No IUPAC name is currently defined for Cashew (Anacardium occidentale) Nutshell Extract, Decarboxylated, Distilled (“Distilled Residue Grade”).

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

1. HYPOTHESIS FOR THE CATEGORY APPROACH (ENDPOINT LEVEL)
The basis for the adoption of a category approach for the three grades of processed Cashew Nutshell Extract is the commonality of the constituents and functional groups in the three grades and the common modes of action for specific localised endpoints that are manifest in physico-chemical, environmental fate and toxicological properties that are similar or follow a regular pattern as a result of structural similarity. The ECHA Final Decisions on the Annex IX and X (mammalian toxicology, ecotoxicology and environmental fate) Testing Proposals for three grades confirmed the applicability of a category approach which involves reading data across from the source substances Cashew Nutshell Extract, Decarboxylated, Distilled (Distilled Grade) and Cashew Nutshell Extract, Decarboxylated, Distillation Residue (Distillation Residue Grade) to the target substance Cashew Nutshell Extract, Decarboxylated (Technical Grade) by interpolation. In this context interpolation is “the estimation of a value for a member of the group using measured values from other members on both sides of that member within the defined group spectrum”. Further details on the justification for using the interpolation based read-across approach are given in the attached document “Report on the grouping and read-across rationale for the three grades of processed Cashew Nutshell Extract”. The interpolation approach has been applied to the Annex IX and X OECD TG211 and TG218 testing on Distilled and Distillation Residue Grades. For the Annex VII and VIII endpoints a programme of testing has been carried out to provide comparative information for the three grades and develop a data matrix to support the category and read-across approaches. This has involved generating reliable data for all Annex VII and VIII physico-chemical and environmental fate endpoints and certain mammalian toxicity properties. However, based on the discussions surrounding the Final Decisions it was not considered necessary to apply this approach retrospectively to address all identified data gaps at Annexes VII and VIII. The original data used for the registration of a single substance (Cashew Nutshell Liquid, CAS Number 8007-24-7) was largely based on data for Distilled Grade since this was considered to be the most (eco) toxicologically active form, given the higher content of low molecular weight constituents (such as cardanol) and the low content of polymeric species. However, for the short-term acute aquatic toxicity endpoints the testing on algae, invertebrates and fish was carried out on Technical Grade. The measured data for the key physico-chemical properties that underpin the likely short term aquatic toxicity of the three grades, namely water solubility and octanol-water partition coefficient, are consistent. Therefore, based on the use of the category approach it is considered appropriate to read-across from the existing short-term aquatic toxicity data for Technical Grade to the other two grades.
2. CATEGORY APPROACH JUSTIFICATION (ENDPOINT LEVEL)
For the toxicity to algae endpoint no test data is available for the registered substance Distillation Residue Grade. However data is available for the compositionally similar substance Technical Grade which is part of the category of the three grades of CNSL. In the algal toxicity study on Technical Grade there were no effects on specific growth rate of the marine alga Skeletonema costatum after 72 hours exposure in a reliable with restriction (Klimisch Code 2) ISO 10253 study at loading rates of ≤250 mg/l prepared using Water Accommodated Fractions. At higher loading rates of 500 and 1000 mg/l reductions in specific growth rate of 25 and 38% were recorded, relative to the controls. However, there is uncertainty associated with the measurements of cell density measured at the two highest loading rates since there was a disparity in the colour and character of those test solutions after 72 hours compared to those of the controls and 62.5, 125 and 250 mg/l WAFs. It is, therefore, possible that the changes observed were due to a physical rather than a toxicological effect. The highest loading rate of 1000 mg/l corresponds, in principle, to the water solubility limit given that no solvents were used in the preparation of the exposure concentrations. Therefore, based on the data generated it was concluded that there were no adverse toxicological effects of Technical Grade on algal growth at the substances water solubility limit. The available data for the three grades indicates that they all show low measured water solubility in the range 0.2 to 0.3 mg/l. All three substances also show high measured octanol-water partition coefficients (log Kow >6.2 in all cases). This data indicates that the measured data for the key physico-chemical properties that underpin the likely short term aquatic toxicity of the three grades are consistent. On this basis it would be expected that the three grades would show similar responses in the short-term aquatic toxicity tests. This hypothesis is currently supported by the results of the long-term OECD TG211 and TG218 ecotoxicity tests that have been conducted on both Distilled Grade and Distillation Residue Grade as part of the interpolation approach. Therefore, it is considered appropriate to read-across from the data for Technical Grade to Distillation Residue Grade with the result that it has been estimated that there will also be no adverse toxicological effects of Distillation Residue Grade on algal growth at the substances water solubility limit.

