Tall oil, sodium salt

Long-term toxicity to aquatic invertebrates

Description of key information

There are no data for long-term toxicity of the substance to aquatic invertebrates. However reliable results are available for the closely-related substance, Crude Tall Oil (EC number 931-433-1). A 21-day NOELR of ≥1 mg/L (tested as Water Accommodated Fractions, WAFs) has been determined for the effects of the substance on reproduction, growth and mortality of Daphnia magna.

Read-across justification:

The use of ecotoxicity data for the read-across substance Crude Tall Oil (CTO; list number 931-433-1) is justified on the following basis.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH

A read across from Crude Tall Oil to TOS can be justified on the following basis.

Crude Tall Oil (CTO), list number 931-433-1, is the term applied to the processed mixture of naturally occurring compounds extracted from tree species like pine, spruce, birch and aspen. CTO is formed by the acidification of TOS, therefore, CTO and TOS are similar substances. They differ only in the water content and that CTO does not contain sodium salts of the fatty/rosin acids.

The main constituents of TOS are sodium salts of saturated and unsaturated C14-20 fatty acids (5-45% w/w), rosin acid sodium salts (10-40% w/w), water (25-45% w/w), sterols (1-10% w/w), and non-volatile lignin/cellulose fibre/oligomeric acids (3-20% w/w). In addition, the following minor constituent blocks are present: terpenes, sesquiterpenes, abietenes and labdanes, C30 branched polyakenes, 3,5 -dimethoxystilbene, rosin alcohol and aldehyde isomers and saturated/unsaturated alcohols and terpene alcohols (each <3% w/w).

The same constituents are present in CTO, with only the following differences:

-The fatty acids and rosin acids in TOS are present as their sodium salts whereas for CTO they are present as acids. In aqueous media, the sodium salts are dissociated into sodium and the parent acid. The sodium, being a ubiquitous and essential element in nature, is not expected to contribute to the toxicity properties of the substance.

-TOS contains 25-45% water compared to trace amounts in CTO; other constituent groups are therefore present at lower levels in TOS but in similar proportions to CTO.

The hypothesis for the read-across approach is that in the environment and under standard laboratory test conditions organisms would be exposed to essentially the same constituents (and in similar proportions) whether they originate from TOS or CTO and so the ecotoxicity of TOS would be substantially the same as that for CTO.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

Both CTO and TOS are UVCB substances that contain fatty acids, rosin acids, neutrals such alcohols, sterols, aldehydes etc. For UVCB substances, impurities are not considered relevant for substance identification. The fatty and rosin acids present in TOS are in the form of the sodium salt. In the environment, the sodium salts of fatty and rosin acids will dissociate and speciate in a similar way to each other. The sodium salts in TOS will ionise into sodium ions and a mixture of the acid anion/parent acid (depending on the pH) and CTO will dissociate into the same mixture of the acid anion/parent acid (again depending on the pH). Sodium is a ubiquitous, essential element in nature and will not contribute to the toxicity of the acid and as such it is considered relevant to read-across the available data for CTO to TOS.

Therefore, it can be concluded that in the environment and under standard laboratory test conditions, the organisms would be exposed to essentially the same constituents and (and in similar proportions) whether they originate from TOS or CTO and so the read-across of ecotoxicity data from CTO to TOS is justified.