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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
other: published data
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Justification for type of information:
The S-allyl O-pentyl dithiocarbonate (CAS No. 2956-12-9, the subject of this dossier) is expected to exhibit very similar toxicity to Potassium isobutyl xanthate (CAS No.13001-46-2), which is also xanthate compound. Comparable metabolism would occur.
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
The inoculum used was activated sludge from a semi-continuous colony maintained in the laboratory.
Incubation was carried out at 25°C in 200 ml Erlenmeyer flasks containing 5 ul of a alcohol and 100 ml of culture medium.
Biodegradation rate constant was determined by measurement ofthe alcohol concentration in the supernatant of the culture
by gas chromatography.
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
test mat.
Reference substance:
not specified
Parameter:
% degradation (CO2 evolution)
Value:
98
Sampling time:
12 d
Parameter:
% degradation (CO2 evolution)
Value:
30
Sampling time:
3 h
Parameter:
% degradation (CO2 evolution)
Value:
75
Sampling time:
5 d
Details on results:
The IUCLID datasheet describes an aerobic biodegradation test for potassium isobutyl xanthate following the OECD Guide-line 302B “Inherent biodegradability: Modified Zahn-Wellens Test”. The results showed degradation of 98% after 12 days, with approximately 30% after 3 h and 75% after 5 days.
These results suggest that potassium isobutyl xanthate will be inherently biodegradable and it is not expected to persist in the environment.
Validity criteria fulfilled:
not specified
Interpretation of results:
inherently biodegradable
Conclusions:
- The S-allyl O-pentyl dithiocarbonate (CAS No. 2956-12-9, the subject of this dossier) is expected to exhibit very similar toxicity to Potassium isobutyl xanthate (CAS No.13001-46-2), which is also xanthate compound. Comparable metabolism would occur. The IUCLID datasheet describes an aerobic biodegradation test for potassium isobutyl xanthate following the OECD Guide-line 302B “Inherent biodegradability: Modified Zahn-Wellens Test”. The results showed degradation of 98% after 12 days, with approximately 30% after 3 h and 75% after 5 days. These results suggest that potassium isobutyl xanthate will be inherently biodegradable and it is not expected to persist in the environment.
Executive summary:

- The S-allyl O-pentyl dithiocarbonate   (CAS No. 2956-12-9, the subject of this dossier) is expected to exhibit very similar toxicity to Potassium isobutyl xanthate (CAS No.13001-46-2), which is also xanthate compound. Comparable metabolism would occur. The IUCLID datasheet describes an aerobic biodegradation test for potassium isobutyl xanthate following the OECD Guide-line 302B “Inherent biodegradability: Modified Zahn-Wellens Test”. The results showed degradation of 98% after 12 days, with approximately 30% after 3 h and 75% after 5 days. These results suggest that potassium isobutyl xanthate will be inherently biodegradable and it is not expected to persist in the environment.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
other: published data
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
Pentan-1-ol/Amyl alcohol is both reagents used in the manufacture of S-allyl O-pentyl dithiocarbonate. Therefore, pentan-1-ol/Amyl alcohol need to be considered in the assessment of S-allyl O-pentyl dithiocarbonate.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Principles of method if other than guideline:
Standard methodology, which is similar to OECD Guideline 301D . These tests measured consumption of oxygen (biochemical oxygen demand, BOD) in vessels containing test substance, non-adapted inoculum from domestic sewage treatment plants, and test media prepared according to APHA guidelines.
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):sewage, domestic, non-adapted
Microbial cultures were grown in medium in 1L or 2 L flasks maintained on a rotary shaker at 25 degree C for 48 hr.
Cells were collected by centrifuge, washed in 0.10M phosphate buffer (pH 7.1), and resuspended in the same buffer.
Warburg flasks contained 1.0 ml of sewage cell suspension, 100 umoles of phosphate buffer (pH 7.1) and 3.0 umoles of substrate. Additional tests with glucose were conducted to assess toxicity of test substance to the inoculum.
Oxygen uptake was measured at 30 degree C.
Duration of test (contact time):
ca. 30 d
Initial conc.:
ca. 2.9 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
other: glucose, 2 mg/l
Parameter:
% degradation (O2 consumption)
Value:
ca. 34
Sampling time:
2 d
Parameter:
% degradation (O2 consumption)
Value:
ca. 52
Sampling time:
5 d
Parameter:
% degradation (O2 consumption)
Value:
ca. 62
Sampling time:
10 d
Parameter:
% degradation (O2 consumption)
Value:
ca. 52
Sampling time:
30 d
Details on results:
A 30-day aerobic test with 1-pentyl alcohol and reported 34% biooxidation by day 2, 52% by day 5, 62% by day 10, and 52% by day 30.
Parameter:
BOD5
Value:
4.1 mg O2/g test mat.
Results with reference substance:
The concentration of oxygen consumed in suspensions exposed to 1-pentyl alcohol was 2.7 mg/l, 4.1 mg/l, 4.9 mg/l, and 4.1 mg/l for days 2, 5, 10, and 30, respectively.

