Dialuminium tris[2-(2,4,5,7-tetrabromo-6-oxido-3-oxoxanthen-9-yl)benzoate]

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Here follows a compiled description of the PBT assessment:

Persistence assessment

The tested substance fulfils the P criterion within Annex XIII based on the assessment that here follows:

 

                     Abiotic degradation

Half-life of hydrolysis of test chemical Di aluminium tris [2-(2,4,5,7-tetrabromo-6-oxido-3-oxoxanthen-9-yl)benzoate]is predicted using OECD QSAR tool box v.3.3 using log Kow as primary descriptor. The half of Hydrolysis of chemical Di aluminium tris [2-(2,4,5,7-tetrabromo-6-oxido-3-oxoxanthen-9-yl)benzoate] estimated is 106.422 days. Since the value of half-life of hydrolysis is more than 10 days test chemical Di aluminium tris [2-(2,4,5,7-tetrabromo-6-oxido-3-oxoxanthen-9-yl)benzoate] have negligible hydrolysis in water.

HYDROWIN™ estimates aqueous hydrolysis rate constants and half-lives for the following chemical classes: esters, carbamates, epoxides, halomethanes, selected alkyl halides, and phosphorus esters. Estimates rate constants for acid- and base-catalyzed hydrolysis. In addition, Hydrowin was used to calculate the half-life and the degradation rate for the read-across compound (tautomeric index 0.5 to CAS 15876-39-8) with CAS number 12224-98-5. The hydrolysis rate was calculated to 3.776E-002 L/mol-sec at pH above 8 and above 25 degrees Celsius. The half-life at pH 8 was 212.462 days and the half-life at pH 7 was 5.817 years (EPI suite version 4.1, 2017). Hence, this compound was estimated to hydrolyse slowly since the hydrolysis half-life is above 90 days. Thereby making this a compound that is prone to persist in the environment.

 

                     Biotic degradation in water

The technical dossier of CAS 15876-39-8 contains the following estimation models for biotic degradation:

1)     Biodegradability of Dialuminium tris(2-(2,4,5,7-tetrabromo-6-oxido-3-oxoxanthen-9-yl)benzoate) is predicted using QSAR toolbox version 3.4 with log Kow as the primary descriptor (2017). Test substance undegoes 6.4% degradation by BOD in 28 days.The test chemical Dialuminium tris(2 -(2,4,5,7 -tetrabromo-6 -oxido-3 -oxoxanthen-9 -yl)benzoate) was estimated to be not readily biodegradable in water. (OECD QSAR prediction, SSS Europe AB, Lund, Sweden, 2017).

2)     Aerobic degradation of Eosin was studied by a modification of the OECD Guideline 302 B used as the static test method. The main variations from the OECD method were the extension of the test period from 28 to 42 days and, because the test time was relatively long, the weekly feeding of the sludge by most of the participating laboratories. The sources of the activated sludge were treatment plants conveniently located to the laboratories carrying out the test. Each week 100 mg/l of yeast extract was used for the feeding of the test inoculum. Conc. of the test chemical and inoculum used for the study was 100 mg/l and 0.5g/l, respectively. Detection method involve the determination of extinction at absorption maximum of 412 nm and DOC (dissolved organic carbon). The DOC elimination of the test chemical was found to be -3% after 42 days. Based on the criteria for evaluation of the static test results, Acid red 87 was in Category D, which signifies that the test chemical was found to not readily biodegradable in nature at the end of 42 days.

3)     The aim of the study was to investigate biodegradation of the xanthene dyes using anaerobic granular sludge. More specially, the biodegradation of the read-across compound Eosin Y with CAS 17372-87-1 was herein investigated. Non-acclimated anaerobic granular sludge had been collected from a regular wastewater treatment plant in Portugal. The suspended solids content of the biomass was determined to be 0.094 g VSS/g. The substrate and macronutrients in a total volume of 50 ml of medium was buffered at pH of 7 before initiation of the incubation period. The dye concentration used in the test was 0.3 mM. The incubation temperature was 37°C. One rotated the used bottles at 120 rpm. The total incubation period was 1 day. Colour decrease was monitored spectrophotometrically in a 96-well plate reader. The decolourization (%) of Eosin Y was 7% after 1 day of incubation (exact incubation time not mentioned). The incubation time was considered to be too short in order to be able to evaluate whether this chemical could be inherently degradable under anaerobic conditions. Moreover, the observed decolourisation of Eosin Y could have been due to adsorption to the biomass and not biodegradation.

