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
FENITROTHION
Explanation
Fenitrothion was evaluated in 1969, 1974, 1976 and 1977.
At its 11th Session, the CCPR requested the meeting to provide a
recommendation for bran (processed) on the basis of new data known to
be available: also for clarification of proposals for MRLs in pears
and peaches as indicated in paragraphs 107 and 108 of ALINORM 79/24.
Further data on the use and fate of fenitrothion was also made
available to the meeting by Australia.
RESIDUES IN FOOD AND THEIR EVALUATION
RESIDUES RESULTING FROM SUPERVISED TRIALS
Pre-harvest
Having examined the raw data from which a selection was made for
presentation in Table 6 of the 1974 monograph, the meeting agreed that
although the residues in pears appeared to be somewhat lower than
those in apples in the trials carried out in Japan, the differences
were small and probably not representative of the true picture
world-wide. It was agreed that the MRL for pears should be brought
into line with that for apples.
The meeting re-examined the raw data from 12 trials carried out on
peaches in Japan and which provide the basis for the information
contained in Table 6 of the 1974 monograph. The original data were
developed by analysis made separately on pulp and peel as is the
custom in Japan. The ratio of the weight of pulp to peel averaged
90:10 (range 92/8-85/15). Recalculation of the residue level on the
whole fruit indicated that the bulk of the values fall below 1 mg/kg.
Residues in Bran
In 1974 and 1976 the meeting reviewed the use of fenitrothion for the
protection of raw grain against stored-product pests. Among the
information reviewed were studies on the fate of fenitrothion residue,
on grain subjected to milling and processing. These data (FAO/WHO
1975b page 266, 1977b page 369) showed that the bulk of the
insecticide deposited on the grain remains in the epidermis and is
removed from the bran during milling.
Further studies by Desmarchelier (1979) with fenitrothion and eleven
other grain protectant insecticides, showed that the concentration on
the bran is from 2 to 3.2 times the concentration on the whole wheat.
Except for bioresmethrin and pirimiphosmethyl, where the concentration
is 3.2 and 2.9 times that on raw grain respectively, all of the other
insecticides tests including fenitrothion residue level all show a
concentrating effect from 2 to 2.7 by comparison with the whole wheat.
This figure depends to a small extent on the original rate of
application of the insecticide and the time in storage prior to
milling. Generally the amount of insecticide in the flour is 10% or
less of the concentration on the whole wheat.
Desmarchelier (1979) extended his studies to determine the percentage
loss of residues during processing of bran using a laboratory
technique to simulate the least severe industrial process. This
consisted of heating the moistened bran for two hours at 90°C. He
showed that 42% of the fenitrothion was lost from raw bran by such
treatment. With some other insecticides the loss was a high at 96%.
None of the insecticides was less subject to degradation than
fenitrothion.
Murray and Snelson (1978) studied the distribution of fenitrothion and
bioresmethrin residues on mill fractions from wheat processed through
a commercial flour mill. The results of their investigations are set
out in Table 1. These show that the bran from all milling streams
when blended together, contained fenitrothion residues 1.5 times as
high as those present in raw wheat received into the mill. Snelson
(1979) also reports the results of monitoring 13 flour mills
processing wheat containing from 5 to 10 mg/kg of fenitrothion. The
results, given in Table 2, indicate that 100% of the bran samples
contained less than 20 mg/kg but up to 90% contained up to 15 mg/kg.
Only 23% of the bran samples contained less than 10 mg/kg. These
results are contrasted with the residues found in processed bran.
There is no wheat available in Australia without residues of grain
protestant insecticides. It was concluded that processed bran
available retail would reflect the effect of processing on the
residues present in raw bran. A survey was conducted in Australia
(Snelson 1979) in which 36 samples of processed bran representing 12
different commercial products available in retail stores of three
cities, located over a distance of 2,000 kilometres were analysed. In
spite of the fact that all raw bran available for processing contained
fenitrothion to a limit of 20 mg/kg, it was found that 80% of the
processed bran available in the form of breakfast cereals contained
less than 1 mg/kg of fenitrothion residue. 8% of the samples
contained more than 3 mg/kg but these (3) represented products which
were only partially processed. 36% of the samples contained no
detectable residues (less than 0.1 mg/kg) of fenitrothion.
In the light of the results of the above survey, a supervised trial
was carried out in a factory processing three bran products. The
results of the trial are shown in Table 3. These indicate that
substantially all of the fenitrothion residues are destroyed in the
cooking process which involves prolonged heating under pressure with
live steam after the bran has been subjected to wet digestion with
malt. The subsequent drying, extrusion, drying and toasting are all
vigorous processes employing high temperatures that would be expected
to destroy any residues which were not destroyed during the cooking.
