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Sediment toxicity

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Description of key information

An older test on the toxicity of chloroform to methanogenesis is available. Two guideline-compliant long-term studies on the sediment organisms Chironomus riparius and Lumbriculus variegatus have been made available after their request under a EU RAR conclusion (i) program (Woodburn et al. 2006a, Woodburn et al. 2006b). The lowest NOEC of 4.5 mg/kg (dw) was found in the reliable study on midges (Woodburn et al. 2006a).

Key value for chemical safety assessment

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

Additional information

The test carried out by van Vlaardingen and van Beelen (1992) applied solutions of chloroform in methanol to sediment/water suspensions prepared from core samples taken from natural sediments of the river Rhine and containing primarily methanogenic mud. Test bottles were incubated at 20 °C for 11 days. Methane production was measured at the end of the exposure period. The EC10 and EC50 values were determined based on the inhibition of methane production: 5.5 and 6.9 mg/kg (dw), respectively.

Two recent studies on the sediment toxicity of chloroform had a testing period of 28 days. The tests used sealed glass jars and spiked sediment in a flow-through test system in order to maintain consistent sediment concentrations. Preliminary work had indicated that this system would permit maintenance of relatively stable chloroform concentrations in the sediment and required dissolved oxygen concentrations in the overlying water. The study on the midge Chironomus riparius followed the OECD Testing Guideline No. 218 with particular precautions to avoid chloroform volatilisation during the test period (Woodburn et al. 2006 a). The monitoring of the concentrations of chloroform in the overlying water and the sediment revealed good maintenance during the 28-day period of the test. The endpoints of interest in the study were the proportion of larvae emerged (emergence ratio) and the development rate. The development rate of the male midges turned out to be the most sensitive endpoint under investigation. The 28-day NOEC and LOEC values for the male development rate were 4.5 and 10.0 mg/kg (dw), respectively. The study on the oligochaete Lumbriculus variegatus followed a proposed OECD guideline, because no finalised standard guideline was available at the timepoint of the study (Woodburn et al. 2006 b). Over the 28-day exposure period, a good reproducibility in sediment concentrations and overlying water concentrations could be observed. The endpoints of interest in the study were the total number of live worms, the reproduction and the worm biomass. The NOEC and LOEC values for these three endpoints together were 19.2 and 36.9 mg/kg (dw), respectively.

The lowest NOEC has been determined in the guideline-compliant study on Chironomus riparius: 4.5 mg/kg (dw). The PNEC for the sediment that is derived from this NOEC (by applying a factor of 10) is 450 microgram/kg (dw). This is considerably lower than the PNECsediment (dw) derived in the draft European Union Risk Assessment Report by using the equilibrium partitioning method, which is 702 microgram/kg (ww) and 3230 microgram/kg (dw) (COM 2007).