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Glossary
of Environmental, Health and Safety Terms and expressions
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A
abatement:
Reducing the degree or intensity of, or eliminating, pollution.
absorption:
the penetration of atoms, ions, or molecules into the bulk
mass of a substance.
acceptable daily Intake (ADI):
Estimate of the largest amount of chemical to which a person
can be exposed on a daily basisthat is not anticipated to
result in adverse effects (usually expressed in mg/kg/day).
Same as RfD.
acid deposition:
A complex chemical and atmospheric phenomenon that occurs
when emissions of sulfur and nitrogen compounds and other
substances are transformed by chemical processes in the atmosphere,
often far from the original sources, and then deposited on
earth in either wet or dry form. The wet forms, popularly
called "acid rain," can fall as rain, snow, or fog.
The dry forms are acidic gases or particulates.
acid mine drainage:
Drainage of water from areas that have been mined for coal
of other mineral ores; the water has low pH, sometimes less
than 2.0 (is acid), because of its contact with sulfur-bearing
material; acid drainage is harmful because it often kills
aquatic organisms.
acid rain: Precipitation
which has been rendered (made) acidic by airborne pollutants.
acidic: The
condition of water or soil that contains a sufficient amount
of acid substances to lower the pH below 7.0
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 is also used
in other regulatory programs.
activated sludge process:
A sewage treatment process by which bacteria that feed on
organic wastes are continuously circulated and put in contact
with organic waste in the presence of oxygen to increase the
rate of decomposition.
active ingredient:
In any pesticide product, the component that kills, or otherwise
controls, target pests. Pesticides are regulated primarily
on the basis of active ingredients.
acute effect:
An adverse effect on any living organism in which severe symptoms
develop rapidly and often subside after the exposure stops.
adaptation:
Changes in an organism's structure or habits that help it
adjust to its surroundings.
additive effect:
Combined effect of two or more chemicals equal to the sum
of their individual effects.
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 suspended solids. (See primary, secondary treatment.)
aeration: A
process which promotes biological degradation of organic matter
in 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).
aerobic treatment:
Process by which microbes decompose complex organic compounds
in the presence of oxygen and use the liberated energy for
reproduction and growth. (Such processes include extended
aeration, trickling filtration, and rotating biological contactors.)
aerosol: A suspension
of liquid or solid particles in a gas.
aggregate: A
mass or cluster of soil particles, often having a characteristic
shape.
agricultural waste:
Poultry and livestock manure, and residual materials in liquid
or solid form generated from the production and marketing
of poultry, livestock, furbearing animals, and their products.
Also includes gra in, vegetable, and fruit harvest residue.
agrochemical:
Synthetic chemicals (pesticide and fertilizers) used in agricultural
production.
air emissions:
Gas emitted into the air from industrial and chemical processes,
such as ozone, carbon monoxide, nitrogen oxide, nitrogen dioxide,
sulfur dioxide and others.
air mass: A
large volume of air with certain meteorological or polluted
characteristics, e,g, a heat inversion or smogginess-while
in one location. The characteristics can change as the air
mass moves away.
air pollutant:
Any substance in air that could, in high enough concentration,
harm man, other animals, vegetation, or material. Pollutants
may include almost any natural or artificial composition of
airborne matter capable of being airborne. They may be in
the form of solid particles, liquid droplets, gases, or in
combination thereof. 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 compounds, halogen compounds, radioactive
compounds, and odors.
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 given time in a defined area.
air stripping:
A treatment system that removes volatile organic compounds
(VOCs) from contaminated ground water or surface water by
forcing an airstream through the water and causing the compounds
to evaporate.
airborne particulates:
Total suspended particulate matter found in the atmosphere
as solid particles or liquid droplets. Chemical composition
of particulates varies widely, depending on location and time
of year. Airborne particulates include: windblown dust, emissions
from industrial processes, smoke from the burning of wood
and coal, and motor vehicle or non-road engine exhausts. exhaust
of motor vehicles.
algae: Chiefly
aquatic, eucaryotic one-celled or multicellular plants without
true stems, roots and leaves, that are typically autotrophic,
photosynthetic, and contain chlorophyll. Algae are not typically
found in groundwater. They also may be attached to structures,
rocks or other submerged surfaces. They are food for fish
and small aquatic animals. Excess algal growths can impart
tastes and odors to potable water. Algae produce oxygen during
sunlight hours and use oxygen during the night hours. Their
biological activities appreciably affect the pH and dissolved
oxygen of the water.
algal bloom:
Sudden, massive growths of microscopic and macroscopic plant
life, such as green or bluegreen algae, which develop in lakes
and reservoirs, which can affect water quality adversely and
indicate potentially hazardous changes in local water chemistry.
alkali: Various
soluble salts, principally of sodium, potassium, magnesium,
and calcium, that have the property of combining with acids
to form neutral salts and may be used in chemical water treatment
processes.
alluvial: Relating
to mud and/or sand deposited by flowing water. Alluvial deposits
may occur after a heavy rain storm.
alternative fuels:
Substitutes for traditional liquid, oil-derived motor vehicle
fuels like gasoline and diesel. Includesmethanol, ethanol,
compressed natural gas, and others.
ambient air:
Any unconfined portion of the atmosphere: open air, surrounding
air.
anaerobic: A
biological process which occurs in the absence of oxygen.
aqueous solubility:
The extent to which a compound will dissolve in water. The
log of solubility is generally inversely related to molecular
weight.
aquifer: An
underground geological formation, or group of formations,
containing usable amounts of groundwater that can supply wells
and springs.
aromatic: A
type of hydrocarbon, such as benzene or toluene, added to
gasoline in order to increase octane. Some aromatics are toxic.
artesian: Water
held under pressure in porous rock or soil confined by impermeable
geologic formations. An artesian well is free flowing.
asbestos abatement:
Procedures to control fiber release from asbestos-containing
materials in a building or to remove them entirely, including
removal, encapsulation, repair, enclosure, encasement, and
operations and maintenance programs.
asbestos: A
mineral fiber that can pollute air or water and cause cancer
or asbestosis when inhaled. EPA has banned or severely restricted
its use in manufacturing and construction.
attainment area:
An area considered to have air quality as good as or better
than the national ambient air quality standards as defined
in the Clean Air Act. An area may be an attainment area for
one pollutant and a non-attainment area for others.
