PESTICIDE RESIDUES IN FOOD - 1984
Sponsored jointly by FAO and WHO
EVALUATIONS 1984
The monographs
Data and recommendations of the joint meeting
of the FAO Panel of Experts on Pesticide Residues
in Food and the Environment and the
WHO Expert Group on Pesticide Residues
Rome, 24 September - 3 October 1984
Food and Agriculture Organization of the United Nations
Rome 1985
METHAMIDOPHOS
Explanation
Methamidophos was first evaluated by the 1976 JMPR 1/ at which
limits were established for a number of commodities. Additional or
revised limits were estimated in 1979 and 1981. On several occasions
the CCPR has requested that methamidophos should be considered
together with acephate, of which it is a metabolite. To date
information has not been sufficient to do that fully, although the
JMPR has taken their relationship into account as far as possible.
This meeting received additional residue data on methamidophos in
egg plants, which are reviewed below. This addendum should be read in
conjunction with that on acephate elsewhere in these evaluations.
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
Mexico
The meeting was informed by one manufacturer that Mexican uses on
egg plants call for a 0-day pre-harvest interval instead of the 14
days on which the current 0.1 mg/kg limit (1979 JMPR) is based. The
original 1 mg/kg estimated by the 1976 JMPR was based on a 7-day
pre-harvest interval. Other information on Mexican uses available to
the meeting indicates a 1-day interval for a 50% LM formulation and 14
days for a 50% EC formulation (Manual de Plaguicidas, 1981).
U.S.A.
Geographically restricted uses in the U.S.A. permit
1.1 kg a.i./ha (1 lb a.i./A) 0.75%SP with a 7-day pre-harvest
interval. The U.S. tolerance of 1 mg/kg is also designed to
accommodate Mexican uses of 150-600 g a.i. EC/ha (5.4 kg a.i./ha
total/season).
RESIDUES RESULTING FROM SUPERVISED TRIALS
The manufacturers have submitted additional residue data on egg
plants (Table 1) not previously reviewed by the JMPR (Chevron, 1984;
Bayer, 1984).
1/ See Annex 2 for FAO/WHO documentation
Table 1. Methamidophos residues on egg plants resulting from supervised field trials.
Application Residues,mg/kg
Country Year rate
no kg a.i./ha formulation 0 1 3 5 7 14 21 Reference
Mobay Repts.
Mexico 1972- 15 8x0.4-0.6 2% D 0.15 0.13 0.08 0.08 0.07 37305
73 2% dust
+ EC
1X 0.6EC
1972- 13 9x0.3-0.5 2% D 0.37 0.17 0.19 0.12 0.13 0.05
73 (includes + (0.68) 1 (0.31) - (0.35) (0.22) (0.24) (0.09) 37306
6 appl of EC
2% dust
+ 2
4x0.6EC Chevron
U.S.A.3 1978 3 1.1 4 spray 4769
(4 lb. 0.29
a.i./Gal) 0.30
1979 14 1.1 4 spray 1.9 0.04 0.05 0.03 4770
0.0 0.03 0.07 0.02
1980 10 1.1 4 spray 0.49 0.65 0.15 5142
1.1 0.45 0.12
1979 17 1.1 4 spray 0.23 0.11 0.02
0.38 0.11 0.04 4768
1 Values in parentheses are adjusted to maximum U.S. approved 1.1 kg a.i./ha rate.
2 Last 4 applications were EC
3 Residue data corrected for recovery.
The Mexican data do not strictly represent approved uses, since
dust applications are included with EC applications. In practice,
however, the data are indicative of likely residues from approved uses
since all of the last applications were with approved EC formulations.
At approved application rates up to 1.1 kg a.i./ha, maximum residues
were 0.65 and 0.15 mg/kg at 7- an 14-day intervals respectively,
1.9 mg/kg at 3 days and 0.37 mg/kg (0.68 mg/kg adjusted to maximum
U.S. application rates) on the day of last application.
Maximum residues of methamidophos in or on kiwi fruit resulting
from the use of acephate were 0.012 mg/kg.
EVIDENCE OF RESIDUES IN COMMERCE OR AT CONSUMPTION
The meeting had information that one 1979 shipment of egg plant
of 38 sampled exported to the U.S.A. had over-tolerance residues of
1.9 mg/kg (FDA Surveillance, 1980).
