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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
1977-11-30
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Ready biodegradation in the MITI-I test; reported in a database of the Japanese authority. Read-across justification: The substance is hydrolytically unstable. When it comes in contact with water or moisture complete hydrolysis will take place with no significant reaction products other than the particular alcohol and hydrated titanium dioxide. This rapid hydrolysis (hydrolysis half-life < 3 minutes to < 2 hours) is the driving force for the fate and pathways of the substance. The aquatic toxicity testing is considered scientifically unjustified as the substance degrades immediately releasing alcohol and hydrated insoluble titanium dioxides in water. The testing conducted with analogue substances of the category proves that the aquatic toxicity in daphnia and algae studies is similar to the aquatic toxicity of alcohol released to the test water, and the insoluble hydrated titanium oxides precipitated on the bottom of the test vessels. The identification of degradation products from the hydrolysis study conducted for the target substance verifies that there are no impurities in the alcohol released from the target substance, which might change the aquatic toxicity of the target substance compared to the toxicity of the pure alcohol. As there is a mechanistic reasoning to the read-across, the read-across from the degradation product (relevant alcohol) is used to evaluate the aquatic toxicity and the fate and pathways of the target substance in the environment.
Justification for type of information:
The substance is hydrolytically unstable. When it comes in contact with water or moisture, a complete hydrolysis will take place with no significant reaction products other than the particular alcohol and hydrated titanium dioxide. This rapid hydrolysis (hydrolysis half-life < 3 minutes to < 2 hours) is the driving force for the fate and pathways of the substance. The aquatic toxicity testing is considered scientifically unjustified as the substance degrades immediately releasing the particular alcohol and hydrated insoluble titanium dioxides in water.
The testing conducted with analogue substance of the category justifies that the aquatic toxicity in daphnia and algae studies is similar to the aquatic toxicity of the alcohol released to test water as the insoluble hydrated titanium oxide, precipitated on the bottom of the test vessels; lacking bioavailability. The identification of the degradation products from the hydrolysis study conducted for the target substance verifies that there are no impurities in the alcohol released from the target substance which might change the aquatic toxicity of the target substance compared to the toxicity of the pure alcohol.
As there is a mechanistic reasoning to the read-across, the read-across from the degradation product (relevant alcohol) is used to evaluate the aquatic toxicity and the fate and pathways of the target substance in the environment.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Concentration of sludge: 30 mg/l
Duration of test (contact time):
2 wk
Initial conc.:
100 mg/L
Based on:
not specified
Parameter followed for biodegradation estimation:
O2 consumption
Parameter followed for biodegradation estimation:
TOC removal
Parameter followed for biodegradation estimation:
test mat. analysis
Remarks:
GC
Parameter:
% degradation (O2 consumption)
Value:
> 79 - < 99.9
Sampling time:
2 wk
Parameter:
% degradation (TOC removal)
Value:
100
Sampling time:
2 wk
Parameter:
% degradation (test mat. analysis)
Value:
100
Sampling time:
2 wk

Read-across justifications and data matrices are presented in IUCLID section 13.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Data contained in Japanese authority's database indicate that 2-ethylhexanol was readily biodegradable in the MITI-I test (OECD TG 301 C), as evidenced by complete removal of TOC (100%) and test substance (100%, measured using GC) within 2 weeks. The BOD was reportedly 99.9 and 79.0 % in these studies. The starting chemical concentration was 100 ppm, concentration of activated sludge was 30 ppm (NITE, 2002).
Executive summary:

