Pitch, coal tar, high-temp., < 1% 4- to 5-membered condensed ring aromatic hydrocarbons

Endpoint summary

Description of key information

Under environmental conditions, there will be no or only a very low environmental availability of the substance Pitch, coal tar, high-temp., < 1% 4- to 5-membered condensed ring aromatic hydrocarbons [EC no. 701-305-8] (CTPhtht) or its constituents. There are no toxicity results in the soil compartment for CTPhtht itself. For comparison, CTPhtht does not show acute aquatic toxicity and is supposed to generate no chronic toxic effects that are relevant for classification. However, for precautionary reasons, environmental risk assessment will take PAHs into account with benzo[a]pyrene (BaP) as marker substance, although the results of BaP describe worst-case conditions rather than being representative of CTPhtht itself.

The toxicity values found in literature for BaP show high variation from almost 1000 mg/kg soil down to less than 10 mg/kg soil dw. In the risk assessment report on Pitch, coal tar, high temp. [CAS no. 65996-93-2] [EU 2008], the estimate of 2.6 mg/kg soil dw for a NOEC/EC10 of reproduction in earthworm based on results of Achazi et al. (1995) is considered relevant for deriving a PNEC.

Additional information

The following summary is from EU 2008:

"Chronic toxicity studies with benzo[a]pyrene are available for 2 species each of terrestrial annelids, crustaceans, and collembola. No effects were found for the studies with Folsomia species (Sverdrup et al., 2002e; Bleeker et al., 2003; Droge et al., 2006). For annelids, effects were observed in one study only, with Eisenia fetida being slightly more sensitive than Enchytraeus crypticus (Achazi et al., 1995). The NOECs for reproduction are 2.6 and 8.7 mg/kg dw respectively, recalculated to a soil with 2% organic carbon.

For the crustaceans Oniscus asellus and Porcellio scaber effects were observed in tests that were conducted in contaminated food with an organic matter content of more than 90 % (Van Straalen & Verweij, 1991; Van Brummelen & Stuijfzand, 1992; Van Brummelen et al., 1996). This way of exposure introduces a large extrapolation to a soil with 3.4 % organic matter (2 % organic carbon). In a third study the growth efficiency was studied during 4 weeks (Van Straalen & Verweij, 1991). The EC10 for growth efficiency of male isopods of 0.53 mg/kg dw is comparable with the concentrations at which 10 % effect or more was observed in the study by Van Brummelen & Stuijfzand (1992) ...."

In the EU RAR for Pitch, coal tar, high temp. [CAS no. 65996-93-2] (EU 2008), the EC10 value of 0.53 mg/kg dw from the growth efficiency study with the isopode Porcellio scaber is used to derive a PNEC (AF of 10). As this value is generated on food, it is considered to be not comparable to soil conditions and hence not sufficiently reliable to represent terrestrial toxicity of BaP. Therefore, the lowest NOEC of 2.6 mg/kg dw for reproduction with the annelid Eisenia fetida is considered relevant as starting point for PNEC derivation. Data for crustaceans is considered not to be sufficiently robust and is omitted from the assessment. Therefore, the AF is increased to 50. PNECs obtained by both methods are the same (0.05 mg/kg dw).

Reference:

EU 2008: European Union Risk Assessment - Report of COAL-TAR PITCH, HIGH TEMPERATURE (Final draft version May 2008), URL: http://echa.europa.eu/documents/10162/433ccfe1-f9a5-4420-9dae-bb316f898fe1