacteria and fungi. It changes
the chemical makeup and physical appearance of materials.
Degradation: The process by which a chemical is reduced to a less complex
form.
Delegated State: A state (or other governmental entity) which has applied for,
and received authority to administer, within its territory, its state regulatory
program as the federal program required under a particular federal statute. As
used in connection with NPDES, UIC, and PWS programs, the term does not
connote any transfer of federal authority to a state.
Defoliant A herbicide that removes leaves from trees and growing plants.
Delist: Use of the petition process to have a facility’s toxic designation res-
cinded.

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Denitrification: The anaerobic biological reduction of nitrate nitrogen to nit-
rogen gas.
Depletion Curve: In hydraulics, a graphical representation of water depletion
from storage-stream channels, surface soil, and ground water. A depletion
curve can be drawn for base flow, direct runoff, or total flow.
Depressunzation: A condition that occurs when the air pressure inside a
structure is lower that the air pressure outside. Depressurization can occur
when household appliances that consume or exhaust house air, such as
fireplaces or furnaces, are not supplied with enough makeup air. Radon-
containing soil gas may be drawn into a house more rapidly under de-
pressurized conditions.
Dermal Toxicity: The ability of a pesticide or toxic chemical to poison people or
animals by contact with the skin. (See: contact pesticide.)
DES: A synthetic estrogen, diethylstilbestrol is used as a growth stimulant in
food animals. Residues in meat are thought to be carcinogenic.
Desalinization: Removing salt from ocean or brackish water.
Desiccant: A chemical agent that absorbs moisture; some desiccants are cap-
able of dzying out plants or insects, causing death.
Designated Pollutant: An air pollutant which is neither a criteria nor
hazardous pollutant, as described in the Clean Air Act, but for which new
sources performance standards exist. The Clean Air Act does require states to
control these pollutants, which include acid mist, total reduced sulfur (TRS),
and fluorides.
Designer Bugs: Popular term for microbes developed through biotechnology
that can degrade specific toxic chemicals at their source in toxic waste dumps
or in ground water.
Desulfurization: Removal of sulfur from fossil fuels to reduce pollution.
Designated Uses: Those water uses identified in state water quality standards
which must be achieved and maintained as required under the Clean Water
Act. Uses can indude cold water fisheries, public water supply, agriculture,
etc.
Synthetic washing agent that helps to remove dirt and oil. Some
contain compounds which kill useful bacteria and encourage algae growth
when they are in wastewater that reaches receiving waters.
Developen A person, government unit, or company that proposes to build a
hazardous waste treatment, storage, or disposal facility.
Diatomaceous Earth (Diatomite): A chalk-like material (fossilized diatoms)
used to filter out solid waste in waste-water treatment plants, also used as an
active ingredient in some powdered pesticides.
Diazinoiu An insecticide. In 1986, EPA banned its use on open areas such as
sod firms and golf courses because it posed a danger to migratoly birds who
‘gathered on them in large numbers. The ban did not apply to its use in
agriculture, or on lawns of homes and commercial establishments.
Dicofol: A pesticide used on citrus fruits.
Differentiation The process by which single cells grow into particular forms
of specialized tissue, e.g., root, stem, leaf.
Diffused Am A type of aeration that forces oxygen into sewage by pumping
air through perforated pipes inside a holding tank and bubbling it through the
sewage.
Digesten In wastewater treatment, a closed tank; in solid waste conversion, a
unit in which bacterial action is induced and accelerated in order to break
down organic matter and establish the proper carbon to nitrogen ratio.
Digestion: The biochemical decomposition of organic matter, resulting in
partial gasification, liquefaction, and mineralization of pollutants.
‘flfke A low wall that can act as a barrier to prevent a spill from spreading.
Dilution Ratio: The relationship between the volume of water in a stream and
the volume of incoming water. It affects the ability of the stream to assimilate
waste.
Dlnocap: A fungicide used primarily by apple growers to control summer
diseases. EPA, in 1986, proposed restrictions on its use when laboratory tests
found it caused birth defects in rabbits.
Dinoseb: A herbicide that is also used as a fungicide and insecticide. It was
banned by EPAin 1986 because it posed the risk of birth defects and sterility.
Dioxin: Any of a family of compounds known chemically as dibenzo-p-
dioxins. Concern about them arises from their potential toxicity and contanu-
nants in commercial products. Tests on laboratory animals indicate that it is
one of the more toxic man-made chemicals known.
Direct Dischargen A municipal or industrial facility which introduces pollu-
tion through a defined conveyance or system; a point source.
Disinfectant: A chemical or physical process that kills pathogenic organisms
in water. Chlorine is often used to disinfect sewage treatment effluent, water
supplies, wells, and swimming pools.
Dispersant: A chemical agent used to break up concentrations of organic
material such as spilled oil.
Disposal: Final placement or destruction of toxic, radioactive, or other wastes;
surplus or banned pesticides or other chemicals; polluted soils; and drums
containing hazardous materials from removal actions or accidental releases.
Disposal may be accomplished through use of approved secure landfills,
surface impoundments, land farming, deep well injection, ocean dumping, or
incineration.
Dissolved Oxygen (DO): The oxygen freely available in water. Dissolved
oxygen is vital to fish and other aquatic life and for the prevention of odors.
Traditionally, the level of dissolved oxygen has been accepted as the single
most important indicator of a water body’s ability to support desirable aquatic
life. Secondary and advanced waste treatment are generally designed to
protect DO in waste-receiving waters.
Dissolved Solids: Disintegrated organic and inorganic material contained in
water. Excessive amounts make water unfit to drink or use in industrial
processes.
Distillation: The act of purifying liquids through boiling, so that the steam
condenses to a pure liquid and the pollutants remain in a concentrated resi-
due.
DNA: Deoxyribonucleic acid, the molecule in which the genetic information
for most living cells is encoded. Viruses, too, can contain RNA.
DNA Hybridization: Use of a segment of DNA, called a DNA probe, to
identify its complementary DNA; used to detect specific genes. This process
takes advantage of the ability of a single strand of DNA to combine with a
complimentary strand. - ‘ -
Dose: In radiology, the quantity of energy or radiation absorbed.
Dosimeten An instrument that measures exposure to radiation.
Dredging: Removal of mud from the bottom of water bodies using a scooping
machine. This disturbs the ecosystem and causes silting that can kill aquatic
life. Dredging of contaminated muds can expose aquatic life to heavy metals
and other toxics. Dredging activities may be subject to regulation under
Section 404 of the Clean Water Act.
Dump: A site used to dispose of solid wastes without environmental controls.
Dust: Particles light enough to be suspended in air.
Dustfall Jan An open container used to collect large particles from the air for
measurement and analysis.
Dystrophic Lakes: Shallow bodies of water that contain much humus and/or
organic matter, that contain many plants but few fish and are highly acidic.
E
Ecological impact: The effect that a man-made or natural activity has on living
organisms and their non-living (abiotic) environment.
Ecology: The relationship of living things to one another and their environ-
ment, or the study of such relationships.
Economic Poisons: Chemicals used to control pests and to defoliate cash crops
such as cotton.
Ecosphere: The “bio-bubble” that contains life on earth, in surface waters, and
in the air. (See: biosphere.)
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 outfall. Generally refers to wastes discharged into
surface waters.
Effluent Limitation: Restrictions established by a State or EPA on quantitie-
s,rates, and concentrations in wastewater discharges.
Electrodialysis: A process that uses electrical current applied to permeable
membranes to remove minerals from water. Often used to desalinize salty or
brackish water.
Electrostatic Precipitator (ESP): An air pollution control device that removes
particles from a gas stream (smoke) after combustion occurs. The ESP imparts
an electrical charge to the particles, causing them to adhere to metal plates
inside the precipitator. Rapping on the plates causes the particles to fall into a
hopper for disposal.
Eligible Costs: The construction costs for waste-water treatment works upon
which EPA grants are based.
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Emergency (chemical): A situation created by an accidental release or spill of
hazardous chemicals which poses a threat to the safety of workers, residents,
the environment, or property.
Emergency Episode (See air pollution episode)
Eminent Domaui. Government taking—or forced acqwsthon—of private land
for public use, with compensation paid to the landowner.
Emissiom Pollution discharged into the atmosphere from smokestacks, other
vents, and surface areas of commercial or industrial facilities; from residential
chimneys; and from motor vehide, locomotive, or aircraft exhausts. --
Emission Facton The relationship between the amount of pollution produced
and the amount of raw material processed. For example, an emission factor for
a blast furnace making iron would be the number of pounds of particulates per
ton of raw materials.
iim Ofl lnventoiy A hating, by source, of the amount of air pollutants
discharged into the atmosphere of a community-It is used to establish emis-
sian standards.
Emission Standard: The maximum amount of air polluting discharge legally
allowed from a single source, mobile or stationary.
Emissions Trading: EPA policy that allows a plant complex with several
facilities to decrease pollution from some facilities while increasing it from
others, -so long as total results are equal to or better than prevuus limits.
Facilities where this is doneare treated asif they exist in a bubble in which total
emissions are averaged out. Complexes that reduce emissions substantially
may Thank” their “credits or sell them to other industries.
Endangered Species: Animals, birds, fish, plants, or other living organisms
threatened with extinction by man-made or natural changes in their environ-
ment. Requirements for declaring a species endangered are contained in the
Endangered Species Act.
Endangerment Assessment: A study conducted to determine the nature and
extent of contamination at a site on the National Priorities List and the risks
posed to public health or the environment. EPA or the state conduct the study
when a legal action is to be taken to direct potentially responsible parties to
dean up a site or pay for the cleanup. An endangerment assessment supple-
merits a remedial investigation.
Enforcssnent: EPA, state, or local legal actions to obtain compliance with
environmental laws, rules, regulations, or agreements and/or obtain penalties
or criminal sanctions for violations. Enforcement procedures may vary, de-
pending on the specific requirements of different environmental laws and
related implementing regulatory requirements. Under CERCLA, for example,
EPA will seek to require potentially responsible parties to dean up a Super-
fund site, or pay for the cleanup, whereas under the Clean Air Act the agency
may invoke sanctions against cities failing to meet ambient air quality stan-
dards that could prevent certain types of construction or federal funding. In
other situations, if investigations by EPA and state agencies uncover willful
violations, criminal trials and penalties are sought.
Enforcement Decision Document (EDDh A document that provides an ex-
planation to the public of EPA’s selection of the cleanup alternative at enforce-
ment sites on the National Priorities List. Similar to a Record of Decision.
Enrichment: The addition of nutrients (e.g., nitrogen, phosphorus, carbon
compounds) from sewage effluent or agricultural runoff to surface water. This
process greatly increases the growth potential for algae and aquatic plants.
Environment The sum of all external conditions affecting the life, develop-
ment and survival of an organism.
Environmental Assessment A written environmental analysis which is pre-
pared pursuant to the National Environmental Policy Act to determine
whether a federal action would significantly affect the environment and thus
require preparation of a more detailed environmental impact statement.
Environmental Audit 1. An independent assessment of the current status ofa
party’s compliance with applicable environmental requirements. 2. An in-
dependent evaluation of a party’s environmental compliance policies, prac’
tices, and controls.
g y i fln mp t a l Impact Statentent A document reqwred of federal agencies by
the National Environmental Policy Act for major projects or legislative pro-
pussis significantly affecting the environment. A tool for decision making, it
describes the positive and negative effects of the undertaking and lists alterna-
tive actions.
Environmental Response Team: EPA experts located in Edison, N.J., and
Cincinnati, OH, who can provide around-the-clock technical assistance to
EPA regional offices and states during all types of emergencies involving
hazardous waste sites and spills of hazardous substances.
EPA: The U.S. Environmental Protection Agency; established in 19 ’O by
Presidential Executive Order, bringing together parts of various government
agencies involved with the control of pollution.
Epidemic: Widespread outbreak of a disease, or a large number of cases of a
disease in a single community or relatively small area.
Epidemiology: The study of diseases as they affect population, including the
distribution of disease, or other health-related states and events in human
populations, the factors (e.g. age, sex, occupation, economic status) that
influence this distribution, and the application of this study to control health
problems.
Episode (Pollution): An air pollution incident in a given area caused by a
concentration of atmospheric pollution reacting with meteorological con-
ditions that may result in a significant increase in illnesses or deaths. Although
most commonly used in relation to air pollution, the term may also be used in
connection with other kinds of environmental events such as a massive water
pollution situation.
