Absorption:  The uptake of water or dissolved chemicals by a cell
or an organism. The movement of a chemical into or across a

Acaricide:  The class of pesticides used to kill mites and ticks;
also known as "miticide."

Acceptable Daily Intake (ADI):  The maximum dose of a substance
that is anticipated to be without health risk to humans when
taken daily over the course of a lifetime.  ADIs are set by the

Accommodation:  The automatic adjustment of the eye lens to allow
for seeing at different distances.

Accumulation:  The buildup of a chemical in the body due to
long-term or repeated exposure.

Acetylcholinesterase:  An enzyme present in nerve tissue, muscles
and red blood cells that catalyzes the hydrolysis of
acetylcholine to choline and acetic acid, allowing neural
transmission across synapses to occur; true cholinesterase.

Acetylcholinesterase inhibitor:  A compound or group of compounds
(e.g., organophosphorus compounds) which block the action of the
enzyme acetylcholinesterase, interfering with the transmission of
impulses between nerve cells.

ACGIH:  American Conference of Governmental Industrial
Hygienists; establishes exposure limits for workers.

Acid equivalent (a.e.):  The amount of active ingredient
expressed in terms of the parent acid.

Acidic:  Sour; having a pH of less than 7.

Activation:  In mutagenicity testing, the exposure of the tested
chemical to a source of enzymes, e.g., liver microsomes, which
metabolize the chemical. The metabolic products may exhibit
mutagenic activity where the original chemical did not.

Active transport:  An energy-expending mechanism by which a cell
moves a chemical across a cell membrane from a point of lower
concentration to a point of higher concentration, against the
diffusion gradient.

Active ingredient (a.i.):  An ingredient in a formulated
pesticide product which will prevent, destroy, repel or mitigate
any pest.

Acute:  Single or short-term exposure; used to describe brief
exposures and effects which appear promptly after exposure.

Additive effect:  Combined effect of two or more chemicals equal
to the sum of their individual effects.

Adenoma:  A benign tumor of glandular origin.

Adjuvant:  Substance added to a formulated pesticide product to
act as a wetting or spreading agent, sticker, penetrant, or
emulsifier in order to enhance the physical characteristics of
the product.

Adsorption:  The process by which chemicals are held on a solid
surface, especially soil particles.

Adsorption coefficient (Koc):  A measure of a material's tendency
to adsorb to soil particles.  High Koc values indicate a tendency
for the material to be adsorbed by soil particles rather than
remain dissolved in the soil solution.  Strongly adsorbed
molecules will not leach or move unless the soil particle to
which they are adsorbed moves (as in erosion).  Koc values of
less than 500 indicate little or no adsorption and a potential
for leaching.

              conc. adsorbed/conc. dissolved
       Koc = _________________________________
               % organic carbon in the soil

Aerobic:  A process requiring oxygen or free air; conditions in
which oxygen is present.

Alkaline:  Basic; having a pH of greater than 7.

Ambient:  Environmental or surrounding conditions.

Anaerobic:  A process which does not require oxygen or free air;
conditions in which oxygen is absent.

Antagonism:  The combined action of two or more substances to
produce an effect less than the sum of their individual effects;
the opposite of synergism.

Aquatic invertebrates:  Organisms that do not have a spinal
column and live in water.  Includes insects, crayfish, mites,

Aqueous:  Watery; pertaining to water.

Arthropods:  Organisms such as insects, arachnides (spiders and
mites) and crustaceans which lack backbones (invertebrates).

Assay:  Analysis to determine the presence, absence or quantity
of a particular chemical or effect.

Atrophy:  The wasting away or reduction in the size of a cell,
tissue, or organ(s).

Autopsy:  The examination of a dead body. Most autopsies involve
an examination of the internal organs and some microscopic
examination of tissues.

Avicide: The class of pesticides used to kill birds.

Background level:  Normal environmental concentration of a

Basic:  Alkaline; having a pH of greater than 7.

Benign tumor:  A non-cancerous tumor.

Bias:  An inadequacy in experimental design that leads to results
or conclusions not representative of the population under study.

Bioaccumulation:  The absorption, via breathing, eating, drinking
or active uptake, and concentration of a substance in plants or

Bioassay:  Test which determines the effect of a chemical on a
population of living organisms.

Biocide:  A material that has the capacity to kill all forms of

Bioconcentration:  The accumulation of a chemical in tissues of
an organism (such as fish) to levels that are greater than the
level in the medium (such as water) in which the organism
resides;  Movement of a substance such as a pesticide from the
surrounding environment (abiotic) into living organisms,
especially via passive absorption.

Bioconcentration factor:  A measure of the tendency for a
chemical to accumulate.  The ratio of the concentration of a
substance in a living organism (mg/kg) to the concentration of
that substance in the surounding environment (mg/l for aquatic

               conc. in organism         =     mg/kg
        BCF = _______________________         _______
               conc. in environment             mg/l

Biodegradation:  Decomposition of a substance into more
elementary compounds by the action of microorganisms such as

Biomagnification:  Process by which substances such as pesticides
or heavy metals move up the food chain, becoming more
concentrated with each succeeding step up the chain.