Back to the Index
B
backflow:
A reverse flow condition, created by a difference in water
pressures, which causes water to flow back into the distribution
pipes of a potable water supply from any source or sources
other than an intended source. Also see backsiphonage and
cross-connection.
background level:
In air pollution control, the concentration of air pollutants
in a definite area during a fixed period of time prior to
the starting up or on the stoppage of a source of emission
under control. In toxic substances monitoring, the average
presence in the environment, originally referring to naturally
occurring phenomena.
bacteria: (Singular
'bacterium') Microscopic living organisms that can aid in
pollution control by metabolizing organic matter in sewage,
oil spills or other pollutants. However, bacteria in soil,
water or air can also cause human, animal and plant health
problems.
baffle: A flat
board or plate, deflector, guide or similar device constructed
or placed in flowing water or slurry systems to cause more
uniform flow velocities, to absorb energy, and to divert,
guide, or agitate liquids (water, chemical solutions, slurry).
berm: A sloped
wall or embankment (typically constructed of earth, hay bales,
or timber framing) used to prevent inflow or outflow of material
into/from an area.
best available technology (BAT):
The best technology treatment techniques, or other means which
the Administrator finds, after examination for efficacy under
field conditions and not solely under laboratory conditions,
are available (taking cost into consideration). For the purposes
of setting MCLs for synthetic organic chemicals, any BAT must
be at least as effective as granular activated carbon.
best management practices (BMPs):
Structural, nonstructural and managerial techniques that are
recognized to be the most effective and practical means to
control nonpoint source pollutants yet are compatible with
the productive use of the resource to which they are applied.
BMPs are used in both urban and agricultural areas.
bioaccumulants: Substances that increase in concentration
in living organisms as they take in contaminated air, water,
or food because the substances are very slowly metabolized
or excreted.
bioassay: A
method used to determine the toxicity of specific chemical
contaminants. A number of individuals of a sensitive species
are placed in water containing specific concentrations of
the contaminant for a specified period of time.
bioaugmentation:
The introduction of cultured microorganisms into the subsurface
environment for the purpose of enhancing bioremediation of
organic contaminants. Generally the microorganisms are selected
for their ability to degrade the organic compounds present
at the remediation site. The culture can be either an isolated
genus or a mix of more than one genera. Nutrients are usually
also blended with the aqueous solution containing the microbes
to serve as a carrier and dispersant. The liquid is introduced
into the subsurface under natural conditions (gravity fed)
or injected under pressure.
biochemicals:
Chemicals that are either naturally occurring or identical
to naturally occurring substances. Examples include hormones,
pheromones, and enzymes. Biochemicals function as pesticides
through non-toxic, non-lethal modes of action, such as disrupting
the mating pattern of insects, regulating growth, or acting
as repellants. Biochemicals tend to be environmentally compatible
and are thus important to Integrated Pest Management programs.
biodegradable:
The ability of a substance to be broken down physically and/or
chemically by microorganisms. For example, many chemicals,
food scraps, cotton, wool, and paper are bio-degradable; plastics
and polyester generally are not.
biodiversity:
The number and variety of different organisms in the ecological
complexes in which they naturally occur. Organisms are organized
at many levels, ranging from complete ecosystems to the biochemical
structures that are the molecular basis of heredity. Thus,
the term encompasses different ecosystems, species, and genes
that must be present for a healthy environment. A large number
of species must characterize the food chain, representing
multiple predator-prey relationships.
biologicals:
Vaccines, cultures and other preparations made from living
organisms and their products, intended for use in diagnosing,
immunizing, or treating humans or animals, or in related research.
biomass: All
of the living material in a given area; often refers to vegetation.
biome: Entire
community of living organisms in a single major ecological
area.
bioremediation:
The use of living organisms (e.g., bacteria) to clean up oil
spills or remove other pollutants from soil, water, and wastewater,
use of organisms such as non-harmful insects to remove agricultural
pests or counteract diseases of trees, plants, and garden
soil.
biosphere: The
portion of Earth and its atmosphere that can support life.
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
to remove toxics from bodies of water, or act as pesticides.
black water:
Water that contains animal, human, or food waste.
bloom (algal):
A proliferation of algae and/or higher aquatic plants in a
body of water; often related to pollution, especially when
pollutants accelerate growth.
bog: A type
of wetland that accumulates appreciable peat deposits. Bogs
depend primarily on precipitation for their water source,
and are usually acidic and rich in plant residue with a conspicuous
mat of living green moss.
bottom ash:
The non-airborne combustion residue from burning pulverized
coal in a boiler; the material which falls to the bottom of
the boiler and is removed mechanically; a concentration of
the non-combustible materials, which may include toxics.
brackish: Mixed
fresh and salt waters.
brine mud: Waste
material, often associated with well-drilling or mining, composed
of mineral salts or other inorganic compounds.
buffer strips:
Strips of grass or other close-growing vegetation that separate
a waterway (ditch, stream, creek) from an intensive land use
area (subdivision, farm); also referred to as filter strips,
vegetated filter strips, and grassed buffers.
by-product:
Material, other than the principal product, generated as a
consequence of an industrial process.
Back to the Index
C
cancer:
A disease
characterized by the rapid and uncontrolled growth of aberrant
cells into malignant tumors.
cap:
A fairly impermeable seal, usually composed of clay-type
soil or a combination of clay soil and synthetic liner, which
is placed over a landfill during closure. The cap serves to
minimize leachate volume during biodegradation of the waste
by keeping precipitation from percolating through the landfill.
The cap also keeps odors down and animal scavengers from gathering.
carbon dioxide:
A colorless, odorless, gas produced by burning
fossil fuels, sometimes referred to as a green house gas because
it contibutes to earth warming.
carbon monoxide:
A colorless, odorless, poisonous gas produced by incomplete
fossil fuel combustion.
carcinogen:
Any
substance that can cause or aggravate cancer.
cask:
A
thick-walled container (usually lead) used to transport
radioactive material. Also called a coffin.
catalyst:
A substance
that changes the speed or yield of a chemical reaction without
being consumed or chemically changed by the chemical reaction.
catalytic converter:
An air pollution abatement device that removes pollutants 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 that oxidizes volatile
organic compounds (VOCs) by using a catalyst to promote the
combustion process. Catalytic incinerators require lower temperatures
than conventional thermal incinerators, thus saving fuel and
other costs.
chelation: A chemical complexing (forming or joining together)
of metallic cations (such as copper) with certain organic
compounds, such as EDTA (ethylene diamine tetracetic acid).