4) The biodegradability of phloxine B was studied using different methods such as aerobic degradability, Warburg method and BOD measurement. Return activated sludge was obtained from the municipal sewage treatment plant, Nakahama, Osaka. Synthetic sewage and Seeded Dilution water were also prepared. 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 of 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. 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.

The percentage degradation of test substance 2',4',5',7'-tetrabromo-4,5,6,7-tetrachloro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthen]-3-one (Phoxine B) was determined to be 0% by using Test mat. analysis and Oxygen uptake in 10 days. Thus, based on percentage degradation test chemical 2',4',5',7'-tetrabromo-4,5,6,7-tetrachloro-3',6'-dihydroxy-3H-spiro [2-benzofuran-1,9'-xanthen]-3-one was considered to be not readily biodegradable in nature. (The Journal of Toxicological Sciences, Vol.3, 193 -204 and 205-214, 1978).

Adsorption

KOCWIN™ program estimates the organic carbon-normalized sorption coefficient for soil and sediment; i.e. KOC. KOC was estimated using two different models: “the Sabljic molecular connectivity method” with improved correction factors and the traditional method based on log KOW. The logarithmic Koc for CAS 15876-39-8 was calculated to 4.221 (molecular connectivity method) and 3.229 (Kow method). The compound was based on the Koc predicted to have strong sorption to soil and sediment. The risk of migration to groundwater should therefore be low.

 

Bioaccumulation assessment

The tested substance does not fulfil the B criterion within Annex XIII based on the assessment that here follows:

 

BCFBAF™, previously called BCFWIN™, estimates fish bioconcentration factor (BCF) and its logarithm using two different methods. The first is the traditional regression based on log KOW and any applicable correction factors, and is analogous to the WSKOWWIN™ method. The second is the Arnot-Gobas method, which calculates BCF from mechanistic first principles. BCFBAF also incorporates prediction of apparent metabolism half-life in fish, and estimates BCF and BAF for three trophic levels.

 

The logarithmic octanol-water partition coefficient (log Kow) was calculated to 4.8 (estimated by KOWWIN™ estimates the log, log KOW, of chemicals using an atom/fragment contribution method.). The regression based log Kow was for CAS no. 15876-39-8 calculated to 0.5 L/kg wet-weight (BCF=3.162 L/kg). The half-life was calculated to 0.9287 days. The log BCF based on Arnot-Gobas method was calculated to 2.564 L/kg wet-wt.The compound was therefore predicted to be of low concern for bioaccumulation in fish (calculated in EPI suite version 4.1, 2017).

 

 

Toxicity assessment

The tested substance does not fulfil the T criterion within Annex XIII based on the assessment that here follows:

 

CMR classification

The chemical unfulfilled the following classifications: H350, H372, H373, H340 and H360 based on assessment by PhD Martina Holst at SSS Europe AB, Sweden, 2017.

 

Ecotoxicity

The available short-term eco-toxicity assessment for fish, invertebrates and algae for CAS 15876-39-8 indicates the key LC/EC50 value to be > 100 mg/L indicating that the substance is likely to be non-hazardous at environmentally relevant concentrations and can be considered as not classified as as per the CLP criteria. All available short-term ecotoxicity exposure assessment for read-across substances Eosin Y (CAS: 17372-87-1) and Phloxine B (CAS: 18472-87-2) are also above 100 mg/L. These values suggest classification for aquatic toxicity will not be applicable as per Annex XIII criteria for all of the tropic levels and the same is based on the above mentioned estimation studies.

 

 

Overall conclusion about Persistence, Bioaccumulation and Toxicity (PBT).

 

Based on critical, independent and collective evaluation of only the information summarized herein (nothing else), the tested chemical substance only fulfils the P criterion within Annex XIII. Hence, the tested compound has not been classified as a PBT compound within Annex XIII.