Common Toxicity Measurement Methods
Algae
Often the unicellular green algae is used to indicate toxicity. This method measures the inhibition of cell division caused by toxic substances. At high toxic concentrations, algaes can die. Hence, new algaes have to be stored and kept in stock to ensure further toxicity measurements after a toxic effect.
The algae test takes 72 hours and the supply of the test organisms must be secured by purchase or breed.
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Specific detectors measure the emitted light and draw conclusions on toxicity. Toxic substances cause a reduction of the emitted light.
Commonly, this standard method uses Vibrio fischeri as test organisms. These bacteria glow under optimal growth conditions (bioluminescence). The bioluminescence is reduced by toxic substances in the sample and may lead to death of the organisms.
The bioluminescence test takes 50 minutes. The used test organisms must be purchased or bred.
Daphnia
Daphnia are crustaceans between 0.2 to 5 mm in lenght. Commonly, these small animals called water fleas and are often used for the determination of toxicity. However, for toxicity measurements, they must not be older than 24 hours.
The used Daphnia Magna are very sensitive to heavy metals but less to other substances. Toxic substances cause the death of the organisms, following which the number of surviving organisms are counted.
The daphnia test takes 24 or 48 hours and the organisms must be bred.
Fish test
The fish test – also known as golden orfe test – describes an animal experiment, which aims to determine at what dilution of waste water all animals survive 48 hours. The result is the smallest integer value of the dilution of the waste water (GF value).
As with the common test methods, the toxic substances cause the death of the organisms. At the end of the test the number of surviving fishes are counted. In Germany the fish test has been replaced since 2005 by the fish egg test.
The fish test takes 48 hours. The used test organisms must be purchased or bred.