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Glossary: L M N
Laboratory Animal Studies:
Investigations using animals as surrogates for humans.
Lagoon:
1. A shallow pond where sunlight, bacterial action, and oxygen work to purify
wastewater; also used for storage of wastewater or spent nuclear fuel rods. 2.
Shallow body of water, often separated from the sea by coral reefs or sandbars.
Land Application:
Discharge of wastewater onto the ground for treatment or reuse. (See:
irrigation.)
Land Ban:
Phasing out of land disposal of most untreated hazardous wastes, as mandated by
the 1984 RCRA amendments.
Land Disposal Restrictions:
Rules that require hazardous wastes to be treated before disposal on land to
destroy or immobilize hazardous constituents that might migrate into soil and
groundwater.
Land Farming (of Waste):
A disposal process in which hazardous waste deposited on or in the soil is
degraded naturally by microbes.
Landfills:
1. Sanitary landfills are disposal sites for non-hazardous solid wastes spread
in layers, compacted to the smallest practical volume, and covered by material
applied at the end of each operating day. 2. Secure chemical landfills are
disposal sites for hazardous waste, selected and designed to minimize the chance
of release of hazardous substances into the environment.
Landscape:
The traits, patterns, and structure of a specific geographic area, including its
biological composition, its physical environment, and its anthropogenic or
social patterns. An area where interacting ecosystems are grouped and repeated
in similar form.
Landscape Characterization:
Documentation of the traits and patterns of the essential elements of the
landscape.
Landscape Ecology:
The study of the distribution patterns of communities and ecosystems, the
ecological processes that affect those patterns, and changes in pattern and
process over time.
Landscape Indicator:
A measurement of the landscape, calculated from mapped or remotely sensed data,
used to describe spatial patterns of land use and land cover across a geographic
area. Landscape indicators may be useful as measures of certain kinds of
environmental degradation such as forest fragmentation.
Langelier Index (LI):
An index reflecting the equilibrium pH of a water with respect to calcium and
alkalinity; used in stabilizing water to control both corrosion and scale
deposition.
Large Quantity Generator:
Person or facility generating more than 2200 pounds of hazardous waste per
month. Such generators produce about 90 percent of the nation's hazardous waste,
and are subject to all RCRA requirements.
Large Water System:
A water system that services more than 50,000 customers.
Laser Induced Fluorescence:
A method for measuring the relative amount of soil and/or groundwater with an
in-situ sensor.
Latency:
Time from the first exposure of a chemical until the appearance of a toxic
effect.
Lateral Sewers:
Pipes that run under city streets and receive the sewage from homes and
businesses, as opposed to domestic feeders and main trunk lines.
Laundering Weir:
Sedimentation basin overflow weir.
LC 50/Lethal Concentration:
Median level concentration, a standard measure of toxicity. It tells how much of
a substance is needed to kill half of a group of experimental organisms in a
given time. (See: LD 50.)
LD 50/ Lethal Dose:
The dose of a toxicant or microbe that will kill 50 percent of the test
organisms within a designated period. The lower the LD 50, the more toxic the
compound.
Ldlo:
Lethal dose low; the lowest dose in an animal study at which lethality occurs.
Leachate:
Water that collects contaminants as it trickles through wastes, pesticides or
fertilizers. Leaching may occur in farming areas, feedlots, and landfills, and
may result in hazardous substances entering surface water, groundwater, or soil.
Leachate Collection System:
A system that gathers leachate and pumps it to the surface for treatment.
Leaching:
The process by which soluble constituents are dissolved and filtered through the
soil by a percolating fluid. (See: leachate.)
Lead (Pb):
A heavy metal that is hazardous to health if breathed or swallowed. Its use in
gasoline, paints, and plumbing compounds has been sharply restricted or
eliminated by federal laws and regulations. (See: heavy metals.)
Lead Service Line:
A service line made of lead which connects the water to the building inlet and
any lead fitting connected to it.
Legionella:
A genus of bacteria, some species of which have caused a type of pneumonia
called Legionnaires Disease.
