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Sediment toxicity

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sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)
GLP compliance:
yes (incl. QA statement)
The department of health of the government of the United Kingdom
Analytical monitoring:
Details on sediment and application:
- Method of mixing: Amounts of test item (63, 125, 250, 500 and 1000 mg) were separately added to 10 g aliquots of sand and mixed thoroughly.
The test item/sand mixtures were each separately added to 1 kg (dry weight) of formulated sediment and mixed with a large scale laboratory mixer to give the test concentrations of 63, 125, 250, 500 and 1000 mg/kg with a nominal moisture content of 40% of dry weight.
- Equilibration time: 2 days
- Controls: Yes, the control was prepared in a similar manner, without the addition of test item.
Test organisms (species):
Chironomus riparius
Details on test organisms:
- Source: Chironomus riparius derived from in-house laboratory cultures
- Handling of egg masses and larvae: Larvae were maintained in glass beakers with a 5-10 mm layer of fine quartz sand covered by reconstituted water (Elendt M4) in a temperature controlled room at approximately 20 °C. The lighting cycle was controlled to give a 16 hour light and 8 hour darkness cycle with 20 minute dawn and dusk transition periods. The cultures were gently aerated, so as not to disturb the substrate, through narrow bore glass tubes. The culture vessels were housed in a sealed clear perspex cabinet (breeding box) with cotton sleeves to enable access.
- Age of animals at beginning of exposure: 2-3 days old
- Feeding during test
- Food type: Tetramin® flake food
- Amount: 0.5 to 2.5 mg
- Frequency: daily

- Acclimation period: No
Study type:
laboratory study
Test type:
Water media type:
Type of sediment:
artificial sediment
Limit test:
28 d
Exposure phase:
total exposure duration
226 - 250 mg/L as CaCO3
Test temperature:
21 - 23 °C
6 -9
Dissolved oxygen:
8 ± 1 mg/L
0.0054 and 0.036 mg/L as NH3 for the control on Days 0 and 28 respectively and 0.0037 and 0.092 mg/L as NH3 for the 1000 mg/kg test group on Days 0 and 28 respectively
Nominal and measured concentrations:
Nominal: 63, 125, 250, 500 and 1000 mg/kg (dry weight of sediment)
Details on test conditions:
- Test container (material, size): 400 mL glass beakers
- Depth of sediment and overlying water: The prepared sediments were dispensed to glass beakers to give a 2 cm layer and was then covered with a 8 cm depth of test water (sediment:water ratio, 1:4).
- Aeration: yes
- Aeration frequency and intensity: approximately 1 bubble/second

- No. of organisms per container (treatment): 20
- No. of replicates per treatment group: 4 +1 (replicate for 10-day larval survival and growth data)
- No. of replicates per control: 4 +1 (replicate for 10-day larval survival and growth data)
- Feeding regime: daily
- Type and preparation of food: Tetramin® flake food
- Amount of food: The larvae were fed at a rate of 0.25 to 0.50 mg Tetramin® flake food per larva per day for the first 13 days and 0.63 to 1.25 mg Tetramin® flake food per larva per day thereafter

- Type of water: Elendt medium (M4)

A defined formulated sediment was used with the following composition:
- Industrial quartz sand 76% w/w
- Kaolinite clay 20% w/w
- Sphagnum moss peat 4% w/w

- Photoperiod: 6 hour light and 8 hour darkness cycle with 20 min dawn and dusk transition periods.
- Light intensity: 896 - 996 Lux

EFFECT PARAMETERS MEASURED : emergence daily, larval survival and growth data at day 10
Reference substance (positive control):
28 d
Dose descriptor:
Effect conc.:
>= 1 000 mg/kg sediment dw
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
emergence rate
Details on results:
The 28-Day EC50 (reduction in emergence) based on nominal test concentrations was greater than >1000 mg/kg. The No Observed Effect Concentration was 1000 mg/kg.
The EC50 (development rate) based on nominal test concentrations was greater than 1000 mg/kg.
It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/kg.

Table 1. Validity criteria for OECD 218.

Criterion from the guideline


Validity criterion fulfilled

The emergence in the control must be at least 70% at the end of the test.



C. riparius and C. yoshimatsui emergence to adults from control vessels should occur between 12 and 23 d after their insertion into the vessels. For C. tentans, a period of 20 to 65 d is necessary.

> day 16


At the end of the test, pH and the dissolved oxygen concentration should be measured in each vessel. The oxygen concentration should be at least 60% of the air saturation value (ASV) at the temperature used and the pH of the overlying water should be in the 6-9 range in all test vessels.


pH 6-9


The water temperature should not differ by more than ± 1.0 °C.

22 ± 1 °C



Validity criteria fulfilled:
Please refer to table 1 in section "Any other information on results incl. tables"

Description of key information

 The substance is not toxic to sediment organisms  (NOEC(28 d)   1000 mg/kg).

Key value for chemical safety assessment

Additional information

The toxicity of the substance to sediment-dwelling larvae of Chironomus riparius was tested according to OECD 218 (GLP)).

Following a preliminary range-finding test 80 larvae of Chironomus riparius were exposed in groups of 20 (four replicates of 20 larvae per concentration) to formulated sediment spiked with test item concentrations of 63, 125, 250, 500 and 1000 mg/kg for a period of 28 days. The numbers of emerged adult midges were recorded daily. A another replicate with 20 larvae of each test group was prepared and sacrificed on Day 10 of the exposure period to determine the 10-Day larval survival and growth data. Inspection of the data showed no significant differences in larval survival and growth, in terms of mean larval dry weight, between the control and each test group after 10 days.

The toxicity of the test item to the sediment-dwelling larvae of Chironomus riparius gave a 28-Day EC50 (emergence) of > 1000 mg/kg. The NOEC (28 d) was ≥ 1000 mg/kg. The EC50 (development rate) based on nominal test concentrations was > 1000 mg/kg.

Based on the available study results, the substance is not considered toxic to sediment organisms.