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Sediment toxicity

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Endpoint:
sediment toxicity: long-term
Data waiving:
other justification
Justification for data waiving:
other:
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
In respect of test design and feasibility:
- Standard sediment studies are designed to assess the effects of prolonged exposure to substances which persist in sediments over long time periods. The standard OECD guideline methods for long term sediment ecotoxicity require spiking of substrate with the test substance initially, with an equilibration phase and in-life exposure phase of several weeks duration, and replenishment during the test is not realistic.
- It is expected that test organism exposure could not be consistently maintained for test substance in a bioavailable form, or primary degradation products, for the duration of a long-term test, due to very rapid biodegradation and mineralisation of bioavailable alcohol in a sediment-water system.
- Considerable technical difficulties would be expected in the conduct of either short or long-term sediment ecotoxicity tests, due to the expected very rapid biotic removal (primary degradation and mineralisation) of bioavailable substance from such a test system.
- Sediment simulation studies (Federle and Itrich, 2010; Itrich, 2010) have demonstrated the very short sediment half-life for the 'readily bioavailable' alcohol 'pool' (see Section 5.2.2); similarly rapid degradation rates are anticipated for other substances in the carbon chain length range C6-24, including this substance.
- for tetradecan-1-ol, in two different natural sediments: half-life 0.04 days and 0.08 days (primary degradation); 0.4 days and 0.15 days (mineralisation)
- for octadecan-1-ol, in two different natural sediments: half-life 1.1 days and 0.04 days (primary degradation); 1.7 days and 0.2 days (mineralisation).
It is considered that this would prevent maintenance of ‘readily bioavailable’ alcohol in pore-water for the duration of a standard long-term test (28 days duration for OECD 225), or even a shorter-term test. (While the sorbed alcohol ‘pool’ has a longer biodegradation half-life (for tetradecan-1-ol, in two different natural sediments: half-life 11.4 days and 23.1 days; for octadecan-1-ol, in two different natural sediments: half-life 17.3 days and 34.7 days (primary degradation)), alcohols are also ‘less bioavailable’ in the sorbed state).
- Please refer to discussion of the long-term aquatic invertebrate and fish studies which were complicated by the rapid degradation in the test system (Section 6.1.2 and 6.1.4).
- Please refer to discussion of the method development for the adsorption/desorption study (decan-1-ol) with natural soils, which was complicated by the rapid removal of test substance in non-sterilised soils (Section 5.4.1 and 5.2.3).
In the context of the chemical safety assessment:
- The substance is readily biodegradable and is very rapidly degradable in all compartments relevant to the environment (please refer to discussion in Section 5.2 of the IUCLID technical dossier for further information).
- In the wider environment, sediment biota are adapted to exposure to fatty alcohols from natural sources (please refer to Section 5.5 of the IUCLID technical dossier for further information).
- The exposure assessment indicates in the course of normal use some releases of alcohols to waste water is possible from both local and wide-dispersive uses. However, investigations have demonstrated that for both freshwater and marine sediments, LCAAs from anthropogenic sources are a minor proportion (1% or less in river environments) of the total present (see Section 5.5 on monitoring data).
- In general it is reasonable to conclude that natural freshwater and marine sediment biota would already be well-adapted to the presence of fatty alcohols from exposure to the many natural sources and the additional exposure to anthropogenic alcohols would not be expected to be a significant concern particularly given that biodegradation would be rapid following release. As such in accordance with column 2 in REACH Annex X, the chemical safety assessment does not indicate a need to investigate further the effects of the substance and/or relevant degradation products on sediment organisms.
Reason / purpose for cross-reference:
data waiving: supporting information
Reason / purpose for cross-reference:
data waiving: supporting information
Reason / purpose for cross-reference:
data waiving: supporting information
Reason / purpose for cross-reference:
data waiving: supporting information
Endpoint:
sediment toxicity: short-term
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted according to a modified OECD guideline, no mention of GLP, no analytical monitoring and lack of water quality measurements.
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 850.1735 (Whole Sediment Acute Toxicity of Invertebrates, freshwater)
Deviations:
yes
Remarks:
the media used was soil and water
GLP compliance:
not specified
Analytical monitoring:
no
Vehicle:
yes
Details on sediment and application:
PREPARATION OF SPIKED SEDIMENT

