Registration Dossier

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

Physicochemical properties

Introduction

TOPP 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

Physical appearance

The substance has been reported as colourless, amber or yellow liquid at standard temperature and pressure. TOPP 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

A freezing point of -60 to -50°C was reported for TOPP in a publicly obtained data source. A full detail on the test method is not available, however the result is considered adequate for assessment purpose.

Boiling point

A boiling point of 154 to 170°C was reported for TOPP in a peer reviewed public domain source. The result is considered adequate for assessment purpose.

Relative density

Relative density values of 0.864 and 0.860 at 25°C has been determined for the test substance using an appropriate test method. A value of 0.85 to 0.87 g/cm3 at 25°C was also reported in O’Neil 2006.

Vapour pressure

TOPP is a UVCB substance with varied composition. The vapour pressure of individual constituents of TOPP was determined to be 5.7E-02 to 2.0E+05 Pa at 25°C using a validated QSAR estimation method. A vapour pressure of 2600 Pa at 25°C was obtained for the substance. TOPP is a volatile substance. The vapour pressures of constituents blocks range from 3.9 Pa to 2.0E+05 Pa at 25°C.

Surface tension

An aqueous solution surface tension value of 54.8 mN/m at 20°C has been determined for TOPP in a GLP study according to OECD Test Guideline 115. TOPP is considered weakly surface active.

Water solubility

Water solubility has been determined in a GLP study for the test substance using a method in accordance to OECD Test Guideline 105. TOPP has a water solubility value of 0.351 g/L at 20°C at 10 g/l loading rate and pH 6.4 – 6.5. The water solubility of the constituents of TOPP was determined to be 4.8E-02 to 2.9E+04 mg/l using validated a QSAR estimation method. The water solubilities of constituent blocks ranges from 1.9 mg/l to 2.9E+04 mg/l at 25°C.

Partition coefficient

log Kow of 0.8 to 6.3 was determined for constituents of TOPP using a validated QSAR estimation method. For environmental risk assessment, the properties of the substance are assessed using the ‘block approach’. The log Kow of each block has been determined based on the weighted average of each constituent in the block. Predicted log Kow in the range of 0.8 to 6.3 was determined for all ‘blocks’ in TOPP.

Viscosity

Viscosity values of 2.03548 cP at 50°F, 1.3035 cP at 100°F and 0.93535 cP at 150°F have been determined for TOPP using an appropriate test method.

Flash point

There are several flash point data available for TOPP. Flash point values of 5°C, 26°C and 37°C have been determined for the test substance using a closed cup method according to an appropriate Test Guideline. Flash point values below 5°C could be obtained for some samples of the substance. TOPP is a UVCB substance and the variations in the results could be due to the nature or composition of the samples tested.

Flammability

The substance is classified as flammable/highly flammable liquid on the basis of a flash point of 5 -37°C. The substance is unlikely to have pyrophoric properties or liberate flammable gases in contact with water. A lower explosion limit of approximately 0.8% (volume) and an upper explosion limit of approximately 6% (volume) at 101.3 kPa was reported for the substance in a peer-reviewed source (Elvers B, Hawkins S (1996)).

Auto-ignition temperature

TOPP has an auto-ignition temperature of 270°C at 99.44 to 99.85 kPa, using a method according to E.U Method A.15 and in compliance with GLP. Auto-ignition is therefore unlikely to present a hazard for TOPP.

Oxidising properties

TOPP is not considered to be oxidising.

Explosive properties

TOPP is not explosive.

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. Residual amounts of unresolved TOPP constituents have been identified and are shown in the table for mass balance. Although, it has not been possible to allocate chemical structures to these constituents; due to the nature of the substance; it is expected that any ‘unknown’ present in TOPP will have similar properties to those of the identified constituents since the constituents are often related due to the plant’s biochemistry.