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

125 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rate

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

250 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rate

Basis for effect:

biomass

Remarks on result:

other: 95% CL: 210-300 mg/l nominal WAF loading rate (Calculated by the Litchfield and Wilcoxon method)

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

1 300 mg/L

Nominal / measured:

nominal

Conc. based on:

other: WAF loading rate

Basis for effect:

growth rate

Remarks on result:

other: It was not possible to derive 95% CL as the data generated does not fit the models available for the calculation of confidence limits

Conclusions:

It is considered appropriate to read-across from the data for Technical Grade to Distillation Residue Grade with the result that it has been estimated that there will also be no adverse toxicological effects of Distillation Residue Grade on algal growth at the substances water solubility limit.

Executive summary:

For the toxicity to algae endpoint no test data is available for the registered substance Distillation Residue Grade. However data is available for the compositionally similar substance Technical Grade which is part of the category of the three grades of CNSL. In the algal toxicity study on Technical Grade, there were no effects on specific growth rate of the marine alga Skeletonema costatum after 72 hours exposure in a reliable with restriction (Klimisch Code 2) ISO 10253 study at loading rates of <250 mg/l prepared using Water Accommodated Fractions. At higher loading rates of 500 and 1000 mg/l reductions in specific growth rate of 25 and 38% were recorded, relative to the controls. However, there is uncertainty associated with the measurements of cell density measured at the two highest loading rates since there was a disparity in the colour and character of those test solutions after 72 hours compared to those of the controls and 62.5, 125 and 250 mg/l WAFs. It is, therefore, possible that the changes observed were due to a physical rather than a toxicological effect. The highest loading rate of 1000 mg/l corresponds, in principle, to the water solubility limit given that no solvents were used in the preparation of the exposure concentrations. Therefore, based on the data generated it was concluded that there were no adverse toxicological effects of Technical Grade on algal growth at the substances water solubility limit. The available data for the three grades indicates that they all show low measured water solubility in the range 0.2 to 0.3 mg/l. All three substances also show high measured octanol-water partition coefficients (log Kow >6.2 in all cases). This data indicates that the measured data for the key physico-chemical properties that underpin the likely short term aquatic toxicity of the three grades are consistent. On this basis it would be expected that the three grades would show similar responses in the short-term aquatic toxicity tests. This hypothesis is currently supported by the results of the long-term OECD TG211 and TG218 ecotoxicity tests that have been conducted on both Distilled Grade and Distillation Residue Grade as part of the interpolation approach. Therefore, it is considered appropriate to read-across from the data for Technical Grade to Distillation Residue Grade with the result that it has been estimated that there will also be no adverse toxicological effects of Distillation Residue Grade on algal growth at the substances water solubility limit.

Additional information

In a 72 hour toxicity study, the cultures of Diatom (Skeletonema costatumCCAP 1077/5) were exposed to Cardolite NC-603 (Cashew (Anacardium occidentale) Nutshell Extract, Decarboxylated ("Technical Grade")) at nominal concentrations of 0, 62.5, 125, 250, 500 and 100 mg/l nominal WAF loading rate under static in accordance with the guideline ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum).

 

The EL₅₀based biomass was 250 mg/l and the EL₅₀based on growth rate was 1300 mg/l. There were no compound related phytotoxic effects.

 

The study is classified as Klimisch Code 2 (reliable with restriction) as it was performed to an internationally recognised method (ISO 10253) and was conducted to Good Laboratory Practice.

 

Read-across justification: The read across source substance is Cashew (Anacardium occidentale) Nutshell Extract, Decarboxylated ("Technical Grade").  For a full description of the read-across case, please refer to the document "Rationale for the grouping and read-across approach for the three grades of processed Cashew Nutshell Extract" located in Section 13.