Mecoprop

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25 September 1986 to 04 December 1986

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EPA 540/9-82-024: Pesticide Assessment Guidelines, Subdivision E, Hazard Evaluation: Wildlife and Aquatic Organisms: Aquatic Organism Testing, Paragraph 72-6 1(1982)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- The total radioactive test material was dissolved in 10.0 mL ethanol and its amount determined by liquid scintillation counting to be 48.91 mg (<= 8.8714 mCi). To 17.775 g unlabelled test material (purity = 94.9 %) dissolved in about 180 mL ethanol, 5.733 mL of the radioactive stock solution (= 28.04 mg or 5086 microCi) were added and the solution made up to 200.0 mL. The specific radioactivity obtained was 0.286 microCi/mg. Thereafter, 28 aliquots of 6.741 mL of the dilution were placed into graduated glass tubes and stored until use at -20 °C.

Radiolabelling:

yes

Details on sampling:

- Sampling intervals/frequency for test organisms: Samples of 15 fish were taken from treated tanks per sampling interval for analysis of residual radioactivity in edible and non-edible parts and in the whole fish. Samples were taken 1 hour after starting the dosage and at day 3, 7, 14, 21 and 28 of exposure. During depuration, samples were taken at day 1, 3, 7 1 10 and 14. Control fish from the control tank were taken at day 0 and 28 of the exposure period. They served as background control. Additional 25 and 20 fish were taken for analysis of extractable and non-extractable radioactivity as well as number and nature of metabolites in edibles at day 21 and 28 of the exposure period, respectively.
- Sampling intervals/frequency for test medium samples: The concentration of test material in both exposure tanks was controlled by 14C-determinations at day 0, 1, 2, 3, 7, 8,14, 21 and 28 of the exposure period and at day 1, 7 and 14 of the depuration period. In addition, water samples of the control tank were analysed for radioactivity background at day 0, 14 and 28 of the exposure period. Water samples were also analysed for amount of parent molecule and amount of metabolites at day 3, 7, 21 and 28 of exposure.
- Details on sampling and analysis of test organisms and test media samples:
Water: Triplicate water samples of one mL each were taken from the respective tanks and the radioactivity determined directly by liquid scintillation counting. In addition, 100 mL water were taken for analysis and stored at -20°C until analysis.
Fish: Immediately after removal from the tanks, the fish (three groups of 5 fish) were killed by decapitation, separated into head, gills, viscera and fins (non-edibles) and into residual carcass (edibles, mainly representing fillets). The fresh-weights of pooled edibles and non-edibles were determined and thereafter edibles and non-edibles lyophilised, the dry-weight taken, homogenised in a mill and aliquots submitted to radioactivity determination. Edibles of fish used for analysis of number and nature of metabolites present were processed in the same way.

Vehicle:

yes

Details on preparation of test solutions, spiked fish food or sediment:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: To 6.741 ml of the ethanol stock solution containing 600 mg diluted test material 6.0 g Tween 80 were added, mixed and the solution quantitatively dissolved in 9.0 L of tap water. This stock solution was continuously stirred and delivered via the dispenser into the mixing flasks. The flow was adjusted so that 4.5 L stock solution were mixed with about 295.5 L of water within 24 hours and fed into the respective tank. The resulting concentration of the test material was about 1.0 ppm.

Test organisms (species):

Lepomis macrochirus

Details on test organisms:

TEST ORGANISM
- Common name: Bluegill sunfish
- Weight at study initiation: 2.4 g average weight on day 0
- Weight at termination: 3.0 g average weight on day 28
- Description of housing/holding area: Aerated tanks containing 100 L of water
- Feeding during test
- Food type: Fish feed or meat
- Amount: ad Llibitum
- Frequency: Daily

ACCLIMATION
- Acclimation period: 3 weeks
- Acclimation conditions: Acclimatised in the same laboratory environment as the test
- Health during acclimation: No mortality observed with all fish during whole study

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

other: Tap water

Total exposure / uptake duration:

28 d

Total depuration duration:

14 d

Test temperature:

19 to 20 °C

pH:

7.7 to 8.0

Dissolved oxygen:

9.2 to 5.5 mg O2/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Tanks
- Type: open
- Material, size, headspace, fill volume: 100 mL of water was added to the tanks
- Aeration: each tank was aerated, aerated stirrer used
- Renewal rate of test solution: 300 L/day
- No. of organisms per vessel: Control tank had 50 fish, each treated tank had 150 fish
- No. of vessels per concentration: 2
- No. of vessels per control: 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water was used as dilution water
- Intervals of water quality measurement: The pH, temperature and oxygen concentration in the water was controlled daily during the exposure and depuration period of the study
- Intervals of test medium replacement: Daily

