Pitch, coal tar, high-temp.

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption / desorption of single PAH

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Studies based on accepted scientific methods, peer-reviewed data

Principles of method if other than guideline:

Determination of (log) Koc of single polycyclic aromatic hydrocarbons (PAH) by (Q)SAR calculations: no Koc of pitch, coal tar, high-temp. derivable due to absence of water solubility.

GLP compliance:

no

Type of method:

other: (Q)SAR calculation

Media:

soil

Specific details on test material used for the study:

The following polycyclic aromatioc hydrocarbons are taken into account in the determination of the range of (log) Koc values that are representative for the UVCB substance CTPht.
- phenanthrene,
- anthracene,
- fluoranthene
- pyrene,
- chrysene
- benz[a]anthracene
- benzo[a]pyrene

Test temperature:

not applicable

Details on study design: HPLC method:

not applicable

Details on sampling:

not applicable

Details on matrix:

not applicable

Details on test conditions:

not applicable

Computational methods:

not applicable

Key result

Type:

Koc

Value:

832 000 dimensionless

Remarks on result:

other: substance benzo[a]pyrene; value obtained from log Kow by calculation

Key result

Type:

log Koc

Value:

5.92 dimensionless

Remarks on result:

other: substance benzo[a]pyrene; value obtained from log Kow by calculation

Type:

Koc

Value:

ca. 12 600 - ca. 800 000 dimensionless

Remarks on result:

other: values obtained from log Kow by calculation; range for different PAH

Type:

log Koc

Value:

ca. 4.1 - ca. 5.9 dimensionless

Remarks on result:

other: values obtained from log Kow by calculation; range for different PAH

Details on results (HPLC method):

not applicable

Adsorption and desorption constants:

not applicable

Recovery of test material:

not applicable

Concentration of test substance at end of adsorption equilibration period:

not applicable

Concentration of test substance at end of desorption equilibration period:

not applicable

Transformation products:

not measured

Details on results (Batch equilibrium method):

not applicable

Statistics:

--

Log Koc values were derived from log Pow (Kow) values by using (Q)SAR calculations applying two different methods (see below). Data and calculation methods are taken from two different sources (EU 2008 and KEMI 2010). In addition, experimental log Kow values are reported (from References 1) and 2)).

Overview of estimated log Koc values, derived from log Pow (Kow) values

	CAS-No.	LogKow (exp.)	LogPow (EU 2008^3))	LogKoc^c^) (EU 2008^3))	LogPow (KEMI 2010^4))	LogKoc^d^) (KEMI 2010^4))
Phenanthrene	85-01-8	4.57^1)	4.57^a)	4.36	4.50	4.05
Anthracene	120-12-7	4.68^1)	4.68^a)	4.47	4.50	4.05
Fluoranthene	206-44-0	5.23^1)	5.20^a)	4.99	5.06	4.60
Pyrene	129-00-0	5.18^2)	4.98^b)	4.77	5.02	4.56
Chrysene	218-01-9	5.81^1)	5.81^a)	5.60	5.76	5.30
Benz[a]anthracene	56-55-3	5.91^1)	5.91^a)	5.70	5.63	5.18
Benzo[a]pyrene	50-32-8	6.13^1)	6.13^a)	5.92	6.27	5.82

a) slow-stirring method

b) shake flask method

c) compare to EU RAR 2008³⁾: Koc values were estimated using the experimental equation derived by Karickhoff et al. (1979)⁵⁾: Koc = 0.63 Kow

(or log Koc = 1.00 log Kow – 0.21)

d) compare to KEMI 2010⁴⁾: Koc values were estimated using the equation derived by Seth et al. 1999)⁶⁾: Koc = 0.35 Kow;

The error limits on Koc, resulting from differences in the nature of organic matter and the experimental difficulties and constraints in Koc measurements, are a factor of 2.5 in both directions, i.e. the coefficient 0.35 may vary from 0.14 to 0.88.

 

References:

1)     de Maagd P G-J, ten Hulscher D ThEM, van den Heuvel H, Opperhuizen A, and Sijm D THM (1998): Physicochemical Properties of Polycyclic Aromatic Hydrocarbons: Aqueous Solubilities, n-Octanol/Water Partition Coefficients, and Henry's Law Constants. Environ.Toxicol. Chem. 17, 251-257

2)     Miller MM, Wasik P, Huang G-L, Shiu W-Y, and Mackay D (1985): Relationships between octanol-water partition coefficient and aqueous solubility. Environ. Sci. Technol. 19, 522-529

3)     EU (2008): Coal-Tar Pitch, high temperature - European Union Risk Assessment Report, The Netherlands (URL:https://echa.europa.eu/documents/10162/433ccfe1-f9a5-4420-9dae-bb316f898fe1)