Bone marrow:  The soft tissue contained inside the bone.

Broad spectrum pesticide:  A pesticide which kills a wide range
of pest species, as opposed to a pesticide which kills a single
or limited number of species.

Cancer:  A disease characterized by the rapid and uncontrolled
growth of aberrant cells into malignant tumors.

Carcinogen:  Any substance capable of producing cancer or a
chemical which causes or induces cancer.

Carcinogenicity:  The ability of a substance to produce cancer.

Carcinoma:  A malignant tumor of epithelial origin

Cardiovascular system:  The heart and blood vessels.

Carrier:  Material added to an active ingredient to facilitate
its preparation, storage, shipment, or use.

CAS No.:  Chemical Abstracts Service Registry Number. The CAS No.
is assigned to a specific compound and is used for cross
referencing chemical names which refer to the same compound.

Cataracts: A clouding of the eye that interferes with light
entering the eye.

CAUTION:  see "Signal Word."

Central nervous system (CNS):  Portion of the nervous system
which consists of the brain and spinal cord.

Certified applicator: A person who has been trained and certified
as a pesticide applicator by a state agency which has been
authorized to do so by EPA.

Cholinergic:  resembling acetylcholine, especially in
physiological action.  Cholinergic symptoms include nausea,
vomiting, headache and sweating.

Cholinesterase:  An enzyme of the body necessary for proper nerve
function; also called serum cholinesterase.

Chromosomal aberration:  An irregularity in the number or
constitution of chromosomes which may cause abnormalities in a
developing embryo.

Chromosome:  Rod-like structure in the nucleus of a cell that
forms during mitosis; composed of DNA and protein; chromosomes
contain the genes responsible for heredity.

Chronic:  Occurring over a long period of time, either
continuously or intermittently, used to describe ongoing
exposures and effects that develop only after a long exposure.

Ciliary:  Of or related to cilia; related to the suspension of
the lens of the eye.

Clay:  A soil component consisting of very fine particles (<0.002
mm diameter).  Clay particles provide ample surface area for
adsorption of molecules.  Clay soils provide the most resistance
to leaching.  Soil texture and many other soil characteristics
are determined by the relative amounts of sand, silt, clay and
loam in a soil.  

Cleft palate: A defect existing before, or at birth which results
in a groove or crack in the roof of the mouth.

Clinical studies:  Studies of humans under controlled conditions.

Common names:  Common names for pesticides are established or
accepted by the following organizations:  ANSI - American
National Standards Institute:  BSI - British Standards
Institution:  ISO - International Organization for
Standardization:  WSSA - Weed Science Society of America.  A
common name generally is not accepted for use on EPA registered
labels or in CFR regulations until it has been accepted by ANSI.

Concentration:  The amount of active ingredient or pesticide
equivalent in a quantity of diluent, expressed as lb/gal,
ml/liter, etc.

Concentration factors:  Concentration factors indicate whether or
not a compound is accumulated in the tissue of an organism.  It
is calculated by dividing the concentration of the compound in
the tissue by the concentration ingested in the diet or taken up
from the surrounding medium.

Confounding factors:  Variables other than those being tested
which can affect the incidence or degree of a parameter being

Congenital:  Existing at birth but acquired in the uterus rather
than inherited.

Conjugate:  A compound resulting from the bonding of two other
compounds. Examples include glucoside conjugates formed from
pesticides in plants and glucuronide conjugates formed from
pesticides in animals.

Conjunctivitis: Inflammation of the conjunctiva, the membrane
that lines the inner surface of the eyelids.

Contact dermatitis: Skin swelling due to either initial acute
irritation from short-term contact with a substance, or from
chronic sensitization that develops from long-term skin contact
with an irritating substance.

Contact poison:  A poison which affects the target organisms
through physical contact rather than through ingestion or
inhalation (animals) or translocation (plants).  Compare with
"Stomach Poison."

Control group:  A group of experimental subjects which are not
exposed to a chemical or treatment being investigated so that
they can be compared to experimental groups which are exposed to
the chemical or treatment.

Cornea:  The transparent front portion of the eyeball.

Cost/benefit analysis:  A quantitative evaluation of the costs
which would be incurred versus the overall benefits to society of
a proposed action such as the establishment of an acceptable dose
of a toxic chemical.

Cumulative exposure:  The summation of exposures of an organism
to a chemical over a period of time.

Cytological aberration:  A deviation from normal cell structure
or function.

Cytotoxicity:  The capacity of a material to interfere with cell

DANGER:  see "Signal Word."

Data gap:  Missing information; used in this context to refer to
that data which is required by the U. S. Environmental Protection
Agency for registration of pesticides, herbicides, etc.

Degradation:  A chemical alteration to a pesticide.  Chemical or
biological breakdown of a complex compound into simpler

Demography:  The study of the characteristics of human
populations such as size, growth, density, distribution, and
vital statistics.

Demyelination:  The destruction or removal of the myelin sheath
which is composed of a lipoid substance and envelops certain
nerve fibers.

Dermal:  Of the skin:  through or by the skin.  

