United States          Office of            December 1989
                Environmental Protection     Communications And       19K-1002
                Agency             Public Affairs (A-107)
vvEPA        Glossary Of
                Environmental Terms
                And Acronym List
                              U.S. Environmental Protection Agenc?
                              Region 5, Library (PI-12J)
                              77 West Jackson Boulevard, 12th Floor
                              Chicago, IL 60604-3590
                                                    Printed on Recycled Paper

This glossary of environmental and acronym list replaces "Common Environmental Terms,
published by the Environmental Protection Agency in 1974 and revised in 1978. It is designed I
give the user an explanation of the more commonly used environmental terms appearing i
EPA publications, news releases and other Agency documents available to the general pubrL
students, the  news  media, and Agency employees.  The terms and definitions in th
publication were selected to give the user a general  sense of what a term or phrase means i
relatively non-technical language, although it was obviously necessary to use some scientif
  The terms selected for inclusion came from previously published lists, internal  glossark
produced by various programs, and specific suggestions made by many Agency programs an
offices. The chemicals and pesticides selected for inclusion were those most frequently referre
to in Agency publications or which are the subject of major EPA regulatory or prograi
  Definitions or information about substances or  program activities not included in th
glossary may be found in EPA libraries or scientific/technical reference documents or may b
obtained from the various program offices.
  The definitions do not constitute the Agency's official use of terms and phrases for regulator
purposes. Nothing in this document should be construed to in any way alter or  supplant an
other federal document. Official terminology may be found in the laws and related regulatior
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 c
Communications and Public Affairs, A-107, USEPA, Washington DC, 20460.

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

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.
Alar: 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.
Aldicarb: 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 are food for 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-
Alpha Particle: A positively charged particle composed of 2 neutrons and 2
protons released by some atoms undergoing radioactive decay. The particle is
identical to the nucleus 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
Ambient Air: 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 Hole": 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 anu water quality require-
ments prohibiting deterioration where pollution levels are above the legal
Antigen: A substance that causes production of antibodies when introduced
into  animal or human tissue.
Aquifer: An underground geological formation, or group of formations, con-
taining usable amounts of ground water that can supply wells and spnngs.
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 o:
asbestos fibers. The disease makes breathing progressively more difficult anc
can lead to death.
Asbestos:  A mineral fiber  that can pollute air or water and cause cancer 01
asbestosis when inhaled. EPA has banned or severely restricted its use ir
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 (an):  A standard unit  of pressure representing the pressun
exerted by a 29.92-inch column of mercury a t sea level at 45' latitude and equa
to 1000 grams per  square centimeter.
Atmopshere (the):  The whole mass of air surrounding the earth, composec
largely of  oxygen and nitrogen.

Atomize: To divide a liquid into extremely minute particles, either by impacl
with a jet of steam or compressed air,  or by passage through some mechanica
Attainment Area: An area considered to have air quality as good as or bettei
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 ares
for others.
Attenuation: The process by which a compound is reduced in concentratior
overtime,  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.


Background Level: In air pollution control, the concentration of air pollutant
in a definite area during a fixed period of time prior to the starting up or on thi
stoppage  of a source of emission under control. In toxic substances monitor
ing, the average presence in the environment, originally referring to naturall1
occurring phenomena.

BACT—Best Available Control Technology: An emission limitation based 01
the maximum degree of emission reduction which (considering energy, en
vironmental, and economic impacts, and other costs) is achievable througl
application of production processes and available  methods, systems, anc
techniques. In  no event does BACT permit emissions  in  excess of thos<
allowed under  any applicable Clean Air Act provisions. Use of the BAC]
concept is allowable on a case by  case basis  for  major new or modifiec
emissions sources in attainment areas and applies to each regulated pollutant

Bacteria: (Singular: bacterium) Microscopic living organisms which can aid ir
pollution control by consuming or breaking down organic matter in sewage 01
by similarly acting on oil spills or other water pollutants. Bacteria in soil, watei
or air can also cause human,  animal and plant health problems.

Baffle Chamber: In incinerator design, a chamber designed to promote thi
settling of fly ash  and coarse particulate matter by changing the director
and/or reducing the velocity of the gases produced by the combustion of tht
refuse or  sludge.
Baghouse Filter: Large fabric bag,  usually made  of glass fibers, used ti
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 vacuun
cleaner, passing the air  and smaller particulate matter, while entrapping thi
larger particulates.
Baling: Compacting solid  waste into blocks to  reduce volume and simplif-
Ballistic Separator: A machine that sorts organic from inorganic matter fo
Band Application: In pesticides, the spreading of chemicals over, or next to
each row of plants in a  field.
Banking: A system for recording qualified air emission reductions for later us<
in bubble, offset, or netting transactions. (See: emissions trading.)
Bar Screen: In wastewater treatment, a device used to remove large solids

Barrier Coating(s): A layer of a material that acts to obstruct or prevent 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
moving 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 or near the bottom of a stream, lake, or ocean.
Benthic Region: The bottom layer of a body of water.
Beryllium: An airborne metal that can be hazardous to human health when
inhaled. It is discharged by machine shops, ceramic and propellant plants, and
Beta Particle: 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.)
Bioassay: Using  living organisms to measure the effect of a substance, factor,
or condition by comparing before-and-after data. Term is often used to mean
cancer bioassays.
Biochemical Oxygen Demand (BOD): 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 river 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:
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
Biomass: All of the living material in a given area, often refers to vegetation.
Also called "biota".
Biomonitoring: 1. The use of living organisms to test the suitability 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.
Biostabilizer: A  machine that converts solid waste into compost by grinding
and aeration
Biota: (See. biomass.)
Biotechnology: 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 toxics from bodies of water,  or as pesticides
Biotic Community: A naturally occurring assemblage of plants and animals
that live  in the same  environment and are mutually sustaining and inter-
Black Lung: A disease of the lungs caused by 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 floating 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. Such legislation is designed to discourage use of throw-
 away containers.
 Bottom Land Hardwoods: Forested fresh-water 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
 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.
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 clay or other  highly impermeable material installed over the
top of a closed landfill to prevent entry of rainwater and minimize production
of leachate.
Capture Efficiency: The fraction of all organic vapors generated by a process
that is 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  (CO2): 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
Carcinogenic:  Cancer-producing.
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.

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
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-
Cathodic Protection: A technique to prevent corrosion of a metal surface by
making that surface the cathode of an  electrochemical cell.
Caustic Soda: Sodium hydroxide, a strong alkaline substance used as the
cleaning 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 BODS, except that nitrogen demand is
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 Collector: 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
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 DDT, aldrin, dieldrin, heptachlor, chlordane,
lindane, endrin, mirex, hexachloride, and toxaphene. Other examples include
TCE, used as an industrial solvent.
Chlorinated Solvent:  An organic  solvent containing chlorine atoms,  e.g.,
methylene chloride and 1,1,1-trichloromethane which is 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.
Chlorofluorocarbons (CFCs): A family of inert, nontoxic, and easily liquified
chemicals used in refrigeration, air conditioning, packaging, insulation, or as
solvents and aerosol propellents. Because CFCs are not destroyed in the lower
atmosphere they drift into the upper atmosphere where their chlorine com-
ponents destroy ozone.
Chlorosis: Discoloration of normally green plant parts, that can be caused by
disease, lack of nutrients, or various air pollutants.
Chromium:  (See: heavy metals.)
Chronic Toxicity: 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.
Clarifier: A tank in which solids are settled to the bottom and are subsequently
removed as  sludge.
Cleanup:  Actions taken  to deal with a release or threat  of release  of a
hazardous substance that could affect humans and/or the environment. The
term "cleanup" is sometimes used interchangeably with the terms remedial
action, removal action, response action, or corrective action.
Clear Cut: A forest management technique that involves harvesting all th
trees in one area at one time. Under certain soil and slope conditions it cai
contribute sediment to water pollution.
Cloning: In biotechnology, obtaining a group of genetically identical cells fror
a single cell. This term has assumed a more general meaning that include
making copies of a gene.
Closed-Loop Recycling: Reclaiming or reusing wastewater for non-potabl
purposes in an enclosed process.
Coagulation: A clumping of particles in wastewater to settle out impurities. 1
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 01
the uses of the sea and its ecology, or, inversely, whose uses and ecology ar
affected by the sea.
Coefficient of Haze (COH): A measurement of visibility interference in th
Coliform Index: A rating of the purity of water based on a count of feca
Coliform Organism: Microorganisms found in the intestinal tract of human
and animals. Their presence in water indicates fecal pollution and potentiall
dangerous bacterial contamination by disease-causing microorganisms.
Combined Sewers: A sewer system that carries both sewage and storm-wate
runoff. Normally, its entire flow goes to a waste treatment plant, but during
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 flov
into receiving waters. Storm-water runoff may also carry toxic chemicals fror
industrial areas or streets  into the sewer system.
Combustion: Burning, or rapid oxidation, accompanied by release of energ
in the form of heat and light. A basic cause of air pollution.
Combustion Product: Substance produced during the burning or oxidation c
a material.
Command Post: Facility located at a safe' distance upwind from an accideri
site, where the on-scene coordinator, responders, and technical represents
fives can make response decisions, deploy manpower and equipment, mair
tain liaison with news media, and handle communications.
Comment Period:  Time provided for the public to review and comment on
proposed EPA action or rulemaking after it is published in the Federal Regis
Comminution: Mechanical shredding or pulverizing of waste. Used in bot
solid waste management and wastewater treatment.
Comminuter: A machine that  shreds  or  pulverizes solids to  make wast
treatment easier.
Community Relations: The EPA effort to establish two-way communicatioi
with the public to create understanding of EPA programs and related actions
to assure public input into  decision-making processes  related to  affectei
communities, and to make certain that the Agency is aware of and responsiv
to public concerns. Specific  community relations activities are  required ii
relation to Superfund remedial actions.
Community Water System: A public water system  which  serves at least 1
service connections used by year-round residents or regularly serves at least 2
year-round residents.
Compaction: Reduction of the bulk of solid waste by rolling and tamping.
Compliance Coating: A coating whose volatile organic compound conten
does not exceed that  allowed by regulation.
Compliance Schedule: A  negotiated agreement between a pollution sourc
and a government agency that specifies dates and  procedures  by which
source will  reduce emissions and, thereby, comply with a  regulation
Compost: A mixture of garbage and degradable trash with soil in which certaii
bacteria in the soil break down the garbage and trash into organic fertilizer.
Composting: The natural biological decomposition of organic material in th
presence of air to form a humus-like material. Controlled methods of composl
ing include mechanical mixing and aerating, ventilating  the materials  b
dropping them through a vertical series of aerated chambers, or placing th
compost in piles out in the open air and mixing it or turning it periodically.

Conditional Registration: Under special  circumstances, the Federal In-
secticide, Fungicide, and Rodenticide Act  (FIFRA) permits  registration of
pesticide products that is "conditional" upon the submission of additional
data. These special circumstances include a finding by the EPA Administrator
that a 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 reasonable 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 Aquifer: 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 at a Superfund
site; cease or correct actions or processes that are polluting the environment, or
otherwise comply with regulations where the PRPs'  failure to comply caused
EPA to initiate regulatory enforcement actions. The consent decree describes
the actions PRPs will take and may be subject to a public comment period.
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-
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 of certain algae that scratches and dehydrates waxy-coated insects.
Contaminant: Any physical, chemical, biological, or radiological substance or
matter that has an adverse affect on air, water, or soil.
Contingency Plan: A document setting out an organized, planned, and coor-
dinated course of action to be followed in case of a fire, explosion, or other
accident  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, soil, air, and water or carry out research projects.

Contrails: Long, narrow clouds caused when high-flying jet aircraft disturb
the atmosphere.
Contour  Plowing: Farming methods that break ground following the shape of
the land  in a way that discourages erosion.
Control Technique Guidelines (CTG): A series of EPA documents designed
to assist states in defining reasonable available control technology (RACT) for
major sources 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-
tion in nuclear reactors, electric generators, various industrial and mechanical
processes,  and automobile engines
Cooling  Tower: 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
Corrosion: 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 contact between two metals
Corrosive: A chemical 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,  such analysis does not require EPA to choose the least expensive
alternative. For example, when selecting a method for cleaning up a 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 cleanup actions by the federal
 Cover: Vegetation or other material providing protection as  ground cover.
 Cover Material: Soil used to cover compacted solid waste in a sanitary landfill.
 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 Clean 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, that is 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 Working 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 Collector: A device that uses centrifugal force to pull large particles
 from polluted  air.
DDT: The first chlorinated hydrocarbon insecticide (chemical name: Dichloro-
Diphsdyl-Trichloromethane). It has a half-life of 15 years and can collect in fatty
tissues of certain animals. EPA banned registration and interstate sale of DDT
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-
Dechlorination: Removal of chlorine from a substance by chemically replacing
it with hydrogen or hydroxide ions in order to detoxify the substances in-
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.
Defoliant: A herbicide  that removes leaves from trees and growing  plants.
Degradation: The process by which a chemical is reduced to a less complex
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.
Delist: Use of the  petition process to have a facility's toxic designation res-

 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.
 Depressurization: A condition that occurs when the air pressure inside a
 structure is lower than 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 drying 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
 source 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 include cold water fisheries,  public water supply, agriculture,
 Detergent: 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.
 Developer: 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.
 Diazinon: An insecticide. In 1986, EPA banned its use on open areas such as
 sod farms and golf courses because it posed a danger to migratory 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 Air: A type of aeration that forces oxygen into sewage by pumping
 air through perforated pipes inside a holding tank and bubbling it through the
 Digester: 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, liquefacation, and mineralization of pollutants.
 Dike: 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
 Dinocap: 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 EPA in 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 con-
 tamination in commercial products. Tests on laboratory animals indicate that it
 is one of the more toxic man-made chemicals known.
 Direct Discharger: 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 organisrr
 in water. Chlorine is often used to disinfect sewage treatment effluent, wat<
 supplies, wells, and swimming pools.
 Dispersant: A chemical agent used to break up  concentrations of organ
 material such as spilled oil.
 Disposal: Final placement or destruction of toxic, radioactive, or other waste
 surplus or banned pesticides or other chemicals; polluted soils; and drurr
 containing hazardous materials from removal actions or accidental release:
 Disposal may be accomplished  through use of approved secure landfill:
 surface impoundments, land farming, deep well injection, ocean dumping, (
 Dissolved  Oxygen (DO): The oxygen  freely available  in water. Dissolve
 oxygen is vital to fish and other aquatic life and for the prevention of odor
 Traditionally, the level of dissolved oxygen has been accepted as the sing
 most important indicator of a water body's ability to support desirable aquat
 life. Secondary and advanced  waste treatment are generally designed I
 protect DO in waste-receiving waters.
 Dissolved Solids: Disintegrated organic and inorganic material contained i
 water. Excessive amounts make water unfit to drink  or use in industri,
 Distillation: The act of purifying liquids  through boiling, so that the steal
 condenses  to a pure liquid and the pollutants remain in a concentrated res
DNA: Deoxyribonucleic acid,  the molecule in which the genetic informatio
for most living cells is encoded. Viruses,  too, can contain DNA.
DNA Hybridization: Use of  a  segment  of DNA, called a DNA probe, t
identify its  complementary DNA; used to detect specific genes. This proces
takes advantage  of the ability of a single strand of DNA to combine with
complementary strand.
Dose: In radiology, the quantity of energy or radiation absorbed.
Dosimeter: An instrument that  measures exposure to radiation.
Dredging: Removal of mud from the bottom of water bodies using a scoopin
machine. This disturbs the ecosystem and causes silting that can kill aquat
life. Dredging of contaminated muds can  expose aquatic life to heavy meta
and other  toxics.  Dredging activities may be subject to regulation und<
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 Jar: An open container used to collect large particles from the air f<
measurement and analysis.
Dystrophic Lakes: Shallow bodies of water that contain much humus and/t
organic matter; that contain many plants but few fish and are highly acidic
Ecological Impact: The effect that a man-made or natural activity has on livin
organisms and their non-living (abiotic) environment.
Ecology: The relationship of living things to one another and their enviroi
ment, or the study of such relationships.
Economic Poisons: Chemicals used to control pests and to defoliate cash croj:
such as cotton.
Ecosphere: The "bio-bubble" that contains life on earth, in surface waters, an
in the air. (See: biosphere.)
Ecosystem: The  interacting system of a  biological community and  its noi
living environmental surroundings.
Effluent: Wastewater—treated or untreated—that flows out of a treatmei
plant, sewer, or industrial outfall. Generally refers to wastes discharged in(
surface  waters.
Effluent Limitation: Restrictions established by a State or EPA on quantitiei
rates, and concentrations in wastewater discharges.
Electrodialysis: A process that uses electrical current applied to permeab
membranes to remove minerals from water. Often used to desalinize salty i
brackish water.