Lethal Concentration 50:
Also referred to as LC50, a concentration of a pollutant or effluent at which 50
percent of the test organisms die; a common measure of acute toxicity.
Lethal Dose 50:
Also referred to as LD50, the dose of a toxicant that will kill 50 percent of
test organisms within a designated period of time; the lower the LD 50, the more
toxic the compound.
Level of Concern (LOC):
The concentration in air of an extremely hazardous substance above which there
may be serious immediate health effects to anyone exposed to it for short
periods
Life Cycle of a Product:
All stages of a product's development, from extraction of fuel for power to
production, marketing, use, and disposal.
Lifetime Average Daily Dose:
Figure for estimating excess lifetime cancer risk.
Lifetime Exposure:
Total amount of exposure to a substance that a human would receive in a lifetime
(usually assumed to be 70 years).
Lift:
In a sanitary landfill, a compacted layer of solid waste and the top layer of
cover material.
Lifting Station:
(See: pumping station.)
Light Non-Aqueous Phase Liquid (LNAPL):
A non-aqueous phase liquid with a specific gravity less than 1.0. Because the
specific gravity of water is 1.0, most LNAPLs float on top of the water table.
Most common petroleum hydrocarbon fuels and lubricating oils are LNAPLs.
Light-Emitting Diode:
A long-lasting illumination technology used for exit signs which requires very
little power
Limestone Scrubbing:
Use of a limestone and water solution to remove gaseous stack-pipe sulfur before
it reaches the atmosphere.
Limit of Detection (LOD):
The minimum concentration of a substance being analyzed test that has a 99
percent probability of being identified.
Limited Degradation:
An environmental policy permitting some degradation of natural systems but
terminating at a level well beneath an established health standard.
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 thrive.
Limnology:
The study of the physical, chemical, hydrological, and biological aspects of
fresh water bodies.
Lindane:
A pesticide that causes adverse health effects in domestic water supplies and is
toxic to freshwater fish and aquatic life.
Liner:
1. A relatively impermeable barrier designed to keep leachate inside 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. They will very selectively
disperse through the environment via uptake in living tissue.
Liquefaction:
Changing a solid into a liquid.
Liquid Injection Incinerator:
Commonly used system that relies on high pressure to prepare liquid wastes for
incineration by breaking them up into tiny droplets to allow easier combustion.
Listed Waste:
Wastes listed as hazardous under RCRA but which have not been subjected to the
Toxic Characteristics Listing Process because the dangers they present are
considered self-evident.
Lithology:
Mineralogy, grain size, texture, and other physical properties of granular soil,
sediment, or rock.
Litter:
1. The highly visible portion of solid waste carelessly discarded outside the
regular garbage and trash collection and disposal system. 2. leaves and twigs
fallen from forest trees.
Littoral Zone:
1. That portion of a body of fresh water extending from the shoreline lake ward
to the limit of occupancy of rooted plants. 2. A strip of land along the
shoreline between the high and low water levels.
Local Education Agency (LEA):
In the asbestos program, an educational agency at the local level that exists
primarily to operate schools or to contract for educational services, including
primary and secondary public and private schools. A single, unaffiliated school
can be considered an LEA for AHERA purposes.
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.
Low Density Polyethylene (LOPE):
Plastic material used for both rigid containers and plastic film applications.
Low Emissivity (low-E) Windows:
New window technology that lowers the amount of energy loss through windows by
inhibiting the transmission of radiant heat while still allowing sufficient
light to pass through.
Low NOx Burners:
One of several combustion technologies used to reduce emissions of Nitrogen
Oxides (NOx.)
Low-Level Radioactive Waste (LLRW):
Wastes less hazardous than most of those associated with a nuclear reactor;
generated by hospitals, research laboratories, and certain industries. The
Department of Energy, Nuclear Regulatory Commission, and USEPA share
responsibilities for managing them. (See: high-level radioactive wastes.)
Lower Detection Limit:
The smallest signal above background noise an instrument can reliably detect.
Lower Explosive Limit (LEL):
The concentration of a compound in air below which the mixture will not catch on
fire.
