Dichloromethylbenzene

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2009

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

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline required

Principles of method if other than guideline:

Calculation with AOPWIN, v1.92

GLP compliance:

no

Specific details on test material used for the study:

Not applicable

Estimation method (if used):

PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 0.5 E+06 OH/cm³
- Temperature for which rate constant was calculated: 25 °C
- Computer programme: AOP v1.92
- other: 24-h day

Light source:

other: not applicable

Details on light source:

Not applicable

Details on test conditions:

Further details not reported

Temp.:

25 °C

Preliminary study:

Not applicable

Test performance:

No remarks

DT50:

12.165 d

Test condition:

2,4-dichlorotoluene

DT50:

12.165

Test condition:

2,6-dichlorotoluene

DT50:

13.579 d

Test condition:

2,5-dichlorotoluene

DT50:

13.579 d

Test condition:

2,3-dichlorotoluene

DT50:

13.579 d

Test condition:

3,4-dichlorotoluene

Transformation products:

not specified

Results with reference substance:

Not applicable

- Degradation rate constant:

2,4-dichlorotoluene: 1.3188 E-12 cm³/molecule*sec

2,5-dichlorotoluene: 1.1815 E-12 cm³/molecule*sec

2,3-dichlorotoluene: 1.1815 E-12 cm³/molecule*sec

3,4-dichlorotoluene: 1.1815 E-12 cm³/molecule*sec

- Fraction sorbed to airborne particulates (which may be resistant to atmospheric oxidation; Junge, Mackay):

2,4 - dichlorotoluene: 2.85 E-006

2,5 - dichlorotoluene: 3.96 E-006

2,3 - dichlorotoluene: 5.73 E-006

3,4 - dichlorotoluene: 4.15 E-006

Validity criteria fulfilled:

not applicable

Conclusions:

The half-life of photodegradation in air is calculated to be 12.2 days for 2,4- and 2,6-dichlorotoluene and 13.6 days for 2,3-, 2,5- and 3,4- dichlorotoluene. It may be assumed, that a mixture of these isomeres degrades with a half life of 12.2 - 13.6 days.

Executive summary:

The degradation of the individual isomers of dichloromethylbenzene in air by reaction with OH-radicals was estimated with the AOP programme (v1.92). Based on a 24-h day with an OH radical concentration of 0.5 E06 OH/cm³ the half lives were calculated to be

- 12.2 days for 2,4- and 2,6-dichlorotoluene and

- 13.6 days for 2,5- , 2,3- and 3,4-dichlorotoluene.

The degradation rates constantes were 1.32 and 1.18 cm³/molecule*sec, respectively.

For the DCT mixture, the longer half life of 13.6 days is applied as worst-case value.

Reference: Lanxess, 2009

Description of key information

The degradation of individual isomers of dichloromethylbenzene in air by reaction with OH-radicals was estimated with the AOP programme (v1.92). Half lives were calculated to be (Reference: Lanxess, 2009):
- 12.2 days for 2,4- and 2,6-dichlorotoluene and
- 13.6 days for 2,5-, 2,3- and 3,4 - dichlorotoluene. 
For the DCT mixture, the longer half life of 13.6 days is applied as worst-case value.

Key value for chemical safety assessment

Half-life in air:

13.6 d

Additional information

Key study

The degradation of individual isomers of dichloromethylbenzene in air by reaction with OH-radicals was estimated with the AOP programme (v1.92). Based on a 24-h day with an OH radical concentration of 0.5 E06 OH/cm³ the half lives were calculated to be:

- 12.2 days for 2,4-and 2,6-dichlorotoluene and

- 13.6 days for 2,5- , 2,3- and 3,4-dichlorotoluene.

The degradation rates constants were 1.32 and 1.18 cm³/molecule*sec, respectively.

Reference: Lanxess, 2009

Further study

The degradation of dichloromethylbenzene (CAS-No. 29797-40-8) in air by reaction with OH-radicals was estimated with the Atkinson (AOP) and with the MOOH-method.

a) Atkinson (AOP): Based on a 12-h day with a OH radical concentration of 1.5 E06 molecules/cm³, a half-life of 4.51 days was estimated.

b) The calculation according to the MOOH-method with the programme MOPAC vers. 6.00 resulted in a half-life of 14.95 days.

For this QSARs too few data were reported for assessing the reliability.

Reference: Rorije, 1997