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Environmental fate & pathways

Biodegradation in soil

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Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study is reliable and primarily addresses ecotoxicity testing of several soil organisms. As such it is not a biodegradation guideline study, although degradation is discussed.
Qualifier:
according to guideline
Guideline:
other: Environment Canada 2004. EPS 1/RM/43 Biological Test Method: Tests for Toxicity of Contaminated Soil to Earthworms (Eisenia andrei, Eisenie fetida or Lumbricus terrestris). Method Development and Applications Section, Environment Canada, Ontario.
Deviations:
yes
Remarks:
This is an ecotoxicological test, although recovery of the test material was measured at the end of the test, which can be indicative of potential degradation.
GLP compliance:
not specified
Test type:
laboratory
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Radiolabelling:
no
Oxygen conditions:
not specified
Soil classification:
not specified
Details on soil characteristics:
A sandy soil (Valcartier, Quebec) was collected, sieved and homogenized in 2008. The test soil was selected to maximise chemical recovery and bioavailability to the test organisms, as prior tests conducted in a clay loam soil, rich in organic matter resulted in poor chemical recovery. However, preliminary tests using the sandy soil demonstrated that the soil was less than optimal for invertebrate reproduction, and therefore, the soil was amended with air-dried, hand-sieved (2-mm) Sphagnum sp. peat moss, on a dry weight basis, to increase overall organic matter content without compromising chemical recovery. The soil was amended with 2.5% peat. Calcium carbonate was added to peat-amended soils to counteract the acidity of the peat and maintain the original soil pH.

The test substance has low very water solubility. Soil treatments were prepared using stock solutions made with pure acetone allowed to evaporate for 24 hours. A solvent control mix of soil and acetone at the highest volume of solution was also prepared.

Formulated artificial soil was included as a negative control treatment for all tests to ensure that test cultures were healthy and to confirm test validity. This soil was formulated using 10% air-dried, hand-sieved (2-mm) Sphagnum sp. peat moss, 20% kaolin clay, 70% silica sand, deionized water, and calcium carbonate (to adjust the soil pH to 7.0 ± 0.5).
Soil No.:
#1
Duration:
>= 14 - <= 63 d
Soil No.:
#1
Initial conc.:
>= 0.23 - <= 3 000 mg/kg soil d.w.
Based on:
test mat.
Parameter followed for biodegradation estimation:
test mat. analysis
Soil No.:
#1
Temp.:
20 degrees C
Humidity:
No data
Microbial biomass:
No data
Details on experimental conditions:
Details for the earthworm ecotoxicity study are as follows: Environment Canada test protocols (2004) were followed; however, because of the increased density of the test soil, 250 mL glass jars were used instead of the recommended 500 mL Each test vessel had 230 g wet wt of test soil, and two sexually mature adults (ranging from 372 ± 82 to 390 ± 83 mg) were added to each replicate. Test vessels were incubated for 35 d, after which the adults were removed, and the test vessels incubated for another 28 d; there were ten replicates per test concentration. Nominal test concentrations for the test substance ranged from 0, 23 to 3000 mg/kg dry wt.Test vessels were incubated at 20 ± 3 degrees C for 16 h of light (ranging from 728 ± 341 to 899 ± 392 lux) and 8 h of dark (Environment Canada, 2004). Test organisms were fed between one-quarter and one-half a teaspoon of cooked oatmeal (Quaker OatsTM "quick" 3-5 min oatmeal) biweekly. Test measurements included: mean adult survival on day 35, mean juvenile production and mean individual juvenile dry mass at test end (day 63).
Soil No.:
#1
% Degr.:
12
Parameter:
test mat. analysis
Sampling time:
63 d
Transformation products:
not specified
Details on transformation products:
No data
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
not specified
Details on results:
On average, a 12 ±3.4% loss was observed between the beginning and end of the tests. The information presented above represents the range of durations and average degradation for ecotoxicity tests on earthworms, Collembola and plants.
Results with reference substance:
No data
Conclusions:
Degradation data were presented in ecotoxicity studies on earthworm, Collembola and plants with test durations ranging from 14 to 63 days. The mean test substance degradation across the studies was 12 ±3.4%.
Executive summary:

Ritchie et al (2013) undertook soil ecotoxicity testing on behalf of Canada's Chemical Management Plan (CMP) with a focus on potential effects to earthworms, Collembola and plants. In addition, information was provided on degradation of the test substance during these tests. On average, a 12 ±3.4% loss was observed between the beginning and end of the tests.

Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study planned
Remarks:
Study in progress, but not completed.
Study period:
To be completed end March 2021; full update to the dossier to be provided in April/May 2021.
Justification for type of information:
Due to the COVID situation and experimental difficulties the draft report for this study will not be available prior to March 2021. This was communicated to ECHA on 25 September 2020, and confirmed by Vilma Koppelomäki on 14 October 2020. Furthermore, the evaluating MSA (Austria, Dr Maximilian Kinzl) was informed, and confirmed that this delay would be acceptable to them, given the current situation in the world.
The lead registrant will update the dossier as soon as possible once the report is received. We would propose, on the basis of current information, that this will be April / May 2021.
This has duly been communicated through the ECHA webform; a copy is attached below for reference.
Qualifier:
according to guideline
Guideline:
OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)
Principles of method if other than guideline:
In line with the guideline, it will be attempted to identify degradation products occuring at 10% or more.
GLP compliance:
yes
Oxygen conditions:
aerobic/anaerobic
Endpoint:
biodegradation in soil: simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study is reliable. Although primarily a bioaccumulation study, beiodegradation information is provided. Peer-reviewed study comparing laboratory-based bioaccumulation in earthworms with in silico modelling predictions. Bioaccumulation study was carried out in accordance with OECD 317 guidelines by the National Research Council Canada and by the regulator Environment Canada.
Qualifier:
according to guideline
Guideline:
other: OECD 317
Deviations:
not applicable
Remarks:
Degradation data were reported as part of the bioaccumulation study
GLP compliance:
not specified
Remarks:
Published data, information on GLP was not specified
Test type:
laboratory
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Radiolabelling:
no
Oxygen conditions:
not specified
Soil classification:
not specified
Soil no.:
#1
Soil type:
clay loam
% Clay:
10
% Silt:
46
% Sand:
44
% Org. C:
5.4
pH:
5.6
Soil no.:
#2
Soil type:
sand
% Clay:
2
% Silt:
4
% Sand:
94
% Org. C:
0.36
pH:
6.5
Details on soil characteristics:
The purpose of the study was to compare in silico-based model predictions with laboratory derived data from bioaccumulation studies on earthworms (Eisenia andrei) for two organic chemicals; the test substance for this dossier, 2,2',6,6'-tetra-tert-butyl-4,4'-methylenediphenol (CAS 118-82-1) [known as Binox] and a xanthene dye 2', 4', 5', 7'-tetrabromo-4,5,6,7-tetrachloro-3', 6'-dihydroxy-, disodium salt [Phloxine B]. Only the details and results of the test substance CAS 118-82-1 are relevant to this dossier and reported here.

The bioaccumulation test design followed OECD Guideline 317 for assessing bioaccumulation in terrestrial oligochaetes. The test consisted of two phases; an uptake phase whereby earthworms were exposed to a concentration in the soil lower than the 25% inhibiting concentration and an elimination phase where earthworms were transferred to uncontaminated reference soil.

Two soils were used:
- Field-collected clay loam soil comprising 10% clay, 46% silt, 44% sand and 5.4% organic carbon with pH 5.6.
- Sandy soil comprising 2% clay, 4% silt, 94% sand and 0.36% organic carbon with pH 6.5.

Design details for the clay loam soil:
Nominal concentration = 50 mg/kg dry soil
Duration of each phase = 28 days
Number of organisms per replicate = 5
Soil mass per organism = 50 g dry soil
Sampling frequency (test day for each phase) = 0, 1, 2, 3, 6, 8, 12, 15, 19, 22, 26 and 28.

Design details for the sandy soil:
Nominal concentration = 10 mg/kg dry soil
Duration of each phase = 21 days
Number of organisms per replicate = 3
Soil mass per organism = 67 g dry soil
Sampling frequency (test day for each phase) = 0, 1, 2, 3, 7, 14 and 21.