Equivalent Method: Any method of sampling and analyzing for air pollution
which has . been demonstrated to the EPA Administrator’s satisfaction to be,
under specific conditions, an acceptable alternative to the normally used
reference methods.
Equilibrium: In relation to radiation, the state at which the radioactivity of
consecutive elements within a radioactive series is neither increasing nor
decreasing.
Erosion: The wearing away of land surface by wind or water. Erosion occurs
naturally from weather or runoff but can be intensified by land-clearing
practices related to farming, residential or industrial development, road build-
ing, or timber-cutting.
Estuary: Regions of interaction between rivers and nearshore ocean waters,
where tidal action and river flow create a mixing of fresh and salt water. These
areas may indude bays, mouths of rivers, salt marshes, and lagoons. These
brackish water ecosystems shelter and feed marine life, birds, and wildlife.
(See: wetlands.)
Ethylene Dibromide (EDB): A chemical used as an agricultural fumigant and
in certain industrial processes. Extremely toxic and found to be a carcinogen in
laboratory animals, EDB has been banned for most agricultural uses in the
United States.
Eutrophication: The slow aging process during which a lake, estuary, or bay
evolves into a bog or marsh and eventually disappears. During the later stages
of eutrophication the water body is choked by abundant plant life as the result
of increased amounts of nutritive compounds such as nitrogen and phosphor-
us. Human activities can accelerate the process.
Eutrophic Lakes: Shallow, murky bodies of water that have excessive con-
centrations of plant nutrients causing excessive algal production. (See:
dystrophic lakes.)
Evaporation Ponds: Areas where sewage sludge is dumped and allowed to
dry out.
Evapotranspiration: The loss of water from the soil both by evaporation and by
transpiration from the plants growing in the soil.
Exceedance: Violation of environmental protection standards by exceeding
allowable limits or concentration levels.
Exclusionary: Any form of zoning ordinance that tends to exdude specific
dasses of persons or businesses from a particular district or area.
Exempt Solvent Specific organic compounds that are not subject to require-
ments of regulation because they have been deemed by EPA tobe of negligible
photochemical reactivity.
Exempted Aquifec Underground bodies of water defined in the Under-
ground Injection Control program as aquifers that are sources of drinking
water (although they are not being used as such) and that are exempted from
regulations barring underground injection activities.
Exposure: The amount of radiation or pollutant present in an environment
which represents a potential health threat to the living organisms in that
environment.
Extremely Hazardous Substances: Any of 406 chemicals identified by EPA on
the basis of toxicity, and listed under SARA Title Ill. The list is subject to
revision.
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F
Fabric Filter: A cloth device that catches dust particles from industrial enils-
sions.
Feasibility Study: 1. Analysis of the practicability of a proposal; e.g., a descrip-
tion and analysis of the potential cleanup alternatives for a site or alternatives
for a site on the National Priorities List. The feasibility study usually
recommends selection of a cost-effective alternative. It usually starts as soon as
the remedial investigation is underway; together, they are commonly referred
to as the “R1/FS”. The term can apply to a variety of proposed corrective or
regulatory actions. 2. In research, a small-scale investigation of a problem to
ascertain whether or not a proposed research approach is likely to provide
useful data.
Fecal Coliform Bacteria: Bacteria found in the intestinal tracts of mammals.
Their presence in water or sludge is an indicator of pollution and possible
contamination by pathogens.
Feedlot A relatively small, confined area for the controlled feeding of animals
that tends to concentrate large amounts of animal wastes that cannot be
absorbed by the soil and, hence, may be carried to nearby streams or lakes by
rainfall runoff.
Fen: A type of wetland that accumulates peat deposits. Fens are less acidic
than bogs, deriving most of their water from groundwater rich in calcium and
magnesium. (See: wetlands.)
Fermentation: Chemical reactions accompanied by living microbes that are
supplied with nutrients and other critical conditions such as heat, pressure,
and light that are specific to the reaction at hand.
Fertilizer: Materials such as nitrogen and phosphorus that provide nutrients
for plants. Commercially sold fertilizers may contain other chemicals or may
be in the form of processed sewage sludge.
Filling: Depositing dirt and mud or other materials into aquatic areas to create
more dry land, usually for agricultural or commercial development purposes.
Such activities often damage the ecology of the area.
Filtration: A treatment process, under the control of qualified operators, for
removing solid (particulate) matter from water by passing the water through
porous media such as sand or a man-made filter. The process is often used to
remove particles that contain pathogenic organisms.
Finding of No Significant Impact A document prepared by a federal agency
that presents the reasons impact: why a proposed action would not have a
significant impact on the environment and thus would not require preparation
of an Environmental Impact Statement. An FNSI is based on the results of an
environmental assessment.
First Draw: The water that unxnediately comes out when a tap is first opened.
This water is likely to have the highest level of lead contamination from
phinibing materials.
Floc A dump of solids formed in sewage by biological or chemical action.
Flocculation: The process by which dumps of solids in water or sewage are
made to increase in size by biological or chemical action so that they can be
separated from the water.
Floor Sweep: A vapor collection designed to capture vapors which are heavier
than air and which collect along the floor.
Flownieter: A gauge that shows the speed of wastewater moving through a
treatment plant. Also used to measure the speed of liquids moving through
various industrial processes.
Flue Gas: The air coming out of a chimney after combustion in the burner it is
venting. It can indude nitrogen oxides, carbon oxides, water vapor, sulfur
oxides, partides and many chemical pollutants.
Flue Gas Desulfurization: A technology which uses a sorbent, usually lime or
limestone, to remove sulfur dioxide from the gases produced by burning fossil
fuels. Flue gas desulferization is current the state-of-the art technology in use
by major S02 emitter, e.g., power plants.
Fluorides: Gaseous, solid, or dissolved compounds containing fluorine that
result from industrial processes. Excessive amounts in food can lead to fluor
Fluorocarbon (FCs): Any of a number of organic compounds analogous to
hydrocarbons in which one or more hydrogen atoms are replaced by fluorine.
Once used in the United States as a propellant in aerosols, they are now
primarily used in coolants and some industrial processes. FCs containing
chlorine are called chlorofluorocarbons (CFC5). They are believed to be mod-
ifying the ozone layer in the stratosphere, thereby allowing more harmful
solar radiation to reach the Earth’s surface.
Fluorosis: An abnormal condition caused by excessive intake of fluorine,
characterized chiefly by mottling of the teeth.
flume: A natural or man-made channel that diverts water.
Flush: 1. To open a cold-water tap to clear out all the water which may have
been sitting for a long time in the pipes. In new homes, to flush a system
means to send large volumes of water gushing through the unused pipes to
remove loose particles of solder and flux. 2. To force large amounts of water
through liquid to clean out piping or tubing, storage or process tanks.
Fly Ash: Non-combustible residual particles from the combustion process,
carried by flue gas.
Fogging: Applying a pesticide by rapidly heating the liquid chemical so that it
forms very fine droplets that resemble smoke or fog. It may be used to destroy
mosquitoes, black ifies, and similar pests.
Food Chain: A sequence of organisms, each of which uses the next, lower
member of the sequence as a food source.
Formaldehyde: A colorless, pungent, irritating gas, CH2O, used chiefly as a
disinfectant and preservative and in synthesizing other compounds and re-
sins.
Formulation: The substance or mixture of substances which is comprised of all
active and inert ingredients in a pesticide.
Fresh Water: Water that generally contains less than 1,000 milligrams-per-liter
of dissolved solids,
Fuel Economy Standard: The Corporate Average Fuel Economy Standard
(CAFE) which went into effect in 1978. It was meant to enhance the national
fuel conservation effort by slowing fuel consumption through a miles-per-
gallon requirement for motor vehicles.
Fugitive Emissions: Emissions not caught by a capture system.
Fume: Tiny particles trapped in vapor in a gas stream.
Fumigant: A pesticide that is vaporized to kill pests. Used in buildings and
greenhouses.
Functional Equivalent: Term used to describe EPA’s decision-making process
and its relationship to the environmental review conducted under the Nation-
al Environmental Policy Act (NEPA). A review is considered functionally
equivalent when it addresses the si bstantive components of a NEPA review.
Fungi: (Singular, Fungus) Molds, mildews, yeasts, mushrooms, and puff-
balls, a group organisms that lack chlorophyll (i.e., are not photosynthetic)
and which are usually non-mobile, filamentous, and multicellular. Some grow
in the ground, others attach themselves to decaying trees and other plants,
getting their nutrition from decomposing organic matter. Some cause disease,
others stabilize sewage and break down solid wastes in composting.
Fungicide: Pesticides which are used to control, prevent, or destroy fungi.
G
Game Fish: Species like trout, salmon, or bass, caught for sport. Many of them
show more sensitivity to euvironmental change than “rough” fish.
Gamma Radiation: Gamma rays are true rays of energy in contrast to alpha
and beta radiation. The properties are similar to x-rays and other
electromagnetic waves. They are the most penetrating waves of radiant nu-
dear energy but can be blocked by dense materials such as lead..
Gasification: Conversion of solid material such as coal into a gas for use as a
fuel. -
Geiger Counter: An electrical device that detects the presence of certain types
of radioactivity.
Gene: A length of DNA that directs the synthesis of a protein.
Gene Library: A collection of DNA fragments from cells or organisms. So far,
no simple way for sorting the contents of gene libraries has been devised.
However, DNA pieces can be moved into bacterial cells where sorting accord-
ing to gene function becomes feasible.
General Permit A permit applicable to a dass or category of dischargers.
Generator: A facility or mobile source that emits pollutants into the air or
releases hazardous wastes into water or soil.
Genetic Engineering: A process of inserting new genetic information into
existing cells in order to modify any organism for the purpose of changing one
of its characteristics.
Germicide: Any compound that kills disease-causing microorganisms.
Grain Loading: The rate at which partides are emitted from a pollution source.
Measurement is made by the number of grains per cubic foot of gas emitted.
Granular Activated Carbon Treatment A filtering system often used in small
water systems and individual homes, to remove organics. GAC can be highly
effective in removing elevated levels of radon from water.

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Gray Water: The term given to domestic wastewater composed of washwater
from sinks, kitchen sinks, bathroom sinks and tubs, and laundry tubs.
Greenhouse Effect: The warming of the Earth’s atmosphere caused by a
build-up of carbon dioxide orother trace gases; it is believed by many scientists
that this build-up allows light from the sun’s rays to heat the Earth but
prevents a counterbalancing loss of heat.
Grinder Pump: A mechanical device which shreds solids and raises the fluid to
a higher elevation through pressure sewers.
Gross Alpha Partide Activity Total activity due to emission of alpha partides.
Used as the screening measurement for radioactivity generally due to
naturally-occurring radionudides. Activity is commonly measured in picocur-
lea.
Gross Beta Particle Activity Total activity due to emission of beta partides.
Used as the screening measurement for radioactivity from man-made
radionudides since the decay products of fission are beta partide and gamma
ray emitters. Activity is commonly measured in picocunes.
Ground Coven Plants grown to keep soil from eroding.
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.
Because ground water is a major source of drinking water there is growing
concern over areas where leaching agricultural or industrial pollutants or
substances from leaking underground storage tanks are contaminating
— water.
H
Hshitats The place where a population ( e.g., human, animal, plant, micro-
organism) lives and its surroundings, both living and non-living.
Half-Uh 1 The time required for a pollutant to lose half its affect on the
environment. Forexample, the half-life of DDTin the environment is 15 years,
of radium, 1,580 years. 1 The time required for half of the atoms of a radioac-
tive element to undergo decay. 3. The time required for the elimination of one
half a total dose from the body.
Haley- - Any of a group of 5 chemically-related nonmetallic elements that
includes bromine, fluorine, chlorine, iodine, and astatine.
Haimar Bromine-containing compounds with long atmospheric lifetimes
whose breakdown in the slratosphere cause depletion of ozone. Halons are
used In fire-fighting.
-l’— H-Alügh-speed machine that hanuners and cutters to crush, grind
chip, or shred solid wastes.
Hard Water: Alkaline watercontainingdissolved salts that interfere with some
Industrial processes and prevent soap from lathering.
Hazardoua Air Pollutantu Air pollutants which are not covered by ambient
air quality standards but which, as defined in the Gean Air Act, may reason-
ably be expected to cause or contribute to irreversible Illness or death. Such
poliutants include athestos, beryllium. mercury, benzene, coke oven emis-
sions, radionse4id e, and vinyl chloride.
