Tall oil, sodium salt

Endpoint summary

Description of key information

Reliable short-term toxicity data for aquatic organisms are available for the substance or a related substance, Crude Tall Oil (CTO, EC number 931-433-1). The data show that short-term LL₅₀ and EL₅₀ values for fish (Danio rerio), invertebrates (Daphnia magna) and algae (Pseudokirchnerella subcapitata) were 20 mg/L, between 32 and 320 mg/L and >100 mg/L respectively.

  

There are no data for long-term toxicity of the substance to aquatic organisms. However reliable results are available for the closely-related substance, Crude Tall Oil (EC number 931-433-1). A 21-day NOELR (No Observed Effect Loading Rate) of ≥1 mg/L has been determined for the effects of the substance on reproduction, growth and mortality of Daphnia magna.

Testing to determine long-term toxicity to fish is not considered to be appropriate on the grounds that:

- result from short-term tests with the substance or with the related substance Crude Tall Oil (EC number 931-433-1) indicate that fish and invertebrates are similarly susceptible and algae are less susceptible.

Reliable long-term invertebrate test data for Crude Tall Oil (EC number 931-433-1) show an absence of toxicity at a loading rate of 1 mg/L.

- Calculation of PNECs for the aquatic compartment will be based on data for the blocks of constituents rather than on data for the whole substance.

Testing for long-term toxicity to fish will therefore not contribute further to the database that is required to complete the assessment of the substance.

New measured data are available for rosin and its rosin acid and salts (whole substance, CAS 8050-09-7), which has been used as supporting data for read-across to the rosin acids in Block 2 (ECHA 2013f). Data are also available on plant sterols (CAS 94109-75-5), used as supporting data for sitosterols and analogues (Block 11) (ECHA 2013g).

Test results are available with rosin, which forms part of Block 2 (rosin acids). The key data indicates that the predictions and the data available are in good agreement. The key short-term data for rosin itself and the rosin and rosin acid salts included in the category, indicate that rosin is toxic in the range LC/LL₅₀ 1.7 to >1000 mg/L to fish, EC/EL₅₀ 1.6 to >2000 mg/L to aquatic invertebrates and EC/EL₅₀ 9.6 to >100 mg/L to algae. Algal NOELRs and NOEC have been reported in the range 6.25 to ≥1000 mg/L. The data has been taken from rosin’s disseminated dossier (ECHA 2013f).

A short-term toxicity study with fish is available with plant sterols, read-across to block 11 (sitosterols and analogues), where an LL₅₀ value of >10 000 mg/L has been derived. This value is in agreement with the predictions for the constituents in block 11, where no effects at the limit of solubility have been predicted. The data has been taken from the plant sterols disseminated dossier (ECHA 2013g).

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.

The use of ecotoxicity data for the read-across substance Rosin (EC 232 -475 -7, CAS 8050-09-7) for Block 2 of TOS is justified on the following basis.

Rosin is a UVCB substance which is a solid form of natural resin obtained from conifers, mainly pine trees. The definition of rosin covers tall oil rosin, gum rosin and wood rosin. These three types of rosins are principally made up of rosin acids and other constituents such as fatty acids; sitosterols may be found. Block 2 of TOS contains various sodium salts of rosin acids such as abietic acid, dehydroabietic acid, pimaric acid, palustric acid and isopimaric acid. The rosin acids found in the registered substance, TOS, are the same as the rosin acids found in gum and wood rosins, and in similar proportions, because they are obtained from same precursors in pine trees (McSweeney et al.,1987). The only difference between gum rosin and TOS is that the rosin acids are present as sodium salts in TOS. In aqueous media, the sodium salts will be dissociated to the parent acid and sodium. The sodium, being a ubiquitous and essential element in nature, is not expected to contribute to the toxicity properties of the substance. Therefore, available measured data for rosin are read-across for the information requirements of Blocks 2 of TOS.

The use of ecotoxicity data for the read-across substance Plant Sterols (EC no. 619-079-3, CAS 949109-75-5) for Block 11 of TOS is justified on the following basis.

Plant sterols is a UVCB substance. The substance is said to occur naturally in small amounts in a range of plant foods which includes fruits, vegetables, nuts, seeds, legumes, cereals and vegetable oils. The composition of plant sterols includes β-sitosterol (EC no: 201-480-6), campesterol (EC no: 207-484-4), stigmasterol (EC no: 201-482-7), Brassicasterol (EC no: 207-486-5), stigmastanol (EC no: 201-479-0) and residual sterols. Block 11 of TOS contained various sterols such as campesterol, stigmasterol, campstanol, sitostanoland β–sitosterol (main sterol present in TOS). It is therefore considered applicable to read-across data for plant sterols to sterol constituents of TOS (Block 11) due to compositional similarity.