APPRAISAL
The meeting reviewed additional residue and good agricultural
practice information for the use of methamidophos on egg plant and
responded to requests of the CCPR to consider acephate and
methamidophos together. The meeting reaffirmed its approach to setting
separate limits for acephate and methamidophos and concluded that
current good agricultural practice information and residue data were
still insufficient to permit an effective reassessment of most
previously estimated limits.
It is noted in the review of acephate elsewhere in these
evaluations that methamidophos limits have been estimated for all
crops for which there are acceptable limits. In the case of animals,
levels of 0.01 mg/kg (limit of determination) were estimated for the
carcase meat and fat of cattle, goats and sheep, and for milk. These
were apparently based on the studies of methamidophos in the goat
reviewed by the 1976 JMPR. Data were also available to that meeting on
acephate and methamidophos residues from the simultaneous feeding of
acephate and methamidophos to goats and pigs. The 0.01 mg/kg limit for
methamidophos in cattle, goats, sheep and milk is probably adequate
for residues resulting from the use of acephate or methamidophos on
feed items for which there are proposed Codex TMRLs.
Studies are not adequate to support methamidophos limits in
poultry or eggs, although trace levels have been observed in the
muscle and eggs of poultry from high dose levels of acephate (1976
JMPR).
Residues data and good agricultural practice information on egg
plants provided to the present meeting indicate that the current
0.1 mg/kg limit would not be adequate to accommodate good agricultural
practices which include 7-day (and possibly shorter) pre-harvest
intervals instead of the 14 days on which the 0.1 mg/kg limit is
based. The 1976 evaluations show that even average residues on peppers
and tomatoes at a 7-day interval from similar application rates to
those approved on egg plant are 0.2 - 1.0 mg/kg and maxima are twice
as high. Even after two weeks, maximum tomato and pepper residues
exceed 1 mg/kg. These data can reasonably be used to supplement egg
plant data.
It is also noteworthy that residues found in commerce have
exceeded 1 mg/kg, although it is not known whether they resulted from
good agricultural practice.
Additional data on methamidophos residues resulting from the use
of acephate do not indicate any need to revise current methamidophos
limits on the commodities concerned. Acephate limits have been
estimated for tree tomatoes (tamarillos). Data were also available for
methamidophos residues resulting from the use of acephate on tree
tomatoes, and these allowed the meeting to estimate a maximum residue
level for methamidophos on this commodity.
RECOMMENDATIONS
The meeting examined residue data from supervised trials
reflecting established good agricultural practice and was able to
estimate residue levels likely to occur when methamidophos is used in
practice and when the reported interval between the last application
and harvest is observed. These estimates are recommended as TMRLs.
They refer only to methamidophos.
Interval between last
application and harvest
Commodity TMRL (mg/kg) (days) on which
recommendations are based
Egg plant 1 (previously 0.1) 7 (previously 14)
Tree tomato
(Tamarillos) * 0.01 14
REFERENCES
Bayer, Unpublished Reports made available to the
1984 1984 JMPR by Bayer AG
Chevron, Unpublished Reports made available to the 1984
1984 JMPR by Bayer AG
FDA Surveillance, Results of FDA Surveillance of Mexican Produce for
1980 Pesticide Residues (Compliance Programs 7305. 008
- Fiscal Year 1979), Bureau of Foods and Office of
the Associate Commissioner for Regulatory Affairs,
Food and Drug Administration, April 23, 1980.
Manual de Plaguicidas Autorizados En 1981 Cultros de Hortalizas Para
1981
See Also:
Toxicological Abbreviations
Methamidophos (HSG 79, 1993)
Methamidophos (ICSC)
Methamidophos (JMPR Evaluations 2002 Part II Toxicological)
Methamidophos (Pesticide residues in food: 1976 evaluations)
Methamidophos (Pesticide residues in food: 1979 evaluations)
Methamidophos (Pesticide residues in food: 1981 evaluations)
Methamidophos (Pesticide residues in food: 1982 evaluations)
Methamidophos (Pesticide residues in food: 1985 evaluations Part II Toxicology)
Methamidophos (Pesticide residues in food: 1990 evaluations Toxicology)