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 TOPP, namely vapour pressure, water solubility, n-octanol/water partition coefficient (log Kow) 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 Sections 5 and 6 respectively.

n-Octanol/water partition coefficients

No measured partition coefficient data are available for TOPP. TOPP is a UVCB substance with variable constituents, it is therefore not considered realistic to use measurement for the determination of the log Kow values. 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 Kow values of the constituents. Predicted log Kow values were obtained using KOWWIN v.1.67 (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. The n-octanol/water partition coefficient increases with increasing carbon chain length, up to a limiting value.

The predicted log Kow 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 TOPP 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 determination

Vapour pressure data for whole substance and individual constituents are determined for the purpose of environmental and human health risk assessment.

Vapour pressure of constituents

The vapour pressures of individual constituents of TOPP were predicted using MPBPVPWIN v 1.43 (part of Syracuse Research Corporation EPIWIN Suite of programs).

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

Vapour pressure of whole substance

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 TOPP

           b = Total moles of TOPP constituents

           c = Vapour pressure of individual constituents

Using the above expression, an estimated total vapour pressure value of 2600 Pa was obtained for the substances as a whole by summation of the contributions of the constituents.

Henry’s Law Constant (HLC)

HLC Values was 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 value for individual constituents of TOPP.


 

Table 1.4.2: Physicochemical properties of constituent blocks for TOPP

Block number

Block name

Molecular weight (gmol-1)

Vapour pressure at 25°C (Pa)

log Kow

Water solubility at 25°C (mg/l)

HLC at 25°C

(Pa.m3/mol)

Percentage block in substance

1

Pinene

136.23

5.1E+02

4.3

5.7

1.2E+04

71.5

2

δ-3-carene

136.24

2.8E+02

4.4

2.9

1.3E+04

13

3

Dipentene

136.24

2.1E+02

4.7

1.9

1.5E+04

7.8

4

Dimethyl sulfide

62.13

6.4E+04

0.9

2.3E+04

1.8E+02

1.2

5

Methyl mercaptan

48.10

2.0E+05

0.8

2.9E+04

3.4E+02

0.06

6

Sesquiterpenes

204.36

3.9E+00

6.3

5.0E-02

1.5E+04

4.30

7

Terpene alcohols

153.99

1.3E+01

3.0

6.1E+02

9.2

1.0

8

Camphene

136.24

2.4E+02

4.4

4.9

6.6E+03

0.81

9

Dimethyl disulfide

94.19

3.3E+03

1.9

3.1E+03

100

0.32

 

 


Identification of ‘Blocks’ present in TOPP

Background

Individual constituents of TOPP have specific and different physicochemical, environmental fate and toxicity properties. As a consequence, the concentrations of each constituent in an environmental compartment and its capacity to cause effects on the biota will be a unique function of its properties. However, for practical purposes it is possible to group or “block” constituents having similar physicochemical properties and environmental degradation potential and thereby simplify the assessment of a complex substance such as TOPP. The ability to establish “blocks” for TOPP makes it possible to determine the PEC (predicted environmental concentration) values for each block for each environmental compartment. In a similar way PNEC (predicted no effect concentration) values can be determined for the blocks and used in conjunction with the PEC values for risk characterisation.

For the purposes of environmental exposure assessment and risk characterisation, it is therefore 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.

TOPP Blocks

TOPP is primarily made up of monoterpenes, sesquiterpenes and terpene alcohols (hydrogenated and oxygenated terpenoids). The molecular weights of the monoterpenes constituents range from 134 – 136 g/mol, sesquiterpenes have an average molecular weight of 204 g/mol, and terpene alcohols have a molecular weight range of 148 – 154 g/mol. The molecular weight of sulfur compounds ranges from 48 – 94 g/mol.

The terpene constituents of TOPP were grouped into blocks based on an initial assessment of their structural similarity followed by a consideration of their log Kow and their PBT properties (Persistence, Bioaccumulation and Toxicity) including variation in their biodegradation potential.