Lowest Acceptable Daily Dose:
The largest quantity of a chemical that will not cause a toxic effect, as
determined by animal studies.
Lowest Achievable Emission Rate:
Under the Clean Air Act, the rate of emissions that reflects (1) the most
stringent emission limitation in the implementation plan of any state for such
source unless the owner or operator demonstrates such limitations are not
achievable; or (2) the most stringent emissions limitation achieved in practice,
whichever is more stringent. A proposed new or modified source may not emit
pollutants in excess of existing new source standards.
Lowest Observed Adverse Effect Level (LOAEL):
The lowest level of a stressor that causes statistically and biologically
significant differences in test samples as compared to other samples subjected
to no stressor.
Glossary: M
Macropores:
Secondary soil features such as root holes or desiccation cracks that can create
significant conduits for movement of NAPL and dissolved contaminants, or
vapor-phase contaminants.
Major Modification:
This term is used to define modifications of major stationary sources of
emissions with respect to Prevention of Significant Deterioration and New Source
Review under the Clean Air Act.
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 with 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 source.
Majors:
Larger publicly owned treatment works (POTWs) with flows equal to at least one
million gallons per day (mgd) or servicing a population equivalent to 10,000
persons; certain other POTWs having significant water quality impacts. (See:
minors.)
Man-Made (Anthropogenic) Beta Particle and Photon Emitters:
All radio nuclides emitting beta particles and/or photons listed in Maximum
Permissible Body Burdens and Maximum Permissible Concentrations of Radonuclides
in Air and Water for Occupational Exposure.
Management Plan:
Under the Asbestos Hazard Emergency Response Act (AHERA), a document that each
Local Education Agency is required to prepare, describing all activities planned
and undertaken by a school to comply with AHERA regulations, including building
inspections to identify asbestos-containing materials, response actions, and
operations and maintenance programs to minimize the risk of exposure.
Manifest:
A one-page form used by haulers transporting waste that lists USEPA
identification numbers, type and quantity of waste, the generator it originated
from, the transporter that shipped it, and the storage or disposal facility to
which it is being shipped. It includes copies for all participants in the
shipping process.
Manifest System:
Tracking of hazardous waste from "cradle-to-grave" (generation through disposal)
with accompanying documents known as manifests.(See: cradle to grave.)
Margin of Safety:
Maximum amount of exposure producing no measurable effect in animals (or studied
humans) divided by the actual amount of human exposure in a population.
Margin of Exposure (MOE):
The ratio of the no-observed adverse-effect-level to the estimated exposure
dose.
Marine Sanitation Device:
Any equipment or process installed on board a vessel to receive, retain, treat,
or discharge sewage.
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,
tidal or non-tidal. (See:
wetlands.)
Material Category:
In the asbestos program, broad classification of materials into thermal
surfacing insulation, surfacing material, and miscellaneous material.
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 circumstances.
Material Type:
Classification of suspect material by its specific use or application; e.g.,
pipe insulation, fireproofing, and floor tile.
Materials Recovery Facility (MRF):
A facility that processes residentially collected mixed recyclables into new
products available for market.
Maximally (or Most) Exposed Individual:
The person with the highest exposure in a given population.
Maximum Acceptable Toxic Concentration:
For a given ecological effects test, the range (or geometric mean) between the
No Observable Adverse Effect Level and the Lowest Observable Adverse Effects
Level.
Maximum Available Control Technology (MACT):
The emission standard for sources of air pollution requiring the maximum
reduction of hazardous emissions, taking cost and feasibility into account.
Under the Clean Air Act Amendments of 1990, the MACT must not be less than the
average emission level achieved by controls on the best performing 12 percent of
existing sources, by category of industrial and utility sources.
Maximum Contaminant Level:
The maximum permissible level of a contaminant in water delivered to any user of
a public system. MCLs are enforceable standards.
Maximum Contaminant Level Goal (MCLG):
Under the Safe Drinking Water Act, a non-enforceable concentration of a drinking
water contaminant, set at the level at which no known or anticipated adverse
effects on human health occur and which allows an adequate safety margin. The
MCLG is usually the starting point for determining the regulated Maximum
Contaminant Level. (See: maximum contaminant level.)