Electrostatic Precipitator (ESP): An air pollution control device that remove
particles from a gas stream (smoke) after combustion occurs. The ESP impar)
an electrical charge to the particles, causing them to adhere to metal plate
inside the precipitator. Rapping on the plates causes the particles to fall into
hopper  for disposal.
Eligible Costs: The construction costs for waste-water treatment works upo
which EPA grants are based.

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 Domain: Government taking—or forced acquisition—of private land
for public use, with compensation paid to the landowner.
Emission: Pollution discharged into the atmosphere from smokestacks, other
vents, and surface areas of commercial or industrial facilities; from residential
chimneys; and from  motor vehicle, locomotive, or aircraft exhausts

Emission Factor: 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.
Emission Inventory: A listing, by source, of the amount of air pollutants
discharged into the atmosphere of a community. It is used to establish emis-
sion 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 previous limits.
Facilities where this is done are treated as if they exist in a bubble in which total
emissions are averaged out Complexes that reduce emissions substantially
may "bank"  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
clean up a site or pay for the cleanup. An endangerment assessment supple-
ments a remedial investigation.
Enforcement: 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 clean 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 (EDD): 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 of a
party's compliance with applicable environmental requirements. 2. An in-
dependent evaluation of a party's environmental compliance policies,  prac-
tices, and controls.

Environmental Impact Statement: A document required of federal agencies by
the National Environmental Policy Act for major projects or legislative pro-
posals 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, NJ, 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 1970 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
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
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 include 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 exclude specific
classes 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 to be of negligible
photochemical reactivity.
Exempted Aquifer: 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
Extremely Hazardous Substances: Any of 406 chemicals identified by EPA on
the basis of toxicity,  and  listed under  SARA Title III. The list is subject to

Fabric Filter: A cloth device that catches dust particles from industrial emis-
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 "RI/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 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 immediately comes out when a tap is first opened.
This water is likely to have the highest level of lead contamination  from
plumbing materials.
Floe: A clump of solids formed in sewage by biological or chemical action.
Flocculation: The process by which clumps 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.
Flowmeter: 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: Vented air coming out of a chimney after combustion in the burner.
It  can include nitrogen oxides, carbon oxides, water vapor, sulfur oxides,
particles, 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 desulfurization  is currently the state-of-the art technology in
use by major SO2 emitters, e.g., power plants.
Fluorides:  Gaseous, solid, or dissolved compounds containing fluorine that
result from industrial processes; excessive amounts in  food can lead to fluoro
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 (CFCs). 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 hav<
been sitting for a long time in the pipes. In new homes, to flush a systerr
means to send large volumes of water gushing through the unused pipes t(
remove loose particles of solder and flux. 2. To force large amounts of wate
through liquid to clean out piping or tubing and 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 i
forms very fine droplets that resemble smoke or fog. It may be used to destro)
mosquitoes, black flies, and similar pests.
Food Chain: A sequence of organisms, each of which uses the next, lowe
member of the sequence as a food source.
Formaldehyde: A colorless, pungent, irritating gas, Cr^O, used chiefly as i
disinfectant and  preservative and in synthesizing other compounds and re
Formulation: The substance or mixture of substances which is comprised of al
active and inert ingredients in a pesticide.
Fresh Water: Water that generally contains less than 1,000 milligrams-per-litei
of dissolved solids.
Fuel Economy Standard: The  Corporate Average Fuel  Economy Standarc
(CAFE) which went into effect in 1978.  It was meant to enhance the nationa
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 anc
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 functional!)
equivalent when it addresses the substantive components of a NEPA review.
Fungi: (Singular, Fungus) Molds, mildews, yeasts, mushrooms, and pufl
balls, a group of organisms that lack chlorophyll (i.e., are not photosynthetic
and which are usually non-mobile, filamentous, and multicellular. Some grov
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.
Game Fish: Species like trout, salmon, or bass, caught for sport. Many of their
show more sensitivity to environmental 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  othei
electromagnetic waves They are the most penetrating waves of radiant nu
clear 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 £
Geiger Counter: An electrical device that detects the presence of certain type;
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 class or category of dischargers.
Generator: A facility or mobile source thai emits pollutants into the air 01
releases hazardous wastes into water or soil.
Genetic Engineering: A process of inserting new genetic information  intc
existing cells in order to modify any organism for the purpose of changing ont
of its characteristics.
Germicide: Any compound that kills disease-causing microorganisms.
Grain Loading: The rate at which particles 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 smal
water systems and individual homes to remove organics. GAC can be highl}
effective in removing elevated levels of radon from water.

 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 or other 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 Particle Activity: Total activity due to emission of alpha particles.
 Used as the screening measurement for radioactivity generally due to
 naturally-occurring radionuclides. Activity is commonly measured in picocur-
 Gross Beta Particle Activity: Total activity due to emission of beta particles.
 Used as the screening measurement  for radioactivity from man-made
 radionuclides since the decay products of fission are beta particles and gamma
 ray emitters. Activity is commonly measured  in picocuries.
 Ground Cover: 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
 ground water.

 Habitat: The place where a population ( e.g.,  human, animal, plant, micro-
 organism)  lives and its surroundings,  both living and non-living.
 Half-Life:  1. The time required for a pollutant to lose  half its affect on the
 environment. For example, the half-life  of DDT in the environment is 15 years,
 of radium,  1,580 years. 2. The time  required for half of the atoms of a
 radioactive element to undergo decay. 3. The time required for the elimination
 of one half a total dose from the body.
 Halogen: Any of a group of five chemically-related nonmetallic elements that
 includes bromine, fluorine, chlorine, iodine, and astatine.
 Halon: Bromine-containing compounds with long atmospheric lifetimes
 whose breakdown in the stratosphere  cause depletion of ozone. Halons are
 used in fire-fighting.
 Hammermill: A high-speed machine  that hammers and cutters to crush,
 grind, chip, or shred solid wastes.
 Hard Water: Alkaline water containing dissolved salts that interfere with some
 industrial processes and prevent soap  from lathering.
 Hazardous Air Pollutants: Air pollutants which are not covered by ambient
 air quality standards but which, as defined in the Clean Air Act, may reason-
 ably be expected to cause or contribute to irreversible illness or death. Such
 pollutants include asbestos, beryllium, mercury, benzene, coke oven emis-
 sions, radionuclides, and vinyl chloride.
 Hazardous Ranking System:  The principle screening tool used by EPA to
 evaluate risks to public health and the environment associated with aban-
 doned or uncontrolled hazardous waste sites. The HRS calculates a score
 based on  the potential of  hazardous  substances  spreading  from the site
 through the air, surface water, or ground water and on other factors such as
 nearby population. This score is the primary factor in deciding if the site
 should be on the National Priorities List  and, if so, what ranking it should have
 compared to other sites on the list
 Hazardous Substance: 1. Any material that poses a threat to human health
 and/or the  environment. Typical hazardous substances are toxic, corrosive,
 ignitable, explosive, or chemically reactive. 2. Any substance named by EPA to
 be reported if a designated quantity of the substance is spilled in the waters of
 the United States or if otherwise emitted into  the environment.
 Hazardous Waste: By-products of society that can pose a substantial or poten-
 tial hazard  to human health or the environment when improperly managed.
 Possesses at least one of four characteristics (ignitability, corrosivity, reactiv-
 ity, or toxicity), or appears on special EPA lists.
 Hazards Analysis:  The procedures involved in  (1) identifying  potential
 sources of release of hazardous materials from fixed facilities or transportation
accidents; (2) determining the vulnerability of a geographical area to a release
of hazardous materials; and (3) comparing hazards to determine which pr-
esent greater or lesser risks to a community.
Hazards Identification: Providing information on  which facilities have ex-
tremely hazardous substances, what those chemicals are, and how much there
is at each facility. The process also provides information on how the chemicals
are 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.
 Heptachlor: 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-
 clear reactor, found at nuclear reactors or nuclear 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
 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
 Humus: Decomposed organic material.
 Hybrid:  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-
 Hydrocarbons (HC): Chemical compounds that consist entirely of carbon and
 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.
 Hydrogeology: 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.


 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 symptoms.
 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.
 Incineration: 1. Burning of certain types of solid, liquid, or gaseous materials.
 2. A treatment technology involving destruction of waste by controlled burn-
 ing at 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 for burning wastes under controlled conditions.
Indicator: In biology, an organism, species, or community whose characteris-
tics show the presence of specific environmental conditions.

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
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
Inertial Separator: A device that uses centrifugal force to  separate  waste
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 wastewater 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
Influent: Water, wastewater, or other liquid flowing into a reservoir, basin, or
treatment  plant.
Information 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 hall that is convenient for local
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.
Inoculum: 1. Bacterium placed in  compost  to start biological action.  2. A
medium containing organisms which is introduced into cultures or  living
Inorganic  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 (I/M): 1. Activities to assure proper emissions-
related operation of mobile sources of air pollutants, particularly automobile
emissions controls. 2. Also applies 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 (IPM): 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" permits.
Interstate  Carrier Water Supply: A source of water for drinking and sanitary
use on planes, buses, trains, and ships operating in more 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 surveillance 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 fn
wastewater during the electrodialysis process.
Ion Exchange Treatment: A common water softening method often found o
large scale at water purification plants that remove some organics and radii
by adding calcium oxide or calcium hydroxide to increase the pH to a le
where the metals will precipitate out.
lonization Chamber: A device that measures the intensity of ionizing rad
Ionizing Radiation: Radiation that can remove  electrons from atoms,  i
alpha, beta, and gamma radiation.
Irradiated Food: Food that has been subject to brief radioactivity, usually
gamma rays, to kill insects,  bacteria, and mold, and preserve it withe
refrigeration or freezing.
Irradiation: Exposure to radiation of wavelengths shorter than those of visil
light (gamma, x-ray, or ultraviolet), for medical purposes, the destruction
bacteria in milk or other foodstuffs, or for inducing polymerization of mono
ers or vulcanization of rubber.
Irrigation: Technique for applying water or wastewater to land areas to sup]
the water and nutrient needs of plants.
Isotope: A variation of an element that has the  same atomic number bu
different weight because of its neutrons. Various isotopes of the same elerru
may have different radioactive behaviors.

Kinetic Rate Coefficient: A number that describes the rate at which  a wal
constituent such as a biochemical oxygen demand or dissolved oxygen i
creases or decreases.
Lagoon: 1. A shallow pond where sunlight, bacterial action, and oxygen we
to purify wastewater; also used to storage of wastewaters or spent nuclear fi
rods. 2. Shallow body of water, often separated from the sea by coral reefs
Land Application: Discharge of wastewater onto the ground for treatment
reuse.  (See:  irrigation.)
Land Farming (of waste):  A disposal process  in which hazardous wa:
deposited on or in the soil is naturally degraded by microbes.
Landfills: 1. Sanitary landfills are land disposal sites for non-hazardous so
wastes at which the waste is spread  in layers, compacted  to the small<
practical volume, and cover material applied at the end of each operating di
2. Secure chemical landfills are disposal sites for hazardous waste. They £
selected and designed to minimize the chance of release of hazardous st
stances into the environment.
Lateral Sewers: Pipes that run under city streets and receive the sewage frc
homes and businesses.
LC 50/Lethal Concentration: Median level concentration, a standard measu
of toxicity. It tells how much of a substance is needed to kill half of a group
experimental organisms at a specific time of  observation. (See: LD 50.)
LD 50/ Lethal Dose: The dose of a toxicant that will kill 50 percent of the t(
organisms within a designated period of time. The lower the LD 50, the me
toxic the compound.
LD 0: The highest concentration of a toxic substance at which none of the tt
organisms die.
LD LO: The lowest concentration and dosage of a toxic substance which ki
test  organisms.
Leachate: A liquid that results from water collecting contaminants as it trick!
through wastes, agricultural pesticides, or fertilizers. Leaching may occur
farming areas, feedlots, and landfills, and may result in hazardous substanc
entering surface water, ground water, or soil.
Leachate Collection System: A system that gathers leachate and pumps it
the surface for treatment.
Leaching: The process by which soluble constituents are dissolved and carri
down through the soil by a percolating fluid. (See: leachate.)
Lead (Pb): A heavy metal that is hazardous to health if breathed or swallowe
Its use in gasoline, paints, and plumbing compounds has been sharply r«
tricted or eliminated by federal laws and regulations. (See: heavy metals.
Leaded Gasoline: Gasoline to which lead has been added to raise the octal

 Level of Concern (LOG): 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: In a sanitary landfill, a compacted layer of solid waste and the top layer of
 cover material.
 Lifting Station: (See: pumping station )
 Limestone Scrubbing:  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
 Limnology: The study of the physical, chemical, meteorological, and  biologi-
 cal aspects of fresh water.
 Liner: 1. A relatively impermeable barrier designed to prevent leachate from
 leaking from a landfill. Liner materials include plastic and dense clay. 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 of 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 Characteristics Listing Process because the dan-
 gers they present are considered self-evident.
 Local Emergency Planning Committee  (LEPC):  A committee appointed by
 the state emergency  response commission, as required by SARA Title III, to
 formulate a comprehensive emergency  plan for its jurisdiction.
 Lower Explosive Limit (LEL): The concentration of a compound in air below
 which a flame will not propagate if the mixture is ignited.
 Lowest Achievable 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, whichever  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 (LLRW):  Wastes less hazardous than  most of
 those generated by a nuclear reactor. Usually generated by hospitals, research
 laboratories, and certain industries.  The  Department of Energy, Nuclear Reg-
 ulatory Commission, and EPA share responsibilities for managing them. (See:
 high-level radioactive wastes.)

Major Modification:  This term is used to define modifications with respect to
Prevention of Significant Deterioration 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 Sources: Term  used to determine the applicability of
Prevention of Significant Deterioration and new source regulations. In a
nonattainment 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 cutoff level 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.
Marine Sanitation Device:  Any equipment installed on board a vessel to
receive, retain, treat, or discharge sewage and any process  to treat such
Marsh: 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..)

Material Safety Data Sheet (MSDS): A compilation of information required
under the OSHA 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-
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.
Media: Specific  environments—air, water, soil—which are the subject of
regulatory concern and activities
Mercury: A heavy metal that can accumulate in the enivronment and is highly
toxic if breathed or swallowed. (See: heavy metals.)
Metabolite: Any substance produced in or by biological processes and derived
from a pesticide.
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
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 (MGD): 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 organisms so small that individually they can usually
only be seen through a microscope.

Mist: Liquid particles measuring 40 to  500  microns, that are formed by con-
densation of vapor. By comparison, "fog" particles are smaller than 40 micro-
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, motorcycles, airplanes
Modeling: An investigative technique using a mathematical or physical repre-
sentation of a system or theory that accounts for all or some of 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: 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. (Also called
MABs and MCAs.)
Muck Soils: Earth made from decaying plant materials.
Mulch: A layer of material (wood chips, straw, leaves, etc.) placed around
plants to hold moisture, prevent weed growth, protect plants, and enrich soil.
Multiple Use: Use of land for more than one purpose; i.e., grazing of livestock,
wildlife production, recreation, watershed, and timber production. Could also
apply to use of bodies of water for recreational purposes, fishing, and water

 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 Discharge 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 NPL
 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 (NRT): 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 while those that do not adapt dis-
 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 compounctt>eing used to replace phosphates in
 Nitrite: 1. An intermediate in the process of nitrification. 2. Nitrous oxide salts
 used in food preservation
 Nitrogen Dioxide (NO2>: 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 significa
amounts of nitrogen.
Nitrogen Oxide (NOx):  Product of combustion from transportation an
stationary sources and a major contributor  to acid deposition and  tl
formation of ground level ozone in the troposphere.
Non-Attainment Area: Geographic area which does not meet one or more
the National Ambient Air Quality Standards for the criteria pollutants desi
nated in the Clean Air Act.
Non-Community Water System: A public water system that is not a commur
ty water system, e.g., the water supply at a camp site or national park.
Non-Conventional Pollutant: Any pollutant which is not statutorily listed
which is poorly understood by the  scientific community.
Non-ionizing Electromagnetic Radiation: 1. Radiation that does not chanj
the structure of atoms but does heat tissue and may cause harmful biologic
effects. 2. Microwaves, radio waves,  and low-frequency electromagnetic fiel(
from high-voltage transmission lines.
Non-Point Source: Pollution sources which are diffuse and do not have
single point of origin or are not introduced into a receiving stream from
specific outlet. The pollutants are generally carried off the land by stormwat
runoff. The commonly used categories for non-point sources are: agricultur
forestry, urban, mining, construction, dams and channels, land disposal, ar
saltwater intrusion.
Nuclear Power Plant: A facility that converts atomic energy into usable pow<
heat produced by a reactor makes  steam to drive turbines which produ
Nuclear Winter:  Prediction by some scientists that smoke and debris risii
from massive fires resulting from a  nuclear war could enter the atmosphe
and block out sunlight for weeks  or  months.  The scientists making tr
prediction project a cooling of the  earth's surface, and changes in  clima
which could,  for example, negatively affect world agricultural and weath
Nutrient: Any substance assimilated by living  things that promotes growt
The term is generally applied to nitrogen and phosphorus in wastewater, b
is also applied to other essential and trace elements.
Off-Site Facility: A hazardous waste treatment, storage, or disposal area th
is located at a place away from the generating site.
Oil Spill: An accidental or intentional discharge of oil which reaches bodies
water; can be controlled by chemical dispersion, combustion, mechanic
containment, and/or adsorption.
Oil Fingerprinting: A method that identifies sources of oil and allows spills
be traced back to their source.
Oligotrophic Lakes: Deep clear lakes with low nutrient supplies. They conta
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 D
partment of Defense official who coordinates and directs  Superfund remov
actions or Clean Water Act oil-or hazardous-spill corrective actions.
On-Site Facility: A hazardous waste treatment, storage, or disposal area th
is located on the generating site.
Opacity: The amount of light obscured by particulate pollution in the air; cle
window glass has zero opacity, a brick wall 100 percent opacity. Opacity
used as an indicator of changes in performance of particulate matter polluric
control systems.
Open Burning: Uncontrolled fires in an open dump.
Open Dump: An uncovered site used for disposal of waste without enviro
mental controls. (See: dump.)
Operable Unit: Term for each of a  number of separate activities undertaken
part of a Superfund  site cleanup.  A typical operable unit  would be removii
drums and tanks from the surface of a site.
Operation And Maintenance: 1. Activities conducted at a site after a Supt
fund site action is completed to ensure that the action is effective and operatii
properly. 2. Actions taken after  construction to assure that facilities co
structed to treat waste water will  be properly operated, maintained,  ar
managed to achieve efficiency levels and prescribed effluent limitations in<
optimum manner.
Organic: 1. Referring to or derived from living organisms.  2. In chemistry, ai
compound containing carbon.

