Overbased reaction products of distilled tall oil and magnesium hydroxide’

Toxicity to aquatic algae and cyanobacteria

Description of key information

No ecotoxicity studies are available for Distilled tall oil, magnesium salt. However, a number of studies are available that can be read across from to provide information on the rosin and fatty acid components of the substance.
There are a wide range of ecotoxicity results reported that can be read across from the rosin component of Fatty acids, tall oil, magnesium salts. The most conservative EL50 value is 39.6 mg/L, based on growth rate. An EL50 of 13 mg/L, based on growth rate, is read across from the fatty acid component of the substance. For classification purposes the worst case value of 13 mg/L is used. 

Additional information

 

A number of reliable studies are available that can be read across from the rosin and the fatty acid components of Distilled tall oil, magnesium salt.

 

A number of studies are available for rosin, hydrogenated rosin and rosin salts. These are read across to the rosin component of Distilled tall oil, magnesium salt. Reliable studies are available for rosin. Inveresk (2001) determined toxicity to Selenastrum capricornutum using WAFs. No analytical verification of test concentrations was conducted. The study determined an EL50 of >1000 mg/L, and a NOELR of 1000 mg/L based on growth rate. Another study is also available using Selenastrum capricornutum which also uses WAFs but did not carry out any analytical verification. An EL50 of >100 mg/L was determined in this study.

 

A study with Tall oil rosin, which is considered to be equivalent to rosin, is also available (Akzo Nobel 1998). The study used WAFs with no analysis of test concentrations. No toxicity was observed at a concentration of 100 mg/L.

 

A study was conducted with Resin acids and Rosin acids, hydrogenated, potassium salt (Eastman 2005), which did not analyse for test concentrations. An EC50 of 39.6 mg/L was determined based on growth and 16.6 mg/L based on biomass. NOEC values of 6.25 (growth rate) and <6.25 (biomass) were reported.

 

A reliable GLP guideline study was performed to assess the effect of Fatty acids C18-(unsaturated) lithium salts on the growth of the green alga Desmodesmus subspicatus (Harlan, 2010).  This result is read across to the fatty acid component of Distilled tall oil, magnesium salt. Following preliminary range-finding tests, Desmodesmus subspicatus was exposed to nominal loading rates of 1.0, 3.2, 10, 32 and 100 mg/l WAF (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at 24 ± 1°C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a haemocytometer and light microscope. Analysis indicated that the test item was unstable in culture medium particularly at the lower test concentrations employed. However, given that the toxicity cannot be attributed to a single component or a mixture of components but to the test item as a whole the results were based on nominal loading rates only. The 72-hour EL50 (growth rate) based on nominal loading rate was 13 mg/L WAF and the 72-hour EL50 (yield) based on nominal loading rate was 4.7 mg/L WAF. A NOELR value of 1 mg/L (growth rate and yield) was reported.