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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

OECD Guideline 201, GLP, key study, validity 1:
96h-ErC50 (Selenastrum capricornutum) = 0.492 mg/L (nominal, as main ingredient)
96h-NOECr (Selenastrum capricornutum) = 0.048 mg/L (nominal, as main ingredient)
ISO Guideline 10253, GLP, key study, validity 2:
72h-ErC50 (Skeletonema costatum) = 0.12 mg/L (nominal, as main ingredient)
72h-NOECr (Skeletonema costatum) = 0.075 mg/L (nominal, as main ingredient)
In conclusion, THPS is considered very toxic to aquatic algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.492 mg/L
EC50 for marine water algae:
0.12 mg/L
EC10 or NOEC for freshwater algae:
0.048 mg/L
EC10 or NOEC for marine water algae:
0.075 mg/L

Additional information

Four studies are available to assess the toxicity of the active substance THPS to algae. These studies were performed on the THPS in solution in static conditions, with freshwater and marine species. The relevant results were expressed as main ingredient (100% active substance).

There is one study of reliability 1 on the freshwater species Selenastrum capricornutum (Jenkins, 1991d) and three studies of reliability 2 on the marine species Skeletonema costatum (Hushagen, 1994; Brakstad, 1994; Vryenhoef, 2004). All studies lead to similar NOEC and EC50 values.

The study of best reliability and lowest NOEC value has been defined as key study (Jenkins, 1991d), and the study of best reliability and lowest EC50 value has also been defined as key study (Hushagen, 1994).

Results are expressed in the table below (as main ingredient):

Test method

Species

Endpoint / Type of test

Exposure

Reliability

Flag

Results (ErC50 (95% CL), mg/L)

Results (ErC10 (95% CL) or NOECr, mg/L)

Reference

OECD Guideline 201

Selenastrum capricornutum (freshwater species)

Growth inhibition / acute and chronic

Static, 96h

1

KS

0.492 (0.408-0.630)

0.048

Jenkins, 1991d

ISO 10253

Skeletonema costatum (marine species)

Growth inhibition / acute and chronic

Static, 72h

2

KS

0.12 (0.075-0.24)

0.075

Hushagen, 1994

ISO 10253

Skeletonema costatum (marine species)

Growth inhibition / acute and chronic

Static, 72h

2

SS

0.266 (0.244-0.290)

0.044 (0.032-0.057)

Brakstad, 1994

ISO 10253

Skeletonema costatum (marine species)

Growth inhibition / acute and chronic

Static, 72h

2

SS

0.465

0.0469

Vryenhoef, 2004*

* This study is not owned by Solvay, the test report is available on the US EPA web site at EPA/OPPT/Toxic Substance Control Act Section 8(e), the test substance was not manufactured by Solvay,THPS main ingredient content is 75 %.

According to the key studies, THPS is considered very toxic to aquatic algae with an EC50 value based on growth rate at 0.12 mg/L on a marine algae species (Skeletonema costatum) and a NOEC value based on growth rate at 0.048 mg/L on a freshwater algae species (Selenastrum capricornutum).