Tall oil, sodium salt

Endpoint summary

Description of key information

Introduction

TOS is a UVCB substance and therefore two aspects need to be considered in relation to physicochemical properties. In the context of raw material handling and safe use it is important to understand the properties of the substance as a whole. However, for the determination of fate and effects in the environment it is important to consider the properties of the constituents.

An overview of the physicochemical properties of the whole substance and that of the individual constituents is discussed below. The predicted results for key physicochemical properties are in Table 1.4.2.

Physicochemical properties of whole substance

For the measured results reported for the registered substance (TOS), variations in the measured results below may be due to the natural variations in the composition of the substance. Various samples e.g. TOS 19, TOS 24 and TOS 28 that are typical/representative of the registered substance was used for the studies were relevant.

Physical appearance

The substance has been reported as a viscous liquid at standard temperature and pressure. TOS is a UVCB, variations in the physical appearance (colour) of the substance may occur depending on factors such as species of wood and manufacturing method which together influence the composition of the substance.

Melting/freezing point

Pour point values of 265 K (-8°C), 306 K (33°C) and 307 K (34°C) were determined for samples of the registered substance. The studies were conducted in accordance with relevant test method and in compliance with GLP.

Boiling point

Three boiling point studies are available for the registered substance. Boiling temperature of >673 K (>400°C) was determined for samples of the registered substance in accordance with relevant test methods and in compliance with GLP. During the studies, as heating continues, loss of volatile fractions was observed from approximately 373 K (100°C).

Relative density

Relative density studies have been conducted on different samples of the registered substance. Relative density values of 0.76, 1.05 and 1.06 at 20 ± 0.5°C were determined for samples of the substance in accordance with a relevant test method and in compliance with GLP.

In another study, a density value of 1026 kg/m³ was obtained for TOS. The substance is a UVCB; hence variation in the results could be as a result of the nature and composition of the samples tested.

Vapour pressure

TOS is a UVCB substance with varied composition. The vapour pressure of individual constituents of TOS was determined to be in the range 3.8E-16 to 5.4E+2 Pa at 25°C using validated QSAR estimation methods.

The vapour pressures of constituent blocks range from 2.5E-8 Pa to 5.4E+2 Pa at 25°C.

The vapour pressure of the whole substance was calculated by multiplying the mole fraction of each constituent by its predicted vapour pressure and summing the results.

The equation is summarised below:

Vapour pressure = Ʃ(a/b) x c

Where: a = Number of moles of individual constituents of TOS

           b = Total moles of TOS constituents

           c = Vapour pressure of individual constituents

Using the above expression, an estimated total vapour pressure value of 1.28 Pa was obtained for the substance as a whole by summation of the contributions of the constituents.

Surface tension

A surface tension value of 55.5 mN/m at 21.5 ± 0.5°C was determined for a sample of the registered substance. The test substance is found to be slightly surface active. In some samples of TOS, surface tension could not be determined due to the formation of micro-emulsion during water solubility determination.

In Drew and Propst (1981), surface tension in the range of 32.2 to 32.7 dynes/cm (32.2 to 32.7 mN/m) at 30°C was reported for the substance.

The test substance is a UVCB substance, variations in the result could occur as a result of the nature and composition of the samples tested.

Water solubility

A water solubility value of 0.0697 g/L at 20°C was determined for a sample of the registered substance using a relevant test method and in compliance with GLP. Some other samples of TOS formed a micro-emulsion during the preliminary water solubility measurement; therefore no definitive study could be conducted for the test substance. In a supporting study, a sample of the substance was found to be mutually miscible with water at ambient temperature of 22 -23°C.

The water solubility of the constituents of TOS was determined to be 9.4E-7 to 3.4E+2 mg/L using validated QSAR estimation methods. The water solubilities of constituent blocks range from 2.2E-6 to 5.7 mg/L at 20°C.

Partition coefficient

Log K_ow of 3.3 to 10.0 was determined for constituents of TOS using validated QSAR estimation methods. For the fatty acid and rosin acid constituents that can dissociate in solution, the predicted log K_ow was corrected for dissociation using the relevant equation.

For environmental risk assessment, the properties of the substance are assessed using the ‘block approach’. The log K_ow of each block has been determined based on the weighted average of each constituent in the block. Predicted log K_ow in the range of 3.7 to 10.0 was determined for all ‘blocks’ in TOS. All calculated log K_ow values above 10 are limited to an upper limit of 10 since it is not technically feasible to measure log K_ow values higher than this. In addition, since log K_ow is an important parameter in the assessment of bioaccumulation (B) which is part of PBT assessment; the raw calculated log K_ow is used. Therefore, for assessment of 'B', TOS has a raw log K_ow in the range 3.3 to 19.6.

Viscosity

Viscosity values of 957000 mPa.s, 98300 mPa.s and 8290000 mPa.s at 30°C were determined for three samples of TOS in studies conducted in accordance to appropriate test guideline and in compliance with GLP. Viscosity values of 3200 mPa.s at 21°C, 2100 mPa.s at 60°C and 2000 mPa.s at 70°C was determined for another sample of the registered substance.

Drew and Propst (1981) also reported a viscosity value of 7000 centistokes at 80°F for a sample of TOS.

The viscosity of the substance varies due to the nature and composition of the samples.

