Registration Dossier
Registration Dossier
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EC number: 259-869-1 | CAS number: 55860-53-2
Endpoint summary
Administrative data
Description of key information
Additional information
Environmental fate and pathways
Environmental Fate/Exposure Summary:
Environmental exposure
O-isobutyl ethylthiocarbamate (IBETC) is used in the mining industry as flotation agents as a fine collector for minerals such as copper sulfate, lead, zinc, molybdenum and nickel. O-isobutyl ethylthiocarbamate (IBETC) is the best collector for copper sulfate. The amount of O-isobutyl ethylthiocarbamate (IBETC) used is very small relative to the quantity of ore treated, being approximately 2 to 50 g/tonne of ore.
The flotation process is fully automated. The process takes place in open tanks. However, the concentration of O-isobutyl ethylthiocarbamate (IBETC) in the flotation tank is low and, therefore, the release of Carbon monoxide; carbon dioxide; oxides of nitrogen; oxides of sulphur (includes sulphur di and tri oxides) would be expected to be low.
Air monitoring data, although limited and of poor quality, indicate that the atmospheric levels of carbon dioxide; oxides are below 10 ppm in the flotation areas. The risk to workers during the flotation process is considered to be low.
2.18 (BCF = 151 L/kg wet-wt)
Environmental fate
O-isobutyl ethylthiocarbamate (IBETC) was hydrolytically stable (half life > 1 year) specified by the OECD Guidelines. This substance has a limited potential to bioaccumulate (based on log Kow used by BCF estimates: 3.81, and predicted bioconcentration factors, log BCF = 2.18 (EPIWIN/BCF Program). O-isobutyl ethylthiocarbamate (IBETC) is not expected to contaminate the environment where ore tailings are confined to well constructed tailings dams. Most will be retained on sulphide minerals and destroyed when they are dried after flotation. Minor residues that remain associated with tailings will be destroyed by hydrolysis intailings dams.
Critical Health Effects
The critical health effects for risk characterisation include, a systemic acute effect (acute toxicity from oral exposure) and a local effect (skin irritation and eye irritation).
Public Risk Characterisation
Given that there are no consumer uses identified for the chemical, it is unlikely that the public will be exposed. Hence, the public risk from this chemical is not considered to be unreasonable.
Occupational Risk Characterisation
During product formulation, oral and dermal exposure might occur, particularly where manual or open processes are used. These could include transfer and blending activities, quality control analysis, and cleaning and maintaining equipment. Worker exposure to the chemical at lower concentrations could also occur while using formulated products containing the chemical. The level and route of exposure will vary depending on the method of application and work practices employed.
Given the critical systemic long-term, systemic acute and local health effects, the chemical could pose an unreasonable risk to workers unless adequate control measures to minimise oral and dermal exposure are implemented. The chemical should be appropriately classified and labelled to ensure that a person conducting a business or undertaking (PCBU) at a workplace (such as an employer) has adequate information to determine the appropriate controls.
Stability
Phototransformation in air
If released to air, a vapor pressure of 0.251 mm Hg at 25 deg C (0.251 mm Hg is equivalent to vapour pressure of 33.5 Pa ) indicates that O-isobutyl ethylthiocarbamate will exist solely as a vapor in the atmosphere. Vapor-phase O-isobutyl ethylthiocarbamate will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 0.224 days, calculated from its rate constant of 47.7336 E-12 cm3/molecule-sec at 25 deg.
O-isobutyl ethylthiocarbamate do not contain chromophores that absorb at wavelengths >290 nm and therefore O-isobutyl ethylthiocarbamate is not expected to be susceptible to direct photolysis by sunlight.
Using the AOPWIN QSAR model, the photochemical degradation rate of O-isobutyl ethylthiocarbamate in the atmosphere is 47.7336 E-12 cm3/molecule-sec, with a resultant predicted half live of 2.689 Hrs ( 0.224 Days (12-hr day; 1.5E6 OH/cm3))
OVERALL OH Rate Constant = 47.7336 E-12 cm3/molecule-sec
HALF-LIFE = 0.224 Days (12-hr day; 1.5E6 OH/cm3)
HALF-LIFE = 2.689 Hrs
Phototransformation in water
It is not applicable for a compound wich is slightly soluble or moderately soluble
Phototransformation in soil
If released to soil, O-isobutyl ethylthiocarbamate is expected to have high mobility based upon an estimated Koc of 144.4 . Volatilization from moist soil surfaces is not expected to be an important fate process.
