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Sediment toxicity

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Reference
Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
March 2013 - October 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: OECD 225: Sediment-water Lumbriculus toxicity testing using spiked sedmiment
GLP compliance:
yes (incl. QA statement)
Details on sampling:
Samples of the freshly prepared sediments were taken from the solvent control and all test concentrations on Day-0 for quantitative analysis.

Samples of the overlying water and sediment were taken from the solvent control and all test concentrations on Days 0 and 28 for quantitative analysis.

Analysis for the concentration of test item in the pore water of the solvent control and all test concentrations was also performed on Days 0 and 28. The pore (interstitial) water was isolated by centrifugation (10000 g at 4 °C for 30 minutes).

Duplicate samples were taken and stored frozen for further analysis if necessary.
Details on sediment and application:
A defined formulated sediment was used in the following composition:

Industrial quartz sand: 75% w/w
Kaolinite clay: 20% w/w
Sphagnum peat, ground and air dried: 5% w/w
Powdered stinging nettle leaves: .0.25%
alpha cellulose : 0.25%

Calcium carbonate was added to bring the pH range within 7.0  0.5.

The Total Organic Carbon (TOC) of the prepared sediment was determined to be 2.0%.

Test organisms (species):
Lumbriculus variegatus
Details on test organisms:
The test was carried out using adult worms of Lumbriculus variegatus derived from in-house cultures.

The worms were maintained in 40 liter glass aquaria with a substrate of shredded paper hand towels. Dechlorinated tap water was continuously passed through the tank. The culture vessels were maintained in a temperature controlled room at approximately 21 ºC. 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 bone glass tubes.

The worms were fed with Tetramin® flake food at approximately 30 mL of a 5 g/100 mL dispersion every day. The Tetramin® flake food was prepared as a suspension in water and an appropriate volume added to the overlying water.

The diet and diluent were considered not to contain any contamination that would affect the integrity or outcome of the test.

Approximately 10 to 14 days prior to the start of the test, sufficient numbers of worms were dissected in the median body region with a scalpel. The posterior ends were placed in culture medium with a small amount of culturing substrate and left to regenerate new heads. This was conducted to synchronize the age of the worms.
Study type:
laboratory study
Test type:
static
Water media type:
freshwater
Type of sediment:
artificial sediment
Limit test:
yes
Duration:
28 d
Exposure phase:
total exposure duration
Hardness:
Day 0: 144 mg/L as CaCO3
Day 28: 172 mg/L as CaCO3
Test temperature:
Room temperature: 20 - 23 deg.C
Overlying temperature: 21 deg.C
pH:
Prepared test Sediment: 6.0 - 6.1
Water: 739 - 8.6
Dissolved oxygen:
8.1 - 8.7 mg/L
Ammonia:
0.0031 - 0.0310 (solvent control)
0.0050 - 0.280 (1000 mg/kg test concentration)
Nominal and measured concentrations:
Nominal: 7.5, 32, 100, 320 and 1000 mg/kg.
Details on test conditions:
The test water used for the range-finding and definitive tests was the same as that used to maintain the new para stock cultures. Laboratory tap water dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened (Elga Nimbus 1248D Duplex Water Softener) giving water with a total hardness of approximately 140 mg/L as CaCO3. After dechlorination and softening the water was passed through a series of computer controlled plate heat exchangers to achieve the required temperature. Typical water quality characteristics for the tap water as supplied, prior to dechlorination and softening, are given in Appendix 3.
Reference substance (positive control):
yes
Remarks:
pentachlorophenol
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
>= 1 000 mg/kg sediment dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
320 mg/kg sediment dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Duration:
28 d
Dose descriptor:
LOEC
Effect conc.:
1 000 mg/kg sediment dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
reproduction
Results with reference substance (positive control):
A positive control (Harlan Study Number: 41302621) used pentachlorophenol sodium salt (PCP-Na salt) as the reference item at concentrations of 1.0, 3.2, 10, 32 and 100 mg/kg (dry weight of sediment).

Exposure conditions for the positive control were similar to those in the definitive test.

Analysis of the numbers of surviving worms at the end of the test by the trimmed Spearman-Karber method (Hamilton et al 1977 ) based on nominal test concentrations gave the following results.

