(1-λ1-oxidanyl-2,2,6,6-tetramethylpiperidin-4-yl) benzoate

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The environmental/toxicological assessment shows that the substance 4-Hydroxy-TEMPO Benzoate (CAS No: 3225-26-1) does not meet the criteria for classification as PBT or vPvB.

 

Persistence (P)

With respect to persistency, a reliable ready biodegradability screening test with the related substance (4-Hydroxy-TEMPO; CAS No 2226-96-2) indicates that 4-Hydroxy-TEMPO-Benzoate is also unlikely to be readily biodegradable under these stringent test conditions. This is an indication of potential P or vP. However, 9% biodegradation was observed after 28 days in this study indicating that some biodegradation has occurred and that biodegradation would be expected under relevant environmental conditions. The predicted (EPI suite) Biowin 3 degradation rate is 2.32 (weeks - months) and is above the 2.2 months probability threshold and is a further indication of P or vP. Other EPI suite predictions are slightly contradictory. The Biowin 2 probability is above 0.5 (estimated probability 0.81) giving an indication that the substance will biodegrade fast. Based on the screening data and EPI suite predictions the substance may be classified as P but is unlikely to be vP.

 

Bioaccumulation (B)

The substance has a low Log Kow measured at: Log Kow 3.02. This low Log Kow (below the screening criteria of log Kow >4.5 for B) is an indication that the substance is likely to remain in water, rather than accumulating in lipid-rich tissues, indicating it should not be considered B or vB. In addition the bioaccumulation factor (predicted from valid EPI suite) is extremely low at 45.94 L/kg. This is well below the > 2000 L/kg threshold which again indicates not B or vB.

 

Toxicity (T)

Results are available from reliable aquatic screening tests (daphnia, algae and fish) on the read-across substance (4-Hydroxy-TEMPO) that shows the EC50 concentrations are all well in excess of the <0.1 mg/L criterion to be classed as T. 4-Hydroxy-TEMPO-Benzoate is not classified as carcinogenic (cat 1A or 1B), cell mutagenic (category 1A or 1B) or toxic for reproduction (category 1A, 1B or 2) in accordance with EC No. 1272/2008 (CLP). However, there is evidence of Specific Target Organ Toxicity from repeated exposure (STOT RE, category 2), based on a LOAEL of 200 mg/kg bw/day seen in a 28-day oral repeated dose study on the read-across substance (4-Hydroxy-TEMPO). This is an indication that 4-Hydroxy-TEMPO-Benzoate should be considered as potentially T.

 

Conclusion

Although the substance is considered as potentially persistent (P) and toxic (T), it clearly does not meet the criteria to be B or vB. Therefore 4-Hydroxy-TEMPO-Benzoate should not be considered as a PBT or vPvB substance.

Likely routes of exposure:

The substance is not classified as PBT therefore there route of exposure it is not relevant.