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Environmental fate & pathways

Adsorption / desorption

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adsorption / desorption: screening
Type of information:
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
EPISuite (v4.11)

2. MODEL (incl. version number)
KOCWIN v2.00

CAS: 32582-32-4

A reliable QSAR model was used to calculate the adsorption/desorption potential of 2-Tetradecyl-1-octadecanol. Koc values were calculated using the KOCWIN v2.00 module embedded within the EPISuite v4.11) computer model.
EPISuite and its modules (including KOCWIN) have been utilized by the scientific community for prediction of phys/chem properties and environmental fate and effect properties since the 1990’s. The program underwent a comprehensive review by a panel of the US EPA’s independent Science Advisory Board (SAB) in 2007. The SAB summarized that the EPA used sound science to develop and refine EPISuite. The SAB also stated that the property estimation routines (PERs) satisfy the Organization for Economic Cooperation and Development (OECD) principles established for quantitative structure-activity relationship ((Q)SAR) validation.
The EPISuite modules (including KOCWIN) have been incorporated into the OECD Toolbox. Inclusion in the OECD toolbox requires specific documentation, validation and acceptability criteria and subjects EPISuite to international use, review, providing a means for receiving additional and on-going input for improvements.
In summary, the EPISuite modules (including KOCWIN) have had their scientific validity established repeatedly.
- Defined endpoint and unambiguous algorithm:
KOCWIN estimates Koc with two separate estimation methodologies: (1) estimation using first-order Molecular Connectivity Index (MCI) and (2) estimation using log Kow (octanol-water partition coefficient).
The initial KOCWIN (version 1) model estimated Koc solely with a QSAR utilizing Molecular Connectivity Index (MCI). This QSAR estimation methodology is described completely in a journal article (Meylan et al, 1992) and in a report prepared for the US EPA (SRC, 1991). KOCWIN (version 2) utilizes the same methodology, but the QSAR has been re-regressed using a larger database of experimental Koc values that includes many new chemicals and structure types. Two separate regressions were performed. The first regression related log Koc of non-polar compounds to the first-order MCI.
A traditional method of estimating soil adsorption Koc involves correlations developed with log octanol-water partition coefficient (log Kow) (Doucette, 2000). Since an expanded experimental Koc database was available from the new MCI regression, it was decided to develop a log Kow estimation methodology that was potentially more accurate than existing log Kow QSARs for diverse structure datasets. Effectively, the new log Kow methodology simply replaces the MCI descriptor with log Kow and derives similar equations. The derivation uses the same training and validation data sets. The training set is divided into the same non-polar (no correction factors) and correction factor sets. The same correction factors are also used.
- Defined domain of applicability:
According to the KOCWIN documentation, there is currently no universally accepted definition of model domain. However, the documentation does provide information for reliability of the calculations. Estimates will possibly be less accurate for compounds that 1) have a MW outside the range of the training set compounds and 2) have a functional group(s) or other structural features not represented in the training set, and for which no fragment coefficient was developed; and that a compound has none of the fragments in the model’s fragment library.
- Appropriate measures of goodness-of-fit and robustness and predictivity:
KOCWIN calculated the Koc values based on the following equations:
Estimation Using MCI: log Koc = 0.5213 MCI + 0.60
Estimation Using Log Kow: log Koc = 0.8679 Log Kow - 0.0004
The KOCWIN model had the following statistics:
MCI Methodology (Training Set): number = 69 correlation coef (r2) = 0.967
MCI Methodology (Validation Set): number = 158 correlation coef (r2) = 0.850
log Kow Methodology (Training Set): number = 68 correlation coef (r2) = 0.877
log Kow Methodology (Validation Set): number = 150 correlation coef (r2) = 0.778
These correlation coefficients indicate the KOCWIN model calculates results that are equivalent to those generated experimentally and are, hence, adequate for the purpose of classification and labelling and/or risk assessment.
Overall, the MCI methodology is somewhat considered more accurate than the Log Kow methodology, although both methods yield good results. If the Training datasets are combined in to one dataset of 516 compounds (69 having no corrections plus 447 with corrections), the MCI methodology has an r2, standard deviation and average deviation of 0.916, 0.330 and 0.263, respectively, versus 0.86, 0.429 and 0.321 for the Log Kow methodology.

