DIAZINON JMPR 1975
At the 8th Session of the Codex Committee on Pesticide Residues a
request was made for a recommended maximum residue limit for diazinon
in milk and milk products: (ALINORM 76/24 para. 89).
Diazinon is used as a spray or dip for the control of lice and
ticks in cattle. It may also be used in dairy barns for the control of
flies and similar pests. It is also used on pasture and forage crops
for the control of a range of insect pests. When used as a spray on
cattle the concentration is 0.05 - 0.1% active ingredient.
RESIDUES RESULTING FROM SUPERVISED TRIALS
The results of investigations on the metabolic fate of diazinon
in mammals were summarized in the Report of the 1969 Joint Meeting
(FAO/WHO 1970). These show that when diazinon is fed to lactating
cows, even at concentrations as high as 1000 ppm in the ration, no
residues appear in milk, meat, or tissues other than fat. Even then,
the fat from the animals receiving 1000 mg/kg in their ration
contained only 0.2 mg/kg of diazinon.
New data were provided by Switzerland in response to the request
made by the Codex Committee on Pesticide Residues. Reports of
experiments carried out in 1971 (Ciba-Geigy 1971) contain the results
of residue analyses for diazinon and diazoxon in milk samples from
eight cows, which were sprayed four times at weekly intervals with
0.05 or 0.1% active ingredient. The milk was analysed daily after each
The results which are summarized in Table 1 show the residue
values to vary considerably from cow to cow and between treatments of
individual cows. The residue levels in milk from cows treated with
0.1% diazinon are somewhat higher than in milk from those treated with
0.05%. The maximum residue levels reported were 0.57 mg/kg and 0.39
mg/kg for the 0.1% and 0.05 a.i. treatments respectively and these
were found shortly after treatment. These residue levels decreased to
0.02 mg/kg or less within about 6 days of spraying.
Diazoxon was not detected in any samples of milk by methods
capable of determining 0.005 mg/kg.
Bourne and Arthus (1967) used 15 lactating cows in an experiment
to determine the presence or absence of diazinon in milk following
dermal application. Five cows were treated for 4 consecutive days with
2% diazinon dust at a rate of 60g per cow; 5 received diazinon applied
from a backrubber for 10 consecutive days and 5 were untreated. Milk
samples were analysed at 12 hours and 1, 3, 5, 10 and 15 days after
the initial application of diazinon.
The milk was analysed by the method of Margot and Stammbach
(1964) with a limit of determination of 0.05 mg/kg. Milk from 3 of the
cows treated with the diazinon dust and 2 of the cows treated by the
backrubber method contained detectable quantities of the insecticide
12 hours after treatment. The residues persisted in the milk from two
of the cows treated with the 2% dust for the first 24 hours after the
initial application. The amount only just exceeded the limit of
determination, the highest value reported being 0.135 mg/kg. Milk from
untreated cows gave a reaction which was calculated to be equivalent
to 0.04 mg/kg apparent diazinon.
Mathysse and Fisk (1968) measured the residue of diazinon and
other insecticides in cows' milk following treatment similar to those
used in ectoparasite and fly control. Their studies included the
measurement of residues in the milk of individual cows after topical
application. Very small amounts of short-lived residues were found in
milk after spraying cows with a large volume of 0.06% diazinon
suspension. Maximum apparent diazinon was 0.33 mg/kg 1 day after a
second spray treatment. By 7 days, apparent diazinon residues were the
same as in milk from untreated cows.
Much lower residues of diazinon in milk were found by Hastie
(1963) who reported 0.04 - 0.05 mg/kg 1 day after cows were sprayed
with 0.05 and 0.1% diazinon emulsion and less than 0.01 mg/kg within 2
Formica (1973) determined the residue of diazinon in the milk of
sheep following dipping in emulsions containing 0.04 and 0.02% active
ingredient. Using a GLC method capable of determining 0.01 mg/kg in
milk it was found that residues of diazinon decrease within 15 days
after dipping from 0.17 to less tho 0.01 mg/kg (when treated with
0.04% a.i.) or from 0.09 to less than 0.01 mg/kg (when dipped in 0.02%
Leschchev, et al, (1972) report trials in which two lactating
cows were sprayed with solutions containing 0.2% a.i. diazinon at the
rate of 3 litres/animal. Samples of milk taken after the first milking
after treatment were analysed by GLC methods. Peak concentrations were
reached after 6 hours (0.65 and 0.39 mg/kg from individual cows).
Three days after treatment the residue level had declined to
0.036 mg/kg. Four days after treatment the residue levels were below
the limit of determination (below 0.001 mg/kg). The levels were
greatly different between the two cows.
