Hydrocarbons, C16-C22, n-alkanes, isoalkanes, <2% aromatics

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Fischer-Tropsch substances are multi-constituent, and consist predominantly of linear and branched alkanes. Within an individual substance the alkanes cover a range of carbon chain lengths and various levels of branching. A key issue for the risk assessment of such substances is the possibility that even though a substance has passed a ready biodegradability test, it might contain some persistent (‘P’) or very persistent (‘vP’) constituents. These would be expected to be those that are most highly branched. Furthermore, some of these constituents could be bioaccumulative (‘B’) or very bioaccumulative (‘vB’), or toxic (‘T’). Therefore the possibility that some ‘vPvB’ or ‘PBT’ constituents are present in the substances needs to be investigated.

Criteria for assessing PBT characteristics are defined in REACH Annex XIII.

The persistence of constituents of Hydrocarbons, C16-C22, n-alkanes, isoalkanes, <2% aromatics was assessed using an adapted version of the BIOHCWIN model, which is described in detail in Section 4.1.2 of the Chemical Safety Report.

Predicted degradation half-lives in surface water are shown in Table 4.1.2 of the Chemical Safety Report.

From this table it can be seen that there are some candidate substances that meet the screening criteria for ‘P’ in the range C20 to C25, and some which meet the screening criteria for ‘vP’ in the range C23 to C26. Constituents below C20 are not persistent according to Annex XIII criteria.

The bioaccumulation potential of constituents of Hydrocarbons, C16-22, n-alkanes, isoalkanes, <2% aromatics is described in detail in Section 4.3.1 of the Chemical Safety Report. All of the constituents at ≥C16 meet the screening criteria for B, but none of the constituents are vB.

Prediction of chronic ecotoxicity values for constituents of Hydrocarbons, C16-C22, n-alkanes, isoalkanes, <2% aromatics is discussed in detail in Section 7.7 of the Chemical Safety Report. None of the constituents meets the criteria for “T”.

Conclusions

P         Contains some candidate P constituents in the range C20 to C22

B        Contains candidate B constituents at ≥C18; no vB constituents (Section 4.3 of the CSR).

T         Contains no T constituents (Section 7.7 of the CSR).

Based on the predictive methods, there are some constituents that meet some individual criteria for P, vP, or B. However, no constituents present in Hydrocarbons, C16-C22, n-alkanes, isoalkanes, <2% aromatics meet all criteria for PBT or vPvB.

Therefore, neither vPvB nor PBT applies to constituents present at above 0.1% in Hydrocarbons, C16-C22, n-alkanes, isoalkanes, <2% aromatics, on the basis of validated predictive QSAR methods.