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N-OCTADECYL MERCAPTAN (ODM)

N-Octadecyl mercaptan is one of these chemicals where no or little data is available

regarding their environmental impact. The chemical fate and pathways of ODM to the

environment has not been assessed before along with its PBT status. An assessment of the

PBT status of N-Octadecyl mercaptan (ODM) using the algorithm described in the toolbox is

explained below step by step.

Step 1: Substance identification

Identifiers on ODM have been obtained from the most recent reliable sources chemfinder and

chemspider which is listed in step 1. Unfortunately no IUCLID data is available for this

chemical. The smiles notation for N-OCTADECYL MERCAPTAN was obtained from the

chemspider source. These identifiers are shown in Table 1 below.

Identifier of N-Octadecyl mercaptan

EINECS or ELINCS number 220-744-1

CAS name and CAS number 2885-00-9

Name(s) in the IUPAC nomenclature orother international chemical name(s)

1-Octadecanethiol

Other names (usual name, trade name,abbreviation)

1-Mercaptooctadecane, n-Octadecylmercaptan, Stearyl mercaptan, n-Octadecanethiol

Information related to molecular andstructural formula of N-OctadecylmercaptanMolecular Formula C18H38S

Structural formula

Smiles Notation CCCCCCCCCCCCCCCCCCS

Table 1: N-Octadecyl mercaptan identification parameters.

SH

http://chembiofinderbeta.cambridgesoft.com/http://www.chemspider.com/http://www.reach-serv.com//index.php?option=com_content&task=view&id=58&Itemid=82MoonyTextBoxN-octadecyl mercaptan (ODM)

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Step 2: Data needed for the assessment

These are divided into the followings:

Physical-chemical properties (water solubility, Partition coefficient n-

octanol/water, Soil Adsorption Coefficient (KOC/Kd), and Henry's Law Constant)

Degradation, (biodegradation, half lives)

Accumulation (BCF)

Environmental Partitioning (MacKay)

Ecotoxicity data of the substance (LC50, NOEC)

Step 3: Collecting the available information and identifying the data gap

1- Information on the physical-chemical properties for N-Octadecyl mercaptan

The following table provides a summary of the

1. Chemical and physical properties required for the assessment as explained in the

algorithm.

2. The available chemical and physical properties of N-Octadecyl mercaptan along with

the source for these data. As explained in the algorithm, in this step you have to make

sure that the data studies were conducted according to EU-approved methods (e.g.

those specified in Annexes V and VIII of Directive 67/548/EEC, or REACH Annex X

methods) and in compliance with the principles of GLP.

3. The data gap which is highlighted as red in the table

Required Property Value SourceWater solubility Insoluble but no measured value is

available.MSDS and NIOSH PocketGuide to Chemical Hazards

Partition coefficient n-octanol/water

Log Kow = 9.12 (estimated notmeasured)

ChemID plus and chemspider

Soil AdsorptionCoefficient (Koc/Kd)

No measured log Koc value isavailable for N-Octadecylmercaptan.

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Henry's Law Constant No experimentally determinedHenry’s law constant information isavailable.

Table2: Physical chemical data available for N-Octadecyl mercaptan.

2- Accumulation data of N-Octadecyl mercaptan

According to MITI result (Biodegradation and Bioaccumulation Database on Existing

Chemicals, Japan (MITI), see step 3 for link), bioaccumulation of N-Octadecyl mercaptan

was studied with common carp (Cyprinus carpio). The mean BCF measured from this study

was approximately

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5- Aquatic toxicity information of N-Octadecyl mercaptan

Not measured data is available.