Organic Chemicals/Compounds: Animal or plant-produced substances con-
taining mainly carbon, hydrogen, and oxygen.
Organic Matter: Carbonaceous waste contained in plant or animal matter and
originating from domestic or industrial sources.
Organism: Any living thing.
Organophosphates: Pesticide chemicals that contain phosphorus; used to
control insects. They are short-lived, but some can be toxic when first applied.
Organotins: 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.
Osmosis: 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
Overland Flow: A land application technique that cleanses 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 results in a uniformity of chemical and physical
properties of the water at all depths.
Oxidant: A substance containing oxygen that reacts chemically in air to pro-
duce a new substance. The primary 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-
ments. 3.  The process in chemistry whereby electrons  are removed from a
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.
Oxygenated Solvent: An organic solvent containing  oxygen as  part of the
molecular structure. Alcohols and ketones are oxygenated compounds often
used as paint solvents.
Ozonator: A device that adds ozone to water.
Ozone (O3): 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 which
provides a protective layer shielding the earth from ultraviolet radiation's
harmful health effects on humans and the environment. In the troposphere (the
layer extending up 7 to 10 miles from the earth's surface), ozone is a chemical
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 Clean 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
Ozone Depletion: Destruction of the stratospheric  ozone layer which shields
the earth from ultraviolet radiation harmful to biological life. This destruction
of ozone 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.
Packed 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 B Permit: (See Interim Permit Status.)
Paraquat: A standard herbicide used to kill various types of crops, including
Particulates: Fine liquid or solid particles  such as dust, smoke, mist, fumes, or
smog, 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
 ca,use serious illnesses.
 PCBs: A group of toxic, persistent chemicals (polychlorinated biphenyls) 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
 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
 injurious 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.
 pH: A measure of the acidity or alkalinity of a liquid or solid material.

 Phenols: Organic compounds that are byproducts 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
 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 Smog: 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
 wastewater 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.

Phytoplankton: 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.)

Pig: A container, usually lead, used to ship or store radioactive materials.
Pile: I. The fuel element in a nuclear 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 environment that
adversely affects the usefulness of a resource.
Pollutant Standard Index (PSD:  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 Clean 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 clump during sewage
Polymer: Basic molecular ingredients in plastic.
Polyvinyl Chloride (PVC): A tough, environmentally indestructible plastic
that releases hydrochloric  acid when burned.
Population: A group of interbreeding organisms of the same kind occupying a
particular space.  Genetically, the number of humans or other living creatures
in a designated area.
Post-Closure: The time period following the shutdown of a waste manage-
ment or manufacturing facility. For monitoring purposes, this is often consid-
ered to be 30 years.
Potable Water: Water that is safe for drinking and cooking.
Potentially Responsible Party (PRP): Any individual or company—including
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
clean up hazardous waste sites PRPs have contaminated.
PPM/PPB:    Parts per million/parts per billion,  a  way of expressing tiny
concentrations of pollutants in air, water, soil, human tissue, food, or  other
products.Radiobiology: The study of radiation effects on living things.
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-
Precipitators: Air pollution control devices that collect particles from an  emis-
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 Sewers: 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 publicly owned treatment works.
Prevention: Measures taken to minimize the release of wastes to the enviroi
Prevention of Significant Deterioration (PSD): EPA program in which sta
and/or federal permits are required that are intended to restrict emissions f
new or modified sources in places where air quality is already better th;
required to meet primary and secondary ambient air quality standards.
Primary Drinking Water Regulation:  Applies to public water systems at
specifies a contaminant level, which, in the judgement of the EPA Administr
tor, will have no adverse effect on human health.
Primary Waste Treatment:  First steps in wastewater treatment; screens ai
sedimentation tanks are used  to remove most  materials that float or w
settle. Primary  treatment results in the removal of  about  30  percent
carbonaceous biochemical oxygen demand from domestic sewage.
Process Weight:  Total weight of all materials, including fuel,  used  in
manufacturing process. It is used to calculate the allowable particulate emi
sion rate from the process.
Proteins: Complex nitrogenous organic compounds of high molecular weig
that contain amino acids as their basic unit and are essential for growth ar
repair of animal tissue. Many proteins are enzymes.
Protoplast: A membrane-bound cell from which the outer cell wall has bet
partially or completely removed. The term often is applied to plant cells.
Public Water System: A system that provides piped water for human  co
sumption to at least 15 service connections or regularly serves 25 individual:
Publicly Owned Treatment Works:  A waste-treatment works owned  by
state, unit of local  government, or Indian tribe, usually designed  to  tre
domestic wastewaters.
Pumping Station: Mechanical devices installed in sewer or water systems
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.

Quality Assurance/Quality Control: A system of procedures, checks, audit
and corrective actions to ensure that all EPA research design and performanc
environmental monitoring and sampling, and other technical and reportii
activities are of the highest achievable quality.
Quench Tank:  A water-filled  tank used to cool incinerator residues or h
materials during industrial processes.
RAD (Radiation Absorbed Dose): A unit of absorbed dose of radiation. Or
RAD of absorbed dose is equal to .01 joules per kilogram.
Radiation: Any form of energy propagated as rays, waves, or streams i
energetic particles. The term is frequently used in relation to the emission i
rays from the nucleus of an atom.
Radiation Standards:  Regulations that set maximum exposure limits f<
protection of the public from radioactive materials.
Radioactive Substances: Substances that emit radiation.
Radiobiology:  The study of  radiation effects on living things.
Radio Frequency Radiation:  (See Non-ionizing Radiation.)

Radionuclide: Radioactive element characterized according to its atomic mai
and atomic number which can be man-made or naturally occurring. They ca
have a long life as soil or water pollutants, and are believed to have potential
mutagenic effects on the human body.
Radius of Vulnerable Zone: The maximum distance from the point of releas
of a hazardous substance in which the airborne concentration could reach tti
level of concern under specified weather conditions.

Radon: A colorless,  naturally occurring, radioactive, inert  gaseous  elemei
formed by radioactive decay of radium atoms in soil or rocks.
Radon Decay Products:  A term used to refer collectively to the immedia
products of the radon decay chain. These include Po-218, Pb-214, Bi-214, ar
Po-214, which have an average combined half-life of about 30 minutes.

Rasp:  A machine that grinds waste into a manageable  material and  help
prevent odor.
Raw Sewage: Untreated wastewater.

 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  sources  in
 nonattainment areas and in  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.
 Recharge: The process by which water is added to a zone of saturation, usually
 by percolation 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
 effect 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 Source:  An existing facility in which components are replaced
 to such an extent that the fixed capital cost of the new components exceed 50
 percent 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 Border:  An EPA document that is undergoing final review before being
 submitted for final management decision.
 Red Tide: A proliferation of a marine plankton  that is toxic and often fatal  to
 fish. This natural phenomenon may be stimulated by the addition of nutrients.
 A tide can be called red, green, or brown, depending on the coloration of the
 Reentry Interval: 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 Reclamation:  Conversion of solid  waste  into useful products, e.g.,
 composting organic wastes to  make soil conditioners or separating aluminum
 and  other metals for melting and  recycling.
 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.
 Registrant: Any manufacturer  or formulator who obtains registration for a
 pesticide active ingredient or  product.
 Registration: 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 Act. 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 person or a part of a  human has been  exposed.
Remedial Action (RA):  The actual construction or  implementation phase of a
Superfund site cleanup that follows remedial design.
Remedial Design: A phase of remedial action that follows the remedial
investigation/feasibility study and includes development of engineering
drawings and specifications for a site cleanup.
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/FS".
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 trig-
gers reports under CERCLA. If a substance is released in amounts exceeding
its RQ, the release must be reported to the National Response Center, the State
Emergency Response Commission, 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 other pollutant  removal process.
 Resistance: For plants and animals, the ability to withstand poor environmen-
 tal conditions and/or attacks by chemicals or disease. The ability may be inborn
 or  developed.
 Resource: A person, thing, or action needed  for living or to improve the
 quality of life.
Response Action: A CERCLA-authonzed 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 Recovery: 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
Restriction Enzymes: Enzymes that recognize certain specific regions of a 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.
Ribonucleic 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  illustrations  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 specific pollutants
Risk Communication: The exchange of information about health or environ-
mental risks between risk assessors, risk managers, the general public,  news
media, interest groups, etc.

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 game 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
Salvage: The utilization of waste materials.
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.
Sanitation: Control  of physical factors in the human environment that could
harm development, health, or  survival.
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.
Sedimentation: Letting solids settle  out of wastewater by gravity during
wastewater treatment.
Sedimentation Tanks:  Holding areas for wastewater where floating wastes
are skimmed off and settled solids are removed for disposal.
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 readi aquatic plants. Careless farming, mining, and build-
ing activities will expose sediment materials, allowing them to be washed off
the land after rainfalls.
Selective Pesticide: A chemical designed to affect only certain types of pes
leaving other plants and animals unharmed.
Semi-Confined Aquifer: An aquifer that is partially confined by a soil layer (
layers) of low permeability through which recharge and discharge can occu
Senescence: Term for the aging process. Sometimes used to describe lakes
other bodies of water in advanced stages of eutrophication.
Septic Tank: An underground storage tank for wastes from homes having i
sewer line to a treatment plant. The waste goes directly from the home to tl
tank, where the organic waste is decomposed by bacteria and the slud;
settles to the bottom. The effluent flows out of the tank into the groui
through drains, the sludge is pumped out periodically.
Service Connector: The pipe that carries tap water from the public water ma
to a building.
Settleable Solids: Material heavy enough to sink to the bottom of a wastewat
treatment tank.
Settling Chamber: A series of screens placed in the way of flue gases to sic
the stream of air, thus helping gravity to pull particles out of the emission in
a collection area.
Settling Tank: A holding area for wastewater, where heavier particles sink
the bottom for removal and disposal.
Sewage: The waste and wastewater produced by residential and commerc
establishments and discharged into sewers.
Sewage Lagoon: (See: lagoon.)
Sewage Sludge: Sludge produced at a Publicly Owned Treatment Works, tl
disposal of which is regulated  under  the Clean Water Act
Sewer: A channel or conduit that carries wastewater and storm water rum
from the source to a treatment plant or receiving stream. Sanitary sewers car
household, industrial, and commercial waste. Storm sewers carry runoff fro
rain  or snow. Combined sewers are used for both purposes.
Sewerage: The entire system of sewage collection, treatment, and  disposa
Shotgun: Non-scientific term for the process of breaking up the DNA deriv
from an organism and then moving each separate and unidentified DIX
fragment into a bacterium
Signal Words: The  words used  on a pesticide label—Danger,  Warnin
Caution—to indicate the level of toxicity of the chemicals.
Significant Deterioration: Pollution resulting from a new source in previous
"clean"  areas. (See: prevention of significant deterioration.)
Significant Municipal Facilities: Those publicly owned sewage  treatme
plants that discharge a million gallons per day or  more and  are therefo
considered by states to have the potential for substantial effect on the quality
receiving waters.
Significant Violations: Violations by point source dischargers of sufficie
magnitude and/or duration to be a regulatory priority.
Silt: Fine particles of sand or rock that can be picked up by the air or water ai
deposited as  sediment.
Silviculture: Management of forest land for timber; sometimes contributes
water pollution, as in clear-cutting.
Sinking: Controlling oil spills by using an agent to trap the oil and sink it to tl
bottom  of the body of water where the agent and the oil are biodegradec
Site Inspection: The collection of information from a Superfund site to d
termine the extent and severity of hazards posed by the site It follows and
more extensive  than a preliminary assessment. The purpose is  to  gath
information necessary to score the site, using the Hazard Ranking System, ai
to determine if the site presents an immediate threat that requires prom
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 tl
Slow Sand Filtration: Treatment process involving passage of raw wat
through a bed of sand at low velocity which results in the substantial remo\
of chemical and biological contaminants.
Sludge: A semi-solid residue from any of a number of air or water treatme
processes. Sludge can be a hazardous waste.
Slurry:  A watery mixture of insoluble matter that results from some pollutii
control  techniques.
Smelter: A facility that melts or fuses ore, often with an accompanying chei
ical  change, to separate the metal. Emissions are known to cause pollutio
Smelting is the process involved.

 Smog: Air 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 Field: A sub-surface area containing a trench or bed with
 clean stones and a system of distribution piping through which treated sewage
 may seep into the surrounding soil for further treatment and disposal
 Soil Conditioner: An organic material like humus or compost that helps soil
 absorb water, build a bacterial community,  and distribute nutrients and
 Soil Gas: Gaseous 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.
 Solder: A metallic compound used to seal the joints between pipes  Until
 recently, most solder contained 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-
 bage 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 Disposal: The final placement  of refuse that is not salvaged  or
 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.
 Sorption: The action of soaking up or attracting substances; a process used in
 many pollution control systems.
 Special Review: Formerly known as Rebuttable Presumption Against Regis-
 tration (RPAR), this is the regulatory process through which existing pesti-
 cides 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 risk/benefit analysis with opportunity for public com-
 ment. If the risk of any use of a pesticide is found to outweigh social and
 economic benefits, regulatory actions—ranging from label revisions and use-
 restriction to cancellation or suspended registration—can be initiated.
 Species: A reproductively isolated aggregate of interbreeding populations of
 Spill Prevention Control and Countermeasures Plan  (SPCC): Plan covering
 the release of hazardous substances as defined in the Clean Water Act
 Sprawl: Unplanned development of open land.
 Spoil: Dirt or rock that has been removed from its original location, destroying
 the composition of the soil in the process, as with strip-mining or dredging.
 Stabilization: Conversion of the active organic matter in sludge into inert,
 harmless material.
 Stabilization Ponds: (See: lagoon.)
 Stable Air: 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 Gas: (See: flue gas.)
 Stagnation: Lack of motion in a mass of air or water, which tends to hold
 Standards: Prescriptive norms which govern action and actual limits on the
amount of pollutants or emissions produced. EPA, under most of its responsi-
bilities, establishes minimum standards.  States are allowed to be stricter.
 State  Emergency Response  Commission (SERC): Commission appointed by
 each state governor  according to the requirements of SARA Title III. The
 SERCs designate emergency planning  districts, appoint local emergency
 planning committees, and supervise and coordinate their activities.
 State Implementation Plans (SIP): 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 dispcsal. 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.
 Strip-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  (SO2>: A heavy,  pungent, colorless, gaseous air pollutant
 formed primarily by industrial fossil  fuel combustion processes.
 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.); also refers  to
 springs, wells, or  other collectors which are directly influenced by surface
 Surfactant: A  surface-active agent used in detergents to cause lathering.
 Surveillance System: A series of monitoring devices designed to determine
 environmental quality.
 Suspended Solids: Small particles 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
 Suspension Culture: Individual cells or small clumps  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 may be 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
 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.
Tailings: Residue of raw materials or waste separated out during the process-
ing of crops or mineral ores.
TBT Paints (Trybutilin): (See: organotins )
Technology-Based Standards: Effluent limitations applicable to  direct and
indirect sources which are developed on a category-by-category basis using
statutory factors, not including water-quality effects.