Maximum Exposure Range:
Estimate of exposure or dose level received by an individual in a defined
population that is greater than the 98th percentile dose for all individuals in
that population, but less than the exposure level received by the person
receiving the highest exposure level.
Maximum Tolerated Dose:
The maximum dose that an animal species can tolerate for a major portion of its
lifetime without significant impairment or toxic effect other than
carcinogenicity.
Measure of Effect/ Measurement Endpoint:
A measurable characteristic of ecological entity that can be related to an
assessment endpoint; e.g. a laboratory test for eight species meeting certain
requirements may serve as a measure of effect for an assessment endpoint, such
as survival of fish, aquatic, invertebrate or algal species under acute
exposure.
Measure of Exposure:
A measurable characteristic of a stressor (such as the specific amount of
mercury in a body of water) used to help quantify the exposure of an ecological
entity or individual organism.
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 other
non-thermal, processes.
Media:
Specific environments--air, water, soil--which are the subject of regulatory
concern and activities.
Medical Surveillance:
A periodic comprehensive review of a worker's health status; acceptable elements
of such surveillance program are listed in the Occupational Safety and Health
Administration standards for asbestos.
Medical Waste:
Any solid waste generated in the diagnosis, treatment, or immunization of human
beings or animals, in research pertaining thereto, or in the production or
testing of biologicals, excluding hazardous waste identified or listed under 40
CFR Part 261 or any household waste as defined in 40 CFR Sub-section 261.4
(b)(1).
Medium-size Water System:
A water system that serves 3,300 to 50,000 customers.
Meniscus:
The curved top of a column of liquid in a small tube.
Mercury (Hg):
Heavy metal that can accumulate in the environment and is highly toxic if
breathed or swallowed. (See: heavy metals.)
Mesotrophic:
Reservoirs and lakes which contain moderate quantities of nutrients and are
moderately productive in terms of aquatic animal and plant life.
Metabolites:
Any substances produced by biological processes, such as those from pesticides.
Metalimnion:
The middle layer of a thermally stratified lake or reservoir. In this layer
there is a rapid decrease in temperature with depth. Also called thermocline.
Methane:
A colorless, nonpoisonous, flammable gas created by anaerobic decomposition of
organic compounds. A major component of natural gas used in the home.
Methanol:
An alcohol that can be used as an alternative fuel or as a gasoline additive. It
is less volatile than gasoline; when blended with gasoline it lowers the carbon
monoxide emissions but increases hydrocarbon emissions. Used as pure fuel, its
emissions are less ozone-forming than those from gasoline. Poisonous to humans
and animals if ingested.
Method 18:
An USEPA test method which uses gas chromatographic techniques to measure the
concentration of volatile organic compounds in a gas stream.
Method 24:
An USEPA reference method to determine density, water content and total volatile
content (water and VOC) of coatings.
Method 25:
An USEPA reference method to determine the VOC concentration in a gas stream.
Method Detection Limit (MDL):
See limit of detection.
Methoxychlor:
Pesticide that causes adverse health effects in domestic water supplies and is
toxic to freshwater and marine aquatic life.
Methyl Orange Alkalinity:
A measure of the total alkalinity in a water sample in which the color of methyl
orange reflects the change in level.
Microbial Growth:
The amplification or multiplication of microorganisms such as bacteria, algae,
diatoms, plankton, and fungi.
Microbial Pesticide:
A microorganism that is used to kill a pest, but is of minimum toxicity to
humans.
Microclimate:
1. Localized climate conditions within an urban area or neighborhood. 2. The
climate around a tree or shrub or a stand of trees.
Microenvironmental Method:
A method for sequentially assessing exposure for a series of microenvironments
that can be approximated by constant concentrations of a stressor.
Microenvironments:
Well-defined surroundings such as the home, office, or kitchen that can be
treated as uniform in terms of stressor concentration.
Million-Gallons Per Day (MGD):
A measure of water flow.