The concentration of oxygen consumed in suspensions exposed to 1-pentyl alcohol was 2.7 mg/l, 4.1 mg/l, 4.9 mg/l, and 4.1 mg/l for days 2, 5, 10, and 30, respectively

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Since the degradation exceeded 62% within 10 days, the substance meets the criteria for classification as readily biodegradable.
The biodegradation of 1-pentyl alcohol (Amyl alcohol) was >62 % after 10 days of exposure, therefore 1-pentyl alcohol (Amyl alcohol) is readily biodegradable.
Pentan-1-ol/Amyl alcohol is both reagents used in the manufacture of S-allyl O-pentyl dithiocarbonate. Therefore, pentan-1-ol/Amyl alcohol need to be considered in the assessment of S-allyl O-pentyl dithiocarbonate


Executive summary:

In this study, Dias and Alexander (1971) conducted a 30-day aerobic test with 1-pentyl alcohol and reported 34% biooxidation by day 2, 52% by day 5, 62% by day 10, and 52% by day 30. In the same study, the authors measured the biooxidation of 2-methyl butyl alcohol, which was measured at 48, 62, 74, and 52% after 2, 5, 10, and 30 days, respectively. Values for both alcohols were corrected for oxygen consumption in bottles with no test substance present, which accounted for the lower rate on day 30.

Results synopsis

BOD2=34%,

BOD5=52%,

BOD10=62%

BOD30=52%

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
other: published data
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
Carbon disulphide is reagent used in the manufacture of S-allyl O-pentyl dithiocarbonate.Therefore, the Biodegradation in water of Carbon disulphide need to be considered in the assessment of S-allyl O-pentyl dithiocarbonate.
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
activated sludge was used as an inoculum
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end the sludge (200 mgdry weight) was aerated for one week. The sludge was diluted to a concentration of 2 mg dry weight/l in the bottles.
Duration of test (contact time):
28 d
Initial conc.:
ca. 5 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
study was conducted according to OECD no 301 D guideline with a slight modification, described under details of inoculum
Reference substance:
acetic acid, sodium salt
Parameter:
% degradation (DOC removal)
Value:
> 80
Sampling time:
1 wk

This study shows that CS2 is readily biodegradable.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The biodegradation of CS2 was >80 % after 28 days of exposure, therefore CS2 is readily biodegradable.
Carbon disulphide is reagent used in the manufacture of S-allyl O-pentyl dithiocarbonate.Therefore, the Biodegradation in water of Carbon disulphide need to be considered in the assessment of S-allyl O-pentyl dithiocarbonate.
These results suggest that S-allyl O-pentyl dithiocarbonate will be readily biodegradable and it is not expected to persist in the environment.
Executive summary:

The biodegradation of CS2 was >80 % after 28 days of exposure, therefore CS2 is readily biodegradable.

Carbon disulphide is reagent used in the manufacture of S-allyl O-pentyl dithiocarbonate.Therefore, the Biodegradation in water of Carbon disulphide need to be considered in the assessment of S-allyl O-pentyl dithiocarbonate.

These results suggest that  S-allyl O-pentyl dithiocarbonate will be readily biodegradable and it is not expected to persist in the environment.

