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Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
23 January, 2012 to 08 March, 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
other: HESI / ILSI (http://www.hesiglobal.org/i4a/pages/index.cfm?pageID=3463)
Qualifier:
according to guideline
Guideline:
other: OECD 319B : Determination of in vitro intrinsic clearance using rainbow trout liver S9 sub-cellular fraction (RT-S9)
Version / remarks:
June, 2018
Principles of method if other than guideline:
In order to characterize the hepatic metabolic profile of the test article, Rainbow trout liver S9 was used. Fish liver S9 fractions represent a model system which contains both Phase I and Phase II metabolizing enzymes. Significant disappearance in the presence of liver S9 fractions would indicate likely contributions from metabolic enzymes.

Although this approach does not constitute an internationally recognised and validated alternative method for extrapolating fish BCF values, it is firmly believed that it offers a solid grounding as a predictive screening approach. In mammalian systems, the primary site of metabolism for many xenobiotics is the liver, where biotransformation reactions are mainly catalyzed by the cytochrome P450 family of enzymes located in the endoplasmic reticulum and/or by non-CYP450 enzyme systems, such as sulfo- and glucuronosyltransferases. Similar to mammalian systems, it is believed that in fish the most relevant information about a chemical’s metabolic clearance in vivo can often be derived from in vitro studies using in vitro cellular/subcellular fractions. When other data such as fraction absorbed and plasma fraction bound are available, measuring the in vitro metabolic stability of a test article can provide an indication of the in vivo hepatic intrinsic clearance.
Generally, prediction of the metabolic stability for a given test article involves either measuring metabolite formation from the test article or disappearance of the test article in liver fractions (microsomes and S9 fractions) or hepatocytes. Liver S9 fractions were chosen due to the potential to provide rapid and cost-effective measurements of fish metabolic biotransformation potential. A pre-validation study utilizing in vitro metabolism data to utilize in the in vitro to in vivo extrapolation model has been undertaken by a consortium composed by industry, government and research centers under the coordination of HESI/ILSI. For example, measurement of the disappearance of a test chemical can provide an estimate of the metabolic half-life (reference 1 to 3, below). In vitro studies also can frequently serve as a screening mechanism to rule out the importance of a particular metabolic pathway. In vitro studies will aid in the incorporation of data into bioaccumulation and physiologically based toxicokinetics models (references 1 and 3, below). In addition, in vitro metabolic stability data from multiple species can aid in the evaluation of animal species for use in toxicological and pharmacokinetic studies.


1. Nichols, J., Schultz, I., and Fitzsimmons, P. The in vitro-in vivo extrapolation of qualitative hepatic biotransformation data for fish. I. A review of methods, and strategies for incorportating intrinsic clearance estimates into chemical kinetic models. Aquatic Toxicol. 78(1):74-90, 2006.
2. Han, X., Naab, D., Mingoia, R., and Yang, C-H. Determination of xenobiotic intrinsic clearance from freshly isolated hepatocytes from Rainbow trout (Oncorhynchus mykiss) and rat and its application in bioaccumulation assessment. Environm. Sci. and Technol. 41(9):3269-3279, 2007.
3. Jones, H. and J.B. Houston, Use of the Substrate Depletion Approach for Determining in Vitro Metabolic Clearance: Time Dependencies in Hepatocyte and Microsomal Incubations. Drug Metab Dispos, 32:973-982, 2004.

The assay has subsequently undergone further inter-laboratory ring testing and has been validated by the OECD and the Test Guideline (319B) published in June, 2018 :

https://www.oecd-ilibrary.org/environment/test-no-319b-determination-of-in-vitro-intrinsic-clearance-using-rainbow-trout-liver-s9-sub-cellular-fraction-rt-s9_9789264303232-en
GLP compliance:
no
Remarks:
Test performed in an internal lab
Specific details on test material used for the study:
Lot No. :VE00147685
Purity : 99.3%.
Expiry Date : 19 March, 2012
Radiolabelling:
no
Details on sampling:
An initial pre-study was performed in order to ascertain the metabolic turnover rate of FLORHYDRAL in the test system and, to determine the overall duration and required sampling timepoints for the deginitive study.

