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Environmental fate & pathways

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Biodegradation in water:

Additional information

Biodegradation in water:

Predicted data from OECD QSAR tool box.v.3.3 for target chemical 3,4,5,6-tetrachloro-2-(2,4,5,7-tetrabromo-3,6-dihydroxyxanthen-9-yl)benzoic acid, aluminium salt ( CAS no. 84473 -86 -9) and supporting weight of evidence studies for target chemical’s closest read across chemicals with log Kow as a primary descriptor and structurally similar read across chemical were summarized as below.

Biodegradability of test chemical was predicted using OECD QSAR tool box v.3.3 using log kow as a primary descriptor. The percent biodegradability of test chemical 3,4,5,6-tetrachloro-2-(2,4,5,7-tetrabromo-3,6-dihydroxyxanthen-9-yl)benzoic acid, aluminium salt ( CAS no. 84473 -86 -9) estimated was 0.20 % by taking BOD parameter into consideration and microorganism as a inoculum in 28 days. The percent degradation is very less so it is concluded that this test chemical is not readily biodegradable.

 

The supporting weight of evidence study from authoritative database ( J check, 2017) for read across chemical pentabromophenol ( CAS no. 608-71-9) was carried out to test biodegradation. Biodegradation was analysed by using BOD and HPLC parameter and by taking sludge as inoculums at 30 mg/L concentration. The initial concentration of read across chemical was 100 mg/L and study design is of standard type. After 4 weeks (28 days) read across chemical showed 0% biodegradation by BOD and 1 % by HPLC so it is concluded that read across chemical pentabromophenol is not readily biodegradable

 

Another supporting weight of evidence study from same source as stated above ( J check 2017) was performed for read across chemical 5-chloro-2-(2,4-dichlorophenoxy)phenol (CAS no.3380-34-5) to test biodegradation by taking activated sludge as a inoculums at 30 mg/L concentration . Biodegradation was analyzed by using two parameters BOD and HPLC. The initial concentration of test chemical was 100 mg/L and study design is of standard type. After 4 weeks( 28 days) read across chemical 5-chloro-2-(2,4-dichlorophenoxy)phenol showed 0% and 1% biodegradation by BOD and HPLC parameters respectively. So it is concluded that this read across chemical 5-chloro-2-(2,4-dichlorophenoxy)phenol is not readily biodegradable.

 Last study was done from the Journal of Toxicological Sciences, Vol.3 , 193 -204, 1978 for structurally similar read across chemical phloxine B in this study the biodegradability of phloxine B was studied using methods: Aerobic degradability, Warburg method and BOD measurement. Return activated sludge was obtained from the municipal sewage treatment plant, Nakahama, Osaka. Synthetic sewage preparation: Glucos, peptone and potassium dihydrogen phosphate, 30g each, were dissolved in 1 liter water and the pH was adjusted to pH 7.0 with sodium hydroxide. Seeded Dilution water: To 1 liter, 10 ml of supernatant of sludge was added. Aerobic biodegradation assay: To 750ml of sludge (MLSS ca, 3,000 ppm) 250 ml of O.03 M dye solution was added, and bubbled with air sufficiently at 20°C. 5ml sample was taken out once a day. After sampling 5ml synthetic sewage was added to the mixture. Each sample was filtered through filter paper and diluted twenty times prior to the spectrophotometric measurement at the absorption maximum within the visible range. The decrease of dyes concentration was expressed in terms of percent to the initial absorption. The experiment was carried out for 10 days. Oxygen uptake of sludge [Warburg Method]- 2.0 ml of sludge, 0.2 ml of 1000 ppm dye solution, and 0.2 ml of 20% potassium hydroxide were pipetted into the vessel, the side arm and central well, respectively. The sludge and the dye solution were mixed and the vessel was shaken at 25°C. The oxygen uptake was measured. The oxygen uptake by sludge alone was subtracted from those by dyes addition.

Determination of BOD – Dye solution (10, 20, and 40 ppm) were prepared with the seeded dilution water and kept at 20°C (Japanese Industrial Standards Committee, 1971). The dissolved oxygen contents were measured by a dissolved oxygen meter, because of the coloration of the solutions.

As there is no regulation on the color of the effluent by the Water Pollution Control Law, discharge of coloring materials is regulated by only BOD OR COD. The COD, BOD and absorbance at 245 and 545 nm (representing ultraviolet and the visible absorbance) of Phloxine B was studied. During 10 days of the aerobic experiment, the absorbance of dye solution was measured once day for 10 days. Food Red No. 104 was scarcely decreased. Free acids of Red No.104, was precipitated due to the slight acidity (pH 6-7) of the solution. Based on the results obtained from the studies, it can be concluded that Phloxine B is not readily biodegradable under aerobic conditions. Phloxine B was determined to be non- biodegradable in the anaerobic test also performed.

 

On the basis of above results of target chemical 3,4,5,6-tetrachloro-2-(2,4,5,7-tetrabromo-3,6-dihydroxyxanthen-9-yl)benzoic acid, aluminium salt from OECD QSAR tool box v.3.3 and its supporting weight of evidence studies from authoritative database and Journal of Toxicological Sciences it is concluded that this test chemical 3,4,5,6-tetrachloro-2-(2,4,5,7-tetrabromo-3,6-dihydroxyxanthen-9-yl)benzoic acid, aluminium salt is not readily biodegradable.