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 exposed daily 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 III.
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 Chemical Release Form: 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 PolIutantsiMaterials contaminating the environment that cause death,
disease, and/or birth defects in organisms that ingest or absorb them. The
quantities and length of exposure necessary to cause these effects can vary
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
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.
Trichloroethylene  (TCE): A stable, low-boiling colorless liquid, toxic by in-
halation. TCE is used  as a solvent, metal degreasing agent, and in other
industrial applications.
Trickling Filter: A coarse, biological treatment system in which wastewater is
trickled over a bed of stones or other material covered with bacterial growth.
The bacteria break down the organic waste in the sewage and produce clean
Trihalomethane (THM): One of a family of organic compounds, named as
derivatives of methane. THM's are generally the byproduct 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 clouds are formed.
Trust Fund (CERCLA): A fund set up under the Comprehensive Environmen-
tal Response,  Compensation, and Liability  Act (CERCLA) to help pay for
cleanup of hazardous waste sites and for legal action to force those responsi
for the sites to clean them up.

Tundra: A type of ecosystem dominated by lichens, mosses, grasses, a
woody plants. Tundra is found at high latitudes  (arctic tundra) and hi
altitudes (alpine tundra). Arctic tundra is underlain by permafrost and
usually very wet. (See: wetlands.)
Turbidimeter: A device that measures the amount of suspended solids n
Turbidity: 1. Haziness in air caused by the presence of particles and poll
ants. 2. A similar cloudy condition in waler due to suspended silt or orgai


Ultra Clean Coal (UCC): Coal that has been washed, ground into fine pa
cles, then chemically treated to remove sulfur, ash, silicone, and other s
stances; usually briquetted and coated with a sealant made from coal.
Ultraviolet Rays: Radiation from  the sun that can be  useful or potenti<
harmful. UV rays from one part of the spectrum enhance plant life and
useful in some medical and dental procedures; UV rays from other parts of
spectrum to which humans are exposed  (e.g., while getting a sun tan)
cause skin cancer or other tissue damage.  The ozone layer in the atmosph
provides a protective shield that limits the amount of ultraviolet rays that re
the Earth's surface.
Underground Injection Control (UIC): The program under the Safe Drink
Water Act that regulates the use of wells to pump fluids into the grouni
Underground Sources of Drinking Water: As defined  in the UIC progr;
this term refers to aquifers that are currently being used as a source of drink
drinking water, and those that are capable of supplying a public water syst<
They have a total dissolved solids content of 10,000 milligrams per liter or It
and are not "exempted aquifers." (See: exempted aquifer.)
Underground Storage Tank: A tank located all or partially under ground t
is designed to hold gasoline or other petroleum products or chemical sc
Unsaturated Zone: The area above the water table where the soil pores are
fully saturated, although some water may be present.
Uranium: A radioactive heavy metal element used in nuclear reactors and
production of nuclear weapons. Term refers usually to U-238, the most ab
dant radium isotope, although a small percentage of naturally occurring t
nium is U-235.
Urban Runoff:  Storm water from city streets and adjacent domestic or cc
mercial properties that may carry  pollutants of various kinds into the sei
systems and/or receiving waters.
 Vaccine: Dead, partial, or modified antigen used to induce immunity
 certain infectious diseases.

 Vapor: The gaseous phase of substances that are liquid or solid at atmosphi
 temperature and pressure, e.g., steam.
 Vapor Capture System: Any combination of hoods and ventilation system t
 captures or contains organic vapors in order that they may be directed to
 abatement or recovery device.
 Vapor Dispersion: The movement of vapor clouds in air due to wind, grai
 spreading, and mixing.
 Vapor Plumes: Flue gases that are visible because they contain water drople
 Vaporization: The change of  a substance  from a liquid to a gas.
 Variance: Government permission for a delay or exception in the applicat
 of a given law, ordinance, or regulation.
 Vector: 1. An organism, often an insect or rodent, that carries disease. 2.
 object that is used to transport genes into a host cell (vectors can be plasmi
 viruses, or other bacteria). A gene is placed in the  vector; the vector tl
 "infects" the bacterium.
 Ventilation/Suction: The act  of admitting fresh air into a space in orde
 replace stale  or contaminated air; achieved by blowing air into the sp;
 Similarly, suction represents the admission of fresh air into an interior sp
 by lowering the pressure outside  of the space, thereby drawing the c
 taminated air outward.
 Vinyl Chloride: A chemical compound, used in producing some plastics, t
 is believed to be carcogenic.
 Virus: The smallest form of microorganisms  capable of causing disease
 Volatile: Description of any substance that evaporates readily.

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 Chemicals: Chemicals that tend to volatilize or
evaporate from water.
Vulnerability Analysis: Assessment of elements in the community that are
susceptible to damage should a release of hazardous 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.

Waste:  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 for each specific water quality criterion being, or expected to
be, violated.
Waste Treatment Plant: A facility containing a series of tanks, screens, filters,
and other processes by which pollutants are removed from water.

Waste Treatment Stream: The continuous movement of w,. ste from generator
to treater and disposer.
Wastewater: The spent or used water from individual homes, a community, a
farm, or an industry that contains dissolved or suspended matter.
Wastewater Operations and Maintenance: Actions taken after construction to
assure that facilities constructed to treat wastewater will be properly operated,
maintained, and managed to achieve efficiency levels and  prescribed effluent
levels in an optimum manner.
Water Pollution: The presence in water of enough harmful or objectionable
material to damage the water's quality
Water Quality Criteria: Specific levels of water quality which, if reached, are
expected to 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 industrial proc-
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
water quality criteria which must be met to protect the designated use or uses
Watershed: The land area that drains into a stream.
Water Supplier: 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 Solubility: 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 polycyclic
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.

X, Y, Z
Xenobiotic: 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.

AA: Adverse Action
AA:  Advices of Allowance
AA: Assistant Administrator
AA: Associate Administrator
AA: Atomic Absorption
AAAS: American Association for the Advance-
  ment of Science
AAEE: American Academy of Environmental En-
AANWR:  Alaskan Arctic National Wildlife Refuge
AAP: Affirmative Action Plan
AAP: Affirmative Action Program
AAP: Asbestos Action Program
AARC: Alliance for Acid Rain Control
ABES: Alliance for Balanced Environmental Solu-
AC: Actual Commitment
AC: Advisory Circular
AC: Alternating Current
A&C: Abatement and Control
ACA: American Conservation Association
ACBM: Asbestos-Containing Building Material
ACE: Alliance for Clean Energy
ACEEE: American Council for an Energy Efficient
ACFM: Actual Cubic Feet Per Minute
ACL: Alternate Concentration Limit
ACL: Analytical Chemistry Laboratory
ACM: Asbestos-Containing Material
ACP: Air Carcinogen Policy
ACQUIRE: Aquatic Information Retrieval
ACQR: Air Quality Control Region
ACS: American Chemical Society
ACT: Action
ACTS: Asbestos Contractor Tracking System
ACWA: American Clean Water Association
ADABA: Acceptable Data Base
ADB: Applications Data Base
ADI: Acceptable Daily Intake
ADQ: Audits of Data Quality
ADR: Alternate Dispute Resolution
ADSS: Air Data Screening System
ADT: Average Daily Traffic
AEA: Atomic Energy Act
AEC: Associate Enforcement Counsels (OECM)
AEE: Alliance for Environmental Education
AEERL: Air  and Energy  Engineering Research
AEM: Acoustic Emmision Monitoring
AERE: Association of Environmental and Re-
  source Economists
AES: Auger Electron Spectometry
AFCA: Area Fuel Consumption Allocation
AFRCE: Air Force Regional Civil Engineers
AFS: AIRS Facility Subsystem
AFUG: AIRS Facility Users Group
AGC: Associate General Counsels (OGC)
AH: Allowance Holders
AHERA: Asbestos Hazard Emergency Response
AI: Artificial Intelligence
AICE: American Institute of Chemical Engineers
AICUZ: Air Installation Compatible Use Zones
AID: Agency for International Development
AIG: Assistant Inspector General
AIHC: American Industrial Health Council
AIP: Auto Ignition Point
AIRS: Aerometric Information Retrieval System
AL: Acceptable Level
AL: Administrative Leave
AL: Annual Leave
ALA: American Lung Association
ALA: Delta-Aminolevulinic Acid
ALA-O: Delta-Aminolevulinic Acid Dehydrates
ALAPO: Association of Local Air Pollution Con-
  trol Officers
ALARA: As Low As Reasonably Achievable
ALC: Application Limiting Constituent
ALJ: Administrative Law Judge
ALMS: TALMS without the tunable
ALR: Action Leakage Rate
AMA: American Medical Association
AMBIENS: Atmospheric Mass Balance  of In-
  dustrially Emitted and Natural Sulfur (ex-,
  perimental investigation by the MAP3S Com-
AMPS: Automatic Mapping and Planning System
AMS: American Meteorological Society
AMSA: Association of Metropolitan Sewer Agen-
ANPR: Advance Notice of Proposed Rulemaking
ANSS: American Nature Study Society
AO: Administrative Officer
AO: Administrator's Office
AO: Administrative Order (on consent)
AO: Area Office
AO: Awards and Obligations
AOC: Abnormal Operating Conditions
AOD: Argon-Oxygen Decarbonization
AOML: Atlantic Oceanographic and Meteorlogi-
  cal Laboratory
AP: Accounting Point
APA: Administrative Procedures Act
APCA: Air  Pollution Control Association
APCD: Air  Pollution Control District
APDS: Automated  Procurement Documentation
APHA: American Public Health Association
APRAC: Urban Diffusion Model for  Carbon
  Monoxide from Motor Vehicle Traffic
APT: Associated Pharmacists and Toxicologists
APTI: Air Pollution Training Institute
APWA: American Public Works Association
AQ-7: Non-reactive Pollutant Modeling
AQCCT: Air Quality Criteria and Control Tech-
AQCR: Air  Quality Control Region  (CAA)
AQD: Air Quality Digest
AQDHS: Air Quality Data  Handling System
AQDM: Air Quality Display Model
AQMA: Air Quality Maintenance Area
AQMP: Air Quality Maintenance Plan
AQMP: Air Quality Management Plan
AQSM: Air Quality Simulation Model
AQTAD: Air Quality  Technical  Assistance
A&R: Air and Radiation
ARA: Assistant Regional Administrator
ARA: Associate Regional Administrator
ARAR: Applicable or Relevant and Appropriate
  Standards, Limitations, Criteria, and Require-
ARB: Air Resources Board
ARC: Agency Ranking Committee
ARCC: American Rivers Conservation Council
ARG: American Resources Group
ARIP: Accidental Release Information Program
ARL: Air Resources Laboratory
ARM: Air Resources Management
ARO: Alternate Regulatory Option
ARRP: Acid Rain Research Program
ARRPA: Air Resources Regional Pollution Assess-
  ment Model
ARZ: Auto-restricted Zone
AS: Area Source
ASC: Area  Source Category
ASCII: American Standard Code for Information
ASDWA: Association of State Drinking Water Ad-
ASHAA: Asbestos in Schools Hazard Abatement
ASIWCPA: Association of State and Interstat
 Water Pollution Control Administrators
ASMDHS: Airshed Model Data Handling Systei
ASRL: Atmospheric Sciences Research Laboratoi
ASTHO: Association  of State and  TerritoriE
   Health Officers
ASTSWMO: Association of State and Territor
   Solid Waste Management Officials
AT: Advanced Treatment (water)
ATERIS: Air Toxics Exposure  and Risk Inform
  tion System (ORD)
ATS: Action Tracking System
ATS: Administrator's Tracking System
ATSDR: Agency for Toxic Substances and Disea
  Registry (HHS)
ATTF: Air Toxics Task Force
AUSA: Assistant United States Attorney
AUSM: Advanced  Utility Simulation  Model
A/WPR: Air/Water  Pollution Report
AWRA: American Water Resources Associatio1
AWWA: American  Water Works Association
AWWARF: American  Water Works  Associate
   Research Foundation
AX:  Adminislrator's Office

BAA: Board of Assistance Appeals (OGC)
BAC: Biotechnology Advisory Committee
BACT: Best Available Control Technology
BADT: Best Available Demonstrated Technoloj
BaP: Benzo(a)Pyrene
BAP: Benefits Analysis Program
BART: Best Available Retrofit Technology
BASIS: Battelles Automated Search Informatii
BAT: Best Available Treatment
BATEA: Best Available Technology Economica
BBS: Bulletin Board System
BCC: Blind Carbon Copy
BCCM: Board for Certified Consulting Meteo
BCT: Best Control Technology
BCT: Best Conventional Pollutant Control Te
BDAT: Best Demonstrated Achievable Technc
BDT: Best Demonstrated Technology
BEJ: Best Expert Judgment
BEP: Black Employment Program
BG: Billion Gallons
BI: Brookings Institution
BIA: Bureau of Indian Affairs
BID: Background Information Document
BID: Buoyancy Induced Dispersion
BIOPLUME: Model to Predict the Maximum
  tent of Existing Plumes
BLM: Bureau of Land Management:
BLOB: Biologically Liberated Organo-Beasties
BLS: Bureau of Labor Statistics
BMP: Best Management Practice(s)
BMR: Baseline Monitoring Report (CWA)
BOD: Biochemical Oxygen Demand
BOD: Biological Oxygen Demand
BOF: Basic Oxygen  Furnace
BOM: Bureau of Mines
BOP: Basic O'xygen Process
BOPF: Basic Oxygen Process Furnace
BOYSNC: Beginning of Year  Significant N
BP: Boiling Point
BPA: Blanket Purchase Agreement
BPJ: Best Professional Judgment
BPT: Best Practicable Technology
BPT: Best Practicable Control Technology
BPT: Best Practicable Treatment