Chelation is used to prevent the precipitation of metals (copper).
chisel plowing: Preparing croplands by using a special implement
that avoids complete inversion of the soil as in with conventional
plowing. Chisel plowing can leave a protective cover or crop
residues on the soil surface to help prevent erosion and improve
filtration.
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.
chlorination: Adding chlorine to water or wastewater, generally
for the purpose of disinfection, but frequently for accomplishing
other biological or chemical results. Chlorine also is used
almost universally in manufacturing processes, particularly
for the plastics industry.
chlorofluorocarbons (CFCs): A family of inert, nontoxic, and
easily liquified chemicals used in refrigeration, air conditioning,
packaging, insulation, or as solvents and aerosol propellants.
Because CFCs are not destroyed in the lower atmosphere they
drift into the upper atmosphere where their chlorine components
destroy ozone.
chlorophenoxy: A class of herbicides that may be found in
domestic water supplies and cause adverse health effects.
Two widely used chlorophenoxy herbicides are 2,4-D (2,4-Dichlorophenoxy
acetic acid) and 2,4,5-TP (2,4,5-Trichlorophenoxy propionic
acid (silvex)).
chlorophyll: A chemical mixture or compound found in the chloroplasts
of plant cells and gives plants their green color. Plants
use chlorophyll to convert the energy of sunlight to food
in the process known as photosynthesis.
chlorosis: Discoloration of normally green plant parts caused
by disease, lack of nutrients, or various air pollutants.
cholinesterase: An enzyme found in animals that regulates
nerve impulses. Cholinesterase inhibition is associated with
a variety of acute symptoms such as nausea, vomiting, blurred
vision, stomach cramps, and rapid heart rate.
chronic effect: An adverse effect on a human or animal in
which symptoms recur frequently or develop slowly over a long
period of time.
cistern: A small tank (usually covered) or a storage facility
used to store water for a home or farm. Often used to store
rain water.
clarifer: A large circular or rectangular tank or basin in
which water is held for a period of time, during which the
heavier suspended solids settle to the bottom. Clarifiers
are also called settling basins and sedimentation basins.
class I area: Under the Clean Air Act, a Class I area is one
in which visibility is protected more stringently than under
the national ambient air quality standards; includes national
parks, wilderness area, monuments and other areas of special
national and cultural significance.
clean coal technology: Any technology not in widespread use
prior to the Clean Air Act amendments of 1990. This Act will
achieve significant reductions in pollutants associated with
the burning of coal.
clean fuels: Blends or substitutes for gasoline fuels, including
compressed natural gas, methanol, ethanol, liquified petroleum
gas, and others.
clear cut: Harvesting all the trees in one area at one time,
a practice that can encourage fast rainfall or snowmelt runoff,
erosion, sedimentation of streams and lakes, flooding, and
destroys vital habitat.
clear well: A reservoir for storing filtered water of sufficient
quantity to prevent the need to vary the filtration rate with
variations in demand. Also used to provide chlorine contact
time for disinfection.
climate change: This term is commonly used interchangeably
with "global warming" and "the greenhouse effect,"
but is a more descriptive term. Climate change refers to the
buildup of man-made gases in the atmosphere that trap the
suns heat, causing changes in weather patterns on a global
scale. The effects include changes in rainfall patterns, sea
level rise, potential droughts, habitat loss, and heat stress.
The greenhouse gases of most concern are carbon dioxide, methane,
and nitrous oxides. If these gases in our atmosphere double,
the earth could warm up by 1.5 to 4.5 degrees by the year
2050, with changes in global precipitation having the greatest
consequences.
cloning: In biotechnology, obtaining a group of genetically
identical cells from a single cell; making identical copies
of a gene.
closed-loop recycling: Reclaiming or reusing wastewater for
non-potable purposes in an enclosed process.
closure: The procedure a landfill operator must follow when
a landfill reaches its legal capacity for solid waste: ceasing
acceptance of solid waste and placing a cap on the landfill
site. No more waste can be accepted and a cap usually is placed
over the site. The cap is then planted with grasses and other
ground covers. Post-closure care includes monitoring ground
water, landfill gases, and leachate collection systems, sometimes
for as long as 30 years.
coagulants: Chemicals that cause very fine particles to clump
together into larger particles. This makes it easier to separate
the solids from the water by settling, skimming, draining
or filtering.
coastal zone: Lands and waters adjacent to the coast that
exert an influence on the uses of the sea and its ecology,
or whose uses and ecology are affected by the sea.
cohesion: Molecular attraction which holds two particles together.
coliform organism: Microorganisms found in the intestinal
tract of humans and animals. Their presence in water indicates
fecal pollution and potentially dangerous bacterial contamination
by disease-causing microorganisms.
colloids: Very small, finely divided solids (particles that
do not dissolve) that remain dispersed in a liquid for a long
time due to their small size and electrical charge. When most
of the particles in water have a negative electrical charge,
they tend to repel each other. This repulsion prevents the
particles from clumping together, becoming heavier, and settling
out.
combustion: 1. Burning, or rapid oxidation, accompanied by
release of energy in the form of heat and light. A basic cause
of air pollution. 2. Refers to controlled burning of waste,
in which heat chemically alters organic compounds, converting
into stable inorganics such as carbon dioxide and water.
commercial waste: All solid waste from businesses. This category
includes, but is not limited to, solid waste originating in
stores, markets, office buildings, restaurants, shopping centers,
and theaters.
comminution: Mechanical shredding or pulverizing of waste.
Used in both solid waste management and wastewater treatment.
community water system (CWS): A public water system which
serves at least 15 service connections used by yearround residents
or regularly serves at least 25 year-round residents. Also
see non-community water system, transient water system and
non-transient non-community water system.
compost: Decomposed organic material that is produced when
bacteria in soil break down garbage and biodegradable trash,
making organic fertilizer. Making compost requires turning
and mixing and exposing the materials to air. Gardeners and
farmers use compost for soil enrichment. The relatively stable
humus material that is produced from a composting process
in which bacteria in soil mixed with garbage and degradable
trash break down the mixture into organic fertilizer.
compressed natural gas (CNG): An alternative fuel for motor
vehicles; considered one of cleanest because of low hydrocarbon
emissions and its vapors are relatively non-ozone producing.
