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Environmental fate & pathways

Hydrolysis

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Endpoint:
hydrolysis
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The QSAR is well documented the test compound fits well within applicability domain and the QSAR is applied for a well defined endpoint
Justification for type of information:
QSAR prediction
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: T. Mill, W. Haag, P. Penwell, T. Pettit and H. Johnson. Environmental fate and exposure studies development of a PC-SAR for hydrolysis: Esters, alkyl halides and epoxides. EPA contract 68-02-4254. SRI International, 1987
Principles of method if other than guideline:
The chemical structure of the compound is the starting point of the analysis. A specific approach was developed for different groups of compounds.For phosphate esters like DBPP a specific QSAR was available.
Hydrolysis rates were based on which chemical bonds are present in the compound and estmates of parameters to describe the steric hindrance for each substituent in the phosphate ester.
GLP compliance:
no
Specific details on test material used for the study:
not applicable
Analytical monitoring:
not required
Details on sampling:
not applicable
Buffers:
not applicable
Estimation method (if used):
The estimation method is based on T. Mill, W. Haag, P. Penwell, T. Pettit and H. Johnson. Environmental fate and exposure studies development of a PC-SAR for hydrolysis: Esters, alkyl halides and epoxides. EPA contract 68-02-4254. SRI International, 1987. This method was adapted to make predictions on phosphate esters, described by W.M. Meylan and P.H. Howard, Environmental Science Centre, Syracuse Research Corporation, Syracuse, NY 13212, 2007
Details on test conditions:
not applicable
Number of replicates:
not applicable
Statistical methods:
not appliacble
Transformation products:
not specified
pH:
7
Temp.:
25 °C
DT50:
19.25 yr
pH:
10
Temp.:
25 °C
DT50:
7.79 d
Validity criteria fulfilled:
not applicable
Conclusions:
The hydrolysis half life of BDPP was estimated for a pH of 5 to 10. Currently it is not possible to derive an acid based hydrolysis rate. The estimated half life of BDPP at ambient temperatures and pH = 5 is 180 years The estimated half life of BDPP at ambient temperatures and pH = 6 is 102.3 years The estimated half life of BDPP at ambient temperatures and pH = 7 is 19.25 years The estimated half life of BDPP at ambient temperatures and pH = 8 is 21.4 years The estimated half life of BDPP at ambient temperatures and pH = 9 is 77.82 days The estimated half life of BDPP at ambient temperatures and pH = 10 is 7.79 days
Executive summary:

The half life for hydrolysis of BDPP was estimated using a QSAR. This QSAR is well defined and BDPP falls well within the applicability domain of the QSAR.

The hydrolysis half life of BDPP was estimated for different pHs. Currently it is not possible to derive an acid based hydrolysis rate. The estimated half life of BDPP at ambient temperatures and pH = 7 is 19.25 years The estimated half life of DBPP at ambient temperatures is minimal at a pH of 10 (7.79 days).

Based on this information it can be concluded that BDPP has a low to non-existing potential for hydrolysis around neutral pH. At higher pH values some potential for hydrolysis exists.

Endpoint:
hydrolysis
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The QSAR is well documented the test compound fits well within applicability domain and the QSAR is applied for a well defined endpoint
Justification for type of information:
QSAR prediction
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: T. Mill, W. Haag, P. Penwell, T. Pettit and H. Johnson. Environmental fate and exposure studies development of a PC-SAR for hydrolysis: Esters, alkyl halides and epoxides. EPA contract 68-02-4254. SRI International, 1987
Principles of method if other than guideline:
The chemical structure of the compound is the starting point of the analysis. A specific approach was developed for different groups of compounds.For phosphate esters like DBPP a specific QSAR was available.
Hydrolysis rates were based on which chemical bonds are present in the compound and estmates of parameters to describe the steric hindrance for each substituent in the phosphate ester.
GLP compliance:
no
Specific details on test material used for the study:
not applicable
Analytical monitoring:
not required
Details on sampling:
not applicable
Buffers:
not applicable
Estimation method (if used):
The estimation method is based on T. Mill, W. Haag, P. Penwell, T. Pettit and H. Johnson. Environmental fate and exposure studies development of a PC-SAR for hydrolysis: Esters, alkyl halides and epoxides. EPA contract 68-02-4254. SRI International, 1987. This method was adapted to make predictions on phosphate esters, described by W.M. Meylan and P.H. Howard, Environmental Science Centre, Syracuse Research Corporation, Syracuse, NY 13212, 2007
Details on test conditions:
not applicable
Number of replicates:
not applicable
Statistical methods:
not appliacble
Transformation products:
not specified
pH:
7
Temp.:
25 °C
DT50:
42.3 yr
pH:
10
Temp.:
25 °C
DT50:
140.4 d
Validity criteria fulfilled:
not applicable
Conclusions:
The hydrolysis half life of DBPP was estimated for a pH of 5 to 10. Currently it is not possible to derive an acid based hydrolysis rate. The estimated half life of DBPP at ambient temperatures and pH = 5 is 47.4 years The estimated half life of DBPP at ambient temperatures and pH = 6 is 46.9 years The estimated half life of DBPP at ambient temperatures and pH = 7 is 42.3 years The estimated half life of DBPP at ambient temperatures and pH = 8 is 21.4 years The estimated half life of DBPP at ambient temperatures and pH = 9 is 3.6 years The estimated half life of DBPP at ambient temperatures and pH = 10 is 140.4 days
Executive summary:

The half life for hydrolysis of DBPP was estimated using a QSAR. This QSAR is well defined and DBPP falls well within the applicability domain of the QSAR.

