CARBARYL JMPR 1975
Explanation
At the Eighth Session of the Codex Committee on Pesticide
Residues some countries expressed the view that a limit of 100 mg/kg
for carbaryl residues in animal foodstuffs was unduly high. A request
was made for a limit for carbaryl in milk and milk products and advice
was sought whether the limit in meat was sufficiently high to take
into account residues in animal feedstuffs.
APPRAISAL
Carbaryl was fully evaluated by the Joint Meeting in 1965, 1966,
1967, 1968, 1969, 1970 and 1973. (FAO/WHO 1965b, 1967b, 1968b, 1970b,
1971b, 1974b).
Extensive information on the fate of carbaryl residues in
domestic animals has been provided in the monographs of the 1966, 1968
and 1973 Meetings. From these monographs it is obvious that many
separate investigations have verified that when carbaryl is included
in the ration of cows only about 0.2% of the amount of carbaryl
ingested is excreted in milk as carbaryl and metabolites. At least
seven separate metabolites have been identified in milk, most of them
water-soluble. Carbaryl itself represents only about 5% of the total
residue following continuous feeding at levels of 100 mg/kg in the
ration (equivalent to about 1.5 mg/kg bodyweight). Since it is very
unlikely that any dairy animal would ever consume as much as 100 mg of
unchanged carbaryl per kg of the entire ration every day, actual milk
residues would be negligibly small.
Since no method of analysis available is suitable for determining
all of the water-soluble metabolites that could occur in milk the only
alternative is to determine the amount of parent carbaryl,
notwithstanding that it constitutes one of the minor components. It is
considered that the other metabolites are lower in toxicity than the
parent compound. It is recommended that the maximum residue limit be
set at or about the limit of determination.
Radio-tracer studies have shown that when cows are fed the
equivalent of 100 mg/kg of carbaryl in their ration, residues of all
fragments do not exceed 1 mg/kg in kidney, 0.4 mg/kg in liver and 0.1
mg/kg in the muscle. Only about 3-17% of these residues is parent
carbaryl.
On the basis of other studies it appears that only 13-30% of the
meat residues are in a form that can be measured by present analytical
methods. The maximum residue limit was therefore recommended to be 0.2
mg/kg. In 1968 the Joint Meeting (FAO/WHO 1969) recommended a
temporary maximum residue limit of 1 mg/kg in meat of cattle, goats
and sheep based not only on feeding studies, but also on residue
studies following dipping in carbaryl suspensions for the control of
cattle ticks. These studies had revealed that a significant residue of
carbaryl remained in fat and other tissues after dipping. The residues
from feeding were much less. The use of carbaryl as a cattle dip has
declined following the development of carbaryl-resistant strains of
ticks and the Joint Meeting in 1973 decided that the higher maximum
residue limit was not necessary.
RECOMMENDATIONS
The maximum residue limit for carbaryl residues in meat of
cattle, sheep and goats (0.2 mg/kg) is confirmed as adequate to
regulate the residues arising from the feeding of forage or other
feedstuffs containing, in their green state, up to 100 mg of carbaryl
per kg of feed.
The following maximum residue limit is recommended for milk and
milk products:
milk and milk products 0.1 mg/kg*
* At or about limit of determination.