Minimization:
A comprehensive program to minimize or eliminate wastes, usually applied to
wastes at their point of origin. (See: waste minimization.)
Mining of an Aquifer:
Withdrawal over a period of time of groundwater that exceeds the rate of
recharge of the aquifer.
Mining Waste:
Residues resulting from the extraction of raw materials from the earth.
Minor Source:
New emissions sources or modifications to existing emissions sources that do not
exceed NAAQS emission levels.
Minors:
Publicly owned treatment works with flows less than 1 million gallons per day.
(See: majors.)
Miscellaneous ACM:
Interior asbestos-containing building material or structural components, members
or fixtures, such as floor and ceiling tiles; does not include surfacing
materials or thermal system insulation.
Miscellaneous Materials:
Interior building materials on structural components, such as floor or ceiling
tiles.
Miscible Liquids:
Two or more liquids that can be mixed and will remain mixed under normal
conditions.
Missed Detection:
The situation that occurs when a test indicates that a tank is "tight" when in
fact it is leaking.
Mist:
Liquid particles measuring 40 to 500 micrometers (pm), are formed by
condensation of vapor. By comparison, fog particles are smaller than 40
micrometers (pm).
Mitigation:
Measures taken to reduce adverse impacts on the environment.
Mixed Funding:
Settlements in which potentially responsible parties and USEPA share the cost of
a response action.
Mixed Glass:
Recovered container glass not sorted into categories (e.g. color, grade).
Mixed Liquor:
A mixture of activated sludge and water containing organic matter undergoing
activated sludge treatment in an aeration tank.
Mixed Metals:
Recovered metals not sorted into categories such as aluminum, tin, or steel cans
or ferrous or non-ferrous metals.
Mixed Municipal Waste:
Solid waste that has not been sorted into specific categories (such as plastic,
glass, yard trimmings, etc.)
Mixed Paper:
Recovered paper not sorted into categories such as old magazines, old
newspapers, old corrugated boxes, etc.
Mixed Plastic:
Recovered plastic unsorted by category.
Mobile Incinerator Systems:
Hazardous waste incinerators that can be transported from one site to another.
Mobile Source:
Any non-stationary source of air pollution such as cars, trucks, motorcycles,
buses, airplanes, and locomotives.
Model Plant:
A hypothetical plant design used for developing economic, environmental, and
energy impact analyses as support for regulations or regulatory guidelines;
first step in exploring the economic impact of a potential NSPS.
Modified Bin Method:
Way of calculating the required heating or cooling for a building based on
determining how much energy the system would use if outdoor temperatures were
within a certain temperature interval and then multiplying the energy use by the
time the temperature interval typically occurs.
Modified Source:
The enlargement of a major stationary pollutant sources is often referred to as
modification, implying that more emissions will occur.
Moisture Content:
1.The amount of water lost from soil upon drying to a constant weight, expressed
as the weight per unit of dry soil or as the volume of water per unit bulk
volume of the soil. For a fully saturated medium, moisture content indicates the
porosity. 2. Water equivalent of snow on the ground; an indicator of snowmelt
flood potential.
Molecule:
The smallest division of a compound that still retains or exhibits all the
properties of the substance.
Molten Salt Reactor:
A thermal treatment unit that rapidly heats waste in a heat-conducting fluid
bath of carbonate salt.
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, plants, and animals.
Monitoring Well:
1. A well used to obtain water quality samples or measure groundwater levels. 2.
A well 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 distribution of
contaminants in the groundwater beneath the site.
Monoclonal Antibodies (Also called MABs and MCAs):
1. Man-made (anthropogenic) clones of a molecule, produced in quantity for
medical or research purposes. 2. 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.
Monomictic:
Lakes and reservoirs which are relatively deep, do not freeze over during
winter, and undergo a single stratification and mixing cycle during the year
(usually in the fall).
Montreal Protocol:
Treaty, signed in 1987, governs stratospheric ozone protection and research, and
the production and use of ozone-depleting substances. It provides for the end of
production of ozone-depleting substances such as CFCS. Under the Protocol,
various research groups continue to assess the ozone layer. The Multilateral
Fund provides resources to developing nations to promote the transition to
ozone-safe technologies.