Bull and McDougall (1974) determined the level and fate of
diazinon residues in milk and milk products from a dairy herd sprayed
with 0.5% a.i. diazinon emulsion at the rate of 10 litres/animal. They
found that the maximum concentrations occurred in the first milking
after treatment and in bulked whole milk from the treated herd the
maximum concentration was 0.25 mg/kg. Residues in whole milk returned
to pre-treatment levels by the 4th milking. Cream and butter prepared
from the milk of the treated herd contained 2.4 mg/kg and 4.5 mg/kg
respectively at the first milking and declined to 0.3 mg/kg in butter
after the 4th milking. Only a trace of diazinon (less than 0.04 mg/kg)
was detected in skim milk made from the whole milk from the first
milking after treatment. The whole milk excreted by the herd contained
4% fat. Cream contained 59% fat and butter 81.6%. Skim milk contained
Results of the study by Bull and McDougall are summarized in
Tables 1 and 2.
FATE OF RESIDUES
Leschchev et al, (1972) showed that pasteurization (90°C for 15
minutes) had no effect in the level of diazinon in whole milk.
Pasteurization at 70°C for 30 minutes reduced the level by 17%.
Cooking (details not given) reduced the diazinon concentration by
53% and "acidification of milk" reduced the concentrations by 65%.
Bull and McDougall (1974) showed that all the diazinon in whole
milk is in the fat and that it all carries over into the butter. There
is an apparent loss owing to interference which produces artificially
high figures during the analysis of whole milk.
The data previously considered show that there is no reasonable
expectation that diazinon residues in animal feed will be transferred
to milk. New data received by the Meeting from spraying trials carried
out in USA, Switzerland, USSR and Australia revealed that significant
quantities of diazinon appear in milk following topical application.
The quantity excreted varied greatly from animal to animal and from
one treatment to the next on the same animal.
TABLE 1. ppm diazinon in milk, skim milk and butter of individual
cows treated with nucidol 20 at 0.05% w/v concentration
Skim Milk Butter
Milkings 151 233 238 248 249 Mean (Composite) (Composite)
Pretreatment 0.03 0.02 0.08
1st milking 0.31 0.25 0.21 0.13 0.19 0.22±0.08 0.03 5.2
2nd milking 0.14 0.05 0.05 0.03 0.04 0.06±0.03 0.02 1.7
3rd milking 0.08 0.06 0.05 0.06 0.04 0.06±0.02 ---- 0.84
4th milking 0.03 0.02 0.05 0.02 0.02 0.03±0.01 ---- 0.26
10th milking 0.02 0.02 0.05 0.02 0.01 0.02±0.02 ---- 0.05
TABLE 2. ppm diazinon in milk, skim milk, butter and cream from the
bulk storage vessel after treating the herd with nucidol 20
at 0.05% w/v concentration
Residue p.p.m. Diazinon
Bulkings Milk Milk Cream Butter
Pre-treatment 0.03 0.02 0.09 0.08
1st milking 0.25 0.04 2.4 4.5
1st & 2nd milkings 0.15 0.03 2.1 2.6
3rd milking 0.06 0.02 0.57 0.60
3rd & 4th milkings 0.04 0.02 0.26 0.30
It is apparent that if a herd was treated the level in the
blended milk would be much less than the maximum amount excreted by
one cow. In keeping with the recommendations for establishing maximum
residue levels in milk and milk products (FAO/WHO 1972a) it is
appropriate to establish the maximum residue limit in the knowledge
that milk from treated herds will be bulked, and blended with milk
from untreated cows before going into commercial channels.
It has been demonstrated that diazinon partitions principally
into the lipid fraction of animal tissues and it can be expected that
the bulk of the residue will be located in the milk Lit, the
concentration being greatly magnified by the preparation of butter.
The following maximum residue limit is additional to
recommendations made previously and is based on the measurement of the
Milk and Milk products (fat basis) - 0.5 mg/kg
Bourne, J.R., and Arthur B.W. (1967) Diazinon residues in milk of
dairy cows. J. Econ. Entom. 60 (2):402-405.
Bull, M.S. and McDougall, K. (1974) Determination of diazinon residues
in milk and milk products from lactating cows following treatment with
diazinon 20EC. Ciba-Geigy Australia Ltd. Report 74/4/440.
Formica, G. (1973) Residues in sheep milk after dipping animals in
diazinon. Ciba-Geigy Agrochemicals (Basle) Report RVA/32/73.
Hastie, B.A. (1963) Diazinon residues. Geigy (Australasia) Multilith.
July 1963, 17 pages.
Leschchev, V.V., Kan, P.T., and Talanov, C.A. (1972) Residues of
dursban and diazinon in cows milk. Veterinarija 1972 Vol. 10, 114-115
Margot, A., and Stammback, K. (1964) In Analytical Methods for
Pesticides and Food Additives, Ed. by Gunter Zweig, Academic Press NY.
Vol.II p. 109-124.
Mathysse, J.G., and Fisk, D. (1968) Residues of diazinon coumaphos,
Ciodrin, methoxychlor and rotenane in cows' milk from treatments
similar to those used for ectoparasite and fly control on dairy
cattle. J. Econ. Entom. 61 (2):1394-98.