BRS: Bibliographic Retrieval Service
BSO: Benzene Soluble Organics
BTU: British Thermal Unit
BTZ: .Below the Treatment Zone
BU: Bargaining Unit
BUN: Blood Urea Nitrogen
BY: Budget Year
C: Celsius
CA: Citizen Act
CA: Competition Advocate
CA: Cooperative Agreements
CA: Corrective Action
CAA: Clean Air Act
CAA: Compliance Assurance Agreement
CAAA: Clean Air Act Amendments
CAB: Civil Aeronautics Board
CAD: Computer Assisted Design
CAER: Community Awareness and  Emergency
CAFE: Corporate Average Fuel Economy
CAFO: Consent Agreement/Final Order
CAG: Carcinogenic Assessment Group
CAIR: Comprehensive Assessment of Informa-
  tion Rule
CALINE: California Line Source Model
CAMP: Continuous Air Monitoring Program
CAN: Common Account Number
CAO: Corrective Action Order
CAP: Corrective Action Plan
CAP: Cost Allocation Procedure
CAP: Criteria Air Pollutant
CAR: Corrective Action Report
CAS: Center for Automotive Safety
CAS: Chemical Abstract Service
CASAC: Clean Air Scientific Advisory Committee
CASLP: Conference on Alternative State and Local
CATS: Corrective Action Tracking  System
CAU: Carbon Adsorption Unit
CAU: Command Arithmetic Unit
CB: Continuous Bubbler
CBA: Chesapeake Bay Agreement
CBA: Cost Benefit Analysis
CBD: Central Business District
CBD: Commerce Business Daily
CBI: Compliance Biomonitoring  Inspection
CBI: Confidental Business Information
CBO: Congressional Budget Office
CBOD: Carbonaceous Biochemical Oxygen De-
CBP: Chesapeake Bay Program
CBP: County Business Patterns
CC:  Carbon Copy
CCA: Competition in Contracting Act
CCAA: Canadian Clean Air Act
CCAP: Center for Clean Air Policy
CCEA: Conventional Combustion Environmental
CCHW: Citizens Clearinghouse for Hazardous
CCID: Confidential Chemicals Identification
CCMS/NATO  : Committee on Challenges of a
  Modern Society/North. Atlantic Treaty Organ-
CCP: Composite Correction Plan (CWA)
CC/RTS:  Chemical Collection/Request Tracking
CCTP: Clean Coal Technology Program
CD: Climatological Data
CDB: Consolidated Data Base
CDBA: Central Data Base Administrator
CDC: Centers for Disease Control (HHS)
CDD: Chlorinated dibenzo-p-dioxin
CDF: Chlorinated dibenzofuran
CDHS: Comprehensive Data Handling System
CDI: Case Development Inspection
CDM: Climatological Dispersion Model
CDM: Comprehensive Data Management
CDMQC: Climatological Dispersion Model with
  Calibration and Source Contribution:
CDNS: Climatological Data National Summary
CDP: Census Designated Places
CDS: Compliance Data System
CE: Categorical Exclusion
CE: Cost Effectiveness
CEA: Cooperative Enforcement Agreement
CEA: Cost and Economic Assessment (OECM)
CEA: Council of Economic Advisors
CEAT: Contractor Evidence Audit Team
CEARC: Canadian Environmental Assessment
  Research Council
CEB: Chemical Element Balance
CEC: Commission of European Communities
CECATS: CSB Existing Chemicals Assessment
 Tracking System (OPTS)
CEE: Center for Environmental Education
CEEM: Center for  Energy and Environmental
CEI: Compliance Evaluation Inspection (CWA)
CELRF: Canadian Environmental  Law Research
CEM: Continuous Emission Monitoring (CAA)
CEMS: Continuous Emission Monitoring System
CEO: Chief Executive Officer
CEPP: Chemical Emergency Preparedness Plan
CEQ: Council on Environmental Quality
CERCLA: Comprehensive Environmental Re-
  sponse, Compensation, and Liability Act of 1980
CERCLIS: Comprehensive Environmental Re-
  sponse, Compensation, and Liability Informa-
  tion System (OSWER)
CERI: Center for  Environmental Research In-
CERT: Certificate of Eligibility
CEU: Continuing Education Units
CF: Conservation Foundation
CFA: Consumer Federation of American
CFC: Chlorofluorocarbons
CFM: Chlorofluoromethanes
CFM: Cubic Feet Per Minute (ft. 3/min. preferred
  except with ACFM or SCFM)
CFR: Code  of Federal Regulations
CFS: Cubic feet per second
CHABA: Committee on Hearing  and Bio-
CHAMP: Community Health Air Monitoring Pro-
CHEMTREC: Chemical Transportation Emergen-
  cy Center
CHESS: Community Health  and Environmental
  Surveillance System
CHIP: Chemical Hazard Information Profile
CI: Compression Ignition
CI: Confidence Interval
CIAQ: Council on Indoor Air Quality
CIBL: Convective Internal Boundary Layer
CICA: Competition in Contracting Act
CICIS: Chemicals in Commerce Information Sys-
CIDRS: Cascade Impactor Data Reduction System
CIMI: Committee on Integrity and Management
CIS: Chemical Information System
CIS: Contracts Information System
CJE: Critical Job Element
CJO: Chief Judicial Officer
CLC: Capacity Limiting Constituents
CLEANS: Clinical Laboratory for Evaluation and
 Assessment of Toxic Substances
CLEVER: Clinical Laboratory for Evaluation and
 Validation of Epidemiologic Research
CLF: Conservation Law Foundation
CLIPS: Chemical List Index  and Processing
CLP: Contract Laboratory Program
CM: Corrective Measure
CMA: Chemical Manufacturers Association
CMB: Chemical Mass Balance
CME: Comprehensive (ground water) Monitoring
CMEL: Comprehensive (ground water) Monitor-
 ing Evaluation Log
CMEP: Critical Mass Energy Project
COCO: Contractor-Owned/Contractor-Operated
COD: Chemical Oxygen demand
COE: U.S. Army Corps of Engineers
COH: Coefficient of Haze
CONG: Congressional Committee
CPF: Carcinogenic Potency Factor
CPI: Consumer Price Index
CPO: Certified Project Officer
CPR: Center for Public Resources
CPSC: Consumer Product  Safety Commission
CQA: Construction Quality Assurance
CR: Community Relations
CROP: Consolidated Rules of Practice
CRR: Center for Renewable Resources
CRS: Congressional Research Service
CRSTER: Single Source Dispersion Model
CSI: Clean Sites, Inc.
CSI: Compliance Sampling Inspection (CWA)
CSIN: Chemical Substances Information Network
CSMA: Chemical Specialties  Manufacturers
CSO: Combined Sewer Overflow
CSPA: Council of State Planning Agencies
CSPI: Center for Science in the Public Interest
CSRL: Center for the  Study of Responsive Law
CTARC: Chemical Testing and Assessment  Re-
  search Commission
CW: Congress Watch
CWA: Clean Water Act (aka FWPCA)
CWAP: Clean Water Action Project
CWTC: Chemical Waste Transportation Council
DA: Deputy Administrator
DAR: Defense Acquisition Regulations
dB: Decibel
DCA: Document Control Assistant
DCO: Delayed Compliance Order (CAA)
DCO: Document Control Officer
DDT: D(Ichloro)D(Iphebyl)T(Richloroethane)
DES: Diethylstilbesterol
DI: Diagnostic Inspection (CWA)
DMR: Discharge Monitoring Report
DNA: Deoxyribonucleic acid
DO: Dissolved Oxygen
DOC: Department of Commerce
DOD: Department of Defense
DOE: Department of Energy
DOI: Department of Interior
DOJ: Department of Justice
DOL: Department of Labor
DOS: Department of State
DOT: Department of Transportation
DOW: Defenders of Wildlife
DPA: Deepwater Ports Act
DQO: Data Quality Objective
DRA: Deputy Regional Administrator
DRC: Deputy Regional Counsel
DRMS: Defense Reutilization and Marketing Ser-
DS: Dichotomous Sampler
DSAP: Data Self Auditing Program

DSCF: Dry Standard Cubic Feet
DSCM: Dry Standard Cubic Meter
DSS: Decision Support System
DSS: Domestic Sewage Study
DT: Detention Time
DU: Decision Unit
DU: Ducks Unlimited
DUC: Decision Unit Coordinator:
DWS: Drinking Water Standard
EA: Endangerment Assessment
EA: Enforcement Agreement
EA: Environmental Action
EA: Environmental Assessment (NEPA)
EA: Environmental Audit
EAF: Electric Arc Furnaces
EAG: Exposure Assessment Group (ORD)
EAP: Environmental Action Plan
EAR: Environmental Auditing Roundtable
EB: Emissions Balancing
EBCDIC: Extended Binary Coded Decimal Inter-
  change Code
EC: European Community (Common Market)
EC: Environment Canada
EC: Effective Concentration
ECA: Economic Community for Africa
ECAP: Employee Counseling and Assistance Pro-
BCD: Electron Capture Detector
ECE: Economic Commission for Europe
ECHH: Electro-Catalytic Hyper-Heaters
ECL: Environmental Chemical Laboratory
ECL: Executive Control Language
ECLA: Economic Commission for Latin America
ECRA: Economic Cleanup Responsibility Act
ED: Department of Education
ED: Effective Dose
EDA: Economic Development Administration
EDA: Emergency Declaration Area
EDB: Ethylene Dibromide
EDC: Ethylene Dichloride:
EDD: Enforcement Decision Document
EDF: Environmental Defense Fund
EDP: Electronic Data Processing
EDRS: Enforcement Document Retrieval System
EDS: Electronic Data System
EDS: Energy Data  System
EDT: Edit Data Transmission
EDTA: Ethylene Diamine Triacetic Acid
EDZ: Emission Density Zoning
EEA: Energy and Environmental Analysis
EEC: European Economic Commission
EEG: Electroencephalogram
EEI: Edison Electric Institute
EENET: Emergency Education Network (FEMA)
EEOC: Equal Employment Opportunity Commis-
EER: Excess Emission Report
EERL: Eastern Environmental Radiation Labora-
EERU: Environmental Emergency Response Unit
EESI: Environment and Energy Study Institute
EESL: Environmental Ecological and Support Lab-
EETFC: Environmental Effects, Transport  and
  Fate Committee
EF: Emission Factor
EFO: Equivalent Field Office
EFTC: European Fluorocarbon Technical Com-
EGR: Exhaust Gas Recirculation
EH: Redox Potential
EHC: Environmental Health Committee (SAB)
EHS: Extremely Hazardous Substance
El: Emissions Inventory
EIA: Economic Impact Assessment
EIA: Environmental Impact Assessment
EIL: Environmental Impairment Liability
EIR: Endangerment Information Report
EIR: Environmental Impact Report
EIS: Environmental Inventory System
EIS: Environmental Impact Statement (NEPA)
EIS/AS: Emissions Inventory System/Area Source
EIS/PS: Emissions Inventory System/Point Source
EKMA: Empirical Kinetic Modeling Approach
EL: Exposure Level
ELI: Environmental Law Institute
ELR: Environmental Law Reporter
EM: Electromagnetic Conductivity
EM: Electron Microscope
E-MAIL: Electronic Mail
EMAS: Enforcement Management and Account-
  ability System (OECM)
EMI: Emergency Management Institute
EMR: Environmental Management Report
EMS: Enforcement Management System
EMSL: Environmental Monitoring Support Lab-
EMSL: Environmental Monitoring Systems Lab-
EMTS: Environmental Monitoring Testing Site
EMTS: Exposure Monitoring Test Site
EO: Ethylene Oxide
EO: Executive Officer
EO: Executive Order
BOB: Executive Office Building
EOC: Emergency Operating Center
EOD: Entrance on Duty
EOE: Equal Opportunity Employer
EOJ: End of Job
EOF: Emergency Operations Plan
EOT: Emergency Operations Team
EOY: End of Year
EP: Earth Protectors
EP: Environmental Profile
EP: Extraction Procedure
EPA: U.S. Environmental Protection Agency
EPAA: Environmental Programs Assistance Act:
EPAAR: EPA Acquisition Regulations
EPACASR:  EPA Chemical Activities Status Report
EPAYS: EPA Payroll System

EPD: Emergency Planning  District
EPI: Environmental Policy  Institute
EPIC: Environmental Photographic Interpretation
EPNL: Effective Perceived  Noise Level
EPO: Estuarine Programs Office (NOAA)
EPRI: Electric Power Research Institute
EPTC: Extraction Procedure Toxicity Characteris-
ER: Electrical Resistivity
ERA: Economic Regulatory Agency
ERAMS: Environmental  Radiation Ambient
  Monitoring System (OAR)
ERC: Emergency Response Commission
ERC: Emissions Reduction Credit
ERC: Environmental Research Center
ERCS: Emergency Response Cleanup Services
ERDA: Energy Research and  Development Ad-
ERD&DAA: Environmental Research, Develop-
  ment and  Demonstration Authorization Act
ERL: Environmental Research Laboratory
ERNS: Emergency Response Notification System
ERP: Enforcement Response Policy
ERT: Emergency Response Team
ERTAQ: ERT Air Quality Model
ES: Enforcement Strategy
ESA: Endangered Species  Act
ESA: Environmentally Sensitive Area
ESC: Endangered Species  Committee
ESCA: Electron Spectroscopy for Chemical An,
ESCAP:  Economic and Social Commission for A
  and the Pacific
ESECA: Energy Supply  and Environment
  Coordination Act
ESH: Environmental Safety and Health
ESP: Electrostatic Precipitators
ET: Emissions Trading
ETP: Emissions Trading Policy
ETS: Environmental Tobacco Smoke
EWCC: Environmental Workforce Coordinatii
EX: Executive Level Appointment
ExEx: Expected Exceedance
EUP: Environmental Use Permit
F: Fahrenheit (Degrees)
FAA: Federal Aviation Administration
FACA: Federal Advisory Committee Act
FACM: Friable Asbestos-Containing Material
FAM: Friable Asbestos Material
FAME: Framework for Achieving Managerial
FAN: Fixed Account Number
FAO: Food and Agriculture Organization
FAR: Federal Acquisition Regulations
FASB: Financial Accounting Standards Board
FATES: FIFRA and TSCA Enforcement Systei
FBC: Fluidized bed combustion
FCC: Federal Communications Commission
FCC: Fluid Catalytic  Converter
f/cc: Fibers per cubic centimeters (of air)
FCCU: Fluid Catalytic Cracking Unit
FCO: Federal Coordinating Officer (in disas
FCO: Forms Control Officer
FDA: Food and Drug Administration
FDF: Fundamentally Different Factors
FDIC: Federal Deposit Insurance Corporation
FDL: Final Determination Letter
FDO: Fee  Determination Official
FE: Fugitive Emissions
FEA: Federal Energy Administration
FEC: Federal Executive Council
FEDS: Federal Energy Data System
FEFx: Forced Expiratory Flow
FEHB: Federal Employees Health Benefits
FEI: Federal Executive Institute
FEIS: Fugitive Emissions Information System;
FEL: Frank Effect Level
FEMA: Federal Emergency Management Agen
FEMA-REP-1: Response Plans and Preparedni
  in Support of Nuclear Power  Plants
FEMA-REP-2: Guidance for  Developing State ;
  Local Radiological Emergency Response PI
  and Preparedness  for Transportation Actioi
FEPCA: Federal Energy Policy  and Conservation A
FERC: Federal Energy Regulatory Commissio
FERSA: Federal Employee Retirement System
FES: Factor Evaluation System
FEV: Forced Expiratory Volume
FEV1: Forced Expiratory Volume - one secon
FEVI: Front End Volatility Index
FEW: Federally Employed Women
FF: Federal Facilities
FFF: Firm  Financial Facility
FFAR: Fuel and Fuel Additive Registration
FFDCA: Federal Food, Drug, and Cosmetic /
FFFSG: Fossil Fuel Fired Steam Generator
FFIS: Federal Facilities Information System
FFP: Firm  Fixed Price
FGD: Flue Gas Desulfurization
FHA: Farmers Home Administration

FHA: Federal Housing Administration
FHLBB: Federal Home Loan Bank Board
FHWA: Federal Highway Administration
FIA: Federal Insurance Administration
FIC: Federal Information Center
FICA: Federal Insurance Contributions Act
FID: Flame lonization Detector
FIFO: First In/First Out
FIFRA: Federal Insecticide, Fungicide, and Roden-
  ticide Act
FIM: Friable Insulation Material
FINDS: Facility Index System (OIRM)
FIP: Federal Implementation Plan
FIP: Federal Information Plan
FIP: Final Implementation Plan
FIPS: Federal Information Procedures System
FIT: Field  Investigation Team
FLETC: Federal Law Enforcement Training Center
FLM: Federal Land Manager
FLP: Flash Point
FLPMA: Federal Land Policy and Management
FLSA: Fair Labor Standards Act
FM: Friable Material
F/M: Food to Microorganism Ratio
FMC: Federal Maritime Commission
FMFIA: Federal Managers Financial Integrity Act
FML: Flexible Membrane Liner
FMO: Financial Management Officer
FMP: Facility Management Plan
FMP: Financial Management Plan
FMS: Financial Management System
FMVCP: Federal Motor Vehicle Control Program
FOE: Friends of the Earth
FOIA: Freedom of Information Act
FOISD: Fiber Optic Isolated  Spherical Dipol An-
FONSI: Finding of No Significant Impact (NEPA)
FORAST: Forest Response to Anthropogenic
FORTRAN: Formula Translation
FP: Fine Particulate
FPA: Federal Pesticide Act
FPC: Federal Power Commission
FPD: Flame Photometric Detector
FPEIS: Fine Particulate Emissions Information
FPM: Federal Personnel Manual
FPR: Federal Procurement Regulation
FPRS: Federal Program Resources Statement
FPRS: Formal Planning and Supporting System
FR: Federal Register
FR: Final Rulemaking
FRA: Federal Register Act
FRB: Federal Reserve Board
FRC: Federal Records Center
FRDS: Federal Reporting Data System
FREDS: Flexible Regional Emissions Data System
FRES: Forest Range Environmental Study
FRM: Federal Reference Methods
FRN: Final Rulemaking Notice
FRS: Formal Reporting System
FRTIB: Federal Retirement Thrift Investment
FS: Feasibility Study
FS: Forest  Service
FSA: Food Security Act
FSS: Facility Status Sheet
FSS: Federal Supply Schedule
FT: Full Time
FTC: Federal Trade Commission
FTE: Full Time Equivalent
FTP: Federal Test Procedure (for motor vehicles)
FTS: Federal Telecommunications System
FTS: File Transfer Service
FTP: Full-Time Temporary
FUA: Fuel Use Act
 FURS: Federal Underground Injection Control
  Reporting System
 FVC: Forced Vital Capacity
 FVMP: Federal Visibility Monitoring Program
 FWCA: Fish and Wildlife Coordination Act
 FWP: Federal Women's Program
 FWPCA: Federal Water Pollution Control Act (aka
  Clean Water Act, or CWA)
 FWPCA: Federal Water Pollution Control  Ad-
 FWS: Fish and Wildlife Service
 FY: Fiscal Year
 FYI: For Your Information
GAAP: Generally Accepted Accounting Principles
GAC: Ground-Water Activated Carbon
GACT: Granular Activated Carbon Treatment
GAO: General Accounting Office
GBL: Government Bill of Lading
GC: Gas Chromatograph
GC: General Counsel
GC/MS: Gas Chromatograph/Mass Spectograph
GCWR: Gross Combination Weight Rating
GEA: Glossary of EPA Acronyms
GEI: Geographic Enforcement Initiative
GEMS: Global Environmental Monitoring System
GEMS: Graphical Exposure  Modeling System
GEP: Good Engineering Practice
GF: General Files
GFF: Glass Fiber Filter
GFP: Government-Furnished  Property
GI: Gastrointestinal
GICS: Grant Information and Control System
GIS: Geographic Information  Systems
GIS: Global Indexing System
GLC: Gas Liquid Chromatography
GLERL:  Great Lakes  Environmental  Research
GLNPO: Great Lakes National Program Office
GLP: Good Laboratory Practices
GLWQA: Great Lakes Water Quality Agreement
GMCC: Global Monitoring for Climatic Change
g/mi: Grams per mile
GMT: Greenwich Mean Time
GNP: Gross National Product
GOCM: Goals, Objectives, Commitments, and
GOCO: Goverment-Owned/Contractor-Operated
GOGO: Goverment-Owned/Government-
GOP: General Operating Procedures
GOPO: Goverment-Owned/Privately-Operated
GPAD: Gallons per acre per day
GPG: Grams per Gallon
GPO: Government Printing Office
GPR: Ground-Penetrating  Radar
GPS: Ground-Water Protection Strategy
GRGL: Ground-Water Residue Guidance Level
GS: General Schedule
GSA: General Services  Administration
GTN: Global Trend Network
GTR: Government Transportation  Request
GVP: Gasoline Vapor Pressure
GVW: Gross Vehicle Weight
GVWR: Gross Vehicle Weight Rating
GW: Ground Water
GWM: Ground-Water Monitoring
GWPS: Ground-Water Protection Standard
GWPS: Ground-Water Protection Strategy