As described above, according to the KOCWIN documentation, there is currently no universally accepted definition of model domain. In general, the intended application domain for all models embedded in EPISuite is organic chemicals. Specific compound classes, besides organic chemicals, require additional correction factors. Indicators for the general applicability of the KOCWIN model are the molecular weight of the target substance and the identification of functional group(s) or other structural features and their representation in the training set. The training set molecular weights are within the range of 32.04 – 665.02 with an average molecular weight of 224.4 (Validation set molecular weights: 73.14 – 504.12 and average of 277.8). The molecular weight of 2-Tetradecyloctadecan-1-ol is 466.88, which falls within the range of both, the training set and the validation set.
In addition, the functional group of 2-Tetradecyloctadecan-1-ol (Aliphatic Alcohol (-C-OH)) is represented in the training set and hence addressed by fragment correction.

--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
First Order Molecular Connectivity Index ........... : 16.346
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 9.1210
Fragment Correction(s): 1 Aliphatic Alcohol (-C-OH) ........... : -1.3179
Corrected Log Koc .................................. : 7.8031
Estimated Koc: 6.355e+007 L/kg

Koc Estimate from Log Kow:
Log Kow (Kowwin estimate) ......................... : 14.52
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 8.9565
Fragment Correction(s):
1 Aliphatic Alcohol (-C-OH) ........... : -0.4114
Corrected Log Koc .................................. : 8.5451
Estimated Koc: 3.508e+008 L/kg

As a result 2-Tetradecyloctadecan-1-ol would not be considered outside the estimation domain.

The Koc values were calculated as 6.355e+007 L/kg and 3.508e+008 L/kg L/kg based on Molecular Connectivity Index (MCI) and log Kow method, respectively. These results both indicate that 2-Tetradecyloctadecan-1-ol is immobile in soil. Considering the available experimental results for the category, these findings support the conclusion that the adsorption potential increases with increasing carbon chain length.
Hence, the KOCWIN predicted adsorption/desorption potential is considered valid and adequate for the purpose of risk assessment.

Documentation of the KOCWIN model is provided in the following references:
Doucette, W.J. 2000. Soil and sediment sorption coefficients. In: Handbook of Property Estimation Methods, Environmental and Health Sciences. R.S. Boethling & D. Mackay (Eds.), Boca Raton, FL: Lewis Publishers (ISBN 1 -56670 -456 -1).
Meylan, W., P.H. Howard and R.S. Boethling. 1992. Molecular topology/fragment contribution method for predicting soil sorption coefficients. Environ. Sci. Technol. 26: 1560 -1567.
McFarland, M. et al. 2007. “Science Advisory Board (SAB) Review of the Estimation Programs Interface Suite (EPI SuiteTM)”. SRC. 1991. Group Contribution Method for Predicting Soil Sorption Coefficients. William Meylan & Philip H. Howard, Syracuse Research Corporation (June 3, 1991). EPA Contract No. 68-D8-0117 (Work Assignment 2-19); SRC F0118-219
other: REACH Guidance on QSARs R.6
Principles of method if other than guideline:
Meylan, W., P.H. Howard and R.S. Boethling, "Molecular Topology/Fragment Contribution Method for Predicting Soil Sorption Coefficients", Environ. Sci. Technol. 26: 1560-7 (1992).
Specific details on test material used for the study:
Key result
63 550 000 L/kg
Remarks on result:
other: estimate from MCI
Key result
350 800 000 L/kg
Remarks on result:
other: estimate from log Kow

KOCWIN v2.00 predicted that 2-tetradecyloctadecan-1-ol has a Koc > 1e+007 L/kg (6.355e+007  L/kg MCI method; 3.508e+008 L/kg logKow based method).

Executive summary:


Description of key information

From QSAR calculation and the two studies provided for this endpoint it is expected that 2-tetradecyloctadecan-1-ol will be immobile in soils and sediment. However, according to a ready biodegradation study of Flach (2014) 2-tetradecyloctadecan-1-ol is readily biodegradable.
In conclusion, 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 in section 5.2, 2-tetradecyloctatetradecan-1-ol is readily biodegradable and unlikely to persist in the environment.

Key value for chemical safety assessment

Koc at 20 °C:
63 550 000

Additional information

KOCWIN v2.00 predicted that 2-tetradecyloctadecan-1-ol has a Koc > 1e+007 L/kg (6.355e+007  L/kg MCI method; 3.508e+008 L/kg logKow based method).