A study of the priority substances of the Water Framework Directive ...

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APPENDIX C
Short list of words and terms
Acute oral LD50: Acute lethal dose for 50 percent
of a group of test animals (rats) within a
defined period of time, often 24 hours. The dose
is normally given in micrograms per gram body
weight.
BCF: Bio-concentration factor. Defined as the
concentration of a chemical in an organism
(divided by the concentration in a reference
compartment (e.g. food, surrounding water)).
ClassLab: "Harmonised Classifications and
Labelling for Substances, refers to the
Norwegian Stofflisten. Stofflisten has some
information that is specific to Norway.
EC50: Effect concentration. The concentration
that gives effects on 50 percent of test animals
within a given period of time.
Half life: Half life (or DT50) is the time it takes
for half the amount of a chemical to disappear.
This may happen due to evaporation, hydrolysis,
photo degradation, chemical degradation,
degradation by bacteria etc. When using values
for half life it should be taken into considera-
A study of the priority substances of the Water Framework Directive
TA-2140/2005
tion that chemicals which are easily degraded by
for instance sunlight may be very persistent in
groundwater or sediments, and that a chemical
may be degraded via several routes simultaneously.
Thus different half life values are given for each
substance for depending on where the chemical
is released and type of degradation.
LC50: Lethal concentration (usually in water)
for fish or invertebrates, the concentration
required to kill 50 percent of a group of fish or
invertebrates in a given time (normally 24 - 96
hours)
Log Kow:Log Octanol-Water Partitioning
Coefficient. High Log Kow indicates a compound
which will preferentially partition into
soil organic matter rather than water.
NOEL/NOAEL: No observed effect level / No
observed adverse effects level. The highest
amount of a substance that can be administered
without any effects on the test animals.