The resultant blocks and percentage abundance of each constituent are shown in Table 1.4.3. 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: TOPP Block Summary

Block number

Block name

% TOPP Block*

1

Pinene Block

71.5

2

Delta-3-carene Block

13

3

Dipentene Block

7.8

4

Dimethyl sulfide Block

1.2

5

Methyl mercaptan Block

0.06

6

Sesquiterpes Block

4.3

7

Terpene alcohols Block

1.0

8

Camphene Block

0.81

9

Dimethyl disulfide Block

0.32

 *To take account of the unknown constituents in the CSA; the overall percentage concentration for the blocks excluding sulfur-containing compounds were scaled up to get the correct total concentration.

The constituents of TOPP have measured or predicted log Kowvalues in the range 0.8 to 6.3.

The sesquiterpenes constituents are predicted to be toxic (T).

Block 1 and Block 7 constituents are those terpenes and terpene alcohols which are not considered to be B or vB, with measured or predicted log Kow values below 4.5.

Block 2 and Block 3 constituents are those terpenes which are potentially bioaccumulative, with measured or predicted log Kow values above 4.5.

Block 4 and Block 5 constituents are the sulfides of sulfur and methyl mercaptan respectively which are not Bioaccumulative, with measured or predicted log Kow values below 4.5. Methyl mercaptan was placed in a separate block because of its high toxicity, while dimethyl sulfide and dimethyl disulfide were considered as a separate blocks based on the chemical properties of sulfides.

Block 6 constituents are the sesquiterpenes which are considered to be vB with predicted log Kow value greater than 4.5. Gamma murolene, alpha and delta cadinene were used as a representative sesquiterpenes that are present in TOPP. These constituents have an approximate log Kow of 6.3.

Camphene and dimethyl disulfides were placed in block 8 and block 9 respectively based on measured biodegradation data. Measured biodegradation results indicate that camphene is not biodegradable and dimethyl disulfide is inherently biodegradable.


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

Block number

Constituent

CAS number (where known)

SMILES

log Kow

Block weighted average log Kow

Water solubility (mg/l)

Block weighted average water solubility (mg/l)

Vapour pressure (Pa)

Block weighted average vapour pressure (Pa)

HLC (Pa.m3/mol)

Block weighted average HLC (Pa.m3/mol)

1

Alpha Pinene

80-56-8

C(C(CC1C2)C1(C)C)(=C2)C

4.3

4.3

 

5.7E+00

5.7E+00 

 

5.4E+02

5.1E+02 

 

1.3E+04

1.2E+04

1

α- Fenchene

471-84-1

C(CC1C2)C(C2=C)C1(C)C

4.4

4.9E+00

6.6E+02

1.9E+04

1

Tricyclene

508-32-7

C(C1(C(C2C3)(C)C)C)(C13)C2

4.1

7.5E+00

2.2E+02

4.1E+03

1

P-Cymene

99-87-6

Cc1ccc(C(C)C)cc1

4.0

3.4E+01

1.5E+02

6.0E+02

1

Beta Pinene

127-91-3

C(C(CC1C2)C1(C)C)(C2)=C

4.4

4.9E+00

3.3E+02

9.4E+03

2

Delta-3-Carene

13466-78-9

C(=CCC(C12)C1(C)C)(C2)C

4.6

4.6

2.9E+00

2.9E+00

2.8E+02

2.8E+02

1.3E+04

1.3E+04

3

Terpinolene

586-62-9

C(=C(C)C)(CCC(=C1)C)C1

4.9

4.7 

 

 

 

1.7E+00

1.9E+00 

 

 

1.3E+02

2.1E+02 

 

 