As the target substance is hydrolytically unstable, biodegradability of the known degradation products (2 -EH and TiO2) are used to evaluate the degradation. Based on the information on aquatic toxicity and biodegradation of the decomposition products (i.e. 2 -ethylhexanol as TiO2 is inroganic), and the rapid hydrolysis of the target substance, the abiotic degradation can be used to demonstrate fast degradation of the target substance for the purposes of C&L. This study is reliable, as it is conducted according to the guideline, to be used in weight of evidence approach to evaluate the biodegradability of the main decomposition product of the target substance.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Data obtained from an authoritative secondary source. Read-across justification: The substance is hydrolytically unstable. When it comes in contact with water or moisture complete hydrolysis will take place with no significant reaction products other than the particular alcohol and hydrated titanium dioxide. This rapid hydrolysis (hydrolysis half-life < 3 minutes to < 2 hours) is the driving force for the fate and pathways of the substance. The aquatic toxicity testing is considered scientifically unjustified as the substance degrades immediately releasing alcohol and hydrated insoluble titanium dioxides in water. The testing conducted with analogue substances of the category proves that the aquatic toxicity in daphnia and algae studies is similar to the aquatic toxicity of alcohol released to the test water, and the insoluble hydrated titanium oxides precipitated on the bottom of the test vessels. The identification of degradation products from the hydrolysis study conducted for the target substance verifies that there are no impurities in the alcohol released from the target substance, which might change the aquatic toxicity of the target substance compared to the toxicity of the pure alcohol. As there is a mechanistic reasoning to the read-across, the read-across from the degradation product (relevant alcohol) is used to evaluate the aquatic toxicity and the fate and pathways of the target substance in the environment.
Justification for type of information:
The substance is hydrolytically unstable. When it comes in contact with water or moisture, a complete hydrolysis will take place with no significant reaction products other than the particular alcohol and hydrated titanium dioxide. This rapid hydrolysis (hydrolysis half-life < 3 minutes to < 2 hours) is the driving force for the fate and pathways of the substance. The aquatic toxicity testing is considered scientifically unjustified as the substance degrades immediately releasing the particular alcohol and hydrated insoluble titanium dioxides in water.
The testing conducted with analogue substance of the category justifies that the aquatic toxicity in daphnia and algae studies is similar to the aquatic toxicity of the alcohol released to test water as the insoluble hydrated titanium oxide, precipitated on the bottom of the test vessels; lacking bioavailability. The identification of the degradation products from the hydrolysis study conducted for the target substance verifies that there are no impurities in the alcohol released from the target substance which might change the aquatic toxicity of the target substance compared to the toxicity of the pure alcohol.
As there is a mechanistic reasoning to the read-across, the read-across from the degradation product (relevant alcohol) is used to evaluate the aquatic toxicity and the fate and pathways of the target substance in the environment.
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
EU Method C.5 (Degradation: Biochemical Oxygen Demand)
Version / remarks:
APHA Standard Methods BOD (Standard Methods for the Examination of Water and Wastewater. 1971. 13th Ed. American Public Health Association, New York, NY).20 day BOD (Biochemical Oxygen Demand) test.
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
other: settled domestic waste water
Duration of test (contact time):
20 d
Initial conc.:
3 mg/L
Based on:
test mat.
Initial conc.:
7 mg/L
Based on:
test mat.
Initial conc.:
10 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Freshwater degradation
- Culturing apparatus: BOD bottle (The bottles were half filled with aerated dilution water containing the specified minerals and buffer).
- Number of culture flasks/concentration: two (Small aliquots of the test chemicals were added to these bottles from 0.1% stock solutions yielding concentrations of 3, 7 and 10 mg/L).
- Method used to create aerobic conditions: When the dissolved oxygen (DO) in the test bottle dropped below 4.0 mg/L, the contents were re­aerated. A clean, empty BOD bottle and the test bottle were connected with the adapter; by allowing about half of the liquid to pass into the new bottle, followed by moderate shaking, tho DO level could be returned to about 7 mg/L. Once this reaeration was accomplished, all of the liquid was returned to the original bottle,and a new DO value was determined and recorded. Insertion of the DO probe displaced some water from the test bottle, and one or two marbles weredropped into the bottle to fill this void.
- Test Method: The test was performed as per Standard methods for the Examination of water and wastewater, 1971 (as cited in Price et al, 1974)

Seawater biodegradation
Substance demonstrated to be biodegraded greater than 50% in 20 days in the freshwater screening tests it was subjected to biodegradation tests insynthetic seawater (refer Table in attached background material). The nutrient salts and buffers for BOD dilution water recommended in "Standard Methods" (as cited in Price et al, 1974) were added to the artificial seawater prior to use in biodegradation tests. With the exception of the seed source, the "seawater" bio­degradation tests were performed in the same manner as were the freshwater tests.
However, an oxygen meter that permitted correction for high salinity water was used for DO determinations where instrumental analysis was performed. The seed used in the seawater biodegradation tests was developed in seawater taken from Lavaca Bay, Texas. This seed source was maintained by adding small amounts of settled raw wastewater about every 3 to 4 days as a source of substrate, seed bacteria and growth factors. Evaporative losses were replaced with distilled water.