However, it does emit a significant quantity of nitrogen oxides.
condensation: The process by which a liquid is removed from
a vapor. In the water cycle, water vapor rises, cools, and
condenses, sometimes clinging to tiny particles of dust in
the atmosphere. Condensed water vapor either remains a liquid
or turns directly into a solid (ice, hail or snow). Clouds
are formed by condensed water particles.
conductance: A rapid method of estimating the dissolvedsolids
content of a water supply. The measurement indicates the capacity
of a sample of water to carry an electrical current, which
is related to the concentration of ionized substances in the
water.
cone of depression: The area around a discharging well where
the hydraulic head (potentiometric surface) in the aquifer
has been lowered by pumping. In an unconfined aquifer, the
cone of depression is a cone-shaped depression in the water
table where the media has actually been dewatered.
confined aquifer: An aquifer in which ground water is confined
under pressure which is significantly greater than atmospheric
pressure. See artesian aquifer.
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 EPA initiated regulatory enforcement
actions to resolve the contamination at the Superfund site
involved. The consent decree describes the actions PRPs will
take and may be subject to a public comment period.
conservation: Preserving and renewing natural resources to
assure their highest economic or social benefit over the longest
period of time. Clean rivers and lakes, wilderness areas,
a diverse wildlife population, healthy soil, and clean air
are natural resources worth conserving for future generations.
construction and demolition waste: Waste building materials,
dredging materials, tree stumps, and rubble resulting from
construction, remodeling, repair, and
demolition of homes, commercial buildings and other structures
and pavements. May contain lead, asbestos, or other hazardous
substances.
consumptive use: Water removed from available supplies without
direct return to a water resource system for uses such as
manufacturing, agriculture, and food preparation.
contact pesticide: A chemical that kills pests when it touches
them, instead of by ingestion. Also, soil that contains the
minute skeletons of certain algae that scratch and dehydrate
waxy-coated insects.
contaminant: Any physical, chemical, biological, or radiological
substance or matter that has an adverse affect on air, water,
or soil.
continuous discharge: A permitted release of pollutants into
the environment that occurs without interruption, except for
infrequent shutdowns for maintenance, process changes, etc.
contour farming: A conservation-based method of farming in
which all farming operations (for example, tillage and planting)
are performed across (rather than up and down) the slope.
Ideally, each crop row is planted at right angles to the ground
slope.
contour strip farming: A kind of contour farming in which
row crops are planted in strips, between alternating strips
of close-growing, erosionresistant forage crops.
conventional filtration: A method of treating water to remove
particulates. The method consists of the addition of coagulant
chemicals, flash mixing, coagulation flocculation, sedimentation
and filtration.
conventional tillage: The traditional method of farming in
which soil is prepared for planting by completely inverting
it with a moldboard plow. Subsequent working of the soil with
other implements is usually performed to smooth the soil surface.
Bare soil is exposed to the weather for some varying length
of time depending on soil and climatic conditions.
conveyance loss: Water lost in conveyance (pipe, channel,
conduit, ditch) by leakage or evaporation.
core: The uranium-containing heart of a nuclear reactor, where
energy is released.
cover crop: A crop that provides temporary protection for
delicate seedlings and/or provides a canopy for seasonal soil
protection and improvement between normal
crop production periods. Except in orchards where permanent
vegetative cover is maintained, cover crops usually are grown
for one year of less. When plowed under and incorporated into
the soil, cover crops are also referred to as gren manure
crops.
cradle-to-grave or manifest system: A procedure in which hazardous
materials are identified and followed as they are produced,
treated, transported, and disposed of by a series of permanent,
linkable, descriptive documents (e.g., manifests). Commonly
referred to as the cradle-to-grave system.
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.
crop rotation: A system of farming in which a regular succession
of different crops are planted on the same land area, as opposed
to growing the same crop time after time (monoculture).
cryptosporidium: A protozoan associated with the disease cryptosporidiosis
in humans. The disease can be transmitted through ingestion
of drinking water, person-to-person contact, or other exposure
routes. Cryptosporidiosis may cause acute diarrhea, abdominal
pain, vomiting, and fever that last 1-2 weeks in healthy adults,
but may be chronic or fatal in immuno-compromised people.
cumulative exposure: The summation of exposures of an organism
to a chemical over a period of time.
curie: A measure of radioactivity. One Curie of radioactivity
is equivalent to 3.7 x 1010 or 37,000,000,000 nuclear disintegrations
per second.
Back to the Index
D
DDT: The first chlorinated hydrocarboninsecticide
chemical name: Dichloro-Diphenyl-Trichloroethane. 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.
decant: To draw off the upper layer of liquid (water) after
the heavier material (a solid or another liquid) has settled.
decay products: Degraded radioactive materials, often referred
to as "daughters" or "progeny"; radon
decay products of most concern from a public health standpoint
are polonium-214 and polonium-218.
decomposition: The conversion of chemically unstable materials
to more stable forms by chemical or biological action. If
organic matter decays when there is no oxygen present (anaerobic
conditions or putrefaction), undesirable tastes and odors
are produced. Decay of organic matter when oxygen is present
(aerobic conditions) tends to produce much less objectionable
tastes and odors.
decontamination: Removal of harmful substances such as noxious
chemicals, harmful bacteria or other organisms, or radioactive
material from exposed individuals, rooms and furnishings in
buildings, or the exterior environment.
deep well injection: A process by which waste fluids are injected
deep below the surface of the earth.
defoliant: An herbicide that removes leaves from trees and
growing plants.
degasification: A water treatment process which removes dissolved
gases from the water. The gases may be removed by either mechanical
or chemical treatment methods or a combination of both.
degradation: Chemical or biological breakdown of a complex
compound into simpler compounds.
denitrification: Bacterial reduction of nitrite to gaseous
nitrogen under anaerobic conditions.
density: A measure of how heavy a solid, liquid, or gas is
for its size. Density is expressed in terms of weight per
unit volume, that is, grams per cubic centimeter or pounds
per cubic foot. The density of water is 1.0 gram per cubic
centimeter or about 62.4 pounds per cubic foot.
dermal toxicity: The ability of a pesticide or toxic chemical
to poison people or animals by contact with the skin.
desalination: 1) Removing salts from ocean or brackish water
by using various technologies. 2) Removal of salts from soil
by artificial means, usually leaching.
desiccant: A chemical agent that absorbs moisture; some desiccants
are capable of drying out plants or insects, causing death.