1.1E+04

1.5E+04

3

Myrcene

123-35-3

C(C=C)(=C)CCC=C(C)C

4.9

1.7E+00

3.2E+02

2.5E+04

3

Terpinene

8013-00-1

CC(C)C1=CC=C(C)CC1

4.8

2.2E+00

2.2E+02

1.4E+04

3

Iso-terpinolene

586-62-9

C(=C(C)C)(CCC(=C1)C)C1

4.9

1.7E+00

1.3E+02

1.1E+04

3

γ- Terpinene

99-85-4

C(=CCC(=C1)C)(C1)C(C)C

4.8

2.2E+00

1.5E+02

9.4E+03

3

Dipentene

7705-14-8

C(=CCC(C(=C)C)C1)(C1)C

4.8

1.9E+00

1.9E+02

1.4E+04

3

alpha-Phellandrene

99-83-2

C(C)(C)C1C=CC(C)=CC1

4.6

2.9E+00

2.6E+02

1.2E+04

3

β-Phellandrene

555-10-2

C(C=CC(C1)C(C)C)(C1)=C

4.7

2.4E+00

2.6E+02

1.5E+04

4

Dimethyl sulfide

75-18-3

S(C)C

0.9

0.9

2.2E+04

2.3E+04

6.4E+04

6.4E+04

1.8E+02

1.8E+02

5

Methyl mercaptan

74-93-1

SC

0.8

0.8

2.9E+04

2.9E+04

2.0E+05

2.0E+05

3.4E+02

3.4E+02

6

Sesquiterpenes (Gamma murolene)

30021-74-0

C(=C(CC1)C)C(C1=C(C2)C)C(C2)C(C)C

6.3

6.3 

 

5.3E-02

5.1E-02 

 

4.8E+00

3.9E+00 

 

1.9E+04

1.5E+04

6

Delta Cadinene

483-76-1

C(=C(CC1)C)C(C1=C(C2)C)C(C2)C(C)C

6.3

4.8E-02

2.5E+00

1.1E+04

6

alpha Cadinene

29350-73-0

CC(C)C1CC=C(C)C2CCC(C)CC12

6.3

5.3E-02

4.8E+00

1.9E+04

7

1,4-Cineole

470-67-7

O(C(CC1)(CC2)C(C)C)C12C

3.1

3.0

 

2.1E+02

6.1E+02 

 

2.4E+02

1.3E+01 

 

