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Vapour pressure

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Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Validated QSAR calculation method. A validated QPRF is attached. The substance is recognised as part of the rulebase utilised by the EPI Suite model data set, and is in model Applicability Domain. Further details can be found within the appended report below or at http://www.epa.gov/oppt/exposure/pubs/episuite.htm. This system is recognised in ECHA Guidance document CHAPTER R.6 – QSARS AND GROUPING OF CHEMICALS, ref R.6.1.4.3 Use of (Q)SARs for PBT (vPvB) assessment
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Qualifier:
according to
Guideline:
other: US EPA On-Line EPI Suite™ MPBPWIN v1.43
Deviations:
no
Principles of method if other than guideline:
MPBPWIN estimates vapor pressure (VP) by three separate methods: (1) the Antoine method, (2) the modified Grain method, and (3) the Mackay method.  All three use the normal boiling point to estimate VP.  Unless the user enters a boiling point on the data entry screen,  MPBPWIN uses the estimated boiling point from the adapted Stein and Brown method as described in the Boiling Point section of this help file.  When a boiling point is entered on the data entry screen, MPBPWIN uses it.  Each VP method is discussed below.

Antoine Method:  Chapter 14 of Lyman et al (1990) includes the description of the Antoine method used by MPBPWIN.  It was developed for gases and liquids.  The Antoine equation is used to estimate vapor pressure from the normal boiling (Tb). The KF structural factors are available in chapter 14 of Lyman et al (1990); the variation of this parameter is related to chemical class and is small (roughly 0.99 to 1.2), so large errors in its selection are unlikely (Lyman, 1985).  The value of R is 1.987 cal/mol-K. MPBPWIN has extended the Antoine method to make it applicable to solids by using the same methodology as the modified Grain method to convert a super-cooled liquid VP to a solid-phase VP as shown below.

Modified Grain Method:   Chapter 2 of Lyman (1985) describes the modified Grain method used by MPBPWIN.  This method is a modification and significant improvement of the modified Watson method.  It is applicable to solids, liquids and gases. The KF structural factors are available in chapter 14 of Lyman et al (1990); the variation of this parameter is related to chemical class and is small (roughly 0.99 to 1.2), so large errors in its selection are unlikely (Lyman, 1985).  The modified Grain method may be the best all-around VP estimation method currently available.

 

Mackay Method:    Mackay derived the following equation to estimate VP (Lyman, 1985):

 ln P  =  -(4.4 + ln Tb)[1.803(Tb/T - 1) - 0.803 ln(Tb/T)] - 6.8(Tm/T - 1)

where Tb is the normal boiling pt (K), T is the VP temperature (K) and Tm is the melting pt (K).  The melting point term is ignored for liquids.  It was derived from two chemical classes: hydrocarbons (aliphatic and aromatic) and halogenated compounds (again aliphatic and aromatic).

MPBPWIN reports the VP estimate from all three methods.  It then reports a "suggested" VP.  For solids, the modified Grain estimate is the suggested VP.  For liquids and gases, the suggested VP is the average of the Antoine and the modified Grain estimates.  The Mackay method is not used in the suggested VP because its application is currently limited to its derivation classes.
GLP compliance:
no
Type of method:
other: QSAR Derivation
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: Modified Grain method results are taken; geometric mean values are derived. Individual results are reported below.
Conclusions:
The model is considered to be appropriate for assessment. Strongly similar compounds with known experimental value in the training set were found.
The accuracy of prediction for similar molecules found in the training set is good. he model is considered suitable for use in the context of a weight of evidence approach. Due to the high variability of the positioning of the propyl subgroups in this UVCB material, a definitive SMILES code is not applicable. 50 possible structures were taken for the purposes of assessment; the results are listed in Appendix 1 to the appended QPRF above. The average of these was taken as the definitive value , with similar results observed across the isomer groups.
The substance is considered to have a low volatility.
Executive summary:

The model is considered to be appropriate for assessment. Strongly similar compounds with known experimental value in the training set were found.

The accuracy of prediction for similar molecules found in the training set is good. he model is considered suitable for use in the context of a weight of evidence approach. Due to the high variability of the positioning of the propyl subgroups in this UVCB material, a definitive SMILES code is not applicable. 50 possible structures were taken for the purposes of assessment; the results are listed in Appendix 1 to the appended QPRF above. The average of these was taken as the definitive value , with similar results observed across the isomer groups.

The substance is considered to have a low volatility.

Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Validated QSAR calculation method. TEST enables users to easily estimate acute toxicity using the above QSAR methodologies. The software is described in further detail in the User's Guide for TEST (version 4.1) (http://www.epa.gov/nrmrl/std/qsar/TEST-user-guide-v41.pdf).The software is based on the Chemistry Development Kit exit EPA, an open-source Java library for computational chemistry.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Qualifier:
according to
Guideline:
other: US EPA (T.E.S.T) v4.1
Deviations:
no
Principles of method if other than guideline:
The Toxicity Estimation Software Tool is an open-source application developed by the US EPA. It estimates the toxicity of a compound by applying several QSAR methodologies thus allowing the user to have greater confidence in predicted toxicities. Among other toxi cities it predicts rat oral LD50, Ames mutagenicity, developmental toxicity, as well as acute toxicity to fish (fathead minnow), Daphnia magna and Tetrahymena pyriformis. The tool is freely downloadable from the EPA website (http://www.epa.gov/nrmrl/std/cppb/qsar/index.html#TEST). The models are well documented and the training set is made available as structure files (SDF file).
GLP compliance:
no
Type of method:
other: QSAR Derivation
Temp.:
25 °C
Vapour pressure:
0 Pa
Remarks on result:
other: Consensus method results are taken; geometric mean values are derived. Individual results are reported below.
Conclusions:
The model is considered to be appropriate for assessment. Strongly similar compounds with known experimental value in the training set were found.
The accuracy of prediction for similar molecules found in the training set is good. he model is considered suitable for use in the context of a weight of evidence approach. Due to the high variability of the positioning of the propyl subgroups in this UVCB material, 50 possible structures were taken for the purposes of assessment; the results are listed above under "attached background material". The average of these was taken as the definitive value. The substance is considered to have a low volatility.
Executive summary:

The model is considered to be appropriate for assessment. Strongly similar compounds with known experimental value in the training set were found.

The accuracy of prediction for similar molecules found in the training set is good. he model is considered suitable for use in the context of a weight of evidence approach. Due to the high variability of the positioning of the propyl subgroups in this UVCB material, 50 possible structures were taken for the purposes of assessment; the results are listed above under "attached background material".

The substance is considered to have a low volatility.

Description of key information

Vapour pressure

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
25 °C

Additional information

A GLP study was carried out according to recognised guideline. However, the results observed are not representative of the expectations for vapour pressure for this type of substance. The phosphates as a group do not demonstrate vapour pressures at the level noted within the study. One justification for this is the methodology used. OECD 104 provides a variety of measuring methods for the vapour pressure parameter.  However, the Isoteniscope method utilised in this study is only suitable for substances with a vapor pressure range of 10E+02 to 10E+05 Pa. This method should not be used to determine vapor pressure of substances with expected low levels of volatility, such as is noted in analogue materials. The high results obtained in this study are unreliable due to the method’s non-applicable range of vapor pressure.

 

In the absence of reliable study data, QSAR data is utilised to provide realistic values for use in safety assessment. QSAR assessment of the components of the substance details the following results:

 

Number

Vapour Pressure - EPIWIN MPBPVP v1.43 - Pa

Vapour Pressure - US EPA (T.E.S.T) v4.1 - mmHg

Vapour Pressure - US EPA (T.E.S.T) v4.1 - Pa

1

0.001500

0.00000087600

0.0001167903944

2

0.000022

0.00000051400

0.0000685276972

3

0.000022

0.00000026600

0.0000354637499

4

0.000022

0.00000017800

0.0000237313815

5

0.000012

0.00000008170

0.0000108924375

6

0.000012

0.00000007220

0.0000096258750

7

0.000012

0.00000005580

0.0000074393881

8

0.000012

0.00000003350

0.0000044662993

9

0.000012

0.00000004860

0.0000064794671

10

0.000012

0.00000001970

0.0000026264506

11

0.000012

0.00000013600

0.0000181318420

12

0.000012

0.00000001940

0.0000025864539

13

0.000012

0.00000001410

0.0000018798454

14

0.000012

0.00000004630

0.0000061728256

15

0.000012

0.00000002010

0.0000026797796

16

0.000012

0.00000003360

0.0000044796316

17

0.000012

0.00000000746

0.0000009945849

18

0.000012

0.00000002450

0.0000032663980

19

0.000012

0.00000002570

0.0000034263849

20

0.000012

0.00000000689

0.0000009185911

21

0.000012

0.00000009830

0.0000131055888

22

0.000012

0.00000000009

0.0000000125056

23

0.000012

0.00000000359

0.0000004786273

24

0.000012

0.00000002600

0.0000034663816

25

0.000012

0.00000000424

0.0000005652868

26

0.000012

0.00000000860

0.0000011465724

27

0.000012

0.00000004940

0.0000065861250

28

0.000012

0.00000003420

0.0000045596250

29

0.000012

0.00000006770

0.0000090259243

30

0.000012

0.00000002100

0.0000027997697

31

0.000012

0.00000000448

0.0000005972842

32

0.000012

0.00000000161

0.0000002146490

33

0.000012

0.00000004420

0.0000058928487

34

0.000012

0.00000001970

0.0000026264506

35

0.000012

0.00000000010

0.0000000129856

36

0.000012

0.00000000656

0.0000008745947

37

0.000012

0.00000004070

0.0000054262204

38

0.000012

0.00000000390

0.0000005199572

39

0.000012

0.00000000013

0.0000000178652

40

0.000012

0.00000004480

0.0000059728421

41

0.000012

0.00000003280

0.0000043729737

42

0.000012

0.00000001210

0.0000016132007

43

0.000012

0.00000008730

0.0000116390427

44

0.000012

0.00000020000

0.0000266644736

45

0.000012

0.00000002460

0.0000032797303

46

0.000012

0.00000000359

0.0000004786273

47

0.000012

0.00000016000

0.0000213315789

48

0.000012

0.00000002820

0.0000037596908

49

0.000012

0.00000001400

0.0000018665132

50

0.000012

0.00000000009

0.0000000120790

Geometric Mean of Results.

0.0000134

0.000000019

0.0000025

 

On the basis of the QSAR derivations and in view of known study data on structural analogues, it is deemed appropriate to utilise the higher of the two QSAR values for vapour pressure for the purposes of hazard assessment. As such, the QSAR values derived using the US EPA On-Line EPI Suite™ MPBPWIN v1.43are used as the base value.