Metabolic Turnover Rate of Florhydral in Fish Liver S9 Fractions :
Initially, a range finding experiment was performed to determine the optimal incubation times to be used in the main experiments.
A stock solution of Florhydral (10 mM) was prepared freshly in methanol and diluted in water resulting in 10 µM solutions. Stock solutions of cofactors were prepared freshly in 0.1 M potassium phosphate buffer, pH 7.8. Alamethicin was dissolved in methanol (5 mg/ml; aliquots stored at -80°C) and diluted in buffer (250 µg/ml).
Rainbow Trout liver S9 fractions were thawed on ice. All incubations were performed in potassium phosphate buffer at pH 7.8 (0.1 M) in Hirschmann glass tubes in duplicate (range finding experiment) or triplicate (main experiments) incubated at 12°C in a Thermomixer (Eppendorf) at 700 rpm. Active S9 fractions protein or heat inactivated protein as control (1 mg/ml) was preincubated on ice with alamethicin (final concentration: 25 µg/ml). Alamethicin is a pore-forming peptide antibiotic which permeabilises microsomal membranes and activates glucuronidation by allowing free transfer of UDPGA and glucuronide product across the membrane. After addition of cofactors for Phase I (NADPH, Nicotinamide adenine dinucleotide 2′-phosphate reduced) and Phase II enzymes (UDPGA, Uridine 5′-diphosphoglucuronic acid; PAPS, Adenosine 3′-phosphate 5′-phosphosulfate; GSH, reduced L-glutathione), the reaction was initiated by addition of the test substance.
In the range finding experiment, Florhydral (1 µM) was incubated in presence of 1 mg/ml active S9 protein and cofactors in duplicate for up to 120 minutes. As controls, the test substance was incubated in presence of heat inactivated S9 protein (1 mg/ml) and cofactors or with active S9 protein, but without any cofactors. Reactions were stopped at 0, 30 minutes and 120 minutes incubation by addition of acetonitrile (200 µl) containing methyl laurate (1 µM) as internal standard to the Hirschmann tubes. Samples were extracted with MTBE (200 µl) in the same tubes by vortexing for 30 seconds, centrifuged to allow a better phase separation and separation of protein (Eppendorf centrifuge, 14 000 rpm, 5 min, room temperature) and subjected to GC-MS analysis.
In the two independent main experiments (1st and 2nd main experiment), Florhydral (1 µM) was incubated in presence of 1 mg/ml active S9 protein and cofactors in triplicate for up to 20 minutes as described above. Reactions were stopped at time 0, (2.5), 5, 10 minutes and 20 minutes. As control, the test substance was incubated in presence of heat inactivated S9 protein (1 mg/ml) and cofactors for 0 minutes and 20 minutes. Reactions were stopped and extracted as described above.

Impact of Individual Cofactors on the Metabolic Stability of Florhydral in Fish Liver S9 Fractions :
Since cell-free fractions are usually depleted of cofactors needed for Phase I or Phase II metabolism, cofactors have to be added to the assay to determine metabolic stability of compounds. To investigate which metabolic route may be involved in trout liver metabolism of Florhydral, we investigated the impact of individual cofactors on metabolic stability of the compound (3rd and 4th main experiment). Thus, Florhydral (1 µM) was incubated in triplicate in presence of 1 mg/ml S9 fractions and the standard cofactors (NADPH, UDPGA, PAPS) plus GSH, without any cofactors, without NADPH, without UDPGA, without PAPS, or without GSH in presence of all other cofactors. As control, Florhydral was incubated with heat inactivated S9 protein in presence of all cofactors. These cofactor experiments (3rd and 4th main experiment) were run in parallel with the 1st and 2nd main experiment, respectively.