Required Property Value Source

FishAcute toxicity to fish(96hrs LC50) mg/l

No data available IUCLID

Long term toxicity to fish(28days NOEC) mg/l

No data available IUCLID

DaphniaAcute toxicity to Daphnia(48hrs EC50) mg/l

No data available IUCLID

Long term toxicity to Daphnia(21days NOEC) mg/l

No data available IUCLID

AlgaeAcute toxicity to algae(72hrs EC50) mg/l

No data available IUCLID

Table4: Aquatic toxicity data available for N-Octadecyl mercaptan

Step 4: Filling the data gap by using QSAR

In this step the above endpoints (both the available and not) will be predicted using QSAR

tools and software listed in step 4 of the algorithm (EPIWIN, Danish(Q)SAR data base and

PBT profiler). The reason for doing this is to compare the QSAR results with the

experimental one to identify the accurate of the QSAR. However, as seen above no

experimental data is available for ODM and hence no comparison could be carried out.

1- Results obtained by using EPIWIN

Table 5 provides the predicted values for the above endpoints using EPIWIN software along

with the name of the programme used. The output obtained by EPIWIN for each end point is

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given. Also included is explanation, which in the toolbox would be obtained by clicking on a

link to view.

Required Property EPI QSARProgramme

Predicted Value

Water solubility WSKOW

(result output)

2.36*10-4 mg/l at 25 0C

Partition coefficient n-octanol/water

KOWWIN log KOW = 9.12 ( not very accurate since it is outside theregion of log Kow 0-5).

Bioconcentration Factor (BCF) BCFWIN LogBCF2 (Syracuse) = 0.5

Soil Adsorption Coefficient(Koc/Kd)

(PCKOCWIN) KOC= 4.26*105

Henry's Law Constant HENRYWIN 3.23*10-1 atm-m3/mole

Half lives-t1/2

1-Hydrolysis as a function of pH HYDROWIN can not be estimated.

2-Photolysis (Atmospheric OHRate Constant)

AOPWIN Atmospheric OxidationRate Constant = 63.972 *10-12 cm3/molecule-secHalf-Life = 2.006 hrs

( Atmosph. Oxidation, Ozone) AOPWIN No Ozone Reaction Estimation

Biodegradability

BIOWIN1 BIOWIN 0.7196 (Biodegrades fast)

BIOWIN2 BIOWIN 0.6864 (biodegrades fast)

BIOWIN3 (Ultimatebiodegradation)

BIOWIN 2.8642 (weeks)

BIOWIN4 (PrimaryBiodegradation)

BIOWIN 3.7034 (Days)

BIOWIN5 BIOWIN 0.7001 (Readily Degradable)

BIOWIN6 BIOWIN 0.8283(Readily Degradable)

BIOWIN7 BIOWIN 0.8806 ( biodegrade fast)

Ready Biodegradability Prediction BIOWIN Yes

Environmental Partitioning

(MacKay) EPI V3.2

(Results output)

Level III Fugacity Model:

Mass Amount Half-Life

(percent) (hr)

Air 0.147 4.01

http://www.reach-serv.com/uploads/ODMEPIWIN output results.pdfMoonyTextBoxResults output

http://www.reach-serv.com/uploads/ODMEPIWIN3.2 output results.pdf

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Water 3.75 360

Soil 28 720

Sediment 68.1 3.24e+003Aquatic toxicity:

FishAcute toxicity to fish

(96hrs LC50) mol/lLong term toxicity

(28days NOEC) mol/l

ECOSAR LC50 (96hrs) = 0.002 mg/l (not reliable because Chemicalmay not be soluble enough to measure this predicted

effect)

DaphniaAcute toxicity to Daphnia

(48hrs EC50) mol/lLong term toxicity

(21days NOEC) mol/l

ECOSAR

AlgaeAcute toxicity to Daphnia

(72hrs EC50) mol/l

ECOSAR

Table5: EPIWIN predictions of the required endpoints

2- Results obtained from Danish(Q)SAR database

The Danish (Q)SAR report for N-Octadecyl mercaptan is shown below (Figures 1 and 2)

with some comments. This output contains predictions for physical-chemical, environmental

and human health endpoints, however, as we are only interested in selected physical-chemical

endpoints along with the environmental endpoints these are highlighted in yellow or blue in

the report. The yellow highlighter identifies the values that have been predicted in the Danish

(Q)SAR using the EPIWIN suite and therefore we can check whether the results obtained

directly with the EPIWIN suite agree (Table 5). The blue highlighter indicates to the values

predicted using other QSAR models such as multicase which is used to predict the

biodegradability.

