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
PHOSMET
Explanation
Phosmet was reviewed in 1978 when a Temporary ADI and some MRLs were
recorded.
Negative results obtained in a rat study and in a primate teratology
bioassay did not fully remove concerns previously raised with regard
to a possible teratogenic potential of phosmet and the meeting
therefore requested additional teratology studies. This monograph
addendum considers the results of such additional studies together
with new data on the occurrence of residues following the use of
phosmet on Kiwi fruit in New Zealand.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
Special Study on Teratogenicity
Groups of Wistar rats (20 pregnant rats per group) were administered
phosmet during gestation at dose levels of 0 or 30 mg/kg body weight
on day 8 or day 12 of gestation. A different group of animals was
administered at dose levels of 0, 0.06, 1.5 and 30 mg/kg/day every
other day throughout pregnancy starting on day 1 and ending on day 17.
All rats were sacrificed on day 20 of gestation and examined for early
and late resorptions and live, dead and malformed pups.
Examination of pups for somatic and skeletal anomalies did not show
any effect as a result of administration of phosmet in either testing
regime. Under the conditions of this bioassay, phosmet did not induce
a teratogenic response in rats (Short, 1979).
COMMENTS
Phosmet was reviewed by the 1978 Joint Meeting (FAO/WHO, 1979) when it
was requested that additional teratology data be submitted to resolve
controversial results noted in one teratology bioassay. Additional
teratology data were made available, reviewed and found to be
negative. These data served to alleviate the concerns of the previous
meeting and allowed this meeting to allocate an ADI. The ADI was
based on no-effect levels in two mammalian species.
TOXICOLOGICAL EVALUATION
Level Causing No Significant Toxicological Effect in Animals
Rat: 40 ppm in the diet equivalent, to 2 mg/kg body weight
Dog: 75 ppm in the diet equivalent, to 1.9 mg/kg body weight
Estimate of Acceptable Daily Intake for Man
0 - 0.02 mg/kg body weight
USE PATTERN: Kiwi fruit
Kiwi fruit is now the second largest horticultural product exported
from New Zealand. The fruit is subject to attack by a number of pests
and diseases and to meet phytosanitary requirements of importing
countries, it is necessary to spray regularly. The insecticide is
used five times throughout the growing season, mid December, January,
February, March and early April using 2.53 kg/ha per application or a
maximum of 12.65 kg/ha in any one season. Kiwi fruit are picked in
May so that the time interval between the last spray and harvest is
not less than 21 days.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Official trials carried out over two seasons (1974-76) resulted in
residue levels ranging up to 17 mg/kg with more than half being about
10 mg/kg (Table 1). Residues of phosmet are mainly in the skin, which
is hairy, relatively unpalatable and is normally discarded.
Table 1.
Treatment Residue on whole
rate No. of commodity
kg a.i./ha applications mg/kg
1974/75 season 3.6 2 8
(duplicate
samples) 3.6 7 17 (small fruit)
12 (large fruit)
2.4 7 8
1975/76 season* 1.7 6 5
variety Haywood 3.7 6 10
variety Abbott 1.6 7 7
3.8 7 12
* Single samples at 21 days after last application.
EVIDENCE OF RESIDUES IN FOOD IN COMMERCE
Monitoring carried out on commercial crops at harvest yielded the
information given in Table 2.
Table 2.
No. of samples Residues mg/kg
Year (separate growers) Mean range
1975 20 3.8 0.3 - 10
1977 28 4.8 0.0 - 23
1978 9 2.2 0.0 - 9
NATIONAL LIMITS REPORTED TO THE MEETING
The meeting was informed that the following national limits have been
established:
Country mg/kg
Australia 15
New Zealand 15
USA 25
APPRAISAL
The status of residues resulting from the use of phosmet on kiwi fruit
was reassessed in the light of data from New Zealand. The meeting
recognized that the bulk of the residues are below 10 mg/kg and that
substantially all of the residues are in the skin which is not
consumed. However, some lots of kiwi fruit retain significantly
higher residues and are not covered by the MRL of 10 mg/kg recommended
in 1978. It was agreed that the MRL should be increased to 15 mg/kg.
RECOMMENDATION
The meeting recommended that the MRL be amended as follows:
Commodity MRL Preharvest interval on which
(mg/kg) recommendation is based
Kiwi fruit 15 21
REFERENCE
Short R. (1979) Unpublished Teratology Data from Mid-West Research
Institute submitted to WHO by the U.S. Environmental Protection
Agency.