Endpoint:
biodegradation in water: ready biodegradability
Data waiving:
other justification
Justification for data waiving:
other:
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
The study was conducted according to ISO Guideline 7827 for several alkyl xanthates, including the S-allyl O-pentyl dithiocarbonate.
Qualifier:
according to
Guideline:
ISO 7827 (Evaluation in an Aqueous Medium of the "Ultimate" Aerobic Biodegradability of Organic Compounds - Method by Analysis of Dissolved Organic Carbon (DOC))
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Principles of method if other than guideline:
Biodegradation of alkyl xanthates was determined by measuring the biodegradability and biodegradation kinetics. The impact of the alkyl structure on the degradability was assessed. UV-spectrometry was applied for identifying the degradation products, and main reaction mechanisms are proposed. The study was conducted in accordance with ISO Standard 7827-1984 (equivalent to OECD 301A, DOC Die-away test),
GLP compliance:
not specified
Remarks:
No statement on the GLP compliance is made
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
The cationic part (and thus the exact chemical identity) of the xanthates studied were not specified in the publication. However, due to immediate dissociation of any alkali salts in an aqueous solution, the behaviour of the anionic part is identical with S-allyl O-pentyl dithiocarbonate
Oxygen conditions:
anaerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Inoculum/activated sludge: activated sludge from sewage treatment plant (type not pecified)
- It was first filtered trough a screen to remove large particles, then removed into a jar and aerated for 4 h
- Initial cell/biomass concentration: about 4.0 - 8.5 E7 CFU/ml by light microscopic evaluation
- the sludge was concentrated to 15 g/L solids
- Preparation of inoculum for exposure: according to ISO 7827 (1984)
- Pretreatment: the cultures (0.5 L) were prepared in 1L shaking flasks
- Test solution: aqueous medium, pH 7.4, containing 3.0 g/L NH4Cl, 1.0 g/L KHPO3, 0.25 g/L MgSO4, 0.25 g/L KCl, 0.002 g/L FeSO4, 0.3 g/L yeast extract
- the test compounds were added to the culture medium to give a concentration of 30 mg/L
- each test medium (0.5L) was inoculated with 5 mL of activated sludge (containing 15 g/L suspended solids), placed on a shaking table (25 oC, dark, 130 rpm, 72 h)
- 5 mL of the liquor was transferred into another shaking flask and acclimatized for 72 h
- a 5 mL aliquot was transferred into another shaking flask containing 0.5L of medium to degrade alkyl xanthates
Duration of test (contact time):
8 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
The following results were observed:
1) Biodegradability of alkyl xanthates
2) Biodegradation kinetics
3) Relationship between structure and biodegradability
4) Biodegradation mechanism
Reference substance:
not specified
Test performance:
The test period was only 8 days, during which 3 out of 5 xanthates tested reached the 70 % biodegradation pass level.
Biodegradation kinetic calculations further support the reliability of the results.
No details on the statistics, reference substances or validation criteria are reported.
Parameter:
% degradation (DOC removal)
Value:
41.1
Sampling time:
2 d
Remarks on result:
other: n-amyl xanthate
Parameter:
% degradation (DOC removal)
Value:
42.8
Sampling time:
4 d
Remarks on result:
other: n-amyl xanthate
Parameter:
% degradation (DOC removal)
Value:
55.7
Sampling time:
6 d
Remarks on result:
other: n-amyl xanthate
Parameter:
% degradation (DOC removal)
Value:
73.74
Sampling time:
8 d
Remarks on result:
other: n-amyl xanthate
Details on results:
Based on the results, S-allyl O-pentyl dithiocarbonate is readily biodegradable: 73.74 % was degraded in 8 days (at initial pH 7.4 and 25 oC). The calculated half-life (t1/2) was 4.6 d. Xanthates with branched alkyl chains can be expected to have slightly lower rate of biodegradation. The results show the rapid biodegradability of the initial substance, but suggest that the main degradation products which cannot be further mineralised by microbes are carbon disulfide, monothiocarbonate and dixanthogen, which accumulated in the test solution. Despite of that, no significant toxic or inhibitory effects on micro-organisms were observed at an initial test concentration of 30 mg/L.

