Alcohols, C16-18, ethoxylated, phosphates

Bioaccumulation: aquatic / sediment

Description of key information

Alcohols, C16-18, ethoxylated, phosphates (CAS 106233-09-4) is regarded as not bioaccumulative. 

Additional information

No experimental data evaluating the bioaccumulation potential of Alcohols, C16-18, ethoxylated, phosphates (CAS 106233-09-4) is available. The substance exhibits a high log Kow (log Kow > 5) suggesting potential to bioaccumulate in biota. However, the information gathered on environmental behaviour and metabolism, provide enough evidence (in accordance to the REACh Regulation (EC) No 1907/2006, Annex XI General rules for adaptation of the standard testing regime set out in Annexes VII to X, 1.2), to cover the data requirements of Regulation (EC) No. 1907/2006, Annex IX) to state that this substance is likely to show little bioaccumulation potential.

Intrinsic properties and fate

Alcohols, C16-18, ethoxylated, phosphates (CAS 106233-09-4) is readily biodegradable. For readily biodegradable substances it is expected that they undergo rapid and ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs) (ECHA, 2012b). Therefore, after passing through conventional STPs, only low concentrations of these substances are likely to be (if at all) released into the environment.

Alcohols, C16-18, ethoxylated, phosphates (CAS 106233-09-4) exhibits a high log Kow and a water solubility < 0.53 mg/L. The Guidance on information requirements and chemical safety assessment, Chapter R.7b (ECHA, 2012b) states that once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Nevertheless, once this contact takes place, these substances are expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7a, ECHA, 2012a) and in the case of Alcohols, C16-18, ethoxylated, phosphates , the rest will be extensively biodegraded (due to ready biodegradability). Thus, discharged concentrations of these substances into the aqueous compartment are likely to be very low. Should the substances be released into the water phase, due to their hydrophobicity and expected high adsorption potential, they will tend to bind to sediment and other particulate organic matter, and therefore, the actual dissolved fraction available to fish via water will be reduced. Thus, the main route of exposure for aquatic organisms such as fish will be via food ingestion or contact with suspended solids.

QSAR data

Conflicting information on the bioaccumulation of Alcohols, C16-18, ethoxylated, phosphates (CAS 106233-09-4) in fish species is available from (Q)SAR estimations. Estimated bioconcentration (BCF) and bioaccumulation (BAF) values were calculated for representative components of this substance using the BCFBAF v3.01 program (Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10., US EPA). The calculated BCF and BAF values are 3 - 1650 L/kg (BCF, regression based estimate) and 1 - 447 and 4.4 - 2700 L/kg (Arnot-Gobas method, BCF and BAF, respectively). BCF calculations reflect the bioaccumulation potential after uptake via water, whereas the BAF gives an indication of the bioaccumulation when all exposure routes (water, food, etc.) are taken into account.

According to Regulation (EC) No. 1907/2006, Annex XIII, 1.1.2, a substance only fulfills the bioaccumulation criterion (B) when BCF values are > 2000 L/kg. Only for one component, i.e. Octadecyl dihydrogen phosphate, the trigger value of 2000 L/kg is exceeded by this (Q)SAR calculation. In this context, it should be noted, that for the comparable substance class of “long chain alcohols” calculated bioconcentration factors (BCF) have been critically assessed (OECD, 2006; Fisk et al. 2009). It was concluded, that the calculated values overestimate, the true potential for accumulation by over a magnitude. Based on the well-established knowledge on the rapid metabolism for long chain alcohols, it was judged that they will have a low potential for bioaccumulation. Therefore, the BCF/BAF values, calculated with Arnot-Gobas method are not used as key values for the assessment of bioaccumulation potential of this substance, but the assessment is rather based on the current knowledge on the metabolism.

Metabolism

Alcohols, C16-18, ethoxylated, phosphates are expected to be metabolized by the ubiquitary occurring enzyme class of phosphatases, resulting in fatty alcohols, polyalkoxylate glycols and phosphate. These constituents are expected to be further metabolised and/or be excreted rapidly. The polyalkoxylate glycols and phosphates are widely distributed within the water compartment of the body (summarised in EPA, 2009). The free alcohols can either be esterified to form wax esters (which are similar to triglycerides) or they can be transformed to fatty acids in a two-step enzymatic process catalyzed by alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). The responsible enzymes ADH and ALDH are present in a large number of animals including plants, and fish as well as in microorganisms. The polyalkoxylate glycols (and conjugated metabolites) and polyalkoxylate sulphates are excreted mainly via urine summarized in (HERA, 2003 and 2009). Therefore, no accumulation is expected.

Further evidence supports the assumption of low bioconcentration of this substance. For the structurally related substance class, Alcohol ethoxylates, reliable experimental data indicate a negligible bioaccumulation potential (Tolls, 1998; Tolls et al. 2000 as cited in HERA, 2009). Tolls (1998, and Tolls et al., 2000) showed that the parent AE (e.g. C13 EO8) was rapidly eliminated by transformation into metabolites, which were eliminated at a slower rate. The BCF factors which Tolls obtained using this combined technique for several AE homologues in fathead minnow range from <5 – 390 L/kg, clearly indicating low accumulation potential.

Testing difficulties

According to Annex XI, 2 of regulation Regulation (EC) No. 1907/2006 a study does not have to be conducted, if testing is technically not possible. Due to the very low water solubility and high log Kow no reliable test results can be retrieved for the analysis of the substance in the aqueous phase if an aqueous bioaccumulation test (OECD 305) would be conducted. According to “Guidance on information requirements and chemical safety assessment; Chapter R.7c” (ECHA, 2012c), a dietary accumulation test with fish may be used in cases where an aquatic bioaccumulation study is not suitable. However, considering the complexity of this UVCB substance, a reliable chemical analysis (e.g. radioactive labeling) is close of beeing impossible to create and a dietary study is thus omitted due to difficulties in the technical performance.

REACh requirements 10-100 t

The Guidance on information requirements and chemical safety assessment, Chapter R.11 (ECHA, 2012d) states: “if the tonnage produced or imported is below 100 t/y, normally a bioaccumulation test is not required and therefore a BCF value may not be available. In that case it should be considered if the available testing and non-testing data are sufficient to conclude on the B-properties for those substances < 100 t/y or if bioaccumulation testing is required to draw a reliable conclusion. If the weight of evidence approach is not sufficient to draw a conclusion, the performance of an experimental bioaccumulation test must be considered.

If bioaccumulation appears to be a critical parameter in the risk assessment process, it could still be necessary to perform a bioaccumulation test, although this may not be needed from the perspective of the PBT and vPvB assessment.

However, before such a test is conducted for assessing the B and vB criteria, the P criterion should be investigated first in order to prevent unnecessary testing of animals.”

Conclusion

Based on a) the data on structurally related substances as described above and b) the expected rapid metabolism and the intrinsic properties, such as ready biodegradability, it is therefore judged, that Alcohols, C16-18, ethoxylated, phosphates (CAS 106233-09-4) is unlikely to be bioaccumulative and further testing is thus omitted.

A detailed reference list is provided in within the CSR.