Identification of metabolites of Florhydral in trout liver S9 fractions
Finally, we analyzed the metabolites of Florhydral formed in trout liver S9 fractions by GC-MS and LC-MS (5th main experiment). Higher test substance and protein concentrations were used.
Florhydral (10 µM) was incubated in presence of active S9 fractions (2 mg/ml), alamethicin and NADPH as single cofactor or NADPH plus UDPGA as cofactors. Samples (5 replicates) were stopped at 0 and 60 minutes incubation with MTBE containing 1 µM methyl laurate as internal standard, pooled and carefully concentrated to ca. 50 µl with a stream of nitrogen. Florhydral disappearance and formation of Florhydral alcohol were analyzed by GC-MS (fullscan method). To identify putative glucuronide metabolites, separate samples (5 replicates) were stopped with acid (50 µl 4 M HCl), and Ibuprofen added as internal standard (50 µM). After centrifugation to remove denatured protein, samples from 5 parallel incubations were pooled and loaded onto a SPE column (Oasis HLB µElution Plate), washed with 5% methanol, and eluted with 100% methanol (50 µl). Eluted samples were diluted with water (50 µl) and analyzed by LC-MS. The glucuronide of Florhydral was synthesized as reference material in house. Calibration curves of Florhydral and the putative metabolites Florhydral alcohol, Florhydral acid and Florhydral alcohol glucuronide were prepared in buffer in presence of inactive protein (0-10 µM) and analyzed by GC-MS or LC-MS.
Vehicle:
yes
Details on preparation of test solutions, spiked fish food or sediment:
A stock solution of Florhydral (10 mM) was prepared freshly in methanol and diluted in water resulting in 10 µM solutions.
Test organisms (species):
Oncorhynchus mykiss (previous name: Salmo gairdneri)
Details on test organisms:
Trout Liver S9 Fractions :
Rainbow Trout (Oncorhynchus mykiss) liver S9 fractions were purchased from Lifetechnologies (formerly CellzDirect/Invitrogen) (“Pooled Male Hatchery Rainbow Trout Liver S9”; product code CZDTRS9PL, Lot# TR015) and stored at -80°C. The average body weight of the fish used for the preparation of S9 fractions was 800 g. The enzymatic activity of newly received S9 fractions was typically tested using internal fragrance reference molecules which are degraded by different enzyme systems (Phase I or Phase II). Furthermore, enzymatic activity was tested with Testosterone and Umbelliferone (7-Hydroxycoumarin) as controls to determine the activity of CYP3A (Cytochrome P450 monooxygenase), UDP-Glucuronosyltransferase and Sulfotransferase . S9 fractions were only used for metabolism studies if significant enzymatic conversion of the reference substances was observed. Aliquots of S9 fractions were prepared to prevent several thawing and freezing cycles to avoid inactivation of enzymes. Heat inactivated S9 fractions were prepared by heating 100 µl aliquots at 100°C using a Biometra Thermocycler and stored at -80°C.
Route of exposure:
other: In vitro study exposing Trout liver S9 fraction to FLORHYDRAL in glass tubes. Exposures performed in Potassium Phosphate Buffer (pH 7.8, 0.1 M).
Justification for method:
other: Metabolism is a key element in determining the potential of a chemical substance to bioconcentrate / bioaccumulate.
Remarks:
In the absence of In vivo fish-BCF testing, the surrogate adopted to identify potential of a chemical substance to bioconcentrate is the LogPow. Metabolism is, however, a key element in determining the uptake, distribution and elimination.
Test type:
other: Static (single application) In vitro metabolism assay determining the Intrinsic Clearance Rate of the test item (CLint)
Water / sediment media type:
other: Rainbow Trout S9 liver cells in Potassium Phosphate buffer
Total exposure / uptake duration:
20 min
Test temperature:
12.5 +/- 2.5°C
pH:
pH 7.8
Details on test conditions:
Assay conditions using trout liver S9 fractions:

