2-butyloctan-1-ol

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

2-Butyloctanol is a member of the Guerbet Alcohols, which comprises a range of branched long chain alcohols C12-36. It is also structurally related to the substances of the OECD SIDS Long Chain Alcohols (LCA) categories, comprising a range of straight and branched long chain alcohols C6-22 and the REACH LCA categories, comprising a range of straight and branched long chain alcohols C6-24. As defined in the ‘Read Across Justification Document’ section 13, data provided for these categories is representative of 2-butyloctanol and suitable for assessment purposes. Experimental data for the Guerbet and LCA categories has been evaluated and trends in physico-chemical properties, environmental fate, ecotoxicology and toxicology of long chain alcohols was used to read-across to the C12 alcohol, 2-butyloctanol for biodegradation, adsorption and (eco)toxicity endpoints.

2-Butyloctanol does not fulfil the screening criteria for persistence, bioaccumulation and toxicity and the overall conclusion is that 2-butyloctanol does not meet the PBT or vPvB criteria. No further testing is required.

Persistence Assessment (P)

According to Annex XIII of Regulation (EC) No 1907/2006 and to the Guidance on information requirements and chemical safety assessment Chapter R.11 (PBT Assessment, ECHA (2008)), a substance does fulfil the criteria “persistent (P)”, if:

- the half-life in marine water is higher than 60 days, or

- the half-life in fresh- or estuarine water is higher than 40 days, or

- the half-life in marine sediment is higher than 180 days, or

- the half-life in fresh- or estuarine water sediment is higher than 120 days, or

- the half-life in soil is higher than 120 days.

Results of the biodegradation simulation tests with a range of Guerbet and other long chain alcohols considered to be representative of 2-butyloctanol demonstrate that the test substance is readily degraded under aerobic conditions in fresh waters. The C12 LCA, dodecanol, attained a high rate of degradation (88% degradation) over a 28-day test duration and >60% degradation during the 14 day window (Werner, 1993). Experimental studies by Richterich (1998 and 1991) on 2-hexyldecanol confirm ready biodegradability for this C16 LCA (>79% and 96% levels over 28 days, respectively). Richterich (1998) and Hertl (1999) reported ready biodegradability of 2-octyldodecanol and a mixture of 2-octyldodecanol and 2-hexyl-1-tetradecanol (64% and 63% degradation in 28 days respectively). The result of an oxygen consumption test by Richterich (1998) on 2-octyldodecanol was considered to be a false negative (>2% level). In a study by Flach (2012), the degradation of 2-decyltetradecanol (C24 LCA) was 84.9 % after 28 days. The degradation rate reached more than 60% within the 10-day window and the test substance is considered to be readily biodegradable. Two further studies by Richterich (1997) with mixtures of C32-36 alcohols, branched indicated moderate biodegradability (47% and 14% levels). However, biodegradation is considered to be limited for the longest carbon chain lengths (C32-36 alcohols) by the low water solubility and poor availability of the test substance for degradation.

Evidence from published literature included a ready biodegradation study by Casteel & Menzies (2009) in which 10 linear primary alcohols from butanol (C4) to docosanol (C22) were tested and concluded that all 10 LCAs are readily biodegradable and satisfy the 10-day criterion. Other studies by Richterich (1998a and b), Belanger et al (2009) and Federle and Ittrich (2006) all reported rapid biodegradation in LCAs from C16 to C22 linear and Guerbet alcohols.

It is concluded that given the very close similarity between C6-C22 LCAs (both linear and Guerbet) as well as similar physico-chemical properties and structure, it is fully expected that the C12 LCA, 2-butyloctanol, will also be readily biodegradable. The published literature is supported by several experimental studies by Werner (1993), Richterich (1998a and b, 1991), Flach (2012) and by Hertl (1999).

According to ECHA Guidance on information requirements and chemical safety assessment (May 2008), Chapter R.11, Figure 11-1: Integrated testing strategy for persistency assessment - maximising data use and targeting, 2-butyloctanol is neither persistent nor very persistent.

Bioaccumulation Assessment (B)

According to Annex XIII of Regulation (EC) No 1907/2006 and to the Guidance on information requirements and chemical safety assessment Chapter R.11 (PBT Assessment, ECHA (2008)), a substance does not fulfil the criteria “bioaccumulative (B)” or “very bioaccumulative (vB)” if the bioconcentration factor (BCF) is below 2000 or 5000 respectively or if the log Kow is below 4.5.

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), in which it states that BCFs can be determined experimentally, by calculation using Kow, or by estimating using BCF models such as QSARs.  The BCFBAF version 3.00 programme of the EPI Suite software (EPIWEB 4.0) was used to predict a log BCF of 84 (BCF of 1.92) based on a regression estimate using a measured LogKow of 5.5. 

The calculated log Kow for 2-butyloctanol is therefore greater than 4.5; however, based on the calculated bioconcentration factor (BCF) of 84, 2-butyloctanol cannot be regarded as bioaccumulative in aquatic organisms.

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 and LCA category REACH dossier also conclude 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. 

The bioaccumulation potential of long chain alcohols has also been reviewed by Environment Canada during its 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.

The data requirement for bioaccumulation studies in terrestrial organisms is waived because, whilst the LCA may adsorb readily to sediment, sludge and soil, it will rapidly degrade. In addition, where a substance does sorb to sediment or soil, the substance will be readily degraded as it desorbs. Based on the evidence for rapid degradability, indirect exposure of 2-butyloctanol to soil organisms is unlikely due to the ready biodegradability of the substance within the STP process. Direct exposure is also unlikely as 2-butyloctanol is not supposed to be applied to soils.

