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Sediment toxicity

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Description of key information

For three different sediment species representing different living and feeding conditions, the NOEC in a 28d-test is available. The lowest NOEC, based on measured concentrations, is  17.1 mg/kg dw (Total Organic Carbon 2.20%).

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:
17.1 mg/kg sediment dw

Additional information

Three invertebrate species associated with the sediment and representing different living and feeding conditions, were tested according to or in line with OECD TG 218 in compliance with GLP. The results of these tests are summarised in the below table. More information on the tests is provided below the table.

Test species

Guideline

Results (mg/kg dw) and 95% confidence limits

Remarks

Lumbriculus variegatus

 

Comparable to OECD 218

28d-NOECreprod.& 28d-NOECbiomass= 33.3 mg/kg

28d-EC50reprod. = 97 mg/kg.

Egeler and Gilberg 2005c

Total organic carbon 2.29%

nom. 33.3 mg/kg

~measured 17.1 mg/kg

Hyalella azteca

 

Comparable to OECD 218

28d-NOECsurvival& 28d-NOECbiomass= 40.6 mg/kg

28d-EC50survival= 198 <115 – 339> mg/kg

Egeler and Gilberg 2005b

Total organic carbon 2.33%

nom. 40.6 mg/kg,

~measured 18.4 mg/kg

 

Chironomus riparius

 

Comparable to OECD 218

28d-NOECemergence ratio= 400 mg/kg

28d-NOECratite midges= 200 mg/kg

28d-EC50emergence ratio= 642 <516-797> mg/kg

Egeler and Gilberg 2005a

Total organic carbon 2.24%

nom. 200 mg/kg,

~measured 102 mg/kg

 

The resulting NOECs are expressed based on the measured concentrations as indicated in the third column of the above table. For the safety assessment, the results are to be converted to a sediment containing 5% TOC in order to be comparable to the estimations for a 'standard sediment'.

The sediment was formulated from quartz sand, kaolinite clay and Sphagnum moss peat. Urtica powder was added as feed. The total organic carbon content was 2%. The sediment including the feed was spiked with test material solved in acetone. Each vessel contained a layer of sediment and the water volume was circa 4 times the sediment volume. The test animals were introduced after an equilibrium period of 1 week. Test concentrations were measured in the sediment, porewater as well as in overlying water.

 

In the test with Lumbriculus variegatus, the test organisms were exposed to nominal concentrations of 1.2, 3.7, 11.1, 33.3 and 100 mg/kg sediment dry weight. The actual concentrations in the sediment upon introduction of the test organisms were 52% of nominal. On day 14 the measured concentrations were within 80% of the concentrations on day 0. This was also the case for the highest concentration on day 28, but middle concentration fell below 80% (Belfroid and Blok 2006). Survival was not affected up to the highest test concentration of 100 mg/kg dw. Reproduction and growth were not affected up to 33 mg/kg dw. The reproduction was inhibited by 55% and growth was inhibited by 35% at 100 mg/kg (Egeler and Gilberg 2005). After correction for the actual concentration on day 0, the actual NOEC was 17.1 mg/kg dw (Belfroid and Blok 2006).

In the test with Chironomus riparius, the test organisms were exposed to nominal concentrations of 50, 100, 200, 400 and 1000 mg/kg dw of test material in the sediment. The actual concentrations in the sediment on day 0 were 50 to 67% of the target concentrations. At termination of the test the concentration was 84-89% of the concentration on day 0 (Belfroid and Blok 2006). The emergence ratio was not affected up to 400 mg/kg, whereas the development rate was not affected in any of the test concentrations. At concentrations ≥ 400 mg/kg(d.w.) an increasing percentage of fully emerged midges were dead and/or not able to fly (ratite) and also the percentage of dead, incompletely emerged midges increased at 400 - 1000 mg/kg (Egeler and Gilberg 2005a).Therefore the NOEC was 200 mg/kg dw (nominal); after correction for the concentrations on day 0, the actual NOEC was 102 mg/kg dw (Belfroid and Blok 2006).

In the test with Hyalella azteca, the test organisms were exposed to nominal concentrations of 1.2, 4.0, 12.7, 40.6 and 130 mg/kg sediment dry weight. The actual concentrations on day 0 of the test with Hyalella azteca were 43 to 47% of the intended concentrations in the sediment. On day 28 the concentrations were within 80% of the concentrations on day 0 (Belfroid and Blok 2005). Survival and biomass were not affected up to 40.6 mg/kg dw (NOEC), whereas growth was not affected up to the highest concentration of 130 mg/kg dw (Egeler and Gilberg 2005b). After correction for the concentrations on day 0 the actual NOEC was 18.4 mg/kg dw (Belfroid and Blok 2006).