OTHER TEST CONDITIONS
- Adjustment of pH: pH was controlled daily during the exposure and depuration period
- Photoperiod: Fish were illuminated 12 hours daily
- Light intensity: 2000 Lux

RANGE-FINDING / PRELIMINARY STUDY
- In a pre-test, the toxicity of the test material to Bluegill Sunfish was checked. For this purpose, four fish each were exposed for 96 hours to un-labelled test material at concentrations of 0, 1 and 10 mg/L. No mortality was observed at concentrations up to 10.0 mg/L. Based on these findings, a concentration of the compound of 1.0 mg/L was selected for the flow-through experiment.

Nominal and measured concentrations:

Nominal concentration: 1.0 mg/L

Reference substance (positive control):

no

Key result

Conc. / dose:

0.99 other: ppm

Temp.:

> 19 - < 20 °C

pH:

7.7

Type:

BAF

Value:

3 other: mg / kg

Basis:

whole body w.w.

Time of plateau:

14 d

Calculation basis:

steady state

Conc. / dose:

0.99 other: ppm

Temp.:

> 19 - < 20 °C

pH:

7.7

Type:

BAF

Value:

5.43 other: mg / kg

Basis:

non-edible fraction

Time of plateau:

14 d

Calculation basis:

steady state

Conc. / dose:

0.99 other: ppm

Temp.:

> 19 - < 20 °C

pH:

7.7

Type:

BAF

Value:

1.2 other: mg / kg

Basis:

edible fraction

Time of plateau:

14 d

Calculation basis:

steady state

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

37.9 h

Remarks on result:

other: non-edible parts

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

27.4 h

Remarks on result:

other: Whole fish

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

7.8 h

Remarks on result:

other: Edible parts

Metabolites:

The pattern of metabolites determined for the organic-soluble radioactivity of edible parts of fish exposed for 21 and 28 days to test material is presented in 'Pattern of metabloites in extractables of edibles of fish exposed to test material'.
The table shows that besides the parent molecule (M3), three further metabolites were present (M1, M2 and M4). After 21 days, the amounts were 0.12, 0.05, 0.24 and 0.34 ppm for M1, M2, M3 and M4, respectively. The corresponding figures found after 28 days were 0.19, 0.13, 0.23 and 0.47 ppm. Metabolites M1 and M2 represented minor metabolites of unknown nature. M3 behaved on TLC as the parent molecule. Metabolite M4 was found to be less polar than the parent molecule and behaved on TLC similar to the methylated parent compound. Whether M4
represented a genuine metabolite or an artefact formed during work-up of the methanol-water extracts cannot be decided. However, it has to be pointed out that none of the metabolites has a significance in the edibles of fish, since no radioactivity was retained by the edible fractions of the fish as shown in the depuration study.

Details on results:

BIOACCUMALATION IN FISH:
Residues in fish and in the edible and non-edible parts of fish during the uptake phase are presented in Tables 'Residues in fish during exposure to test material' and 'Residues (background) in untreated fish'. The residue values, calculated as parent equivalents according to the radioactivity found in fish or fish parts, are based on the fresh weight of the respective material. They reached a plateau 14 days after starting the exposure. The plateau values were, on average, 1.18 +/- 0.18, 5.43 +/- 0.16 and 2.99 +/- 0.09 mg/kg in edible parts, non-edible parts and the whole fish, respectively. When the above given values were related to the actual concentration of radioactivity (Test material equivalents) representing, on average, 0.99 mg/L in both tanks a bioaccumulation factor (BF) of 1.2, 5.5 and 3.0 was obtained for edible parts, non-edible parts and the whole fish, respectively. Based on the water solubility of the test material of 620 mg per litre (= 2880 micromol / L), the n-octanol/water partition coefficient (P) was calculated using the following equation:
Log P = 5.00 – 0.67log S (S = 2880)
Log P = 2.68
P = 481.
Based on the above log P value, the following bioaccumulation factor would have been expected from literature data, using the following equation established for catfish:
log BF = 0.83 x log P - 1.71
= 0.83 X 2.68 - 1.71
= 0.52
BF = 3.3.
This theoretical value fits very well into the experimental value of BF= 3 established in the flow-through system. In conclusion, the test material was only accumulated to a very limited extent in non-edibles which was shown by the formation of a clear plateau value (5.4 ppm). No accumulation was observed in edible parts since the levels of radioactivity were of the same order of magnitude as the surrounding water. These figures clearly demonstrate that the bioaccumulation properties of the test material are very low and are predominantly based on the physical-chemical properties (low lipophilicity) of the herbicide.