In conclusion, 2-butyloctanol cannot be regarded as bioaccumulative in aquatic, sediment or terrestrial organisms; 2-butyloctanol does not fulfil the criteria “bioaccumulative (B)” or “very bioaccumulative (vB)”. According to ECHA Guidance on information requirements and chemical safety assessment (May 2008), Chapter R.11, Figure 11-2: Integrated testing strategy for B-assessment, no further testing is required to conclude on the bioaccumulation criterion.

Toxicity Assessment

Although a toxicity assessment is not required if the P and B criteria are not met (see above) it is discussed here. According to Annex XIII of Regulation (EC) No 1907/2006 and according to the Guidance on information requirements and chemical safety assessment Chapter 11 (PBT Assessment, May 2008), a substance does not fulfill the criterion if the NOEC for marine or freshwater organisms is 0.01 mg/l or higher and if there is no evidence of chronic toxicity considering human health and no classification as carcinogenic (category 1 or 2), mutagenic (category 1or 2) or toxic for reproduction (category 1, 2 or 3) according to Directive 67/548/ECC.

Read across is used to address short-term ecotoxicity and human toxicity endpoints as defined in the ‘Read Across Justification Document’ section 13 in which data provided for the Guerbet and long chain alcohols categories is representative of2-butyloctanoland suitable for assessment purposes.

2-butyloctan-1-ol is not classified as carcinogenic (category 1A or 1B), germ cell mutagenic (category 1A or 1B), or toxic for reproduction (category 1A, 1B or 2). There is no evidence of chronic toxicity, as identified by the classifications: STOT (repeated exposure), category 1 (oral, dermal, inhalation of gases/ vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/ vapours, inhalation of dust/mist/fume) according to the CLP Regulation.

Reliable long-term ecotoxicity data are available for 2-butyloctanol, for algae only. Vryenhoef and Mullee (2012) provide a study using the green algae,Pseudokirchnerella subcapitata, where the 72-hour NOEC, based on growth rate, was 0.38 mg/L. Additionally, reliable long-term data are available for a structural analogue of2-butyloctanol, dodecanol. Schaeffers (2005) conducted a long-term study exposingDaphnia magnato concentrations of dodecanol for 21 days. The 21-day NOEC was 0.014 mg/L based on reproduction. Reliable toxicity short-term toxicity data indicate that invertebrates are the most sensitive to 2-butyloctanol with a 48-hour EC50 of 0.14 mg/L. Therefore, it is possible to qualitatively conclude that, based on available acute effects test data for2-butyloctanoland long-term toxicity data for a structural analogue (dodecanol), 2-butyloctanol does not pose a risk to the freshwater aquatic compartment.

There are no toxicity data for sediment-dwelling or terrestrial organisms relating to2-butyloctanolor other long chain alcohols. However, these endpoints are waived on the basis of the following arguments (i) technical testing difficulties due to low water solubility, (ii) ready biodegradability within the STP process and the surface water environment, (iii) the physico-chemical data indicate that the substance is not bioaccumulative and (iv) based on read-across from other long chain alcohols,2-butyloctanolis unlikely to be toxic to aquatic organisms.

Based on available reliable data for toxicity of 2-butyloctanol andcategory constituents of LCAs, short-term acute toxicity (LC₅₀or EC₅₀) to aquatic organisms is >0.01 mg/L and does not meet the definitive toxicity criterion according to the ECHA guidance on PBT assessment (Part C). Chronic data on aquatic species indicates 2-butyloctanol long-term toxicity (NOEC) to aquatic organisms is >0.01 mg/L and therefore the criteria of Annex XIII REACH for aquatic toxicity are not fulfilled.Additionally,it is concluded that long-term effects are unlikely due to the ready biodegradability of 2-butyloctanol. It can be concluded that the substance does not fulfill the Toxicity criteria as laid down in Annex XIII of regulation (EC) No 1907/2006.

PBT Assessment

Persistence: From a comparison of the results obtained for Guerbet Alcohols and other long chain alcohols with the criteria of REACH Annex XIII, it can be concluded that 2-butyloctanol is not persistent (P) under aerobic conditions.

Bioaccumulation: In conclusion, 2-butyloctanol cannot be regarded as bioaccumulative in aquatic, sediment or terrestrial organisms; 2-butyloctanol does not fulfil the criteria “bioaccumulative (B)” or “very bioaccumulative (vB)”. According to ECHA Guidance on information requirements and chemical safety assessment (May 2008), Chapter R.11, Figure 11-2: Integrated testing strategy for B-assessment, no further testing is required to conclude on the bioaccumulation criterion.

Toxicity: Based on available reliable data for toxicity ofconstituent category substance of LCAs, including 2-butyloctanol, short-term acute toxicity (LC₅₀or EC₅₀) to aquatic organisms is >0.01 mg/L and does not meet the definitive ecotoxicity criterion according to the ECHA guidance on PBT assessment (Part C). Chronic data on aquatic species are not available for 2-butyloctanol but are available for the structural analogue, but it is concluded that long-term effects are unlikely due to the ready biodegradability of2-butyloctanoland therefore the criteria of Annex XIII REACH foraquatic toxicity are not fulfilled.

2-butyloctanol is not classified as carcinogenic (category 1A or 1B), germ cell mutagenic (category 1A or 1B), or toxic for reproduction (category 1A, 1B or 2). There is no evidence of chronic toxicity, as identified by the classifications: STOT (repeated exposure), category 1 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) according to the CLP Regulation.

It can be concluded that the substance does not fulfill the Toxicity criteria as laid down in Annex XIII of regulation (EC) No 1907/2006.

2-Butyloctanol does not fulfil the screening criteria for persistence, bioaccumulation, and toxicity. The overall conclusion is that 2-butyloctanoldoes not meet the PBT or vPvB criteria. No further testing is required.