Addition of: Final concentration
90 µl K-Phosphate buffer, pH 7.8 (0.1 M) 0.1 M K-Phosphate buffer, pH 7.8
10 µl S9 protein (20 mg/ml) 1 mg/ml protein
Preincubation for 5 min at 12.5 ± 2.5 °C (700 rpm)
20 µl Alamethicin (250 µg/ml) 25 µg/ml Alamethicin
Incubation on ice for 15 min; pre-incubation at 12°C for 10 min
Addition of cofactors:
20 µl NADPH (10 mM) 1 mM NADPH
20 µl UDPGA (20 mM) 2 mM UDPGA
20 µl GSH (5 mM) 0.5 mM GSH
20 µl PAPS (1 mM) 0.1 mM PAPS
20 µl test substance in water (10 µM) 1 µM test substance
Final volume in Hirschmann tubes: 200 µl
Incubation at 12.5 ± 2.5 °C (700 rpm) for different time points

For separate study for Determination of Metabolites, a higher starting concentration of FLORHYDRAL (10 microM) was employed :

Assay conditions using trout liver S9 fractions to identify metabolites:
Addition of: Final concentration
118 or 138 µl K-Phosphate buffer, pH 7.8 (0.1 M) 0.1 M K-Phosphate buffer, pH 7.8
20 µl S9 protein (20 mg/ml) 2 mg/ml protein
Preincubation for 5 min at 12.5 ± 2.5 °C (700 rpm)
20 µl Alamethicin (250 µg/ml) 25 µg/ml Alamethicin
Incubation on ice for 15 min; pre-incubation at 12°C for 10 min
Addition of cofactors:
20 µl NADPH (10 mM) 1 mM NADPH
20 µl UDPGA (20 mM) 2 mM UDPGA
2 µl Florhydral in 60% Methanol (1mM) 10 µM Florhydral
Final volume in Hirschmann tubes: 200 µl
Incubation at 12.5 ± 2.5 °C (700 rpm) for 1 hour.
Nominal and measured concentrations:
Nominal starting concentration in the Metabolic Turnover part of the study was 1 microM of FLORHYDRAL.

Nominal starting concentration in theassay considering formation of Metabolites was 10 microM of FLORHYDRAL.
Reference substance (positive control):
yes
Details on estimation of bioconcentration:
Confirmation of Validity of S9 Liver Fractions using Testosterone and Umbelliferone :
Enzymatic turnover of Testosterone (CYP3A activity) and Umbelliferone (glucuronidation and sulfation activity) were determined to validate the S9 liver fractions.
Remarks on result:
not measured/tested
Rate constant:
other: Intrinsic Clearance Rate (CLint) - mL/h/mg protein
Value:
7.06
Remarks on result:
other: Intrinsic Clearance rate in 1st main experiment.
Rate constant:
other: Intrinsic Clearance Rate (CLint) - mL/h/mg protein
Value:
8.29
Remarks on result:
other: Intrinsic Clearance rate in 2nd main experiment.
Details on kinetic parameters:
The in vitro intrinsic clearance (CLint, in vitro) was calculated from the log-transform measured concentrations of parent compound as a function of time in two independent experiments: 7.06 and 8.29 ml/h/mg protein.

Metabolites:
Metabolites were studies in a separate assay to consider Phase I and Phase II metabolism processes.

Identification of Phase I and Phase II Metabolites of Florhydral in Fish Liver S9 Fractions
We identified Florhydral alcohol as major metabolite of Florhydral in trout liver S9 fractions with NADPH as single cofactor or NADPH plus UDPGA as cofactors by GC-MS. Florhydral acid (~2 µM) was detected in trout liver S9 fractions with NADPH as single cofactor or NADPH plus UDPGA by LC-MS. Furthermore, the O-glucuronide of Florhydral alcohol was found as a phase II metabolite in samples analyzed by LC-MS using synthesized glucuronide as reference material. Ca. 2 µM of Florhydral alcohol glucuronide was detected in samples incubated with NADPH and UDPGA as cofactors, whereas no glucuronide was detected in absence of UDPGA as cofactor or with inactive protein.
Results with reference substance (positive control):
Testosterone underwent approx. 60% metabolic turnover during the 120 minute incubation.