Reference substance:
not specified
Parameter:
% degradation (O2 consumption)
Value:
78
Sampling time:
15 d
Remarks on result:
other: Freshwater
Parameter:
% degradation (O2 consumption)
Value:
86
Sampling time:
20 d
Remarks on result:
other: Freshwater
Parameter:
% degradation (O2 consumption)
Value:
84
Sampling time:
15 d
Remarks on result:
other: Synthetic salt water
Parameter:
% degradation (O2 consumption)
Value:
100
Sampling time:
20 d
Remarks on result:
other: Synthetic salt water
Details on results:
Theoretical oxygen demand (mg/mg); 2.95 and measured COD; 2.79 mg/mg. Equations for the interpratation of the results is presented in section any other information on results including tables.

Results of the biodegradation tests were expressed in terms of percent bio-oxidation, defined below.

percent bio-oxidisesd = 100 (O's- Ob)/ Cx. ThOD

where

O's= cumulative oxygen uptake for the oxidation of the carbonaceous material in the test sample bottle from day zero to the day of interest, mg/L.

Ob=cumulative oxygen uptake in a blank, containing the same amount and type of microbial seed as the test sample bottle, from day zero to the day of interest, mg/L.

Cx.= initial concentration of compound being tested, mg/L.

ThOD = theoretical oxygen demand or the weight ratio of oxygen required per milligram of compound for complete conversion of the compound to carbon dioxide and water.

Interpretation of results:
readily biodegradable
Conclusions:
Based on the literature, 20-d biodegradation-% of 2-ethylhexanol using settled domestic wastewater was 86 % and 100 % at nominal test concentrations of 3, 7 and 10 mg/l . Testing was conducted in both freswater and synthetic seawater.
Executive summary:

As the target substance is hydrolytically unstable, biodegradability of the known degradation products (2 -EH and TiO2) are used to evaluate the degradation. Based on the information on aquatic toxicity and biodegradation of the decomposition products (i.e. 2 -ethylhexanol as TiO2 is inroganic), and the rapid hydrolysis of the target substance, the abiotic degradation can be used to demonstrate fast degradation of the target substance for the purposes of C&L. This study is reliable to be used in weight of evidence approach to evaluate the biodegradability of the main decomposition product of the target substance.

Endpoint:
biodegradation in water: ready biodegradability
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:

Description of key information

Testing is not scientifically justified as substance is hydrolytically unstable. Based on the rapid hydrolysis,

and the ready biodegradability and low aquatic toxicity of the known decomposition products, this substance can

be considered as readily degradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Testing of biodegradability of tetrakis(2 -ethylhexane-1,3 -diolato)titanium is not scientifically justified as it is hydrolytically unstable. When this substance comes in contact with water or moisture, a complete hydrolysis will take place with no significant reaction products other than 2 EHD) and hydrated titanium dioxides (half-life < 10 minutes, Brekelmans 2013). In addition, biodegradability testing is not necessary as all the decomposition products have been identified. The structurally similair degradation product (2 -EH) is readily biodegradable (> 79 % to 100 % in 14-d MITI-I test (OECD TG 301 C) at 100 ppm test concentration (NITE 2002), and > 86 -% in 20-d biooxidation test in freshwater and synthetic seawater; Price et al. 1974). The other environmentally non-hazardous degradation product (TiO2) is inorganic and insoluble and therefore not relevant for this endpoint. Based on the information on aquatic toxicity and biodegradation of the decomposition products, and the rapid hydrolysis of the target substance, the abiotic degradation can be used to demonstrate fast degradation of this substance for the purposes of C&L.