- Pooling or mixing of different substrates: soil and water

- Method of mixing: not reported

- Details of spiking: sand spike, using 10% of the total dry weight of soil. This involved adding an appropriate amount of compound to analar grade acetone to form a stock solution for the 1000 mg/kg dose. Aliquots of the stock solution were then diluted with acetone to prepare lower doses. Acetone solutions were added to silica sand in 500 ml amber glass jars. Mixtures were mixed thoroughly with a stainless steel spatula. The acetone was left to evaporate in a fume cupboard, leaving the test item coated onto the sand. Appropriate amount of moist soil was added to each of the glass jars. The dosed or undosed sand was incorporated into the bulk of the soil using a paletted knife. Jars were then sealed with screw top lids containing aluminium foil inserts and tumbled overnight (ca. 16 h) on a rotary soil tumbler 50 rpm.

- Equilibration time: not reported

- Controls: One aliquot of sand was dosed with acetone only to serve as solvent control. A jar with an aliquot of sand only served as untreated control - both with the appropriate amount of moist soil added thereafter.

- Chemical name of vehicle (organic solvent, emulsifier or dispersant):

- Concentration of vehicle in test medium (stock solution and final test solution): acetone solutions was added between 1-7 ml to 5-35g of silica sand. The sand was left to evaporate the acetone completely before initial exposure, so that the concentration of vehicle would be negligible.

- Evaporation of vehicle before use: yes


PREPARATION OF SPIKED WATER

- Details of spiking: not spiked
Test organisms (species):
other: Heterocypris incongruens
Details on test organisms:
TEST ORGANISM

- Common name: ostracods

- Justification for species other than prescribed by test guideline: testing new method

- Source: obtained as dormant cysts in test kits (Ostracodtoxkit F. Chronic "direct contact" Toxicity Test for Freshwater Sediments, MicroBio Tests Inc. Deinze, Belgium).

- Breeding conditions: as test kit instructed. Organism were hatched in standard hard water in a covered petri dish for 52 h at 25 degC before introduction to the prepared soil.

- Age of animals at beginning of exposure: a few hours old

- Feeding during test

- Food type: algae powder (Spirulina sp, provided with the toxkit)

- Amount: one tube

- Frequency: once, four hours before the test began



ACCLIMATION

- Acclimation period: none
Study type:
laboratory study
Test type:
static
Water media type:
freshwater
Limit test:
no
Duration:
6 d
Exposure phase:
total exposure duration
Test temperature:
25 +/- 2 degC
pH:
not reported
Dissolved oxygen:
not reported
Nominal and measured concentrations:
Nominal concentrations: 0, 10, 30, 100, 300, 1000 mg/kg
Details on test conditions:
TEST SYSTEM

- Test container (material, size): polystyerene, multi well plates, supplied with the Ostracodtoxkit F.

- Amount of soil or substrate: 300ul og either reference sediment (supplied with the kit) or treated soil

- No. of organisms per container (treatment): 10

- No. of replicates per treatment group: 3

- No. of replicates per control: 3

- No. of replicates per vehicle control: 3



SOURCE AND PROPERTIES OF SUBSTRATE

- Geographic location: Heath Farm, Leicester Lane, LandLook (Midlands), Leamington Spa, from Dr Graham Beard. OS map reference 32896926.

- Pesticide use history at the collection site: assumed to be pesticide free, as the field the soil was taken from land that had been set aside for 3-4 years.

- Collection procedures: the soil was sieved to 2 mm.

- Sampling depth (cm): 5-20cm to avoid surface root mat

- Soil texture

- % sand: 63.8%-64.8%

- Soil classification: sandy loam soil. The soil is described as soil series, Bomsgrove, standard soil number 33, variant.

