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Determination of a BCF follows Guidance on Information Requirements and Chemical Safety Assessment Chapter R.16: Environmental Exposure Estimation (ECHA 2008) and Chapter R. 7c Endpoint Specific Guidance (ECHA 2008).  Chapter R.16.5.3.5 states that there may be bioaccumulation potential if log Kow is >3. The Log Kow for 2-butyloctanol is a measured value of 5.5 (Spilker, 2009). According to REACH Annex IX, bioaccumulation information is required for substances manufactured or imported in quantities of 100 t/y or more.

 

Chapter R.7c states that BCFs can be determined experimentally, by calculation using Kow, or by estimating using BCF models such as QSARs.  BCFs and a BAF are calculated using regression-based approach and the Arnot-Gobas model using EPI Suite software.   

 

EPI Suite (regression-based estimate)

The BCFBAF version 3.01 programme of the EPI Suite software (EPIWEB 4.11) was used to predict a log BCF of 1.92 (BCF of 84) based on a regression estimate using a measured log Kow of 5.5.

 

EPI Suite (Arnot-Gobas upper trophic estimate)

The BCFBAF version 3.01 programme of the EPI Suite software (EPIWEB 4.11) was used to predict a log BCF of 2.79 (BCF of 609) based on the Arnot-Gobas upper trophic model both using a measured log Kow of 5.5.

 

By way of comparison, the OECD SIDS Initial Assessment Report for Long Chain Alcohols (2006) reports BCFs, calculated from Log Kow, from 7.0 for C6 to a maximum of 46,000 for C16, then reducing to 1,100 for C22 alcohols. It is generally considered for long chain alcohols that BCFs based on Log Kow calculations are overestimates:

 

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. The OECD SIDS report also concludes that alcohols are metabolised (biotransformed) in living organisms and that where biotransformation is not considered in an estimate, such as those based on log oil-water partition coefficients, then bioaccumulation potentials are overestimates. Measured BCF data on long chain alcohols supports the concept that bioaccumulation potential will be lower than estimated from Log Kow. For example, aqueous BCF calculations (as reported in the OECD SIDS Report (2006) and using BCFBAF v. 3.00) for hexadecan-1-ol ranged from 479 to 45300:

 

Measured

Log Kow

BCFBAF

Connell & Hawker

BCF (regression-based estimate)

BCF (Arnot-Gobas method)

BCF (as recalculated for the LCA SIAR)

Upper trophic

Mid trophic

Lower trophic

6.65

479

615

848

935

45300

These calculated values are much higher than an experimental BCF value of 60 for hexadecano-1-ol obtained by Freitag et al., (1982) 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 categorisation 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.”

 

The evidence seen in the literature (e.g. SIDS LCA Report, 2006) and in the estimated BCFs indicates that 2-butyloctanol is unlikely to bioaccumulate in the aquatic environment. In addition, LCAs have low solubility in water making for technically challenging test conditions but they are also unavailable for uptake and bioconcentration. This was confirmed by de Wolf and Parkerton (1999) who demonstrated that LCAs do not bioconcentrate because they are rapidly metabolised.

Terrestrial

According to REACH Annex IX, bioaccumulation information in aquatic species is required for substances manufactured or imported in quantities of 100 t/y or more. However, based on the weight of evidence confirming bioaccumulation is unlikely to occur in aquatic organisms, the endpoint for terrestrial organisms is waived.

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. Freitag D et al Geyer, H., Kraus, A., Viswanathan, R., Kotzias, D., Attar, A., Klein, W., and Korte, F. (1982); Ecotoxicological profile analysis VII. Screening chemicals their environmental behavior by comparative evaluation. Ecotox Environ Safety 6: 60-81, 1982