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Category name:
Citrus essential oils of the Rutacae family

Justifications and discussions

Category definition:
The category is built with substances of Unknown or Variable composition, Complex reaction products or Biological material (UVCB substances), or more specifically with NCSs (Natural Complex Substances). The substances in this particular category are essential oils, extracts, fractions and distillation products of the citrus species, which are all variants of the botanical Rutacae family.
Category rationale:
Category hypothesis

The rational for the grouping of these NCSs is based on:
a) The part of the plant as source for the NCS, namely in all cases the pericarp of the fruit
b) The common methods of production (peeling, pressing, rasping, extraction and refinement by filtration, distillation and other purification processes; see IUCLID chapter 3)
c) The same dominant constituent: D-limonene (in most oils >60%, in two oils > 25%)
d) Same and/or similar constituents: the common presence of myrcene (max 5%), β-pinene and γ-terpinene (both max 25%), citral (<35%), all being unsaturated C10H16 monoterpene hydrocarbons (see paragraph 1.2) and many other minor constituents (all < 10%, except in some qualities of lime oil where maximum values may be up to 22%) that are being shared within this group.

Based on these arguments, the citrus UVCB substances can be considered as a category. The constituents are predominantly alicyclic unsaturated monoterpene hydrocarbons with one or more double bonds. Other constituents are aliphatic short-chain aldehydes, alcohols or esters, some of these with one or more double bonds.

Citrus NCSs of the Rutacae family that do not comply with the above mentioned criteria a – d can not be included in this group for read across. The read across is primarily based on limonene (> 25%), and to a lesser extent also on β-pinene, γ-terpinene and citral (all max 35%). There are no other major constituents ≥ 10% (with the exception of some qualities of lime oil where maximum values may be up to 22%). Although this threshold for limonene and the other constituents can be considered arbitrary, it is clear that the lower the limonene content, the more difficult read across for some endpoints is. In this category, read across was feasible because 1) the citrus NCSs did not only share limonene as a major constituent in a percentage >25%, but 2) citrus NCSs with a lower content of limonene also share β-pinene and/or γ-terpinene and or citral in the same range (max 35%%) and 3) there were no other major constituents ≥ 10% (except for lime oil). The latter criterion is also important because it excludes the addition of constituents which are uncommon to this citrus category and may hamper read across. For Lime oil some constituents are > 10%, but they do not alter the C&L and therefore can also be considered not hampering read across

All category members are liquid at room temperature, liquid but slightly turbid or with some precipitate at -25°C, are similar in their boiling point, relative density and flash point (between 45 and 55°C). All category members are flammable. No other hazards linked to the physico-chemical properties have been established.

Based on the fact that the citrus NCSs share the same constituents and all contain one major constituent (D-limonene) and since physico-chemical properties are similar, there is no reason to expect any differences in toxicokinetic behaviour among the category members.