Creosote oil, acenaphthene fraction

Endpoint summary

Additional information

No experimental data is available for creosote oil, acenaphthene fraction (wash oil) itself. Thus, information from other substances will be used as substitute. Terrestrial toxicity data are available for the closely structure-related tar oil creosote as well as for major wash oil constituents (acenaphthene, fluorene, and 1-/2-methylnaphthalene). These substances will be used as supporting substances.

Creosote is closely related to wash oil with major constituent the same as in wash oil. Small differences exist for the concentration of methylnaphthalenes (somewhat lower) and of phenanthrene to fluoranthene (somewhat higher) due to a slightly different distillation range (200 to 355°C for creosote compared to 210 to 300°C for wash oil). Nevertheless, toxicity to the terrestrial compartment is considered to be similar for both substances as range of constituents correspond closely.

Supporting evidence will derive from acenaphthene, fluorene and 1-/2-methylnaphthalene data. These sub stances are substantial constituents of wash oil (see Chapter 7.1) contributing basically to the terrestrial toxicity of wash oil.

Terrestrial toxicity of wash oil related substances has been examined with annelids (substances fluorene and 1-/2-methylnaphthalene), arthropods (substances creosote, acenaphthene, and 1-/2-methylnaphthalene), plants (substance acenaphthene), and soil microorganisms (substance creosote and 1-/2-methylnaphthalene). Plants and arthropods appear to be the most sensitive species. Study results are presented in Chapters 7.2.1. to 7.2.3. The findings summarised below will be represented by data normalised to standard soil (2 % organic carbon content or 3.4 % of organic matter).

Toxicity to soil macroorganisms except arthropods

Data are available from studies with fluorene and 1-/2-methylnaphthalene (substance mixture) using OECD Test guidelines. Test organisms were the worms Enchytraeus crypticus and Eisenia fetida respectively. Test concentrations were measured (initial) for fluorene and nominal for the methylnaphthalene mixture.

Fluorene: EC10(21 d) = 31 mg/kg soil dw (reproduction) (Sverdrup et al., 2002)

1-/2-Methylnaphthalene: LC0(14 w) = 34 mg/kg soil dw (mortality) (Winkler, 1992a)

Toxicity to terrestrial arthropods

Data are available from studies with creosote, acenaphthene, and 1-/2-methylnaphthalene (substance mixture). For guidelines used see Chapter 7.2.2. Test organisms were the collembola (soil-dwelling springtail) Folsomia candida and Folsomia fimetaria. Test concentrations were measured (initial) for acenaphthene and nominal for creosote and the methylnaphthalene mixture. In the creosote test, mortality was the more sensitive endpoint with a NOEC lower than the NOEC for reproduction. The LC50 (mortality) was determined to be 15.9 mg/kg soil dw (normalised to 3.4 % of organic matter).

Creosote: LC10(28 d) = 3.4 mg/kg soil dw (mortality) (Bruhnke, 2007)

Acenaphthene: EC10(21 d) = 39 mg/kg soil dw (mortality) (Sverdrup et al., 2002)

1-/2-Methylnaphthalene: NOEC(28 d) = 19 mg/kg soil dw (reproduction) (Lang, 1992)

Toxicity to terrestrial plant

There is one study with a terrestrial plant available (germination and shoot growth of Lactuca sativa - lettuce; OECD TG 208). Test substance is acenaphthene. EC50 was determined to be 47 mg/kg soil dw. No dose response data or NOEC or EC10 are given in the publication. However, in an unpublished underlying report, the NOEC is stated to be 1.9 mg/kg soil dw recalculated to a soil with 2% organic carbon content (EU 2008). As the source of this report could not be verified (unpublished), the NOEC will not be used by itself but only as weight of evidence.

Acenaphthene: NOEC(14 d) = 1.9 mg/kg soil dw (shoot growth) (Hulzebos et al., 1993) (not verified, only weight of evidence)

Toxicity to soil microorganisms

Data are available from studies with creosote and 1-/2-methylnaphthalene (substance mixture). Endpoints investigated were carbon transformation and nitrate formation. In tests with creosote (carbon transformation) and 1-/2-methylnaphthalene (nitrate formation), no effects could be observed up to the highest concentration tested (1000 and 100 mg/kg soil dw, respectively). In a nitrate formation test with creosote, a NOEC could be determined.

Creosote: NOEC(14 d) = 316 mg/kg soil dw (nitrate formation rate) (Scheerbaum, 2007b)

Evaluation of combined data

There is no comprehensive dataset for one single substance. To decide on the lowest effect level valid for wash oil, all the data available will be considered together.

Toxicity to soil microorganisms is low (NOECs > 100 mg/kg soil dw up to > 1000 mg/kg soil dw) compared to effects on soil macroorganisms and plants. Therefore, this effect can be neglected for the decision which effect will be use to describe the terrestrial toxicity of wash oil.

The lowest NOECs/LC10 have been found for creosote (terrestrial arthropod) and acenaphthene (terrestrial plant). Both values are similar. The effect (NOEC) of acenaphthene on terrestrial plants could not be verified by a valid primary source. Thus, it will only be used as weight of evidence. For direct comparison, the L/EC50 values determined in both tests are available. The LC50 of 15.9 mg/kg soil dw from the collembolan reproduction inhibition test with creosote is distinctly lower than the reported EC50 of 47 mg/kg soil dw from the terrestrial plants seedling emergence and growth test with acenaphthene indicating a somewhat higher toxicity of creosote. This information will be considered as additional evidence. NOEC and LC10 from both tests are close together having principally the same magnitude. But the NOEC of 1.9 mg/kg soil dw from the terrestrial plant growth inhibition test will only be taken as supporting the creosote LC10 from the arthropod study especially as the extrapolation from the EC50 to the NOEC for this test cannot be verified. The LC10 from the collembolan reproduction inhibition test is assessed to be more valid.

Taking all available data into account, the LC10 of 3.4 mg/kg soil dw originating from the long-term toxicity test of creosote with terrestrial arthropods is assessed to be the most valid NOEC/LC10 and to characterise best the terrestrial toxicity of creosote oil, acenaphthene fraction (wash oil).

Reference:

EU 2008: European Union Risk Assessment- Report of COAL-TAR PITCH, HIGH TEMPERATURE (Final draft version May 2008) [http://echa.europa.eu/documents/10162/433ccfe1-f9a5-4420-9dae-bb316f898fe1]