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Aquatic toxicity of anthracene oil (with < 50 ppm BaP, anthracene oil low, AOL, composite sample CS 07) itself was only tested in a short-term aquatic toxicity test with aquatic invertebrates (daphnia) and in a toxicity test with algae. Other short-term tests have been performed using other closely structure-related tar oils: anthracene oil with > 50 ppm BaP (anthracene oil high, AOH, composite sample CS 06), creosote oil, acenaphthene fraction (wash oil, composite sample CS 05), and creosote. All these oils are UVCB substances of complex composition with a low water solubility. They comprise merely PAH, and the nature of constituents and the individual components coincide closely. Percentage of single substances present in the oils is of the same magnitude. They are used complementary to define the short-term aquatic toxicity of AOL.

Long-term aquatic toxicity tests with anthracene oil (AOL) could not be identified. Tests with phenanthrene are used instead to characterise the long-term aquatic toxicity of AOL. AOL contains mainly three-ring aromatic compounds and to a lesser extent PAHs with four rings (see Chapter 1.). Two-ring aromatics are minor. In combination, these substances will constitute the toxic effects of AOL to aquatic organisms.

Main component of AOL is phenanthrene. It is present in AOL in concentrations up to 31 % (average 28 %). Amongst the PAH present in AOL, phenanthrene is one with the most pronounced aquatic toxicity. Individual four-ring PAH may have a somewhat higher aquatic toxicity than phenanthrene, but this is counterbalanced by the much higher concentration of phenanthrene. Therefore, the toxicity potential of phenanthrene in the aquatic environment is considered to be representative of total AOL integrating the toxic effects of all its other PAH constituents. Thus, phenanthrene can be used as surrogate and marker substance to characterise the aquatic toxicity of total AOL.

Short-term toxicity (tests with AOL and other tar oils)

Due to the complex composition and variable but low solubility of its components, water solubility of AOL is not clearly defined. Depending on the quantity used, concentration of material dissolved in saturated water samples is variable. Therefore, water accommodated fractions (WAFs) have been used in aquatic toxicity tests with AOL. The same holds for the other tar oils. Thus, results of short-term tests with tar oils are given as loadings (LL/EL50, NOELR).

Short-term aquatic toxicity has been examined in fish, daphnia and alga (OECD TG 203, 202, and 201, respectively). In fish tests, semi-static and open test conditions were use. Test substances were AOH and wash oil. Tests with daphnia were performed under static conditions using open test vessels (test substances AOL and AOH) or under largely sealed/closed test conditions (test substance AOH). Algae were tested under static conditions in open vessels using the substances AOL and AOH.

The lowest acute toxicity value was obtained in the daphnia study with AOH under closed test conditions: LL50(48 h) = 22.4 mg/L (AOH, CS 06). Under open conditions, the corresponding values in daphnia were approximately 6 and 8 times higher: LL50(48 h) = 167 mg/L (AOH, CS 06) and 137 mg/L (AOL, CS 07).

These findings indicate that volatility of constituents in anthracene oils is substantial and that volatile components contribute to acute intoxication. It may be assumed that narcosis is the main underlying mechanism for the high intoxication by the volatile fraction.

All other toxicity data in fish and alga are significantly above 10 mg/L or 100 mg/L (based on loading):

Fish: LL50(96 h) = >100 mg/L (AOH, CS 06) and 79 mg/L (wash oil, CS 05)

Alga: EL50(72 h) = 25 mg/L (AOL, CS 07) and 48 mg/L (AOH, CS 06).

Inhibitory effect to micro-organisms:

A structure-related tar-oil (creosote) caused no substantial inhibition of a mixed microbial population but at high nominal concentrations (EL50 = 670 mg/L, OECD TG 209).

The short-term test results reported here demonstrate, that anthracene oil (AOL) as such as well as the other tar oils possess only a low toxicity to aquatic organisms. Data are not sufficiently different in order to unequivocally decide, which species is the most sensitive. Selection of the leading toxic effect will be based on results from the long-term aquatic toxicity studies with phenanthrene.

Long-term toxicity (tests with phenanthrene)

Several long-term aquatic toxicity tests are available for the test substance phenanthrene (marker substance, representative for AOL). Toxic effects in freshwater and marine water organisms were produced within its water solubility range.

Tests in freshwater were conducted with fish (ELS test, OECD TG 210), aquatic invertebrates (daphnia, OECD TG 202/211 and draft TG AFNOR), and with algae (Norme Francais EN 28692, EU Method C.3). Toxic effects in the marine compartment were studied with bacteria, annelids, crustaceans (short-term and long-term tests) as well as with molluscs and fish (short-term tests only). For marine species, only long-term results are presented below (polychaete worm Nereis (Neanthes) arenaceodentata and Zuiderzee (dwarf) crab Rhithropanopeus harrissi).

All results showed the same magnitude.

Freshwater species (measured values):

Fish: NOEC(28 d) = 11 µg/L (larval development) (Hooftman and de Ruiter, 1991)

Daphnia: NOEC(21 d) = 18 µg/L (reproduction) (Hooftman, 1991)

EC 10(7 d) = 13 µg/L (reproduction) (Bisson et al., 2000)

Alga: EC 10(72 h) = 26 µg/L (growth) (Bisson et al., 2000)

Saltwater species (nominal values):

Polychaete worm: LC 50(96 h) = 51 µg/L (emerging juvenile - early life stage) (Emery and Dillon, 1996)

LOEC(8 wks) = 20 µg/L (growth, fecundity, emerging juvenile production) (Emery and Dillon, 1996)

NOEC(8 wks) = 20 µg/L (mortality) (Emery and Dillon, 1996)

Zuiderzee crab: NOEC = 100 µgL (zoeal development until megalopa stage) (Laughlin and Neff. 1979)

The lowest NOEC identified was 11 µg/L (fish, larval development). NOECs for daphnia fell in the same range (13 and 18 µg/L). Toxicity in the marine compartment was not higher than with freshwater species.

The NOEC with fish (11 µg/L) is selected as starting point for derivation of PNECs. As toxicity to marine species is not higher than to freshwater species, the same NOEC is used for derivation of the PNEC aqua (marine water).