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PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

8.1.1. Persistence Assessment

Two ready biodegradation studies have been performed on 2,2,4-trimethylpentanediol (TMPD). The key study was conducted using the DOC Die-Away Test (OECD Guideline 301A). In that study a lag phase of approximately 3 - 4 days occurred before biodegradation reached 10% in both test vessels. The test substance reached 91% and 98% degradation within the subsequent 10-day window. At test end, the test substance showed 99% and 100% degradation (as measured by loss of DOC). In the second study based upon CO2 evolution an average of 87.8% biodegradation was observed within 28 days. Based upon the results of these studies the substance meets the criteria to be considered readily biodegradable.

In addition to the ready biodegradation studies, a wastewater treatment plant simulation study was conducted using a Semi-Continuous Activated Sludge (SCAS) Removability Test. This test is designed to determine the removability of the test substances in the SCAS test system, as measured by soluble organic carbon (SOC). In this study the sludge organisms were incrementally acclimated to TMPD over 7 days followed by a 7 day test period. During the 7 day test period SOC was measured in samples removed from the control and test substance replicates. The volume of sample removed was replaced with a comparable volume of fresh influent containing the test substance and synthetic sewage and the process was repeated each day. The result of these daily analyses over the 7 day test period was a daily mean removal of 101% with a 95% confidence interval of ± 1.6%.

Based upon these studies TMPD would not be considered as persistent according to REACH Annex XIII regulation and would not be considered as a P or vP substance.

8.1.2. Bioaccumulation Assessment

A measured bio oncentration factor (BCF) in an aquatic species is not available for TMPD. However, the measured partition coefficient value is log Pow = 1.25. This value indicates a low potential to bioaccumulate (see Column 2 of REACH Annex IX and Annex XIII of REACH). Therefore the substance is not considered to meet the B criterion.

8.1.3. Toxicity Assessment

Reliable acute aquatic toxicity test data are available for TMPD for the three principal trophic levels: primary producers, represented by algae; plant eating animals, represented by daphnids; and predators, represented by fish (see Guidance on Information Requirements and Chemical Safety Assessment. Chapter R.10, May 2008). The results of these studies suggest that the T criterion is not applicable for this substance.

8.1.4. Summary and overall Conclusions on PBT or vPvB Properties

 

Both the ready and ultimate biodegradability in screening level tests consistently indicate that TMPD will not be persistent in the environment and that it is unlikely that the half-life of TMPD in fresh water will exceed 40 days. Based on these results TMPD would not be rated as either a P or vP substance.

Based on a measured maximum Log Pow value of 1.25, TMPD should not be rated as either a B or vB substance.

TMPD fails to meet the toxicity criterion (T) as specified in the REACH regulation (Annex XIII) based on acute aquatic toxicity values in excess of 100 mg/L. TMPD is not classified as a carcinogen, mutagen, or as a reproductive hazard; also, there is no evidence of chronic toxicity for TMPD as identified by classifications of T/R48 or Xn/R48.