The trial confirmed that normal commercial processing destroyed the
bulk of the residues.
Table 1. Residues of Fenitrothion, Mg/kg, in Wheat Milling Fractions (and of Bioresmethrin)
Sample No. Treated with 12 mg/kg Treated at harvest
and fenitrothion (plus 1 mg/kg with 12 mg/kg
Description syngergized bioresmethrin) fenitrothion
Laboratory A Laboratory B Laboratory A
1. Wheat before point
of pesticide application <0.5 - N.A.
2. Wheat when received
into the mill 8 7 (0.7) 7
3. Wheat at first break roll
before it enters the rolls 4 4 (0.6) 3
4. Crushed wheat at first
break roll after it drops 5 4 (0.6) 3
from the rolls
5. Flour sieved from the
sitter fed from first 1 0.8 (<0.05) 1
break roll (clean stream)
6. Flour sieved from the
sitter fed by the last
break roll (dirty stream) 4 3 (0.1) 2
7. Flour sieved from the
sitter fed by the first
reduction roll (clean stream) 0.5 0.6 (<0.05) 0.5
8. Flour sieved from the
sitter fed by the last
reduction roll (dirty stream) 5 5 (0.3) 4
Table 1. Continued...
Sample No. Treated with 12 mg/kg Treated at harvest
and fenitrothion (plus 1 mg/kg with 12 mg/kg
Description syngergized bioresmethrin) fenitrothion
Laboratory A Laboratory B Laboratory A
9. Flour from all streams,
being fed into bulk flour
bins or into packers 2 2 (0.1) 1
10. pollard from all streams
before it is mixed with
the bran 6 8 (0.7) 7
11. Bran from all streams
before it is mixed with the
pollard 12 11 (1) 11
12. Wheat germ 10 10 (2) 7
Figures in ( ) are for bioresmethrin.
Table 2. Fenitrothion Residues on Raw and Processed Bran
(Results from Australian Survey)
Raw Bran Processed Bran
Range of No. % Range of No. %
Residues Residues
<10 3 23 <0.1 13 36
10-12 5 38 0-1-0.5 7 19
12-14 1 8 6.5-1.0 9 25
14-16 3 23 1.0-2.0 3 8
16-18 0 0 2.0-3.0 1 3
18-20 1 8 >3.0** 3 8
13 100 36** 100
* Maximum 4.0
** 12 different brands.
Table 3. Effect of Commercial Processing on Fenitrothion
Residues on Bran
Processing Stage Product A Product B Product C
Rep.
1 2 1 2 1 2
1. Raw bran before cooking 5 4 3 4 23 21
2. Cooked bran taken
directly from cookers <0.05 <0.05 <0.05 <0.05 2 2
3. Bran taken after initial
drying stage <0.05 <0.05 <0.05 <0.05 1 2
4. Finished product taken
after bran has been formed
into final shape and dried/
toasted through an oven 1 <0.05 <0.05 <0.05 1 1
Tempone (1979) has shown that fenitrothion and other grain protectant
insecticides are destroyed during the melting process when grain
protectant insecticide residues are present on the raw barley. These
investigations have been verified by extensive surveys in which malt
from more than 30 maltsters has been monitored for fenitrothion and
other insecticide residues. It was already known that all of the
barley available for melting contained either malathion or
fenitrothion residues at levels up to the maximum residue limits (8
and 10 mg/kg respectively). None of the 36 samples examined contained
fenitrothion residues at or above the limit of reporting (0.1 mg/kg).
(Snelson, 1979). It is apparent therefore, that the melting process
effectively destroys a variety of insecticide residues and no doubt
the enzymes of malt which is added to the process to improve the
palatability and flavour of the bran, could contribute to the
destruction of fenitrothion prior to and during the cooking of raw
bran.
Residues in Flour
Snelson (1979) observed that commercial flour mills could not comply
with the national residue limit for fenitrothion in flour (1 mg/kg)
particularly when wheat available had been treated within the previous
two to three months with fenitrothion at the recommended level of 6
mg/kg. The matter was investigated by Murray and Snelson (1978) and
the results, summarised in Table 1, indicate that although the flour
sieved from the sifter fed by the first reduction rolls contains
residues of the order of 0.5 mg/kg, this is later blended with flour
from other streams containing slightly higher residues of fenitrothion
due to the higher degree of extraction which occurs in these steps.
As a consequence, the commercial flour contained 2 mg/kg of
fenitrothion.
All of the data examined by the meeting in 1974 and 1976 came from
experimental milling equipment which, although designed to reproduce
commercial practice, does not give the same high degree of extraction.