Hazardous Banking Systean The principle screening tool used by EPA to
evakrate ii ks to public health and the environment associated with aban-
dimed or uncontrolled hazardous waste sites. The HRS calculates a score
based on the potential of hazardous substances spreading from the site
through the air. surfa e water, or ground water and on other factors such as
nearby population. This score is the primary factor in deciding if the site
shouldbe on the National Priorities List and, if so, what rankingit should have
compared to other sites on the list.
Ha.zunkrus Substance 1. Any material that poses a threat to human health
andkrr the environment. Typical hazardous substances are tonic, corrosive,
ignitable, explosive, or chemically reactive. 2. Any substance designated by
EPA to be reported if a designated quantity of the substance is spilled in the
wate*n of the United States or if otherwise emitted to the environment.
Rw..A.s Waste By-products of society that can pose a substantial or poten-
tial hazard to human health or the environment when improperly managed.
Pn. m at least one of four characteristics (ignitability, couosivity . reactiv-
ity, or toxicity), or appears on special EPA lists.
Hazard. Analysia: The procedures involved in (1) identifying potential
sources of release of hazardous materials from fixed facilities or transportation
aa*lentai (2) determining the vulnerability of a geographical area to a release
øthazardous n ri.ls ; and (3) comparing hazards to determine which pr-
merit or lesser risks to a community.
P’ lilentlfleatloar Porviding information on which facilities have ex-
z yhazardoussulntanom,whatthosechemicalsare andhowmuchthere
katends facility. lire Prc also providesinformation on how the chemicals
stored and whether they are used at high temperatures.
Heat Island Effect A “dome” of elevated temperatures over an urban area
caused by structural and pavement heat fluxes, and pollutant emissions from
the area below the dome.
Heavy Metals: Metallic elements with high atomic weights, e.g., mercury,
chromium, cadmium, arsenic, and lead. They can damage living things at low
concentrations and tend to accumulate in the food chain.
Heptachlon An insecticide that was banned on some food products in 1975
and all of them 1978. It was allowed for use in seed treatment until in 1983.
More recently it was found in milk and other dairy products in Arkansas and
Missouri, as a result of illegally feeding treated seed to dairy cattle.
Herbicide: A chemical pesticide designed to control or destroy plants, weeds,
or grasses.
Herbivore: An animal that feeds on plants.
Heterotrophic Organisms: Consumers such as humans and animals, and
decomposers—chiefly bacteria and fungi—that are dependent on organic
matter for food.
High-Density Polyethylene: A material that produces toxic fumes when
burned. Used to make plastic bottles and other products.
High-Level Radioactive Waste (HLW): Waste generated in the fuel of a nu-
dear reactor, found at nudear reactors or nudear fuel reprocessing plants. It is
a serious threat to anyone who comes near the wastes without shielding. (See
Low-Level Radioactive Waste).
Holding Pond: A pond or reservoir, usually made of earth, built to store
polluted runoff.
Hood Capture Efficiency The emissions from a process which are captured by
hood and directed into the control device, expressed as a percent of all
emissions.
Host: 1. In genetics, the organism, typically a bacterium, into which a gene
from another organism is transplanted. 2. In medicine, an animal infected by
or parasitized by another organism.
Humun Decomposed organic material.
Hybridi A cell or organism resulting from a cross between two unlike plant or
animal cells or organisms.
Hybridoma: A hybrid cell that produces monoclonal antibodies in large quan-
tities.
Hydrocarbons (HC): Chemical compounds that consist entirely of carbon and
hydrogen.
Hydrogen Sulfide (HS): Gas emitted during organic decomposition. Also a
byproduct of oil refining and burning. It smells like rotten eggs and, in heavy
concentration, can cause illness.
Hydrugeology The geology of ground water, with particular emphasis on the
chemistry and movement of water.
Hydrology The science dealing with the properties,distribution, and circula-
tion of water.
I
Ignitable Capable of burning or causing a fire.
Impoundment A body of water or sludge confined by a dam, dike, floodgate,
or other barrier.
Immediately Dangerous to Life and Health (IDLH): The maximum level to
which a healthy individual can be exposed to a chemical for 30 minutes and
escape without suffering irreversible health effects or impairing symptons.
Used as a “level of concern.” (See: level of concern.)
In VItro: 1. In glass”; a test-tube culture. 2. Any laboratory test using living
cells taken from an organism.
In Vivo: In the living body of a plant or animal. In vivo tests are those
laboratory experiments carried out on whole animals or human volunteers.
Incineratioe 1. Burning of certain types of solid, liquid or gaseous materials.
2. A treatment technology involving destruction of waste by controlled burn-
ingat high temperatures, e.g., burning sludge to remove the water and reduce
the remaining residues to a safe, non-burnable ash which can be disposed of
safely on land, in some waters or in underground locations.
Incineration at Sea: Disposal of waste by burning at sea on specially-designed
incinerator ships.
Incinerator: A furnace fur burning wastes under controlled conditions.
Indicator: In biology, an organism, species, or community whose characteris-
tics show the presence of specific environmental conditions.

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Indirect Discharge: Introduction of pollutants from a non-domestic source
into a publicly owned waste treatment system. Indirect dischargers can be
commercial or industrial facilities whose wastes go into the local sewers.
Indoor Air The breathing air inside a habitable structure or conveyance.
Indoor Air Pollution: Chemical, physical, or biological contaminants in indoor
air.
Indoor Climate: Temperature, humidity, lighting and noise levels in a habit-
able structure or conveyance. Indoor climate can affect indoor air pollution.
Inert Ingredient: Pesticide components such as solvents, carriers, and sur-
factants that are not active against target pests. Not all inert ingredients are
innocuous.
Inertial Separator. A device that uses centrifugal force to separate waste
particles.
Infiltration: 1. The penetration of water through the ground surface into
sub-surface soil or the penetration of water from the soil into sewer or other
pipes through defective joints, connections, or manhole walls. 2. A land
application technique where large volumes of waste water are applied to land,
allowed to penetrate the surface and percolate through the underlying soil.
(See: percolation)
Inflow: Entry of extraneous rain water into a sewer system from sources other
than infiltration, such as basement drains, manholes, storm drains, and street
washing.
Influenti Water, wastewater, or other liquid flowing into a reservoir, basin, or
treatment plant.
Infoanation File: In the Superfund program, a file that contains accurate,
up’to-.date documents on a Superfund site. The file is usually located in a
public building such as a school, library, or city hail that is convenient for local
residents.
Injection Well: A well into which fluids are injected for purposes such as
waste disposal, improving the recovery of crude oil, or solution mining.
Injection Zone: A geological formation, group of formations, or part of a
formation receiving fluids through a well.
Inoculunsj 1. Bacterium placed in compost to start biological action. 2. A
medium containing organisms which is introduced into cultures or living
organisms,
Inosganic Chemicals: Chemical substances of mineral origin, not of basically
carbon structure.
Insecticide: A pesticide compound specifically used to kill or control the
growth of insects.
Inspection and Maintenance (J/M): 1. Activities to assure proper emissions-
related operation of mobile sources of air pollutants, particularly automobile
emissions controls. 2. Also applies to to wastewater treatment plants and
other anti-pollution facilities and processes.
Instream Use: Water use taking place within a stream channel, e.g., hydro-
electric power generation, navigation, water-quality improvement, fish pro-
pagation, recreation.
Integrated Pest Management (1PM): A mixture of pesticide and non-pesticide
methods to control pests.
Interceptor Sewers: Large sewer lines that, in a combined system, control the
flow of the sewage to the treatment plant. In a storm, they allow some of the
sewage to flow directly into a receiving stream, thus preventing an overload by
a sudden surge of water into the sewers. They are also used in separate
systems to collect the flows from main and trunk sewers and carry them to
treatment points.
Interim (Permit) Status: Period during which treatment, storage and disposal
facilities coming under RCRA in 1980 are temporarily permitted to operate
while awaiting denial or issuance of a permanent permit. Permits issued under
these circumstances are usually called “Part A” or “Part B” pennits.
Interstate Carrier Water Supply: A source of water for drinking and sanitary
use on planes, buses, trains, and ships operating mmore than one state. These
sources are federally regulated.
Interstate Waters: Waters that flow across or form part of state or international
boundaries, e.g., the Great Lakes, the Mississippi River, or coastal waters.
Interstitial Monitoring: The continuous survefflance of the space between the
walls of an underground storage tank.
Inventory TSCA inventory of chemicals produced pursuant to Section 8 (b) of
the Toxic Substances Control Act.
Inversion: An atmospheric condition caused by a layer of warm air preventing
the rise of cooling air trapped beneath it. This prevents the rise of pollutants
that might otherwise be dispersed and can cause an air pollution episode.
Ion: An electrically charged atom or group of atoms which can be drawn from
waste water during the electrodialysis process.
Ion Exchange Treatment: A common water softening method often found on a
large scale at water purification plants that remove some organics and radium
by adding calcium oxide or calcium hydroxide to increase the ph to a level
where the metals will precipitate out.
Ionization Chamber: A device that measures the intensity of ionizing radia-
tion.
Ionizing Radiation: Radiation that can remove electrons from atoms, i.e.,
alpha, beta, and gamma radiation.
Irradiated Food: Food that has been subject to brief radioactivity, usually by
gamma rays, to kill insects, bacteria, and mold, and preserve it without
refrigeration or freezing.
Irradiation: Exposure to radiation of wavelengths shorter than those of visible
light (gamma, x-ray, or ultraviolet), for medical purposes, the destruction of
bacteria in milk or other foodstuffs, or for inducing polymerization of monom-
ers or vulcanization of rubber.
Irrigation: Technique for applying water or wastewater to land areas to supply
the water and nutrient needs of plants.
Isotope: A variation of an element that has the same atomic number but a
different weight because of its neutrons. Various isotopes of the same element
may have different radioactive behaviors.
K
Kinetic Rate Coefficient: A number that describes the rate at which a water
constituent such as a biochemical oxygen demand or dissolved oxygen in-
creases or decreases.
L
Lagoon: (1) A shallow pond where sunlight, bacterial action, and oxygen work
to purify wastewater; also used to storage of wastewaters or spent nuclear fuel
rods. (2) Shallow body of water, often separated from the sea by coral reefs or
sandbars.
Land Application: Discharge of wastewater onto the ground for treatment or
reuse. (See: irrigation.)
Land Farming (of waste): A disposal process in which hazardous waste
deposited on or in the soil is naturally degraded by microbes.
Lindfills: 1. Sanitary landfills are land disposal sites for non-hazardous solid
wastes at which the waste is spread in layers, compacted to the smallest
practical volume, and cover material applied at the end of each operating day.
2. Secure chemical landfills are disposal sites for hazardous waste. They are
selected and designed to minimize the chance of release of hazardous sub-
stances into the environment.
Lateral Sewers: Pipes that run under city streets and receive the sewage from
homes and businesses.
LC5O/Lethal Concentration: Median level concentration, a standard measure
of toxicity. It tells how much of a substance is needed to kill half of a group of
experimental organisms at a specific time of observation. (See LD5O.)
Leachate: A liquid that results from water collecting contaminants as it trickles
through wastes, agricultural pesticides or fertilizers. Leaching may occur in
farming areas, feedlots, and landfills, and may result in hazardous substances
entering surface water, ground water, or soil.
Leachate Collection System: A system that gathers leachate and pumps it to
the surface for treatment.
Leaching: The process by which soluble constituents are dissolved and carried
down through the soil by a percolating fluid. (See: leachate.)
Lead (PE): A heavy metal that is hazardous to health if breathed or swallowed.
Its use in gasoline, paints, and plumbing compounds has been sharply res-
tricted or eliminated by federal laws and regulations. (See: heavy metals.)
Leaded Gasoline: Gasoline to which lead has been added to raise the octane
level.
LD 50/ Lethal Dose: The dose of a toxicant that will kill 50 percent of the test
organisms within a designated period of time. The lower the LD 50. the more
toxic the compound.
LD 0: The highest concentration of a toxic substance at which none of the test
organisms die.
LD LO: The lowest concentration and dosage of a toxic substance which kills
test organisms.
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Level of Concern (LOC): The concentration in air of an extremely hazardous
substance above which there may be serious immediate health effects to
anyone exposed to it for short periods of time.
