Teflubenzuron

Bioaccumulation: aquatic / sediment

Description of key information

In a flow-through bioconcentration study according a method similar to the US EPA Guideline 165-4, common carp (Cyprinus carpio) were exposed to 14C-labeled test item at nominal concentrations of 0.002 mg teflubenzuron/L. in water. The maximum BCF values obtained in this study during the uptake period was 300 for the nominal test item concentrations of 0.002 mg teflubenzuron/L.

Key value for chemical safety assessment

BCF (aquatic species):

300 dimensionless

Additional information

teflubenzuron = active substance = a.s.

Additional information

One fish bioaccumulation study with the test item according a method similar to the US EPA Guideline 165-4 is available. 

 

Key information

Yokohama Laboratory (1989): Teflubenzuron - Dynamic Accumulation Study - Uptake, Distribution, Metabo­lism and Elimination in Carp. Unpublished report, report No.: 6Y007, according to Draft Assessment Report (2007) according to Council Directive 91/414/EEC, crossreference: MCA 8.2.3/01

To evaluate the bioaccumulation potential of the test item a bioaccumulation test with aquatic exposure according to a method similar to the US EPA Guideline 165-4 was carried out. The bioconcentration test consisted of a 28 days uptake phase, followed by a 2 weeks depuration phase. Comparing the description of the test method used in this test with the OECD Guideline 305 does not reveal significant differences. A statistical analysis whether an uptake plateau was reached, was, however, not performed, but increase in whole body and parts of the fishes was only slow after an initial phase. Therefore calculating a BCF from the uptake rate is acceptable. Fish (Cyprinus carpio) were exposed to nominal test item concentrations of 0 (negative control) and 0.02 mg a.s./L. The stock solution was prepared using acetonitrile as a solvent. Thus, a solvent control (with water and 0.0002% acetonitrile) ran in parallel. One test vessel per treatment, with 88 fish per vessel for the control and treatment was used. Analysis of the test item concentration in test water was conducted twice a week during the uptake period of 28 days.

During uptake phase, 4 mL (n=2) of the control and treated water samples were collected at days 0, 0.17 (4 h), 1, 3, 7, 11, 14, 18, 21 and 28 for analysis of ¹⁴C-residue, and at days 0, 14 and 28, 1,000 mL of the control and treated water samples were collected for analysis of metabolites in water. During depuration phase, each 4 mL (n=2) of the control and treated water samples were taken at days 1, 3, 7, 10 and 14 for measurement of ¹⁴C-residues. The radioactivity was measured by liquid scintillation counting (LSC). During uptake phase, 4 fish of the test aquarium and 4 or 6 fish of the control aquarium were collected at days 0.17, 1, 3, 7, 14, 21 and 28 for measurement of ¹⁴C-residues in whole body (2 fish) and tissues or organs (2 or 4 fish). The fish samples were combusted and oxidised by an oxidiser and radioactivity were measured by LSC. The mean value of radioactivity in con­trol fish was used as background. Two fish were collected at days 1, 7, 14 and 28 for autoradiography. In addition, ten fish were collected at days 14 and 28 for metabolism study. The metabolites were identified by TLC analysis. During the depuration phase, six fish were collected at days 1, 3, 7 and 14 for measurement of ¹⁴C-residues in fish whole body (2 fish of test and control aquarium), tissues or organs (2 fish of test aquarium and 4 fish of control aquarium), and for autoradiography (2 fish of test aquarium).

Temperature, pH and dissolved oxygen concentration of water during 42 days test period were 25.0-25.3 °C, 7.4-7.7 and 6.7-7.9 mg/L, respectively. The mean value of ¹⁴C-residues in water during the uptake phase was 0.0017 ± 0.00021 mg/L (coefficient of variation: 13%). This value is used to calculate BCF values. The ¹⁴C-residues in whole fish increased rapidly during the first day and then increased slowly from days 1 to 28, apparently approaching steady state. The BCF after 28 days was 640 ± 120, based on total ¹⁴C-residue. Within the first 3 days during the depuration phase, 92% of uptake amount was eliminated. Then, the elimination rate was slowed and after 14 days 97% was eliminated. The elimination kinetic constant k was 0.85/d for the initial rapid phase (α) and 0.076/d for the longer phase (β). The biological half-lives (t_1/2) were 0.8 days for initial phase (α) and 9 days for longer phase (β).

Teflubenzuron in fish comprised 33-36% of ¹⁴C-residue. From result of analysis of parent compound in water and fish, the maximum BCF of teflubenzuron was calculated to be 300 at day 28 exposure.

During the evaluation of teflubenzuron according to Council Directive 91/414/EEC, the BCF of 300 was determined as key value for the risk assessment (please refer to the Draft Assessment Report for teflubenzuron prepared according to Council Directive 91/414/EEC, Volume 3 B.9 (AS), 2007).

 

Conclusion

Based on a fish bioaccumulation study according a method similar to the US EPA Guideline 165-4 and following a worst case approach the bioconcentration factor of the test item is determined to be BCF = 300.