DEPURATION OF TEST MATERIAL:
Depuration of radioactivity from Bluegill Sunfish after exposure to test material is shown in Table 'Residues in fish during depuration'. Depuration was very rapid within the first 3 days, i.e. the residual radioactivity dropped to 14.1, 20.4 and 18.5 %. Of their values at the beginning of the depuration period in edible parts, non-edible parts, and whole fish respectively. Thereafter, a significant decrease in the depuration rate was observed. The elimination rate of residual radioactivity can be satisfactorily described by second-order reaction kinetics. For the whole fish, edibles and non-edibles the following equations could be established:
whole fish: 1/Rt = 0.28 x t + 0.56 (R* = 0.98)
edible parts: 1/Rt = 2.27 x t - 0.60 (R* = 0.99)
non-edible parts: 1/Rt = 0.12 x t - 0.33 (R* = 0.97)
R* = correlation coefficient
Based on these findings, the half-lives for the initial residues are as follows.
T/2 whole fish = (1/28) x (1/3.09) = 27.4 hours
T/2 edible parts = (1/2.27) x (1/1.35) = 7.8 hours)
T/2 non-edible = (1/0.12) x (1/5.35) = 37.9 hours)

As indicated above and based on second-order reaction kinetics, the half-life increases significantly when lower values of the residual radioactivity are reached due to the fact that the second factor of the above equations increases when the residual radioactivity decreases. However, it has to be stated that second-order reaction kinetics are known to occur for the elimination of pesticides/pesticide residues from fish. However, at the end of the study residual radioactivity amounted to 0.03, 0.64 and 0.29 mg/kg only for edible parts, non-edible parts and whole fish, respectively. Based on residues observed with untreated control fish (Table 'Residues in fish during depuration'), the above given figures are at the limit of detection, at the limit of quantification (double background) or below the limit of quantification.


ANALYSIS OF RADIOACTIVITY IN EXPOSURE WATER:
Practically all radioactivity in the exposure water was found to be extractable with ethyl acetate, amounting to 96.8, 97.8, 100.0 and 100.0 % at day 3, 7, 21 and 28, respectively. The aqueous-soluble radioactivity amounted for the corresponding sampling intervals to 3.2, 2.2, 0 and O % of the radioactivity present in the exposure water. Analysis of the radioactivity in the ethyl acetate extracts showed only the presence of the parent molecule. These data indicate that the test article was stable in the exposure water.


ANALYSIS OF RADIOACTIVITY IN EXPOSURE WATER:
78.5 % and 82.0 % of the radioactivity present in edibles of fish exposed for 21 and 28 days to the test material were extractable. These figures correspond to a residue of 0.93 ppm and 1.11 ppm. The corresponding figures for non-extractables were 21.5 % and 18.0 % of the radioactivity found in edibles. The latter values correspond to 0.26 ppm and 0.24 ppm. When the extractable radioactivity was partitioned with un-polar organic solvents, 63.1 % to 75.3 % of the radioactivity present in edibles were found to be extractable with un-polar solvents and only smaller amounts of radioactivity remained in the water phase (15.4 1. to 6.7 %) which could not be further analysed due to its low amount of radioactivity present.

Table 'Residues in fish during exposure to test material'

Exposure time (days)	Residues* (mg / kg = ppm)
	edibles	non-edibles	whole fish
0**	0.39	0.73	0.56
3	0.74	4.2	2.15
7	0.93	4.33	2.35
14	0.99	5.33	2.91
21	1.19	5.62	2.98
28	1.35	5.35	3.09
Average**	1.18	5.43	2.99
+/- s.d	0.18	0.16	0.09

* Values represent mean of 3 groups of 5 fish each.
** One hour after starting dosage.
*** Average day 14-28: plateau value

 

Table 'Residues (background) in untreated fish'

Exposure time (days)	Residues* (mg / kg = ppm)
	edibles	non-edibles	whole fish
0**	0.39	0.31	0.36
28	0.38	0.35	0.37
Average	0.39	0.33	0.37

* Values represent mean of 3 groups of 5 fish each.
** One hour after starting dosage

 

Table 'Residues in fish during depuration'

Depuration time (days)	Residues* (mg / kg = ppm)
	edibles	non-edibles	whole fish
0**	1.35	5.35	3.09
1	0.45	2.2	1.21
3	0.19	1.09	0.57
7	0.07	0.87	0.4
10	0.05	0.65	0.31
14	0.03	0.64	0.29