Lift: ma sanitary landfill, a compacted layer of solid waste and the top layer of
cover material.
Lifting Statiorc (See: pumping station.)
Limestone Scrubbinç Process in which sulfur gases moving towards a
smokestack are passed through a limestone and water solution to remove
sulfur before it reaches the atmosphere.
Limiting Factor: A condition, whose absence, or excessive concentration, is
incompatible with the needs or tolerance of a species or population and which
may have a negative influence on their ability to grow or even survive.
Umnn logy The study of the physical, chemical, meteorological, and biologi-
cal asp cts of fresh water.
Liner: 1. A relatively impermeable barrier designed to prevent leachate from
leaking from a landfill. Liner materials indude plastic and dense day. 2. An
insert or sleeve for sewer pipes to prevent leakage or infiltration.
Lipid Solubility The maximum concentration of a chemical that will dissolve
in fatty substances; lipid soluble substances are insoluble in water. If a sub-
stance is lipid soluble it will very selectively disperse through the environment
via living tissue.
Liquefaction: Changing a solid into a liquid.
List: Shorthand term for EPA list if violating facilities or list of firms debarred
from obtaining government contracts because they violated certain sections of
the Clean Air or Clean Water Acts. The list is maintained by The Office of
Enforcement and Compliance Monitoring.
Listed Waste: Wastes listed as hazardous under RCRA but which have not
been subjected to the Toxic Cbaracteristks Listing Process because the dan-
gem they present are considered self-evident.
Local Emergency Planning Conunittee (LEPC): A committee appointed by
the state emergency response commission, as required by SARA Title ifi. to
formulate a comprehensive emergency plan for its jurisdiction.
Lower Explosive Limit (La): The concentration of a compound in air belo r
which a flame will not propagate if the mixture is ignited.
Lowest Adiievable Emission Rate: Under the Clean Air Act, this is the rate of
emissions which reflects (a) the most stringent emission limitation which is
contained in the implementation plan of any state for such source unless the
owner or operator of the proposed source demonstrates such limitations are
not achievable; or (b) the most stringent emissions limitation achieved in
practice, which ever is more stringent. Application of this term does not
permit a proposed new or modified source to emit pollutants in excess of
existing new source standards.
Low-Level Radioactive Waste (U.RW): Wastes less hazardous than most of
those generated by a nudear reactor. Usually generated by hospitals, research
laboratories, and certain industries. The Department of Energy, Nudear Reg-
ulatnryConunission, and EPA share responsibilities for managing them. (See:
high4evel radsoactive wastes.)
M
Marine Sanitation Device: Any equipment installed on board a vessel to
receive, retain, treat, or discharge sewage and any process to treat such
sewage.
Major Modification: This term is used to define modifications with respect to
Preveatran of Significant Detenorahon and New Source Review under the
Clean Air Act and refers to modifications to major stationary sources of
emissions and provides significant pollutant increase levels below which a
modification is not considered major.
Major Stationary Sourees: Term used to determine to applicability of Preven-
tion of Significant Deterioration and new source regulations. In a nonattain-
merit area, any stationary pollutant source that has a potential to emit more
than 100 tons per year is considered a major stationary source. In PSD areas the
iflevel may be either 100 or 250 tons, depending upon the type of source.
Manufacturers Formulation: A list of substances or component parts as de-
scribed by the maker of a coating, pesticide or other product containing
chemicals or other substances.
Mamhi A type of wetland that does not accumulate appreciable peat deposits
and is dominated by herbaceous vegetation. Marshes may be either fresh or
saltwater and tidal or non-tidal. (See: wetlands.)
Matabolite: Any substance produced in orby biological processes and derived
from a pesticide.
Material Safety Data Sheet (MSDS): A compilation of information required
under the OSI-lA Communication Standard on the identity of hazardous
chemicals, health, and physical hazards, exposure limits, and precautions.
Section 311 of SARA requires facilities to submit MSDSs under certain circum-
stances.
Maximum Contaminant Level: The maximum permissible level of a contami-
nant in water delivered to any user of a public water system. MCLs are
enforceable standards.
Mechanical Aeration: Use of mechanical energy to inject air into water to
cause a waste stream to absorb oxygen.
Mechanical Turbulence: Random irregularities of fluid motion in air caused
by buildings or mechanical, non-thermal, processes.
Mediar Specific environments—air, water, soil—which are the subject of
regulatory concern and activities.
Mercury: A heavy metal that can accumulate in the enivornment and is highly
toxic if breathed or swallowed. (See: heavy metals.)
Methane: A colorless, nonpoisonous, flammable gas created by anaerobic
decomposition of organic compounds.
Method 18: An EPA test method which uses gas chromatographic techniques
to measure the concentration of individual volatile organic compounds in a gas
stream,
Method 24: An EPA reference method to determine density, water content
and total volatile content (water and VOC) of coatings.
Method 25: An EPA reference method to determine the VOC concentration in
a gas stream.
Million-gallons Per Day (MCD): A measure of water flow.
Microbes: Microscopic organisms such as algae, animals, viruses, bacteria,
fungus, and protozoa, some of which cause diseases. (See: microorganism.)
Microbial Pesticide: A microorganism that is used to control a pest. They are
of low toxicity to man.
Microorganism: Living.orgarusms so small that individually they can usually
only be seen through a microscope.
Mist: Liquid partides measuring 500 to 40 microns, that are formed by con-
densation of vapor. By comparison, “fog” particles are smaller than 40 micro-
ns.
Mitigation: Measures taken to reduce adverse impacts on the environment.
Mixed Liquor: A mixture of activated sludge and water containing organic
matter undergoing activated sludge treatment in an aeration tank.
Mobile Source: A moving producer of air pollution, mainly forms of transpor-
tation such as cars, trucks, motorcydes, airplanes.
Modeling: An investigative technique using a mathematical or physical repre-
sentation of a system or theory that accounts for all or some its known
properties. Models are often used to test the effect of changes of system
components on the overall performance of the system.
MOdel Plant: A description of a typical but theoretical plant used for develop-
ing economic, environmental impact and energy impact analyses as support
for regulations or regulatory guidelines. It is an imaginary plant, with features
of existing or future plants used to estimate the cost of incorporating air
pollution control technology as the first step in exploring the economic impact
of a potential NSPS.
Monitoring: Periodic or continuous surveillance or testing to determine the
level of compliance with statutory requirements and/or pollutant levels in
various media or in humans, animals, and other living things.
Monitoring Wells: Wells drilled at a hazardous waste management facility or
Superfund site to collect ground-water samples for the purpose of physical,
chemical, or biological analysis to determine the amounts, types, and distribu-
tion of contaminants in the ground water beneath the site.
Monoclonal Antibodies: (Also called MASs and MCAs) Molecules of living
organisms that selectively find and attach to other molecules to which their
structure conforms exactly. This could also apply to equivalent activity by
chemical molecules.
Muck Soils: Earth made from decaying plant materials.
MU ICIn A layer of material (wood chips, straw, leaves, etc.) placed around
plants to hold moisture, prevent weed growth, protect the plants, and enrich
the soil.
Multiple Use: Use of land for more than one purpose; i.e., gra.zing of livestock,
wildlife production, recreation, watershed, and timber production. Could also
apply to use of bodies of water for recreational purposes, fishing, and water
supply.
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Mutagen: Any substance that can cause a change in genetic material.
Mutate: To bring about a change in the genetic constitution of a cell by altering
its DNA. In turn, “mutagenesis” is any process by which cells are mutated
National Ambient Air Quality Standards (NAAQS): Air quality standards
established by EPA that apply to outside air throughout the country. (See:
criteria pollutants, state implementation plans, emissions trading.)
National Emissions Standards For Hazardous Air Pollutants (NESHAPS):
Emissions standards set by EPA for an air pollutant not covered by NAAQS
that may cause an increase in deaths or in serious, irreversible, or incapacitat-
ing illness. Primary standards are designed to protect human health, secon-
dary standards to protect public welfare.
National Oil and Hazardous Substances Contingency Plan (NOHSCP/NCP):
The federal regulation that guides determination of the sites to be corrected
under the Superfund program and the program to prevent or control spills
into surface waters or other portions of the environment.
National Pollutant Dischai ge Elimination System (NPDES): A provision of
the Clean Water Act which prohibits discharge of pollutants into waters of the
United States unless a special permit is issued by EPA, a state, or (where
delegated) a tribal government on an Indian reservation.
National Priorities List (NPL): EPA’s list of the most serious uncontrolled or
abandoned hazardous waste sites identified for possible long-term remedial
action under Superfund. A site must be on the NPL to receive money from the
Trust Fund for remedial action. The list is based primarily on the score a site
receives from the Hazard Ranking System. EPA is required to update the NFL
at least once a year.
National Response Center The federal operations center that receives noti-
fications of all releases of oil and hazardous substances into the environment.
The Center, open 24 hours a day, is operated by the U.S. Coast Guard, which
evaluates all reports and notifies the appropriate agency.
National Response Team (NKT): Representatives of 13 federal agencies that,
as a team, coordinate federal responses to nationally significant incidents of
pollution and provide advice and technical assistance to the responding agen-
cy(ies) before and during a response action.
Natural Gas: A natural fuel containing primarily methane and ethane that
occurs in certain geologic formations.
Natural Selection: The process of survival of the fittest, by which organisms
that adapt to their environment survive and those that do not disappear.
Navigable Waters: Traditionally, waters sufficiently deep and wide for
navigation by all, or specified sizes of vessels; such waters in the United States
come under federal jurisdiction and are included in certain provisions of the
Clean Water Act.
Necrosis: Death of plant or animal cells. In plants, necrosis can discolor areas
on the plant or kill it entirely.
Nematocide: A chemical agent which is destructive to nematodes (round
worms or threadworms.)
Neutralization: Decreasing the acidity or alkalinity of a substance by adding to
it alkaline or acidic materials respectively.
New Source: Any stationary source which is built or modified after publication
of final or proposed regulations that prescribe a standard of performance
which is intended to apply to that type of emission source.
New Source Performance Standards (NSPS): Uniform national EPA air emis-
sion and water effluent standards which limit the amount of pollution allowed
from new sources or from existing sources that have been modified.
Nitrate: A compound containing nitrogen which 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 cows.
Nitric Oxide (NO): A gas formed by combustion under high temperature and
high pressure in an internal combustion engine. It changes into nitrogen
dioxide in the ambient air and contributes to photochemical smog.
Nitrification: The process whereby ammonia in wastewater is oxidized to
nitrite and then to nitrate by bacterial or chemical reactions.
Nitrilotriacetic Acid (NTA): A compound being used to replace phosphates in
detergents:
Nitrite: 1. An intermediate in the process of nitrification. 2. Nitrous oxide salts
used in food preservation
Nitrogen Dioxide (N02): The result of nitric oxide combining with oxygen in
the atmosphere. A major component of photochemical smog.
Nitrogenous Wastes: Animal or vegetable residues that contain significant
amounts of nitrogen.
Nitrogen Oxide (NOx): Product of combustion from transportation and sta-
tionary sources and major a contributor to the formation of ozone in the
troposphere and acid deposition.
Non-Attainment Area: Geographic area which does not meet one or more of
the National Ambient Air Quality Standards for the criteria pollutants desig-
nated in the Clean Air Act.
Non-Community Water System: A public water system that is not a communi-
ty water system, e.g., the water supply at a camp site or national park.
Non-Conventional Pollutant: Any pollutant which is not a statutorily listed or
which is poorly understood by the scientific community.
Non-ionizing Electromagnetic Radiation: 1. Radiation that does not change
the structure of atoms but does heat tissue and may cause harmful biological
effects. 2. Microwaves, radio waves, and low-frequency electromagnetic fields
from high-voltage transmission lines.
Non-Point Source: Pollution sources which are diffuse and do not have a
single point of origin or are not introduced into a receiving stream from a
specific outlet. The pollutants are generally carried off the land by stormwater
runoff. The commonly used categories for non-point sources are: agriculture,
forestry, urban, mining, construction, dams and channels, land disposal, and
saltwater intrusion.
Nuclear Power Plant: A facility that converts atomic energy into usable power;
heat produced by a reactor makes steam to drive turbines which produce
electricity.
