1,2,4-trichlorobenzene

Phototransformation in water

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in water

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

EU Risk Assessment (2003):

Degradation by direct photolysis is not expected to be essential because the maximum absorption value is 286 nm (Bayer spectral data). The half-life for sunlight photolysis in pure surface water at 40° latitude in summer was 450 years (Dulin et al., 1986). The recovery of 1,2,4-TCB from isopropanol solution in Pyrex glass tubing (with a cut-off at 285 nm) irradiated with 300 and 310 nm fluorescent lamps for 30 minutes was 89.4% under anaerobic conditions where O2 was replaced with N2 and 8.1% under aerobic conditions. The products of photodegradation were 1,3- and 1,4-dichlorobenzene (Akermark et al., 1976).

 

In a laboratory study using artificial light (high pressure mercury vapour lamp at wavelengths > 290 nm), the photodegradation was studied at a concentration of 2-5 ppm. 1,2,4-TCB was dissolved in distilled water and filtered river water. The photolytic half-life was estimated to be 16.7 hours in distilled water and 12.2 hours in river water. The photolysis products in river water were 1,4-dichlorophenol and 4-chlorophenol (Mansour et al., 1989).

 

The photolysis was studied by exposing 5 ml 1,2,4-TCB at 4µg/ml at a distance of 30 cm from artificial light (Fluorochemical lamps 20W.2) at 25°C. After 144 hours, 0% was degraded (Kondo et al., 1988).

 

In a test where 1,2,4-TCB was adsorbed on silica gel and irradiated with light at wavelengths > 290 nm for 17 hours, 9.8% of the applied amount was degraded to CO2 (Freitag et al., 1985).

 

In addition to the direct photolysis, the photodegradation may also follow an indirect photolysis by sensitisation by secondary reactions with OH- and O2-radicals. The photolysis was studied in water solutions 600 ml at 4-20 mg/l irradiated for 3 hours. The photoreactivity in solutions in the presence of nitrite was observed to increase the photodegradation rate. The rate constant in pure water was 1.5*10^-4s^-1resulting in T½ to be 1.2 hours. In water added nitrite, the rate constant k was 3.1*10^-4s^-1and the resulting T½ 0.4 hours (Kotzias et al., 1982). The study was conducted under artificial conditions but indicates that photolysis may be affected by the contents in water. In the study, salts were used but other organic substances and organic matter may also affect the photodegradation rate.

Executive summary:

EU Risk Assessment (2003):

Degradation by direct photolysis is not expected to be essential because the maximum absorption value is 286 nm (Bayer spectral data). The half-life for sunlight photolysis in pure surface water at 40° latitude in summer was 450 years (Dulin et al., 1986). The recovery of 1,2,4-TCB from isopropanol solution in Pyrex glass tubing (with a cut-off at 285 nm) irradiated with 300 and 310 nm fluorescent lamps for 30 minutes was 89.4% under anaerobic conditions where O₂ was replaced with N₂ and 8.1% under aerobic conditions. The products of photodegradation were 1,3- and 1,4-dichlorobenzene (Akermark et al., 1976).

In a laboratory study using artificial light (high pressure mercury vapour lamp at wavelengths > 290 nm), the photodegradation was studied at a concentration of 2-5 ppm. 1,2,4-TCB was dissolved in distilled water and filtered river water. The photolytic half-life was estimated to be 16.7 hours in distilled water and 12.2 hours in river water. The photolysis products in river water were 1,4-dichlorophenol and 4-chlorophenol (Mansour et al., 1989).

The photolysis was studied by exposing 5 ml 1,2,4-TCB at 4µg/ml at a distance of 30 cm from artificial light (Fluorochemical lamps 20W.2) at 25°C. After 144 hours, 0% was degraded (Kondo et al., 1988).

In a test where 1,2,4-TCB was adsorbed on silica gel and irradiated with light at wavelengths > 290 nm for 17 hours, 9.8% of the applied amount was degraded to CO₂ (Freitag et al., 1985).

In addition to the direct photolysis, the photodegradation may also follow an indirect photolysis by sensitisation by secondary reactions with OH- and O₂-radicals. The photolysis was studied in water solutions 600 ml at 4-20 mg/l irradiated for 3 hours. The photoreactivity in solutions in the presence of nitrite was observed to increase the photodegradation rate. The rate constant in pure water was 1.5*10^-4s^-1resulting in T½ to be 1.2 hours. In water added nitrite, the rate constant k was 3.1*10^-4s^-1and the resulting T½ 0.4 hours (Kotzias et al., 1982). The study was conducted under artificial conditions but indicates that photolysis may be affected by the contents in water. In the study, salts were used but other organic substances and organic matter may also affect the photodegradation rate.

