Naphtha (Fischer-Tropsch), light, C4-10-branched and linear

Endpoint summary

Additional information

The UVCB substance 'Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear' had an experimentally determined log KOW of 4.4 to > 6.5 (whereas 60.2% of the test material had a log KOW-value greater than 6.50) and would therefore be expected to have the potential to bioaccumulate. However, the bioaccumulation potential may not be realised in vivo because of the high degradability potential of the component hydrocarbons. In this context a recent review can be taken into account, which demonstrates / underpins this thesis (Rojo, 2009; see IUCLID section 5.6 for more details).

Moreover, a systematic review of the persistence and bioaccumulation properties of petroleum hydrocarbons is available (whereas measured data and model predictions were used to develop an evidence-based conclusion), which supports the conclusion that none of the branched and linear constituents that comprise 'Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear' meet the PB criteria. Accordingly, none of the constituents that comprise 'Naphtha (Fischer-Tropsch), light, C4-10 - branched and linear' has a bioconcentration factor in aquatic species higher than 2000.

Some further information is available regarding bioaccumulation, from a solid phase micro extraction (SPME) study (see EPSR Harris, 2013). SPME is a biomimetic extraction system that tries to mimic the way organisms extract chemicals from water. A biomimetic extraction technique using SPME in conjunction with gas chromatography (GC) was employed to assess the level of water soluble hydrocarbons and hence the potential toxicity of water accommodated fractions (WAFs) for a range of GTL products. In addition, the toxicity of WAFs was also monitored using an in-vitro MicrotoxTMassay, a biosensor-based measurement system based on Vibro Fischeri bacteria. In this study the majority of GTL samples (including the registration substance GTL Naphtha) analysed using SPME-GC indicated a low total peak area for soluble hydrocarbons (on average less than 12 000) and hence toxicity, with no detectable toxicity using the MicrotoxTM assay. The low total peak area for soluble hydrocarbons for these substances is indicative of a low potential to bioaccumulate. The related C8 -16 ("GTL Kerosine") and C4 -10 ("GTL Naphtha") samples, consisting of shorter chain hydrocarbons, produced a more soluble hydrocarbon fraction, and GTL Naphtha resulted in a moderate level of toxicity detected with the MicrotoxTM assay. The level of toxicity seen with the GTL Naphtha is, however, considerably less than that seen with the crude oil gasoline.

Aquatic bioconcentration factors (BCF) for consituents of GTL Naphtha were calculated using a validated QSAR method. Further details are given in the attached QM(P)RF documents.