Diffusion:  The movement of suspended or dissolved particles from
a more concentrated region to a less concentrated region as a
result of the random movement of individual particles.  Diffusion
tends to distribute particles uniformly throughout the available

Dipterous:  An order of insects that includes flies and

Distribution:  The movement of a chemical from the blood to other

Dominant lethal assay:  A mutagenic bioassay used in assessing
the ability of a chemical to penetrate gonadal tissue and produce
genetic damage. Male animals are treated with a test substance
acutely (single dose) or over the entire period of sperm
production. These males are then mated with females, which after
about the 14th day of pregnancy are sacrificed and examined for
the number of total implantations and viable fetuses.

Dose:  A measure of exposure. Dose is often expressed in
milligrams per kilogram (mg/kg) or parts per million (ppm).

Dose response:  A quantitative relationship between the dose of a
chemical and the degree/severity of an effect caused by the

Dust:  A pesticide formulation which consists of an active
ingredient impregnated on a finely ground carrier such as clay,
talc, or calcium carbonate.

Ecology:  The study of the interrelationships between living
organisms and their environment, both physical and biological.

Ecosystem:  The interacting system of a biological community and
its non-living environment.

Effective dose:  The ED50 is the effective dose for 50 percent of
tested subjects.

Elimination:  The removal of a chemical from the body, primarily
in the urine, feces or exhaled air.

Embryo:  The developing animal during pregnancy, especially
during the early stages.

Embryonic: Pertaining to embryos, young organisms in the early
stages of development.

Emulsifiable Concentrate (EC):  A pesticide formulation
consisting of an active ingredient and an emulsifying agent in an
organic solvent.  The solvent is usually not soluble in water. 
When an EC product is mixed with water prior to application, the
resulting mix is a dispersion of fine, oily particles in water.

Embryotoxicity:  A compound-induced toxic effect on the embryo
during the initial phase of pregnancy.

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.

Endpoint:  A biological effect used as an index of the effect of
a chemical on an organism.

Environmental fate:  The destiny of a chemical after release to
the environment; involves considerations such as transport
through air, soil and water, bioconcentration, degradation, etc.

Enzyme:  A protein, synthesized by a cell, that acts as a
catalyst in a specific chemical reaction.

EPA:  United States Environmental Protection Agency.

Epidemiology:  The study of the incidence and distribution of
disease and/or toxic effects  in a population.

Excretion:  The removal of a chemical from the body in urine,
feces or expired air.

Exposure:  Contact with a chemical. Some common routes of
exposure are dermal (skin), oral (by mouth) and inhalation

Extrapolation:  Estimation of unknown values by extending or
projecting from known values.

FAO:  Food and Agriculture Organization of the United Nations.

FDA monitoring:  The collection and analysis for pesticide
residues carried out by the Food and Drug Administration. The
primary components of the monitoring are the Total Diet Studies,
which entail examining ready-to-eat foods, and the Compliance
Programs, special assignments, and surveys on both domestic and
imported foods, which include both surveillance and compliance
examinations of fresh fruits and vegetables, grains, milk and
dairy products, fish, and a variety of processed products and

Fetal resorption:  Following the in utero death of a fetus, for
whatever reason, the fetal tissues will undergo either partial or
complete dissolution and the resulting products will be absorbed
by the maternal tissue.

Fetotoxicity:  A compound-induced toxic effect on the fetus
during the latter phase of pregnancy.

Fetus:  Unborn or unhatched vertebrate, especially one that has
attained the basic structure of its kind; a developing human,
usually from three months after conception until birth.

Flash point:  The lowest temperature at which a liquid gives off
ignitable vapors.

Food chain:  A sequence of species in which each species serves
as a food source for  the next species.  Food chains usually
begin with species which consume detritus or plant material
(herbivores) and proceed to larger and larger carnivores.  Ex:
grasshopper eaten by snake eaten by owl.

Formulated pesticide product:  A mixture of one or more
pesticidal active ingredients with inert ingredients such as
carriers, diluents, etc.;  a packaged, ready-for-sale pesticide
product.  Types of formulations include liquids, dusts,
emulsifiable concentrates, ultra-low volume and granular

Fungicide:  A class of pesticides used to kill fungi, primarily
those which cause diseases of plants.

Gastrointestinal tract (GI tract):  The entire digestive canal
from mouth to anus.

Gavage:  Forced feeding by stomach tube.

General Use Pesticide (GUP):  A pesticide which may be purchased
and used by individuals without any special certification or
licensing.  Pesticides classified by the EPA as GUP have not been
shown to pose undue hazards to applicators, the general public or
to the environment.  Compare with "Restricted Use Pesticide."

Genotoxicity:  Any toxic modification or alteration of the
structure or function of genetic material.

Gestation:  The duration of pregnancy. In the human, gestation is
normally nine months.

Goiter:  Enlargement of the thyroid gland.

Goitrogen:  A material capable of causing goiter.

Granular formulation:  a dry, ready-to-use pesticide product
which consists  of an active ingredient mixed with or impregnated
into a carrier such as coarse particles of clay.

Groundwater:  Water located in saturated zones below the soil
surface.  Many wells and springs are fed by groundwater.

GRGL:  Groundwater residue guidance level.

GUP:  see "General Use Pesticide."

HA:  see "Health Advisory."