Moratorium:
During the negotiation process, a period of 60 to 90 days during which USEPA and
potentially responsible parties may reach settlement but no site response
activities can be conducted.
Morbidity:
Rate of disease incidence.
Mortality:
Death rate.
Most Probable Number:
An estimate of microbial density per unit volume of water sample, based on
probability theory.
Muck Soils:
Earth made from decaying plant materials.
Mudballs:
Round material that forms in filters and gradually increases in size when not
removed by backwashing.
Mulch:
A layer of material (wood chips, straw, leaves, etc.) placed around plants to
hold moisture, prevent weed growth, and enrich or sterilize the soil.
Multi-Media Approach:
Joint approach to several environmental media, such as air, water, and land.
Multiple Chemical Sensitivity:
A diagnostic label for people who suffer multi-system illnesses as a result of
contact with, or proximity to, a variety of airborne agents and other
substances.
Multistage Remote Sensing:
A strategy for landscape characterization that involves gathering and analyzing
information at several geographic scales, ranging from generalized levels of
detail at the national level through high levels of detail at the local scale.
Municipal Discharge:
Discharge of effluent from waste water treatment plants which receive waste
water from households, commercial establishments, and industries in the coastal
drainage basin. Combined sewer/separate storm overflows are included in this
category.
Municipal Sewage:
Wastes (mostly liquid) originating from a community; may be composed of domestic
wastewaters and/or industrial discharges.
Municipal Sludge:
Semi-liquid residue remaining from the treatment of municipal water and
wastewater.
Municipal Solid Waste:
Common garbage or trash generated by industries, businesses, institutions, and
homes.
Mutagen/Mutagenicity:
An agent that causes a permanent genetic change in a cell other than that which
occurs during normal growth. Mutagenicity is the capacity of a chemical or
physical agent to cause such permanent changes.
Glossary: N
National Ambient Air Quality Standards (NAAQS):
Standards established by USEPA that apply for outdoor air throughout the
country. (See: criteria pollutants, state implementation plans, emissions
trading.)
National Emissions Standards for Hazardous Air Pollutants (NESHAPS):
Emissions standards set by USEPA for an air pollutant not covered by NAAQS that
may cause an increase in fatalities or in serious, irreversible, or
incapacitating illness. Primary standards are designed to protect human health,
secondary standards to protect public welfare (e.g. building facades,
visibility, crops, and domestic animals).
National Environmental Performance Partnership Agreements:
System that allows states to assume greater responsibility for environmental
programs based on their relative ability to execute them.
National Estuary Program:
A program established under the Clean Water Act Amendments of 1987 to develop
and implement conservation and management plans for protecting estuaries and
restoring and maintaining their chemical, physical, and biological integrity, as
well as controlling point and nonpoint pollution sources.
National Municipal Plan:
A policy created in 1984 by USEPA and the states in 1984 to bring all publicly
owned treatment works (POTWs) into compliance with Clean Water Act requirements.
National Oil and Hazardous Substances Contingency Plan (NOHSCP/NCP):
The federal regulation that guides determination of the sites to be corrected
under both the Superfund program and the program to prevent or control spills
into surface waters or elsewhere.
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 USEPA, a state,
or, where delegated, a tribal government on an Indian reservation.
National Priorities List (NPL):
USEPA's list of the most serious uncontrolled or abandoned hazardous waste sites
identified for possible long-term remedial action under Superfund. The list is
based primarily on the score a site receives from the Hazard Ranking System.
USEPA is required to update the NPL at least once a year. A site must be on the
NPL to receive money from the Trust Fund for remedial action.
National Response Center:
The federal operations center that receives notifications of all releases of oil
and hazardous substances into the environment; 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--an oil spill, a
major chemical release, or a - superfund response action--and provide advice and
technical assistance to the responding agency(ies) before and during a response
action.
National Secondary Drinking Water Regulations:
Commonly referred to as NSDWRs.
