FENTHION JMPR 1977
Explanation
Fenthion was evaluated in 1971 (FAO/WHO 1972) and in 1975 (FA0/WHO
1976) and a temporary acceptable daily intake was estimated to be
0.0005 mg/kg bw. Temporary maximum residue limits were recommended for
a range of fruits, vegetables, grain and foods of animal origin. It
was indicated that certain specific toxicological information was
required before the acceptable daily intake and maximum residue limits
could be confirmed. Residue data from supervised trials on other
citrus fruits (especially lemons), coffee, cucurbits, onions and
potatoes and additional residue data on sugar beet roots and tops were
also required.
In 1977 the 9th Session of the Codex Committee on Pesticide Residues
requested the Joint Meeting to review maximum residue limits in the
light of information provided by governments and other relevant
information such as disappearance rate.
The results of a considerable number of supervised residue studies
were provided by the principal manufacturer (Bayer, 1977). Information
was also received from Poland, the Philipines, Turkey, the USA and
from the scientific literature in part fulfillment of the above
requirements, and the following monograph addendum reflects the
evaluation of this information. No new toxicological data were made
available in sufficient time for consideration.
RESIDUES IN FOOD AND OTHER EVALUATION
RESIDUES RESULTING FROM SUPERVISED TRIALS
The results of studies carried out on alfalfa, apples, bananas, beans,
cherries, grapes, grass, olives, onions, oranges, peaches, pears,
plums, potatoes, sweet potatoes, rice., strawberries and tomatoes are
summarized in Table 1.
These data represent the results of a large number of separate trials
(average of 3 for each pre-harvest interval). The results indicate
that the recommended maximum residue limits for fenthion residues in
apples, cherries, grapes, olives, peaches and rice are appropriate,
being neither too high nor too low to accommodate the maximum values
reported.
Bananas
The use of fenthion as a post-harvest dip to control fruit flies in
bananas and other tropical fruits is important in order to be able to
comply with the phytosanitary requirements of many importing
countries. The studies in the Philippines (Magallona, 1977) indicate
that such treatment results in the bulk of the residue being retained
in the peel (1-2 mg/kg) with 0.3-0.5 mg/kg occurring in the pulp
(peeled fruit).
Citrus
In the case of oranges it is obvious that residues in excess of the
recommended maximum residue level can occur even 50-60 days after the
application of normal rates of fenthion. Table 1 gives details of
studies made in Japan in 1972. (Bayer, 1977) which indicate that the
following the spraying of orange trees with fenthion at the rate of
2.7 - 3kg/ha, the residue in the whole fruit is of the order of 1
mg/kg when harvested 50/60 days later. Of this residue about 0.05-0.15
mg/kg is in the juice and 1.0-5.8 mg/kg in the peel. Reference to the
1971 monograph (FAO/WHO 1972) reveals that the previous recommendation
is based on studies where fenthion was applied at the much lower rate
of 300 g/ha.
Studies made in Turkey in 1967-1969 (Kirca, 1976) on oranges and
tangerines show that the application of fenthion/sugar bait to
tangerines for the control of fruit fly produces residues in the whole
fruit ranging from 0.25-4 mg/kg 7-10 days after the last application
and up to 2 mg/kg 21 days after treatment. (See Table 1.) Because the
maximum residue limit recommended by the Joint Meeting did not
accommodate these residues, the use of fenthion was not accepted in
Turkey for the control of fruit fly. Fenthion is widely used on citrus
against fruit fly and consideration must be given to the establishment
of a maximum residue limit appropriate for these needs.
Olives
Extensive studies in Turkey between 1963 and 1975 (Kirca, 1976) show
that olives treated for the control of live fruit fly and
Mediterranean fruit fly take up considerable amounts of fenthion which
dissipate slowly. Only by careful control of the application rate and
by strict observance of a 30-day pre-harvest interval is it possible
to comply with the currently recommended limit of 2 mg/kg in harvested
olives.
Pears and plums
Residue studies on pears (Bayer, 1977) and on plums (Glogowski et al.,
1974) provide a basis for proposing maximum residue limits on these
fruits (See Table 1.)
Potatoes
Data were available from Japan (Bayer, 1977) from 5 trials in
different regions of the country where fenthion spray applied three
times at a concentration of 0.05% and at the rate of 1200-20001ha
with the last spray 15 days and 30 days prior to the harvest. None of
the tubers harvested were found to contain residues when examined by
methods sensitive to 0.001 mg/kg.
