Sodium benzenesulphinate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of Sodium benzenesulphinate for effects in the environment:

 

The chemical Sodium benzenesulphinate (CAS no. 873 -55 -2) is used as a pharmaceutical intermediate and for chemical synthesis. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for Sodium benzenesulphinate. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.

 

 

Persistence assessment

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

 

Biotic degradation

Various experimental studies for the target compound sodium benzenesulfinate (CAS No. 873-55-2) were reviewed for the biodegradation end point which are summarized as below:

 

In an experimental study from peer reviewed journal (H A Painter and E F King, 1986), biodegradation experiment was conducted for 28 days according to OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test). Sewage effluent, MITI or activated sludge was used as a test inoculum. Concentration of sludge used was 0.5 ml effluent /l or 30 mg activated sludge solids/l and initial test substance conc. used was 10-50 mg/l based on DOC. The study was performed at a temperature of 20 or 25°C. Test chemical was not adequately removed in the 28-day period when the inoculum used was sewage effluent, whereas test chemical was removed to a much larger extent when activated sludge was used as the inoculum. The percentage degradation of test substance was determined to be16, 98 and 85% by using DOC removal parameter in 28 days by using sewage effluent, MITI and activated sludge as a test inoculum. Thus, based on percentage degradation, test substance sodium benzenesulfinate was considered to be readily biodegradable in nature.

 

In a supporting data, biodegradation experiment was conducted for 28 days according to EEC Respirometric method for evaluating the percentage biodegradability of test substance sodium benzenesulfinate (CAS no. 873-55-2) (H A Painter and E F King, 1986). Activated sludge was used as a test inoculum. Concentration of sludge used was 30 mg activated sludge solids/l and initial test substance conc. used was 100 mg/l based on test material. The study was performed at a temperature of 20 or 25°C. In screening tests, 60% ThOD and 70% DOC removal was achieved in a ’10 -day window’. In screening tests, 60% ThOD and 70% DOC removal was achieved in a ’10-day window’. The percentage degradation of test substance was determined to be 70 and 100% by ThOD and DOC removal parameter after 28 days in EEC respirometric method, whereas 95 and 97% degradation of test substance was determined after 28 days in MITI respirometric method. Thus, based on percentage degradation, test substance sodium benzenesulfinate was considered to be readily biodegradable in nature.

 

Another supporting biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test substance sodium benzenesulfinate (CAS no. 873-55-2) under aerobic conditions at a temperature of 20°C (J. STRUIJS AND J. STOLTENKAMP, 1990). Activated Sludge was used as a test inoculum obtained from local sewage treatment plant (de Bilt, The Netherlands). Concentration of inoculum i.e, sludge used was 3.9 mg/l and initial test substance conc. used in the study was 10 mg/l, respectively. Test and blank solutions were transferred to caliberated 120 ml serum bottles in a headspace/solution ratio ½. The serum bottles were sealed with three-part caps consisting of butyl rubber septa, pierceable, and closed aluminium screw tops. Incubations were carried out in the dark at 20°C on a rotary shaker (120 rpm). Weekly, part of the bottles were sacrificed for CO2 headspace analyses and if possible, DOC measurements of the solution. The CO2 concentrations in the headspace of the acidified solution were related to the corresponding blank from which the level of mineralization was calculated as percent ThCO2 (theoretical amount of carbon dioxide of the compound). The test was terminated when percent ThC02 exceeded 70%. For the blank control, a series containing a mineral solution with inoculum was prepared. DOC measurements of the soluble test compounds were carried out with a Technicon AA” auto-analyzer on Day 0 and after each carbon dioxide analysis. Samples were centrifuged at 5000g before DOC was measured. The percentage degradation of test substance was determined to be 28 – 35% degradation by ThCO2 parameter in 28 days. Thus, based on percentage degradation, test substance sodium benzenesulfinate was considered to be inherently biodegradable in nature.

 

In a supporting study from authoritative database (J-CHECK, 2017), biodegradation screening test was conducted for 21 days for the test substance sodium benzenesulfinate (CAS no. 873-55-2). Concentration of inoculum i.e., sludge used was 100 mg/l and initial test substance conc. used in the study was 30 mg/l, respectively. The percentage degradation of test substance was determined to be 99, 81 and 67% by BOD, TOC and UV-Vis parameter in 21 days. Thus, based on percentage degradation, test substance sodium benzenesulfinate was considered to be readily biodegradable in nature.

 

For the target chemical sodium benzenesulfinate (CAS no. 873-55-2), biodegradation study was conducted for 30 days for test substance sodium benzenesulfinate (J. Struijs and R. Van Den Berg, 1995). The study was performed according to OECD Guideline. Test inoculum activated sludge was obtained from communal waste water treatment plant. The percentage degradation of test substance was determined to be 100% degradation in 30 days. Thus, based on percentage degradation, test substance sodium benzenesulfinate was considered to be readily biodegradable in nature.

 

Although 1 study from peer reviewed journal (J. STRUIJS AND J. STOLTENKAMP, 1990) indicate that the chemical is inherently biodegradable in nature, based on the overall reported results for target chemical sodium benzenesulfinate (from peer reviewed journal and authoritative database J-CHECK), it can be concluded that the test substance sodium benzenesulfinate can be expected to be readily biodegradable in nature.

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 67.5%). In soil, Sodium benzenesulphinate was expected to have negligible to rapid mobility based upon an estimated Log KOC in the range 0 - 1.43. The half-life in soil (30 days estimated by EPI suite) indicates that the chemical is not persistent in soil and the exposure risk to soil dwelling animals is moderate to low.

 

If released in to the environment, 32.4 % of the chemical will partition into water according to the Mackay fugacity model level III in EPI suite version 4.1 (2016). However, the half-life (15 days estimated by EPI suite) indicates that the exposure risk to aquatic animals is moderate to low.

 

Moreover, its persistent characteristic is only observed in the sediment compartment but Fugacity modelling shows that sediment is not an important environmental fate (less than 1% when estimated by EPI Suite version 4.1).

 

Hence it has been concluded that Sodium benzenesulphinate is not persistent in nature.  

 

 

Bioaccumulation assessment

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

 

The estimated BCF value for the substance is in the range 1.0 – 4.49 L/kg wet wt. and the estimated log octanol-water partition coefficient (log Kow) was determined to be in the range – 3.04 to -3.54 which is less than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a low risk for the chemical to bioaccumulate in fish and food chains.

 

Toxicity assessment

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

 

Mammals

The tested chemical is regarded to be not classified for carcinogenicity, mutagenicity and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1(oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).

 

Aquatic organisms

 

All of the available short-term eco-toxicity estimation for invertebrates and algae for the substance indicates the LC50/EC50 value to be > 100 mg/L. These value suggest that the substance is likely to be non-hazardous at environmentally relevant concentrations and can be considered as not-classified as per the CLP regulation.

 

There are no available long-term toxicity evaluations for Sodium benzenesulphinate. By speculation, long-term NOEC for aquatic organisms were not expected for the substance at concentration below 0.01 mg/L based on the data mentioned above.

 

The chemical was therefore not considered as hazardous to aquatic environments as per the criteria set out in Annex XIII.

 

Conclusion

Based on critical, independent and collective evaluation of information summarized herein, the tested compound does not fulfil the P, B and T criterion and has therefore not been classified as a PBT compound within Annex XIII.