Half-life:  The time required for half of the residue to lose its
analytical identity whether through dissipation, decomposition,
metabolic alteration or other factors. The half-life concept may
be applied to residues in crops, soil, water, animals or specific

Hazard:  The potential that the use of a product would result in
an adverse effect on man or the environment in a given situation.

Health Advisory (HA or LHA):  A non-enforceable guideline set by
EPA and used to evaluate the health significance of a contaminant
in drinking water when no Maximum Contaminant Level has been set
by EPA for that contaminant.  HAs are set at a concentration of
contamination that can be consumed daily in drinking water over
the course of a lifetime with no adverse health effects.  HAs may
or may not include consideration of cancer risks posed by the
contaminant.  Also known as "Lifetime Health Advisory."

Hematopoiesis:  The production of blood and blood cells;

Hectare:  A measure of area in the metric system approximately
equal to 2.47 acres.

Hemotoxicity:  A toxic effect on blood components or properties
such as changes in hemoglobin, pH, electrolytes, or protein of
the plasma.

Henry's Law Constant:  A parameter used in evaluating air
exposure pathways. Values for Henry's Law Constant (H) were
calculated using the following equation and the values previously
recorded for solubility, vapor pressure, and molecular weight:

                        Vapor Pressure (atm) x Mole Wt (g/mole)
   H(atm-meter3/mole) =______________________________________
                          Water Solubility (g/cubic meter).

Hepatoma:  A malignant tumor occurring in the liver.

Herbicide:  A pesticide used for killing or inhibiting plant
growth. A weed or grass killer.

Histology:  The study of the structure of cells and tissues;
usually involves microscopic examination of tissue slices.

Homeostasis:  Maintenance of a constant internal environment in
an organism.

Hormone:  A chemical substance secreted in one part of an
organism and transported to another part of that organism where
it has a specific effect.

Host-mediated assay:  This assay evaluates the genotoxicity of a
substance to microbial cells introduced (e.g., by intravenous
injection) into a host animal. The host animal receives the test
compound orally, and therefore acts as a source of chemical
metabolism, distribution and excretion of the test compound.

Human equivalent dose:  A dose which, when administered to
humans, produces an effect equal to that produced by a dose in

Hydrology:  The study of the properties, distribution, behavior
and effects of water on the earth's surface, in the soil and
underlying rocks and in the atmosphere.

Hydrolysis:  The chemical process of decomposition involving the
splitting of a molecule and the addition of a water molecule.

Hydrolyze:  To subject to hydrolysis; to undergo hydrolysis.

Hypoesthia:  A decreased sense of touch.

Hypoxia:  A deficiency of oxygen.

Inert ingredient:  An ingredient in a formulated pesticide
product which will not prevent, destroy, repel or mitigate any
pest and which is intentionally included in the product. 
Includes carriers and materials which dilute the active

Inhalation:  Drawing of air into the lungs.

Insecticide:  A class of pesticides used to kill insects.

Intake:  Amount of material inhaled, ingested, or absorbed
dermally during a specified period of time.

Intraperitoneal (I.P.):  The introduction (e.g., by injection) of
a substance into the peritoneal cavity which is comprised of the
abdominal and pelvic spaces and contains the large internal

Intubation:  The insertion of a tube; for example, the passing of
a tube from the mouth through the esophagus and into the stomach
as a means of facilitating the accurate, oral dosing of a test
animal with a substance.

In vitro studies:  Studies of chemical effects conducted in
tissues, cells or subcellular extracts from an organism (i.e.,
not in the living organism).

In vivo studies:  Studies of chemical effects conducted in intact
living organisms.

Invertebrates:  Organisms which lack a spinal column.

Irreversible:  Permanent, incurable.

Iris:  The colored circular portion of the eyeball.

Isomers:  Two or more chemical compounds having the same
structure but different properties.

Kd:  Soil-water adsorption coefficient, calculated by using
measurements of pesticide distribution between soil and water.

Koc:  see "Adsorption coefficient."

Kow:  see "Octanol-water partition coefficient."

Laboratory Information Bulletin (LIB):  An internal publication
of FDA, for the dissemination of information concerning
analytical methodology among FDA laboratories.

Larvae:  The immature form and stage of development of some
insect species that go through extreme changes in the
developmental process of becoming an adult.

Larvicide:  A class of pesticides used to kill insect larvae. 
Usually refers to chemicals used for controlling mosquito larvae,
but also to chemicals for controlling caterpillars on crops.

Latency:  Time from the first exposure to a chemical until the
appearance of a toxic effect.

LC:  Lethal Concentration.

LC50:  The concentration of toxicant necessary to kill 50 percent
of the organisms being tested. It is usually expressed in parts
per million (ppm).

LC50/96 hr:  Lethal concentration in a 96-hour test.

LClo:  Lethal concentration, low.  The lowest concentration to
cause death in test animals.

LD:  Lethal dose.

LD50:  The amount of a chemical that is lethal to one-half (50%)
of the experimental animals exposed to it.  LD50s are usually
expressed as the weight of the chemical per unit of body weight
(mg/kg). It may be fed (oral LD50), applied to the skin (dermal
LD50), or administered in the form of vapors (inhalation LD50).