Flash point

There is no measured flash point study for TOS. Therefore, available data was read-across from a structural analogue, crude tall oil (CTO). A flash point of 121 – 185°C has been determined for CTO using a closed cup method according to ASTM D3278. In a published literature, flash point in the range of 385 – 420°F (196 - 216°C) was reported for CTO using an open cup (Cleveland) method according to Test Guideline D-803 ASTM (Drew and Propst 1981). Since TOS has a higher amount of water and lower amount of terpenes (volatile constituents) compared with CTO and as such, it is expected that the flash point of TOS will be greater than that of CTO. Therefore, the flash point of TOS is reported as greater than the lowest flash point determined for CTO i.e. >121°C for the purpose of classification and labelling.

Flammability

The substance is not classified for flammability on the basis of a flash point of >121°C. The substance does not have pyrophoric properties or liberate flammable gases in contact with water based on experience in use and handling.

Auto-ignition temperature

There is no measured auto-ignition temperature study for TOS. Therefore, available data was read-across a structural analogue, crude tall oil (CTO). An auto-ignition temperature value of 276°C at 99.17 to 100.85 kPa was determined for CTO using a relevant test method and in compliance with GLP. Since TOS has a higher amount of water and lower amount of terpenes (volatile constituents) compared with CTO, it is expected that the auto-ignition temperature of TOS will be greater than that of CTO. Therefore, the auto-ignition temperature of TOS is reported as >276°C.

Oxidising properties

TOS is not considered to be oxidising.

Explosive properties

TOS is not explosive.

pH

Several studies are available for the pH of TOS. pH values of 10.78, 11.39 and 11.49 at 25°C were determined for a 1% aqueous solution of three samples of TOS. In addition, pH values of 12.98, 13.34 and 13.5 at 25°C were determined for neat samples of the registered substance.

Metal corrosion

Three samples of TOS were determined not to be corrosive to metals.

Dissociation constants

No measured data for dissociation constant of TOS constituents are available. The pK_a values for the constituents are predicted using a relevant estimation method.

While the acid constituents (Fatty and Rosin acids) group in TOS is capable of dissociation, neutral constituents such as alcohols and sterols are extremely weak acids and only dissociate under strongly basic conditions. In the range of pH usually considered relevant to the human body and environment, i.e. pH 2-9, acid constituents will dissociate while the neutrals will be non-ionised. The acid constituents in TOS have predicted pK_a of 4.6 – 4.8 using a generally acceptable prediction method. For the alcohols and sterols, the predicted pKa is in the range 15.5 to 17.6.

Physicochemical properties of constituents

The individual constituents of the substances show variation in their physicochemical, degradation and toxicological properties. In the environment, each individual constituent behaves independently.

For the purposes of assessing environmental fate and behaviour it is essential to consider the properties of individual constituents, and whole property data have no real scientific meaning or significance. Some identified constituents are only present in trace/residual amounts and are shown in the table for mass balance. One of the constituents present in TOS is a high amount of water (Block 3, 25-45 %w/w) which has not been considered in the CSA. Similarly, Block 12 contains about 3-20 %w/w of high molecular weight compounds such as lignin, cellulose and fibres. The constituents in Block 12 are also not assessed because they are not expected to be bioavailable.

For the purposes of identifying constituent blocks and assessing the environmental hazard and fate properties of those blocks, it is necessary to consider certain physicochemical properties of the individual constituents of TOS, namely vapour pressure, water solubility, n-octanol/water partition coefficient (log K_ow) and Henry’s Law constant (HLC).

The resultant physicochemical properties for each block are also shown in Table 1.4.2, while the predicted physicochemical values for each constituent are in Table 1.4.4. Biodegradation and ecotoxicity properties are covered in IUCLID Sections 5 and 6 respectively and CSR Sections 4 and 7 respectively.

Acid Dissociation constant (pKa)

Dissociation constant is important for ionisable organic substances, since it indicates which chemical species will be present at a particular pH (e.g. in fresh or marine waters, or in the gut). The dissociation of a substance may affect its fate and behaviour (e.g. bioconcentration and adsorption to soil/sediment). It is also important information for the interpretation of ecotoxicity and mammalian toxicokinetic data. For the latter, dissociation constant indicates the potential for absorption from the gastrointestinal tract and dermal absorption (certain ionic compounds are not absorbed dermally).

The acid dissociation constants (pKa) of the ionisable constituents of TOS were obtained by prediction based on the use of SPARC software online calculator (version 4.5, September 2009). This uses a method based on linear free energy relationships and molecular orbital properties, and is the method recommended by ECHA (2008). The fatty acids and rosin acids have pKa values in the range 4.6 - 4.8.

Some of the neutral constituents, for example alcohols/sterols are extremely weak acids and only dissociate under strongly basic conditions (pH >16 approximately). The alcohols/sterols present in TOS have pKa in the range 15.5 - 17.6. Therefore, in the range of pH usually considered relevant to the human body and environment, i.e. pH 2-9, the neutral constituents present in TOS will not be ionised.

n-Octanol/water partition coefficients

TOS is a UVCB substance with variable constituents, it is therefore not considered realistic to use measurement for the determination of the log K_ow values of the constituents. In the context of risk or exposure assessment, an understanding of the n-octanol/water partition coefficient of the substance is obtained from the individual predicted log K_ow values of the constituents. Predicted log K_ow values were obtained using KOWWIN v.1.67 (part of Syracuse Research Corporation EPIWIN Suite of programs).

For the fatty acids and rosin acids, the log K_ow values were assessed on the basis of the log K_ow of the carboxylate anions. This is because they are expected to dissociate at relevant environmental pH. The log K_ow of the acidic constituents were corrected using the equation at pH 7; CORR = 1/1 +10^A(pH-pKa) [where A = 1 for acids, -1 for bases; pH = pH-value of the environment; pKa = acid/base dissociation constant]. The corrected log K_ow are approximately 2.25 log units lower than those of the non-dissociated forms. The corrected log K_ow values are used for the CSA.