The No Observed Effect Concentration (NOEC) was 10 mg/kg.
The Lowest Observed Effect Concentration (LOEC) was 32 mg/kg.

The observed EC50 was within the 4.0 to 37.9 mg/kg range given in the Test Guideline.

Table 1: Number of surviving worms in the range finding test

Nominal
Concentration
(mg/kg)

Number of Surviving Worms

Day 28

Control

30

Solvent Control

33

1.0

33

10

39

100

33

1000

19

Table2     Worm Weight Data for the Range-Finding Test

Nominal
Concentration
(mg/kg)

Mean Individual Worm Dry Weight (mg)

Day 28

Control

1.82

Solvent Control

1.15

1.0

2.13

10

0.94

100

1.52

1000

2.01

Table 3: Number of surviving worms in the definitive test after 28 days

Nominal
Concentration
(mg/kg)

Number of Surviving Worms

Day 28

R1

R2

R3

R4

R5

R6

Control

21

5*

24

29

20

27

Solvent Control

27

28

26

24

25

29

7.5

15

24

8

23

-

-

32

23

20

20

24

-

-

100

13

27

13

27

-

-

320

28

26

12

25

-

-

1000

17

13

14

21

-

-


R1– R6= Replicates 1 to 6

*Determined to be an anomalous result and excluded from statistical analysis.

Validity criteria fulfilled:
yes
Remarks:
The dissolved oxygen concentration should be at least 30% air saturation value at end of test and pH of overlying water in the range 6-9, water temp should not vary by +-1 deg. C, control worms must increase by a factor of 1.8. All conditions were all met
Conclusions:
The 28 d EC50 (reproduction) based on nominal test concentrations was greater than 1000 mg/kg. The No Observed Effect Concentration was 320 mg/kg and the Lowest Observed Effect Concentration was 1000 mg/kg
Executive summary:

SUMMARY

Introduction

A study was performed to assess the toxicity of the test item on reproduction to the sediment-dwelling oligochaete,Lumbriculus variegatus. The method was based on The OECD Guidelines for the Testing of Chemicals, “Sediment-waterLumbriculusToxicity Test using Spiked Sediment”, OECD Guideline No. 225, October 2007.

 

 

Methods….

Following a preliminary range-finding test, worms ofLumbriculus variegatus(4 replicates of 40 worms) were exposed to formulated sediment spiked with test item at concentrations of 7.5, 32, 100, 320 and 1000 mg/kg for a period of 28 days. The numbers of worms and the dry weight data of these worms were recorded at the end of the test.

 

Further replicates were prepared for each test group and sacrificed on Days 0 and 28 for chemical analysis of the sediment and overlying water.

 

 

Results…….

The 28d EC50(reproduction) based on nominal test concentrations was greater than 1000 mg/kg. The No Observed Effect Concentration was 320 mg/kg. The Lowest Observed Effect Concentration was 1000 mg/kg. The Ec10 has not been reported due to the unsuitable nature of the data

 

Analysis of the sediment on Day 0 of the test showed the measured concentrations to range from 80% to 122% of nominal with the exception of the 7.5 mg/kg test concentration which showed that a concentration of 11% of nominal (152% in the repeat analysis) was obtained. This was considered to be due to the low nominal concentration and the fact that this was close to the Limit of Quantification (2.051 mg/kg) of the analytical method. Analysis of the overlying water on Day 0 showed measured concentrations to range from less than the LOQ, determined to be 0.0615 mg/L to 0.242 mg/L. Analysis of the interstitial water on Day 0 of the test showed measured concentrations to range from less than the LOQ, determined to be 0.308 mg/L, to 0.933 mg/L.

 

Analysis of the sediment on Day 28 of the test showed the measured concentrations to range from 25% to 80% of nominal. Analysis of the overlying water on Day 28 showed the measured concentrations to be less than the LOQ. Analysis of the interstitial water on Day 28 of the test showed measured concentrations to range from less than the LOQ to 37.9 mg/L.

Description of key information

One OECD 225 GLP study is available where the 28 NOEC is 320 mg/kg

Key value for chemical safety assessment

EC50 or LC50 for freshwater sediment:
1 000 mg/kg sediment dw
EC10, LC10 or NOEC for freshwater sediment:
320 mg/kg sediment dw

Additional information