Hydrocarbons, C14-30, olefin-rich

Ecotoxicological Summary

Conclusion on classification

The acute ecotoxicity tests report that the EL and LL50 are above the WAF tested. This indicates that acute effects are not observed even at loading concentrations far in excess of the water solubility of the test substance. Poorly water soluble substances which do not exert acute toxicity at their limit of solubility may require a precautionary classification of R53 'May cause long term advserse effects in the aquatic environment' under the DSD and Chronic Category 4 under the CLP Regulations.

This classification can be removed if the substance is readily biodegradable or does not demonstrate chronic toxicity at the limit of solubility. Alkenes with a carbon number range of C10 -24 have been shown to be readily biodegradable. Therefore, the components of hydrocarbons C14-30 olefin rich in the C10-24 range would not require a classification of R53, chronic 4.

The following justification is submitted in support of the removal of R53, Chronic Cat 4 for the C24 and higher olefins, based on demonstrating that the substance shows no chronic toxicity at the limit of solubility. Experimental chronic toxicity is not available at this carbon number range. However,

1. All the acute ecotoxicity data for category members demonstrates that there is an acute toxicity cut-off at approximately C12 – C14. Based on an acute to chronic ratio of <10 for non-polar narcotics, and acute/chronic toxicity QSARs, the change in carbon length at which chronic toxicity would also not be exhibited would be at least 2 carbon units higher (equivalent to a log Kow change of approx 1). Suggesting C16 as the lower limit at which chronic toxicity would be observed. This observation is also supported by the following two QSAR predictions;

2. In running PETROTOX/HC5 (Redman et al., 2010) – a prediction of no acute or chronic toxicity at the limit of solubility for these carbon chain-lengths, >C24 is obtained,

3. ECOSAR (Nabholz and Mayo-Bean, 1998) predictions indicate that no acute of chronic toxicity is expected at the limit of solubility for alkenes of C24 and above.

4. Historically CONCAWE (CONCAWE, 2001) in assessing Waxes (C20 – C50 (iso)alkanes and cyclic alkanes), Foots Oil (C20 – C50 isoalkanes), Slack Waxes ( C12 – C50, (iso)alkanes) and Petrolatums (C20 – 85 (iso)alkanes and cyclic alkanes) have used the same read-across argument :

QSAR assessment of the toxicity of the substances in this group, based on their hydrocarbon composition, indicates that they would not be expected to cause acute toxicity to aquatic organisms. Substances in this group do not meet the criteria for ready degradability. However, based on read across of chronic toxicity results from related high molecular weight hydrocarbons (i.e., lubricants and hydrocarbon solvents), the substances in this group would not be expected to pose a long-term hazard to the environment.

5. Finally – the most recent data available from the CONCAWE assessment of petroleum hydrocarbons (CONCAWE, 2010)reviews the chronic ecotoxicity of the lower carbon chain lengths (<C20). A solubility cut-off of 1 – 10 µg/l is discussed as the limit of chronic aquatic toxicity. This clearly demonstrates that the C24 and above olefins with calculated solubilities of <1 ng/L would be extremely unlikely to be able to exert toxicity in the aquatic environment.  

Based on this justification, hydrocarbons C14-10 olefin rich is not given the precautionary classification of R53, Chronic Cat 4.