Principles of toxicity testing
Toxicity tests are carried out using
organisms that are sensitive to pollution,
such as certain species of fish, algae,
and riverine macroinvertebrates (or river
insects), and the water flea, Daphnia.
These organisms should be a true
representation of their various trophic
levels in the food chain.
Aquatic toxicity data is used in all
these applications to monitor pollution
of water bodies.
Examples of a test battery
•
•
•
•
Poecilia reticulata (vertebrate)
acute lethality. Duration: 96 hours.
Visual.
Daphnea pulex (invertebrate)
acute lethality. Duration: 24/48
hours. Visual.
Selenastrum capricornutum (algal
growth inhibition). Duration: 72
hours. Spectrophotometric.
Allivibrio fischeri (bioluminescent
bacteria). Duration: 15 and 30
minutes. Luminometer with
software.
The two steps when performing
toxicity testing procedures are:
• Screening (acute lethality) to
determine whether a sample is
toxic or not.
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This illustrates the importance of each
test and their interdependence, and
also that, should any of these ‘legs’ be
taken away, the ‘pot’ (testing system)
will collapse.
The tests are in vitro and performed
in a temperature-controlled laboratory.
innovations
or more substances, waste, or
environmental factors alone or
in combination (American Public
Health Association, 1989).
Each of the legs of the Driepootpot
(three-legged pot) approach represents
one of the three approaches when
doing aquatic toxicological testing:
1. Traditionally quantitative
chemical analyses
• Over- and/or underestimation of
real danger.
2. Biological approach
• Biological indexes (SASS, fish
health index, and so on).
• Evaluate hazard resulting from
combined impact of all pollutants
present.
• Qualitative and quantitative
comparison of indigenous fauna
and flora in aquatic environments.
3. Toxicity testing
• Procedure in which the
response of aquatic organisms
is used to detect or measure
the presence or effect of one
The approach
Uncertainty still exists regarding the provision of standardised training procedures to potential toxicity analysts.