Pitch, coal tar, high-temp.

Endpoint summary

Additional information

Pitch, coal tar, high-temp. (coal-tar pitch, CTPht) is a solid consisting of a complex aromatic structure, which is practically insoluble in water (0.24 mg C/L), i.e. significantly less than 1 mg carbon/L at a loading of 1000 mg/L. Aquatic toxicity data based on coal tar pitch as test substance are presented below.

Pitch, coal tar, high-temp. contains polycyclic aromatic hydrocarbons as constituents in a quantity up to 7.5 %. One of the environmentally most relevant PAHs is benzo[a]pyrene. It is present in coal tar pitch in a percentage up to 1.5. As PAH may be released into the environment from coal tar 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 abundance and high environmental toxicity.

Relevant toxicity data will be reported below. PNEC derivation will be based on long-term aquatic toxicity data of benzo[a]pyrene as marker substance. In a second step, benzo[a]pyrene PNECs will be adjusted to total pitch, coal tar, high-temp., taking into account the total PAH content of CTPht (see below, CSR Sect. 7.6.).

Acute aquatic toxicity

Due to its poor solubility in water (see above and CSR Sect. 1.3), this material does not produce noticeable acute aquatic toxicity under standard test conditions in fish (OECD TG 203), in daphnia (OECD TG 202), and in algae (OECD TG 201). The EL50/LL50 values were consistently higher than 10 - 100 mg/L (loading).

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

Acute toxicity data of benzo[a]pyrene are available for aquatic invertebrates and algae. In a 24 h test with Daphnia magna, an EC50 of 59.7 µg/L was determined (Wernersson 2003). In an algal growth inhibition test, EC10 was 1.54 µg/L (nominal concentration, 0.78 µg/L measured TWA) (Bisson 2000).

Long-term aquatic toxicity of pitch, coal tar, high-temp.

Daphnia:

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 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 coal-tar pitch.

Alga:

In a test with alga (OECD TG 201), an ErL10 of 100 mg/L was established. A constant apparent inhibition of less than 10 % as compared with the untreated controls was noted from 10 to 100 mg/L (nominal exposure concentration, loading). However, there was not any concentration-dependent increase in growth inhibition until 100 mg/L. Therefore, this low-level effect was considered to be unrelated to the presence of the test substance.

Fish:

Long-term studies in fish are not available. However, they are not supposed to generate chronic toxic effects that are relevant for classification.

Long-term aquatic toxicity of the marker substance benzo(a)pyrene (BaP)

Fish:

In a limit test with zebra fish (equivalent to OECD TG 210 - Fish, early life stage toxicity), the 42-d NOEC was 4 µg/L. Relevant endpoint was larval development.

Aquatic invertebrates:

Long-term toxicity of BaP to aquatic invertebrates was tested in three experiments, one with freshwater daphnia and two with seawater oyster and sea urchin embryos, respectively.

In a test (AFNOR draft TG) with Ceriodaphnia dubia, an EC10 of 0.503 µg/L was observed (measured concentration, relevant endpoints mortality and reproduction).

The tests with seawater organisms are not based on test guidelines but on established experimental procedures. Effects of BaP on the embryonic development of oysters (Crassostrea gigas - shell development) and sea urchins (Strongylocentrotus purpuratus - gastrulation) were examined. Determination of BaP toxicity on oyster shell development resulted in EC10 values of 1.1 and 0.22 µg/L (without and with exposure to UV radiation, respectively).

In the study with sea urchin embryos, developmental (impeded gastrulation) and genotoxic effects (mitotic aberration) were examined. At the lowest dose tested (0.5 µg/L), effects on embryonic development could not be identified (NOEC 0.5 µg/L). However, significant mitotic aberration compared to controls was still present (LOEC 0.5 µg/L). As effects were seen at a level of only approx. 5%, this value is assessed to be in the range of EC10.

For derivation of PNECs, the lowest EC10 value (0.22 µg/L, oyster shell development) is applied.

Discussion of acute photo-toxicity of pitch

Notwithstanding these observations, coal tar pitch is being discussed to be classified for environmental hazard, as very low concentration of certain PAH, which are constituents of coal tar pitch, exhibit aquatic toxicity in the presence of UV light (photo-toxicity). No particular acute photo-toxicity study is available for pitch material, since photo-toxicity testing is no standard and has not been adopted as criterion for environmental classification.