Nudear Winter Prediction by some scientists that smoke and debris rising
from massive fires resulting from a nuclear war could enter the atmosphere
and block out sunlight for weeks or months. The scientists making this
prediction project a cooling of the earth’s surface, and changes in climate
which could, for example, negatively effect world agricultural and weather
patterns.
Nutrient: Any substance assimilated by living things that promotes growth.
The term is generally applied to nitrogen and phosphorus in wastewater, but
is also applied to other essential and trace elements.
0
Off-Site Facility: hazardous waste treatment, storage or disposal area that
is located at a place away from the generating site.
Oil Spill: An accidental or intentional discharge of oil which reaches bodies of
water. Can be controlled by chemical dispersion, combustion, mechanical
containment, andlor adsorption.
Oil Fingerprinting: A method that identifies sources of oil and allows spills to
be traced back to their source.
Oligotrophic Lakes: Deep clear lakes with low nutrient supplies. They contain
little organic matter and have a high dissolved-oxygen level.
Oncogenic: A substance that causes tumors, whether benign or malignant.
On-Scene Coordinator (OSC): The predesignated EPA, Coast Guard, or De-
partment of Defense official who coordinates and directs Superfund removal
actions or Clean Water Act oil-or hazardous-spill corrective actions.
On-Site Facility: A hazardous waste treatment, storage or disposal area that is
located on the generating site.
Opacity: The amount of light obscured by particulate pollution in the air; clear
window glass has a zero opacity, a brick wall has 100 percent opacity. Opacity
is used as an indicator of changes in performance of particulate matter pollu-
tion control systems.
Open Burning: Uncontrolled fires in an open dump.
Open Dump: An uncovered site used for disposal of waste without environ-
mental controls. (See: dump.)
Operable Unit: Term for each of a number of separate activities undertaken as
part of a Superfund site cleanup. A typical operable unit would be removing
drums and tanks from the surface of a site.
Operation And Maintenance: 1. Activities conducted at a site after a Super-
fund site action is completed to ensure that the action is effective and operating
properly. 2. Actions taken after construction to assure that facilities con-
structed to treat waste water will be properly operated, maintained,and man-
aged to achieve efficiency levels and prescribed effluent limitations in an
optimum manner.
Organic: 1. Referring to or derived from living organisms. 2. In chemistry, any
compound containing carbon.
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Organic OsemIcals/Compounds: Animal or plant-produced substances con-
taining mainly carbon, hydrogen, and oxygen.
Organic Mafter: Carbonaceous waste contained in plant or animal matter and
originating from domestic or industrial sources.
Organism: Any living thing.
Ospnophosphates Pesticide chemicals that contain phosphorus; used to
control insects. They are short-lived, but some can be toxic when first applied.
Organotinu Chemical compounds used in anti-foulant paints to protect the
hulls of boats and ships. buoys, and dock pilings from marine organisms such
as barnacles.
Osmoske The tendency of a fluid to pass through a permeable membrane such
as the wall of a living cell into a less concentrated solution so as to equalize the
concentrations on both sides of the membrane.
Outfall: The place where an effluent is discharged into receiving waters.
Overburden: The rock and soil cleared away before mining.
Overfire Air: Air forced into the top of an incinerator or boiler to fan the
flames.
Overland Flow: A land application technique that deanses waste water by
allowing it to flow over a sloped surface. As the water flows over the surface,
the contaminants are removed and the water is collected at the bottom of the
slope for reuse.
Overturn: The period of mixing (turnover), by top to bottom circulation, of
previously stratified water masses. This phenomenon may occur in spring
and/or fall, or after storms. It result$ ina uniformity of chemical and physical
1 wportics of the water at all depths.
Oxidant: A substance containing oxygen that reacts chemically in air to pro-
duce a new substance. The primaiy ingredient of photochemical smog.
OxidatIon: 1. The addition of oxygen which breaks down organic waste or
chemicals such as cyanides, phenols, and organic sulfur compounds in sew-
age by bacterial and chemical means. 2. Oxygen combining with other ele-
merits. 3. The process in chemistry whereby electrons are removed from a
molecule.
Oxidation Pond: A man-made lake or body of water in which waste is con-
sumed by bacteria. it is used most frequently with other waste-treatment
processes. An oxidation pond is basically the same as a sewage lagoon.
Oxygeuated Solvent: An organic solvent containing oxygen as part of the
molecular structure. Alcohols and ketones are oxygenated compounds often
used as paint solvents.
O.n ’. . A device that adds ozone to water.
Ozone (0* Found in two layers of the atmosphere, the stratosphere and the
troposphere. In the stratosphere (the atmospheric layer beginning 7 to 10
miles above the earth’s surface) ozone is a form of oxygen found naturally
whidri provides a protective layer shielding the earth from ultraviolet radia-
thin’s harmful health effects on humans and the environment.ln the tropos-
pitere (the layerextending up7to 10 miles from the earth’s surface), ozone isa
ñ iarn ai oxidant and major component of photochemical smog. Ozone can
seriously affect the human respiratory system and is one of the most prevalent
and widespread of all the criteria pollutants for which the Qean Air Act
required EPA to set standards. Ozone in the troposphere is produced through
complex chemical reactions of nitrogen oxides, which are among the primary
pollutants emitted by combustion sources; hydrocarbons, released into the
atmosphere through the combustion, handling and processing of petroleum
products; and samlight.
Ozone Depletion: Destruction of thestratospheric ozone layer which shields
t im earth from ultraviolet radiation harmful to biological life. This destruction
of ntone is caused by the breakdown of certain chlorine and/or-bromine
containing compounds (chlorofluorocarbons or halons) which break down
when they reach the stratosphere and catalytically destroy ozone molecules.
p
Lathed Tower: A pollution control device that forces dirty air through a tower
packed with crushed rock or wood chips while liquid is sprayed over the
packing material. The pollutants in the air stream either dissolve or chemically
react with the liquid.
Pandemic: Widespread throughout an area, nation or the world.
Part A Permit, Part 0 Permit (See Interim Permit Status.)
Paraquab A standard herbicide used to kill various types of crops, including
Partleulates: Fine liquid or solid particles such as dust, smoke, mist, fumes, or
g, found in air or emissions.
Particulate Loading The mass of particulates per unit volume of air or water.
Pathogenic Capable of causing disease.
Pathogens: Microorganisms that can cause disease in other organisms or in
humans, animals and plants. They may be bacteria, viruses, or parasites and
are found in sewage, in runoff from animal farms or rural areas populated with
domestic and/or wild animals, and in water used for swimming. Fish and
shellfish contaminated by pathogens, or the contaminated water itself, can
cause serious illnesses.
PCBs: A group of toxic, persistent chemicals (polychlorinatedbiphenyls) used
in transformers and capacitators for insulating purposes and in gas pipeline
systems as a lubricant. Further sale of new use was banned by law in 1979.
Percolation: The movement of water downward and radially through the
sub-surface soil layers, usually continuing downward to the ground water.
Permeability: The rate at which liquids pass through soil or other materials in a
specified direction.
Permit: An authorization, license, or equivalent control document issued by
EPA or an approved state agency to implement the requirements of an en-
vironmental regulation; e.g., a permit to operate a wastewater treatment plant
or to operate a facility that may generate harmful emissions.
Persistence: Refers to the length of time a compound, once introduced into the
environment, stays there. A compound may persist for less than a second or
indefinitely.
Persistent Pesticides: Pesticides that do not break down chemically or break
down very slowly and that remain in the environment after a growing season.
Pest An insect, rodent, nematode, fungus, weed or other form of terrestrial or
aquatic plant or animal life or virus, bacterial or microorganism that is in-
jurious to health or the environment.
Pesticide: Substance or mixture of substances intended for preventing, de-
stroying, repelling, or mitigating any pest. Also, any substance or mixture of
substances intended for use as a plant regulator, defoliant, or desiccant.
Pesticides can accumulate in the food chain and/or contaminate the environ-
ment if misused.
Pesticide Tolerance: The amount of pesticide residue allowed by law to remain
in or on a harvested crop. By using various safety factors, EPA sets these levels
well below the point where the chemicals might be harmful to consumers.
pit A measure of the acidity or alkalinity of a liquid or solid material.
Phenols: Organic compounds that are by products of petroleum refining,
tanning, and textile, dye, and resin manufacturing. Low concentrations cause
taste and odor problems in water; higher concentrations can kill aquatic life
and humans.
Pheromone: Hormonal chemical produced by female of a species to attract a
mate.
Phosphates: Certain chemical compounds containing phosphorus.
Phosphorus: An essential chemical food element that can contribute to the
eutrophication of lakes and other water bodies. Increased phosphorus levels
result from discharge of phosphorus-containing materials into surface waters.
Photochemical Oxidants: Air pollutants formed by the action of sunlight on
oxides of nitrogen and hydrocarbons.
Photochemical Smoç Air pollution caused by chemical reactions of various
pollutants emitted from different sources.
Photosynthesis: The manufacture by plants of carbohydrates and oxygen from
carbon dioxide and water in the presence of chlorophyll, using sunlight as an
energy source. -
Physical and Chemical Treatment Processes generally used in large-scale
waste-water treatment facilities. Physical processes may involve air-stripping
or filtration. Chemical treatment includes coagulation, chlorination, or ozone
addition. The term can also refer to treatment processes, treatment of toxic
materials in surface waters and ground waters, oil spills, and some methods of
dealing with hazardous materials on or in the ground.
Pbytoplanktorn That portion of the plankton community comprised of tiny
plants, e.g., algae, diatoms.
Phytotoxic Something that harms plants.
Picocurie: Measurement of radioactivity. A picocurie is one million millionth,
or a trillionth, of a curie, and represents about 2.2 radioactive particle disinte-
grations per minute.
Picocuries Per Liter pCi/L): A unit of measure used for expressing levels of
radon gas. (See picocurie.)

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Pig: A container, usually lead, used to ship or store radioactive materials.
Pile: 1. The fuel element in a nudear reactor. 2. A heap of waste.
Plankton: Tiny plants and animals that live in water.
Plasmid: A circular piece of DNA that exists apart from the chromosome and
replicates independently of it. Bacterial plasmids carry information that ren-
ders the bacteria resistant to antibiotics. Plasmids are often used in genetic
engineering to carry desired genes into organisms.
Plastics: Non-metallic compounds that result from a chemical reaction, and
are molded or formed into rigid or pliable construction materials or fabrics.
Plugging: 1. The act or process of stopping the flow of water, oil, or gas into or
out of a formation through a borehole or well penetrating that formation. 2.
Stopping a leak or sealing off a pipe or hose.
Plume: 1. A visible or measurable discharge of a contaminant from a given
point of origin. Can be visible or thermal in water, or visible in the air as, for
example, a plume of smoke. 2 The area of measurable and potentially harmful
radiation leaking from a damaged reactor. 3. The distance from a toxic release
considered dangerous for those exposed to the leaking fumes.
Plutonium: A radioactive metallic element similar chemically to uranium.
Point Source: A stationery location or fixed facility from which pollutants are
discharged or emitted. Also, any single identifiable source of pollution. e.g.. a
pipe, ditch, ship, ore pit, factory smokestack.
Pollen: 1. A fine dust produced by plants. 2.The fertilizing element of flower-
ing plants. 3. A natural or background air pollutant.
Pollutant: Generally, any substance introduced into the envirorunent that
adversely affects the usefulness of a resource.
Pollutant Standard Index (PSI): Measure of adverse health effects of air
pollution levels in major cities.
Pollution: Generally, the presence of matter or energy whose nature, location
or quantity produces undesired environmental effects. Under the aean Water
Act, for example, the term is defined as the man-made or man-induced
alteration of the physical, biological, and radiological integrity of water.
Polyelectrolytes: Synthetic chemicals that help solids to dump during sewage
treatment.
Polymen Basic molecular ingredients in plastic.
Polyvinyl Chloride (PVC): A tough, environmen.tally indestructible plastic
that releases hydrochloric acid when burned.
Population: A group of interbreeding organisms of the same kind occupying a
particular space. Generically, the number of humans or other living creatures
in a designated area.
Post-Closure: The time period following the shutdown of a waste manage-
mentor manufacturing facility. For monitoring purposes, this is often consid-
ered to be 30 years.
Potable Watec Water that is safe for drinking and cooking.
Potentially Responsible Party (PRP): Any individual or company—induding
owners, operators, transporters or generators—potentially responsible for, or
contributing to, the contamination problems at a Superfund site. Whenever
possible, EPA requires PRPs, through administrative and legal actions, to
dean up hazardous waste sites they have contaminated.