 HAD: Health Assessment Document
 HAP: Hazardous Air Pollutant
 HAPEMS: Hazardous Air Pollutant Enforcement
   Management System
 HAPPS: Hazardous Air Pollutant Prioritization
 HATREMS: Hazardous and Trace Emissions
 HAZMAT: Hazardous Material
 HAZOP: Hazard and Operability Study
 HB: Health Benefits
 HBEP: Hispanic and Black Employment Programs
 HC: Hazardous Constituents
 HC: Hydrocarbons
 HCCPD: Hexachlorocyclopentadiene
 HCP: Hypothermal Coal Process
 HDD: Heavy-Duty Diesel
 HDE: Heavy-Duty Engine
 HDG: Heavy-Duty Gasoline-Powered Vehicle
 HOPE: High Density Polyethelene
 HDT: Heavy-Duty Truck
 HDV: Heavy-Duty Vehicle
 HEAL: Human Exposure Assessment Location
 HECC: House Energy and Commerce Committee
 HEI: Health Effects Institute
 HEM: Human Exposure Modeling
 HEP: Hispanic Employment Program
 HEPA: High-Efficiency Particulate Air
 HERL: Health Effects Research Laboratory
 HERS: Hyperion Energy Recovery System
 HEX-BCH: Hexachloronorbornadiene
 HHE: Human Health and the Environment
 HHS: Department of Health and Human Services-
   Formerly HEW
 HHV: Higher Heating Value
 HI: Hazard Index
 HI-VOL: High-Volume Sampler
 HIWAY: A Line Source Model for Gaseous Pollut-
 HLRW: High-Level Radioactive Waste
 HMIS: Hazardous Materials Information System
 HMS: Highway Mobile Source
 HMTA: Hazardous Materials Transportation Act
 HMTR: Hazardous Materials Transportation
 HO: Headquarters Offices
 HOC: Halogenated Organic Carbons
 HON: Hazardous Organic NESHAP
 HOV: High-Occupancy Vehicle
 HP: Horse Power
 HPLC: High Performance Liquid  Chromatogra-
 HPV: High Priority Violater
 HQ: Headquarters
 HQCDO: Headquarters Case Development Offi-
 HRC: Human Resources Council
 HRS: Hazardous Ranking System
 HRUP: High Risk Urban Problem
 HSDB: Hazardous Substance Data Base
 HSL: Hazardous Substance List
 HSWA: Hazardous and Solid Waste Amend-
 HT: Hypothermally Treated
 HTP: High Temperature and Pressure
HUD: Department of Housing and Urban De-
HVAC: Heating, Ventilation, and Air Condition-
 ing (System)
HVIO: High Volume Industrial Organics
HW: Hazardous Waste
HWDMS: Hazardous  Waste Data Management
 System (OSWER)
HWERL: Hazardous Waste Engineering Research

HWGTF: Hazardous'Waste Ground Water Task
HWGTF: Hazardous Waste Ground Water Test
HWLT: Hazardous Waste Land Treatment
HWM: Hazardous Waste Managment
HVVRTF: Hazardous Waste  Restrictions Task
HWTC:  Hazardous Waste Treatment Council

IA: Interagency Agreeement
IAAC: Interagency Assessment Advisory Com-
IAEA: International Atomic Energy Agency
IAG: Interagency  Agreement
IAP: Incentive Awards Program
IAP: Indoor Air Pollution
IARC: International Agency for  Research on
IARDB: Interim Air Toxics Data Base
IBA: Industrial Biotechnology Association
IBRD: International Bank for  Reconstruction and
ICAIR: Interdisciplinary Planning and Informa-
 tion Research
ICAP: Inductively Coupled Argon Plasma
ICBN: International Commission on the Biological
  Effects of Noise
ICC: Interstate Commerce Commission
ICE: Industrial Combustion Emissions Model
ICE: Internal Combustion Engine
ICP: Inductively Coupled Plasma
ICR: Information Collection Request
ICRE: Ignitability,  Corrosivity, Reactivity, Extrac-
 tion (Characteristics)
ICRP: International Commission on Radiological
ICS: Institute for Chemical Studies:
ICS: Intermittent Control Strategies
ICS: Intermittent Control System (CAA)
ICWM: Institute for Chemical Waste Management
ID: Inside Diameter
IDLH: Immediately Dangerous  to Life and
IEB: International  Environment Bureau
IEMP: Integrated  Environmental Management
IBS: Institute for Environmental Studies
IFB: Invitation for Bid
IFCAM: Industrial Fuel Choice Analysis Model
IFIS : Industry File Information System
IFPP: Industrial Fugitive Process Particulate
1G: Inspector General
IGCI: Industrial Gas Cleaning Institute
IIS: Inflationary Impact Statement
IJC: International  Joint Commission (on Great
I/M: Inspection/Maintenance
IMM: Intersection Midblock Model
IMPACT: Integrated Model of Plumes and Atmos-
  phere  in Complex Terrain
IMPROVE: Interagency Monitoring of Protected
 Visual Environment
INPUFF: A Gaussian Puff Dispersion Model
INT: Intermittent
IO: Immediate Office
IOAA: Immediate Office of the Assistant Adminis-
IOAU: Input/Output Arithmetic Unit
IOB: Iron Ore Beneficiation
IOU: Input/Output Unit
IP: Inhalable Particles
IPA: Intergovernmental Personnel Act
IPA: Intergovernmental Personnel Agreement
1PM: Inhalable Particulate Matter
IPM:  Integrated Pest Management
IPP: Implementation Planning Program
IPP: Integrated Plotting Package
IPP: Intermedia Priority Pollutant (document)
IPCS: International Program on Chemical Safety
IR: Infrared
IRG: Interagency Review Group
IRIS: Instructional Resources Information System
IRIS: Integrated Risk Information System
IRM: Intermediate Remedial Measures (CERCLA)
IRMC: Inter-Regulatory Risk Management Coun-
IRP: Installation Restoration Program
IRPTC: International Register of Potentially Toxic
IRR: Institute of Resource Recovery
IRS: Internal Revenue Service
IRS: International Referral Systems
IS: Interim Status
ISAM: Indexed Sequential File Access Method
ISC: Industrial Source Complex
ISCL: Interim Status Compliance Letter
ISCLT: Industrial  Source Complex  Long Term
1SCST: Industrial  Source Complex  Short Term
ISD: Interim Status Document (RCRA)
ISE: Ion-specific electrode
ISMAP: Indirect Source Model for Air Pollution
ISS: Interim Status Standards
ITC: Interagency Testing Committee
ITC: International Trade Commission
ITDP: Individual Training and Development Plan
ITP: Individual Training Plan
IWC: In-Stream Waste Concentration (CWA)
IWS: Ionizing Wet Scrubber
JAPCA: Journal of Air Pollution Control Associa-
JCL: Job Control Language
JEC: Joint Economic Committee
JLC: Justification for Limited Competition
JNCP: Justification for Non-Competitive Procure-
JOFOC: Justification for Other Than Full and
  Open Competition
JPA: Joint Permitting Agreement
JSD: Jackson Structured Design
JSP: Jackson Structured Programming
JTU: Jackson Turbidity Unit

KW: Kilowatt
KWH: Kilowatt Hour
LAA: Lead Agency Attorney
LAER: Lowest Achievable Emission Rate
LAI: Laboratory Audit Inspection
LAMP: Lake Acidification Mitigation Project
LC: Lethal Concentration
LC: Liquid Chromatography
LCD: Local Climatological Data
LCL: Lower Control Limit
LCM: Life Cycle Management
LCRS: Leachate Collection and Removal System
LD:  Land Disposal
LD:  Light Duty
LD50: Low Dose Where Fifty Percent of Animals
LDC: London Dumping Convention
LDCRS: Leachate Detection, Collection, and R
  moval System
LDD: Light-Duty Diesel
LDIP: Laboratory Data Integrity Program
LDR: Land Disposal Restrictions
LDRTF: Land Disposal Restrictions Task Force
LDS: Leak Detection System
LOT: Light-Duty Truck
LDV: Light-Duty Vehicle
LEL: Lower Explosive Limit
LEP: Laboratory Evaluation Program
LEPC: Local Emergency Planning Committee
LERC: Local Emergency Response Committee
LFL: Lower Flammability Limit
LIDAR: Light Detection and Ranging
LIFO: Last In/First Out
LIMB: Limestone-Injection, Multi-Stage Burnei
LLRW: Low Level Radioactive Waste
LMFBR: Liquid Metal Fast Breeder Reactor
LMR: Labor Management Relations
LNEP: Low Noise Emission Product
LNG: Liquified Natural Gas
LOAFL: Lowest Observed Adverse Effect  Leve
LOC: Library of Congress
LOE: Level of Effort
LOEL: Lowest Observed Effect Level
LOIS: Loss of Interim Status (SDWA)
LONGZ: Long-Term Terrain Model
LOQ: Level of Quantitation
LP: Legislative Proposal
LPG: Liquified Petroleum Gas
LSI: Legal Support Inspection  (CWA)
LSL: Lump Sum  Leave
LST: Low-Solvent Technology
LTA: Lead Trial Attorney
LTD: Land Treatment Demonstration
LTO: Landing-Takeoff Cycle
LTOP: Lease to Purchase
LTR: Lead Technical Representative
LTU: Land Treatment Unit
LUST: Leaking underground Storage Tank(s) (c
  rent usage omits the "L")
LWCF: Land and Water Conservation Fund.
LWOP: Lease with Option to Purchase
LWOP: Leave Without Pay
MAB: Man and Biosphere Program
MADCAP: Model of Advection, Diffusion,  ar
 Chemistry for Air Pollution
MAER: Maximum Allowable Emission Rate
MAG: Management Advisory Group
MAP3S: Multistate Atmospheric Power Produ
 tion Pollution Study
MAPPER: Maintaining, Preparing, and Produci
  Executive Reports
MAPSIM: Mesoscale  Air Pollution Simulatii
MARC: Mining and Reclamation Council
MATC: Maximum Allowable Toxicant Concent
MBDA: Minority Business Development Agen
MBE: Minority Business Enterprises
MCA: Manufacturing Chemists Association
MCEF: Mixed Cellulose Ester Filter
MCL: Maximum Contaminant Level
MCLG: Maximum Contaminant Level Goal
MCP: Municipal Compliance Plan (CWA)
MD: Mail Drop
MDA: Methylenedianilline
MDL: Method Detection Limit
MEFS: Midterm Energy Forecasting System
MEI: Maximum Exposed Individual:
MEK: Methyl Ethyl Ketone
MEM: Modal Emission Model
MENS:  Mission Element Needs Statement

 MEP: Multiple Extraction Procedure
 MERL: Municipal Environmental Research Lab-
 MESOPAC: Mesoscale Meteorological Reproces-
  ser Program
 MESOPLUME: Mesoscale "Bent Plume" Model
 MESOPUFF: Mesoscale Puff Model
 MESS: Model Evaluation Support System
 MFBI: Major Fuel Burning Installation
 MFC: Metal Finishing Category
 MGD: Million Gallons Per Day
 MH: Man-Hours
 MHD: Magnetohydrodynamics:
 MIBK: Methyl Isobutyl Ketone
 MIC: Methyl Isocaynate
 MICE: Management Information Capability for
 MICROMORT: A One-in-a-Million Chance of
  Death from an Environmental Hazard
 MIPS: Millions of Instructions Per Second
 MIS: Management Information System
 MIS: Mineral Industry Surveys
 MITS: Management Information Tracking System
 ML: Meteorology Laboratory:
 ML: Military Leave
 MLAP: Migrant Legal Action Program
 MLSS: Mixed Liquor Suspended Solids
 MLVSS: Mixed Liquor Volatile Suspended Solids
 MMS: Minerals Management Service (DOI)
 MMT: Million Metric Tons
 MOA: Memorandum of Agreement
 MOBILE: Mobile Source Emission Model
 MOD: Miscellaneous Obligation Document
 MOD: Modification
 MOI: Memorandum of Intent
 MOS:  Margin of Safety
 MOU: Memorandum of Understanding
 MP: Melting Point
 MPO:  Metropolitan Planning Organization
 MPP: Merit Promotion Plan
 MPRSA: Marine Protection, Research and Sanc-
  tuaries Act
 MPTDS: MPTER Model with Deposition and Set-
  tling of Pollutants
 MPTER: Multiple Point Source Model with Ter-
 MRA:  Minimum Retirement Age
 MRP: Multi-Roller Press (in sludge drying unit)
 MS: Mail Stop
 MS: Mass Spectrometry
 MSA: Management System Audits
 MSA: Metropolitan Statistical Areas
 MSAM: Multi-Keyed Indexed Sequential File Ac-
  cess Method:
 MSDS. Material Safety Data Sheet
 MSEE: Major Source Enforcement Effort
 MSHA: Mine Safety and Health Administration
 MSIS:  Model State Information System
 MSL: Mean Sea Level
 MSPB: Merit System Protection Board
 MTB: Materials Transportation Bureau
 MTBE: Methyl Tertiary Butyl Ether
 MTD: Maximum Tolerated Dose
 MTDDIS: Mesoscale Transport Diffusion  and
 Deposition Model for Industrial Sources
MTG: Media Task Group
MTS: Management Tracking System  (OW)
 MTSL: Monitoring and Technical Support Labora-
 MTU: Mobile Treatment Unit
 MVA:  Multivariate Analysis
 MVAPCA: Motor  Vehicle Air  Pollution Control
 MVEL: Motor Vehicle Emissions Laboratory
 MVI/M: Motor Vehicle Inspection/Maintenance
 MVICSA: Motor Vehicle Information and Cost
 Savings Act:
 MVRS: Marine Vapor Recovery System
 MVTS: Motor Vehicle Tampering Survey
 MW: Megawatt
 MW: Molecular Weight
 MWC: Municipal Waste Combustor
 MWG: Model Work Group
 MWL: Municipal Waste Leachate
 MYDP: Multi-Year Development Plans