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.
destratification: The development of vertical mixing within
a lake or reservoir to eliminate (either totally or partially)
separate layers of temperature, plant, or animal life. This
vertical mixing can be caused by mechanical means (pumps)
or through the use of forced air diffusers which release air
into the lower layers of the reservoir.
detritus: Loose fragments, particles, or grains formed by
the disintegration of rocks.
diatomaceous earth (diatomite): A chalk-like material (fossilized
diatoms) used to filter out solid waste in wastewater treatment
plants, also used as an active ingredient in some powdered
pesticides.
diffusion: The movement of suspended or dissolved particles
from a more concentrated to a less concentrated area. The
process tends to distribute the particles more uniformly.
digestion: The biochemical decomposition of organic matter,
resulting in partial gasification, liquefaction, and mineralization
of pollutants.
dimictic: Lakes and reservoirs which freeze over and normally
go through two stratification and two mixing cycles within
a year.
dioxin: Any of a family of compounds known chemically as dibenzo-p-dioxins.
Concern about them arises from their potential toxicity and
contaminants in commercial products. Tests on laboratory animals
indicate that it is one of the more toxic man-made compounds.
direct runoff: Water that flows over the ground surface or
through the ground directly into streams, rivers, or lakes.
discharge: Flow of surface water in a stream or canal or the
outflow of ground water from a flowing artesian well, ditch,
or spring. Can also apply to discharge of liquid effluent
from a facility or of chemical emissions into the air through
designated venting mechanisms.
disinfectant: Any oxidant, including but not limited to chlorine,
chlorine dioxide, chloramines, and ozone, that is added to
water in any part of the treatment or distribution process
and is intended to kill or inactivate pathogenic microorganisms.
dispersant: A chemical agent used to break up concentrations
of organic material such as spilled oil.
disposal: Final placement or destruction of toxic, radioactive,
or other wastes; surplus or banned pesticides or other chemicals;
polluted soils; and drums containing hazardous materials from
removal actions or accidental releases. Disposal may be accomplished
through use of approved secure landfills, surface impoundments,
land farming, deep-well injection, ocean dumping, or incineration.
dissolved oxygen: The oxygen freely available in water, vital
to fish and other aquatic life and for the prevention of odors.
DO levels are considered a most important indicator of a water
body's ability to support desirable aquatic life. Secondary
and advanced waste treatment are generally designed to ensure
adequate DO in waste-receiving waters.
dissolved solids: Disintegrated organic and inorganic material
in water. Excessive amounts make water unfit to drink or use
in industrial processes.
distillation: The act of purifying liquids through boiling,
so that the steam condenses to a pure liquid and the pollutants
remain in a concentrated residue.
drainage: A technique to improve the productivity of some
agricultural land by removing excess water from the soil;
surface drainage is accomplished with open
ditches; subsurface drainage uses porous conduits (drain tile)
buried beneath the soil surface.
drawdown: 1) The drop in the water table or level of water
in the ground when water is being pumped from a well. 2) The
amount of water used from a tank or reservoir. 3) The drop
in the water level of a tank or reservoir.
dredging: Removal of mud from the bottom of water bodies.
This can disturb the ecosystem and causes silting that kills
aquatic life. Dredging of contaminated muds can expose biota
to heavy metals and other toxics. Dredging activities may
be subject to regulation under Section 404 of the Clean Water
Act.
dump: A land site where wastes are discarded in a disorderly
or haphazard fashion without regard to protecting the environment.
Uncontrolled dumping is an indiscriminate and illegal form
of waste disposal. Problems associated with dumps include
multiplication of disease-carrying organisms and pests, fires,
air and water pollution, unsightliness, loss of habitat, and
personal injury.
dystrophic lakes: Acidic, shallow bodies of water that contain
much humus and/or other organic matter; contain many plants
but few fish.
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E
ecological impact: The effect that a man-made
or natural activity has on living organisms and their non-living
(abiotic) environment.
ecological indicator: A characteristic of the environment
that, when measured, quantifies magnitude of stress, habitat
characteristics, degree of exposure to a stressor, or ecological
response to exposure. The term is a collective term for response,
exposure. The term is a collective term for response, exposure,
habitat, and stressor indicators.
ecological risk assessment: The application of a formal framework,
analytical process, or model to estimate the effects of human actions(s) on a natural resource and to interpret the significance
of those effects in light of the uncertainties identified
in each component of the assessment process. Such analysis
includes initial hazard identification, exposure and doseresponse
assessments, and risk characterization.
ecology: The study of the relationships between all living
organisms and the environment, especially the totality or
pattern of interactions; a view that includes all plant and
animal species and their unique contributions to a particular
habitat.
ecosystem: The interacting synergism of all living organisms
in a particular environment; every plant, insect, aquatic
animal, bird, or land species that forms a complex web of
interdependency. An action taken at any level in the food
chain, use of a pesticide for example, has a potential domino
effect on every other occupant of that system.
effluent: Water or some other liquid-raw, partially or completely
treated-flowing from a reservoir, basin, treatment process
or treatment plant.
electrodialysis: A process that uses electrical current applied
to permeable membranes to remove minerals from water. Often
used to desalinize salty or brackish water.
electrolyte: A substance which dissociates (separates) into
two or more ions when it is dissolved in water.
electrostatic precipitator (ESP): A device that removes particles
from a gas stream (smoke) after combustion occurs. The ESP
imparts an electrical charge to the particles, causing them
to adhere to metal plates inside the precipitator. Rapping
on the plates causes the particles to fall into a hopper for
disposal.
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 cap: A limit designed to prevent projected growth
in emissions from existing and future stationary sources from
eroding any mandated reduction. Generally, such provisions
require any emission growth from facilities under the restrictions
be offset by equivalent reductions at other facilities under
the same cap.
emissions trading: The creation of surplus emission reductions
at certain stacks, vents, or similar emissions sources and
the use of this surplus to meet or redefine pollution requirements
applicable to other emission sources. This allows one source
to increase emissions when another sources reduces them, maintaining
an overall constant emission level. Facilities that reduce
emissions substantially may "bank" their "credits"
or sell them to other industries.
encapsulation: The treatment of asbestos-containing material
with a liquid that covers the surface with a protective coating
or embeds fibers in an adhesive matrix to prevent their release
into the air.
endangered species: Animals, birds, fish, plants, or other
living organisms threatened with extinction by man-made or
natural changes in their environment. Requirements for declaring
a species endangered are contained in the Endangered Species
Act.
endangerment assessment: A site-specific risk assessment of
the actual or potential danger to human health or welfare
and the environment from the release of hazardous substances
or waste. The endangerment assessment document is prepared
in support of enforcement actions under CERCLA or RCRA.
endemic: Something peculiar to a particular people or locality,
such as a disease which is always present in the population.
