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Toxicity to aquatic algae and cyanobacteria

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Description of key information

A phytotoxicity test was performed to determine the effect of 1,3-diphenylguanidine on the freshwater alga Selenastrum capricornutum. Results of the test are reported as 24-, 48-, 72-, and 96-hour EC50's (the concentrations of the test material estimated to cause a 50% decrease of in vivo chlorophyllian exposed cultures as compared to the control at the specified times). Cell numbers in exposed and control cultures were also determined after 96 hours of exposure and another 96-hour EC50 was calculated (the concentration of the test material estimated to cause a 50% decrease of cell numbers in exposed cultures as compared to the control). This study on the toxicity of 1,3 -diphenylguanidine to algae permitted to estimate a EC50 -96h = 1.4 - 1.7 mg/l concerning the cell division rate (determined by cell counter) and an NOEC at 0.3 mg/l

Key value for chemical safety assessment

EC50 for freshwater algae:
1.4 mg/L
EC10 or NOEC for freshwater algae:
0.3 mg/L

Additional information

A phytotoxicity test was performed at Bionomics Marine Research Laboratory (BMRL), Pensacola, Florida, to determine the effect of DPG (BN-79-1384358-le) on the freshwater alga Selenastrum capricornutum. Results of the test are reported as 24-, 48-, 72-, and 96-hour EC50. Cell numbers in exposed and control cultures were also determined after 96 hours of exposure and another 96-hour EC50 was calculated.

This study on the toxicity of 1,3 -diphenylguanidine to algae permitted to estimate an EC50 -96h = 1.4 - 1.7 mg/l concerning the cell division rate (determined by cell counter). The results obtained during this test are summarized hereafter:

EC50s based on chlorophyll a determination:
24h >5.6 mg/l 
48h 3.5 mg/l (0.2-56)
72h 2.0 mg/l (0.2-17)
96h 1.4 mg/l (0.2-7.4)
96h EC50 based on cell number = 1.7 mg/l (0.4-7.4)
NOEC not calculated but based on available data can be taken as 0.3 mg/l at both 72 and 96h (for chlorophyll a and growth rate data at 96h).

In another test relative to the cell division inhibition (DIN 38412 part 9) the following values were determined for the green algae Scenedesmus subspicatus after 72 hours at a pH of 7.6 - 8.9 and 23°C+/-2°C: EC10 = 0.013 mg/l and EC50 = 2.6 mg/l (based on the biomass); EC10 = 2.1 mg/l and EC50 = 7.5 mg/l (based on the growth rate).