However, based on weight of evidence, it can be explained that acute aquatic toxicity of coal tar pitch is very unlikely to occur in simulated sunlight:

The total of 18 aromatic substances leached from 100 mg/L of CTPht resulted in 1.3 – 1.4 µg/L (WSF). The concentrations of individual key PAHs in this water-soluble fraction (WSF) are compared with EC50/LC50 that were obtained under the influence of UV-light.

The following table compares the PAH concentrations achieved in the chronic daphnia study [NOACK et al 2009] (1st data column) to the lowest EC50 values in the presence of UV-light, (2nd data column).

The ratios of water concentrations-to-toxic values for single PAHs are far below 1, proving that toxic values will not be achieved. This finding provides strong evidence that acute aquatic photo-toxicity is very unlikely to arise from coal-tar pitch in contact with water.

	Mean (n = 5) [µg/L]	EC50 daphnia [µg/L] (+ UV)		EC50 : WSF ratio (mean)
Naphthalene	< LOQ			0.0
Acenaphthylene	< LOQ			0.0
1-Methylnaphthalene	< LOQ			0.0
2-Methylnaphthalene	< LOQ			0.0
Acenaphthene	0.063	>1000	Wernersson 2003	0.0
Fluorene	0.054	>1000	Wernersson 2003	0.0
Phenanthrene	0.252	378	Wernersson 2003	0.0
Anthracene	0.056	1.2	Oris and Giesy 1984; Allred and Giesy 1985	0.05
Fluoranthene	0.318	1.6	Spehar 1999	0.20
Pyrene	0.240	1.4	Wernersson 2003	0.17
Benz(a)anthracene	0.072	3.4	Wernersson 2003	0.02
Chrysene	0.080	0.7	Newsted and Giesy 1987	0.11
Benzo(b)fluoranthene	0.0033	4.2	Wernersson and Dave 1997	0.01
Benzo(k)fluoranthene	< LOQ			0.0
Benzo(a)pyrene	0.035	1.2	Wernersson 2003	0.03
Dibenz(a,h)anthracene	< LOQ	1.8	Wernersson 2003	0.0
Benzo(ghi)perylene	< LOQ			0.0
Indeno(1,2,3-cd) pyrene	< LOQ			0.0
Sum of 18 PAHs	approx. 1.33

LOQ: limit of quantitation = 0.030 µg/L; included in the total of 1.33 µg/L with LOQ/2 = 0.015 µg/L (8 values)

References:

Noack M, Stülten D, Noack U (2009): Pitch, coal tar, high-temp - Daphnia magna Reproduction Test, Limit-Test (Semi-Static, 21 d). Project-No. 070615HC, DR. U. NOACK-LABORATORIEN, Germany, 27 July 2009

Allred PM, Giesy JP (1985): Solar radiation-induced toxicity of anthracene to Daphnia pulex. Environ. Toxicol. Chem. 4, 219-226

Newsted JL and Giesy JP (1987): Predictive models for photoinduced acute toxicity of polycyclic aromatic hydrocarbons to Daphnia magna, Strauss, Cladocera, Crustacea. Toxicol Chem. 6, 445-461

Oris JT, Giesy JP, Allred PM, Grant DF, Landrum PF (1984): Photoinduced toxicity of anthracene in aquatic organisms: an environmental perspective. Stud. Environ. Sci. 25 (Biosphere: Probl. Solutions, ed. Veziroglu TN), 639-658

Spehar RL, Poucher S, Brooke LT, Hansen DJ, Champlin D, Cox DA (1999): Comparative toxicity of fluoranthene to freshwater and saltwater species under fluorescent light. Arch. Environ. Contam. Toxicol. 37, 496-502

Wernersson A-S (2003): Predicting petroleum phototoxicity. Ecotoxicol. Environ. Saf. 54, 355-365

Wernersson A.-S., Dave G. (1997): Phototoxicity identification by solid phase extraction and photoinduced toxicity to Daphnia magna. Arch. Environ. Contam. Toxicol. 32, 268-273