The hydrolysis half life of DBPP was estimated for different pHs. Currently it is not possible to derive an acid based hydrolysis rate. The estimated half life of DBPP at ambient temperatures and pH = 7 is 42.3 years The estimated half life of DBPP at ambient temperatures is minimal at a pH of 10 (140.4 days).

Based on this information it can be concluded that DBPP has a low to non-existing potential for hydrolysis.

Endpoint:
hydrolysis
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The QSAR is well documented the test compound fits well within applicability domain and the QSAR is applied for a well defined endpoint
Justification for type of information:
QSAR prediction
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: T. Mill, W. Haag, P. Penwell, T. Pettit and H. Johnson. Environmental fate and exposure studies development of a PC-SAR for hydrolysis: Esters, alkyl halides and epoxides. EPA contract 68-02-4254. SRI International, 1987
Principles of method if other than guideline:
The chemical structure of the compound is the starting point of the analysis. A specific approach was developed for different groups of compounds.For phosphate esters like TBP a specific QSAR was available.
Hydrolysis rates were based on which chemical bonds are present in the compound and estmates of parameters to describe the steric hindrance for each substituent in the phosphate ester.
GLP compliance:
no
Specific details on test material used for the study:
not applicable
Analytical monitoring:
not required
Details on sampling:
not applicable
Buffers:
not applicable
Estimation method (if used):
The estimation method is based on T. Mill, W. Haag, P. Penwell, T. Pettit and H. Johnson. Environmental fate and exposure studies development of a PC-SAR for hydrolysis: Esters, alkyl halides and epoxides. EPA contract 68-02-4254. SRI International, 1987. This method was adapted to make predictions on phosphate esters, described by W.M. Meylan and P.H. Howard, Environmental Science Centre, Syracuse Research Corporation, Syracuse, NY 13212, 2007
Details on test conditions:
not applicable
Number of replicates:
not applicable
Statistical methods:
not appliacble
Transformation products:
not specified
pH:
7
Temp.:
25 °C
DT50:
11.45 yr
pH:
10
Temp.:
25 °C
DT50:
4.37 yr
Validity criteria fulfilled:
not applicable
Conclusions:
The hydrolysis half life of TBP was estimated for a pH of 5 to 10. Currently it is not possible to derive an acid based hydrolysis rate. The estimated half life of TBP at ambient temperatures and pH = 5 is 11.47 years The estimated half life of TBP at ambient temperatures and pH = 6 is 11.47 years The estimated half life of TBP at ambient temperatures and pH = 7 is 11.45 years The estimated half life of TBP at ambient temperatures and pH = 8 is 11.29 years The estimated half life of TBP at ambient temperatures and pH = 9 is 9.87 years The estimated half life of TBP at ambient temperatures and pH = 10 is 4.37 years
Executive summary:

The half life for hydrolysis of TBP was estimated using a QSAR. This QSAR is well defined and TBP falls well within the applicability domain of the QSAR.

The hydrolysis half life of TBP was estimated for different pHs. Currently it is not possible to derive an acid based hydrolysis rate. The estimated half life of TBP at ambient temperatures and pH = 7 is 11.45 years The estimated half life of TBP at ambient temperatures is minimal at a pH of 10 (4.37 years).

Based on this information it can be concluded that TBP has a low to non-existing potential for hydrolysis.

Description of key information

The hydrolysis half life of the constituents of the DBPP multi-constituent were estimated for different pHs using a QSAR (EpiSuite v4.10). This QSAR is well defined and the DBPP constituents falls well within the applicability domain of the QSAR.  The estimated half life of DBPP mono-constituent is regarded the most relevant one, the results of the other constituents are in the same range (>100 days to years). At ambient temperatures and pH = 7 the hydrolysis half life is 42.3 years for the DBPP mono-constituent. The estimated half life of DBPP mono-constituent at ambient temperatures and pH = 10 is 140.4 days. In conclusion it can be stated that the substance has a low  to non-existing hydrolysis potential.

Key value for chemical safety assessment

Half-life for hydrolysis:
42.3 yr
at the temperature of:
25 °C

Additional information

The hydrolysis half life of Dibutyl phenyl phosphate (DBPP), Tributyl phosphate (TBP) and Butyl diphenyl phosphate (BDPP) was estimated for different pHs using a QSAR (EpiSuite v4.10). This QSAR is well defined and all three phosphate esters fall well within the applicability domain of the QSAR.

Compound              pH                     Hydrolysis half life

DBPP                     7                            42.31 years

DBPP                     10                         140.4 days

TBP                      7                            11.45 years

TBP                        10                          4.37 years

BDPP                     7                            19.25 years

BDPP                     10                            7.79 days

The estimated half life of all three compounds at ambient temperatures and pH = 7 is well over 10 years. In conclusion it can be stated that all three substances have a low to non-existing hydrolysis potential at neutral pHs.