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Environmental fate & pathways

Phototransformation in air

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Endpoint:
phototransformation in air
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
estimated by calculation
Adequacy of study:
key study
Study period:
Up to 1985
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, non guideline study. Data calculated in accordance with TGD guideline. Study published in peer review literature.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across: supporting information
Principles of method if other than guideline:
The author applied a least squares analysis of degradation rate constants for organic chemicals by hydroxyl radicals developed by other investigators.
GLP compliance:
not specified
Remarks:
No data reported
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data reported
Estimation method (if used):
Calculated half life based on -OH radical concentration of 5 E5 molecules/cm3 as specified in the TGD
Light source:
not specified
Details on light source:
No data reported
Details on test conditions:
No data reported
Preliminary study:
No data reported
Test performance:
No data reported
Key result
DT50:
3.95 d
Test condition:
No data reported
Results with reference substance:
No data reported

The rate constant of the reaction between n-pentane and OH-radicals has been measured by several researchers. The result of the experiments have been reported and reviewed by Atkinson (1985). The reported values are between 3.5 and 5.3.10-12 cm3/(molecule.sec) at 300K (27C). On the basis of the review of available data Atkinson recommends a rate of 4.06.10-12 cm3/ (molecule.sec). The latter value has been used in the risk assessment. Taking into account the OH-radical concentration as given in the TGD of 5.105 molecules/cm3, atmospheric half-life of n-pentane is estimated to 3.95 days.

Conclusions:
The atmospheric half-life of n-pentane is estimated to be 3.95 days.
Executive summary:

Measured data from author and other investigators were quality assessed and then used to develop rate constants for different chemicals. Therefore, this value represents a valid rate constant for n-pentane based on all valid studies at the time of publication. The half life of n-pentane is 3.95 days.

Endpoint:
phototransformation in air
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Remarks:
estimated by calculation
Adequacy of study:
key study
Study period:
Up to 1985
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, non guideline study. Calculated data, published in peer review paper and was calculated in accordance with the TGD.
Justification for type of information:
A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across: supporting information
Principles of method if other than guideline:
The author used data from other investigators. This data was generated using two methods: absolute and relative constant techniques. The author then applied a least squares analysis of degradation rate constants for organic chemicals by hydroxyl radicals developed by other investigators. This calculation was in accordance with the TGD
GLP compliance:
not specified
Remarks:
Not reported
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data reported
Estimation method (if used):
Endpoint was calculated based on a rate constant of 3.5 E -12 and-OH radical concentration of 5 E5 molecules/cm3
Details on light source:
No data reported
Details on test conditions:
No data reported
Preliminary study:
No data reported
Test performance:
No data reported
Key result
DT50:
2.3 d
Results with reference substance:
No data reported

Based on a calculated rate constant of 7.38E-12 cm3 molecule-1sec-1, and a hydroxyl radical concentration of 5E5 molecule.cm-3

Conclusions:
The dissipation half-life of 2-methylbutane was calculated as 2.3 days
Executive summary:

Measured data from author and other investigators were quality assessed and then used to develop rate constants for different chemicals. Therefore, this value represents a valid rate constant for 2 -methylbutane based on all valid studies at the time of publication. The half life of 2 -methylbutane is 2.3 days.

Description of key information

There is no data available for this substance. However, key data is available for the structural analogues Pentane and 2 -methylbutane and is presented in the dossier. The data is read across to this substance based on analogue read across and a discussion and report on the read across strategy is provided as an attachment inIUCLID Section 13.

The dissipation half-life of 2-methylbutane was calculated as 2.3 days. Based on a calculated rate constant of 7.38E-12 cm3 molecule-1sec-1, and a hydroxyl radical concentration of 5E5 molecule.cm-3.

The atmospheric half-life of n-pentane is estimated to be 3.95 days. The rate constant of the reaction between n-pentane and OH-radicals has been measured by several researchers. The result of the experiments have been reported and reviewed by Atkinson (1985). The reported values are between 3.5 and 5.3.10-12 cm3/(molecule.sec) at 300K (27C). On the basis of the review of available data Atkinson recommends a rate of 4.06.10-12 cm3/ (molecule.sec). The latter value has been used in the risk assessment. Taking into account the OH-radical concentration as given in the TGD of 5.105 molecules/cm3

Key value for chemical safety assessment

Half-life in air:
3.95 d
Degradation rate constant with OH radicals:
0 cm³ molecule-1 s-1

Additional information