There are several neutral constituents present in TOS. Neutral constituents in TOS are hydrocarbons, alcohols, aldehydes and steroidal compounds. However, limited measured partition coefficient data are available for these groups of constituents. Predicted log K_ow values were determined using KOWWIN. The general trends in the data show properties that vary with carbon chain length in accordance with normal expectations. The n-octanol/water partition coefficient increases with increasing carbon chain length, up to a limiting value.

The predicted log K_ow of the constituents was used to determine the weighted average for the blocks.

Water solubility

Predicted water solubility values were obtained for the constituents of TOS using WSKOWWIN v.1.41 (part of Syracuse Research Corporation EPIWIN Suite of programs).

The general trends in the data show properties that vary with carbon chain length, in accordance with normal expectations. Water solubility decreases with increasing carbon chain length.

The predicted water solubility of the constituents was used to determine the weighted average for the blocks.

Vapour pressure

The vapour pressures of individual constituents of TOS were predicted using MPBPVPWIN v 1.43 (part of Syracuse Research Corporation EPIWIN Suite of programs). The vapour pressures of the constituents of TOS are, with the exception of volatiles such as terpenes, so low that the regression of measured and predicted values show poor correlation. The very low predicted vapour pressure values are considered not significant to the CSA.

The predicted values for most of the constituents were low, which indicates low potential to vaporise.

The weighted average was determined for the blocks based on the predicted vapour pressure for the constituents.

Henry’s Law Constant (HLC)

HLC Values were calculated from the other physicochemical properties using the expression:

HLC (Pa.m³/mol) = [VP (Pa) x MW (g/mol)] ÷ [WS (mg/l)]

Where

VP = vapour pressure;

MW = molecular weight;

WS = water solubility

The weighted averages for the constituents were determined from the calculated HLC values for individual constituents of TOS.

 

Table 1.4.2: Physicochemical properties of constituent blocks for TOS

Block No/Name	Mean (%w/w)	Mol. wt (g/mol)	Vapour pressure (Pa) at 25°C	log Kow	Water solubility (mg/L) at 20°C	HLC ((Pa.m^3/mol)) at 25°C	pKa
BLOCK 1: Sodium salts of saturated and unsaturated C14-C20 fatty acids	27.0	283.09	2.8E-3	5.2	0.88	12.2	4.7
BLOCK 2: Rosin Acid Sodium Salts	24.0	302.18	2.7E-5	3.7	3.2	3.8E-3	4.7
BLOCK 3: Water	32.3	18.02	N/A	N/A	N/A	N/A	N/A
BLOCK 4: Terpenes	<0.1	136.23	5.4E+2	4.3	5.7	1.8E+4	-
BLOCK 5: Sesquiterpenes	0.1	204.36	4.8	6.3	0.05	1.8E+4	-
BLOCK 6: Abietenes and labdanes	0.8	274.49	4.5E-2	8.0	9.7E-4	5.9E+4	-
BLOCK 7: C30 Branched alkenes	0.2	410.72	8.2E-5	10.0	2.2E-6	9.4E+7	-
BLOCK 8: 3,5-Dimethoxystilbene	0.1	240.30	3.2E-3	4.7	2.7	3.9E-1	-
BLOCK 9: Rosin Alcohol and aldehydes isomers	1.4	287.08	9.8E-4	6.2	7.2E-2	5.3	15.6
BLOCK 10: C20-C35 alcohols and terpene alcohols.	0.8	347.63	3.2E-5	9.0	6.2E-5	17.7	15.7
BLOCK 11: Sterols	3.7	421.29	2.5E-8	9.4	1.1E-4	0.42	16.3
BLOCK 12:Lignin, cellulose fibre and oligomeric acids*	9.6	>1000	N/A	N/A	N/A	N/A	N/A

N/A = Not assessed

-No ionising groups

 

Identification of ‘Blocks’ present in TOS

Background

For the purposes of environmental exposure assessment and risk characterisation, it is necessary to consider the properties of the constituents, rather than the whole substance. Given the large number of constituents, however, it is not practicable to perform a separate environmental risk characterisation for each one. An approach known as ‘blocking’ is therefore used based on the methodology set out for petroleum-based substances in the EU Risk Assessment (ECB TGD Part II).

The EU TGD (EC, 2003) refers to blocks based on physicochemical, degradation and toxicological properties alone; however, analytical techniques have advanced and the compositional description of multi-constituent oil products is far more detailed than was envisaged when the TGD was written. Therefore, blocks based on composition are preferred here, since it is much easier to manipulate the data and interpret the results.

Separate exposure and hazard assessments can thus be determined for each block and the sum of their RCR (risk characterisation ratio) determined for the whole turpentine substance. The approach for simplifying the description of the substance by the use of blocks is consistent with REACH guidance.

TOS Blocks

TOS is a UVCB substance that is made up of sodium salts of fatty acids, sodium salts of rosin acids and other constituents such as alcohols, aldehydes and sterols etc. The molecular weights of the constituents range from 18.02 to 631.09 g/mol, excluding lignin, oligomeric compounds (>1000 g/mol, block 12).

The constituents of TOS were assigned into Blocks based on their chemical structure; sodium salts of fatty acids and sodium salts of rosin acids were assigned into one block each. Water and terpenes that are the volatile constituents present in TOS were assigned into different Blocks due to differences in their properties. The neutral constituents, for example sesquiterpenes, alkenes, alcohols, sterols and lignin/cellulose are all assigned into individual blocks as shown in Table 1.4.3.