* Values represent mean of 3 groups of 5 fish each.
** Day 28 of exposition = day 0 of depuration

 

Table 'Pattern of metabloites in extractables of edibles of fish exposed to test material'

Code	Identity	Rf-value SS 2	Exposure time (days)
			21		28
			%**	ppm	%**	ppm
M1	Unknown	0.40	10.3	0.12	14.4	0.19
M2	Unknown	0.56	4.0	0.05	9.6	0.13
M3	Mecoprop	0.79	19.9	0.24	16.8	0.23
M4	Mecoprop-methyl	0.97	28.9	0.34	34.5	0.47
N.a	(water-soluble)*		15.4	0.18	6.7	0.09
Total			78.5	0.93	82.0	1.11

(values represent mean of fish of tanks 2 and 3)
* Radioactivity remaining in the water phase after partitioning;due to low amount not analysed (n.a.).

** In % of the radioactivity found in the edible parts of fish.

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of this study, it was found that the test material is not accumulated to a significant extent by fish and does not represent a hazard for aquatic food chains.

Executive summary:

The bioaccumulation and elimination of the test material by Bluegill Sunfish was investigated in a dynamic flow-through system in accordance with EPA Guidelines 540/9-82-024 and in compliance with GLP.

The fish were continuously exposed to a mean concentration of test material of about 1.0 mg/L of tap water for 28 days at 20 +/- 0.5 °C. Thereafter, the fish were transferred to flowing, untreated water for 14 days and the elimination of radioactivity followed. Based on the average amount of radioactivity in the water and the residual radioactivity found in edibles, non-edibles and in the whole fish, bioaccumulation factors of 1.2, 5.5 and 3.0 were determined, respectively. Elimination of radioactivity from edibles, non-edibles and the whole fish was found to be rapid at the beginning of the depuration phase with half-lives of 7.8, 37.9 and 27.4 hours, respectively. Finally, after two weeks, residual radioactivity was at the limit of detection, at about the limit of quantification or below the limit of quantification for edibles, none-edibles and the whole fish, respectively. Analysis of the extractable radioactivity present in edibles of fish at day 21 and 28 showed besides the parent molecule (M3) the presence of two minor, polar metabolites (M1 and M2) and one major, unpolar metabolite (M4). The amounts ranged for M1 and M2 from 0.05 to 0.19 mg/kg. The parent molecule amounted, on average, to 0.24 ppm. Metabolite M4, tentatively characterised as the methyl-derivative of the test material, ranged from 0.34 to 0.47 mg/kg.

Under the conditions of this study, it was found that the test material is not accumulated to a significant extent by fish and does not represent a hazard for aquatic food chains.

Description of key information

Under the conditions of this study, it was found that the test material is not accumulated to a significant extent by fish and does not represent a hazard for aquatic food chains.

Key value for chemical safety assessment

BCF (aquatic species):

3 dimensionless

Additional information

The bioaccumulation and elimination of the test material by Bluegill Sunfish was investigated in a dynamic flow-through system in accordance with EPA Guidelines 540/9-82-024 and in compliance with GLP. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The fish were continuously exposed to a mean concentration of test material of about 1.0 mg/L of tap water for 28 days at 20 +/- 0.5 °C. Thereafter, the fish were transferred to flowing, untreated water for 14 days and the elimination of radioactivity followed. Based on the average amount of radioactivity in the water and the residual radioactivity found in edibles, non-edibles and in the whole fish, bioaccumulation factors of 1.2, 5.5 and 3.0 were determined, respectively. Elimination of radioactivity from edibles, non-edibles and the whole fish was found to be rapid at the beginning of the depuration phase with half-lives of 7.8, 37.9 and 27.4 hours, respectively. Finally, after two weeks, residual radioactivity was at the limit of detection, at about the limit of quantification or below the limit of quantification for edibles, none-edibles and the whole fish, respectively. Analysis of the extractable radioactivity present in edibles of fish at day 21 and 28 showed besides the parent molecule (M3) the presence of two minor, polar metabolites (M1 and M2) and one major, unpolar metabolite (M4). The amounts ranged for M1 and M2 from 0.05 to 0.19 mg/kg. The parent molecule amounted, on average, to 0.24 ppm. Metabolite M4, tentatively characterised as the methyl-derivative of the test material, ranged from 0.34 to 0.47 mg/kg.

Under the conditions of this study, it was found that the test material is not accumulated to a significant extent by fish and does not represent a hazard for aquatic food chains.