Lemon, ext.

Bioaccumulation: aquatic / sediment

Description of key information

The estimated BCF of the constituents in Lemon oil was in the range of 66 to 250 for monoterpenoids, typically 10 % of Lemon oil and 250 - 6683 for hydrocarbon terpenes, typically 87% of Lemon oil. With limonene as the main constituent the BCF is 361 for > 25% (typical 60%) of the NCS. The BCF is above 500 for only 3% (typical) of the NCS. 

Key value for chemical safety assessment

BCF (aquatic species):

361 L/kg ww

Additional information

NCSs, consisting of a number of constituents, do not have one single BCF value but a range of BCF values. BCF tests are not adapted to such complex UVCBs such as the NCSs, because of analytical monitoring issues (existing test protocols have been developed for single molecules which are preferably radio-labelled). A constituent approach is followed.

 

The range of BCF can be based on calculated or measured values of the individual constituents. Very few measured BCF values are available for the individual constituents. However, for all constituents, calculated BCF values can be derived by QSAR from log Kow.

 

In the constituent approach, estimated BCF values for the constituents have been used instead of measured. Thus the justification for use of constituent approach and estimated BCF values includes:

• no BCF data available for Lemon oil
• BCF difficult to determine for mixtures
• REACH Annex XI encourages the use of alternative information at all supply levels before a new vertebrate test is conducted
• the constituents as well as the test substance Lemon oil is considered readily biodegradable thus exposure of the aquatic compartment is expected to be low 

A drawback of every QSAR is that biotransformation is not included. The calculation method for BCF is generally realistic for the actual value, unless biotransformation occurs. When a substance is subject to biotransformation, the actual BCF will be lower than the calculated BCF. Thus, BCF calculations by QSAR are a worst case approach. 

 

The TGD provides the following information about the different QSAR models available for estimating BCF from log Kow: “Among the QSAR models based on the correlation between BCF and Kow, Meylan et al. (1999) compared their proposed fragment-based approach with a linear (Veith & Kosian, 1983) and bilinear (Bintein et al., 1993) model, using a data set of 610 non-ionic compounds. The fragment method provided a considerably better fit to the data set of recommended BCF values than the other two methods, as shown by the higher R2 value, but more importantly, a much lower SD and ME.” This supports the use of the more recently developed model based on Meylan et al (1999) instead of the older model according to Veith et al (1979). The regression method has been revised since 1999 and this QSAR is validated and incorporated in the EPIWIN program as the Log BCF regression-based estimate in the BCFBAF v3.00 programme. Attention is paid that each constituent falls within the applicability domain of the QSAR."

Log BCF values of known Lemon oil constituents were calculated using Log Kow estimates that were calculated using the corresponding log Kow value estimated by KOWWIN (see IUCLID chapter 4.7).

The estimated BCF of the constituents in Lemon oil was in the range of 66 - 258 for monoterpenoids, typically 10% of oil and 262 – 6680 for hydrocarbon terpenes, typically 87% of oil. With D-limonene as the main constituent the BCF is 361 for >25% (typical 60%) of the NCS. The estimated BCF is above 500 for only 3% of oil.

As the constituents are readily biodegradable, it is likely that they will also be biotransformed in higher organisms so a high bioaccumulation factor is actually not expected.