Therefore testing for Phototransformation in soils does not need to be performed.
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water (H2O) are split into hydrogen cations (H+, conventionally referred to as protons) and hydroxide anions (OH−) in the process of a chemical mechanism).
The hydrolysis of the substance was less than 10% over the 5 days, so a definitive test was not performed. Based on these results, O-isobutyl ethylthiocarbamate was hydrolytically stable (half life > 1 year) specified by the OECD Guidelines .
Biodegradation
Biodegradation in water: screening tests
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. Isobutyl alcohol is reagents used in the manufacture of O-isobutyl ethylthiocarbamate.Therefore, the Biodegradation in water of Isobutyl alcohol need to be considered in the assessment of O-isobutyl ethylthiocarbamate .
The ready biodegradability of the substance was examined. After 28 days, approximately 74% of the test material was degraded.
The results suggest that Isobutyl alcohol is readily biodegradable and therefore O-isobutyl ethylthiocarbamate will be readily biodegradable and it is not expected to persist in the environment. As O-isobutyl ethylthiocarbamate 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.
Biodegradation in water and sediment: simulation tests
The study does not need to be conducted because direct and indirect exposure of sedimentis unlikely
Biodegradation in soil
If released to soil, O-isobutyl ethylthiocarbamate is expected to have very high mobility based upon an estimated Koc of 144.4. Volatilization from moist soil surfaces is not expected to be an important fate process. Therefore testing for biodegradation in soil does not need to be performed.
Bioaccumulation
This substance has a limited potential to bioaccumulate (based on log Kow used by BCF estimates: 3.81, and predicted bioconcentration factors, log BCF = 2.18 (EPIWIN/BCF Program).
The estimated BCF of 151.4 L/kg wet-wt was measured by calculation from EPI SuiteTM v4.1 Program.
These values would suggest very low bioaccumulation potential.
This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency).
BCFBAF Program (v3.01) Results:
==============================
SMILES : O(C(=NCC)S)CC(C)C
CHEM : Carbamothioic acid, ethyl-, o-(2-methylpropyl) ester
MOL FOR: C7 H15 N1 O1 S1
MOL WT : 161.26
--------------------------------- BCFBAF v3.01 --------------------------------
Summary Results:
Log BCF (regression-based estimate): 2.18 (BCF = 151 L/kg wet-wt)
Biotransformation Half-Life (days) : 0.649 (normalized to 10 g fish)
Log BAF (Arnot-Gobas upper trophic): 2.29 (BAF = 195 L/kg wet-wt)
Log Kow (experimental): not available from database
Log Kow used by BCF estimates: 3.81
Equation Used to Make BCF estimate:
Log BCF = 0.6598 log Kow - 0.333 + Correction
Correction(s): Value
No Applicable Correction Factors
Estimated Log BCF = 2.180 (BCF = 151.4 L/kg wet-wt)
Bioaccumulation: terrestrial
QSAR estimation using the BCFBAF v3.01 of the EPISUITE 4.1 indicate that the BCF of O-isobutyl ethylthiocarbamateis 151.4L/kgwwt. This is well below the threshold for Bioaccumulation (B) for the PBT determination.
Transport and distribution
Adsorption / desorption
The log of the adsorption coefficient (KOC) of O-isobutyl ethylthiocarbamate was estimated to be log KOC = 2.1595 which is equal to a KOC value of 144.4 using the KOCWIN v2.00 QSARmethod.
This value indicates that O-isobutyl ethylthiocarbamate will be adsorbed by organic carbon in soil. O-isobutyl ethylthiocarbamate can be classified to be of very high mobility in soil according these results and does not have a high potential for adsorption to soil. O-isobutyl ethylthiocarbamate adsorbs strongly to sulphide minerals but has less affinity for surfaces in general. The KOC value of 144.4 also suggest this conclusion.