PPM! PPB: Parts per million/ parts per billion, a way of expressing tiny
concentrations of pollutants in-air, water, soil, hi’man tissue, food, or other
products.
Precipitate: A solid that separates from a solution because of some chemical or
physical change.
Precipitation: Removal of solids from liquid waste so that the hazardous solid
portion can be disposed of safely; removal of particles from airborne emis-
sions.
Precipitators: Air pollution control devices that collect particles from an emis-
sion.
Precursor In photochemical terminology, a compound such as a volatile
organic compound (VOC) that “precedes” an oxidant. Precursors react in
sunlight to form ozone or other photochemical oxidants.
Preliminary Assessment: The process of collecting and reviewing available
information about a known or suspected waste site or release.
Pressure Sewern A system of pipes in which water, wastewater, or other
liquid is transported to a higher elevation by use of pumping force.
Pretreatment: Processes used to reduce, eliminate, or alter the nature of
wastewater pollutants from non-domestic sources before they are discharged
into publidy owned treatment works.
Prevention: Measures taken to minimize the release of wastes to the environ-
ment.
Prevention of Significant Deterioration (PSD): EPA program in which state
and/or federal permits are required that are intended to restrict emissions for
new or modified sources in places where air quality is already better than
required to meet primary and secondary ambient air quality standards.
Primary Drinking Water Regulation; Applies to public water systems and
specifies a contaminant level, which, in the judgement of the EPA Administra-
tor, will have no adverse effect on human health.
Primary Waste Treatment: First steps in wastewater treatment; screens and
sedimentation tanks are used to remove most materials that floats or will
settle. Primary treatment results in the removal of about 30 percent of
carbonaceous biochemical oxygen demand from domestic sewage.
Process Weight: Total weight of all materials, including fuel, used in a
manufacturing process. it is used to calculate the allowable particulate emis-
sion rate from the process.
Proteins: Complex nitrogenous organic compounds of high molecular weight
that contain amino acids as their basic unit and are essential for growth and
repair of animal tissue. Many proteins are enzymes.
Protoplast: A membrane-bound cell from which the outer cell wall has been
partially or completely removed. The term often is applied to plant cells.
Public Water System: A system that provides piped water for human con-
sumption to at least 15 service connections or regularly serves 25 individuals.
Publicly Owned Treatment Works: A waste-treatment works owned by a
state, unit of local government, or Indian tribe, usually designed to treat
domestic wastewaters.
Pumping Station: Mechanical devices installed in sewer or water systems or
other liquid-carrying pipelines that move the liquids to a higher level.
Putrescible; Able to rot quickly enough to cause odors and attract flies.
Pyrolysis: Decomposition of a chemical by extreme heat.
Q
Quality Assurance/Quality Control: A system of procedures, checks, audits,
and corrective actions to ensure that all EPA research design and performance,
environmental monitoring and sampling, and other technical and reporting
activities are of theliighest achievable quality.
Quench Tank: A water-filled tank used to cool incinerator residues or hot
materials during industrial processes.
R
RAD (Radiation Absorbed Dose): A unit of absorbed dose of radiation. One
RAD of absorbed dose is equal to .01 joules per kilogram.
Radiation: Any form of energy propagated as rays, waves, or streams of
energetic particles. The term is frequently used in relation to the emission of
rays from the nudeus of an atom.
Radiation Standards: Regulations that set maximum exposure limits for
protection of the public from radioactive materials.
Radioactive Substances; Substances that emit radiation.
Radiobiology: The study radiation effects on living things.
Radio Frequency Radiation: (See Non-ionizing Radiation.)
Radionudide: Radioactive element characterized according to its atomic mass
and atomic number which can be man-made or naturally occurring. Radioiso-
topes can have a long life as soil or water pollutants, and are believed to have
potentially mutagenic effects on the human bony.
Radius of Vulnerable Zone: The maximum distance from the point of release
of a hazardous substance in which the airborne concentration could reach the
level of concern under specified weather conditions.
Radon: A colorless naturally occurring, radioactive, inert gaseous element
formed by radioactive decay of radium atoms in soil or rocks.
Radon Decay Products: A term used to refer collectively to the immediate
products of the radon decay chain. These include Po-218, Pb-214, Bi-214, and
Po-214, which have an average combined half-life of about 30 minutes.
Rasp: A machine that grinds waste into a manageable material and helps
prevent odor.
Raw Sewage: Untreated wastewater.
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Reasonably Available Control Technology (RACT): The lowest emissions
limit that a particular source is capable of meeting by the application of control
technology that is both reasonably available, as well as technologically and
economically: feasible. RACT is usually applied to existing to existing sources
in nonattainment areas and most cases is less stringent than new source
performance standards.
Receiving Waters: A river, lake, ocean, stream or other watercourse into
which wastewater or treated effluent is discharged.
KechaiBeThe process by which wateris added to a zone of saturation, usually.
iojpercolafion from the soil surface, e.g., the recharge of an aquifer.
Recharge Area: A land area in which water reaches to the zone of saturation
from surface infiltration, e.g. • an area where rainwater soaks through the earth
to reach an aquifer.
Recombinant Bacteria: A type of microorganism whose genetic makeup has
been altered by deliberate introduction of new genetic elements. The offspring
of these altered bacteria also contain these new genetic elements.
Recombinant DNA (rDNA): The new DNA that is formed by combining
pieces of DNA from different organisms or cells.
Recommended Maximum Contaminant Level (RMCL): The maximum level
of a contaminant in drinking water at which no known or anticipated adverse
affect on human health would occur, and which includes an adequate margin
of safety. Recommended levels are nonenforceable health goals. (See: max-
imum contaminant level.)
Reconstructed Sourcs: An existing facility in which components are replaced
to such an extent that the fixed cap al cost of the new components exceed 50
peitent of the capital cost that would be required to construct a comparable
entirely new facility. New source performance standards may be applied to
sources which are reconstructed after the proposal of the standard if it is
technologically and economically feasible to meet the standard.
Record of Decision (ROD): A public document that explains which cleanup
alternative(s) will be used at National Priorities List sites where, under CERC-
LA, Trust Funds pay for the cleanup.
Recycle/Reuse: The process of minimizing the generation of waste by recover-
ing usable products that might otherwise become waste. Examples are the
recycling of aluminum cans, wastepaper, and bottles.
Red Borden An EPA document that is undergoing final review before being
submitted for final management decision.
RedT*ds: Apro liferationofamarineplanktonthatistoxicandoftenfatalto
fish. This natural phenomenon maybe stimulated by theaddition of nutrients.
A tide can be called red, green or brown, depending on the coloration of the
plankton.
Reentry Jnterval: The period of time immediately following the application of
a pesticide during which unprotected workers should not enter a field.
Refuse: (See: solid waste.)
Refuse Reclamatlom Conversion of solid waste into useful products, e.g.,
izanposting organic wastes to make soil conditioners or separating alununwn
and other metals for melting and recyding.
Regeneration: Manipulation of individual cells or masses, of cells to cause
them to develop into whole plants.
Regional Response Team (RRT): Representatives of federal, local, and state
agencies who may assist in coordination of activities at the request of the
On-Scene Coordinator before and during a Superfund response action.
Regkhm* Any manufacturer or formulator who obtains registration for a
pesticide active ingredient or prodi ct,
R sliatioau Formal listing with EPA of a new pesticide before it can be sold
or distributed in intra- or inter-state commerce. The product must be reg-
istered under the Federal Insecticide, Fungicide, and Rodenticide Art. EPA is
responsible’for registration (pre-market licensing) of pesticides on the basis of
data demonstrating that they will not cause unreasonable adverse effects on
human health or the environment when used according to approved label
Registration Standards: Published reviews of all the data available on pesti-
cide active ingredients.
REM (Roentgen Equivalent Man): The unit of dose equivalent from ionizing
radiation to the human body, used to measure the amount of radiation to
which a per or a part of a human has been exposed. -
Remedial Action (RA): The actual construction or implementation phase of a
Si perfund site cleanup that follpws remedial design..
Remedial. Design: A phain of ‘remedial acbon that follows the remedial
investigation/feasibility study and includes development of engineering
thawnags and specifications for a site cleanup.
16
Remedial Investigation: An in-depth study designed to gather the data neces-
sary to determine the nature and extent of contamination at a Superfund site;
establish criteria for cleaning up the site; identify preliminary alternatives for
remedial actions; and support the technical and cost analyses of the alterna-
tives. The remedial investigation is usually done with the feasibility study.
Together they are usually referred to as the “RI/ES”.
Remedial Project Manager (RPM): The EPA or state official responsible for
overseeing remedial action at a site.
Remedial Response: A long-term action that stops or substantially reduces a
release or threat of a release of hazardous substances that is serious but not an
immediate threat to public health.
Removal Action: Short-term immediate actions taken to address releases of
hazardous substances that require expedited response. (See: cleanup.)
Reportable Quantity (RQ): The quantity of a hazardous substance that
triggers reports under CERCLA. If a substance is released in amounts exceed-
ing its RQ, the release must be reported to the National Response Center, the
SERC, and community emergency coordinators for areas likely to be affected.
Reregistration: The reevaluation and relicensing of existing pesticides origi-
nally registered prior to current scientific and regulatory standards. EPA
reregisters pesticides through its Registration Standards Program.
Reservoir: Any natural or artificial holding area used to store, regulate, or
control water.
Residual: Amount of a pollutant remaining in the environment after a natural
or technological process has taken place, e.g., the sludge remaining after
initial wastewater treatment, or particulates remaining in air after the air
passes through a scrubbing or process.
Resistance: For plants and animals, the ability to withstand poor environmen-
tal conditions and/or attacks by chemicals or disease. The ability maybe inborn
or developed.
Resource: A person, thing, or action needed for living or to improve the
quality of life.
Response Action: A CERCLA-authorized action involving either a short-term
removal action or a long-term removal response that may include but is not
limited to: removing hazardous materials from’ a site to an EPA-approved
hazardous waste facility for treatment, containment, or destruction; contain-
ing the waste safely on-site; destroying or treating the waste on-site; and
identifying and removing the source of ground-water contamination and
halting further migration of contaminants. (See: cleanup.)
Resource Recoveiy The process of obtaining matter or energy from materials
formerly discarded.
Restoration: Measures taken to return a site to pre-violation conditions.
Restricted Use: When a pesticide is registered, some or all of its uses may be
classified (under FIFRA regulations) for restricted use if the pesticide requires
special handling because of its toxicity. Restricted-use pesticides may be
applied only by trained, certified applicators or those under their direct
supervision.
Restriction Enzymes: Enzymes that recognize certain specific regions ofa long
DNA molecule and then cut the DNA into smaller pieces.
Reverse Osmosis: A water treatment process used in small water systems by
adding pressure to force water through a semi-permeable membrane. Reverse
osmosis removes most drinking water contaminants. Also used in wastewater
treatment. Large-scale reverse osmosis plants are now being developed.
Ribonudeic Acid (RNA): A molecule that carries the genetic message from
DNA to a cell’s protein-producing mechanisms; similar to, but chemically
different from, DNA.
Ringlemann Chart A series of shaded ifiustrations used to measure the
opacity of air pollution emissions. The chart ranges from light grey through
black and is used to set and enforce emissions standards.
Riparian Habitat: Areas adjacent to rivers and streams that have a high
density, diversity, and productivity of plant and animal species relative to
nearby uplands.
Riparian Rights: Entitlement of a land owner to the water on or bordering his
property, including the right to prevent diversion or misuse of upstream
waters. Generally, a matter of state law.
Risk Assessment: The qualitative and quantitative evaluation performed in an
effort to define the risk posed to human health and/or the environment by the
presence or potential presence and/or use of sj,ecific pollutants.
Risk çornmuuiQtiQn: The exchange of information about health or environ-
mental risks between risk assessoct, risk mariagers, the general public, new
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Risk Management; The process of evaluating alternative regulatory and non-
regulatory responses to risk and selecting among them. The selection process
necessarily requires the consideration of legal, economic and social factors.
River Basin: The land area drained by a river and its tributaries.
RodentIcide: A chemical or agent used to destroy rats or other rodent pests, or
to prevent them from damaging food, crops, etc.
Rough Fish: Those fish, not prized for eating, such as gar and suckers. Most
are more tolerant of changing environmental conditions than gánie species.
