Fatty acids, tallow, zinc salts

Toxicity to aquatic algae and cyanobacteria

Description of key information

72 h, ErL50 (Pseudokirchneriella subcapitata): > 100 mg/L; read-across

72 h, ErL10 (Pseudokirchneriella subcapitata): 3.31 mg/L; read-across

Additional information

No studies are available on the toxicity of Fatty acids, tallow, zinc salts to algae. In accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5, a read across to the structural analogue Fatty acids, C16-18, zinc salts (CAS No. 91051-01-3) was conducted. Based on similar structure, physico-chemical properties and zinc content, the ecotoxicological profile of the two substances is expected to be comparable. Further justification is given within the endpoint summary 6.1 and the analogue justification. The data available for Fatty acids, C16-18, zinc salts and the supporting data available for inorganic zinc substances are discussed below.

Fatty acids, C16 -18, zinc salts:

The toxic effects of Water Accommodated Fractions (WAF) of Fatty acids, C16-18, zinc salts on the growth rate of algae (Pseudokirchneriella subcapitata) were studied in three state-of-the-art tests according to OECD Guideline 201 (Wenzel, 2010a,b; Wenzel, 2013). While in the first test, the WAF of a loading of 100 mg/L was diluted in series to allow the calculation of toxicity parameters (EC10, EC50), the WAFs of several loadings (1, 10, and 100 mg/L) were tested in the second test according to OECD Series No. 23 to enable the classification based on WAFs. The first study has to be disregarded with respect to the fact that the preparation of test concentrations was done from one WAF in a series (Wenzel 2010a). In the second test the WAF were each prepared separately, but no loading-dependent inhibition was obtained (Wenzel 2010b). The inhibition was clearly higher at 1 mg/L loading than at 10 mg/L, so also this study has to be disregarded. Therefore, a further full test with test concentrations 0.01, 0.1, 1.0, 10.0, and 100 mg/L, each prepared separately as WAF, was conducted (Wenzel, 2013). This study was also performed according to OECD Guideline 201 and GLP. Since a loading-dependent inhibition was observed and also the further validity criteria according to OECD 201 were met, this study can be assessed as valide and the effect values for growth rate could be taken into account. The ErL50 (72 h), ErL10 (72 h) and the NOEL (72) were stated as > 100 mg/L, 3.31 mg/L and 0.1 mg/L, respectively.

For further hazard assessment, the EC10 was used as chronic value, as recommended by the Guidance on information requirements and chemical safety assessment Chapter R.10: Characterisation of dose [concentration]-response for environment Table R.10-1 (ECHA, 2008). As stated in the guidance document, there has been a recommendation within OECD in 1996 to phase out the use of the NOEC, in particular as it can correspond to large and potentially biologically important magnitudes of effect. The advantage of regression method for the estimation of ECx is that information from the whole concentration-effect relationship is taken into account and that confidence intervals can be calculated. Also the OECD Guideline 201 states: “Recent scientific developments have led to a recommendation of abandoning the concept of NOEC and replacing it with regression based point estimates ECx. An appropriate value for x has not been established for this algal test. A range of 10 to 20 % appears to be appropriate (depending on the response variable chosen), and preferably both the EC10 and EC20 should be reported.”(OECD, 2011).

ZINC:

Acute freshwater toxicity tests of high quality and relevancy performed according to standard protocol. Information is available on 1 species which is in both the acute and chronic aquatic database on zinc the most sensitive. The lowest IC50 value is taken as reference value for classification for acute effect at neutral/high pH.

Chronic freshwater toxicity tests of high quality and relevancy according to standard protocol or equivalent. Data on 2 species, one of which the most sensitive of all freshwater organisms, second species is less sensitive.

Chronic seawater tests of high quality and relevancy according to standard protocol or equivalent. Data on 12 species, for which 3 species are in the low part of the species sensitivity distribution. One species of macro-algae is the second most sensitive of all seawater organisms.

The data, as summarised in the overall endpoint summary 6.1, show that algae represents the most sensitive trophic level among aquatic organisms. For a comprehensive overview of the acute toxicity of (soluble) zinc to algae,see Chemical Safety Assessment of "Zinc" within the framework of Regulation (EC) No 1907/2006 in the technical dossier (IUCLID section 13).

 

CONCLUSION:

Three studies on algal toxicity were conducted with the structural analogue Fatty acids, C16-18, zinc salts. However, a loading-dependent inhibition was only observed in one study, on which the assessment is based. In this study ErL50 and ErL10 values of > 100 mg/L and 3.31 mg/L were observed, respectively. The algae study is the only chronic data available for aquatic organisms. As based on the data available for inorganic zinc substances, algae is the most sensitive organism, this data can be used as reference value for the hazard assessment.