The biodegradation extent of several alkyl xanthate collectors has been determined according to ISO 7827 and the kinetic model of biodegradation has been discussed. Meanwhile, the impact of molecular structure on biodegradability has been studied. The results indicated that the biodegradation extent of ethyl xanthate, n-butyl xanthate, n-amyl xanthate, isopropyl xanthate and iso-butyl xanthate can attain 96.36%, 81.76%, 73.74%, 63.37% and 60.30%, respectively in 8d. The rate constants (k) follows the order of: kethyl>kn-butyl>kn-amyl>kisopropyl>kisobutyl. And their aerobic biodegradation follows the first order reaction kinetics equation. The biodegradation of the xanthates decreases with the DT-90 and half-life time increase with an increase in the length of hydrocarbon chain and number of alkyl lateral chains. Comparing to the hydrocarbon chain length, the branched structure has a more significant effect on the degradability of alkyl xanthates. Through the preliminary study of the biodegradation mechanism of xanthates, it was found that CS2 and monothiocarbonate are the main products of biodegradation of xanthates and a small amount of oil-like dixanthogen droplets are also produced.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Based on the results, S-allyl O-pentyl dithiocarbonate is readily biodegradable: 73.74 % was degraded in 8 days (at initial pH 7.4 and 25 oC). The calculated half-life (t1/2) was 4.6 d. Xanthates with branched alkyl chains can be expected to have slightly lower rate of biodegradation. The results show the rapid biodegradability of the initial substance, but suggest that the main degradation products which cannot be further mineralised by microbes are carbon disulfide, monothiocarbonate and dixanthogen, which accumulated in the test solution. Despite of that, no significant toxic or inhibitory effects on micro-organisms were observed at an initial test concentration of 30 mg/L.
Executive summary:

The biodegradation extent of several alkyl xanthate collectors has been determined according to ISO 7827 and the kinetic model of biodegradation has been discussed. Meanwhile, the impact of molecular structure on biodegradability has been studied. The results indicated that the biodegradation extent of ethyl xanthate, n-butyl xanthate, n-amyl xanthate, isopropyl xanthate and iso-butyl xanthate can attain 96.36%, 81.76%, 73.74%, 63.37% and 60.30%, respectively in 8d. The rate constants (k) follows the order of: kethyl>kn-butyl>kn-amyl>kisopropyl>kisobutyl. And their aerobic biodegradation follows the first order reaction kinetics equation. The biodegradation of the xanthates decreases with the DT-90 and half-life time increase with an increase in the length of hydrocarbon chain and number of alkyl lateral chains. Comparing to the hydrocarbon chain length, the branched structure has a more significant effect on the degradability of alkyl xanthates. Through the preliminary study of the biodegradation mechanism of xanthates, it was found that CS2 and monothiocarbonate are the main products of biodegradation of xanthates and a small amount of oil-like dixanthogen droplets are also produced.

 

Description of key information

Based on the results, S-allyl O-pentyl dithiocarbonate is readily biodegradable: 73.74 % was degraded in 8 days (at initial pH 7.4 and 25 oC). The calculated half-life (t1/2) was 4.6 d. Xanthates with branched alkyl chains can be expected to have slightly lower rate of biodegradation. The results show the rapid biodegradability of the initial substance, but suggest that the main degradation products which cannot be further mineralised by microbes are carbon disulfide, monothiocarbonate and dixanthogen, which accumulated in the test solution. Despite of that, no significant toxic or inhibitory effects on micro-organisms were observed at an initial test concentration of 30 mg/L.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

According to “ANNEX IX- STANDARD INFORMATION REQUIREMENTS FOR SUBSTANCES MANUFACTURED OR IMPORTED IN QUANTITIES OF 100 TONNES OR MORE”, a simulation testing on ultimate degradation in surface water, the study does not need to be performed if the substance is ready biodegradable. Pentan-1-ol/Amyl alcohol, Carbon disulphide and Allyl Chloride are both reagents used in the manufacture of S-allyl O-pentyl dithiocarbonate.Therefore, the Biodegradation in water of Pentan-1-ol/Amyl alcohol, Carbon disulphide and Allyl Chloride need to be considered in the assessment of S-allyl O-pentyl dithiocarbonate. The results suggest that Pentan-1-ol/Amyl alcohol, Carbon disulphide and Allyl Chloride are readily biodegradable and S-allyl O-pentyl dithiocarbonate will be readily biodegradable and it is not expected to persist in the environment. As S-allyl O-pentyl dithiocarbonate is ready biodegradable a ready biodegradability study does not need to be conducted. Therefore testing for Biodegradation in water screening tests does not need to be performed.