A mixture of: thiobis(4,1-phenylene)-S,S,S',S'-tetraphenyldisulfonium bishexafluorophosphate; diphenyl(4-phenylthiophenyl)sulfonium hexafluorophosphate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The assessment of PBT/vPvB properties has been done on the basis of the data available from the testing programme as well as from some calculated approaches.

Persistence Assessment

The persistent assessment of the substance in water has been performed evaluating a biotic and an abiotic degradation pathway. Therefore a ready biodegradability study and an hydrolysis study have been carried out. In both experiments the substance resulted not degradable:

-       In the ready biodegradation study the substance resulted not inherently degradable, with a 10% of degradation after 28 days;

-       In the hydrolysis study the half life of the substance higher than 1 year at 50° C (at pH 4, 7 and 9).

No degradation products are expected as no hydrolytic behaviour has been recorded experimentally.

In soil, the substance is expected to have a high mobility, based on the value of the absorption/desorption coefficient (logKoc) of ranging from 1.89 and 2.21 (L/kg) at 21° C, depending by the pH (from 2 to 10).

Moreover the substance is not expected to enter into the atmosphere because of its low vapour pressure (0.0023 Pa at).

In addition, the exposure assessment shows that under adequate control measures, negligible releases to the environmental compartments are expected to occur during the life-cycle. As a result of the previous data, the substance will be mainly distributed in the aquatic compartment, although at not relevant doses (water solubility of 74 mg/L at), and it will not undergo to significant degradation. Therefore the substance meets the criteria of Annex XIII of Regulation EC 1907/2006 for the classification as “Persistent”.

Bioaccumulation Assessment

The substance is not expected to bioaccumulate in aquatic organisms, on the basis of logK_OWvalue of 1 at.

Toxicity Assessment

Results of the acute toxicity studies on aquatic organisms provided the following low L(E)C₅₀values: 4.9 mg/L, 0.8 mg/L, and 0.091 mg/L for fish (96 hours), daphnia (48 hours) and algae (72 hours), respectively. Although long-term data on aquatic organisms are not available, a very low NOEC (<0.01 mg/l) can beassumed basing on the low value of algal NOEC after 72 hours exposure (< 0.056 mg/L).

On the basis of the above consideration, it can be reasonably assumed that the substance meets the criteria of Annex XIII of Regulation EC 1907/2006 for the classification as “Toxic”.

Summary and overall Conclusions on PBT or vPvB Properties

On the basis of the available data, A mixture of: thiobis(4,1-phenylene)-S,S,S',S'-tetraphenyldisulfonium bishexafluorophosphate; diphenyl(4-phenylthiophenyl)sulfonium hexafluorophosphate, although environmental emissions are negligible, will mainly distribute into the aquatic compartment, where it is not expected to degrade neither by biotic nor abiotic pathways. In the aquatic environment, however, the substance is not expected to bioaccumulate in the aquatic organisms. The substance is however toxic for aquatic organisms as indicated by the short-term ecotoxicity studies on fish, crustaceans and algae.

In conclusion, considering al the available data, the substance meets the criteria of Annex XIII of Regulation EC 1907/2006 for the classification as “Persistent” and “Toxic”, but it does not meet the criteria for the “Bioaccumulation” endpoint. Therefore the substance is not considered to be neither a PBT nor a vPvB substance.

Emission Characterisation

Because the substance does not fulfil the PBT and vPvB criteria, no emission characterisation is performed. Furthermore on the basis of the risk characterisation, the risk is evaluated as adequately controlled during all steps of life cycle.