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EC number: 204-428-0 | CAS number: 120-82-1
Phototransformation in air
Administrative data
Link to relevant study record(s)
- Endpoint:
- phototransformation in air
- Type of information:
- other: not specified if experimental or calculated values
- Adequacy of study:
- other information
- Reliability:
- 4 (not assignable)
- Rationale for reliability incl. deficiencies:
- other: Original reference is not available.
- GLP compliance:
- not specified
- Executive summary:
UBA, 1984
kOH = 0.6 x 10e-12 cm3/s
t1/2 = 27 d ((OH) = 5 x 10e5/cm3)- Endpoint:
- phototransformation in air
- Type of information:
- other: not specified if experimental or calculated values
- Adequacy of study:
- other information
- Reliability:
- 4 (not assignable)
- Rationale for reliability incl. deficiencies:
- other: Original reference is not available.
- GLP compliance:
- not specified
- Executive summary:
Mackay, 1992
Suggested half-life in air:
mean half-life (hours): 550 (ca. 3 weeks); range (hours): 300 - 1000- Endpoint:
- phototransformation in air
- Type of information:
- other: not specified if experimental or calculated values
- Adequacy of study:
- other information
- Reliability:
- 4 (not assignable)
- Rationale for reliability incl. deficiencies:
- other: Original reference is not available.
- GLP compliance:
- not specified
- Executive summary:
Howard, 1991
Half-lives in air: high: 1284 hours (53.5 days)
low: 128.4 hours (5.4 days)- Endpoint:
- phototransformation in air
- Type of information:
- other: not specified if calculated or experimental result
- Adequacy of study:
- other information
- Reliability:
- 4 (not assignable)
- Rationale for reliability incl. deficiencies:
- other: Original reference is not available.
- GLP compliance:
- not specified
- Executive summary:
Bunce, 1989
direct photolysis in the vapour phase
calculated minimum photolytic half-life: ca. 4 months- Endpoint:
- phototransformation in air
- Type of information:
- (Q)SAR
- Adequacy of study:
- other information
- Reliability:
- 4 (not assignable)
- Rationale for reliability incl. deficiencies:
- results derived from a (Q)SAR model, with limited documentation / justification
- GLP compliance:
- not specified
- Executive summary:
AOPWIN 3.1, 1994, calculation
OH rate constant = 0.2908 E-12 [cm3/molecule/s]
half-life time = 55.178 days (24 h; 0.5 E6 OH/cm3)- Endpoint:
- phototransformation in air
- Type of information:
- experimental study
- Adequacy of study:
- other information
- Reliability:
- 4 (not assignable)
- Rationale for reliability incl. deficiencies:
- documentation insufficient for assessment
- Principles of method if other than guideline:
- - irradiation of 14C-labeled 1,2,4-trichlorbenzene by a wavelength of 290 nm
- the percentage of evolving radioactive CO2 was measured = photomineralisation - GLP compliance:
- not specified
- Specific details on test material used for the study:
- - Name of test material (as cited in study report): 1,2,4-Trichlorbenzol
- Analytical purity: no data
- Radiochemical purity (if radiolabelling): no data - Light source:
- other: mercury vapour lamp
- Light spectrum: wavelength in nm:
- 290
- Parameter:
- other: photomineralisation
- Value:
- 9.8 other:
- Remarks on result:
- other: % CO2
- Transformation products:
- yes
- Executive summary:
Korte, 1986
When 14C-labeled 1,2,4-trichlorbenzene was irradiated at a wavelength of 290 nm and the percentage of evolving radioactive CO2 was measured (defined as photomineralisation) an experimental value of 9.8% CO2 was determined.
- Endpoint:
- phototransformation in air
- Type of information:
- other: EU Risk Assessment
- Adequacy of study:
- other information
- Reliability:
- other: EU Risk Assessment
- Rationale for reliability incl. deficiencies:
- other: No reliability is given as this is a summary entry for the EU RAR.
- GLP compliance:
- not specified
- Executive summary:
EU Risk Assessment (2003):
Atmospheric photodegradation occurs with a half-life of approximately 30 days which is used in the risk assessment.
The photodegradation of 1,2,4-TCB by hydroxyl radicals in the atmosphere is estimated to be in the order of a month. However, the values should been considered as the upper limit of stability since other degradation modes are not considered.
Referenceopen allclose all
EU Risk Assessment (2003):
Atmospheric photodegradation occurs with a half-life of approximately 30 days which is used in the risk assessment.
