Octanoic acid, zinc salt, basic

Endpoint summary

Description of key information

Reliable acute and chronic toxicity data of octanoic acid, zinc salt, basic are available for algae but not for all trophic levels: The lowest EL10 and EL50 values for the 72-h growth rate inhibition of P. subcapitata in standard test medium amount to 0.02 and 0.16 mg/L, respectively. In the assessment of environmental toxicity of octanoic acid, zinc salt, basic, read-across to the assessment entities soluble zinc substances and octanoic acid is applied since zinc cations and octanoate anions determine its fate and toxicity in the environment.

Acute (short-term) toxicity data:

The toxic effects of the dissolved fraction of Octanoic acid, zinc salt, basic on the growth rate of algae (Pseudokirchneriella subcapitata) was studied in state-of-the-art tests according to OECD Guideline 201 (Wenzel, 2013a,b). The dissolved fractions were prepared according to OECD Series # 29 in standard test medium to enable the classification for a potential aquatic hazard based on the dissolved fraction. Thus, the toxicity of the dissolved fractions of the loadings 0.01, 0.1, 1.0, and 10.0 mg/L was tested; the lowest EL10 and EL50 values for the 72-h inhibition of growth rate of P. subcapitata in standard test medium are 0.02 and 0.16 mg/L, respectively. The toxicity to the trophic levels invertebrates and fish is assessed based on read-across of the aquatic toxicity of the respective assessment entities zinc cations and octanoic acid:

The lowest 48-h EC/LC50 values of "zinc" for the trophic levels algae, invertebrates and fish range from 0.136 mg Zn/L to 0.78 mg Zn/L depending on solution pH and hardness with the lowest EC reported for algae and the 2nd lowest reported for invertebrates (Ceriodaphnia dubia) - both at neutral-high pH and low hardness.

Regarding "octanoic acid”, based on short-term toxicity data available for freshwater algae, invertebrates and fish, the lowest acute effect concentration is the 48-h ErC50 of 15 mg/L decanoic acid for P. subcapitata and the 2nd lowest the 96-h LC50 of 51 mg/L octanoic acid observed for Oryzias latipes.

Chronic (long-term) toxicity:

Studies of octanoic acid, zinc salt, basic resulted in an EL10 value of 0.02 mg/L (dissolved fraction after 7 days in accordance with OECD Series # 29) in the standard test medium for the green algae Pseudokirchneriella subcapitata. The toxicity to the trophic levels invertebrates and fish is assessed based on read-across of the aquatic toxicity of the respective assessment entities zinc cations and octanoic acid:

 

Based on the comprehensive data set on aquatic long-term toxicity of zinc and mean effect concentrations for standard species (i.e. Pseudokirchneriella subcapitata, Daphnia magna, Oncorhynchus mykiss), algae appear to be the most sensitive taxa; respective NOEC/EC10 values for the long-term toxicity of zinc to invertebrates and fish are substantially higher (more than factor of 4) than the NOEL/EL10 value for algae. "Species mean” NOEC values used for the PNEC derivation (freshwater PNECadd, aquatic), range from 19 to 530 µg/l with Pseudokirchneriella subcapitata (algae) being the most sensitive and invertebrtaes (Ceriodaphnia dubia) being second most sensitive.

Regarding the assessment entity “octanoic acid”, reliable long-term toxicity data for freshwater organisms are also available for three trophic levels. The lowest chronic effect concentration is the 21-d NOEC of 0.2 mg/L observed for the effect of decanoic acid on the reproduction of the freshwater invertebrate Daphnia magna.

 

Regarding aquatic microorganisms, octanoic acid, zinc salt, basic is not toxic up to 100 mg/L based on results of the toxicity control in the OECD 301F biodegradation test. However, the lowest NOEC for nitrification inhibition of zinc amounts to 0.1 mg Zn/L based on an ISO 9509 nitrification inhibition test.

 

For more detailed information, please refer to the respective endpoint summaries for the assessment entities “zinc” and “octanoic acid”.