Pitch, petroleum, arom.

Endpoint summary

Additional information

Pitch, petroleum, arom. (petro pitch) is a solid consisting of a complex aromatic structure which is practically insoluble in water (0.4 mg C/L), i.e. significantly less than 1 mg carbon/L at a loading of 1000 mg/L.Aquatic toxicity data based on petro pitch as test substance are presented below.

In addition, aquatic toxicity data of pitch, coal tar, high temp. are used, as chemical structure and constituents of both substances are very similar. Both show a very low water solubility and consist of a complex mixture of in part highly condensed PAH.

Petro pitch contains polycyclic aromatic hydrocarbons as constituents in a quantity of approx. 2 %. One of the environmentally most relevant PAHs is benzo[a]pyrene. It is present in petro pitch in a percentage up to 0.14 %. As PAH may be released into the environment from petro pitch during its use, risk assessment is also based on their presence as worst case scenario. Benzo[a]pyrene is selected as marker substance due to its quantity in petro pitch and its high environmental toxicity. Derivation of PNECs is based on aquatic long-term toxicity data of benzo[a]pyrene.

Acute aquatic toxicity

Due to the poor solubility of petro pitch in water, this material does not produce noticeable acute aquatic toxicity under standard test conditions in daphnia (OECD TG 202; Aniol et al. 2007a), and in algae (OECD TG 201, Aniol et al. 2007b). The EL50/LL50 values were consistently higher than 100 mg/L (loading). Acute data in fish have not been produced, since the structure-analogous coal tar pitch was not acutely toxic (OECD TG 203;Tadokoro et al.1991).

Coal tar pitch as supporting substance exhibited no inhibitory effects on microbial growth and activity.

Chronic aquatic toxicity (petro pitch and structure related coal tar pitch)

Daphnia:

No data is available for petro pitch itself.However, in a 21d reproduction study in daphnia (semi-static, OECD TG 211), no adverse effects were observed in the presence of a water-extract from 100 mg/L powdered coal tar pitch, the structure-analogue. The NOEC(nominal) was greater than 100 mg/L (nominal), which corresponded to a mean water-soluble fraction of 1.3 – 1.4 µg/L of 18 aromatic key compounds (16 EPA PAH plus 2). This again underlines the extremely low bioavailability of this kind of compounds.

Alga:

In a test with alga (OECD TG 201), the no-effect loading rate (NOELR) was 100 mg/L. There was no inhibition of the average specific growth rate by petro pitch at the limit test loading rate of 100 mg/L at any observation time. Growth stimulation rather than inhibition could be observed 24 - 72 h.

Fish:

Long-term studies in fish are not available. However, petro pitch is not supposed to generate chronic toxic effects that are relevant for classification taking into account test results for daphnia and alga.

Chronic aquatic toxicity (marker substance benzo[a]pyrene)

Daphnia:

Long-term toxicity of BaP to daphnia was examined in a test according to the French guideline series AFNOR using ceriodaphnia dubia (Bisson et al. 2000). EC10 (7d) was determined to 0.507 µg/L (meas.).

Alga:

In a test with alga similar to EU method C.3 using BaP as test substance, an EC10 (72 h) of 0.78 µg/L (meas.) was determined (Bisson et al. 2000).

Fish:

Long-term toxicity of BaP to fish was examined in an ELS study similar to OECD TG 210. A NOEC (42 d) of 4 µg/L (meas.) was determined.

Marine species:

Long-term toxicity of BaP was determined in two marine species (molluscs and echinoderms). EC10 (48h) for the embryonic development of the salt water oyster Crassostrea gigas under UV-radiation was 0.5 µg/L (meas.) (Lyons et al. 2002). NOEC for developmental toxicity (gastrulation) of the purple sea urchin Strongylocentrotus purpuratus was also 0.5 µg/L (nominal) (Hose et al. 1985).