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Patchouli ext. is a multi-constituent substance consisting of sesquiterpene hydrocarbons and sesquiterpene alcohols. The acute lethal loading E(L)L 50 values for a mixture may be used directly for classification. However, they cannot be used to derive PNECs since partitioning in the environment will make the comparison with PEC meaningless. To assess environmental exposure and risks of Patchouli oil, three major constituents were chosen to represent blocks of related constituents: alpha-guaiene (represents lower boiling sesquiterpene hydrocarbons), alpha-bulnesene (represents higher boiling sesquiterpene hydrocarbons) and Patchouli alcohol (represents sesquiterpene alcohols).

Chromatographic profiles show that the majority of peak area in the aqueous samples from the water solubility, acute daphnia, acute fish and algal inhibition studies conducted on Patchouli Oil is from a single peak, which can be assigned to Patchouli alcohol. Given that any low levels of hydrocarbon components present are unlikely to exhibit acute aquatic toxicity at levels up to their limit of water solubility, the patchouli alcohol component is considered the lead substance responsible for the aquatic toxicity of Patchouli Oil. Toxicity data for Patchouli Oil based on loading rates shows that fish is the most sensitive species. Therefore, the 96-hour LC50 value of 1.0mg/L based on the alcohol component of the test item has been used to derive PNECaquatic for the sesquiterpene alcohol block. PNECaquatic for the hydrocarbon blocks has been derived from water solubility data.