Rubbish: Solid waste, excluding food waste and ashes, from homes, in-
stitutions, and work-places.
Run-Off: That part of precipitation. snow melt, or irrigation water that runs off
the land into streams or other surface-water. It can carry pollutants from the air
and land into the receiving waters.
Salinity: The degree of salt in water.
Salts: Minerals that water picks up as it passes through the air, over and under
the ground, and as it is used by households and industry.
Salt Water Intrusion: The invasion of fresh surface or ground water by salt
water. If the salt water comes from the ocean it may be called sea water
intrusion.
Salvage: The utilization of waste materials.
Sanitation: Control of physical factors in the human environment that could
harm development, health, or survival.
Sand Filters: Devices that remove some suspended solids from sewage. Air
and bacteria decompose additional wastes filtering through the sand so that
cleaner water drains from the bed.
Sanitary Landfill: (See: landfill, sanitary.)
Sanitary Sewers: Underground pipes that carry off only domestic or industrial
waste, not storm water.
Sanitary Survey: An on-site review of the water sources, facilities, equipment,
operation and maintenance of a public water system to evaluate the adequacy
of those elements for producing and distributing safe drinking water.
Saturated Zone: A subsurface area in which all pores and cracks are filled with
water under pressure equal to or greater than that of the atmosphere.
Scrap: Materials discarded from manufacturing operations that may be suit-
able for reprocessing.
Screening: Use of screens to remove coarse floating and suspended solids
from sewage.
Scrubber. An air pollution device that uses a spray of water or reactant or a dry
process to trap pollutants in emissions. -
Secondary Drinking Water Regulations: Unenforceable regulations which
apply to public water systems and which specify the maximum contamination
levels which, in the judgement of EPA, are required to protect the public
welfare. These regulations apply to any contaminants that may adversely
affect the odor or appearance of such water and consequently may cause
people served by the system to discontinue its use.
Secondary Treatment: The second step in most publicly owned waste treat-
ment systems in which bacteria consume the organic parts of the waste. It is
accomplished by bringing together waste, bacteria, and oxygen in trickling
filters or in the activated sludge process. This treatment removes floating and
settleable solids and about 90 percent of the oxygen-demanding substances
and suspended solids. Disinfection is the final stage of secondary treatment.
(See: primary, tertiary treatment.)
Secure Chemical: (See: landfills.)
Secure Maximum Contaminant Level: Maximum permissible level of a con-
taminant in water which is delivered to the free flowing outlet of the ultimate
user of a water supply, the consumer, or of contamination resulting from
corrosion of piping and plumbing caused by water quality.
Sediments: Soil, sand, and minerals washed from land into water usually after
rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting
areas and holes of water animals, and clouding the water so that needed
sunlight might not reach aquatic plants. Careless farming, mining, and build-
ing activities will expose sediment materials, allowing them to be washed off
the land after rainfal!s.
Sedimentation: Letting solids settle out of wastewater by gravity during
wastewater treatment.
Sedimentation Tanks: Holding areas fur wastewater where floating wastes
are skimmed off and settled solids are removed for disposal.
Selectivël’esticide: A chemical designed to affect only certain types of pests,
leaving other plants and inimals unharmed.
Semi-Confined Aquifer. An aquifer that is partially confined by a soil layer (or
layers) of low permeability through which recharge and discharge can occur.
Senescence: Term for the aging process. Sometimes used to describe lakes or
other bodies of water in advanced stages of eutrophication.
Septic Tank: An underground storage tank for wastes from homes having no
sewer line to a treatment plant. The waste goet directly from the home to the
tank, where the organic waste is decomposed by bacteria and the sludge
settles to the bottom. The effluent flows out of the taiik into the ground
through drains; the sludge is pumped Out periodically.
Service Connector: The pipe that carries tap water from the public water main
to a building.
Settleable Solids: Material heavy enough to sink to the bottom of a wastewater
treatment tank.
Settling Chamber. A series of screens placed in the way of flue gases to slow
the stream of air, thus helping gravity to pull particles out of the emission into
a collection area.
Settling Tank: A holding area for wastewater, where heavier particles sink to
the bottom for removal and disposal.
Sewage: The waste and wastewater produced by residential and commercial
establishments and discharged into sewers.
Sewage Lagoon: (See: lagoon.)
Sewage Sludge: Sludge produced at a Publicly Owned Treatment Works, the
disposal of which is regulated under the Clean Water Act.
Sewer: A channel or conduit that carries wastewater and stormwater runoff
from the source to a treatment plant or receiving stream. Sanitary sewers carry
household, industrial, and commercial waste. Storm sewers carry runoff from
rain or snow. Combined sewers are used for both purposes.
Sewerage: The entire system of sewage collection, treatment, and disposal.
Shotgun: Non-scientific term for the process of breaking up the DNA derived
from an organism and then moving each separate and unidentified DNA
fragment into a bacterium.
Signal Words: The words used on a pesticide label—Danger, Warning,
Caution—to indicate the level of toxicity of the chemicals.
Significant Deterioration: Pollution resulting from a new source in previously
“clean” areas. (See: prevention of significant deterioration.)
Significant Municipal Facilities: Those publicly owned sewage treatment
plants that discharge a million gallons per day or more and are therefore
considered by states to have the potential for substantial effect on the quality of
receiving waters.
Significant Violations: Violations by point source dischargers of sufficient
magnitude and/or duration to be a regulatory priority.
Silt: Fine partides of sand or rock that can be picked up by the air or water and
deposited as sediment.
Silviculture: Management of forest land for timber. Sometimes contributes to
water pollution, as in clear-cutting.
Sinking: Controlling oil spills by using an agent to trap the oil and sink it to the
bottom of the body of water where the agent and the oil are biodegraded.
Site Inspection: The collection of information from a Superfund site to de-
termine the extent and severity of hazards posed by the site. It follows and is
more extensive than a preliminary assessment. The purpose is to gather
information necessary to score the site, using the Hazard Ranking System, and
to determine if the site presents an immediate threat that requires prompt
removal action.
Siting: The process of choosing a location for a facility.
Skimming: Using a machine to remove oil or scum from the surface of the
water.
Slow Sand Filtration: Treatment process involving passage of raw water
through a bed of sand at low velocity which results in the substantial removal
of chemical and biological contaminants,
Sludge: A semi-solid residue from any of a number of air or water treatment
processes. Sludge can be a hazardous waste.
Slurry: A watery mixture of insoluble matter that results from some pollution
control techniques.
Smelter: A facility that melts or fuses ore, often with an accompanying chem-
ical change, to separate the metal. Emissions are known to cause pollution.
Smelting is the process involved.
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Smog: Mr pollution associated with oxidants. (See: photochemical smog.)
Smoke: Particles suspended in air after incomplete combustion of materials.
Soft Detergents: Cleaning agents that break down in nature.
Soft Water: Any water that is not “hard,” i.e., does not contain a significant
amount of dissolved minerals such as salts containing calcium or magnesium.
Soil Adsorption lield: A sub-surface area containing a trench or bed with
dean stones anda system of distribution piping through which treated sewage
may seep into the surrounding soil for further treatment and disposal.
Soil Conditionen An organic material like humus or compost that helps soil
absorb water, build a bacterial community. and distribute nutrients and
m i ner
Soil Gast (aseous elements and compounds that occur in the small spaces
between particles of the earth and soil. Such gases can move through or leave
the soil or rock, depending on changes in pressure.
Solden A metallic compound used to seal the joints between pipes. Until
recently, most solder ocontained 50 percent lead.
Sole Source Aquifer: An aquifer that supplies 50 percent Or more of the
drinking water of an area.
Solid Waste: Non-liquid., non-soluble materials ranging from municipal gar-
báge to industrial wastes that contain complex, and sometimes hazardous,
substances. Solid wastes also include sewage sludge, agricultural refuse,
demolition wastes, and mining residues. Technically, solid waste also refers to
liquids and gases in containers
Solid Waste Dispond: The final acement of refuse that is not salvaged or
recycled.
Solid Waste Management: Supervised handling of waste materials from their
source through recovery processes to disposal
Solidification and Stabilization: Removal of wastewater from a waste or
changing it chemically to make the waste less permeable and susceptible to
transport by water.
Solvent Substance (usually liquid) capable of dissolving or dispersing one or
more other substances.
Soot: Carbon dust formed by incomplete combustion.
Soiptiun. The action of soaking up orattractingsubstances A process used in
many pollution control systems.
Special Review: Formerly known as Rebuttable Presumption Against Regis-
tratio (RPAR), this is the regulatory process through which existing pesti-
ddes suspected of posing unreasonable risks to human health, non-target
organisms, or the environment are referred for review by EPA. The review
requires an intensive iisklbeneflt analysis with opportunity for public corn-
mOnt. if the risk of any use of a pesticide is found to outweigh social and
ecxrnomicbeneflts,regu latory actions—ranging from label revisions and use-
restriction to cancellation or suspended registration—can be initiated.
Species: A repcuductwdy isolated aggregate of interbreeding populations of
orgamsms.
Spill Prevention Control and Countermeasures Plan (SPCC) Plan covering
the release of hamrdous substances as defined in the Clean Water Act.
Sprawli Unplanned development of open land.
SpoiL Dirt or rock that has been removed from its ongmallocation destroying
the crnnposition at the soil in the process, as with strip-mining or dredging.
Stabilizallois: Conversion of the active organic matter in sludge into inert,
harmless material.
Stabilization Ponde (See: lagoon.)
Stable Am A mass of air that is not moving normally, so that it holds rather
than disperses pollutants.
Stack: A chimney or smokestack, a vertical pipe that discharges used air.
Stack Effect: Used air, as in a chimney, that moves upward because it is
warmer than the surrounding atmosphere.
Stack Can (See: flue gas.)
Stagnation: Lack of motion in a mass of air or water, which tends to hold
pollutants.
Standards: Prescriptive norms which govern action and actual limits on the
amount of pollutants oreniissions produced. EPA, under most of its responsi-
bihtres establishes minimum standards States are allowed to be stricter
51* Emergency Response Commission (SERC): Commi sion apointed by
r state governor according to the requirements of SARA Title ifi. The
S*C’s designate emergency planning districts appoint local emergency
p1 lug committees, and supervise and coordinate their activities.
is
State implementation Plans (SW): EPA-approved state plans for the establish-
ment, regulation. and enforcement of air pollution standards.
Stationary Source: A fixed, non-moving producer of pollution, mainly power
plants and other facilities using industrial combustion processes.
Sterilization: 1. In pest control, the use of radiation and chemicals to damage
body cells needed for reproduction. 2. The destruction of all living organisms
in water or on the surface of various materials. In contrast, disinfection is the
destruction of most living organisms in water or on surfaces.
Storage: Temporary holding of waste pending treatment or dispcsai. Storage
methods include containers, tanks, waste piles, and surface impoundments.
Storm Sewer: A system of pipes (separate from sanitary sewers) that carry
only water runoff from building and land surfaces.
Stratification: Separating into layers.
Stratosphere: The portion of the atmosphere that is 10-to-25 miles above the
earth’s surface.
Ship-Cropping: Growing crops in a systematic arrangement of strips or bands
which serve as barriers to wind and water erosion.
Strip-Mining: A process that uses machines to scrape soil or rock away from
mineral deposits just under the earth’s surface.
Sulfur Dioxide (S02): A heavy, pungent, colorless, gaseous air pollutant
formed primarily by the combustion of fossil plants.
Sump: A pit or tank that catches liquid runoff for drainage or disposal.
Sump Pump: A mechanism for removing water or wastewater from a sump or
wet well.
Superfund: The program operated under the legislative authority of CERCLA
and SARA that funds and carries out the EPA solid waste emergency and
long-term removal remedial activities. These activities include establishing the
National Priorities List, investigating sites for inclusion on the list, determin-
ing their priority level on the list, and conducting and/or supervising the
ultimately determined cleanup and other remedial actions.
Surface Impoundment: Treatment, storage, or disposal of liquid hazardous
wastes in ponds.
Surface Water: All water naturally open to the atmosphere (rivers, lakes,
reservoirs, streams, impoundments, seas, estuaries, etc.) and all springs,
wells, or other collectors which are directly influenced by surface water.
Surfactant: A surface-active agent used in detergents to cause lathering.
Surveillance Systenr: A series of monitoring devices designed to determine
environmental quality.
