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PBT assessment

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PBT assessment: overall result

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

Summary and overall conclusions on PBT or vPvB properties

 

The available data on degradation, bioaccumulation and toxicity for Oxooil LS9, indicate that the substance does not fulfil the PBT criteria (not PBT) nor the vPvB criteria (not vPvB).

 

PBT/vPvB criteria and justification

Persistence

Although the substance was not readily biodegradable in an OECD TG 310 study and hydrolysis is not considered to be a relevant pathway of degradation, the substance is not expected to be persistent. No further data on biodegradation (simulation test in surface water) were generated, since indirect oxidation by hydroxyl radicals in the atmosphere is considered to be the main environmental degradation pathway. This degradation pathway is environmentally relevant because of the high volatility of Oxooil LS9 from soil and water.

Based on the equilibrium partitioning coefficients between water, air and soil, the substance has the tendency to distribute to the air: the partitioning constant between water and air (Henry-constant) is very high: Henry constants range mainly from 7.56E+004 to 3.77E+005 Pa-m³/mole. Only one constituent present at a very low concentration (<1%) is less volatile (3.14 Pa-m³/mole); this constituent, however, is predicted to be readily biodegradable and not bioaccumulating (see attached information), and therefore of no concern with respect to PBT/vPvB properties. The persistence time of this constituent predicted by the Mackay Level III Fugacity model is 273 h, which is well below the 960 hours of the persistence criterion. 

 

The Henry-constant is calculated from the water solubilities being very low (<20 mg/L) and the vapour pressure of the substance being significant high (>1000 Pa). The partitioning coefficient between soil and water (Koc) on the other hand is not high enough to make soil or sediment a relevant target compartment.

 

Degradation in air

The half-lives for all relevant constituents in air (reaction with OH-radicals) were calculated (AOP v1.92): The half-life for hydroxyl radical reaction ranged from 1.14 h to 15.49 h. For olefins, additionally reaction with ozone is possible; half-lives ranged from 13.75 min to 22.92 h. Overall, these results indicate fast photodegradation of the constituents.

 

Half-life in the environment

For the relevance of atmospheric degradation for the entire environment (and the P-criterium), not only the rate of degradation in the atmosphere has to be considered. The velocity for transport from other compartments (compartments into which the release of Oxooil LS9 takes place) into the atmosphere is of the same importance.

EPI Suite (US EPA) provides two tools that consider the transport velocities between compartments as well as the corresponding half-lives / persistence times.

The Water Volatilization Program estimates volatilization half-lives from a model river and lake. It was used to model the situation for all relevant constituents of Oxooil LS9. Using default parameters of the model, the half-lives for the volatilization from river are: 1.1 hours and the half-lives for the volatilization from lake are 101.5 hours (4.2 days).

 

The half-life of the volatilization out of a lake of 4.2 days results, after 10 and 28 days, respectively, in a residual content of the substance of 19.2%, and 1% (elimination 80.8% and 99%, respectively). For comparison: a test for ready degradability is passed, if 60% degradation is achieved within 10 days (28 days for UVCB substances such as Oxooil LS9).

 

 Persistence times were estimated using the steady state model according to Mackay level III (Mackay, D. et al. 1996a, 1996b): this equilibrium criterion or EQC model describes the distribution of a chemical as steady state, non-equilibrium considering degradation, advection and intermedia transfer.

Using actual release rates, persistence times ranging from 80.9 to 273 hours (3.4 – 11.3 days) are calculated. This is significantly lower than the 960 hours of the persistence criterion (40 days). Therefore, Oxooil LS9 does not fulfil the “P” criterion.

 

In conclusion, Oxooil LS9 undergoes rapid degradation in the atmosphere by oxidation with OH-radicals; half-lives were calculated to be below the cut-off value for the “P” criterion.

 

Overall, degradation in air is environmentally relevant. The distribution to air and degradation in air are fast enough for non-P classification of Oxooil LS9.

 

Bioaccumulation

Based on the results in chapter 4.3 Bioaccumulation, Oxooil LS9 is not bioaccumulative (not B) and not very bioaccumulative (not vB).

Toxicity

Based on the results of the aquatic toxicity studies from chapter 7.1 and relevant mammalian toxicity studies in chaper 5, Oxooil LS9 is not Toxic (not T).

 

Emission Characterisation

Because the substance does not fulfil the PBT or vPvB criteria, no emission characterisation has been performed.

 

References

Mackay,D. et al. 1996a. Assessing the fate of new and existing chemicals: A fivestage process. Environ. Toxicol. Chem. 15:1618–1626.

 

Mackay,D. et al. 1996b. Evaluating the environmental fate of a variety of types of chemicals using the EQC model. Environ. Toxicol. Chem. 15:1627-1637