LDlo:  Lethal dose, low.  The lowest dose which causes death in
test animals.

Leaching:  The movement of a pesticide chemical or another
substance downward through soil as a result of water movement,
potentially causing contamination of groundwater resources.

LEL:  Lowest Effect Level. In a series of dose levels tested, it
is the lowest level at which an effect is observed in the species

Lethality:  Death

LHA:  see "Health Advisory."

Lifetime Health Advisory: see "Health Advisory."

LOAEL:  Lowest-Observed-Adverse-Effect-Level; the lowest dose in
an experiment which produced an observable adverse effect.

Loam:  A soil of intermediate texture containing moderate amounts
of sand, silt and clay.  Soil texture and many other soil
characteristics are determined by the relative amounts of sand,
silt, clay and loam in a soil.  

LOEL:  Lowest-Observed-Effect-Level; the lowest dose in an
experiment which produced an observable effect.

Malignant tumor:  A cancerous tumor.

Mammals:  The class of organisms that have backbones
(vertebrates); includes all animals that have hair and suckle
their young.

MATC:  Maximum Acceptable Tolerance Concentration.

MCL:  Maximum Contaminant Level.  The highest amount of a
contaminant allowed by EPA in water supplied by a municipal water
system; also referred to as "drinking water standard."

Metabolic enzymes:  Protein-based substances that promote change
in bodily cells.

Metabolism:  The process of chemical change by which energy is
provided in living cells.

Metabolite:  Any product of metabolism, especially a transformed

mg/kg:  Milligrams per kilogram.

mg/kg/day:  Milligrams per kilogram per day.

mg/l:  Milligrams per liter.

micrograms/liter:  Usual unit of measurement for contaminants of
water; ug/l; equivalent to parts per billion (ppb).

mg/m3:  Milligrams of material per cubic meter (of air or water).

micrograms/m3:  Microgram per cubic meter (ug/m3) (of air or

Miosis:  Decreased pupil (eye) size.

MLD:  Minimum Lethal Dose; the smallest of several doses which
kills one of a group of test animals.

mm Hg:  Millimeters of mercury.

Modeling:  Use of mathematical equations to simulate and predict
real events and processes.

Molluscicide:  A class of pesticides used to kill mollusks,
primarily snails and slugs.

Monitoring:  Measuring concentrations of substances in
environmental media or in human or other biological tissues.

MOS:  Margin of Safety.  Refer to "Uncertainty Factor."

MPI:  Maximum Permissible Intake. A limit established by EPA,
usually expressed as mg/day for a 60 kg person, which is used to
determine the level of pesticide residues permitted on crops for
human consumption.

MTD:  Maximum Tolerated Dose; the highest dose of a chemical that
does not alter the life span or severely affect the health of an

Mucous membranes:  Any tissue lining body cavities and canals
which come in contact with the air, and kept moist by secretions
of various types of glands (e.g., inside the mouth).

Musculoskeletal system:  Composed of, or pertaining to the
muscles and the skeleton.

Mutagen:  An agent that causes a permanent genetic change in a
cell other than that which occurs during normal genetic

Mutagenicity:  The ability of a substance to produce a detectable
and heritable change in genetic material which may be transmitted
to the progeny of affected individuals through germ cells
(germinal mutation) or from one cell generation to another within
the individual (somatic mutation).

Mutation:  An alteration in genetic structure which is passed
from one generation to the next.

Mydriasis:  An excessive dilation of the pupil of the eye.

Necropsy:  The examination of a dead body, autopsy. The term
necropsy is often used with respect to examination of animals
other than humans.

Necrosis:  Death of cells or tissue.

NEL:  The No-Effect-Level of a pollutant is the concentration at
or below which there will be no defined effect, either
deleterious or beneficial, on a member of a population exposed to
the pollutant in question.

Nervous system:  Includes the brain and all the nerves.

Neural tube:  A hollow tube in vertebrate embryos which changes
and eventually forms the brain and spinal cord.

Neurotoxicity:  The ability of a substance to destroy nerve
tissues or affect behavior.

Neurotoxin:  Any substance that is capable of destroying or
adversely affecting nerve tissue.

NIOSH:  National Institute of Occupational Safety and Health; a
branch of the U.S. Department of Health and Human Services and
the U.S. Department of Labor. Responsible for setting limits to
exposure which workers should be allowed to receive in their

NOAEL:  No-Observed-Adverse-Effect Level; the highest dose in an
experiment which did not produce an observable adverse effect.

NOEL:  The dosage or exposure level at which no toxicologically
significant adverse effect(s) can be detected. The NOEL has been
used interchangeably with the NEL (no effect level). However,
there is a distinction which is based on the interpretation of
the occurrence of an effect. An NEL denotes that at a particular
dose, there was absolutely no effect. In reality, an effect may
have occurred but went undetected for a variety of reasons. Thus,
the more accepted terminology is the NOEL, which indicates that
while an effect was not observed under a particular set of test
conditions, it does not preclude the possibility that some effect
may have occurred.

Nonvolatile:  Will not vaporize or become a gas.

Nonsystemic:  Not capable of affecting the entire system; limited
to particular areas of a plant or animal.