Navigable Waters:
Traditionally, waters sufficiently deep and wide for navigation by all, or
specified vessels; such waters in the United States come under federal
jurisdiction and are protected by certain provisions of the Clean Water Act.
Necrosis:
Death of plant or animal cells or tissues. In plants, necrosis can discolor
stems or leaves or kill a plant entirely.
Negotiations (Under Superfund):
After potentially responsible parties are identified for a site, USEPA
coordinates with them to reach a settlement that will result in the PRP paying
for or conducting the cleanup under USEPA supervision. If negotiations fail,
USEPA can order the PRP to conduct the cleanup or USEPA can pay for the cleanup
using Superfund monies and then sue to recover the costs.
Nematocide:
A chemical agent which is destructive to nematodes.
Nephelometric:
Method of measuring turbidity in a water sample by passing light through the
sample and measuring the amount of the light that is deflected.
Neutralization:
Decreasing the acidity or alkalinity of a substance by adding alkaline or acidic
materials, respectively.
New Source:
Any stationary source built or modified after publication of final or proposed
regulations that prescribe a given standard of performance.
New Source Performance Standards (NSPS):
Uniform national USEPA air emission and water effluent standards which limit the
amount of pollution allowed from new sources or from modified existing sources.
New Source Review (NSR):
A Clean Air Act requirement that State Implementation Plans must include a
permit review that applies to the construction and operation of new and modified
stationary sources in nonattainment areas to ensure attainment of national
ambient air quality standards.
Nitrate:
A compound containing nitrogen that can exist in the atmosphere or as a
dissolved gas in water and which can have harmful effects on humans and animals.
Nitrates in water can cause severe illness in infants and domestic animals. A
plant nutrient and inorganic fertilizer, nitrate is found in septic systems,
animal feed lots, agricultural fertilizers, manure, industrial waste waters,
sanitary landfills, and garbage dumps.
Nitric Oxide (NO):
A gas formed by combustion under high temperature and high pressure in an
internal combustion engine; it is converted by sunlight and photochemical
processes in ambient air to nitrogen oxide. NO is a precursor of ground-level
ozone pollution, or smog..
Nitrification:
The process whereby ammonia in wastewater is oxidized to nitrite and then to
nitrate by bacterial or chemical reactions.
Nitrilotriacetic Acid (NTA):
A compound now replacing phosphates in detergents.
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; major
component of photochemical smog.
Nitrogen Oxide (NOx):
The result of photochemical reactions of nitric oxide in ambient air; major
component of photochemical smog. Product of combustion from transportation and
stationary sources and a major contributor to the formation of ozone in the
troposphere and to acid deposition.
Nitrogenous Wastes:
Animal or vegetable residues that contain significant amounts of nitrogen.
Nitrophenols:
Synthetic organopesticides containing carbon, hydrogen, nitrogen, and oxygen.
No Further Remedial Action Planned:
Determination made by USEPA following a preliminary assessment that a site does
not pose a significant risk and so requires no further activity under CERCLA.
No Observable Adverse Effect Level (NOAEL):
An exposure level at which there are no statistically or biologically
significant increases in the frequency or severity of adverse effects between
the exposed population and its appropriate control; some effects may be produced
at this level, but they are not considered as adverse, or as precursors to
adverse effects. In an experiment with several NOAELs, the regulatory focus is
primarily on the highest one, leading to the common usage of the term NOAEL as
the highest exposure without adverse effects.
No-Observed-Effect-Level (NOEL):
Exposure level at which there are no statistically or biological significant
differences in the frequency or severity of any effect in the exposed or control
populations.
Noble Metal:
Chemically inactive metal such as gold; does not corrode easily.
Noise:
Product-level or product-volume changes occurring during a test that are not
related to a leak but may be mistaken for one.
Non-Aqueous Phase Liquid (NAPL):
Contaminants that remain undiluted as the original bulk liquid in the
subsurface, e.g. spilled oil. (See: fee product.)
