CXLs are currently established at 0.7 mg/kg for the meat (fat) of cattle, goats and pigs and 0.02 mg/kg for milk. The 1993 JMPR reviewed residues resulting from the use of ear tags but not those from other uses on animals. Mainly because of the lack of animal transfer studies the 1993 JMPR recommended withdrawal of these CXLs, noting that data from veterinary uses were also desirable. The 1995 CCPR recommended retention of the limits pending the 1996 JMPR review of promised data on both transfer to animals and treatments against ectoparasites.
Animal feeding studies
The results of studies on cattle and poultry were available.
Cattle. Residues of diazinon, diazoxon (G-24576) and hydroxydiazinon (CGA-14128) were determined in the blood, milk and tissues of Holstein dairy cows dosed with technical diazinon after the evening milking for 28-30 consecutive days by gelatin capsule at rates equivalent to 40 ppm (IX), 120 ppm (3X) and 400 ppm (10X) in the diet (Selman, 1994a,b). Separate reports were provided of the analytical phase (Perez and Wetters, 1994) and the biological phase (Krautter, 1994) of the study, which was based on specified protocols (Selman, 1992a).
Three cows were dosed at each rate and one served as a control. The IX rate was based on worst-case estimates of residues of 10 mg/kg in bean forage and pea vines each fed at 50% of the diet, converted to a dry-weight basis (34.3 ppm dietary burden) and the dosing took into account the mean dry-weight food consumption by the test animals.
Blood was sampled just before slaughter and composite samples of morning and evening milk were taken from each cow before dosing and 1, 3, 7, 14, 21 and 27 days after the first dose. Liver, kidney, round muscle, tenderloin muscle, and perirenal and omental fat were taken within 18-24 hours after slaughter. All samples were handled and stored satisfactorily (-20°C storage). Storage was for 4-5 months before analysis. As noted earlier, information on storage stability has been provided only for diazinon per se and only in tissues, not in milk.
The analytical method used was AG-550A. Results were corrected for procedural recoveries but not for control values. The results of recovery experiments were corrected for control values and diazoxon and hydroxydiazinon were expressed as diazinon (factors of 1.052 and 0.950 respectively). At the 0.01 mg/kg fortification level the percentage recoveries were:
|
|
diazinon |
diazoxon |
hvdroxydiazinon |
|
Liver |
101 |
77 |
111 |
|
Kidney |
91 |
82 |
104 |
|
Muscle1 |
115 |
107 |
121 |
|
Fat1 |
109 |
106 |
113 |
|
Milk1 |
108 |
103 |
113 |
|
Blood |
96 |
35 |
102 |
1 mean recoveries
No residues of diazoxon or hydroxydiazinon were found in milk or any of the tissues at any interval or dosing level with the exception of hydroxydiazinon in omental and perirenal fat, which ranged from 0.01 to 0.06 mg/kg from the 10X dose. The residues of diazinon are shown in Table 7.
Table 7. Residues of diazinon in blood, milk and tissues from dosing diary cows with diazinon for 28-30 consecutive days at rates equivalent to 40, 120 and 400 ppm in the diet (Selman, 1994a,b).
|
Sample |
Diazinon, mg/kg, from equivalent of |
|||
|
40 ppm (IX) |
120 ppm (3X) |
400 ppm (10X) |
||
|
Liver |
<0.01 |
<0.01 |
<0.01 |
|
|
Kidney |
<0.01 |
<0.01 |
<0.01-0.01 |
|
|
Blood |
<0.01 |
<0.01 |
<0.01 |
|
|
Muscle, round |
<0.01 |
<0.01 |
<0.01-0.02 |
|
|
Muscle, tenderloin |
<0.01 |
<0.01 |
0.01-0.02 |
|
|
Fat, perirenal |
<0.02-0.03 (0.02) |
0.05-0.08 (0.06) |
0.15-0.58 (0.4) |
|
|
Fat, omental |
0.02-0.04 (0.03) |
0.07-0.1 (0.08) |
0.2-0.84 (0.6) |
|
|
Days
|
||||
|
Milk |
1 |
<0.01 |
<0.01 |
<0.01-0.05 (0.02) |
|
|
3 |
<0.01 |
<0.01 |
0.01-0.06 (0.04) |
|
|
7 |
<0.01 |
<0.01 |
0.02-0.08 (0.04) |
|
|
14 |
<0.01 |
<0.01 |
<0.01-0.06 (0.03) |
|
|
21 |
<0.01 |
<0.01-0.01 |
<0.01-0.03 (0.02) |
|
|
27 |
<0.01 |
<0.01 |
<0.01-0.03 (0.02) |
Poultry. A study on poultry described by Selman (1992b, 1993) was derived from supporting studies of the biological phase by March and Rezold (1992) and the analytical phase by Perez and Wetters (1992) in accordance with specified protocols (Selman, 1991).
White Leghorn hens (3 groups of five birds at each dose level) were dosed with technical grade diazinon by gelatin capsule at rates equivalent to 0, 0.5 (IX), 1.5 (3X) and 5 ppm (10X) for 28 consecutive days. Feed and water were ad libitum. Eggs were collected from all the birds at 0, 3, 7, 14, 21 and 28 days and the hens were killed after 28 days. Composite samples of breast and thigh muscle, skin and attached fat, peritoneal fat and liver were taken on the next day. Samples were transported in dry ice to the laboratory where they were stored at -20°C until analysis within approximately 5 months of sampling. The diazinon content of the capsules was confirmed by analysis.
The samples were analysed by AG-550A for diazinon, diazoxon (G-24576) and hydroxydiazinon (CGA-14128). Procedural recoveries at the 0.01 mg/kg fortification level were respectively 103, 103 and 99% (means) from eggs; 120, 126 and 123% from muscle; 95, 87, and 107% from skin with attached fat; 120, 81 and 117% from fat and 99, 63 and 89% from liver, with all controls 0.01 mg/kg. Sample chromatograms from fat and eggs fortified at 0.01 mg/kg suggest that although 0.01 mg/kg may be attainable, 0.02 mg/kg would be a practical limit of determination. Other sample chromatograms were from fortification levels of 0.1 mg/kg in muscle, 0.05 mg/kg in skin/fat, and 0.5 mg/kg in liver.
No residues (<0.01 mg/kg) of diazinon, diazoxon or hydroxydiazinon were found in any sample at any dose rate.