Nontarget vegetation:  Vegetation which is not expected or not
planned to be affected by an herbicide application.

Nontarget species:  Any plant, animal, or pest which is not
intended to be treated with a pesticide application.

Octanol-water partition coefficient (Kow):  A measurement of how
a chemical is distributed at equilibrium between octanol and
water. It is an important parameter and is used often in the
assessment of environmental fate and transport for organic
chemicals. Additionally, Kow is a key variable used in the
estimation of other properties.

Ocular:  Of or relating to the eye muscles.

Oncogen:  Any substance capable of inducing tumors; a carcinogen.

Oncogenicity:  The ability of a substance to produce either
benign or malignant tumors.

OP:  Organophosphate Pesticide.

Oral:  Of the mouth; through or by the mouth.

Organic carbon partition coefficient (Koc):  A measure of the
tendency for organics to be adsorbed by soil and sediment and is
expressed as:  

              mg chemical adsorbed/kg organic carbon
     Koc =  __________________________________________
              mg chemical dissolved/liter of solution

     The Koc is chemical specific and is largely independent of
soil properties.

Organic Matter (OM):  Soil particles created by the decomposition
of plant tissues.  Soil OM has a high adsorptive capacity (higher
than clay) and offers resistance to leaching of soil water and
dissolved molecules.

Organogenesis:  The time period during embryonic development in
which all major organs and organ systems are formed. During this
period, the embryo is most susceptible to factors interfering
with development.

OSHA:  Occupational Safety and Health Administration, a branch of
the U.S. Department of Labor.

Provisional Acceptable Daily Intake (PADI):  The maximum dose of
a substance that is anticipated to be without health risk to
humans when taken daily over the course of a lifetime.  PADIs are
set by the EPA.

Pathogen:  Any disease-causing agent, usually applied to living

Pathogenic:  Causing or capable of disease.

PEL:  Permissible Exposure Level;  OSHA air standard.

Pesticide:  EPA defines a pesticide as, "... any substance or
mixture of substances intended for preventing, destroying,
repelling, or mitigating any pest, and any substance or mixture
of substances intended for use as a plant regulator, defoliant or
dessicant."  The following are a list of pesticides as classified
by their target species: 

     Acaricide             mites, ticks
     algaecide             algae
     attractant            insects, birds, other vertebrates
     avicide               birds
     bactericide           bacteria
     defoliant             unwanted plant leaves
     desiccant             unwanted plant tops
     fungicide             fungi
     growth regulator      insect and plant growth
     herbicide             weeds
     insecticide           insects
     miticide              mites
     molluscicide          snails, slugs
     nematicide            nematodes
     piscicide             fish
     predacide             vertebrates
     repellents            insects, birds, other vertebrates
     rodenticide           rodents
     silvicide             trees and woody vegetation
     slimicide             slime molds
     sterilants            insects, vertebrates

pH:  Hydrogen ion concentration; used to express the degree of
acidity or alkalinity of a material.

Pharmacokinetics:  The dynamic behavior of chemicals inside
biological systems; includes the processes of uptake,
distribution, metabolism and excretion.

Phototoxicity:  Toxicity resulting from sequential exposure to a
photosensitizing agent and sunlight.

Physiological:  Having to do with the mechanics of body function.

Polymer:  The resulting form of many small molecules joined
together; a mixture of compounds formed by a specific molecular
process called polymerization.

Potency:  A measure of the relative strength of a chemical.

Potentiation:  The ability of a substance to increase the toxic
effect(s) of another compound.

ppb:  Parts per billion; a measure of concentration.  May
represent the concentration of a residue in soil, water or whole
animals.  For example, one ppb is equivalent to one second in 32

ppm:  Parts per million; a measure of concentration.  May
represent the concentration of a residue in soil, water or whole
animals.  For example, one ppm is equivalent to one minute in 2

Pupil:  The opening in the colored portion (iris) of the eye,
through which light passes.

Qualitative:  Descriptive of size, magnitude or degree. 

Rate:  The amount of active ingredient or acid equivalent applied
per unit area or other treatment unit.

Receptor (1) In biochemistry: a specialized molecule in a cell
that binds a specific chemical with high specificity and high
affinity; (2) In exposure assessment: an organism that receives,
may receive, or has received environmental exposure to a

Reentry interval:  The period of time designated by Federal law
between the application of certain hazardous pesticides to crops,
and the entrance of workers into the fields of crops without
protective clothing.

Registration standard:  A document produced by the EPA, which
details the various conditions which chemical registrants must
meet in order to reregister pesticide products containing active
ingredients. Through its Registration Standards program, EPA is
reexamining, by current scientific standards, the health and
environmental safety of approximately 600 active ingredients
contained in some 45,000 currently registered products.

Renal:  Pertaining to the kidney.

Reproductive effects:  Changes which may occur during the
reproductive process including mutagenesis, teratogenesis,
diminished fertility, death, growth retardation, functional
disorders, and prematurity or death of the offspring.

Reservoir:  A tissue in an organism or a place in the environment
where a chemical accumulates, from which it may be released at a
later time.