Non-Attainment Area:
Area that does not meet one or more of the National Ambient Air Quality
Standards for the criteria pollutants designated in the Clean Air Act.
Non-Binding Allocations of Responsibility (NBAR):
A process for USEPA to propose a way for potentially responsible parties to
allocate costs among themselves.
Non-Community Water System:
A public water system that is not a community water system; e.g. the water
supply at a camp site or national park.
Non-Compliance Coal:
Any coal that emits greater than 3.0 pounds of sulfur dioxide per million BTU
when burned. Also known as high-sulfur coal.
Non-Contact Cooling Water:
Water used for cooling which does not come into direct contact with any raw
material, product, byproduct, or waste.
Non-Conventional Pollutant:
Any pollutant not statutorily listed or which is poorly understood by the
scientific community.
Non-Degradation:
An environmental policy which disallows any lowering of naturally occurring
quality regardless of pre-established health standards.
Non-Ferrous Metals:
Nonmagnetic metals such as aluminum, lead, and copper. Products made all or in
part from such metals include containers, packaging, appliances, furniture,
electronic equipment and aluminum foil.
Non-ionizing Electromagnetic Radiation:
1. Radiation that does not change the structure of atoms but does heat tissue
and may cause harmful biological effects. 2. Microwaves, radio waves, and
low-frequency electromagnetic fields from high-voltage transmission lines.
Non-Methane Hydrocarbon (NMHC):
The sum of all hydrocarbon air pollutants except methane; significant precursors
to ozone formation.
Non-Methane Organic Gases (NMOG):
The sum of all organic air pollutants. Excluding methane; they account for
aldehydes, ketones, alcohols, and other pollutants that are not hydrocarbons but
are precursors of ozone.
Non-Point Sources:
Diffuse pollution sources (i.e. without a single point of origin or not
introduced into a receiving stream from a specific outlet). The pollutants are
generally carried off the land by storm water. Common non-point sources are
agriculture, forestry, urban, mining, construction, dams, channels, land
disposal, saltwater intrusion, and city streets.
Non-potable:
Water that is unsafe or unpalatable to drink because it contains pollutants,
contaminants, minerals, or infective agents.
Non-Road Emissions:
Pollutants emitted by combustion engines on farm and construction equipment,
gasoline-powered lawn and garden equipment, and power boats and outboard motors.
Non-Transient Non-Community Water System:
A public water system that regularly serves at least 25 of the same non-resident
persons per day for more than six months per year.
Non-discharging Treatment Plant:
A treatment plant that does not discharge treated wastewater into any stream or
river. Most are pond systems that dispose of the total flow they receive by
means of evaporation or percolation to groundwater, or facilities that dispose
of their effluent by recycling or reuse (e.g. spray irrigation or groundwater
discharge).
Nonfriable Asbestos-Containing Materials:
Any material containing more than one percent asbestos (as determined by
Polarized Light Microscopy) that, when dry, cannot be crumbled, pulverized, or
reduced to powder by hand pressure.
Nonhazardous Industrial Waste:
Industrial process waste in wastewater not considered municipal solid waste or
hazardous waste under RARA.
Notice of Deficiency:
An USEPA request to a facility owner or operator requesting additional
information before a preliminary decision on a permit application can be made.
Notice of Intent to Deny:
Notification by USEPA of its preliminary intent to deny a permit application.
Notice of Intent to Suspend:
Notification sent to a pesticide registrant when USEPA decides to suspend
product sale and distribution because of failure to submit requested data in a
timely and/or acceptable manner, or because of imminent hazard. (See: emergency
suspension.)
Nuclear Reactors and Support Facilities:
Uranium mills, commercial power reactors, fuel reprocessing plants, and uranium
enrichment facilities.
Nuclide:
An atom characterized by the number of protons, neutrons, and energy in the
nucleus.
Nutrient:
Any substance assimilated by living things that promotes growth. The term is
generally applied to nitrogen and phosphorus in wastewater, but is also applied
to other essential and trace elements.
Nutrient Pollution:
Contamination of water resources by excessive inputs of nutrients. In surface
waters, excess algal production is a major concern.
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