Suspended Solids: Small partides of solid pollutants that float on the surface
of, or are suspended in sewage or other liquids. They resist removal by
conventional means. (See: Total Suspended Solids.)
Suspension: The act of suspending the use of a pesticide when EPA deems it
necessary to do so in order to prevent an imminent hazard resulting from
continued use of the pesticide. An emergency suspension takes effect im-
mediately; under an ordinary suspension a registrant can request a hearing
before the suspension goes into effect. Such a hearing process might take six
months.
Suspension Culture: Individual cells or small dumps of cells growing in a
liquid nutrient medium.
Swamp: A type of wetland that is dominated by woody vegetation and does
not accumulate appreciable peat deposits. Swamps maybe fresh or salt water
and tidal or non-tidal. (See: Wetlands.)
Synergism: The cooperative interaction of two or more chemicals or other
phenomena producing a greater total effect than the sum of their individual
effects.
Synthetic Organic Chemicals (SOCs): Man-made organic chemicals. Some
SOCs are volatile, others tend to stay dissolved in water rather than evaporate
out of it.
Systemic Pesticide: A chemical that is taken up from the ground or absorbed
through the surface and carried through the system of the organism being
protected, making the organism toxic to pests.
T
Tailings: Residue of raw materials or waste separated out during the process-
ing of crops or mineral ores
TBT Paints (Taybutilin): (See: organotins.)
Technology-Based Standards: Effluent limitations applicable to direct and
indirect sources which are developed on a category-by-category basis using
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Teratogen: Substance that causes malformation or serious deviation from
normal development of embryos and fetuses.
Terracing: Diking. built along the contour of sloping agricultural land, that
holds runoff and sediment to reduce erosion.
Tertiary Treatment: Advanced cleaning of wastewater that goes beyond the
secondary or biological stage. It removes nutrients such as phosphorus and
nitrogen and most BOD and suspended solids.
Thermal Pollution: Discharge of heated water from industrial processes that
can affect the life processes of aquatic organisms.
Threshold Limit Value (TLV): Represents the air concentrations of chemical
substances to which it is believed that workers may be daily exposed without
adverse effect.
Threshold Planning Quantity: A quantity designated for each chemical on the
list of extremely hazardous substances that triggers notification by facilities to
the state emergency response commission that such facilities are subject to
emergency planning under SARA Title lii.
Tidal Marsh: Low, flat marshlands traversed by channels and tidal hollows
and subject to tidal inundation; normally, the only vegetation present are
salt-tolerant bushes and grasses. (See: wetlands.)
Tolerances: The permissible residue levels for pesticides in raw agricultural
produce and processed foods. Whenever a pesticide is registered for use on a
food or a feed crop, a tolerance (or exemption from the tolerance requirement)
must be established. EPA establishes the tolerance levels, which are enforced
by the Food and Drug Administration and the Department of Agriculture.
Topography: The physical features of a surface area including relative eleva-
tions and the position of natural and man-made features.
Total Suspended Solids (TSS): A measure of the suspended solids in
wastewater, effluent, or water bodies, determined by using tests for “total
suspended non-filterable solids.” (See: suspended solids.)
Toxic Harmful to living organisms.
Toxic Pollutants: Materials contaminating the environment that cause death,
disease, birth defects in organisms that ingest or absorb them. The quantities
and length of exposure necessary to cause these effects can vary widely.
Toxic Chemical Release Forth: Information form required to be submitted by
facilities that manufacture, process, or use (in quantities above a specific
amount) chemicals listed under SARA Title III.
Toxic Cloud: Airborne mass of gases, vapors, fumes, or aerosols containing
toxic materials.
Toxic Substance: A chemical or mixture that may present an unreasonable risk
of injury to health or the environment.
Toxicant A poisonous agent that kills or injures animal or plant life.
Toxicity: The degree of danger posed by a substance to animal or plant life.
(See: acute, chronic toxicity.)
Toxicology: The science and study of poisons control.
Transformation: The process of placing new genes into a host cell, thereby
inducing the host cell to exhibit functions encoded by the DNA.
Transpiration: The process by which water vapor is lost to the atmosphere
from living plants. The term can also be applied to the quantity of water thus
dissipated.
Trash-to-Energy Plan: A plan for putting waste back to work by burning trash
to produce energy.
Treatment, Storage, and Disposal Facility: Site where a hazardous substance
is treated, stored, or disposed. TSD facilities are regulated by EPA and states
under RCRA.
Trichioroethylene TCE): A stable, low-boiling colorless liquid, toxic by inhala-
tion. TCE is used as a solvent, metal degreasing agent, and in other industrial
applications.
Trickling Filten A coarse, biological treatment system in which wastewater is
triclded over a bed of stones or other material covered with bacterial growth.
The bacteria break down the
Trihalomethane (THM): One of a family of organic compounds, named as
derivatives of methane. THM’s are generally the by-product from chlorination
of drinking water that contains organic material.
Troposphere: The lower atmosphere, the portion of the atmosphere between
seven and ten miles from the Earth’s surface where douds are formed.
Trust Fund (CERCLA): A fund set up under the Comprehensive Envirortmen-
tal Response, Compensation and Liability Act (CERCLA) to help pay for
cleanup of hazardous waste sites and for legal action to force those responsible
for the sites to clean them up.
Tundra: A type of ecosystem dominated by lichens, mosses, grasses, and
woody plants. Tundra is found at high latitudes (arctic tundra) and high
altitudes (alpine tundra). Arctic tundra is underlain by permafrost and is
usually very wet. (See: wetlands.)
Turbidimeter: A device that measures the amount of suspended solids in a
liquid.
Turbidity: 1. Haziness in air caused by the presence of particles and pollut-
ants. 2. A similar cloudy condition in water due to suspended silt or organic
matter.
U
Ultra Clean Coal (UCC): Coal that has been washed, ground into fine parti-
cles, then chemically treated to remove sulfur, ash, silicone, and other sub-
stances; usually briquetted and coated with a sealant made from coal.
Ultraviolet Rays: Radiation from the sun that can be useful or potentially
harmful. UV rays from one part of the spectrum enhance plant life and are
useful in some medical and dental procedures; UV rays from other parts of the
spectrum to which humans are exposed (e.g., while getting a sun tan) can
cause skin cancer or other tissue damage. The ozone layer in the atmosphere
provides a protective shield that limits the amount of ultraviolet rays that reach
the Earth’s surface.
Underground Injection Control (UIC): The program under the Safe Drinking
Water Act that regulates the use of wells to pump fluids into the ground.
Underground Sources of Drinking Water: As defined in the UIC program,
this terms refers to aquifers that are currently being used as a source of
drinking Water, and those that are capable of supplying a public water system.
They have a total dissolved solids content of 10,000 milligrams per liter or less,
and are not “exempted aquifers.” (See: exempted aquifer.)
Underground Storage Tank: A tank located all or partially under ground that
is designed to hold gasoline or other petroleum products or chemical solu-
tions.
Unsaturated Zone: The area above the water table where the soil pores are not
fully saturated, although some water may be present.
Uranium: A radioactive heavy metal element used in nuclear reactors and the
production of nudear weapons. Term refers usually to U-238 , the most abun-
dant radium isotope, although a small percentage of naturall ’-occumng ura-
nium is U-235.
Urban Runoff: Stormwater from city streets and adjacent domestic or com-
mercial properties that may carry pollutants of various kinds into the sewer
systems andlor receiving waters.
V
Vaccine: Dead or partial or modified antigen used to induce immunity to
certain infectious diseases.
Vapor: The gaseous phase of substances that are liquid or solid at atmospheric
temperature and pressure, e.g., steam.
Vapor Capture System: Any combination of hoods and ventilation system that
captures or contains organic vapors in order that they may be directed to an
abatement or recovery device.
Vapor Dispersion: The movement of vapor clouds in air due to wind, gravity
spreading, and mixing.
Vapor Plumes: Flue gases that are visible because they contain water droplets.
Vaporization: The change of a substance from a liquid to a gas.
Variance: Government permission for a delay or exception in the application
of a given law, ordinance, or regulation.
Vector 1. An organism, often an insect or rodent, that carries disease. 2. An
object that is used to transport genes into a host cell (vectors can be plasmids,
viruses, or other bacteria). A gene is placed in the vector; the vector then
“infects” the bacterium.
Ventilation/Suction: The act of admitting fresh air into a space in order to
replace stale or contaminated air; achieved by blowing air into the space.
Similarly, suction represents the admission of fresh air into an interior space
by lowering the pressure outside of the space, thereby drawing the con-
taminated air outward.
Vinyl Chloride: A chemical compound, used in producing some plastics, that
is believed to be carcogemc.
Virus: The smallest form of microorganisms capable of causing disease.
Volatile: Description of any substance that evaporates readily.
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Volatile Organic Compound (VOC): Any organic compound which partici-
pates in atmospheric photochemical reactions except for those designated by
the EPA Administrator as having negligible photochemical reactivity.
Volatile Synthetic Organic Qsemicals: Chemicals that tend to volatilize or
evaporate from water.
Vubwrebility Analysis: Assessment of elements in the community that are
susceptible to damage should a release of haza*.Ious materials occur.
Vulnerable Zone: An area over which the airborne concentration of a chem-
ical involved in an accidental release could reach the level of concern.
w
Wástei 1. Unwanted materials left over from a manufacturing process. 2.
Refuse from places of human or animal habitation.
Waste Load Allocation: The maximum load of pollutants each discharger of
waste Is allowed to release into a particular waterway. Discharge limits are
usually required fur each specific water quality criterion being, or expected to
WasteTieabnent Stream: The continuous movement of waste from generator
to treater and disposer.
Waste Treatment PIant A facility containing a series of tanks, screens, filters
and other processes by which pollutants are removed from water
Wastewater The spent or used water from individual homes a community a
farm, or an industry that contains dissolved or suspended matter.
WsrtewaterOperaltons and Mau enance Actions taken after construction to
assure tMt facilities constructed to treat wastewater will be properly operated;
maintained, and managed to achieve efficiency levels and prescribed effluent
levelS In anoptimum manner.
WdrrF ’üllutlose The presence in water of enough harmful or objectionable
mate to damage the water’s quality.
WaterQuallty Criteria: Specific levels of water quality which, if reached, are
4vct4to render a body of water suitable for its designated use. The criteria
are based on specific levels of pollutants that would make the water harmful if
used for drinking, swimming, farming, fish production or mdustrial proc-
ess
Water Quality Standards: State-adopted and EPA-approved ambient stan-
dards for water bodies. The standards cover the use of the water body and the
wateruualitvaiteria which must be met to protect the designated use or uses.
Watershed: The land area that drains into a stream.
Water Supplien A person who owns or operates a public water system.
Water Supply System: The collection, treatment, storage, and distribution of
potable water from source to consumer.
Water Solubiity: The maximum concentration of a chemical compound
which can result when it is dissolved in water. If a substance is water soluble it
can very readily disperse through the environment.
Water Table: The level of ground water.
Well: A bored, drilled, or driven shaft, or a dug hole, whose depth is greater
than the largest surface dimension and whose purpose is to reach under-
ground water supplies or oil, or to store or bury fluids below ground.
Well Injection: The subsurface emplacement of fluids in a well.
Well Monitoring: The measurement, by on-site instruments or laboratory
methods, of the quality of water in a well.
Well Plug: A watertight and gastight seal installed in a bore hole or well to
prevent movement of fluids.
Wetlands: An area that is regularly, saturated by surface or ground water and
subsequently is characterized by a prevalence of vegetation that is adapted for
life in saturated soil conditions. Examples include: swamps, bogs, fens,
marshes, and estuaries.
Wildlife Refuge: An area designated for the protection of wild animals, within
which hunting and fishing are either prohibited or strictly controlled.
Wood-Burning Stove Pollution: Air pollution caused by emissions of particu-
late matter, carbon monoxide, total suspended particulates, and polycydic
organic matter from wood-burning stoves.
Working Level (WL): A unit of measure for documenting exposure to radon
decay products. One working level is equal to approximately 200 picocuries
per liter.
Working Level Month (WLM): A unit of measure used to determine cumula-
tive exposure to radon.
xj,Y,z
Xenobiotia Term for non-naturally occurring man-made substances found in
the environment (i.e., synthetic material solvents, plastics.).
Zooplankton: Tiny aquatic animals eaten by fish.

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