The photodegradation of 1,2,4-TCB by hydroxyl radicals in the atmosphere is estimated to be in the order of a month. However, the values should been considered as the upper limit of stability since other degradation modes are not considered.
Summerisation of data on photodegradation:
Rate constant [cm3/ molecule / s] |
Half-life [days] |
Method |
Reference |
5.32*10-13 |
18.5 |
Experimental |
Atkinson et al. (1985) |
5.32*10-13 |
30.2 |
Measured, 296ºK |
Rinke and Zetzsch (1984) |
2.82*10-13 |
38.0 |
Calculated by AOP programme |
AOPWIN (1995) |
The reaction of 1,2,4-TCB with OH radicals was investigated in the presence of helium at pressures from 5 to 800 mbar using a pulsed vacuum UV photolysis-resonance fluorescence apparatus. At 23°C and 133 mbar helium, the rate constant k was observed to be 0.5*10-12cm3/s (Rinke and Zetzsch, 1984). Assuming an average tropospheric OH radical concentration of 5*105molecules/cm3, the half-life is about 30 days (BUA, 1987).
In the atmosphere, the estimated vapour phase half-life of 1,2,4-TCB was 18.5 days estimated as a result of reaction with photochemically produced hydroxyl radicals at 8*105molecules/cm3giving a reaction rate of 0.532*10-12cm3/molecules/sec (Atkinson et al., 1985). The photochemical oxidation was estimated using the structure analysis by the model AOPWIN (1995) for comparison. The estimated half-life of 38 days is based on the OH-radical concentration of 1.5*106molecules/cm3and a 12-hour daylight period. The previous model used 5*105molecules/cm3which was a 24-hour average value that included nighttime. Using 5*105molecules/cm3(24 hours) would result in a T½ of 57 days estimated by AOPWIN (1995).
It is mentioned in IUCLID that using an experimental value for the OH rate constant of 0.55*10-12cm3/molecules/s and by setting the OH radical concentration to 5*105molecules/ cm3, a T½ of 29 days would be estimated (IUCLID, 1996; Rippen 1991). The value is based on the geometric mean of the measured absolute KOHvalue (296ºK) 0.5*10-12cm3/s and a relative measured KOH value (300ºK) 0.6*10 -12cm3/s (Rippen, 1991). However, the mentioned value is the weighted average from the study and not the 296ºK, cf. the table.
The removal of 1,2,4 -TCB in air may be by degradation by chemical- or sunlight-catalysed reactions or absorption onto particles that settle or are removed from the atmosphere by rain. A measure of the effectiveness of these factors is the atmospheric residence time. In a field study inand, air samples during a two-week period included an unspecified trichlorobenzene. The estimated residence time was 116 days assuming an average daily (24 hours) abundance of OH radicals of 106molecules/ cm3. The daily loss rates estimated for 12 hours was 0.9% (Singh et al., 1981).
Description of key information
For transported isolated intermediates according to REACh, Article 18, this endpoint is not a data requirement. However, data is available for this endpoint and is thus reported under the guidance of "all available data".
EU Risk Assessment (2003)
Atmospheric photodegradation occurs with a half-life of approximately 30 days.
The photodegradation of 1,2,4-TCB by hydroxyl radicals in the atmosphere is estimated to be in the order of a month. However, the values should been considered as the upper limit of stability since other degradation modes are not considered.
Korte, 1986
When 14C-labeled 1,2,4-trichlorbenzene was irradiated at a wavelength of 290 nm and the percentage of evolving radioactive CO2 was measured (defined as photomineralisation) an experimental value of 9.8% CO2 was determined.
Bunce, 1989
direct photolysis in the vapour phase
calculated minimum photolytic half-life: ca. 4 months
Howard, 1991
Half-lives in air: high: 1284 hours (53.5 days); low: 128.4 hours (5.4 days)
Mackay, 1992
Suggested half-life in air:
mean half-life (hours): 550 (ca. 3 weeks); range (hours): 300 - 1000
UBA, 1984
kOH = 0.6 x 10e-12 cm3/s
t1/2 = 27 d ((OH) = 5 x 10e5/cm3)
AOPWIN 3.1, 1994, calculation
OH rate constant = 0.2908 E-12 [cm3/molecule/s]
half-life time = 55.178 days (24 h; 0.5 E6 OH/cm3)
Key value for chemical safety assessment
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