Metabolic Turnover Rate– FLORHYDRAL demonstrated rapid metabolic turnover in the presence of active Trout Liver S9 fractions in both of the separate metabolic turnover rate investigations with a decrease of 93.1 and 93.6% in FLORHYDRAL concentrations following 20 minutes of exposure to active S9 + cofactors +GSH c.f. a decrease of 3.8 and 2.4% observed for the samples with heat inactivated protein + cofactors +GSH.


Impact of Individual Cofactors on Metabolic Stability of FLORHYDRAL in Fish Liver S9 Fractions– In this part of the experiment it was observed that the absence of both EDPGA and PAPS as cofactors did not inhibit the metabolic turnover rate of FLORHYDRAL (92.2 to 95.5% turnover within 20 minutes). Contrastingly, in the absence of NADPH as a cofactor, the rate of turnover decreased significantly to 10.6 to 11.7%, similar to the level of decrease observed in the absence of any cofactors. The dependence of enzymatic turnover on NADPH indicates the involvement of a Cytochrome P450 monooxygenase or reductase.


Identification of Metabolites of FLORHYDRAL in Trout Liver S9 Fractions– FLORHYDRAL alcohol was identified as the major metabolite of FLORHYDRAL in Trout liver S9 fractions. In addition, the O-glucuronide of FLORHYDRAL alcohol was observed as a Phase II metabolite. The acid of FLORHYDRAL was also detected.


Validity criteria fulfilled:
not applicable
Conclusions:
FLORHYDRAL underwent rapid biotransformation in Rainbow Trout (O. mykiss) liver S9 fractions under in vitro exposure conditions (average of 93.4% turnover after 20 minutes). The metabolic turnover of FLORHYDRAL appears to be dependent upon the presence of Cytochrome P450 monooxygenase and/or reductase enzymes.

The in vitro intrinsic clearance (CLint, in vitro) was calculated from the log-transform measured concentrations of parent compound as a function of time in two independent experiments: 7.06 and 8.29 ml/h/mg protein.

Rapid enzymatic turnover of Florhydral by trout liver S9 fractions was observed. Therefore, the bioaccumulation potential in vivo is likely to be low compared to the bioaccumulation potential calculated based on logKow.
Florhydral is probably reduced by a dehydrogenase or a reductase to the corresponding alcohol. The Florhydral alcohol is a potential substrate for UDP-Glucuronosyltransferases resulting in an O-glucuronide as metabolite which may be more easily excreted than the educt. The identity of the Florhydral alcohol glucuronide was confirmed by comparison with synthesized reference material by LC-MS. Furthermore, Florhydral was oxidized to the corresponding acid.
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Study period:
16 October, 2019
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
LogPow of FLORHYDRAL is relatively low (3.1), and, very rapid metabolism was observed in an In vitro study performed with Rainbow Trout liver S9 cells suggesting that the bioconcentration and bioaccumulation potential of FLORHYDRAL is low.
Qualifier:
no guideline followed
Principles of method if other than guideline:
QSAR Predictions : BCFBAF (v3.01) Module of EPISuite (v4.11)
The BCFBAF Program is an update and expansion of the previous BCFWIN Program that was part of the EPI Suite version 3.20.  The update pertains to estimation of Bioconcentration Factor (BCF).  The BCFBAF program estimates BCF of an organic compound using the compound's log octanol-water partition coefficient (Kow).  For the update, a more recent and better evaluated database of BCF values was used for both training and validation.  The BCF data were re-regressed using the same methodology as in the original BCFWIN program.

