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
METHAMIDOPHOS
Explanation
This compound was evaluated in 1976. The 1979 CCPR decided to ask the
Meeting to re-evaluate the data because several delegations felt that
the recommended MRLS were higher than necessary. Comments on the
significance of methamidophos as a residue from acephate application
were also solicited. This specifically relates to whether the MRLs
for methamidophos would be exceeded from applications of acephate
considering that in several crops, acephate has higher MRLs than
methamidophos.
RESIDUES IN FOOD AND THEIR EVALUATION
The 1976 data on cauliflower, cucumber, eggplants and sugar beets are
summarized in Table 1. It is seen that there are enough grounds for
lowering the MRLS for these commodities.
In the case of alfalfa, soybeans and citrus fruit, the MRLs are
necessary to take account of methamidophos residues as a result of
acephate application since MRLS for acephate have been allocated for
these crops. The data in 1976 for acephate can be used as the basis in
this MRL.
Table 1. Residues from acephate and methamidophos application
(from FAO/WHO 1977)
Acephate (mg/kg) Methamidophos
Based on Based on
Commodity Residues1 MRL PHI Residues2 MRL PHI
(days) (days)
Cauliflower 2.3-4.4 5 14 0.5 2 14
Cucumbers - 0.03-0.3 1 7
Eggplants - 0.05-0.06 1 7
Sugarbeets n.d.-0.05 1 21 0.01(23) 21
n.d. (28)
1 Combined acephate and methamidophos residues;
2 No PHI recorded in 1976 but the values shown could be the basis
for the recommended MRLs.
From Table 1 the meeting was able to estimate the maximum residue
levels which are likely to occur when methamidophos was used in
practice and when the reported intervals between last application and
harvest were observed. Further, the 1976 data for acephate is
sufficient to estimate maximum residue levels for methamidophos which
could result from acephate application to alfalfa, citrus fruit and
soybeans. Additional data would be required if methamidophos are
applied on these crops.
RECOMMENDATIONS
The following new Maximum Residue Limits are recommended:
Commodity MRL Preharvest intervals
on which based
Alfalfa 2
Cauliflower 1 14
Citrus 0.5
Cucumber 0.5 3
Eggplant 0.1 14
Soybeans 0.05
Sugarbeets 0.03
FURTHER WORK OR EVALUATION
Desirable
1. Residue data on alfalfa, citrus and soybeans arising from the
application of methamidophos;
2. Information on use patterns from countries where methamidophos is
used;
3. Further information on the level and fate of residues during
cooking and processing of fruit and vegetables.