Sitosterol and its analogues (sterols) were grouped into a block based on their similar properties.

It is relevant to note that:

- Fatty acids from C6 to C24 and their potassium, sodium, calcium and magnesium salts are exempt from REACH Registration under Annex IV.

- Sterols such as sitosterols have been assessed by EFSA for food use.

- Oligomeric acids, lignins and cellulose have not been assessed because they are high molecular weight compounds that are not expected to be bioavailable.

- Sodium is a ubiquitous substance in nature which is an essential nutrient and subject to biological activity and control. It is the sixth most abundant element on Earth and it is distributed widely in soil, plants, food and water. It is a normal component of the body. Sodium is therefore not expected to be toxic in the environment and is therefore not included as part of this chemical safety assessment.

The resultant blocks and percentage abundance of each constituent are shown in Table 1.4.3. Overall, twelve (12) blocks were identified in TOS. The constituents are all quantified, so blocks can be based on a weighted average of properties of the individual constituents within the block.

Table 1.4.3: TOS Block Summary

Block No/Name	Mean (%w/w)
BLOCK 1: Sodium salts of saturated and unsaturated C14-C20 fatty acids	27.0
BLOCK 2: Rosin Acid Sodium Salts	24.0
BLOCK 3: Water	32.3
BLOCK 4: Terpenes	<0.1
BLOCK 5: Sesquiterpenes	0.1
BLOCK 6: Abietenes and labdanes	0.8
BLOCK 7: C30 Branched alkenes	0.2
BLOCK 8: 3,5-Dimethoxystilbene	0.1
BLOCK 9: Rosin Alcohol and aldehydes isomers	1.4
BLOCK 10: C20-C35 alcohols and terpene alcohols.	0.8
BLOCK 11: Sterols	3.7
BLOCK 12: Lignin, cellulose fibre and oligomeric acids*	9.6

 

Table 1.4.4: Predicted results for key physicochemical properties of constituents of TOS