Endrin: a pesticide toxic to freshwater and marine aquatic
life that produces adverse health effects in domestic water
supplies.
energy recovery: To capture energy from waste through any
of a variety of processes (e.g., burning). Many new technology
incinerators are waste-to-energy recovery units.
enrichment: The addition of nutrients (e.g., nitrogen, phosphorus,
carbon compounds) from sewage effluent or agricultural runoff
to surface water, greatly increases the growth potential for
algae and other aquatic plants.
enteric: Of intestinal origin, especially applied to wastes
or bacteria.
environment: The sum of all external conditions affecting
the life, development and survival of an organism.
environmental assessment (EA): An environmental analysis prepared
pursuant to the National Environmental Policy Act to determine
whether a federal action would significantly affect the environment
and thus require a more detailed environmental impact statement.
environmental audit: An independent assessment (not conducted
by EPA) of a facility's compliance policies, practices, and
controls. Many pollution prevention initiatives require an
audit to determine where wastes may be reduced or eliminated
or energy conserved. Many supplemental environmental projects
that offset a penalty use audits to identify ways to reduce
the harmful effects of a violation.
environmental equity: Equal protection from environmental
hazards for individuals, groups, or communities regardless
of race, ethnicity, or economic status.
environmental exposure: Human exposure to pollutants originating
from facility emissions. Threshold levels are not necessarily
surpassed, but low level chronic pollutant exposure is one
of the most common forms of environmental exposure.
environmental impact statement (EIS): A document prepared
by or for EPA which identifies and analyzes, in detail, environmental
impacts of a proposed action. As a tool for decision-making,
the EIS describes positive and negative effects and lists
alternatives for an undertaking, such as development of a
wilderness area. (Required by NEPA : see Federal Law Section).
environmental technology: An all-inclusive term used to describe
pollution control devices and systems, waste treatment processes
and storage facilities, and site remediation technologies
and their components that may be utilized to remove pollutants
or contaminants from, or to prevent them from entering, the
environment. Examples include wet scrubbers (air), soil washing
(soil), granulated activated carbon unit (water), and filtration
(air, water). Usually, this term applies to hardware-based
systems; however, it can also apply to methods or techniques
used for pollution prevention, pollutant reduction, or containment
of contamination to prevent further movement of the contaminants,
such as capping, solidification or vitrification, and biological
treatment.
enzyme: (a) any of numerous proteins or conjugated proteins
produced by living organisms and functioning as biochemical
catalysts. (b) a protein that a living organism uses in the
process of degrading a specific compound. The protein serves
as a catalyst in the compound's biochemical transformation.
epidemic: Widespread outbreak of a disease, or a large number
of cases of a disease in a single community or relatively
small area. Disease may spread from person to person, and/or
by the exposure of many persons to a single source, such as
a water supply.
epidemiology: The study of the occurrence and causes of health
effects in human populations. An epidemiological study often
compares two groups of people who are alike except for one
factor, such as exposure to a chemical or the presence of
a health effect. The investigators try to determine if any
factor is associated with thehealth effect.
erosion: The wearing away of land surface by wind or water,
intensified by land-clearing practices related to farming,
residential or industrial development, road building, or logging.
estuary: A complex ecosystem between a river and near-shore
ocean waters where fresh and salt water mix. These brackish
areas include bays, mouths of rivers, salt marshes, wetlands,
and lagoons and are influenced by tides and currents. Estuaries
provide valuable habitat for marine animals, birds, and other
wildlife.
ethanol: An alternative automotive fuel derived from grain
and corn; usually blended with gasoline to form gasohol.
eutrophic lakes: Shallow, murky bodies of water with concentrations
of plant nutrients causing excessive production of algae.
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 due to higher levels of nutritive compounds such as nitrogen
and phosphorus. Human activities can accelerate the process.
evaporation: The process by which water or other liquid becomes
a gas (water vapor or ammonia vapor). Water from land areas,
bodies of water, and all other moist surfaces is absorbed
into the atmosphere as a vapor.
evaporation ponds: Areas where sewage sludge is dumped and
dried.
evapotranspiration: The combined processes of evaporation
and transpiration. It can be defined as the sum of water used
by vegetation and water lost by evaporation.
ex situ: Moved from its original place; excavated; removed
or recovered from the subsurface.
exotic species: A species that is not indigenous to a region.
explosive limits: The amounts of vapor in the air that form
explosive mixtures; limits are expressed as lower and upper
limits and give the range of vapor concentrations in air that
will explode if an ignition source is present.
exposure: Radiation or pollutants that come into contact with
the body and present a potential health threat. The most common
routes of exposure are through the skin, mouth, or by inhalation.
exposure assessment: The determination or estimation (qualitative
or quantitative) of the magnitude, frequency, duration, route,
and extent (number of people) of
exposure to a chemical.
exposure level (chemical): The amount (concentration) of a
chemical at the absorptive surfaces of an organism.
extremely hazardous substances (EHS): Any of 366 (+ or:) chemicals
or hazardous substances identified by EPA on the basis of
hazard or toxicity and listed under EPCRA. The list is periodically
revised.
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F
facilities plans: Plans and studies related
to the construction of treatment works necessary to comply
with the Clean Water Act or RCRA. A facilities plan investigates
needs and provides information on the cost effectiveness of
alternatives, a recommended plan, an environmental assessment
of the recommendations, and descriptions of the treatment
works, costs, and a completion schedule.
facultative: Used to describe organisms that are able to grow
in either the presence or absence of a specific environmental
factor (e.g., oxygen). See also facultative anaerobe.
feasibility study: 1. Analysis of the practicability of a
proposal; e.g., a description and analysis of potential cleanup
alternatives for a site such as one 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". 2. A small-scale
investigation of a problem to ascertain whether a proposed
research approach is likely to provide useful data.
fecal coliform bacteria: Bacteria found in the intestinal
tracts of animals. Their presence in water or sludge is an
indicator of pollution and possible contamination by pathogens.
feedlot: A confined area for the controlled feeding of animals.