- Organic carbon (%): 1.3%

- Maximum water holding capacity: ca. 40%

- Pretreatment of soil: the soil was treated with gamma radiation (27 KGy) in order to kill the indigenous nematodes and potential predators. However observation from extracted fresh soil indicated that interference from the indigenous population was likely to be insignificant. Consequently, the definitive test were carried out using unsterilised soil.

- Storage: stored in closed black plastic bags at 4 degC until required.


OTHER TEST CONDITIONS

- Photoperiod: plates were incubated in the dark

-Other: animals were fed with 3x10^7 algal cells


EFFECT PARAMETERS MEASURED: Growth was determined by measuring the length of ostracods at the beginning (on a sub-sample) and end of the exposure period (surviving individuals). Measured once the ostracods were fixed in Lugols solution and via a calibrated graticule under a binocular microscope. Mortality (immobilisation) was measured at the end of the test.


VEHICLE CONTROL PERFORMED: yes


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 3

- Range finding study: no
Reference substance (positive control):
yes
Remarks:
dimethoate
Duration:
6 d
Dose descriptor:
EC50
Effect conc.:
150 mg/kg sediment dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: reproduction and survival
Details on results:
- Mortality at end of exposure period: 100% at 1000 mg/kg

- Other biological observations: 67% growth inhibition was observed 300 mg/kg dw dose.

See table 1 for details on results with other species.
Results with reference substance (positive control):
- Results with reference substance valid? yes

- Relevant effect levels: 160 mg/kg
Reported statistics and error estimates:
Probit analysis (Finney 1971) was used to determine EC50 values and their corresponding 95% intervals in definitive tests.

Table 1. Summary of findings.

Concentration (mg/kg dw soil) Number alive  Number dead/missing  Effect (%) 
Control  10 
Control  10 
Control  10 
Solvent control  10 
Solvent control  10 
Solvent control  10 
30  20 
30  10  0
30  10 
 100  9  1  10
 100  9  1  10
 100  10  0  0
 300  8  2  20
 300  7  3  30
 300  6  4  40
 1000  0  10  100
1000   0  10  100
 1000  0  10  100

Validity criteria fulfilled:
yes
Remarks:
on the data provided, however not enough data on water quality
Conclusions:
A 6 d EC50 value of 150 mg/kg dw soil has been determined for the effects of the test substance on population numbers of the ostracod H. incongruens.
Executive summary:

Short-term toxicity data are available for decan-1 -ol. The test was carried out with the sediment organism Heterocypris incongruens using a medium that was a mixture of soil and water and can therefore been considered as a sediment exposure. The data show that the C10 alcohol had an EC50value of 150 mg/kg d.w. This is the only available data.

Description of key information

In accordance with section 2 of REACH Annex XI the study does not need to be conducted because it is technically not possible.

Key value for chemical safety assessment

Additional information

Short term sediment toxicity

A 6-d EC50 value of 150 mg/kg dw soil (1.3% organic carbon) has been determined for the effects of the test substance on population numbers of the ostracod H. incongruens. This is a reliable non-guidance study looking at the effects in a soil and water mixture.

The study reflects the lowest value that is available for this endpoint. However this study is shorter than the guidance short-term toxicity study and is not considered to be useful to assess the sediment compartment where longer-term exposure is more relevant.

 

Long term sediment toxicity

Testing for sediment toxicity is not considered necessary because: 

PNECsediment has been calculated from PNECfreshwater on the basis of the equilibrium partitioning method. In accordance with Annex XI, section 2, the long-term toxicity effects studies to sediment dwelling organisms (required in Section 9.5.1) do not need to be conducted as the study is technically not possible. This is due to the very short sediment half-life once desorbed (see the discussion of Biodegradation in water and sediment for further details), preventing maintenance of exposure concentrations.

 

PNECsediment has been calculated from PNECfreshwater on the basis of the equilibrium partitioning method (EQPM). Sediment hazard assessment is based on the EQPM PNECs derived from the aquatic data.

 

For comparison, concentrations of decanol in natural sediments in the range <0.01 - 0.4 mg/kg dwt were reported from reliable monitoring data (Mudge, 2015).