 NA: National Archives
 NA: Nonattainment
 N/A: Not Applicable
 N/A: Not Available
 NAA: Nonattainment Areas
 NAAQS: National Ambient Air Quality Standards
   Program (CAA)
 NAAS: National Air Audit System (OAR)
 NACA: National Agricultural Chemicals Associa-
 NADB: National Atmospheric Data Bank
 NADP: National Atmospheric Deposition Pro-
 NAIS: Neutral  Administrative Inspection
 NALD: Nonattainment Areas Lacking Demon-
 NAMA: National Air Monitoring Audits
 NAMS: National Air Monitoring System
 NANCO: National Association of Noise Control
 NAPAP: National Acid Precipitation Assessment
 NAPBN: National Air Pollution Background Net-
 NAPBTAC: National Air Pollution Control Tech-
  nical Advisory Committee
 NAR: National Asbestos Registry
 NARA: National Air Resources Act
 NARA: National Archives and Records Adminis-
 NARS: National Asbestos-Contractor Registry
 NAS: National Academy of Sciences
 NAS: National Audubon Society
 NASA: National Aeronautics and Space Adminis-
 NATICH: National Air Toxics Information Clear-
 NAWC: National Association of Water Companies
 NAWDEX: National Water Data Exchange
 NEAR: Non-Binding Allocation of Authority
 NBS: National Bureau of Standards
 NCA: National Coal Association
 NCA: Noise Control Act
 NCAC: National Clean Air Coalition
 NCAF: National Clean Air Fund
 NCAMP: National Coalition Against the Misuse of
 NCAQ: National Commission on Air Quality
 NCAR: National Center for Atmospheric Research
 NCASI: National Council of the Paper Industry for
  Air and Stream Improvements
 NCC: National Climatic Center
 NCC: National Computer Center
 NCF: Network Control Facility
 NCHS: National Center for Health Statistics (NIH)
 NCI: National Cancer Institute
NCIC:  National Crime Information Center
NCLP:  National  Contract Laboratory Program
NCM: National Coal Model
NCM: Notice  of Commencement of Manufacture
NCO: Negotiated Consent Order
NCP: National Contingency Plan  (CERCLA)
NCP: Noncompliance  Penalties (CAA):
NCP: Nonconformance Penalty:
NCR: Noncompliance Report (CWA)
NCR: Nonconformance Report
NCRIC: National Chemical  Response and In-
  formation Center
NCS: National Compliance Strategy:
NCV: Nerve Conduction Velocity
NCVECS: National Center for Vehicle Emissions
  Control and Safety
NCWQ: National Commission on Water Quality
NDD: Negotiation Decision Document
NDDN: National Dry Deposition Network
NDIR: Nondispersive Infrared Analysis
NDS: National Dioxin Study
NDS: National Disposal Site
NDWAC: National Drinking Water Advisory
NEA: National Energy Act
NEDA: National  Environmental Development
NEDS: National Emissions Data System
NEEC: National Environmental Enforcement
  Council (NAAG)
NEEJ: National Environmental Enforcement Jour-
  nal (NAAG)
NEIC: National Enforcement Investigations Cen-
NEP:  National Energy Plan
NEP:  National Estuary Program
NEPA: National Environmental Policy Act
NER: National Emissions Report
NEROS: Northeast Regional Oxidant Study
NESCAUM: Northeast States for Coordinated Air
  Use Management
NESHAPS: National  Emissions  Standards for
  Hazardous Air Pollutants (CAA)
NETC: National Emergency Training Center
NETTING: Emission Trading Used to Avoid PSD/
  NSR Permit Review Requirements
NFAN: National Filter Analysis Network
NFFE: National Federation of Federal Employees
NFIP: National Flood Insurance Program
NFWF: National Fish and Wildlife Foundation
NGA: Natural Gas Association
NGPA: Natural Gas Policy Act
NGWIC: National Ground Water Information
NHANES: National Health and Nutrition Ex-
  amination Study
NHPA: National Historic Preservation Act
NHTSA: National Highway Traffic Safety Act
NHTSA: National Highway Traffic  Safety Ad-
  ministration (DOT)
NHWP: Northeast Hazardous Waste Project
NICS: National Institute for Chemical Studies
NIEHS:  National Institute of Environmental
  Health Sciences
NIEI:  National Indoor Environmental Institute
NIH: National Institutes of Health
NIM:  National Impact Model
NIMBY:  Not In My Backyard
NIOSH: National Institute of Occupational Safety
  and  Health
NIPDWR: National Interim  Primary Drinking
  Water Regulations
NIS: Noise Information System
NITEP: National Incinerator Testing and Evalua-
  tion Program
NLAP: National Laboratory Audit program
NLETS: National Law Enforcement Teletype Sys-
NLM: National Library of Medicine
NLT: Not Later Than
NMC: National Meteorological Center
NMFS: National Marine Fisheries Service (DOC)
NMHC: Nonmethane Hydrocarbons
NMOC: Nonmethane Organic Compound
NMP: National Municipal Policy

NMR: Nuclear Magnetic Resonance
NNC: Notice of Noncompliance
NNPSPP: National Non-Point Source Pollution
NOA: New Obligation Authority
NOAA: National Oceanic and Atmospheric Ad-
  ministration (DOC)
NOAEL: No Observed Adverse Effect Level
NOC: Notice of Commencement
NOD: Notice of Deficiency (RCRA)
NOEL: No Observed  Effects Level
NOHSCP: National  Oil  and Hazardous Sub-
  stances Contingency Plan
NON: Notice of Noncompliance (TSCA)
NOPES: Non-Occupational Pesticide Exposure
NORA: National Oil Recyclers Asssociation
NOS: National Ocean Survey (NOAA)
NOV: Notice of Violation
NOV/C/D: Notice of  Violation/Compliance/
NPAA: Noise Pollution  and Abatement Act-
NPCA: National Parks and Conservation Associa-
NPDES: National Pollutant Discharge Elimination
  System (CWA)
NPIRES: National Pesticide Information Retrieval
NPL: National Priority List (CERCLA)
NPM: National Program Manager
NPN: National Particulate Network
NPRM: Notice of Proposed Rulemaking
NPS: National Park Service
NFS: National Permit Strategy
NPS: National Pesticide Survey (OW)
NPS: Non-Point Source
NPUG: National Prime User Group
NRA: National Recreation Area
NRC: National Research Council
NRC: National Response Center
NRC: Non-Reusable Containers
NRC: Nuclear Regulatory Commission
NRCA: National Resource Council of America
NRDC: Natural Resources Defense Council
NRT: National Response Team
NRWA: National Rural Water Association:
NSC: National Security  Council:
NSDWR: National Secondary Drinking Water
NSF: National Sanitation Foundation.
NSF: National Science Foundation
NSO: Nonferrous Smelter Orders (CAA)
NSPS: New Source Performance Standards (CAA)
NSR: New Source (Pre-construction) Review
NSTL: National Space Technology Laboratory
NSWMA: National Solid Waste Management
NSWS: National Surface Water Survey
NTA: Negotiated Testing  Agreement
NTE: Not to Exceed
NTIS: National Technical Information Service
NTN: National Trends Network
NTP: National Toxicology Program
NTSP: National Transportation Safety Board
NURF: NAPA Utility Reference File
NVPP: National Vehicle Population Poll
NWA: National Water Alliance
NWF: National Wildlife Federation
NWPA: Nuclear Waste  Policy Act
NWRC: National Weather Records Center
NWS: National Weather Service (NOAA)
 Ox: Total Oxidants
 OASDI: Old Age and Survivor Insurance
 OC: Object Class
 OCD: Offshore and Coastal Dispersion Model
 OCI: Organizational Conflicts of Interest
 OCR: Optical Character Reader
 OCS: Outer Continental Shelf
 OCSLA: Outer Continental Shelf Lands Act
 OD: Organizational Development
 OD: Outside Diameter
 OF: Optional Form
 O&G: Oil and Gas
 O&M: Operations and Maintenance
 OMB: Office of Management and Budget
 OP: Operating Plan
 OPAC: Overall Performance Appraisal Certifica-
 OFF: Official Personnel Folder
 ORM: Other Regulated Material
 ORNL: Oak Ridge  National Laboratory
 ORP: Oxidation-Reduction Potential
 ORV: Off-road Vehicle
 OSC: On-Scene Coordinator
 OSHA: Occupational Safety and Health Act
 OSHA: Occupational Safety and Health Adminis-
  tration (DOL)
 OSM: Office of Surface Mining (DOI)
 OSTP: Office of Science and Technology Policy
  (White House)
 OS/VS: Operating System/Virtual Storage
 OT: Overtime
 OTA: Office of Technology Assessment (US Con-
 OY: Operating Year
 OYG: Operating Year Guidance
 OZIPP: Ozone Isopleth Plotting Package
 OZIPPM: Modified Ozone Isopleth Plotting Pack-
PA: Policy Analyst
PA: Preliminary Assessment
P&A: Precision and Accuracy
PAA: Priority Abatement Areas:
PADRE: Particle  Analysis and Data Reduction
PAGM: Permit Applications Guidance Manual
PAH: Polycyclic Aromatic Hydrocarbon
PAHO: Pan Americn Health Organization
PAI: Performance Audit Inspection (CWA)
PAIR: Preliminary Assessment Information Rule
PAL:  Point, Area, and Line Source Air Quality
PALDS: PAL Model with Deposition and Settling
  of Pollutants
PAN:  Peroxyacetyl Nitrate
PAPR: Powered Air Purifying Respirator
PARS: Precision and Accuracy Reporting System
PASS: Procurement Automated Source System
PAT:  Permit Assistance Team (RCRA)
PBB: Polybromated Biphenyls
PBL: Planetary Boundary Layer
PBLSQ: The Lead Line Source Model
PC: Personal Computer
PC: Planned Commitment
PC: Position Classification
PC: Pulverized Coal
PCA:  Principle Component Analysis
PCB:  Polychlorinated  Biphenyls
PC&B: Personnel Compensation  and Benefits
PCDD: Polychlorinated Dibenzodioxm
PCDF: Polychlonnated Dibendzofuran
PCE: Pollution Control Equipment
PCIE: President's Council on Integrity and Effi-
 ciency in: Government
 pCi/1: Picocuries Per Litre
 PCIOS: Processor Common Input/Output Systei
 PCM: Phase Contrast Microscopy
 PCO: Printing Control Officer
 PCON:  Potential Contractor
 PCP: Pentachlorophenyl
 PCS: Permanent Change of Station
 PCS: Permit Compliance System (CWA)
 PCSC: PC Site Coordinator
 PCV: Positive Crankcase Ventilation
 PD: Position Description
 PD: Position Document
 PD: Project Description
 PDFID: Preconstruction Direct Flame lomzatioi
 PDMS:  Pesticide Document Management Syster
 PDR: Particulate Data Reduction
 PE: Program Element
 PEL: Permissible Exposure Limit
 PEL: Personal Exposure Limit
 PEM: Partial Equilibrium Multimarket Model
 PEM: Personal Exposure Model
 PEPE: Prolonged Elevated Pollution Episode
 PESTAN: Pesticides Analytical Transport Solutio
 PF: Potency Factor
 PF: Protection Factor
 PFT: Permanent Full Time
 PFTE: Permanent Full-Time Equivalent
 PHC: Principal Hazardous  Constituent
 PHS: (US) Public Health Service
 PHSA: Public Health Service Act
 PI: Preliminary Injunction
 PI: Program Information
 PIC: Products of Incomplete Combustion
 PIC: Public Information Center
 PIGS: Pesticides in Groundwater Strategy
 PIN: Procurement Information Notice
 PIP: Public Involvement Program
 PIPQUIC: Program Integration Project Querie
  Used in Interactive Command
 PIRG: Public Interest Research Group
 PIRT: Pretreatment Implementation Review Tas
 PIS: Public Information Specialist:
 PITS: Project Information Tracking System (OTS
 PLIRRA: Pollution Liability Insurance  and  Ris
  Retention Act
PLM: Polarized Light Microscopy
PLUVUE: Plume Visibility Model
PM: Particulate Matter
PM: Program Manager
PM10: Particulate Matter (nominally 10m and less
PM15: Particulate Matter (nominally 15m and less
PMEL: Pacific Marine Environmental Laborator
PMIP: Presidential Management Intern Prograrr
PMIS: Personnel Management Information  Sys
  tern (OARM)
PMN: Premanufacture Notification (TSCA)
PMNF: Premanufacture Notification Form
PMR: Pollutant Mass Rate
PMRS: Performance Management and  Recogni
  tion System (OARM)
PMS: Personnel Management Specialist
PMS: Program Management System
 PNA: Polynuclear Aromatic Hydrocarbons
 PO: Project Officer
 PO: Purchase Order
 POC: Point of Compliance
 POC: Program Office Contacts
 POE: Point of Exposure
POGO:  Privately-Owned/Government-Operatec
POHC: Principal Organic Hazardous Constituer
 POI: Point of Interception
 POLREP: Pollution Report
 POM: Particulate Organic Matter
 POM: Polycyclic Organic Matter



POTW: Publicly Owned Treatment Works
POV: Privately Owned Vehicle
PP: Pay Period
PP: Program Planning
PPA: Pesticide Producers Association
PPA: Planned Program Accomplishment
ppt>: Parts Per Billion
PPC: Personal Protective Clothing
PPI:: Personal Protective Equipment
PPIS: Pesticide Product Information System
pprn: Parts Per Million
PPMAP: Power Planning  Modeling Application
PPSP: Power Plant Siting Program
PPT: Permanent Part Time
ppt  Parts Per Trillion
ppt!i: Parts Per Thousand
PR: Preliminary Review
PR: Procurement Request
PRA: Paperwork Reduction Act
PRA: Planned Regulatory  Action
PRM: Prevention Reference Manuals
PRI1: Potentially Responsible Party  (CERCLA)
PS: Point Source
PSA M: Point Source Ambient Monitoring
PSD: Prevention of Significant Deterioration
PSE: Program Subelement
PSIS: Pretreatment Standards  for Existing
PSI: Pollutant Standards Index
PSI: Pounds Per Square Inch (Pressure)
PSI: Pressure Per Square Inch
PSIG: Pressure Per Square Inch Gauge
PSM: Point Source Monitoring
PSNS: Pretreatment Standards for New Sources
PSP Payroll Savings Plan
PSS. Personnel Staffing Specialist
PST'V: Pesticide Safety Team Network
PT: 3art Time
PTDIS: Single Stack Meteorological  Model in EPA
  UMAMAP Series
PTE: Potential to Emit
PTFH: Polytetrafluoroethylene (Teflon)
PTM AX:' Single Stack Meteorlogical  Model in EPA
  UNAMAP series
PTPLU: Point Source Gaussian Diffusion Model
PUC: Public Utility Commission
PV: Project Verification
PVC: Polyvmyl Chloride
PWS: Public Water Supply
PWS: Public Water System (SDWA)
PWSS: Public Water Supply System (SDWA)
PY: Prior Year
QA: Quality Assurance
QAC: Quality Assurance Coordinator
QA/QC: Quality Assistance/Quality Control
QAMIS: Quality Assurance Management and In-
  for nation System
QAO: Quality Assurance Officer
QAPP: Quality Assurance Program (or Project)
qBtu: Quadrillion British Thermal Units
QC: Quality Control
QCA: Quiet Communities Act
QCI:  Quality  Control Index
QCP: Quiet Community Program
QNCR: Quarterly Noncomphance Report
Q5I:  Quality  Step Increase