Reference 2

Endpoint:

phototransformation in water

Type of information:

other: BUA report

Adequacy of study:

other information

Reliability:

other: BUA report

Rationale for reliability incl. deficiencies:

other: No reliability is given as this is a summary entry for the BUA report.

GLP compliance:

not specified

BUA report (1987):

The half life of 1,2,4-trichlorobenzene for direct photodegradation in surface water is calculated to be 450 years (Dulin et al., 1986). An accelerated degradation in the presence of nitrite could be shown (Kotzias et al., 1982).

Executive summary:

BUA report (1987):

The half life of 1,2,4-trichlorobenzene for direct photodegradation in surface water is calculated to be 450 years (Dulin et al., 1986). An accelerated degradation in the presence of nitrite could be shown (Kotzias et al., 1982).

Reference 3

Endpoint:

phototransformation in water

Type of information:

other: scientific judgement

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 surface water:
high:  4320 h (6 m)
low :   672 h (4 w)
Scientific judgement based upon estimated unacclimated aqueous aerobic biodegradation half-life.

________________________________________________________________________________

Half-lives in ground water:
high: 8640 h (12 m)
low : 1344 h (8 w)
Scientific judgement based upon estimated unacclimated aqueous aerobic biodegradation half-life.

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):

Degradation by direct photolysis is not expected to be essential because the maximum absorption value is 286 nm (Bayer spectral data). The half-life for sunlight photolysis in pure surface water at 40° latitude in summer was 450 years (Dulin et al., 1986). The recovery of 1,2,4-TCB from isopropanol solution in Pyrex glass tubing (with a cut-off at 285 nm) irradiated with 300 and 310 nm fluorescent lamps for 30 minutes was 89.4% under anaerobic conditions where O2 was replaced with N2 and 8.1% under aerobic conditions. The products of photodegradation were 1,3- and 1,4-dichlorobenzene (Akermark et al., 1976).

In a laboratory study using artificial light (high pressure mercury vapour lamp at wavelengths > 290 nm), the photodegradation was studied at a concentration of 2-5 ppm. 1,2,4-TCB was dissolved in distilled water and filtered river water. The photolytic half-life was estimated to be 16.7 hours in distilled water and 12.2 hours in river water. The photolysis products in river water were 1,4-dichlorophenol and 4-chlorophenol (Mansour et al., 1989).

The photolysis was studied by exposing 5 ml 1,2,4-TCB at 4 µg/ml at a distance of 30 cm from artificial light (Fluorochemical lamps 20W.2) at 25°C. After 144 hours, 0% was degraded (Kondo et al., 1988).

In a test where 1,2,4-TCB was adsorbed on silica gel and irradiated with light at wavelengths > 290 nm for 17 hours, 9.8% of the applied amount was degraded to CO2 (Freitag et al., 1985).

In addition to the direct photolysis, the photodegradation may also follow an indirect photolysis by sensitisation by secondary reactions with OH- and O2-radicals. The photolysis was studied in water solutions 600 ml at 4-20 mg/l irradiated for 3 hours. The photoreactivity in solutions in the presence of nitrite was observed to increase the photodegradation rate. The rate constant in pure water was 1.5*10^-4s^-1resulting in T½ to be 1.2 hours. In water added nitrite, the rate constant k was 3.1*10^-4s^-1and the resulting T½ 0.4 hours (Kotzias et al., 1982). The study was conducted under artificial conditions but indicates that photolysis may be affected by the contents in water. In the study, salts were used but other organic substances and organic matter may also affect the photodegradation rate.

 

BUA report (1987):

The half life of 1,2,4-trichlorobenzene for direct photodegradation in surface water is calculated to be 450 years (Dulin et al., 1986). An accelerated degradation in the presence of nitrite could be shown (Kotzias et al., 1982).

 

Howard, 1991:

Half-lives in surface water:
high:  4320 h (6 m)
low :   672 h (4 w)
Scientific judgement based upon estimated unacclimated
aqueous aerobic biodegradation half-life

________________________________________________________________________________

Half-lives in ground water:
high: 8640 h (12 m)
low : 1344 h (8 w)
Scientific judgement based upon estimated unacclimated
aqueous aerobic biodegradation half-life