Pitch, coal tar, high-temp.

Endpoint summary

Description of key information

Data for long-term toxicity of pitch, coal tar, high-temp. itself in soil could not be identified. Data for benzo[a]pyrene are used instead (read-across from supporting substance). BaP is selected as marker substance for the terrestrial toxicity of CTPht based on its ecotoxicological profile and on its abundance in CTPht.

Various studies are available. The most relevant soil toxicity values are an EC10 (30 d) of 2.6 mg/kg dw for the annelid Eisenia fetida and an EC10 (47 wk) and NOEC (4 wk) value of 12 mg/kg dw and 0.94 mg/kg dw, respectively, for the crustacea Porcellio scaber.

Additional information

There are no studies of terrestrial toxicity for pitch, coal tar, high-temp. (CTPht) itself.

Based on its toxicological profile and on its content in CTPht, benzo[a]pyrene (BaP) has been selected as key marker substance in CTPht for deriving a PNEC(soil):

The toxicity values for soil organisms found in studies with BaP show high variation from more than 1000 mg/kg soil dw down to less than 10 mg/kg soil dw. In the risk assessment report on coal-tar pitch [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 as relevant for deriving a PNEC.

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., 2002; 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 Oniscusa sellus 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 coal-tar pitch, high temp. (EU 2008), the EC10 value of 0.53 mg/kg dw from the growth efficiency study with the isopod 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]