Distillates (coal tar), heavy oils

Endpoint summary

Additional information

The substance distillates (coal tar), heavy oils (anthracene oil high (> 50 ppm) BaP, AOH - composite sample CS 06) [CAS no. 90640-86-1] is a UVCB and consists of a complex and within limits variable combination of polycyclic aromatic hydrocarbons (PAH). Manufacturing process excludes low molecular aromatic hydrocarbons (1- and 2-ring aromatics) as well as largely polycyclic aromatic hydrocarbons composed of 5 rings and above.

Main components are phenanthrene, anthracene (3-ring PAH), fluoranthene, pyrene, chrysene, and benz[a]anthracene (4-ring PAH) representing approx. 30 % of total AOH, each accounting for ca. 3 to 10 %. The majority of other components of AOH fall within the molecular size range of these five substances.

A key component of AOH is phenanthrene (7 – 10 %). Fluoranthene and pyrene are present in similar amounts.In analogy to the structure-related anthracene oil (low (< 50 ppm) BaP, AOL) [CAS no. 90640-80-5], the key component phenanthrene is considered to adequately represent the PAH-related environmental toxicity of AOH. It is one of the most abundant components in AOH. Therefore, phenanthrene is selected as marker substance to represent the environmental toxicity of AOH.

Aquatic toxicity of AOH (composite sample CS 06) itself was only tested in short-term toxicity tests with fish and aquatic invertebrates (daphnia) and in a toxicity test with algae. Additional short-term tests have been performed using three other closely structure-related tar oils: anthracene oil (low (< 50 ppm) BaP, AOL - CS 07) [CAS no. 90640-80-5], creosote oil, acenaphthene fraction (wash oil, WO - CS 05) [CAS no. 90640-84-9], and creosote [CAS no. 8001-58-9]. All these oils are UVCB substances of complex composition with a low water solubility comprising PAH. The nature of constituents coincide closely, while the content of single substances in the oils is of the same magnitude. Therefore, these tar oils are used complementary to define the short term aquatic toxicity of AOH.

Long-term aquatic toxicity tests with AOH could not be located. Tests with phenanthrene are used instead to characterise the long-term aquatic toxicity of AOH as phenanthrene was selected as marker substance for the PAH related environmental toxicity of AOH (see above).

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

Due to the complex composition and variable but low solubility of its components, water solubility of AOH 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 AOH. 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 used. Test substances were AOH and wash oil. Tests with daphnia were performed under static conditions using sealed/closed and largely open test vessels (test substances AOH and AOH / AOL, respectively). Algae were tested under static conditions in open vessels using the substances AOH and AOL.

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, AOH, CS 06). Under open conditions, the corresponding values in daphnia were approximately 6 and 8 times higher: LL50(48 h) = 167 mg/L (anthracene oil high BaP, AOH, CS 06) and 137 mg/L (anthracene oil low BaP, 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 (anthracene oil high BaP, AOH, CS 06) and 79 mg/L (wash oil, WO, CS 05)

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

The short-term test results reported here demonstrate, that anthracene oil high (> 50 ppm) BaP (AOH) as well as the other tar oils possess only a low toxicity to aquatic organisms. Data are not sufficiently different 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 is represented by tests with the marker 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, semi-static, OECD TG 210), with aquatic invertebrates (daphnia; intermittent flow-through, OECD TG 202/211 and semi-static, draft TG AFNOR), and with algae (static, 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)

          EC10(7 d) = 13 µg/L (reproduction) (Bisson et al., 2000)

Alga: EC10(72 h) = 26 µg/L (growth) (Bisson et al., 2000)

Polychaete worm: LC50(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.

Inhibitory effect to micro-organisms (test with creosote)

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).