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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27 days
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: In accordance with recognised guidelines
Qualifier:
according to guideline
Guideline:
OECD Guideline 305 (Bioconcentration: Flow-through Fish Test)
Deviations:
no
GLP compliance:
yes
Radiolabelling:
yes
Vehicle:
not specified
Test organisms (species):
Lepomis macrochirus
Route of exposure:
aqueous
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
17 d
Total depuration duration:
10 d
Nominal and measured concentrations:
Average measured exposure concentration of 93 µ/L
Details on estimation of bioconcentration:
Calculated, based on measured residues
Type:
BCF
Value:
122
Basis:
edible fraction
Time of plateau:
1 d
Calculation basis:
steady state
Remarks on result:
other: Conc.in environment / dose:19 µg/L
Type:
BCF
Value:
877
Basis:
non-edible fraction
Time of plateau:
1 d
Calculation basis:
steady state
Remarks on result:
other: Conc.in environment / dose:19 µg/L
Type:
BCF
Value:
621
Basis:
whole body w.w.
Time of plateau:
1 d
Calculation basis:
steady state
Remarks on result:
other: Conc.in environment / dose:19 µg/L
Elimination:
yes
Parameter:
DT50
Depuration time (DT):
0.3 d

The residual radioactivity in fish body increased rapidly and reached a maximum after about one day of exposure. Thereafter, the concentration remained constant at 16 to 57,  11 to 65, and 0.9 to 13 µg parent equivalents/g fish in non-edible tissues, whole fish, and edible tissues, respectively. The residues in the edible and non-edible tissues were mainly comprised of CGA 153433. Because bioconcentration of the metabolite CGA 153433 was unlikely to occur (log POW = -0.75), it is assumed that cloquintocet-mexyl was accumulated and immediately metabolised into CGA 153433. Consequently, for the estimation of bioconcentration factors (BCF), it is assumed, that residual radioactivity in fish parts initially represented accumulated cloquintocet-mexyl. Based on the total radioactivity in fish, the BCF values are calculated to be 122,  877, and 621 in edible tissues, non-edible tissues, and whole fish respectively. After transferring the fish to clean flowing water, the radioactivity decreased very rapidly with half-lives ranging from 0.3 to 0.6 days. After 10 days depuration, residual radioactivity was below the limit of quantification.  

Therefore, bioconcentration of cloquintocet-mexyl is not considered to be of concern as it is rapidly metabolised and eliminated in fish and since the primary metabolite of cloquintocet-mexyl (CGA 153433) has negligible bioaccumulation potential.

Validity criteria fulfilled:
yes
Conclusions:
In a flow-through test with L. macrochirus, exposed to an average of 19 µg/L, based on the total radioactivity in fish, the BCF values are calculated to be 122, 877, and 621 in edible tissues, non-edible tissues, and whole fish respectively. After transferring the fish to clean flowing water, the radioactivity decreased very rapidly with half-lives ranging from 0.3 to 0.6 days. After 10 days depuration, residual radioactivity was below the limit of quantification.
Executive summary:

In a flow-through test with L. macrochirus, exposed to an average of 19 µg/L, based on the total radioactivity in fish, the BCF values are calculated to be 122, 877, and 621 in edible tissues, non-edible tissues, and whole fish respectively. After transferring the fish to clean flowing water, the radioactivity decreased very rapidly with half-lives ranging from 0.3 to 0.6 days. After 10 days depuration, residual radioactivity was below the limit of quantification.

Description of key information

The bioaccumulation and depuration of cloquintocet-mexyl in bluegill sunfish (Lepomis macrochirus) was investigated in one study (Burri, 1993). The substance is rapidly metabolised and eliminated in fish, whilst the primary metabolite has negligible bioaccumulation potential.

Key value for chemical safety assessment

BCF (aquatic species):
621 dimensionless

Additional information

The bioaccumulation and depuration of cloquintocet-mexyl (log Pow = 5.2) in bluegill sunfish (Lepomis macrochirus) was investigated by Burri (1993) using a dynamic flow-through system. The study was GLP compliant, conducted to OECD TG 305 and is considered to be reliable without restrictions.
The fish were continuously exposed (flow-through system) to 14C-labelled cloquintocet-mexyl for 17 days. In the exposure water, cloquintocet-mexyl was partially hydrolysed to Acetic acid, 2-[(5-chloro-8-quinolinyl)oxy]-, the main environmental metabolite of cloquintocet-mexyl. The residual radioactivity in fish body increased rapidly and reached a maximum after about one day of exposure. The residues in the edible and non-edible tissues were mainly identified as the metabolite. It is assumed that residual radioactivity in fish parts initially represented accumulated cloquintocet-mexyl, which was then immediately metabolised. Therefore, bioconcentration of cloquintocet-mexyl is not considered to be of concern as it is rapidly metabolised and eliminated in fish, whilst the primary metabolite of cloquintocet-mexyl, ( Acetic acid, 2-[(5-chloro-8-quinolinyl)oxy]-), has negligible bioaccumulation potential.

Based on the total radioactivity in fish, the BCF values are calculated to be 122, 877, and 621 in edible tissues, non-edible tissues, and whole fish, respectively. After transferring the fish to clean flowing water, the radioactivity decreased very rapidly with half-lives ranging from 0.3 to 0.6 days. After 10 days depuration, residual radioactivity was below the limit of quantification.

Therefore, bioconcentration of cloquintocet-mexyl is not considered to be of concern as it is rapidly metabolised and eliminated in fish and since the primary metabolite of cloquintocet-mexyl, ( Acetic acid, 2-[(5-chloro-8-quinolinyl)oxy]-, has negligible bioaccumulation potential.

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