Tends to concentrate large amounts of animal waste that cannot
be absorbed by the soil and, hence, may be carried to nearby
streams or lakes by rainfall runoff.
feedstock: Raw material supplied to a machine or processing
plant from which other products can be made. For example,
polyvinyl chloride and polyethylene are raw chemicals used
to produce plastic tiles, mats, fenders, cushions, and traffic
cones.
field capacity: The maximum amount of water that a soil can
retain after excess water from saturated conditions has been
drained by the force of gravity.
filling: Depositing dirt, mud or other materials into aquatic
areas to create more dry land, usually for agricultural or
commercial development purposes, often with ruinous ecological
consequences.
filter strip: Strip or area of vegetation used for removing
sediment, organic matter, and other pollutants from runoff
and waste water.
filtration: A treatment process, under the control of qualified
operators, for removing solid (particulate) matter from water
by means of porous media such as sand or a man-made filter;
often used to remove particles that containing pathogens.
finished water: Water that has passed through a water treatment
plant; all the treatment processes are completed or "finished".
This water is ready to be delivered to consumers. Also called
product water.
first draw: The water that comes out when a faucet in the
kitchen or bathroom is first opened, which is likely to have
the highest level of lead contamination from old plumbing
solder and pipes.
fish kill: When aquatic life within a river, lake, or stream
dies in a mass extinction.
flare: A device that burns gaseous materials to prevent them
from being released into the environment. Flares may operate
continuously or intermittently and are usually found on top
of a stack. Flares also burn off methane gas in a landfill.
flash point: The lowest temperature at which evaporation of
a substance produces enough vapor to form an ignitable mixture
with air.
flocculation: The gathering together of fine particles in
water by gentle mixing after the addition of coagulant chemicals
to form larger particles.
floodplain: Mostly level land along rivers and streams that
may be submerged by floodwater. A 100-year floodplain is an
area which can be expected to flood once in every 100 years.
flow rate: The rate, expressed in gallons-or liters-per-hour,
at which a fluid escapes from a hole or fissure in a tank.
Such measurements are also made of liquid waste, effluent,
and surface water movement.
flue gas: The air coming out of a chimney after combustion
in the burner it is venting. It can include nitrogen oxides,
carbon oxides, water vapor, sulfur oxides, particles and many
chemical pollutants.
flue gas desulfurization: A technology that employs a sorbent,
usually lime or limestone, to remove sulfur dioxide from the
gases produced by burning fossil fuels. Flue gas desulfurization
is current state-of-the art technology for major SO2 emitters,
like power plants.
fluidized: A mass of solid particles that is made to flow
like a liquid by injection of water or gas is said to have
been fluidized. In water treatment, a bed of filter media
is
fluidized by backwashing water through the filter.
flume: A natural or man-made channel that diverts water.
fluoridation: The addition of a chemical to increase the concentration
of fluoride ions in drinking water to a predetermined optimum
limit to reduce the incidence (number) of dental caries (tooth
decay) in children. Defluoridation is the removal of excess
fluoride in drinking water to prevent the mottling (brown
stains) of teeth.
fluorides: Gaseous, solid, or dissolved compounds containing
fluorine that result from industrial processes. Excessive
amounts in food can lead to fluorosis.
fluorocarbons (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 for domestic aerosols, they are now found mainly
in coolants and some industrial processes. FCs containing
chlorine are called chlorofluorocarbons (CFCs). They are believed
to be modifying the ozone layer in the stratosphere, thereby
allowing more harmful solar radiation to reach the Earth's
surface.
fogging: Applying a pesticide by rapidly heating the liquid
chemical so that it forms very fine droplets that resemble
smoke or fog. Used to destroy mosquitoes, black flies, and
similar pests.
food chain: A sequence of organisms, each of which uses the
next, lower member of the sequence as a food source.
formaldehyde: A colorless, pungent, and irritating gas, CH20,
used chiefly as a disinfectant and preservative and in synthesizing
other compounds like resins.
fossil fuel: Fuel derived from ancient organic remains, e.g.,
peat, coal, crude oil, and natural gas.
fresh water: Water that generally contains less than 1,000
milligrams-per-liter of dissolved solids
friable: Capable of being crumbled, pulverized, or reduced
to powder by hand pressure.
fuel economy standard: The Corporate Average Fuel Economy
Standard (CAFE) effective in 1978. It enhanced the national
fuel conservation effort imposing a miles-per-gallon floor
for motor vehicles.
fuel efficiency: The proportion of the energy released on
combustion of a fuel that is converted into useful energy.
fugitive emissions: Air pollutants released to the air other
than those from stacks or vents; typically small releases
from leaks in plant equipment such as valves, pump seals,
flanges, sampling connections, etc.
fume: Tiny particles trapped in vapor in a gas stream.
fumigant: A pesticide vaporized to kill pests. Used in buildings
and greenhouses.
fungi: Aerobic, multicellular, nonphotosynthetic, heterotrophic
microorganisms. The fungi include mushrooms, yeast, molds,
and smuts. Most fungi are saprophytes, obtaining their nourishment
from dead organic matter. Along with bacteria, fungi are the
principal organisms responsible for the decomposition of carbon
in the biosphere. Fungi have two ecological advantages over
bacteria: (1) they can grow in low moisture areas, and (2)
they can grow in low pH environments. gate valve: a valve
regulated by the position of a circular plate.
fungicide: A pesticide used to control or destroy fungi on
food or grain crops.
fungistat: A chemical that keeps fungi from growing.
furrow irrigation: Irrigation method in which water travels
through the field by means of small channels between each
row or groups of rows.
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G
galvanize: To coat a metal (especially iron
or steel) with zinc. Galvanization is the process of coating
a metal with zinc.
game fish: Species like trout, salmon, or bass, caught for
sport. Many of them show more sensitivity to environmental
change than "rough" fish.
garbage: Animal and vegetable waste resulting from the handling,
storage, sale, preparation, cooking, and serving of foods.
gas chromatograph/mass spectrometer: Highly sophisticated
instrument that identifies the molecular composition and concentrations
of various chemicals in water and soil samples.
gasification: Conversion of solid material such as coal into
a gas for use as a fuel.
gasohol: Mixture of gasoline and ethanol derived from fermented
agricultural products containing at least nine percent ethanol.
Gasohol emissions contain less carbon monoxide than those
from gasoline.
gastroenteritis: An inflammation of the stomach and intestine
resulting in diarrhea, with vomiting and cramps when irritation
is excessive. When caused by an infectious agent, it is often
associated with fever.
genetic engineering: A process of inserting new genetic information
into existing cells in order to modify an organism for the
purpose of changing particular characteristics.
geographic information system (GIS): A computer system designed
for storing, manipulating, analyzing, and displaying data
in a geographic context.
geological log: A detailed description of all underground
features discovered during the drilling of a well (depth,
thickness and type of formations).
germicide: A substance formulated to kill germs or microorganisms.
