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Sediment toxicity

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Description of key information

The lowest valid value for chronic toxicity to sediment organisms is a NOEC of 78 mg Sb/kg ww or 112 mg Sb/kg dw for Chironomus riparius (Heijerick and Vangheluwe, 2005).

Key value for chemical safety assessment

Additional information

Three reliable and relevant chronic sediment toxicity tests with different species are available. The test species all have different exposure routes, feeding habits and ecological niches: (1) the bottom-dwelling Hyalella azteca (crustacean) is a surface deposit and filter feeder, (2) Chironomus riparius (insect) burrows within the sediment with a combined surface and subsurface feeding behaviour, and (3) Lumbriculus variegatus (oligochaete) is a head-down deposit feeder that feeds well below the sediment-water interface.

In Heijerick and Vangheluwe (2003) the amphipod Hyalella azteca was exposed to various concentrations of trivalent antimony (SbCl3) in a sediment-water system. The amphipods were exposed for 28 days. After this period, they were separated from the sediment and placed in sediment-free chambers for another 14 days. During this period, survival (day 28, 35, 42), growth (day 28, 42) and reproduction (number of young per female produced from day 28 to 42) were measured. This study was performed with 13 replicates, five concentrations (range: 30.8-249 mg Sb/kg ww) and a control, with each replicate consisting of 10 amphipods. The 13 replicates were used as follows: four replicates were used for the 28-day growth and survival endpoints and eight for the measurements of survival and reproduction on day 35 and 42 (incl. growth). The remaining replicate was used for the performance of chemical measurements. The overlying water was renewed at least three times a week (±75%). The most sensitive endpoint was growth (both weight and length) after 28 days of exposure, which resulted in a NOEC of 87 mg Sb/kg ww (124 mg Sb/kg dry wt).

Larvae of the midge Chironomus riparius were exposed to a concentration range of SbCl3in a sediment-water system (Heijerick and Vangheluwe, 2005). The test procedure was based on the OECD draft proposal for a new guideline 218 “Sediment-Water Chironomid Toxicity Test Using Spiked Sediment” (Draft February 2001, adopted April 2004). Two-day old larvae were exposed to spiked sediment until the larvae transformed to the adult phase. Mortality and growth of the larvae, and emergence to midges were determined after 14 and 28 days of exposure. The study was performed with six concentrations (23- 445 mg Sb/kg ww) and a control (<1.4 mg Sb/kg ww), and 11 replicates per concentration, of which five replicates were used to determine survival and growth after 14 days of exposure, five to determine emergence after 28 days of exposure, and the remaining replicate to perform chemical analyses. The overlying water was renewed at least three times a week (±75% renewal). The most sensitive endpoint was growth (weight), which resulted in a NOEC of 78 mg Sb/kg ww.

Adults of the oligochaete Lumbriculus variegatus were exposed to a concentration range of SbCl3in a sediment-water system (Heijerick and Vangheluwe, 2005). The test procedure was based on the OECD draft “Bioaccumulation; Sediment test using benthic oligochaetes” (January 2000; 3rd revised draft) and the EPA Guideline 600/R-99/064 “Methods for measuring the toxicity and bioaccumulation of sediment-associated contaminants with freshwater invertebrates”, Section 13, Test Method 100.3 “Lumbriculus variegatus bioaccumulation test for sediments”. The test organisms were exposed for 28 days to the spiked sediment. At the end of the exposure period survival, reproduction and growth were monitored. The study was performed with six concentrations (23 - 445 mg Sb/kg ww) and a control (<1.4 mg Sb/kg ww), and 7 replicates per concentration, of which six replicates were used to determine survival, reproduction and growth after 28 days of exposure, and the remaining replicate to perform chemical analyses. The overlying water was renewed at least three times a week (±75% renewal). The most sensitive endpoint was growth (weight), which resulted in a NOEC of 78 mg Sb/kg ww.