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Environmental fate & pathways

Phototransformation in air

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Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
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.
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.

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.

Description of key information

There is data available for this substance. Additionally, key data is available for the structural analogue Pentane and is presented in the dossier. The data is read across to these substances 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

Additional information