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Environmental fate & pathways

Bioaccumulation: terrestrial

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Key value for chemical safety assessment

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The BCF (terrestrial) is calculated using the ECHA Equation R.16-76, which is BCFearthworm = (0.84+0.012Kow)/RHO earthworm. The RHOearthworm by default value of 1 (kg wwt/L) can be assumed.

BCF calculation using logKow of 6.80 (Kow is 6309573.445)

BCFearthworm = 0.84+(0.012*6309573.445)/1

BCFearthworm = 75715.72

The BCF of 75,716 (rounded) for earthworms indicates that 2-hexyldecanol has a high tendency to accumulate in terrestrial organisms.

While the predicted BCF for earthworms indicate a tendency for accumulation of 2-hexyldecanol in terrestrial organisms, it is unlikely 2-hexyldecanol will accumulate to this extent. Alcohols are ubiquitous in nature and are produced by all living organisms (Mudge et al., 2008). As a result, alcohol and aldehyde dehydrogenase enzymes used in the conversions of alcohols to fatty acids are also ubiquitous in the plant and animal kingdoms (de Wolf and Parkerton, 1999). The ability of organisms to metabolise alcohols will limit the potential for bioaccumulation. This ability of organisms to readily metabolise long chain alcohols will also result in the over-estimation of bioaccumulation by QSAR models. According to Belanger et al. (2009), calculated BCFs for long chain alcohols are 1 to greater than 2 log units higher than measured values.

For example, aqueous BCF calculations (as reported in the OECD SIDS Initial Assessment Report for Long Chain Alcohols (2006) and using BCFBAF v. 3.00) for hexadecan-1-ol ranged from 479 to 45300:

 Measured Log Kow  BCF (regression-based estimate) BCF (Arnot-Gobas method) Upper trophic 

 BCF (Arnot-Gobas method) Mid trophic

 
  BCF (Arnot-Gobas method) Lower trophic BCF (as recalculated for the LCA SIAR) (Connel & Hawker 
 6.65  479  615  848 935  45300 

These calculated values are much higher than an experimental BCF value of 60 for hexadecan-1-ol obtained by Freitag et al., (1985) using the Golden Orfe (Leuciscus idus melanotus). Although there are a number of short-comings (e.g. length of exposure, only total radioactivity was measured) with this study, the result is considered to be useful supporting evidence for the over-estimation in modelled BCFs.

The bioaccumulation potential of long chain alcohols has also been reviewed by Environment Canada during their preliminary decisions on the ecological categorization of substances on the Canadian Domestic Substance List. Upon review of the available data, Environment Canada (undated) concluded that "[...] aliphatic alcohols do not meet the categorization criteria for bioaccumulation. Although the substances are lipophilic in nature, it is evident that the metabolism rates prevent any significant accumulation."

Based on the weight of evidence, it is reasonable to assume that the predicted BCF of 75,716 for earthworms is an over estimate by orders of magnitude.

References:

Belanger, S.E., Sanderson, H., Fisk, P.R., Schäfers, C., Mudge, S.M., Willing, A., Kasai, Y., Nielsen, A.M., Dyer, S.D., and Toy, R. (2009). Assessment of the environmental risk of long-chain aliphatic alcohols. Ecotoxicology and Environmental Safety, Volume 72, Issue 4, May 2009, Pages 1006-1015.

de Wolf, W. and Parkerton, T. (1999). Higher alcohols bioconcentration: influence of bio-transformation. In: Symposium `Persistent, Bioaccumulative, Toxic Chemicals' at the 217th ACS National Meeting, Anaheim (CA, USA), March 21-25, 1999.

Environment Canada (undated). Response to the ICG Aliphatic Working Group's Proposal Regarding Environment Canada's Preliminary Categorization of Aliphatic Alcohols.

Frietag, D., Ballhorn, L., Geyer, H., and Korte, F. (1985). Environmental hazard profile of organic chemicals. An experimental method for the assessment of the behaviour of organic chemicals in the ecosphere by means of simple laboratory tests with 14C labelled chamicals. Chemosphere 14, 1589 - 1616.

Mudge, S.M., Belanger, S.E., and Nielsen, A.M. (2008). FattyAlcohols-Anthropogenic and Natural Occurrence in the Environment. Royal Society of Chemistry, London, UK.

OECD SIDS Initial Assessment Report for SIAM 22 (2006). Long Chain Alcohols; Tome 1: SIAR. Organisation for Economic Cooperation and Development.