 RA: Reasonable Alternative
 RA: Regional Administrator
 RA: Regulatory Alternatives
 RA: Regulatory Analysis
 RA: Remedial Action
 RA: Resource Allocation
 RA: Risk Analysis
 RA: Risk Assessment
 RAATS: RCRA Administrative Action Tracking
 RAC: Radiation Advisory Committee
 RAC: Regional Asbestos Coordinator
 RAC: Response Action Coordinator
 RACM: Reasonably Available Control Measures
 RACT: Reasonably Available Control Technology
 RAD: Radiation Adsorbed Dose (unit of measure-
  ment of radiation adsorbed by humans)
 RADM: Random  Walk Advection and Dispersion
 RADM: Regional  Acid Deposition Model
 RAM: Urban Air Quality Model for Point and Area
  Source in EPA UNAMAP Series
 RAMP: Rural Abandoned Mine Program
 RAMS: Regional Air Monitoring System
 RAP: Radon Action Program
 RAP: Remedial Accomplishment Plan
 RAP: Response Action Plan
 RAPS: Regional Air Pollution Study
 RARG: Regulatory Analysis Review Group
 RAS: Routine Analytical Service
 RAT: Relative Accuracy Test
 RB: Red Border
 RBC: Red Blood Cells
 RC: Regional Counsel
 RC: Responsibility Center
 RCC: Radiation Coordinating Council
 RCDO: Regional Case Development Officer
 RCP: Research Centers Program
RCRA: Resource Conservation and Recovery Act
 RCRIS: Resource  Conservation and Recovery In-
  formation System
 RD: Remedial Design  (CERCLA)
 R&D: Research and Development
 RD&D: Research, Development and Demonstra-
 RDF: Refuse-Derived Fuel
 rDNA: Recombmant DNA
 RDU: Regional Decision Units
 RE: Reasonable Efforts
RE: Reportable Event
REAP: Regional Enforcement Activities Plan
REE: Rare Earth Elements
REEP: Review of Environmental Effects of Pollut-
REF: Reference
REM: Roentgen Equivalent, Man
REM/FIT: Remedial/Field Investigation Team
REMS: RCRA Enforcement Management System
REP: Reasonable Efforts Program
REPS: Regional Emissions Projection System
RESOLVE: Center for Environmental Conflict
RF: Radio Frequency
RF: Response Factor
RFA: Regulatory Flexibility Act
RFB: Request for Bid
RFD: Reference Dose Values
RFI: Remedial Field Investigation
RFP: Reasonable Further Programs
RI: Reconnaissance Inspection (CWA)
RI: Remedial Investigation
RIA: Regulatory Impact Analysis
RIA: Regulatory Impact Assessment
RIC: Radon Information Center
RIC: RTP Information  Center
RICC: Retirement Information  and Counseling
RICO: Racketeer Influenced and Corrupt Organi-
  zations Act
RI/FS: Remedial Information/Feasibility Stud)'
RIM: Regulatory Interpretation  Memorandum
RIN: Regulatory Identifier Number-
RIP: RCRA Implementation Plan
RISC: Regulatory Information Service Center
RJE: Remote Job Entry
RLL: Rapid and Large Leakage  (Rate)
RMCL: Recommended Maximum  Contaminant
  Level (this phrase is being discontinued in favoi
  of MCLG)
RMDHS: Regional Model Data Handling System
RMIS: Resources Management Information  Sys-
RMO: Records Management Officer
RMP: Revolutions Per Minute
RNA: Ribonucleic Acid
RO: Regional Office
ROADCHEM: Roadway Version that Includes
  Chemical Reactions of BI, NO2, and Oa
ROADWAY:  A Model to Predict Pollutant Con-
  centrations Near a Roadway
ROC: Record of Communication
ROD: Record of Decision (CERCLA)
ROG: Reactive Organic Gases
ROLLBACK:  A Proportional Reduction Model
ROM: Regional Oxidant Model
ROMCOE: Rocky Mountain  Center on the  En-
ROP: Regional Oversight Policy
ROPA: Record of Procurement Action
RP: Respirable Particulates
RP: Responsible Party
RPAR: Rebuttable Presumption Against Registra-
  tion (FIFRA)
RPM: Reactive Plume Model
RPM: Remedial Project Manager (CERCLA)
RPM: Revolutions Per Minute
RPO: Regional Planning Officer
RPO: Regional Program Officer
RQ: Reportable Quantities
RRC: Regional Response Center
RRT: Regional Response Team
RRT: Requisite Remedial Technology
RSCC: Regional Sample Control Center
RSKERL: Robert S. Kerr Environmental Research
RT: Regional Total
RTCM: Reasonable Transportation Control
RTD: Return to Duty
RTDM: Rough Terrain Diffusion Model
RTECS: Registry of Toxic Effects of Chemical Sub-
RTM: Regional Transport Model
RTP: Research Triangle Park
RUP: Restricted Use Pesticide (FIFRA)
RVP: Reid Vapor Pressure
RWC: Residential  Wood Combustion
SA: Special Assistant
SA: Sunshine Act
S&A: Sampling and Analysis
S&A: Surveillance and Analysis
SAB: Science Advisory Board (AO)
SAC: Secretarial Advisory Board
SAC: Suspended and Cancelled Pesticides (FIF-
SADAA: Science  Assistant to  the  Deputy Ad-
SAEWG: Standing Air Emissions Work Group

SAIC: Special-Agents-In-Charge (NEIC)
SAIP: Systems Acquisition and Implementation
SAMWG: Standing Air Monitoring Work Group
SANE: Sulfur and Nitrogen Emissions
SANSS: Structure and  Nomenclature  Search
SAP: Scientific Advisory  Panel
SAR: Start Action Request
SAR: Structural Activity Relationship (of a quali-
 tative  assessment)
SARA: Superfund Amendments and Reauthoriza-
  tion Act of 1986
SAROAD: Storage and Retrieval  of Aerometric
SAS: Special Analytical Service
SAS: Statistical Analysis System
SASS: Source Assessment Sampling System
SBA: Small Business Act
SBA: Small Business Administration
SBO: Small Business Ombudsman
SC: Sierra Club
SC: Steering Committee
SCAP: Superfund Consolidated Accomplish-
 ments  Plan (CERCLA)
SCAC: Support Careers Advisory  Committee
SCBA: Self-Contamed Breathing Apparatus
SCC: Source Classification Code
SCFM: Standard Cubic Feet Per Minute
SCLDF: Sierra Club Legal Defense Fund
SCORPIO: Subject Content-Oriented Retriever
 for Processing Information On-Line
SCR: Selective Catalytic Reduction
SCRAM: State Consolidated RCRA Authorization
SCRC: Superfund Community Relations Coordi-
SCS: Soil Conservation Service
SCS: Supplementary Control Strategy
SCS: Supplementary Control System
SCSA: Soil Conservation Society of America
SCSP: Storm and Combined Sewer Program
SCW: Supercritical Water Oxidation
SD: Standard Deviation
SDBE: Small Disadvantaged Business Enterprise
SDC: Systems Decision Plan
SDVVA:  Safe Drinking Water Act
S&E: Salaries and Expensses
SEA: State Enforcement Agreement
SEA: State/EPA Agreement
SEAM: Surface, Environment, and Mining
SEAS: Strategic Environmental Assessment Sys-
SEE: Senior Environmental Employee
SEIA: Socioeconomic Impact Analysis
SEM: Scanning Electronic Microscope
SEM: Standard Error of the Means
SEPWC: Senate Environment and Public Works
SERC: State Emergency Response Commission
SES: Secondary Emissions Standard
SES: Senior Executive Service
SES: Socioeconomic Status
SETS: Site Enforcement Tracking System
SF: Standard Form
SF: Superfund
SFA: Spectral Flame Analyzers
SFFAS:  Superfund Financial Assessment Systerm
SFIREG: State FIFRA Issues Research and Evalua-
  tion Group
SHORTZ: Short Term Terrain Model
SHWL:  Seasonal High Water Level
SI: International System of Units
SI: Spark Ignition
SIC: Standard Industrial  Classification
SICEA:  Steel Industry Compliance Extension Act
SIMS: Secondary Ion-Mass Spectometry
SIP: State Implementation Plan (CAA)
SIS: Stay In School
SITE: Superfund Innovative Technology Evalua-
SL: Sick Leave
SLAMS: State/Local Air Monitoring Station
SLSM: Simple Line Source Model
SMCRA: Surface Mining Control and Reclamation
SME: Subject Matter Expert
SMO: Sample Management Office
SMSA: Standard Metropolitan Statistical Area
SNA: System Network Architecture
SNAAQS: Secondary National Ambient Air Qual-
  ity Standards
SNAP: Significant Noncomphance Action Pro-
SNARL: Suggested No Adverse Response Level
SNC: Signficant Noncompliers
SNUR: Significant New Use Rule (TSCA)
SOC: Synthetic Organic Chemicals
SOCMI: Synthetic  Organic Chemicals  Man-
 ufacturing Industry
SOP: Standard Operating Procedure
SOTDAT: Source Test Data
SOW: Scope of Work
SPAR: Status of Permit Application Report
SPCC: Spill Prevention, Containment, and Coun-
  termeasure (CWA)
SPE: Secondary Particulate Emissions
SPECS: Specifications
SPF: Structured Programming Facility
SPI: Strategic Planning Initiative
SPLMD: Soil-pore Liquid Monitoring Device
SPMS: Special Purpose Monitoring Stations
SPMS: Strategic Planning and Management Sys-
SPOC: Single Point of Contact
SPS: State Permit System
SPSS: Statistical Package for the Social Sciences
SPUR: Software Package for Unique Reports
SQBE: Small Quantity Burner Exemption
SQG: Small Quantity Generator
SRAP: Superfund Remedial Accomplishment
SRC: Solvent-Refined Coal
SRM: Standard Reference Method
SS: Settleable Solids
SS: Superfund Surcharge
SSA: Sole Source Aquifer
SSAC: Soil Site Assimulated Capacity
SSC: State Superfund Contracts: (OSWER)
SSD: Standards Support Document
SSEIS: Standard Support and Environmental Im-
  pact Statement
SSEIS: Stationary Source Emissions and Inventory
SSI: Size Selective  Inlet
SSMS: Spark Source Mass Spectrometry
SSN: Social Security Number
SSO: Source Selection Official
SST: Supersonic Transport
SSURO: Stop Sale, Use and Removal Order (FIF-
STAPPA: State and Territorial Air Pollution Pro-
  gram Administrators
STALAPCO: State and Local Air Pollution Control
STAR: Stability Wind Rose
STAR: State Acid Rain Projects
S/TCAC: Scientific/Technical  Careers  Advisory
STEL: Short-Term Exposure Limit
STEM: Scanning Transmission-Electron Micro-
STN: Scientific and Technical Information Net-
STORET: Storage and Retrieval of Water-Related
 STP: Sewage Treatment Plant
 STP: Standard Temperature and Pressure
 SUP: Standard Unit of Processing
 SURE: Sulfate Regional Experiment Program
 SV: Sampling Visit
 SW: Slow Wave
 SWC: Settlement With Conditions
 SWDA: Solid Waste Disposal Act
 SWIE: Southern Waste Information Exchange
 SWMU: Solid Waste Management Unit
 SYSOP: Systems Operator
 TA: Travel Authorization
 T&A: Time and Attendance
 TALMS: Tunable Atomic Line Molecular Spec
 TAMS: Toxic Air Monitoring System
 TAMTAC: Toxic Air Monitoring System Advisoi
 TAP: Technical Asssistance Program
 TAPDS: Toxic Air Pollutant Data System
 TAPP: Time and Attendance, Payroll, and Pel
 TBT: Tributyltin
 TC: Target Concentration
 TC: Technical Center
 TC: Toxic Concentration:
 TCDD: Dioxin (Tetrachlorodibenzo-p-dioxin)
 TCDF: Tetrachlorodibenzofurans
 TCE: Trichloroethylene
 TCLP: Total Concentrate Leachate Procedure
 TCLP: Toxicity Characteristic Leachate Procedur
 TCM: Transportation Control Measure
 TCP: Transportation Control Plan
 TCP: Trichloroethylene
 TCP: Trichloropropane
 TCRI: Toxic Chemical Release Inventory
 TD: Toxic Dose
 TDS: Total Dissolved Solids
 TOY: Temporary Duty
 TEAM: Total Exposure Assessment Model
 TEC: Technical Evaluation Committee
 TEG: Tetraethylene Glycol
 TEGD: Technical Enforcement Guidance Docu
 TEM: Texas Episodic Model
 TEM: Transmission Electron Microscopy
 TEP: Technical Evaluation Panel
 TES: Technical Enforcement Support
 TEXIN: Texas Intersection Air Quality Model
 TFT: Temporary Full Time
 TFTE: Temporary Full-Time Equivalent
 TGO: Total Gross Output
 THC: Total Hydrocarbons
 THM: Trihalomethane
 TI:  Temporary Intermittent
 TI:  Therapeutic Index
 TIBL: Thermal Internal Boundary Layer
 TIC: Technical Information Coordinator
 TIC: Tentatively Identified Compounds
 TIM: Technical Information Manager
 TIP: Transportation Improvement Program
 TISE: Take It Somewhere Else (Solid Waste Syr
  drome. See NIMBY)
 TITC: Toxic Substance Control Act Interagenc
 Testing Committee
 TLV: Threshold Limit Value
TMI: Three Mile Island
TNT: Trinitrotoluene
TO: Task Order
TO: Travel Order
TOA: Trace Organic Analysis
TOO Total Organic Carbon
TOC:' Total Organic Compound
TOT: Time-of-Travel

TOX: Tetradichloroxylene
TPC: Testing Priorities Committee
TPI: Technical Proposal Instructions
TPQ: Threshold Planning Quantity
TPSIS: Transportation Planning Support Informa-
  tion System:
TPTH: Triphenyltinhydroxide
TPY: Tons Per Year
T-R: Transformer-Rectifier
TRC: Technical Review Committee
TRD: Technical Review Document
TRI: Toxic Release Inventory
TRIP: Toxic Release Inventory Program
TRLN: Triangle Research Library Network
TRO: Temporary Restraining Order
TS: Toxic Substances
TSA: Technical Systems Audit
TSCA: Toxic Substances Control Act
TSCATS: TSCA Test Submissions Database (OTS)
TSCC: Toxic Substances Coordinating Committee
TSD: Technical Support Document
TSDF: Treatment, Storage, and Disposal Facility
TSDG: Toxic Substances Dialogue Group
TSM: Transportation System Management
TSO: Time Sharing Option
TSP: Teleprocessing Services Program
TSP: Thrift Savings Plan
TSP: Total Suspended Particulates
TSS: Terminal Security System
TSS: Total Suspended (non-filterable) Solids
TTFA:  Target Transformation Factor  Analysis
TTHM: Total Trihalomethane
TTO: Total Toxic Organics
TTY: Teletypewriter
TVA: Tennessee Valley Authority
TWA: Time Weighted Authority:
TZ: Treatment Zone

UAC: User Advisory Committee
UAM: Urban Airshed Model
UAPSP: Utility Acid Precipitation Study Program
UAQI: Uniform Air Quality Index
UARG: Utility Air Regulatory Group
UCC: Ultra Clean Coal
UCL: Upper Control Limit
UDMH: Unsymmetrical Dimethyl Hydrazine
UEL: Upper Explosive Limit
UFL: Upper Flammability Limit
UIC: Underground Injection Control
UL: Underwriters' Laboratories
ULP: Unfair Labor Practices
UMTA: Urban Mass Transportation Administra-
UMTRCA: Uranium Mill Tailings Radiation Con-
  trol Act
UN: United Nations
UNAMAP: Users' Newtork for Applied Modeling
  of Air Pollution
UNEP: United Nations Environment Program
UNESCO: United Nations Educational, Scientific
  and Cultural:  Organization
UNIDO: United Nations Industrial  Development
USAO: United States Attorney's Office
USBM: United States Bureau of Mines
USC: Unified Soil Classification
USC: United States Code
USCA: United States Code Annotated
USDA: United States Department of Agriculture
USDOI: United States Department of the Interior
USDW: Underground Sources of Drinking Water
USEPA: United States Environmental Protection
USFS: United States Forest Service
USGS: United States Geological Survey
USNRC: United States Nuclear Regulatory Com-
USPHS: United States  Public Health Service
USPS: United States Postal Service
UST: Underground Storage Tank
UTM: Universal Transverse Mercator.
UTP: Urban Transportation Planning-
UV: Ultraviolet
UZM: Unsaturated Zone Monitoring

VA: Veterans Administration
VALLEY: Meteorological Model to Calculate Con-
  centrations on Elevated Terrain
VCM: Vinyl Chloride Monomer
VE: Visual Emissions.
VEO: Visible Emission Observation
VHS: Vertical and Horizontal Spread Model
VHT; Vehicle-Hours of Travel
VISTTA: Visibility Impairment from  Sulfur
  Transformation and Transport in the Atmos-
VKT: Vehicle Kilometers Traveled
VMT: Vehicle Miles Traveled
VOC: Volatile Organic Compounds
VOS: Vehicle Operating Survey
VOST: Volatile Organic Sampling Tram
VP: Vapor Pressure
VSD: Virtually Safe Dose
VSI: Visual Site Inspection
VSS: Volatile Suspended Solids

WA: Work Assignment
WADTF: Western Atmospheric Deposition Task
WAP: Waste Analysis Plan (RCRA)
WB: Wet Bulb
WB: World Bank
WBC: White Blood Cells
WBE: Women's Business Enterprise
WCED: World Commission on Environment and
WDROP: Distribution Register of Organic Pollut-
  ants in Water
WENDB: Water Enforcement National Data Base
WERL: Water Engineering Research Laboratory
WG: Wage Grade
WG: Work Group
WGI: Within Grade Increase
WHO: World Health Organization
WHWT: Water and Hazardous Waste Team
WIC: Washington Information Center
WICEM: World Industry Conference on Environ-
  mental Management
WISE: Women In Science and Engineering
WL: Warning Letter
WL: Working Level (radon measurement)
WLA/TMDL: Waste  Load Allocation/Total Max-
  imum Daily Load
WLM: Working Level Months:
WMO: World Meteorological Organization
WPCF: Water Pollution Control Federation
WRC: Water Resources Council
WRDA: Water Resources Development Act
WRI: World Resources Institute
WS: Work Status
WSF: Water Soluble Fraction
WSRA: Wild and Scenic  Rivers Act
WSTB: Water Sciences and Technology Board
WSTP: Wastewater Sewage Treatment Plant
WWEMA: Waste and Wastewater Equipment
  Manufacturers' Association
WWF: World Wildlife Fund
WWTP: Wastewater Treatment Plant

YTD: Year to Date
ZBB: Zero Base Budgeting
ZHE: Zero Headspace Extractor
ZOI: Zone of Incorporation
ZRL: Zero Risk Level
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th  Hoo*
Chicago,  II  60604-3590