Buta-1,3-diene

Phototransformation in air

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Principles of method if other than guideline:

The Atmospheric Oxidation Program for Microsoft Windows (AOPWIN) estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals.  It also estimates the rate constant for the gas-phase reaction between ozone and olefinic/acetylenic compounds. The rate constants estimated by the program are then used to calculate atmospheric half-lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals and ozone.

Specific details on test material used for the study:

Buta-1,3-butadiene (SMILE C(C=C)=C)

Light source:

sunlight

Reference substance:

no

Key result

DT50:

1.927 h

Test condition:

OH radicals reaction

Remarks on result:

other: QSAR prediction result

Key result

DT50:

33.96 h

Test condition:

Ozone reaction

Remarks on result:

other: QSAR prediction result

Key result

Reaction with:

OH radicals

Rate constant:

0 cm³ molecule-1 s-1

Remarks on result:

other: QSAR prediction result

Key result

Reaction with:

ozone

Rate constant:

0 cm³ molecule-1 s-1

Remarks on result:

other: QSAR prediction result

The half-life with OH radicals reaction was predicted to be 0.161 d (12 -h day; 1.56 OH/cm3) or 1.927 h. The half-life with ozone reaction was predicted to be 1.415 d (at 7E11 mol/cm3) or 33.96 h).

Validity criteria fulfilled:

yes

Conclusions:

The reference substance is not predicted to be persistent in air.

Executive summary:

AOPwin was used to predicte 1,3 -butadiene persistence in air. The half-life with OH radicals reaction was predicted to be 0.161 d (12 -h day; 1.56 OH/cm3) or 1.927 h. The half-life with ozone reaction was predicted to be 1.415 d (at 7E11 mol/cm3) or 33.96 h). 1,3 -butadiene is not predicted to be persistent in air and is predicted to be mainly degraded by reaction with OH radicals. AOPwin estimates the gas-phase reaction rate for the reaction between the most prevalent atmospheric oxidant, hydroxyl radicals, and a chemical. Atmospheric half-live is calculated using assumed average hydroxyl radical and ozone concentrations.

Reference 2

Endpoint:

phototransformation in air

Type of information:

other: Calculation

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP, non guideline, published in peer reviewed literature, acceptable with restrictions

Principles of method if other than guideline:

Measured data from author and other investigators were quality assessed and then used to develop rate constants for different chemicals. The author applied a least squares analysis of degradation rate constants to calculate a preferred value.

GLP compliance:

no

Remarks:

No data reported

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
No data reported

Estimation method (if used):

No data reported

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:

3.2 d

Test condition:

Based on a rate constant of 1E-13 cm3 molecule-1sec-1 with NO3

Results with reference substance:

No data reported

Author reports a recommended rate constant of 1E-13 cm3 molecule-1sec-1. Half life is calculated based on this rate constant and a NO3 concentration of 2.5E7 molecule.cm-3

Conclusions:

The estimated half life of 1,3-butadiene is 3.2 days based on a recommended reaction rate with NO3 and the concentration of NO3 of 2.5E7 molecules/cm3 in clean air (as used in the EU RAR).

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 1,3-butadiene based on all valid studies at the time of publication. The half life is longer than that reported in the EU RAR for buta-1,3 -diene as a more recent review was available by Atkinson that derived an updated rate constant.

Description of key information

Atmospheric photooxidation half-lives of 1,3-butadiene were predicted to be 1.93 h (hydroxyl radicals), 34.0 h (ozone), and 76.8 h (NO3 radicals). 1,3 -butadiene is not predicted to be persistent in air and is predicted to be mainly degraded by reaction with OH radicals. The reaction rates with ozone and NO3 are less rapid, and therefore less important than the reaction rate with hydroxyl radicals during daylight hours. However, at night, when the concentration of hydroxyl radicals falls to negligible levels, the degradation processes that involve ozone and NO3 will predominate.

Key value for chemical safety assessment

Half-life in air:

1.93 h

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1

Additional information

AOPwin was used to predict 1,3 -butadiene persistence in air. The half-life with OH radicals reaction was predicted to be 0.161 d (12 -h day; 1.56 OH/cm3) or 1.927 h. The half-life with ozone reaction was predicted to be 1.415 d (at 7E11 mol/cm3) or 33.96 h). 1,3 -butadiene is not predicted to be persistent in air and is predicted to be mainly degraded by reaction with OH radicals. AOPwin estimates the gas-phase reaction rate for the reaction between the most prevalent atmospheric oxidant, hydroxyl radicals, and a chemical. Atmospheric half-live is calculated using assumed average hydroxyl radical and ozone concentrations.

The estimated half life of 1,3-butadiene is 3.2 days (76.8 h) based on a recommended reaction rate with NO3 and the concentration of NO3 of 2.5E7 molecules/cm3 in clean air (as used in the EU RAR).