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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Bioaccumulation tests are waived based on the fact that the available information is deemed sufficient for classification purposes, the PBT assessment and the chemical safety assessment. Since a significant fraction of Patchouli ext. has partition coefficients greater than 5.7, the substance is considered to be potentially bioaccumulative for classification and PBT assessment purposes. Predicted worst-case BCF values for the three major constituents were used for the CSA.

Key value for chemical safety assessment

Additional information

According to REACH Annex IX, information on bioaccumulation in aquatic species, preferably fish, is required for substances manufactured or imported in quantities of 100 t/y or more unless the substance has a low potential for bioaccumulation (for instance a log Kow ≤ 3). However, REACH aims to reduce animal testing where possible and according to the Integrated Testing Strategy (ITS, Figure R.7.10-2) in ECHA Guidance R.7c (Endpoint specific guidance), all available information should be assessed before further testing for bioaccumulation is performed. Furthermore, complex mixtures pose a special challenge to bioaccumulation assessment, because of the range of individual substances that may be present, and the variation in their physico-chemical and environmental fate properties. In such cases, it may be possible to screen for bioaccumulation potential by deriving a range of Kow values from a HPLC method. It is preferable to identify one or more constituents for further consideration that can be considered representative of other constituents in the mixture in terms of bioaccumulation potential.

Patchouli Oil is a multi-constituent substance consisting of sesquiterpene hydrocarbons and sesquiterpene alcohols. The HPLC method (OECD 117) was used to determine the partition coefficient. The HPLC chromatogram of the test material showed a large number of peaks, ten of which had relative peak areas of more than 1%. The first group of peaks (peaks 1 to 3) were determined to have log Kow values of 3.2, 4.5 and 5.0. Another group of peaks (peak 4 to 10) were found to have partition coefficients above the highest limit of the calibration range (i.e. > 5.7). Since a significant fraction of Patchouli Oil has partition coefficients > 5.7, the substance is considered to have the potential to bioconcentrate for classification purposes ( CLP Regulation EC 1272/2008 cut-off value of ≥ 4) and to meet the screening bioaccumulation criterion (logKow > 4.5) for PBT/vPvB assessment purposes.

For the chemical safety assessment, 3 key constituents have been identified that represent blocks of related constituents in Patchouli Oil in order to assess environmental exposure and risk.The BCF for each constituent was estimated using log Kow based QSARs.

alpha-guaiene: represents sesquiterpene hydrocarbons with lower boiling point, estimated BCF = 19700

alpha-bulnesene: represents sesquiterpene hydrocarbons with higher boiling point, estimated BCF = 15670

Patchouli alcohol: represents sesquiterpene alcohols, estimated BCF = 482

The BCF for Patchouli alcohol was calculated in EUSES v2.1.2 based on an estimated log Kow of 3.98 (Kowwin v1.68).  For substances with a log Kow higher than 6, EUSES uses a parabolic equation which, according to the EC TGD Part II (2003), has a higher degree of uncertainty than the linear regression used for substances with a log Kow of 2-6. Moreover, the parabolic equation is based on a relatively small data set of 43 persistent chemicals, mainly chlorinated hydrocarbons (EC TGD Part III, Chapter 4). In contrast, Patchouli Oil and its underlying constituents are considered readily biodegradable and are not are chlorinated. Therefore for alpha-guaiene and alpha-bulnesene, which have estimated log Kow values of 6.4 and 6.7 respectively, it was considered more appropriate to apply a consensus modelling approach using the BCF models available in BCFBAF v3.01. The results are summarised in the table below. The highest predicted BCF value for each constituent was chosen as a conservative estimate for risk assessment purposes.

Constituent

Predicted BCF (BCFBAF v3.01)

regression based estimate

Arnot-Gobas (upper trophic)a

Arnot-Gobas (mid trophic)a

Arnot-Gobas (lower trophic)a

Arnot-Gobas (upper trophic)b

alpha-guaiene

7706

11590

16160

17580

19700

alpha-bulnesene

13000

9654

14110

15670

15600

a) Including biotransformation rate estimates; b) Assuming a biotransformation rate of zero

The BCFBAF regression-based QSAR for non-ionic substances with a log Kow of 1.0 to 7.0 is based on a large dataset of 396 while the Arnot-Gobas BCF & BAF method is considered to have wide applicability to non-ionic organic substances with a log Kow of < 9 and was calibrated to large database of high quality BCF and BAF observations (482 and 936 respectively). Moreover, the Arnot-Gobas BCF QSAR (assuming a biotransformation rate of zero) was developed to fit upper bound BCF observations and as such can be considered to give conservative and worst-case estimates. The two sesquiterpene hydrocarbons fall within the applicability domain of both models. They are non-ionic and have an estimated log Kow which is within the log Kow applicability domain of both models. 

Using the worst-case predicted BCF values for the above three representative constituents, the chemical safety assessment does not show a need for further refinement. Therefore, the available information is deemed sufficient for classification purposes, the PBT assessment and the chemical safety assessment and no further testing is required.