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EC number: 200-543-5
CAS number: 62-56-6
Two publications are available that are reporting 96-hr effect concentrations for the green algae Scenedesmus subspicatus Chodat:- Geyer et al. (1985): EC10 = 0.3 - 0.6 mg/L, EC50 = 4.8 - 10 mg/L- Friesel et al. (1984): EC10 = 0.5 - 0.7 mg/L, EC50 = 3.8 - 5.4 mg/LBoth publications report values that are within in the same range. Due to precautionary principles, the lowest reported value for the EC10 and EC50, respectively, is used as key value in the risk assessment for thiourea.
Friesel at al. (1984) and Geyer et al. (1985) both
report 96 -hr EC50 and EC10 values of thiourea for the green algae
Scenedesmus subspicatus Chodat. In both cases results were determined in
test according to the guideline "Hemmung der Zellvermehrung bei der
Grünalge Scenedesmus subspicatus Chod." of the German Environmental
Protection Agency (UBA; May 1982). But as the documentation of both
experiments, especially with regard to the results, is insufficient for
assessment, the publications are rated as Klimisch III.
According to current guidelines, the standard test
duration for testing of algae toxicity is 72 hours instead of 96 hours.
But as the test duration in the reported experiments is longer than in
standard tests, the results are considered to rather overestimate the
toxicity of thiourea to algae. Thererfore, the results are deemed
sufficiently precautionary to be used in the risk assessment of the
In addition, as both publications report results that
are within the same range, the results are used in a weight-of-evidence
approach to assess the environmental risk of thiourea:
- Geyer et al. (1985): EC10 = 0.3–0.6 mg/L,
EC50 = 4.8–10 mg/L
- Friesel et al. (1984): EC10 = 0.5–0.7 mg/L,
EC50 = 3.8–5.4 mg/L
Due to precautionary principles, the lowest reported
value for the EC10 and EC50, respectively, is used as key value in the
risk assessment for thiourea.
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