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Figure1: Danish(Q)SAR report for N-Octadecyl mercaptan

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Figure2: Danish(Q)SAR report for N-Octadecyl mercaptan

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Before proceeding to step 5, it is useful to compare the predicted values obtained from

EPIWIN with the Danish(Q)SAR database (see Table 6). In this way the reproducibility of

EPIWIN predictions can be tested as explained previously.

As expected, we could see that t the predictions from the EPIWIN suite are consistent with

the one obtained from the Danish(Q)SAR ( Log Kow, Log Koc and Henry's Law Constant, see

Table 6). However, the predicted parameters from using QSARs other than EPIWIN which

are listed in Danish(Q)SAR report are different form EPIWIN. An example for this can be

seen in the biodegradability result. This is an important aspect for the assessment as these

numerical values are crucial for determining if the PBT criteria are met.

Required Property Predicted Value usingDanish(Q)SAR database

Predicted Value using EPIWIN

Water solubility 0.002mg/l 2.36*10-4 mg/l at 25 0C

Partition coefficient n-octanol/water

log Kow =9.12 log KOW = 9.12 ( not very accurate since it isoutside the region of log Kow 0-5).

Bioconcentration Factor (BCF) LogBCF2 (Syracuse) = 0.5, BCF =3.16Log BCF(Bintien) = 1.68, BCF =47.86

LogBCF2 (Syracuse) = 0.5

Soil Adsorption Coefficient(Koc/Kd)

log Koc = 5.629 log Koc = 5.629, KOC= 4.26*105

Henry's Law Constant 0.232 atm-m3/mole 0.323 atm-m3/mole

Half lives-t1/2

1-Hydrolysis as a function of Ph N/A

2-Photolysis (Atmospheric OHRate Constant)

0.167 days which is equal to2.006hrs

Atmospheric OxidationRate Constant = 63.972 *10-12

cm3/molecule-sec

Half-Life = 0.167 Days (12-hr day; 1.5E6OH/cm3)Half-Life = 2.006 hrs

( Atmosph. Oxidation, Ozone) N/A Can not be estimated

Biodegradability

BIOWIN1 0.7196 0.7196 (Biodegrades fast)

BIOWIN2 0.6864 0.6864 (biodegrades fast)

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BIOWIN3 (Ultimatebiodegradation)

2.8642 2.8642 (weeks)

BIOWIN4 (PrimaryBiodegradation)

3.7034 3.7034 (Days)

BIOWIN5 0.7001 0.7001 (Readily Degradable)

BIOWIN6 0.8283 0.8283(Readily Degradable)

BIOWIN (Ready BiodegradabilityPrediction)

Yes

Multicase (Ready BiodegradabilityPrediction) NEGEnvironmental Partitioning

(MacKay, (III)) Air(%) 0.293

Water (%) 7.28

Soil(%) 27.9

Sediment(%) 64.5

Air (%) 0.147

Water (%) 3.75

Soil (%) 28

Sediment (%) 68.1FishAcute toxicity to fish (96hrs LC50)mol/lLong term toxicity

(28days NOEC) mol/l

LC50 (96hrs) for Bintein:

= 140.4mg/l (non-polar)

=296.33mg/l (Polar)

LC50 (96hrs) for Syracuse:

= 738.6mg/l (non-polar)

=172.19mg/l (Polar)

LC50 (96hrs) = 0.002 mg/l (not reliablebecause Chemical may not be soluble

enough to measure this predicted effect)

DaphniaAcute toxicity to Daphnia (48hrsEC50) mol/lLong term toxicity

(21days NOEC) mol/l

Value can not be considered since itis outside the model domain

AlgaeAcute toxicity to Daphnia (72hrsEC50) mol/l

Value can not be considered since itis outside the model domain

Table6: Comparison between the results obtained from EPIWIN, Danish(Q)SAR and theexperimental one.

