sodium 3-[(3,4-dicyanophenyl)thio]propane-1-sulfonate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

A PBT/vPvB assessment of test substance could not be carried out acording to theREACH Annex XIII as the required experimental data is not available. However, based on data that is available for the analogous substamce that is very similar it is possible to assess the PBT/vPvB properties of the test substance with a level of certainty which, although not meeting the Annex XIII requirements, can be considered an acceptable for a substance such as the test substance registered at REACH Annex VIII level.  

 

PBT/vPvB criteria and justification

 

Persistence Assessment

 

The analogous test substance showed < 6.9 % degradation in a ready biodegradability test and does not meet the criteria for being classed as readily biodegradable. 

 

At pH 4.0 and pH 7.0 the analogous test substance under goes less than 10% hydrolysis after 5 days at 50°C which indicates a half-life of in excess of one year at 25°C. At pH 9.0 the test substance underwent approximately 30% hydrolysis after 5 days at 50°C giving it an estimated half-life of 9.9 days; however, at a more environmentally relevant 5 days at 20°C there was < 10% hydrolysis. These results suggest that although the analogous test substance is susceptible to hydrolysis, in the natural environment this will probably be limited to specific conditions and environments.

 

There is no other information on whether the analogous test substance will be susceptible to other abiotic degradation processes such as the effects of light or pH. However, given its structure it is not expected to undergo significant degradation from natural processes. In a storage stability test it was determined that it was stable for at least two years. 

 

In conclusion, the analogous test substance can be expected to be resistant to degradation in the environment and it is considered to be persistent according to the criteria set out in REACH Annex XIII. Due to the very close similarites of the test Substance S200437 to the analogous test substance it is fully expected that the test substance will behave in the same manner as the analogous test substance.

 

Bioaccumulation Assessment

 

The test suibstanceis a relatively low molecular weight molecule (288 as lithium salt) and therefore its size is unlikely to present a significant barrier to absorption across biological membranes. However, the test substance has a low log P value -2.32 and is very water soluble which will retard absorption across biological membranes. These characteristics also mean that when in the body it will not easily partition into, or be retained by body fats making bioaccumulation unlikely.

 

The test substance undergoes limited hydrolysis at pH 4 and pH 7; however, at pH 9 for 5 days at 50 °C approximately 30% hydrolysis occurs. Based on the hydrolysis results, it is possible that the test substance may be susceptible to at least a degree of hydrolysis in the lower intestine where up to ca. pH 8 could be encountered following oral administration.

 

The test substance contains a water soluble sulphonic acid and two cyano groups which are likely to aid excretion and also metabolism of the molecule by cytochrome P450 enzyme metabolising system. Hence, in organisms such as mammals and fish with significant P450 metabolising systems the test substance is expected to undergo a degree of metabolism resulting in breakdown of the molecule and ultimate excretion. In a repeated dose developmental toxicity screening study histopathological changes were observed in the kidneys indicating that the test substance and/or its metabolite(s) are present in this organ following exposure and indicating it is a route of excretion.  

 

In conclusion, the test substance is not considered to be bioaccumulative according to the criteria set out in REACH Annex XIII.

 

Toxicity Assessment

 

The test substance has not produced any significant adverse toxicity to organisms in any mammalian toxicity tests or ecotoxicity tests and has not been classified as hazardous according to CLP/GHS. A repeated dose developmental toxicity screening study showed no concerns from repeated exposure or for reproductive effects.

In conclusion, the test ubstanceis not considered a toxic compound according to the criteria set out in REACH Annex XIII.

 

8.1.2. Summary and overall conclusions on PBT or vPvB properties

 

Data available on the test substance does not meet the specific criteria to allow full direct comparison with the criteria detailed in REACH Annex XIII. However, what data is available indicates with a high degree of certainty that the test ubstance does not meet the criteria for classification as a PBT because it does not fulfil all three criteria covering persistence, bioaccumulation and toxicity. Additionally, as the test substance is not both persistent and bioaccumulative it does not meet the criteria for classification as a vPvB.

 

Overall conclusion:

Based on the assessment described in the subsections above the test substance is not a PBT or vPvB substance.