PESTICIDE RESIDUES IN FOOD - 1979
Sponsored jointly by FAO and WHO
EVALUATIONS 1979
Joint meeting of the
FAO Panel of Experts on Pesticide Residues
in Food and the Environment
and the
WHO Expert Group on Pesticide Residues
Geneva, 3-12 December 1979
PIRIMICARB
Explanation
Pirimicarb was evaluated at the 1976 and 1978 Meetings when MRLs were
recommended for an extensive list, predominantly of fruit and
vegetables, and a temporary ADI was established. The only outstanding
queries related to the need for a carcinogenic study, to be completed
in time for the 1980 Meeting.
At the 11th Session of the CCPR, a suggestion was made that the MRL of
0.5 mg/kg for "beans with pod", which was proposed by the 1976
Meeting, should be increased to 1 mg/kg. Information on the use of
pirimicarb on beans together with the results of supervised trials
supporting an increase in the MRL is reviewed in the present monograph
addendum.
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
Pirimicarb is normally effective at rates of 125-250 g/ha, depending
upon the circumstances. The higher rate will tend to be needed under
the conditions of heaviest aphid infestation or to kill some species.
At the time of the 1976 Meeting, a preharvest interval (PHI) of 7 days
was typical for crops such as dwarf or runner beans. The 1976 Meeting
proposed the limit of 0.5 mg/kg for "beans in pod", notwithstanding
the existence of an occasional value up to 0.55 mg/kg 7-8 days after
spraying at 250 g/ha.
Since 1976, there has been a trend towards a shorter PHI and, for
example, a 3-day PHI has been cleared on this crop in the United
Kingdom. In many respects, this is most appropriate to the behaviour
of residues of the compound, since these have been shown to decline
rapidly during the first 2-3 days after spraying (volatilization being
an important means of loss) and then more slowly.
RESIDUES RESULTING FROM SUPERVISED TRIALS
The available data for the 250 g/ha rate and a 3-day PHI, provides
justification for increasing the MRL to 1 mg/kg.
Manley (1972) in a summary of information on pirimicarb residues in
crops, points out that trials carried with the 50% dispersable powder
and the 5% emulsifiable concentrate formulations applied to French
beans using a hand lance and boom sprayer indicated that residues
following application by boom sprayer were considerably less than
those following application by lance. However, later results did not
endorse this pattern, and some other cause must be responsible for the
variations in residue levels.
Table 1. Pirimicarb Residues in French Beans - Summary of Results
from U.K. 1968-71
No. of samples
Application Days between analysed with Total carbamate
rate application residues residues (ppm)
g a.i./l and harvest >0.06 <0.06 Range Mean
ppm ppm
0.25 0 3 2 <0.06-0.95 0.44
4 6 7 <0.06-0.63 0.23
7-8 6 4 <0.06-0.55 0.24
13-14 11 1 <0.06-0.57 0.30
0.50 0 3 0 0.89-1.4 1.1
4 9 4 <0.06-0.95 0.39
7-8 7 4 <0.06-0.67 0.30
13-14 11 1 <0.06-0.69 0.40
Table 2. Pirimicarb Residues in Runner Beans - Summary of results from
Germany 1973/75
Application Interval No. of samples Total carbamate
rate between analysed with residues
(kg ai/ha) application residues (ppm)
and harvest >0.01 <0.01 Range Mean
(days) ppm ppm
0.3 0 1 0 0.74
1 1 0 0.18
2 1 0 0.18
3 1 0 (1.3)*
4 1 0 0.07
7 1 0 0.05
10 1 0 0.01
0.5 0 3 0 0.03-0.18 0.12
1 3 0 0.07-0.15 0.12
3 3 0 0.06-0.10 0.08
5 3 0 0.03-0.07 0.06
7 3 0 0.02-0.06 0.05
10 2 0 0.01-0.05 0.03
* Suspect result
The results obtained in a number of trials over the period 1968-71 are
summarized in Table 1. Total carbamate residues declined rapidly
during the first few days after spraying and then more slowly. This
is consistent with the pattern already seen on other vegetables
(FAO/WHO 1977b).
Edwards and Dick (1976) in a summary of reports of residue trials in
crops during 1973/75, record that in four trials in Germany pirimicarb
was sprayed on beans at the rate of 0.3-0.5 kg/ha and 600-1000 L/ha.
The results are summarised in Table 2. Examination of the three
trials where pirimicarb was applied at the rate of 0.5 kg/ha showed
lower initial residues to be present (0.12 mg/kg at 0 days). These
residues degraded slowly to 0.03 mg/kg at 10 days. A single trial
where pirimicarb was applied at the rate of 0.3 kg/ha gave a higher
initial residue of 0.74 mg/kg which degraded more rapidly to 0.01
mg/kg at 10 days.
The samples from the German trials were analysed by a
gas-chromatographic procedure with a limit of determination of 0.01
mg/kg.
APPRAISAL
At the request of the 11th Session of the Codex Committee on Pesticide
Residues the meeting re-evaluated pirimicarb residues on "beans with
pod" in the light of data from the 1976 Monographs and detailed
reports from the manufacturers. In the light of amended use patterns
which involve a shorter pre-harvest interval, the meeting agreed that
the MRL should be raised from 0.5 to 1 mg/kg.
RECOMMENDATION
The recommended maximum residue limits for pirimicarb should be
amended as follows:
Commodity Temporary maximum Pre-harvest interval on
residue limit which the recommendation
(mg/kg) was based
Beans (with pod) 1 3 days
REFERENCES
Edwards, M.J. and Dick, J.P. - Pirimicarb Residue Summary: Residues in
crops from Field Trials during 1973-75". ICI Plant Protection
Division Report No. TMJ1360B (1976), Unpublished.
Manley, C.A. - Residue Summary: Pirimicarb in Crops". ICI Plant
Protection Limited Report No. TMJ585/2 (1972), unpublished.