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Sediment toxicity

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Description of key information

No data on pitch, coal tar, high-temp. (CTPht) as such is available. As substitute, data of several polycyclic aromatic hydrocarbons are used in combination to characterise the sediment toxicity of CTPht. Short-term and long-term toxicity studies have been performed. The lowest toxicity values from short-and long-term tests have been selected to specify the toxicity of CTPht to sediment dwelling organisms.

Key value for chemical safety assessment

EC50 or LC50 for freshwater sediment:
68 mg/kg sediment dw
EC50 or LC50 for marine water sediment:
220 mg/kg sediment dw
EC10, LC10 or NOEC for freshwater sediment:
15 mg/kg sediment dw
EC10, LC10 or NOEC for marine water sediment:
13 mg/kg sediment dw

Additional information

Studies on sediment toxicity of CTPht itself could not be located. Information resulting from studies with PAH as constituents of CTPht are also not widespread. Data are only available for a limited number of PAH. Especially for higher molecular weight PAH, no information on sediment toxicity was identified. Taking into account the composition of CTPht, data on sediment toxicity are available for phenanthrene, fluoranthene, pyrene, and benzofluoranthenes. Studies using benzo[a]pyrene could not be located. This substance serves as marker substance for CTPht and is used as representative for the toxicity of CTPht regarding other endpoints. In the absence of sediment toxicity data for benzo[a]pyrene, toxicity of CTPht to sediment dwelling organisms will be evaluated using data obtained with the PAH constituents of CTPht specified above.


Sediment toxicity of PAH has extensively been evaluated in the EU Risk Assessment Report of pitch, coal tar, high-temp. (EU 2008). The sediment toxicity of PAH reported here is based on this evaluation. In Appendix A.3 (see below under references), numerous toxicity values related to various test species and PAH as test materials are listed. From these data, tests were selected that were performed using at least two of the PAH cited above as test materials. This way, the potency of toxic/adverse effects caused by different PAH could be compared. Further criteria were that the studies covered taxa different from each other and that toxicity values reported were among the lowest values in the list.


The studies selected include short-term tests covering an exposure period of 4 or 10 days (Verrhiest 2001a, Swartz 1997, Lotufo and Fleeger 1996, and Lotufo 1997). Effect parameter determined was mortality. For long term-tests, the exposure period was 14 or 28 days (Verrhiest 2001b, Lotufo and Fleeger 1996 and Lotufo 1997). The effect parameter monitored were mortality/growth and reproduction.


There are freshwater test results available for three different taxonomic groups (annelids, crustaceans, and insect larvae) representing different habitats and living conditions. All cover short term exposure (Verrhiest 2001a/b, Lotufo and Fleeger 1996), while one includes also long term-exposure (Lotufo and Fleeger 1996). Tests in estuarine/saltwater sediments were performed using test organisms of two different taxonomic groups (amphipods and copepods). One covers short term exposure (Swartz et al. 1997), while the study with the meiobenthic copepod (Lotufo 1997) includes short-term and long-term exposure.


Data of the different studies are summarised in the following table. To make values comparable, they are recalculated to a standard sediment with 10 % organic carbon content.


 


Values in mg/kg sediment dw, normalised to a standard sediment with 10 % organic carbon


 


















































































































































              Freshwater



              Study Verrhiest 2001



Exposure 10 d
(effect: mortality)



Substance



10-d LC50



 



EC10



10-d NOEC



Chironimus riparius



phenanthrene



68



 



 



50



fluoranthene



73.5



 



< 15



benzo[k]fluoranthene



> 1500



 



1500



Exposure 14 days
(effect: mortality)



 



14-d LC50



14-d EC10



14-d NOEC



Hyalella azteca



phenanthrene



103



 



50



fluoranthene



26



 



15



benzo[k]fluoranthene



> 1500



 



1500



              Study Lotufo 1996



Exposure 10 days
(effects: mortality)



 



10-d LC50



Exposure: 28 days
(effect reproduction)



28-d EC10



28-d NOEC



Limnodrilus hoffmeisteri



phenanthrene



4257



 



1077



670



pyrene



n.d.



54



< 1400



              Salt water



              Study Swartz 1997



Exposure 10 d
(effect: mortality)



 



10-d LC50



 



 



 



Rhepoxynius abronius



phenanthrene



220



 



fluoranthene



331



pyrene



281



Study Lotufo 1997



 



 



Exposure 4 days
(effects: mortality)



 



4-d LC50



Exposure 14 days
(effects: reproduction)



14-d EC10



14-d NOEC



Schizopera knabeni



phenanthrene



3153



 



13



< 373



fluoranthene



> 14000



67



< 407



n.d.: not determinable


 


Toxicity data indicate that there is no clear relationship between individual PAH substances and toxic effects. There seems to be the tendency that toxicity to sediment microorganisms decreases with increasing size of PAH. But in some cases, toxicity of fluoranthene is higher than the toxicity of phenanthrene. Overall, at high toxicity levels (low effect values), differences between substances diminish when all studies are taken into account.


Sediment toxicity of CTPht will be characterised by the results of all its constituents that contribute data on sediment toxicity. Using the lowest values determined for effect and hazard identification, constitutes a worst case approach. The risk to sediment organisms caused by CTPht will be realised satisfactorily by this approach.


Comparing short-term freshwater and saltwater toxicity data shows that saltwater organisms are less susceptible to toxic effects (mortality) of PAH than freshwater organisms. The lowest long-term values (EC10 or NOEC) are comparable (13 or < 15 mg/kg sediment dw). The derivation of PNECs for freshwater and marine sediment will thus be based on the same value (13 mg/kg sediment dw, 14-d EC10 of Schizopera knabeni from the study of Lotufo 1997).


 


References:


EU (2008): European Union Risk Assessment Report - Coal-Tar Pitch, high temperature. The Netherlands (rapporteur) (URL:https://echa.europa.eu/documents/10162/433ccfe1-f9a5-4420-9dae-bb316f898fe1)


Appendix A.3 Table benthic toxicity data PAHs (Appendices to EU RAR, listed on p. 217)


(URL: https://echa.europa.eu/documents/10162/13630/trd_rar_app3_netherlands_pitch_en.pdf)

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