Step 5: Assess your substance to identify whether it is PBT or vPvB

Is your substance persistent? (Degradation properties)

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The assessment of persistence is based on the degradation data. As seen above, no measured

data is available on the rate of degradation of N-Octadecyl mercaptan in the environment.

Where no measured environmental degradation data are available, the predicted one can be

used as a screen to indicate persistence.

The predicted rate constant and estimated half-life for the reaction of hydroxyl radicals with

N-Octadecyl mercaptan in the atmosphere indicated that when N-Octadecyl mercaptan is

released to the atmosphere is likely to be rapidly degraded (not persistence) by this fate

process. Moreover no data was available with regards to aquatic degradation. As a result a

definitive conclusion cannot be reached regarding persistence of N-Octadecyl mercaptan in

the Environment. Further testing would be needed to determine the rate of aquatic

degradation.

In this case the ready biodegradability result can be used to determine if a substance meets

the P criteria. The DEPA Multicase (Q)SAR (see Table 6 ) gives a prediction that the

substance is not readily biodegradable. This is in contrast with BIOWIN v4.02 which gives

an overall prediction that the substance is readily biodegradable. In this condition when two

different predictions for the same endpoint exist, the one, which indicates the higher risk, will

be used. Moreover, the PBT Profiler has estimated that ODM is expected to be found

predominantly in sediment and its persistence estimate is based on its transformation in this

medium. Its half-life in sediment, 140 days, exceeds the EPA criteria of >= 2 months but not

the EU criteria of 180 days. Therefore, ODM is estimated to be persistent in the environment.

As a conclusion, based on the ready biodegradability prediction results (multicase) and PBT

profiler, N-Octadecyl mercaptan is considered to meet the screening criteria for persistence.

Is your substance bioaccumlative?

The assessment of bioaccumlative is based on the measured BCF. According to MITI result,

bioaccumulation of N-Octadecyl mercaptan was studied with common carp (Cyprinus

carpio). The mean BCF measured from this study was approximately

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profiler and multicase. Both BCFWIN v2.17 and PBT profiler predict BCF of 3.16 for N-

Octadecyl mercaptan based on logKOW of –1.08. Multicase prediction for BCF is slightly

higher but still does not exceed the EU bioconcentration criteria and therefore, N-Octadecyl

mercaptan is considered not to meet the screening criteria for bioaccumulation.

Is your substance toxic to the environment organisms?

No data is available for toxicity of ODM to fish, Daphnia and algae. In the absence of reliable

toxicity data, the predicted one can be used as a screen to indicate toxicity to aquatic

organisms. Unfortunately, results from a (Q)SAR investigation of the acute and chronic

toxicity to fish and Daphnia cannot be considered since ODM is appeared clearly outside the

applicability domain of the ECOSAR models (log KOW>6). Therefore, the criteria for toxicity

cannot be determined and further testing will be required to confirm if the criteria for toxicity

are met.

Is your chemical classified as potential PBT?

On the basis of the available data, the screening criteria for PBT/vPvB cannot be determined

due to the lack of the information regarding its toxicity. ODM is considered to be persistent

but not bioaccumulative based on the screening criteria. This is in agreement with PBT

profiler estimate for N-Octadecyl mercaptan. The PBT Profiler has estimated that N-

Octadecyl mercaptan is persistent not bioaccumulative while its toxicity could not be

estimated. Further testing will be required to confirm if the criteria for persistence,

bioaccumulation and toxicity are met.

What is the preferred environmental compartment of your chemical? (Environmental

Distribution )

The PBT Profiler has estimated that N-Octadecyl mercaptan is expected to be found

predominantly in sediment and its persistence estimate is based on its transformation in this

medium. This is in agreement with Mackay level III predictions which shows that that

sediment is the preferred environmental compartment (68%). Its half-life in sediment, 140

days, exceeds the EPA criteria but not EU. Therefore, N-Octadecyl mercaptan is estimated to

be persistent in the environment under the EPA criteria.

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