Residue:  That quantity of pesticide, its degradation products,
and/or its metabolites remaining on or in the soil, plant parts,
animal tissues, whole organisms, and surfaces.

Resorption of fetuses:  The disappearance of part, or all, of a
fetus caused by biochemical reactions that may involve
dissolution, absorption and/or other actions.

Respiratory system/tract:  All the passages through which air is
taken in and out of the body with breathing, including the nose,
trachea, larynx, and lungs, where an exchange of oxygen and
carbon dioxide takes place.

Restricted Use Pesticide (RUP):  A designation given to a
pesticide by the EPA which restricts purchase and use of that
pesticide to certified applicators.  The designation is given to
pesticides which pose a potential hazard to applicators, the
general public or to the environment or may be highly toxic.

RfD:  Reference dose.

Risk assessment:  A qualitative or quantitative evaluation of the
environmental and/or health risk resulting from exposure to a
chemical or physical agent (pollutant); combines exposure
assessment results with toxicity assessment results to estimate

Risk:  The potential for realization of unwanted negative
consequences or events.

Rodenticide:  A class of pesticides which kills rodents,
especially rats and mice.

RRfd:  Risk reference dose.

RUP:  see "Restricted Use Pesticide."

Sand:  A soil component consisting of coarse particles (0.05 to
2.0 mm diameter).  Sand particles provide relatively little
surface area for adsorption of molecules.  Soil water and
dissolved materials move/leach easily through sandy soils.  Soil
texture and many other soil characteristics are determined by the
relative amounts of sand, silt, clay and loam in a soil.  

Scrotal:  Refers to the external pouch that contains the testes
in most mammals.

Selective herbicide:  One that kills specific undesirable plants,
sparing other desirable plants; this is done through different
types of toxic action or by the manner in which the material is
used (its formulation, dosage, timing, placement, etc.).

Sensitization:  The development of a hypersensitive or allergic
reaction upon reexposure to a substance. The reaction may be
immediate or delayed and may be of short-term or chronic

Signal word:  One of three words which must appear in large, bold
letters on a pesticide label.  Signal words usually indicate the
level of acute toxicity posed by the pesticide product.

     Signal Word           Toxicity
     ___________           ________

     DANGER                highly toxic
     WARNING               moderately toxic
     CAUTION               slightly toxic or relatively non-toxic

Silt:  A soil component consisting of moderately sized particles
(0.002 to 0.05 mm diameter).  Silt particles provide a moderate
amount of surface area for adsorption of molecules, providing
some resistance to leaching of charged molecules.  Soil texture
and many other soil characteristics are determined by the
relative amounts of sand, silt, clay and loam in a soil.  

Sink:  A place in the environment where a compound or material

SNARL:  Suggested No Adverse Response Level.

Soil mobility:  Movement of a compound through soil from the
treated area by leaching, volatilization, adsorption and
desorption, or dispersal by water. Leaching is of particular
concern because of the potential for contamination of

Solubility:  The concentration of a substance that dissolves in a
given solvent. HIGH SOLUBILITY: readily dissolves. LOW
SOLUBILITY: does not dissolve very well.

Soil organic matter:  see "Organic Matter."

Solvent solubility:  Concentration of a material that dissolves
in a given solvent.

Sorption:  A surface phenomenon which may be either absorption or
adsorption, or a combination of the two; often used when the
specific mechanism is not known.

Special review:  An intensive analysis of all the data on a
chemical, including its risks and benefits. The initiation of a
special review process is an announcement of EPA's concern about
the safety of a pesticide's use. Existing pesticides suspected of
posing unreasonable risks to human health, nontarget organisms or
the environment are referred to EPA for special review. This
process may or may not lead to the cancellation of a material.

Spleen:  An organ near the stomach or intestines of most
vertebrates; the site of final destruction of blood cells, blood
storage, and production of lymphocytes.

Statistically significant:  Probably caused by something other
than mere chance.

STEL:  Short-Term Exposure Limit. The maximum allowable
concentration, or ceiling, not to be exceeded at any time during
a 15-minute exposure period up to four times per day.  The level
to which persons may be exposed continuously for 15 minutes
without adverse effects.

Sterility:  Total inability to reproduce.

Stomach poison:  A pesticide which must be eaten in order to kill
or poison an organism.  Compare with "Contact poison." 

Subchronic:  Intermediate between acute and chronic toxicities;
subchronic toxicity studies involve repeated daily exposures of
animals to a chemical for part (not exceeding 10%) of a lifespan.
In rodents, this period extends up to 90 days of exposure.

Subcutaneous:  Under the skin.

Surface water:  Water at the soil surface in open bodies such as
streams, rivers, ponds, lakes and oceans.

Susceptibility:  Capacity to be adversely affected by pesticide

Synergism:  An interaction of two or more chemicals that results
in an effect that is greater than the sum of their effects taken

Systemic:  Affecting the body generally; distributed throughout
the body.

Systemic insecticide:  Capable of being absorbed by plants into
the plant sap, or by animals into the blood stream, without undue
harm to the plant or animal; capable of poisoning insects feeding
on the plant juice or animal blood. For example, a systemic
insecticide can be applied to the soil, enter the roots of the
plant, travel to the leaves, and kill insects feeding on the

Systemic toxicity:  Poisoning of the whole system or organism,
rather than poisoning which affects, for example, a single organ.