Test vessels = 250 mL glass jars with perforated lids.
Weighed = weekly to maintain soil moisture conditions.
Soil No.:
#1
Duration:
28 d
Soil No.:
#2
Duration:
21 d
Soil No.:
#1
Initial conc.:
50 mg/kg soil d.w.
Based on:
test mat.
Soil No.:
#2
Initial conc.:
10 mg/kg soil d.w.
Based on:
test mat.
Parameter followed for biodegradation estimation:
test mat. analysis
Details on experimental conditions:
The purpose of the study was to compare in silico-based model predictions with laboratory derived data from bioaccumulation studies on earthworms (Eisenia andrei) for two organic chemicals; the test substance for this dossier, 2,2',6,6'-tetra-tert-butyl-4,4'-methylenediphenol (CAS 118-82-1) [known as Binox] and a xanthene dye 2', 4', 5', 7'-tetrabromo-4,5,6,7-tetrachloro-3', 6'-dihydroxy-, disodium salt [Phloxine B]. Only the details and results of the test substance CAS 118-82-1 are relevant to this dossier and reported here.

The bioaccumulation test design followed OECD Guideline 317 for assessing bioaccumulation in terrestrial oligochaetes. The test consisted of two phases; an uptake phase whereby earthworms were exposed to a concentration in the soil lower than the 25% inhibiting concentration and an elimination phase where earthworms were transferred to uncontaminated reference soil.

Two soils were used:
- Field-collected clay loam soil comprising 10% clay, 46% silt, 44% sand and 5.4% organic carbon with pH 5.6.
- Sandy soil comprising 2% clay, 4% silt, 94% sand and 0.36% organic carbon with pH 6.5.

Design details for the clay loam soil:
Nominal concentration = 50 mg/kg dry soil
Duration of each phase = 28 days
Number of organisms per replicate = 5
Soil mass per organism = 50 g dry soil
Sampling frequency (test day for each phase) = 0, 1, 2, 3, 6, 8, 12, 15, 19, 22, 26 and 28.

Design details for the sandy soil:
Nominal concentration = 10 mg/kg dry soil
Duration of each phase = 21 days
Number of organisms per replicate = 3
Soil mass per organism = 67 g dry soil
Sampling frequency (test day for each phase) = 0, 1, 2, 3, 7, 14 and 21.

Test vessels = 250 mL glass jars with perforated lids.
Weighed = weekly to maintain soil moisture conditions.
Soil No.:
#1
DT50:
46 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Information on temperature was not reported
Soil No.:
#2
DT50:
11 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Information on temperature was not reported
Transformation products:
not specified
Details on transformation products:
No data
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
not specified
Details on results:
No significant loss of the test substance was measured from the clay loam soil (soil #1). A significant loss of the test substance was observed from teh sandy soil (soil #2).
Results with reference substance:
No data
Conclusions:
The half-life of the test substance was reported for two soils - clay loam and a sandy soil. The half-lives in each soil were 46 and 11 days, respectively. The results indicate loss of the test substance is more rapid from sandy soils than clay loam soils.
Executive summary:

A bioaccumulation study of the uptake and elimination of the test substance in earthworms was reported by Princz et al (2014). In addition, the half-life of the test substance was recorded in the two different test soils. The half-lives were 46 and 11 days in the clay loam and sandy soils, respectively.

Description of key information

Two published studies are available which relate to laboratory studies undertaken on behalf of the Canadian Chemicals Management Plan testing programme. Princz et al (2014) is primarily a bioaccumulation study and reports half lives for the test substance in sandy and clay loam soils of 11 and 46 days, respectively. In soil toxicity studies by Ritchie et al (2013) it was concluded that the test substance was persistent with an average recovery of 77% at test end.

Key value for chemical safety assessment

Half-life in soil:
46 d
at the temperature of:
20 °C

Additional information

Two published studies are available which relate to laboratory studies undertaken on behalf of the Canadian Chemicals Management Plan testing programme. The key study is by Princz et al (2014) and is primarily an environmental fate study with a focus on bioaccumulation. The authors report half lives for the test substance in sandy and clay loam soils of 11 and 46 days, respectively. In order to be precautionary, the longest half life is taken to represent potential persistence across a range of natural soils in this risk assessment. A half life of 46 days (or less) does not meet or exceed the persistence criterion of 120 days or more and the test substance is not classified for persistence in soil.

The supporting study by Ritchie et al (2013) reported the results from a series of soil toxicity tests with earthworm, Collembola and terrestrial plants. The test durations varied depending on the organism being tested with the longest duration being 63 days.

In soil toxicity studies by Ritchie et al (2013) it was concluded that the test substance was persistent with an average recovery of 77% at test end.