Block No/Constituent name	Mean (%w/w)	Mol. Wt (g/mol)	Vapour Pressure (Pa) at 25°C	corrected log Kow	corrected log Kow limited to 10	Water solubility (mg/L) at 20°C	pKa	HLC (Pa.m^3/mol)
BLOCK 1: Sodium salts of saturated and unsaturated C14-C20 fatty acids
Sodium salts of C10-C14 saturated and unsaturated fatty acids. Example Sodium myristate, C14:0-OONa EC No 212-487-9, CAS# 822-12-8	0.2	228.38	2.8E-02	3.9	3.9	15.8	4.8	4.1E-01
Sodium salts of C16:0 saturated fatty acids. Example Palmitic acid, sodium salt CAS#: 408-35-5	1.6	256.43	5.4E-03	4.9	4.9	1.4	4.8	9.9E-01
Sodium salts of C16:1 unsaturated fatty acids. Example Sodium palmitoleate EC No 229-562-7, CAS# 6610-24-8	0	254.42	6.2E-03	4.3	4.3	4.6	4.7	3.4E-01
Sodium salts of C17 saturated fatty acids. Example Sodium heptadecanoate; C17:0-OONa	0.5	270.46	2.6E-03	5.5	5.5	0.4	4.8	1.8E+00
Sodium salts of C17:1 unsaturated fatty acids. Example C17:1 fatty acid (8) Sodium (8Z)-heptadec-8-enoate	0	268.44	3.2E-04	4.9	4.9	1.3	4.8	6.5E-02
Sodium stearate	0.2	284.49	7.0E-04	6.0	6.0	0.12	4.8	1.7E+00
Sodium oleate	7.1	282.47	4.8E-03	5.4	5.4	0.4	4.7	3.4E+00
Sodium salts of C18 mono-unsaturated fatty acids. Example Sodium (9E)-octadec-9-enoate	0.4	282.47	4.8E-03	5.4	5.4	0.4	4.7	3.4E+00
Sodium linoleate	9.1	280.45	1.3E-03	4.8	4.8	1.3	4.7	2.7E-01
Sodium salts of C18 polyunsaturated fatty acids. Example C18:2-OONa isomers	6.2	294.48	4.4E-05	5.3	5.3	0.38	4.7	3.4E-02
Sodium salts of C20 saturated and unsaturated fatty acids. Example Sodium Eicosanate CAS#: 13257-34-6, EC No.: 236-248-3	0.6	312.54	1.6E-02	7.0	7.0	1.0E-02	4.8	4.8E+02
Sodium docosanoate	0	340.60	3.6E-05	8.1	8.1	8.6E-04	4.8	1.4E+01
Sodium Tricosylate	0	354.62	2.2E-06	8.6	8.6	2.5E-04	4.8	3.1E+00
Sodium Tetracosanoate	0	368.65	8.6E-06	9.2	9.2	7.3E-05	4.8	4.4E+01
Block 1 total abundance	25.9
BLOCK 2: Rosin Acid Sodium Salts
Sodium Abietate	9.8	302.46	2.6E-05	3.7	3.7	3.1	4.8	2.6E-03
Sodium dehydroabietate	3.2	300.44	2.3E-05	3.4	3.4	5.6	4.8	1.2E-03
Sodium Isopimarate	1.6	302.46	4.7E-05	3.7	3.7	2.9	4.8	4.9E-03
Sodium Neobietate	2.2	302.46	3.3E-05	3.7	3.7	2.9	4.6	3.4E-03
Sodium Palustrate	2.4	302.46	2.9E-05	4.5	4.5	0.56	4.7	1.6E-02
Sodium Pimarate	2	302.46	9.8E-06	3.5	3.5	4.0	4.6	7.5E-04
Rosin acid sodium salt. Example Geometric isomers of Abietic acid sodium salts	2.1	302.46	2.6E-05	3.7	3.7	3.1	4.8	2.6E-03
Block 2 total abundance	23.3
BLOCK 3: Water
Water	32.3	18.02	N/A	N/A	N/A	N/A	N/A	N/A
Block 3 total abundance	32.3
BLOCK 4: Bicyclic terpenes
Bicyclic terpenes example alpha pinene	0.06	136.23	5.4E+02	4.3	4.3	5.7	-	1.8E+04
Block 4 total abundance	0.06
BLOCK 5: Sesquiterpenes
Sesquiterpenes. Example gamma Muurolene	0.1	204.36	4.8E+00	6.3	6.3	5.0E-02	-	1.8E+04
Block 5 total abundance	0.1
BLOCK 6: Abietenes and Labdanes
Abietenes	0.2	272.47	2.7E-02	7.7	7.7	1.4E-03	-	6.4E+03
Decarboxylated Rosin. Example Dehydroabietine	0	256.43	1.1E-02	7.3	7.3	1.3E-02	-	2.7E+02
Steradienes. Example Stigmasta-3,5-diene	0	396.69	3.5E-05	11.0	10.00	2.7E-06	-	5.9E+04
Labdanes. Example labdane	0.1	278.52	8.3E-02	8.7	8.7	1.6E-04	-	1.6E+05
Block 6 total abundance	0.3
BLOCK 7: C30 branched polyalkenes
Squalene	0.2	410.72	8.2E-05	14.1	10.0	2.2E-06	-	9.4E+07
Block 7 total abundance	0.2
BLOCK 8: 3,5-Dimethoxystilbene
3,5-Dimethoxystilbene	0.1	240.3	3.2E-03	4.7	4.7	2.7	-	3.9E-01
Block 8 total abundance	0.1
BLOCK 9: Rosin Alcohol and aldehydes isomers
Rosin Aldehyde isomers. Example Abieta-7,13-dien-18-al	0.9	286.46	1.4E-03	6.2	6.2	7.3E-02	15.6	7.6E+00
Dehydroabietal	0	284.45	7.1E-04	6.3	6.3	6.7E-02	15.6	4.3E+00
Agatholal	0	304.47	1.6E-06	5.7	5.7	5.2E-01	15.6	1.6E-03
Neoabietal	0	286.46	8.7E-04	6.3	6.3	5.7E-02	15.5	6.2E+00
Isopimaral	0	286.46	1.6E-03	6.2	6.2	7.6E-02	15.6	8.4E+00
Pimaral	0	286.46	1.6E-03	6.2	6.2	7.6E-02	15.6	8.4E+00
Rosin Alcohol isomers. Example Abietol	0.4	288.47	1.5E-05	6.2	6.2	6.8E-02	15.6	2.9E-02
Agathadiol	0	306.49	1.8E-07	6.1	6.1	6.6E-02	15.5	1.5E-03
Isopimarinol	0	288.48	1.8E-05	6.2	6.2	7.0E-02	15.6	3.4E-02
Neoabietol	0	288.48	9.9E-06	6.4	6.4	5.3E-02	15.5	2.6E-02
Palustrol	0	222.37	1.5E-02	4.6	4.6	3.7E+00	15.6	3.0E-01
Pimarol	0	288.48	1.8E-05	6.2	6.2	7.0E-02	15.6	1.2E-01
Block 9 total abundance	1.3
BLOCK 10: C20-C35 saturated/unsaturated alcohols and terpene alcohols
Mono-terpene alcohols	0	154.25	2.9E+00	3.3	3.3	3.4E+02	0	1.1E+00
C20-C26 saturated alcohols. Example Eicosanol	0.6	298.55	4.2E-05	8.7	8.7	8.1E-05	15.6	1.3E+01
Docosanol	0	326.61	4.7E-06	9.7	9.7	4.8E-06	15.6	1.8E+01
Tricosanol	0	340.63	4.9E-07	10.2	10.0	6.6E-05	15.6	6.4E+00
Tetracosanol	0	354.67	8.2E-07	10.7	10.0	5.4E-05	15.8	3.7E+01
Hexacosanol	0	382.71	1.5E-07	11.7	10.0	3.7E-05	15.6	7.7E+01
Betulaprenol 6 C30:6-(trans)-OH	0	426.73	2.2E-09	12.7	10.0	1.9E-05	0	1.7E+01
Betulaprenol 7 C35:7-(trans)-OH	0.2	494.85	1.4E-11	15.0	10.0	7.2E-06	15.7	3.1E+01
Betulaprenol 8 C40:8-(trans)-OH	0	562.97	7.5E-14	17.3	10.0	2.6E-06	15.7	5.0E+01
Betulaprenol 9 C45:9-(trans)-OH	0	631.09	3.8E-16	19.6	10.0	9.4E-07	0	7.3E+01
Block 10 total abundance	0.8
BLOCK 11: Sterols
Campesterol	0.3	400.68	4.5E-08	9.2	9.2	1.5E-04	15.6	2.3E-01
Campestanol	0.1	402.71	5.2E-08	9.2	9.2	1.2E-04	17.6	3.2E-01
β-Sitosterol	2.0	414.72	2.6E-08	9.7	9.7	4.6E-05	15.6	4.5E-01
Sitostanol isomers. Example Sitostanol	0.4	416.73	3.7E-08	9.7	9.7	3.8E-05	17.6	7.8E-01
Lupeol	0	426.73	3.5E-09	9.2	9.2	8.8E-05	17.6	3.3E-02
Cycloartenol	0	426.73	6.5E-09	9.9	9.9	2.3E-05	17.6	2.3E-01
Citrostadienol	0	426.73	3.8E-09	10.0	10.0	2.0E-05	17.6	1.6E-01
24-methylenecycloartanol	0.2	440.76	6.4E-09	10.4	10.0	1.6E-05	17.6	7.7E-01
Betulin	0.2	442.72	2.1E-11	8.2	8.2	5.6E-04	17.6	1.1E-04
Rosin esters example Methyl Betulinate	0.3	470.74	3.1E-10	8.3	8.3	3.0E-04	17.6	9.6E-04
Block 11 total abundance	3.5
BLOCK 12: Cellulose fibre, lignin and oligomeric acids
Lignin (non-eluting neutral)	2.3
Cellulose fibre	6.2
Oligomeric esters (Higher boiling point neutrals)	1.1	>1000
Block 12 total abundance	9.6