T 1/2:  see "Half-life."

Target:  The target species is the organism which the pesticide
is intended to control. Conversely, the non-target species are
those which because they are either beneficial or harmless, are
not to be killed by the pesticide.

TD:  Toxic dose; the dose of a chemical that produces signs of

TDlo:  The lowest dose which produces signs of toxicity.

Teratogen:  Any substance capable of producing structural
abnormalities of prenatal origin, present at birth or manifested
shortly thereafter.

Teratogenic:   The ability to produce birth defects.  A
teratogenic agent has the ability to induce or increase the
incidence of congenital malformations, i.e., permanent structural
or functional deviations arising during embryogenesis.

Teratogenicity:  The ability of a substance to produce
irreversible birth defects or anatomical or functional disorders
as a result of an effect on the developing embryo or fetus.

Testicular atrophy:  The acquired local reduction in the size of
testicles caused by disease or physiological imbalance.

Testicular:  Referring to the testes, a pair of male reproductive

Theoretical Maximum Residue Contribution (TMRC):  The amount of a
substance that would be present in a 1.5 kg "average" daily diet
if all commodities with established tolerances bore residues at
the tolerance level. The percentages of various commodities in
the "average" diet are those used by EPA and are based on the
"1965-66 Household Food Consumption Survey" conducted by USDA.

Threshold:  The lowest dose of a chemical at which a specified
measurable effect is observed and below which it is not observed.

Thymus:  An immune system gland located at the base of the neck
in young vertebrates; it tends to disappear or become
nonfunctional in adults.

Thyroid carcinoma:  Malignant tumor of the thyroid gland, an
endocrine gland which lies in front of the trachea.

Thyroid gland:  An endocrine gland which lies in front of the
trachea, or wind pipe.

Tissue:  A group of similar cells.

TLm TL50:  Median tolerance limit; for example, the concentration
of chemical in water necessary to kill 50 percent of the test
aquatic organisms during a specific exposure period. The TLm is
usually expressed as parts per million parts of water for 24, 48,
72, or 96 hours of exposure.

TLV:  Threshold Limit Value.  The highest allowable air
concentration of a chemical in which workers may work for many
years (8 hours a day, 40 hours per week) without negative health
effects. Expressed as milligrams (mg) per cubic meter of air
(mg/m3).  The level to which persons may be exposed for an 8-hour
workday without adverse effects.

TLV-TWA:  Threshold Limit Value-Time Weighted Average. The
time-weighted average concentration for a normal 8-hour workday
and a 40-hour work week, to which nearly all workers may be
repeatedly exposed without adverse effect.

Tolerance:  (1) A legal limit, established by EPA, for the
maximum amount of a pesticide residue which may be present in or
on a food. Pesticide tolerances on raw agricultural commodities
are listed in Part 180, CFR 40; tolerances on processed foods are
listed in Part 193, CFR 21; and tolerances on processed animal
feeds are listed in Part 561, CFR 21. Temporary tolerances, which
cover residues resulting from an experimental use, generally
expire after one year.  (2) Capacity to withstand pesticide
treatment without adverse effect on normal growth and function.

Toxic:  Harmful; poisonous.

Toxicity:  (l) The capacity or property of a substance to cause
adverse effects. (2) The specific quantity of a substance which
may be expected, under specific conditions, to do damage to a
specific living organism.

Transformation:  Acquisition by a cell of the property of
uncontrolled growth.

Translocation:  Transport of a substance through a plant from the
site of absorption to other parts of the plant.

Tubules:  Small tubes which serve to transport bodily substances.

Tumor:  An abnormal mass of cells produced by unregulated
overgrowth of cells, and which has no physiologic function. 
Tumors may be benign or malignant.

TWA:  The Time-Weighted Average concentration is the average
exposure concentration based on the duration of exposure to
airborne concentration as it varies during an 8-hour workday.

ug/l:  see "micrograms per liter."

Ultra-Low Volume (ULV):  A liquid pesticide product which is
applied undiluted at a rate of one-half gallon per acre or less.

Uncertainty factor:  A number (equal to or greater than one) used
to divide NOAEL or LOAEL values derived from measurements in
animals or small groups of humans, in order to estimate a NOAEL
value for the whole human population; also called

Vapor pressure:  A relative measure of the volatility of a
chemical in its pure state. The pressure exerted by a gas that is
in equilibrium with its solid or liquid form.

Volatile:  Capable of vaporizing or evaporating readily.

VSD:  Virtually Safe Dose.

WARNING:  see "Signal Word."

Water solubility:  The maximum concentration of a chemical that
dissolves in pure water at a specific temperature and pH.

WHO:  World Health Organization.

     This PIP is part of the EXTOXNET Pesticide Information
Notebook.  For more information, contact the Pesticide Management
Education Program, Cornell University, 5123 Comstock Hall,
Ithaca, N.Y.  14853-0901.

DISCLAIMER:  The information in this profile does not in any way
replace or supersede the information on the pesticide product
label/ing or other regulatory requirements.  Please refer to the
pesticide product label/ing.