Registration Dossier
Registration Dossier
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EC number: 292-605-3 | CAS number: 90640-84-9 A complex combination of hydrocarbons produced by the distillation of coal tar and boiling in the range of approximately 240°C to 280°C (464°F to 536°F). Composed primarily of acenaphthene, naphthalene and alkyl naphthalene.
Biodegradation in soil
Administrative data
Link to relevant study record(s)
Description of key information
Half-life of PAH in soil has been determined in a study similar to OECD TG 309. Half-lives increased with increasing size of PAH. The half-lives in soil determined in this study for the highest molecular size PAH present in wash oil (phenanthrene and anthracene) are selected to represent the half-life of wash oil itself. As conservative estimate, the 90th percentile calculated from the measured values has been used as half-life of wash oil in soil.
Key value for chemical safety assessment
- Half-life in soil:
- 109 d
- at the temperature of:
- 20 °C
Additional information
Creosote oil, acenaphthene fraction (wash oil) is a liquid UVCB substance mainly consisting of 2- and 3-ring polycyclic aromatic compounds. Major constituents are (typical concentration): naphthalene (ca 11 - 13 %), 2-methylnaphthalene (ca. 17 - 20 %), 1-methylnaphthalene (ca. 7 - 9 %), and acenaphthene (ca. 13 - 15 %). 3-ring PAH comprised of fully aromatic 6-membered rings are only minor components with typical contents of ca. 2 % (phenanthrene) and 0.3 % (anthracene).
Due to the complex composition of wash oil, a distinct half-life for the substance as whole cannot be experimentally determined. Main components (all PAH) will have their individual half-lives.
Experimental results for individual PAH substances (Park et al. 1990) show that half-life of PAH increases with growing molecular size and ring-number. Three-membered fully aromatic rings will be the constituents of wash oil with the longest half-lives. Using the half-lives of these constituents for the wash oil as whole will result in very conservative half-life for wash oil (worst case estimate).
The highest molecular size constituents of wash oil are phenanthrene and anthracene (for percentage see above). If the half-lives of these substances are used to represent the half-life of the substance wash oil, the resulting value will be conservative.
Experimental results (Park et al., 1990, see above) demonstrate longer half-lives for anthracene (two different soils: 50 and 134 days) compared to phenanthrene (two different soils: 16 and 35 days). As anthracene only contributes 0.3% to the total of wash oil, it does not seem to be justified to establish a half-life for wash oil in soil only based on the highest value (134 days) determined for this minute constituent. As conservative estimate, the 90th percentile resulting from the four measured values is considered to represent satisfactorily the half-life of wash oil as a whole in soil. A value of 109 days is calculated using the QUANTIL.INKL function in MS Excel 2013.
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