1.7E+02

9.2E+00

7

1,8-Cineole

470-82-6

O(C(CCC1C2)(C2)C)C1(C)C

3.1

3.3E+02

2.1E+02

9.7E+01

7

Fenchone

1195-79-5

O=C(C(CC1C2)(C2)C)C1(C)C

3.0

7.3E+01

9.6E+01

2.0E+02

7

Camphor

76-22-2

O=C(C(C(C1C2)(C)C)(C2)C)C1

3.0

1.9E+02

1.4E+00

1.2E+00

7

Terpinen-1-ol

586-82-3

OC(CC=C1C(C)C)(CC1)C

3.3

3.4E+02

4.8E+00

2.2E+00

7

Fenchol

512-13-0

OC(C(CC1C2)(C2)C)C1(C)C

2.9

4.6E+02

3.3E+00

1.1E+00

7

Terpinen-4-ol

562-74-3

OC(CCC(=C1)C)(C1)C(C)C

3.3

3.9E+02

5.7E+00

2.3E+00

7

beta-Terpineol

138-87-4

OC(CCC(C(=C)C)C1)(C1)C

3.4

2.9E+02

4.2E+00

2.2E+00

7

Methyl Chavicol

140-67-0

O(c(ccc(c1)CC=C)c1)C

3.5

8.4E+01

2.2E+01

3.9E+.1

7

Isoborneol

124-76-5

OC(C(C(C1C2)(C)C)(C2)C)C1

2.9

4.0E+02

5.7E-02

2.2E-02

7

alpha-Terpineol

98-55-5

OC(C(CCC(=C1)C)C1)(C)C

3.3

6.7E+02

2.6E+00

6.0E-01

7

Borneol

507-70-0

OC(C(C(C1C2)(C)C)(C2)C)C1

2.9

1.2E+03

5.7E-02

7.4E-03

7

cis-Anethole

104-46-1

O(c(ccc(c1)C=CC)c1)C

3.4

9.8E+01

8.5E+00

1.3E+01

7

trans-Anethole

4180-23-8

O(c(ccc(c1)C=CC)c1)C

3.4

9.8E+01

8.5E+00

1.3+01

8

Camphene

79-92-5

C(C(CC1C2)C2)(C1(C)C)=C

4.4

4.4

4.9E+00

4.9E+00

2.4E+02

2.4E+02

6.6E+03

6.6E+03

9

Dimethyl disulfide

624-92-0

S(SC)C

1.9

1.9

3.1E+03

3.1E+03

3.3E+03

3.3E+03

1.0E+02

1.0E+02

Additional information

Chemistry/Structural discussion of the constituents of TOPP

The majority of the constituents of TOPP are terpenes including sesquiterpenes. Others are sulfur containing compounds such as dimethyl sulfide and dimethyl disulfide.

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). Int. J. Pharm. Sci. Rev. Res., 27(2), July – August 2014; Article No. 45, Pages: 272 – 278; http://globalresearchonline.net/journalcontents/v27-2/45.pdf]. 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 in TOPP, 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 major terpenes present in TOPP are monoterpenes (C10H16) and sesquiterpenes (C15H24); other minor constituents are sulfur containing compounds and monoterpenoids (oxygenated and hydrogenated derivatives).

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.

 

Justification for read-across

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

The submission includes use of QSAR and read-across with exact details depending on the endpoint but limited to 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

- Substance(s) with related composition

- Structural analogues to the constituents of the substance

Where relevant data are available for the constituents; these are used in addition to available data for the whole substance.

Hydrocarbons, terpene processing by-products (CAS 68956-56-9)

Compositional comparison of TOPP and hydrocarbon terpenes processing by-products

The registration substance is a UVCB substance containing terpene hydrocarbons, terpene alcohols, sesquiterpenes and sulfur-containing constituents. Similarly, the read-across substance; hydrocarbons, terpene processing by-products contains mainly terpene hydrocarbons and unknown alcohols. The percentage distribution of individual constituents in the read-across substance are shown in Table 1.5.1 (Betat 2013, acute fish study).

Table 1.5.1: Constituents of hydrocarbons, terpene processing by-products (Betat 2013)

S/N

Constituent

CAS No.

% abundance

Is constituent present in TOPP (Yes (Y)/No (N))

1

Alpha fenchene

471-84-1

1.3

Y

2

Alpha pinene

80-56-8

5.0

Y

3

Alpha terpinene

99-86-5

15.1

Y

4

Beta phellandrene

555-10-2

0.3

Y

5

Camphene

79-92-5

8.1

Y

6

Delta-3-carene

13468-78-9

1.0

Y

7

Dipemtene

138-86-3

10.1

Y

8

Gamma terpinene

99-85-4

12.6

Y

9

Myrcene

123-35-3

2.4

Y

10

Para-cymene

99-87-6

4.2

Y

11

Paramentha-2,4(8)diene

586-63-0

3.4

Similar to terpinolene

12

Terpinolene

586-62-9

19.8

Y

13

Tricyclene

508-32-7

1.9

Y

14

Other terpene hydrocarbons

 

3.9

 

15

Cineol-1,4

470-67-7

3.0

Y

16

Cineol-1,8

470-82-6

3.6

Y

17

Alpha terpineol

98-55-5

0.5

Y

18

Borneol

507-70-0

0.8

Y

19

Fenchol

1632-73-1

2.2

Y

20

Gamma terpineol

586-81-2

0.1

Y

21

Isoborneol

124-76-5

0.1

Y

22

Terpinen-3-ol-1

586-82-3

0.4

 

23

Other terpene alcohols

 

0.2

 

 

Both substances contained very similar constituents of mainly hydrocarbon terpene and terpene alcohols. Implication of the presence of sesquiterpenes and sulfur-containing constituents in TOPP are discussed in the relevant section. Therefore, where data gap exists; it is considered relevant to read-across data for hydrocarbons, terpene processing by-product to TOPP.