 

 

Additional information

Chemistry/Structural discussion of the constituents of TOS

TOS is a UVCB substance containing sodium salts of fatty acids, sodium salts of rosin acids, water, terpenes, alcohols, aldehydes, sterols and high molecular weight compounds such as lignin and cellulose. The chemistry of the constituents are briefly discussed below.

Fatty acids:

The fatty acids present in TOS are in the form of their sodium salts. The long-chain fatty acids (LCAF) present in TOS are carboxylic acids with a long aliphatic C13-C24 chain either saturated or unsaturated. In TOS, these are predominately unsaturated fatty acids. Fatty acids in plants and organisms are normally in the form of triglycerides, phospholipids, and cholesterol esters. They are important structural components for cells.

- Fatty acids are slightly acidic at pH 5 to 6

- Saponification is the neutralisation of fatty acids

- Unsaturated fatty acids are susceptible to degradation by ozone. This can be used in the production of azelaic acid [(CH₂)₇(COOH)₂] from oleic acid

- Unsaturated fatty acids undergo auto-oxidation in the presence of oxygen (air) and accelerated by the presence of trace metals

- Fatty acids play a number of roles in metabolism, as an essential component of all membranes and as gene regulators.

- Short chain fatty acids are freely soluble (protonated and ionised form) in water. As the aliphatic chain length of fatty acids increases, the lipid-like properties begin to appear. As chain length increases e.g. to C12, the protonated fatty acids become less soluble

- At very high pH where the longer chained fatty acids are totally ionised, there is the possibility of micelle formation (small thermodynamically stable aggregates of molecules in aqueous solutions)

- At high pHs >9, fatty acids form soaps. Below the melting temperature of the hydrated, crystalline soaps, soap crystals will separate from an aqueous solution and be in equilibrium with a very low concentration of ionised soap molecules. At pH between 7 to 9, below the melting point, the system will be partly ionised and partly unionised to form 'acid soap' (Small 1992)

- Fatty acids are relatively hydrophilic as sodium salts

Rosin acids:

Rosin is a mixture of eight closely related rosin acids that are made up of three fused six-carbon rings containing double bonds which vary in number and location with a single carboxylic acid group. They have the empirical formula C₁₉H₂₉COOH. Rosin, unlike hydrocarbon resins, is not a polymer. It is a blend of distinct molecules. Rosin is a mixture of eight closely related rosin acids characterised by three fused six-carbon rings, double bonds that vary in number and location and a single carboxylic acid. The ratio of these isomers in rosin depends on the collection method and the species of the tree from which the rosin was harvested. The molecular weight of rosin is quite different compared to hydrocarbon resins.

Rosin acids are tacky, yellowish gums that are water-insoluble, freely soluble in alcohol, benzene, ether, has low vapour pressure. They are used to produce soaps. Rosin acids are protectants and wood preservatives that are produced by parenchymatous epithelial cells that surround the resin ducts in trees from temperate coniferous forests.

Terpenes:

Terpenes are a large class of natural hydrocarbon secondary metabolites that are built up from five-carbon isoprene units; linked together most commonly in a head-to-tail arrangement but can be constructed in other configurations with varying degrees of unsaturation, oxidation, functional groups and ring closures.

The term terpenes refer to compounds that are isolated from turpentine (a volatile liquid that is isolated from pine trees) Yadav et al (2014) [Nita Yadav, Rajesh Yadav, Anju Goyal (2014). Chemistry of Terpenoids. Int. J. Pharm. Sci. Rev. Res., 27(2), July – August 2014; Article No. 45, Pages: 272 – 278]. Mono and sesquiterpenes are the chief constituent of the essential oils that are obtained from the sap and tissues of plants and trees. Terpene was originally used to describe the mixture of isomeric hydrocarbons of the molecular formula C₁₀H₁₆ that occurred in essential oils which are obtained from sap, plant tissue and trees. Due to the varied nature of the terpenes, the term terpenoid (includes hydrocarbons and their oxygenated derivatives) will be used.

Terpenoids are the hydrocarbons of plant origin with the general formula (C₅H₈)_n including their oxygenated, halogenated and dehydrogenated derivatives. They are volatile substances.