The estimated Soil Adsorption Coefficient was 144.4 L/kg measured by calculation from EPI SuiteTM v4.1 Program. This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency
KOCWIN Program (v2.00) Results:
==============================
SMILES : O(C(=NCC)S)CC(C)C
CHEM : Carbamothioic acid, ethyl-, o-(2-methylpropyl) ester
MOL FOR: C7 H15 N1 O1 S1
MOL WT : 161.26
--------------------------- KOCWIN v2.00 Results ---------------------------
Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 4.664
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 3.0311
Fragment Correction(s):
1 Ether, aliphatic (-C-O-C-) .......... : -0.8716
Corrected Log Koc .................................. : 2.1595
Estimated Koc: 144.4 L/kg <===========
Koc Estimate from Log Kow:
-------------------------
Log Kow (Kowwin estimate) ......................... : 3.81
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 3.0325
Fragment Correction(s):
1 Ether, aliphatic (-C-O-C-) .......... : -0.0906
Corrected Log Koc .................................. : 2.9419
Estimated Koc: 874.8 L/kg <===========
Henry's Law constant
The estimated Henrys Law Constant (25 deg C) measured by calculation from EPI SuiteTM v4.1, HENRYWIN v3.20 Program was 1.412E-003 atm-m3/mole (1.431E+002 Pa-m3/mole) , which is almost zero.
This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency).
Distribution modelling.
O-isobutyl ethylthiocarbamate has no affinity to be in air and sediment. The direct emissions to soil and surface water are significant, therefore O-isobutyl ethylthiocarbamate will be almost exclusively be found in soil and surface water.
Mackay fugacity modelling (level 3) indicates that, taking into account degradation and using inflow parameters which are consistent with the known production tonnage of this substance in, fugacity coefficient indicates that environmental concentrations in water are predicted to be 6.93e-011 (atm), in air (atm) 1.13e-011and soil 5.48e-010 (atm) and sediment to be 5.83e-011 (atm).
These are negligible low levels. This can be considered a worse case prediction as it assumes all product is emitted with no emission control systems used.
Other distribution data
These results suggest O-isobutyl ethylthiocarbamate that direct and indirect exposure from distribution in media is unlikely.
Based on low vapor pressure and low estimated log Pow, expected to partition to water and soil. Not expected to partition to air, sediments or biota. Therefore testing for distribution in media does not need to be performed.
The estimated STP Fugacity Model and Volatilization From Water were measured by calculation from EPI SuiteTM v4.1 Program. This is Exposure Assessment Tools and Models made from EPA (Environmental Protection Agency) .
Volatilization From Water
=========================
Chemical Name: Carbamothioic acid, ethyl-, o-(2-methylpropyl) ester
Molecular Weight : 161.26 g/mole
Water Solubility : -----
Vapor Pressure : -----
Henry's Law Constant: 6.26E-006 atm-m3/mole (estimated by Bond SAR Method)
RIVER LAKE
--------- ---------
Water Depth (meters): 1 1
Wind Velocity (m/sec): 5 0.5
Current Velocity (m/sec): 1 0.05
HALF-LIFE (hours) : 120.1 1416
HALF-LIFE (days ) : 5.003 59.01
STP Fugacity Model: Predicted Fate in a Wastewater Treatment Facility
======================================================================
(using 10000 hr Bio P,A,S)
PROPERTIES OF: Carbamothioic acid, ethyl-, o-(2-methylpropyl) ester
-------------
Molecular weight (g/mol) 161.26
Aqueous solubility (mg/l) 0
Vapour pressure (Pa) 0
(atm) 0
(mm Hg) 0
Henry 's law constant (Atm-m3/mol) 6.26E-006
Air-water partition coefficient 0.000256015
Octanol-water partition coefficient (Kow) 6456.54
Log Kow 3.81
Biomass to water partition coefficient 1292.11
Temperature [deg C] 25
Biodeg rate constants (h^-1),half life in biomass (h) and in 2000 mg/L MLSS (h):
-Primary tank 0.00 7209.99 10000.00
-Aeration tank 0.00 7209.99 10000.00
-Settling tank 0.00 7209.99 10000.00
STP Overall Chemical Mass Balance:
---------------------------------
g/h mol/h percent
Influent 1.00E+001 6.2E-002 100.00
Primary sludge 1.25E+000 7.8E-003 12.50
Waste sludge 9.41E-001 5.8E-003 9.41
Primary volatilization 2.64E-003 1.6E-005 0.03
Settling volatilization 7.03E-003 4.4E-005 0.07
Aeration off gas 1.78E-002 1.1E-004 0.18
Primary biodegradation 5.00E-003 3.1E-005 0.05
Settling biodegradation 1.46E-003 9.1E-006 0.01
Aeration biodegradation 1.92E-002 1.2E-004 0.19
Final water effluent 7.76E+000 4.8E-002 77.56
Total removal 2.24E+000 1.4E-002 22.44
Total biodegradation 2.57E-002 1.6E-004 0.26
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