Symclosene

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

A GLP study was performed to determine cyanuric acid residues in catfish and trout filets harvested at 1, 3, 7, 14, 28 and 42 days after a single oral dose of 20 mg/kg body weight.

GLP compliance:

yes

Radiolabelling:

no

Details on sampling:

Thawed fish filets were cut into small pieces, which were all blended with dry ice in a blender ⁄ homogenizer with pulsed action until contents were uniform and had the consistency of a fine powder. The homogenate was allowed to degas in the freezer overnight, and then was tightly sealed and stored (-80°C) until analysis. Fortified (25 and 50 ng ⁄ mL) and un-spiked (negative control) samples of tissue homogenate from store-bought filets of farm-raised catfish and rainbow trout were extracted and analyzed with each set of depletion study samples to ensure method performance criteria for cyanuric acid residue determination.

Test organisms (species):

other: Ictalurus punctatus and Oncorhynchus mykiss

Details on test organisms:

TEST ORGANISM
- Common name: Channel catfish and rainbow trout
- Source: Bought from commercial fish farms
- Length at termination: Catfish (n = 100) were 25.3 ± 1.7 cm and trout (n = 120) were 30.2 ± 4.2 cm
- Weight at termination: Catfish (n = 100) were 195.5 ± 40.0 g and trout (n = 120) were 408.3 ± 168.9 g
- Description of housing/holding area: Catfish were housed in 200-L flow-through glass aquaria. Trout were held in 1800 L round fiberglass tanks.
- Food type: Catfish were fed a commercially available extruded diet at 35% protein, 8% fat, and 5% fiber (Burris Aquaculture, Franklinton, LA, USA). Trout were fed a pelleted commercial diet at 40% protein, 14% fat, and 4% fiber (Rangen Inc. Buhl, ID, USA).
- Amount: Catfish at 1-2% bw/day, trout 1-4% bw/day.


ACCLIMATION
- Acclimation period: 1 month before use
- Acclimation conditions: The holding systems and experimental systems were supplied with the same source of freshwater

Route of exposure:

other: Gelatin capsules administered via intragastric feeding tubes

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Test temperature:

Catfish tank water: 24.3 ± 1.0°C. Trout water: 12.5 ± 1.1°C

pH:

Catfish tank water: 7.2 ± 0.2. Trout water: 7.0 ± 0.1

Dissolved oxygen:

Catfish tank water: 8.4 ± 1.3 ppm. Trout water: 9.3 ± 3.4 ppm

Details on test conditions:

TEST SYSTEM
- Test vessel: 60 L flow through glass aquaria
- No. of organisms per vessel: One fish/tank. A total of 8 fish were used for each withdrawal time: six fish for each of the three chemical treatments and two control fish.

Nominal and measured concentrations:

20 mg/kg bw cyanuric acid (nominal concentration). Actual mean dosages calculated on the basis of bw at necropsy were 21.9 ± 2.3 mg/kg for catfish and 20.6 ± 2.1 mg/kg for trout.

Reference substance (positive control):

no

Details on estimation of bioconcentration:

The mean residue levels of cyanuric acid from each treatment group for each sample day were used to calculate the tissue half-life (t 1/2) and elimination rate constant (Kel). Calculations were carried out by regression of the semi-logarithmic concentration vs. time data using PK functions for Microsoft Excel developed by Usansky et al (Department of Pharmacokinetics and Drug Metabolism, Allergan, Irvine, CA, USA).

Details on results:

The highest concentration of cyanuric acid, occurred on day 1 following administration, 0.68 mg⁄ kg in catfish (highest individual) or 0.46 mg/kg (mean of 6), 2.59 mg⁄ kg in trout (highest individual) or 0.86 mg/kg (mean of 6) with mean cyanuric acid concentrations declining rapidly during the first week. Other than one trout on day 1, no fish had cyanuric acid muscle residues greater than 2.5 mg⁄ kg at any time point.

Reported statistics:

Cyanuric acid residues in trout and catfish following the individual dose were only statistically significant from the control on day 1 (P-value < 0.001).

Table 1: Cyanuric acid residues in catfish filets (mg/kg) following single 20 mg/kg bw dose

Days	1	3	7	14	28
	0.68	0.03	0.00	0.00	0.00
	0.48	0.00	0.00	0.00	0.00
	0.46	0.00	0.00	0.00	0.00
	0.44	0.00	0.00	0.00	0.00
	0.37	0.00	0.00	0.00	0.00
	0.30	0.00	0.00	0.00	0.00
Mean	0.46	0.01	0.00	0.00	0.00
SD	0.13	0.01	0.00	0.00	0.00

Table 2: Cyanuric acid residues in trout filets (mg/kg) following single 20 mg/kg bw dose

Days	1	3	7	14	28
	2.59	0.14	0.01	0.00	0.00
	0.75	0.04	0.00	0.00	0.00
	0.68	0.03	0.00	0.00	0.00
	0.47	0.01	0.00	0.00	0.00
	0.41	0.00	0.00	0.00	0.00
	0.26	0.00	0.00	0.00	0.00
Mean	0.86	0.03	0.00	0.00	0.00
SD	0.87	0.05	0.00	0.00	0.00

Conclusions:

Cyanuric acid residues in all dosage groups on day 3 had decreased to a level similar to that of controls. The t1/2 for fish receiving only cyanuric acid was less than 1 day for either catfish or trout. Only 2 of 30 catfish receiving only cyanuric acid developed renal crystals (days 14 and 28)

Description of key information

The log kow of CYA is - 1.31 indicating no potential to bioaccumulate. In a study to determine cyanuric acid residues in catfish and trout following oral administration of 20 mg/kg cyanuric residues had decreased to a similar level to the controls by day 3. Cyanuric acid does not have any potential to bioaccumulate.  

Additional information

The Log Kow of cyanuric acid is ≤ 3. In a supporting study in catfish and trout (Reimschuessel et al 2009) cyanuric acid was administered as a single oral dose at 20 mg/kg bw. Cyanuric acid residues in all dosage groups on day 3 had decreased to a level similar to the controls. Cyanuric acid t1/2 was less than 1 day in catfish and between 1 and 2 days in trout. Cyanuric acid has no potential to bioaccumulate.