 The original estimation methodology used by the original BCFWIN program is described in a document prepared for the U.S. Environmental Protection Agency (Meylan et al., 1997).  The estimation methodology was then published in journal article (Meylan et al, 1999).  The methodology is described in the Bioconcentration Factor Estimation section.

BCFBAF has been expanded to include estimation of the Biotransformation Rate (kM) in fish and estimation of Bioaccumulation Factor (BAF) by the Arnot-Gobas method (Arnot and Gobas, 2003).

 BCFBAF requires only a chemical structure to estimate BCF, BAF and kM.  Structures are entered into BCFBAF through SMILES (Simplified Molecular Input Line Entry System) notations.  The six available methods of entering a SMILES into BCFBAF are listed in the Entering SMILES section.

BCFBAF estimates a log Kow for every SMILES notation by using the estimation module of the KOWWIN program (which is part of the EPI Suite).  BCFBAF also automatically retrieves experimental log Kow values from a database containing more than 13200 organic compounds with reliably measured values.  When a SMILES structure matches a database structure (via an exact atom-to-atom connection match), the experimental log Kow value is retrieved and used to predict BCF, BAF and kM rather than the estimated value.

https://www.epa.gov/tsca-screening-tools/epi-suitetm-estimation-program-interface
GLP compliance:
no
Specific details on test material used for the study:
FLORHYDRAL :
SMILES annotation : O=CCC(c1cccc(c1)C(C)C)C
LogPow : 3.1 (entered manually)
Key result
Type:
BCF
Value:
101 L/kg
Basis:
other: QSAR Prediction : BCFBAF (v3.01), EPISuite (v4.11) - Arnot-Gobas Upper Trophic
Calculation basis:
other: QSAR Prediction : BCFBAF (v3.01), EPISuite (v4.11) - Arnot-Gobas Upper Trophic
Details on results:
BCFBAF Program (v3.01) Results:
==============================
SMILES : O=CCC(c1cccc(c1)C(C)C)C
CHEM : FLORHYDRAL
MOL FOR: C13 H18 O1
MOL WT : 190.29
--------------------------------- BCFBAF v3.01 --------------------------------
Summary Results:
Log BCF (regression-based estimate): 1.71 (BCF = 51.6 L/kg wet-wt)
Biotransformation Half-Life (days) : 1 (normalized to 10 g fish)
Log BAF (Arnot-Gobas upper trophic): 2.01 (BAF = 101 L/kg wet-wt)

Log Kow (experimental): not available from database
Log Kow used by BCF estimates: 3.10 (user entered)

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 = 1.712 (BCF = 51.57 L/kg wet-wt)

===========================================================
Whole Body Primary Biotransformation Rate Estimate for Fish:
===========================================================
------+-----+--------------------------------------------+---------+---------
TYPE | NUM | LOG BIOTRANSFORMATION FRAGMENT DESCRIPTION | COEFF | VALUE
------+-----+--------------------------------------------+---------+---------
Frag | 1 | Aldehyde [-CHO] | 0.2465 | 0.2465
Frag | 2 | Alkyl substituent on aromatic ring | 0.1781 | 0.3561
Frag | 2 | Aromatic-CH | -0.4629 | -0.9259
Frag | 4 | Aromatic-H | 0.2664 | 1.0655
Frag | 3 | Methyl [-CH3] | 0.2451 | 0.7353
Frag | 1 | -CH2- [linear] | 0.0242 | 0.0242
Frag | 1 | Benzene | -0.4277 | -0.4277
L Kow| * | Log Kow = 3.10 (user-entered ) | 0.3073 | 0.9528
MolWt| * | Molecular Weight Parameter | | -0.4880
Const| * | Equation Constant | | -1.5371
============+============================================+=========+=========

RESULT | LOG Bio Half-Life (days) | | 0.0018
RESULT | Bio Half-Life (days) | | 1.004
NOTE | Bio Half-Life Normalized to 10 g fish at 15 deg C |
============+============================================+=========+=========

