absorption.
Entry of a chemical into the body through a surface such
as the skin, digestive tract, or respiratory tract.
acute
toxicity. Adverse effects of a chemical on an
organism after brief exposure to a relatively large
amount of the chemical. Often, acute effects occur a
few minutes or hours after exposure begins. [compare to
chronic toxicity]
ataxia.
Inability to produce coordinated movements or locomotion
due to neurotoxicity effects or neurological disorder.
behavioral
toxicology. Study of the disruptive effects of
chemicals on the behavior of organisms.
bioassay.
Strict definition: Use of a living organism to
estimate the amount of a chemical in a test sample. In
toxicology, this is done by comparing the toxicity effects
produced by a test sample, which contains an unknown amount
of a chemical, to the toxicity effects produced by known
amounts of the chemical. Loose definition: The
use of an organism to investigate or test for toxicity
effects of chemicals.
chronic
toxicity. Adverse effects of a chemical on an
organism as a result of long-term exposure to a relatively
small amount of the chemical. Often, chronic effects
become evident only many days or weeks of repeated or
continuous exposure. [compare to acute toxicity]
contaminant.
A chemical that taints or corrupts soil, water, food,
or air, thus making it impure. [compare to toxicant
and toxin and pesticide.
control
group. A group of organisms that has not been
exposed to the test chemical but which has, in every other
way, been subjected to conditions and procedures that
are identical to those in groups exposed to the test chemical.
contact
exposure. Exposure of an organism to a chemical
by direct contact with a surface of the body, such as
skin.
dose.
The total amount of a chemical given to an organism at
one specific time. [compare to dosage]
dosage.
The rate of administration of a chemical or drug to an
organism. A stated dosage includes the dose, dose frequency,
and total period of time that a chemical is administered
to the organism. [compare to dose].
dose-response
relationship. A quantitative relationship between
the amount of chemical given to (or taken in) by organisms
in a group and the measured effect of the chemical in
the organisms, as determined by some type of toxicity
test. In a dose-response graph, the amount of chemical
is shown on the x-axis.
EC50.
In a dose-response relationship showing sublethal effects,
the EC50 is the concentration that produces a level of
effect = 50% of the maximum effect. For example, the
EC50 may be the concentration that causes a particular
behavioral effect in 50% of the organisms that are tested.
[compare to LC50]
effect.
Any observable or measurable biological response of an
organism to chemical exposure. The measured effect
in a toxicity test may be lethality -- that is, death
caused by chemical exposure -- or the measured effect
may be sublethal, such as a change in an organism’s
behavior, physiology, and/or biochemistry.
environmental
toxicology. A subdivision of toxicology that
deals with the presence, movement, chemical fate, and
biological effects of chemical contaminants within air,
land, or water environments, especially in relation to
individual organisms, populations of organisms, food chains,
or habitats.
exposure.
Contact of an organism with a chemical. [see chronic
toxicity and acute toxicity]
hazard.
A danger or threat that a chemical poses in terms of some
toxicity effect(s) [compare to risk]
LC50.
In a dose-response relationship, the LC50 is the concentration
of chemical that is expected to produce death in 50% of
the organisms that are exposed to that concentration.
[compare to EC50]
lethality.
Death of an organism caused by chemical effects.
lipid
soluble/lipophilic. Refers to chemicals that
tend to be soluble in lipids but not water. Lipophilic
substances tend to easily cross cell membranes and enter
the body. [compare to hydrophilic]
mode
of action. Refers to the biological/biochemical
mechanism (or mechanisms) by which a toxicant is known
to (or is believed to) exert its effects on an organism.
mortality.
The frequency of deaths in a group of organisms exposed
to a chemical. [compare to moribund]
moribund.
Describing a state in which an organism is beginning to
die or is near death. [Compare to mortality]
MODS.
Material Safety Data Sheet. [Source for MODS: http://hazard.com/msds/
]
neurotoxicology.
Study of the adverse effects of chemicals on the structure
or function of the nervous system; neurotoxicity effects
often cause behavioral effects. [see behavioral toxicology]
neurotransmitter.
A chemical (such as acetylcholine) that is released by
a nerve cell at a chemically transmitting synapse.
no
observed effect level (NOEL). In a dose-response
relationship, the NOEL is the highest concentration of
a chemical that causes no observable effect in a group
of organisms. [compare to threshold concentration/dose]
non-target
organism. An organism that is exposed to, but
is not the intended target for, an applied pesticide.
paralysis.
Inability to move the body or body parts due to effects
of disease or toxicity.
parts
per million (ppm). A unit of chemical concentration.
The concentration of a chemical is 1 ppm if one weight
unit of chemical (for example, 1 milligram) is dissolved
in one million weight units of water (1,000,000 milligrams
of water = 1 liter). Very low concentrations of chemicals
may be expressed in parts per billion or high concentrations
in parts per thousand.
pesticide.
A chemical used to kill organisms that are considered
pests. [see non-target organism]
poison.
Synonym = toxicant. Any chemical that causes harmful
biological effects.
recovery.
The disappearance of toxicity effects in an organism and
return to normal function and behavior. If this occurs,
it often occurs at some point in time after sublethal
exposure to a chemical has ended.
risk.
The probability that adverse effects will occur if an
organism is exposed to a chemical under a specific conditions.
serial
dilution. Creation of a series of separate solutions
with concentrations that differ in a regular, step-wise
fashion, such as a series of concentrations that decrease
by a factor of five: 50, 10, 2, 0.4 ppm. Serial dilutions
may be used for both range-finding and final stages of
toxicity testing.
solvent.
A liquid that is capable of dissolving other chemicals.
sublethal
concentration. A concentration of chemical that
does not kill an organism.
sublethal
effect. A biological effect caused by chemical
exposure at a concentration below that which causes death.
threshold
concentration/dose. In reference to a dose-response
relationship, the threshold dose/threshold concentration
is the minimum amount of a chemical that just causes an
observable effect in a group of organisms. [compare to
no observed effect level]
toxic.
Synonym = harmful or poisonous.
toxicant.
Synonym = poison. Any chemical that causes harmful
biological effects.
toxicity.
The capacity of a chemical to produce harmful effects.
toxicity
test. A controlled test in which the effects
of a toxicant are studied on living cells, tissues, or
organisms.
toxin.
A toxicant produced by a living organism. [compare to
toxicant and contaminant]
toxicology.
The study of the adverse effects of chemicals on living
organisms.
voltage-gated
channel: A membrane channel protein, usually
in nerve and muscle, that opens (or closes) in response
to membrane depolarization. Voltage-gated channels generate
electrical impulses (= action potentials).
water
soluble/hydrophilic. Refers to chemicals that
are soluble in water but not in lipids. [compare to lipid
soluble]
xenobiotic.
Any chemical that does not occur in the normal biochemical
pathways of an organism; a xenobiotic compound is a compound
that is “foreign” to the organism.
