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Environmental fate & pathways

Phototransformation in water

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Reference
Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
168 hours
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The result is within the experimental error of 10% of the method of analysis.
Study type:
direct photolysis
Qualifier:
no guideline followed
Principles of method if other than guideline:
Photoirradiation with a mercury lamp emitting wavelenghts above 290 nm of Dechlorane Plus in aqueous solution with 5% acetonitrile for 168 hours and comparison with a similar solution kept in the dark. Analysis of both solutions by gas-liquid phase chromatography with electron capture.
GLP compliance:
no
Radiolabelling:
no
Analytical method:
other: gas-liquid phase chromatography with electrone capture
Details on sampling:
The water samples were extracted with methylene chloride and hexane, and the extract was reduced in an evaporator.
Buffers:
none
Light source:
other: mercury lamp
Light spectrum: wavelength in nm:
> 290
Details on light source:
450 watt mercura lamp with a borosilicate immersion wall serving as a filter allowing only wavelengths avobe 290 nm to reach the solutions.
Details on test conditions:
No further details reported.
Duration:
168 h
Reference substance:
no
Dark controls:
yes
Computational methods:
none
Test performance:
The extracts were reduced in an evaporator with a high uncertainty of 10% thus leading to an internal error in the test system of at least 10%. The initial concentration was 1 ppm.
Remarks:
not determined
% Degr.:
< 10
Sampling time:
168 h
Test condition:
168 h irradiation at > 290 nm
Rate constant (for indirect photolysis):
< 6 other: 1/10000 / h
Predicted environmental photolytic half-life:
> 48 days
Transformation products:
yes
Details on results:
One photolysis product was found at less than 10% of the total concentration. This product was not identified.
Results with reference substance:
none

One photolysis product of Dechlorane Plus was detected at less than 10% of the total concentration, but the internal error of the method of analysis was reported at 10% of the total concentration.

Validity criteria fulfilled:
no
Conclusions:
The amount of produced degradation product is quantitatively not reliable, as the detected concentration was within the internal error of the method of analysis. The amount of residual non-degraded substance is partly reliable with a relatively large range of about 80 - 100%.
Executive summary:

Dechlorane Plus was investigated for photodegradation by irradiation at wavelenghts above 290 nm for 168 hours in aqueous solution at a concentration of 1 ppm under addition of 5% acetonitrile to improve water solubility. Less than 10% of the substance was degraded within 168 hours producing one degradation product which was not identified. The predicted half-life was calculated to be above 48 days.

Description of key information

Based on a study using UV radiation of dissolved DP in water with 5% acetonitrile, there is some indication for photodegradation in water but considering the error margins of the study, the results cannot be considered as conclusive. The phototransformation in water rate constant was calculated as <6 x 10-4 h-1, equivalent to a half-life of >48 d.

Key value for chemical safety assessment

Additional information

In Chou et al.(1979), phototransformation of the substance in water (aqueous solution with 5% acetonitrile) was determined by the use of a mercury lamp emitting wavelengths of >290 nm for 168 h, which was compared with a similar solution, kept in the dark (control). Both solutions were analysed using GC with electron capture. The extracts were reduced in an evaporator with uncertainty of 10% thus leading to an internal error in the test system of at least 10%. One photolysis product of Dechlorane Plus was detected at less than 10% of the total concentration, but as the internal error of the method of analysis was reported at 10% of the total concentration the result can only be seen as indicative. The degradation product was not identified. The phototransformation in water rate constant was calculated as <6 x 10-4h-1, equivalent to a half-life of >48 d.