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Aquatic toxicity of anthracene oil < 50 ppm BaP (anthracene oil low BaP, AOL, composite sample CS 07) itself was only tested in a short-term aquatic toxicity tests 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 > 50 ppm BaP (anthracene oil high BaP, AOH, composite sample CS 06), wash oil (composite sample CS 05), and creosote. All these oils are UVCB 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 toxicity of AOL.

Long-term aquatic toxicity tests with anthracene oil < 50 ppm BaP could not be identified. Tests with phenanthrene are used instead to characterise the long-term aquatic toxicity of AOL. AOL contains mainly 3-ring aromatic compounds and to a lesser extent PAHs with >=4 rings (see Chapter 1.). 2-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. Its toxic potency is representative for the aquatic toxicity of the other PAH. Phenanthrene can be used as substitute 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 sealed/closed or largely open test vessels ((test substances AOH and AOL / AOH respectively). 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 (Anthracene oil high BaP, CS 06). Under open conditions, the corresponding values in daphnia were approximately 6 and 8 times higher: LL50(48 h) = 137 mg/L (anthracene oil low BaP, CS 07) and 167 mg/L (anthracene oil high BaP, CS 06).

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 (anthracene oil high BaP, CS 06) and 79 mg/L (wash oil, CS 5)

Alga: EL50(72 h) = 25 mg/L (anthracene oil low BaP, CS 07) and 48 mg/L (anthracene oil high BaP, 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 complete anthracene oil < 50 ppm BaP 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 tests with phenanthrene.

Long-term toxicity (tests with phenanthrene)

Long-term aquatic toxicity tests are available only for the test substance phenanthrene. 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 using the polychaete worm Nereis (Neanthes) arenaceodentata.

All results showed the same magnitude (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)

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)

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.