In view of the extensive commercial experience which shows that
commercial flour mills cannot comply with the maximum residue limit of
1 mg/kg, the meeting recommended that the maximum residue limit in
flour be raised to 3 mg/kg.
Desmarchelier (1979a) and Desmarchelier and Marsden (1979) thoroughly
investigated the transfer of fenitrothion residues from wheat via
flour into wheat gluten and the fate of these residues during the
cooking of many varieties of bread prepared from different recipes.
They showed that although gluten represents approximately 10% of the
content of raw grain, the residue in the extracted gluten is about 30%
of that present in the raw grain, thus representing a threefold
concentration above the expected level. This picture is not unique to
fenitrothion, but appears to occur with many insecticides of quite
different chemical groups.
These investigations showed that irrespective of the level of residues
in the flour or in gluten and independent of the type of bread, the
recipe or the baking process, approximately 50% of the residue was
destroyed in the process.
Likewise, the processing of oats for the production of rolled oats,
involving as it does the removal of the hulls and the heating of the
kernel to produce groats, in the removal and destruction of
substantially all the insecticide deposited on the grain for
protection against stored product pests. Fenitrothion is removed in
this operation to an extent exceeding 95% (Desmarchelier, 1979).
APPRAISAL
New information has been made available concerning the level and fate
of fenitrothion residues on bran and other foods processed from raw
cereals. The meeting recognised that when fenitrothion was used to
protect grain from stored product pests the bulk of the insecticide is
deposited on the epidermis and is removed on the bran during the
milling process. The concentration on the bran is from 2 to 2.5 times
that on the whole wheat.
Although some raw, unprocessed bran is marketed for direct consumption
or for culinary purposes, the bulk of the bran used for human
consumption is first subjected to processes designed to improve the
flavour and palatability. These processes subject raw bran to
vigorous physical and chemical processes which destroy substantially
all of the fenitrothion residues present. The available data indicate
that a maximum residue could be established at a lower level on
processed bran to assist food processors and food control officials in
their monitoring activities.
It has been shown that the malting process destroys substantially all
of the fenitrothion present on the raw barley. Likewise the removal
of the hulls from raw oats and the process involved in converting the
hulled oats into groats and rolled oats destroys substantially more
than 95% of the residues present on the raw oats.
The meeting has reviewed the data on fenitrothion residues on peaches
and pears and agrees there is justification for amending the
recommendations previously made.
RECOMMENDATION
The following additional maximum residue limits are recommended:
Wheat bran (processed) 2 mg/kg.
The maximum residue limits previously proposed are amended as follows:
Wheat bran to read wheat bran (raw) 20
Pears 0.5 mg/kg
Peaches 1 mg/kg
Wheat flour (white) 3 mg/kg
REFERENCES
Desmarchelier, J.M. - The effect of milling and processing on the
level and fate of grain protectant insecticide residues on wheat and
oats. Report of CSIRO Division of Entomology, Canberra, Australia, May
1979.
Transfer of grain protectant insecticide residues from grain to
wheat gluten. Report of CSIRO Division of Entomology, Canberra,
Australia, June 1979.
Desmarchelier, J.M. and Marsden, P. - Effect of baking on fenitrothion
residues in wheat gluten. Report of CSIRO Division of Entomology,
Canberra, Australia, May 1979.
Murray, D. and Snelson, J.T. - Fenitrothion and bioresmethrin residues
in milled products from a commercial flour mill. Report to Department
of Primary Industry, Canberra, June 1978.
Snelson. J.T. Pesticide Residue Survey, Department of Primary
Industry, Canberra, July 1979.
The effect of processing on fenitrothion residues on raw bran.
Report to Department of Primary Industry, Canberra, October 1979.
Tempone, M.J. Studies on the effects of insecticides on barley
malting, Government of Victoria. Research Project Series No. 50,
January, 1979.
See Also:
Toxicological Abbreviations
Fenitrothion (EHC 133, 1992)
Fenitrothion (HSG 65, 1991)
Fenitrothion (ICSC)
Fenitrothion (FAO/PL:1969/M/17/1)
Fenitrothion (WHO Pesticide Residues Series 4)
Fenitrothion (Pesticide residues in food: 1976 evaluations)
Fenitrothion (Pesticide residues in food: 1977 evaluations)
Fenitrothion (Pesticide residues in food: 1982 evaluations)
Fenitrothion (Pesticide residues in food: 1983 evaluations)
Fenitrothion (Pesticide residues in food: 1984 evaluations)
Fenitrothion (Pesticide residues in food: 1986 evaluations Part II Toxicology)
Fenitrothion (Pesticide residues in food: 1988 evaluations Part II Toxicology)
Fenitrothion (JMPR Evaluations 2000 Part II Toxicological)