The majority of natural terpenoid hydrocarbons have the general formula (C₅H₈)_n. Thus, terpenoids can be classified on the number of carbon atoms (n) that are present in the structure based on the number of isoprene units present in the structure; example monoterpenes, diterpenes, sesquiterpenes etc.

The terpenoids have the following general properties:

- most terpenoids are colourless, fragrant liquids but few are solids that are lighter than water, volatile with steam

- soluble in organic solvents, usually insoluble in water; monoterpenoids are slightly soluble in water

- undergo polymerisation and dehydrogenation

- undergo easy oxidation and most produce isoprene unit as product of thermal decomposition

- are open chain or cyclic unsaturated compounds with one or more double bonds. Hence, they undergo addition reaction with acids, halogen and hydrogen.

 

Sesquiterpenes:

Sesquiterpenes are acyclic unsaturated hydrocarbons and normally have a molecular formula of C₁₅H₂₄. Biochemical modifications such as oxidation or rearrangement produce the related sesquiterpenoids.

- sesquiterpenes are less volatile and have higher boiling point than terpenes

- over time, sesquiterpenes undergo oxidation to form sesquiterpenols

Abietenes and labdanes:

Abietenes are tricyclic unsaturated compounds. It is a diterpene which are the basis for a variety of natural chemical compounds, for example abietic acid. Labdanes are bicyclic unsaturated diterpenes.

Squalene:

Squalene is an unsaturated branched chain hydrocarbon. It is present from plant sources (primarily vegetable oils) and synthetically from genetically engineered yeast cells. It is a biochemical precursor/intermediate for synthesis of all plant and animal sterols e.g. cholesterol and steroid hormones in the human body. It has a density of 0.855 g/ml.

C20-C26 saturated alcohols:

Long chain saturated alcohols, also known as fatty alcohols are usually high-molecular-weight, straight-chain primary alcohols in the range of C20–C26 normally with an even number of carbons and a single terminal alcohol group (–OH). They are colourless waxy solids, may be unsaturated and branched.

 

Fatty alcohols are used to produce detergents and surfactants. They are components also of cosmetics, foods, and as industrial solvents. Due to their amphipathic nature, fatty alcohols behave as non-ionic surfactants. They find use as co-emulsifiers, emollients and thickeners in cosmetics and food industry. Very long-chain fatty alcohols (VLCFA) of C24 to C32 obtained from plant waxes and beeswax have been reported to lower plasma cholesterol in humans. In general, for alcohols, properties are expected to vary with the carbon chain length.

In general, for alcohols

- boiling point increases with increasing carbon atoms

- vapour pressure decreases as the carbon atoms increase

- water solubility decreases with increasing carbon atoms

- log K_ow increases as the carbon atoms increases up to a limit value

Sterols:

Sterols, also known as steroid alcohols, are a subgroup of the steroids with a hydroxyl group at the 3-position of the A-ring. The hydroxyl group on the ring is polar and the rest of the aliphatic chain is non-polar. Plant sterols (unsaturated) and stanols (saturated) are naturally found in plants sources e.g. vegetable oils and are structurally similar to cholesterol. Cholesterol is considered to be the predominant sterol in animals including humans, a variety of sterols are found in plants called phytosterols. Sterols structures are based on the tetracyclic ring system (three cyclohexane ring and one cyclopentane ring). Cholesterol is biosynthesized from the triterpene squalene.

Types of phytosterols

Phytosterols are classed into two, (i) sterols which have double bond in the sterol ring, hence are unsaturated compound. Example of sterols found in CTO/TOS are sitosterol, stigmasterol and campesterol. (ii) Stanols which lack double bond in the sterol ring, hence are saturated compound, examples are sitostanol and campestanol. The hydrogenation of phytosterols form the corresponding stanols.

 

- most are optically active solid with high melting point

- they are insoluble in water but soluble in non-polar solvents such as hexane, 2-propanol

- they are hydrophobic with high log K_ow

- they have very low vapour pressure

Plant sterols or stanols are approved for use in lowering cholesterol level in blood in the EU and in a number of countries worldwide (nutritional supplement), example, see Commission Regulation (EU) No 686/2014

of 20 June 2014 amending Regulations (EC) No 983/2009 and (EU) No 384/2010 as regards the conditions of use of certain health claims related to the lowering effect of plant sterols and plant stanols on blood LDL-cholesterol. Official Journal of the European Union L 182/27, Document 32014R0686, dated 21 June 2014 http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv:OJ.L_.2014.182.01.0027.01.ENG

Cellulose fibre, lignin and oligomeric acids:

Lignin (non-eluting neutral) [9005-53-2]

Lignin is complex cross-linked phenolic polymer of over 10,000 g/mol. These form key structural materials in the support tissues of vascular plants and some algae. The composition of lignin varies from species to species. For example, aspen has 63.4% carbon, 5.9% hydrogen, 0.7% ash (mineral components), and 30% oxygen (by difference). This corresponds to approximately to the formula (C₃₁H₃₄O₁₁)_n.

Lignin is a fibrous, tasteless material, insoluble in water and alcohol but soluble in slightly alkaline solutions and can be precipitated from solution using acid. Also soluble in most organic solvents (e.g. diethyl-ether).

Cellulose fibre

Cellulose and fibre are insoluble residues from the pulping process.

Oligomeric esters (Higher boiling point neutrals)

Oligomeric esters are esters of rosin acids and fatty alcohols or rosin acids and fatty alcohols so have molecular weights in excess of 1000 g/mol.

Justification for read-across

The registration substance, TOS is a UVCB substance obtained from naturally-occurring compounds which is extracted from wood chips during the Kraft Pulping of wood.

