Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Hydrolysis

No significant hydrolysis was detected at pH values of 4, 7 ,and 9 at 50 °C after 5 days. The half life at ambient temperature was estimated to be greater than 1 year.

Phototransformation in water

In dilute solutions and in presence of sunlight,stilbene fluorescent whitening agentsundergo reversible isomerization of the stilbene moiety. In this process, two isomeric forms occur. The E- and Z-isomers are under environmental conditions in equilibrium within a few minutes. The parent substances used as fluorescent whitening agent consist of the E-isomer, while isomerization to the Z-form leads to complete loss of fluorescence. Two studies demonstrate that at solar latitude 60°, at 25°C, and on surface layer depths of 0 to 5m the remaining E-isomer fraction is 13.9 to 9.5 and 17.8 to 13.3, respectively. The preceding isomer equilibrium influences the photo-degradation rate. The half-life for photo-oxidation in natural water (Lake Greifensee) was measured for the same substances and under the same light conditions on the surface layer: 278 min and 313 min. The experimental kinetic data are used to calculate photochemical half-lives as a function of surface layer depth, optical density of the water, and time of the year.

Based on measured kinetic parameters and the quatum yield, photochemical half-lives in three Swiss lakes are calculated according to GCSOLAR as a function of surface layer depth and time of the year (Kramer, 1996). Both substances degrade with nearly identical half-lives. Therefore, it is assumed that all substances of the category follow the same photolytical processes and areeffectively degraded in surface waters.

A RIVM report (Plassche et al., 1999) shows that stilbene fluorescent whitening agents will be effectively degraded by photochemical processes. It is shown that first photoisomerization occurs, followed by photodegradation. Rates are rapid: half-lives are in order of 1 hour or even less. The US EPA property estimation program AOPWIN v 1.92 calculates a Half-Life of 6 hours (Hydroxyl Radicals reaction) and 2 hours (Ozone reaction) for a stilbene principle structure.

UV-VIS spectrum of the test item showed an absorption band with a maximum located at 350 nm. Therefore direct photo degradation is very likely.

Biodegradation in water: screening test

In a test for ready biodegradability according to OECD Guideline 301 D (Ready Biodegradability, Closed Bottle Test, activated sludge, domestic, non-adapted) 23 % of the test material degraded in 28 days.

The test material is considered not readily biodegradable by non-adapted domestic activated sludge.

Biodegradation in water and sediment: simulation test

No data on the biodegradation in sediments and surface water are available for the test item. However, further biotic degradation testing shall be proposed if the chemical safety assessment according to Annex I indicates the need to investigate further degradation of the substance and its degradation products. The test substance were found to be non-biodegradable in a study concerning ready biodegradability. It is not expected that the DT90 of the test item in an OECD 308 or 309 would indicate a rapid biodegradation in sediment and surface water e.g. < 100 d. Based on these facts the simulation tests according OECD 308 and 309 are not warranted.

Biodegradation in soil

No data on the biodegradation in soil are available for the test item (stilbene fluorescent whitening agent). However, further biotic degradation testing shall be proposed if the chemical safety assessment according to Annex I indicates the need to investigate further degradation of the substance and its degradation products. The test substances were found to be non-biodegradable in studies concerning ready biodegradability. It is assumed that the test substance is not biodegradable in simulation tests either. Therefore, simulation studies in soil are not provided for the stilbene fluorescent whitening agent.

Nevertheless a RIVM report (Plassche et al., 1999) shows that stilbene fluorescent whitening agents will be effectively degraded by photochemical processes (see also IUCLID Chapter 5.1.3). It is shown that first photoisomerization occurs, followed by photodegradation. Rates are rapid: half-lives are in order of 1 hour or even less. The US EPA property estimation program AOPWIN v 1.92 calculates a Half-Life of 6 hours (Hydroxyl Radicals reaction) and 2 hours (Ozone reaction) for a stilbene principle structure.

UV-VIS spectrum of the test item showed an absorption band with a maximum located at 350 nm. Therefore direct photo degradation is very likely.

Bioaccumulation

Based on the high molecular weight and the excellent solubility in water a significant potential of bioaccumulation is not anticipated. Due to the fact that the partitioning coefficient octanol water is negative a bioconcentration and bioaccumulation is not expected.

Adsorption / desorption

In a study on adsorption/desorption in soil according to OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method) the adsorption coefficient Koc was determined as 5580 (log Koc: 3.75). The results of the adsorption/desorption study indicate that the test material is tightly bound to soil components, if exposure should occur.