Biotransformation Rate Constant:
kM (Rate Constant): 0.6903 /day (10 gram fish)
kM (Rate Constant): 0.3882 /day (100 gram fish)
kM (Rate Constant): 0.2183 /day (1 kg fish)
kM (Rate Constant): 0.1228 /day (10 kg fish)

Arnot-Gobas BCF & BAF Methods (including biotransformation rate estimates):
Estimated Log BCF (upper trophic) = 2.005 (BCF = 101.2 L/kg wet-wt)
Estimated Log BAF (upper trophic) = 2.005 (BAF = 101.2 L/kg wet-wt)
Estimated Log BCF (mid trophic) = 1.877 (BCF = 75.29 L/kg wet-wt)
Estimated Log BAF (mid trophic) = 1.877 (BAF = 75.36 L/kg wet-wt)
Estimated Log BCF (lower trophic) = 1.831 (BCF = 67.77 L/kg wet-wt)
Estimated Log BAF (lower trophic) = 1.833 (BAF = 68.04 L/kg wet-wt)

Arnot-Gobas BCF & BAF Methods (assuming a biotransformation rate of zero):
Estimated Log BCF (upper trophic) = 2.130 (BCF = 135 L/kg wet-wt)
Estimated Log BAF (upper trophic) = 2.199 (BAF = 158.1 L/kg wet-wt)

Conclusions:
Estimated LogBCF using Arnot-Gobas upper trophic level module of BCFBAF (v3.01) QSAR in EPISuite (v4.11) :
LogBCF = 2.005 (BCF = 101.2 l/kg wet wt.).

Estimated LogBCF using Regression based estimate module of BCFBAF (v3.01) QSAR in EPISuite (v4.11) :
LogBCF = 1.71 (BCF = 51.6 L/kg wet wt.).

Description of key information

BIOCONCENTRATION :

Predictive QSAR models (EPISuite BCFBAF, OASIS-CATALOGIC BCF BaseLine) indicate that FLORHYDRAL has a low potential to bioaccumulate in fish. The latter model indicated that the metabolism step would derive the Florhydral-Acid in the first instance. Predicted BCF values for FLORHYDRAL using the Arnot Gobas and Regression model of BCFBAF (v3.01), EPISuite (v4.11), are 101 L/kg and 52 L/kg, respectively.


In addition to this, an In vitro metabolism study using Rainbow Trout liver S9 (equivalent to the OECD 319B Test Guideline) was performed to determine the metabolism kinetics of FLORHYDRAL and establish the intrinsic clearance rate (CLint). This assay illustrated > 90% metabolic turnover of FLORHYDRAL within 20 minutes of exposure. Both Florhydral-Acid and Florhydral-Alcohol were identified as metabolites as was the glucuronide conjugate of the alcohol derivative. This assay further confirmed the low potential to bioaccumulate of FLORHYDRAL. 

Key value for chemical safety assessment

BCF (aquatic species):
101 L/kg ww

Additional information

BIOCONCENTRATION :

Predictive QSAR models (EPISuite BCFBAF, OASIS-CATALOGIC BCF BaseLine) indicate that FLORHYDRAL has a low potential to bioaccumulate in fish. The latter model indicated that the metabolism step would derive the Florhydral-Acid in the first instance. Predicted BCF values for FLORHYDRAL using the Arnot Gobas and Regression model of BCFBAF (v3.01), EPISuite (v4.11), are 101 L/kg and 52 L/kg, respectively.


In addition to this, an In vitro metabolism study using Rainbow Trout liver S9 (equivalent to the OECD 319B Test Guideline) was performed to determine the metabolism kinetics of FLORHYDRAL and establish the intrinsic clearance rate (CLint). This assay illustrated > 90% metabolic turnover of FLORHYDRAL within 20 minutes of exposure. Both Florhydral-Acid and Florhydral-Alcohol were identified as metabolites as was the glucuronide conjugate of the alcohol derivative. This assay further confirmed the low potential to bioaccumulate of FLORHYDRAL

.