The germicidal properties of chlorine make it an effective
disinfectant.
giardia lamblia: Flagellate protozoan which is shed during
its cyst stage into the feces of man and animals. When water
containing these cysts is ingested, the protozoan causes a
severe gastrointestinal disease called giardiasis.
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.
gram: A unit of mass equivalent to one milliliter of water
at 4 degrees Celsius. 1/454 of a pound.
grassed waterway: Natural or constructed watercourse or outlet
that is shaped or graded and established in suitable vegetation
for the disposal of runoff water without erosion.
gray water: Domestic wastewater composed of wash water from
kitchen, bathroom, and laundry sinks, tubs, and washers.
greenhouse effect: The warming of Earth's atmosphere attributed
to a build-up of carbon dioxide or other gases;some scientists
think that this build-up allows the sun's rays to heat Earth,
while infra-red radiation makes the atmosphere opaque to a
counterbalancing loss of heat.
ground water: The supply of fresh water found beneath the
Earth's surface, usually in aquifers, which supply wells and
springs. Because ground water is a major source of drinking
water, there is growing concern over contamination from leaching
agricultural or industrial pollutants or leaking underground
storage tanks.
ground-water discharge: Ground water entering near coastal
waters which has been contaminated by landfill leachate, deep
well injection of hazardous wastes, septic tanks, etc.
gully erosion: Severe erosion in which trenches are cut to
a depth greater than 30 centimeters (a foot). Generally, ditches
deep enough to cross with farm equipment are considered gullies.
Back to the Index
H
habitat: The place where a population (e.g.,
human, animal, plant, microorganism) 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 biochemical
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 self-transmutation or decay.
3. The time required for the elimination of one half a total
dose from the body.
halogen: One of the chemical elements chlorine, bromine, or
iodine.
hard water: Alkaline water containing dissolved salts that
interfere with some industrial processes and prevent soap
from lathering. Water may be considered hard if it has a hardness
greater than the typical hardness of water from the region.
Some textbooks define hard water as water with a hardness
of more than 100 mgAL as calcium carbonate.
hazard evaluation: A component of risk assessment that involves
gathering and evaluating data on the types of health injury
or disease (e.g., cancer) that may be produced by a chemical
and on the conditions of exposure under which injury or disease
is produced.
hazardous air pollutants: Air pollutants which are not covered
by ambient air quality standards but which, as defined in
the Clean Air Act, may reasonably be expected to cause or
contribute to irreversible illness or death. Such pollutants
include asbestos, beryllium, mercury, benzene, coke oven emissions, radionuclides, and vinyl chloride.
hazardous chemical: An EPA designation for any hazardous material
requiring an MSDS under OSHA's Hazard Communication Standard.
Such substances are capable of producing fires and explosions
or adverse health effects like cancer and dermatitis. Hazardous
chemicals are distinct from hazardous waste.
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 substancedesignated by EPA to be reported
if a designated quantity of the substance is spilled in the
waters of the United States or if otherwise released into
the environment.
hazardous waste: A subset of solid wastes that pose substantial
or potential threats to public health or the environment and
meet any of the following criteria: it is specifically listed
as a hazardous waste by EPA; exhibits one or more of the characteristics
of hazardous wastes (ignitability, corrosiveness, reactivity,
and/or toxicity); o is generated by the treatment of hazardous
waste; or is contained in a hazardous waste.
health advisory level: A non-regulatory health-based reference
level of chemical traces (usually in ppm) in drinking water
at which there are no adverse health risks when ingested over
various periods of time. Such levels are established for one
day, 10 days, long term and life-time exposure periods. They
contain a large margin of safety.
heat island effect: A "dome" of elevated temperatures
over an urban area caused by structural and pavement heat
fluxes, and pollutant emissions.
heavy metal: Metallic elements with high atomic weights, e.g.,
mercury, chromium, cadmium, arsenic, and lead; can damage
living things at low concentrations and tend to accumulate
in the food chain.
herbaceous: Any of various types of non-woody plants with
green stems. Herbaceous plants die down to ground level in
the winter.
herbicide: A pesticide designed to control or kill plants,
weeds, or grasses. Almost 70% of all pesticide used by farmers
and ranchers are herbicides. These chemicals have wide-ranging
effects on non-target species (other than those the pesticide
is meant to control).
herbivore: An animal that feeds on plants.
heterotrophic microorganisms: Bacteria and other microorganisms
that use organic matter synthesized by other organisms for
energy and growth.
high-density polyethylene: A material used to make plastic
bottles and other products that produces toxic fumes when
burned.
high-level radioactive waste (HLW): Waste generated in core
fuel of a nuclear reactor, found at nuclear reactors or by
nuclear fuel reprocessing; is a serious threat to anyone who
comes near the waste without shielding.
histology: The study of the structure of cells and tissues;
usually involves microscopic examination of tissue slices.
host: 1. In genetics, the organism, typically a bacterium,
into which a gene from another organism is transplanted. 2.
In medicine, an animal infected or parasitized by another
organism.
hot spot: Localized elliptical areas with concentrations in
excess of the cleanup standard, either a volume defined by
the projection of the surface area through the soil zone that
will be sampled or a discrete horizon within the soil zone
that will be sampled.
household waste (domestic waste): Solid waste, composed of
garbage and rubbish, which normally originated in a private
home or apartment house. Domestic waste may contain a significant
amount of toxic or hazardous waste.
humus: Organic portion of the soil remaining after prolonged
microbial decomposition.
hydrocarbon: Chemicals that consist entirely of hydrogen and
carbon. Hydrocarbons contribute to air pollution problems
like smog.
hydrochlorination: The application of hypochlorite compounds
to water for the purpose of disinfection.
hydrogen peroxide: Hydrogen peroxide is used to increase the
dissolved oxygen content of groundwater to stimulate aerobic
biodegradation of organic contaminants. Hydrogen peroxide
is infinitely soluble in water, but rapidly dissociates to
form a molecule of water [H(2)O] and one-half molecule of
oxygen [O]. Dissolved oxygen concentrations of greater than
1,000 mg/L are possible using hydrogen peroxide, but high
levels of D.O. can be toxic to microorganisms.
hydrogen sulfide: Gas emitted during organic decomposition.
Also a byproduct of oil refining and burning. Smells like
rotten eggs and, in heavy conce |