4)     EMI (2010): Creosote (PT8) - Document II-A - Risk Assessment (Final)

5)     Karickhoff SW, Brown DS, and Scott TA (1979): Sorption of hydrophobic pollutants on natural sediments. Water Res. 13, 241-248
Karickhoff SW (1981): Semi-empirical estimation of sorption of hydrophobic pollutants on natural sediments and soil. Chemosphere 10, 883-846

6)     Seth R, Mackay D, and Muncke J (1999): Estimating the organic carbon partition coefficient and its variability for hydrophobic chemicals. Environ. Sci. Technol. 33, 2390-239

 

Reference 2

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption / desorption of single PAH

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Pitch, coal tar, high-temp. (coal-tar pitch, CTPht), is a UVCB substance of variable composition. It consists of a complex mixture of polycyclic aromatic hydrocarbons (PAH), predominantly of highly condensed aromatic ring systems forming an inert matrix. In this matrix, individual PAH with a lower degree of condensation are included (mostly four- and five-membered ring aromatic PAH). Physico-chemical properties and biological effects of coal-tar pitch are characterised on the one hand by the inert matrix, on the other hand by the individual PAH that may be set free from the inert matrix.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Determination of (log) Koc values was performed for individual PAH included in the list of the 16 EPA PAH. Selected values are taken as characteristic for the environmental fate of the substance pitch, coal tar, high-temp. as such.

3. ANALOGUE APPROACH JUSTIFICATION
As consequence of the production process (residue of the oxygen free high-temperature distillation of tar, coal, high-temperature, CAS No. 65996-89-6), coal-tar pitch consists mainly of a highly polycondensed, to some extent carbonised inert matrix including some less condensed materials (polycyclic aromatic hydrocarbons). This is demonstrated by the fact that only a fraction of ca. 20 % of the substance will evaporate at a distillation temperature up to 500 °C. This fraction comprises polycyclic
aromatic hydrocarbons with predominantly 4- and 5-membered (up to 6) rings. CTPht is scarcely soluble in water (ca. 0.24 mg dissolved C/L at a loading of 1000 mg substance/L) and only limited soluble in organic solvents like quinoline or toluene. Most of the substance is not accessible by common analytical tools. Only about 10 % can be identified by GC. Fraction of the 16 EPA PAH in GC analysis is up to 7.5 % with up to 1.5 % of them being benzo[a]pyrene (BaP).
Under environmental conditions or during processing of the substance, environmentally available or volatile components of CTPht may be released. This will be PAH (mainly four and five ring representatives) incorporated into the inert matrix. The most relevant PAH among them under an environmental or toxic point of view is benzo[a]pyrene. This substance is besides benzo[b]fluoranthene the most abundant PAH, determined under the components of CTPht analysable by GC.
For these reasons, BaP is selected as marker substance for the substance CTPht itself. Data determined for BaP will be taken to characterise CTPht as a whole and will be used in the chemical safety assessment of CTPht.

Reason / purpose for cross-reference:

read-across source

Principles of method if other than guideline:

Read-across to the preceding entry:
Source substance: polycyclic aromatic hydrocarbons (PAH), generic mixture;
Reference: EU, Rapporteur: The Netherlands, Bureau REACH, Bilthoven 2008; KEMI - Kemikalieinspektionen, Swedish Chemicals Agency 2010

Key result

Type:

Koc

Value:

832 000 dimensionless

Remarks on result:

other: this value is determined for the substance benzo[a]pyrenem, which serves as marker substance for CTPht; it is used for the CSA of CTPht as such

Key result

Type:

log Koc

Remarks:

determined by (Q)SAR calculation

Value:

5.92 dimensionless

Remarks on result:

other: this value is determined for the substance benzo[a]pyrenem, which serves as marker substance for CTPht; it is used for the CSA of CTPht as such

Description of key information

No Koc value is derivable for the substance pitch, coal tar, high-temp. as such due to practical insolubility in water and complexity of its composition. Benzo[a]pyrene serves as marker substance. Koc and log Koc are estimated based on the log Kow of BaP (see below).

Key value for chemical safety assessment

Koc at 20 °C:

832 000

Additional information

The key values used for the environmental exposure assessment relate to the marker substance benzo[a]pyrene (BaP). The Koc has been estimated from the mean log Pow of 6.13 for BaP (see Chapter 1.3 and EU 2008 - Risk assessment report of coal-tar pitch, high temperature). The Koc value is estimated using the experimental equation derived by Karickhoff et al. (1979): Koc = 0.63 Kow (or log Koc = 1.00 log Kow - 0.21).

[LogKoc: 5.92]