The submission includes use of QSAR and read-across with exact details depending on the endpoint, fo example, environmental fate, ecotoxicology and toxicology.

Measured properties for the registration substance are used where available and valid. Where there are data gaps, these may be filled using read-across from measured data for: 

- For the constituents of TOS including rosin, fatty acids, sterols

- Crude Tall Oil (CTO), a structural analogue of TOS

Where relevant data are available for the constituents; these are used in addition to available data for the whole substance. The substances used for read-across for the registered substance are discussed below.

Crude Tall Oil (CTO):

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.

Crude Tall Oil (CTO) is formed by acidification of Tall Oil Soap (TOS), therefore, CTO and TOS are similar UVCB substances. They differ only in the water content and that CTO does not contain sodium salts of the fatty/rosin acids.

The main constituent blocks for TOS are the sodium salts of saturated and unsaturated C14-C20 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 polyalkenes, 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 but in similar proportions

Fatty acid salts:

Fatty acid salts category is defined as the salts of monocarboxylic acids that contain straight, even-numbered fatty acid chains. The carbon number ranges from 10 to 22, with the C16 to C22 being saturated or unsaturated (HERA 2003).

TOS contained straight-chained even-numbered sodium salts of fatty acids; with carbon number ranging from C16 to C24. Data are available for substances within this category that are also constituents of Block 1 of TOS. The read across is based on a direct comparison of the constituent and carbon chain length distribution of the read-across substance to the target or submission substance (TOS) and is discussed further in the relevant sections of the dossier. In the environment, fatty acid salts are expected to dissociate forming carboxylate anions and the corresponding cations.

Rosin (CAS 8050-09-7):

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 depending on the source of the rosin. TOS is the precursor substance from which CTO is produced. Tall oil rosin (CAS 8052-10-6) is one of the products of fractional distillation of CTO. Gum rosin is the oleoresin (pine gum) of the living pine tree and wood rosin is the acid extracted from pine stump.

Sust Forest (2012) reported percentage range of rosin acids in various sources of rosins as shown in the table below.

Table 1.6.1: Sources of rosin and percentage abundance

Rosin acid (% of acid fraction)	Gum rosin	Tall oil rosin	Wood rosin
Abietic	32 – 37	40 – 45	25 – 35
Palustric/levopimaric	18 – 23	5 – 10	5 – 10
Neoabietic	15 – 20	1 – 6	5 – 15
Dehydroabietic	8 – 10	27 – 32	20 – 25
Pimaric	7 – 12	5 – 10	3 – 5
Isopimaric	6 – 11	4 – 9	2 – 6
Sandaracopimaric	1 – 3	<2	1 – 3

 

The compositional comparison of constituents of rosin (test material) and TOS (target substance) are shown in the table below. The percentage abundance of rosin reported in the table was obtained from the available measured ready biodegradation study for gum rosin.

Table 1.6.2: Compositional comparisons between TOS and gum rosin

Constituent	Percentage (%) w/w of gum rosin constituents presented in ready biodegradation study	Percentage (%) w/w of TOS (% w/w)*
Pimaric acid	7.3	2.0
Sandaracopimaric acid	1.5	-
Palustric acid	17.9	2.4
Levopimaric acid	0.7	-
Isopimaric acid	3.4	1.6
Abietic acid	44.5	9.8
Dehydroabietic	2.9	3.2
Neoabietic acid	15.8	2.2
Sesquiterpenes	4.4	0.1
Unknown	1.6	2.1

*the rosin acids are presented as the sodium salt

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 (McSweeneyet 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 ubiquitous and essential element in nature, is not expected to contribute to the toxicity properties of the registered substance. Therefore, available measured data for rosins are read-across where valid to fulfil information requirements of Blocks 2 of TOS.

Plant sterols (CAS No: 949109-75 -5, List no: 619-079-3):

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 (e.g. soyabean and corn oil) (British Dietetic Association Food Fact Sheet 2012.www.bda.uk.com/foodfacts).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, sitostanol and 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) where relevant due to compositional similarity.

The table below present the constituents present in plant sterols. The main constituent of Block 11 (β–sitosterol) is also the main constituent of Plant sterols. Block 11 and Plant sterols also have several other constituents in common (campesterol, sitostanol and campestanol). The remaining constituents of Block 11 are structurally similar to the constituents of Plant sterols.

Table 1.6.3: Compositional comparisons between TOS and plant sterols

Constituent	Percentage (%) w/w of plant sterols constituents presented in ready biodegradation study	Percentage (%) w/w of TOS (typical % w/w of Block 11)
β-Sitosterol	30-80	2.0 (57%)
Campesterol	≤45	0.3 (9%)
Stigmasterol	≤30	-
Brassicasterol	≤20	-
Sitostanol	≤15	0.4 (11%)
Campestanol	≤2	0.1 (3%)

 

References:

McSweeney E.E, Herbert G, Russell J (1987). Tall Oil and its uses – II, Pulp Chemicals Association, Inc. Atlanta, GA, 1987.

Sust Forest (2012) Atelier International De Diagnostique De L’Idustrie Des Resineus de Seconde Transformation “La Colophane et Son Avenir Dans Domaine Du Sudoe” Bordeaux France

Small Donald M (1992). Physical properties of Fatty Acids and their Extracellular and Intracellular Distribution. Polyunsaturated Fatty Acids in Human Nutrition, edited by Bracco and R. J. Deckelbaum. Nestlé Nutrition Workshop Series, Vol. 28, Nestec Ltd., Vevey/Raven Press. Ltd. New York 1992.