In the light of the data summarized in Table 1, it is possible to
propose revised or additional maximum residue limits for fenthion in
bananas, beans, citrus, onions, pears, plums, potatoes, sweet
TABLE 1. Residues of penthion resulting from supervised trials
Application Residues (mg/kg) at intervals (days) after application
rate
Crop Country Year no kg ai./ha formulation 0/1 3 7 14 21 28 35
Alfalfa Turkey 1970 1 0.75 Dust 0.1 0.25
U.S.A. 1976 1 0.11 SC 3.58 0.65
Apples Germany 1971 1 0-7-1.4g/ EC 0.75-0.9 0.5-0.7 0.15-0.25 0.15-0.2 0.05-0.1
tree
(Renette) Poland 1969 1 0.5 EC 5.32 1.94 1.2 0.11 0.08 0.03 Trace
(Starking) Poland 1969 1 0.5 EC 8.2 3.07 1.06 0.11 0.06 0.03 Trace
(Jonathan) Poland 1970 1 1.1-1.25 EC 10.06 4.12 2.73 1.55 0.40 0.20 0.16
(Starking) Poland 1970 1 1-1-1.25 EC 15.11 2.65 1.66 0.41 0.35 trace ---
Bananas Phillipines 1977 1 0.04% EC 1.2
(peel) Phillipines 1 0.05% EC 1.2
post-harvest Phillipines 1 0.075% EC 1.3
(pulp) Phillipines 1 0.04% EC 0.3
post-harvest Phillipines 1 0.05% EC 0.5
Phillipines 1 0.075% EC 0.9
Beans Japan 1972 5 0.5 EC nd nd nd
Cherries Germany 1971 1 1.4g/tree EC 0.8-0.9 0.55-0.7 0.3-0.45 0.05-0.1
1 1.4g/tree EC 0.7-6.7 0.4-0.8 0.1-1.95 nd -0.3
Poland 1970 1 11.3g/tree EC 19.15 6.14 3.58 1.32 0.35 0.24 trace
1971 1 11.3g/tree EC 19.0 12.54 6.45 2.03 0.70
Grapes Japan 1972 2 0.07-1.5 EC 1-1.24 0.35-0.4 nd-0.29 nd nd
Grass U.S.A. 1976 10 0.11 SC 1.12-1.86
Turkey 1974 1 4 oil 46 5.9
Olives Turkey 1963 1 0.075 EC 5.1 3.1 0.97
1964 1 6:75g/tree EC 2.7 2.0 3.1
1975 1 7.5g/tree EC 6.5 1.7 trace
Turkey 1965 1 14 g/tree EC 4.04 1.94 0.56 0.4
1965 2 0.075% EC 6.5 3.2 1.0
TABLE 1. (Continued)
Application Residues (mg/kg) at intervals (days) after application
rate
Crop Country Year no kg ai./ha formulation 0/1 3 7 14 21 28 35
Onions Japan 1970 1 0.5-1.0 EC nd-0.08 nd-0.06 nd-0.03
Oranges
(flesh) Japan 1972 2 2-7-3.0 EC nd-0.02
(peel) 2 2.7-3.0 EC 1.0-5.8
(juice) 2 2.7-3.0 EC 0.06-0.14
Oranges Turkey 1969 3 1% bait 0.87 0.57
1969 6 1% bait 1.73
Peaches Japan 1969 6 0.35-1.6 WP 0.03-1.2 0.03-1.0 0.06-0.5
Pears Japan 1969 5 1.0 -2.8 WP 0.004-1.4 nd-0.9 0.15-0.18
Plums Poland 1969 1 0.075% EC 7.11 2.82 0.85 0.2 0.11 0.06
1970 1 0.075% EC 10.85 9.45 3.72 0.8 0.6 0.5 trace
Potatoes Japan 1970 3 0.5-1.0 EC; nd nd nd
Sweet
Potatoes Japan 1973 1 3.0-4.5 Gran nd-0.01
Rice in husk U.S.A. 1972 3 0.11 Gran 0.01-0.02
Rice hulled Japan 1973 4 0.5-0.75 EC 0.022-0.035 nd-0.07 nd-0.06 nd-0.008
Rice hulled Japan 1972 3 2 Gran nd nd nd
Rice huIled Japan 1969 3 0.6-0.9 SC 0.016 nd nd nd
Rice
polished Japan 1969 1 0.5 -0.75 EC nd nd
Strawberries Japan 1971 2 0.6 -1.5 EC 1.0-2.87 0.67-1.6 0.16-1.7 0.03-0.9
TABLE 1. (Continued)
Application Residues (mg/kg) at intervals (days) after application
rate
Crop Country Year no kg ai./ha formulation 0/1 3 7 14 21 28 35
Tangerines Turkey 1967 1 1% bait 0.8 0.12
2 1% bait 0.25
4 1% bait 4.00 1.10
1968 1 1% bait 0.71 0.53
1969 3 1% bait 2.92 2.00
1969 6 1% bait 3.19
Tomatoes Japan 1970 2 0.9 -1.5 EC nd-0.89 nd-0.34 nd-0.06 nd
potatoes, strawberries and tomatoes. See also "Fate of residues",
"In plants".
FATE OF RESIDUES
In animals
Avrahami and White (1975) treated two lactating dairy cows with 20%
fenthion as a topical spot-treatment used for the control of lice
using 32P-labelled fenthion applied at the rate of 9 mg/kg body
weight. Highest residues of total radioactivity in the blood, milk
urine and faeces appeared between the first and second day after
treatment. The residues were predominantly water-soluble hydrolysis
products of fenthion. The highest daily average level of fenthion and
its organosoluble metabolites in the milk from the two cows was
approximately 0.1 mg/kg on the first day after treatment. Of the total
radioactivity applied to each cow, 45-55% was recovered in the urine,
2-2.5% in the faeces and 1.5-2% in the milk over a period of 4 weeks.
Johnson and Bowman (1972) administered fenthion to lactating dairy
cows at the rate of 25, 50 and 100 ppm in the total daily ration for
28 days. Total residues consisting of fenthion, its sulphoxide and
sulphone and the sulphoxide and sulphone of the oxygen analogue in the
milk averaged 0.016, 0.049 and 0.099 mg/kg, respectively over the
period. Total residues in faeces consisted of fenthion and its
sulphoxide and averaged from 0.042 to 0.308 mg/kg. Neither fenthion
nor its oxygen analogue was found in urine but totals of the
sulphoxide and sulphone of fenthion and its oxygen analogue averaged
from 0.43 to 1.05 mg/kg. Seven days after feeding was terminated,
residues could not be detected in milk, urine or faeces.
In plants
Zadrozinska (IT2) studied the metabolism of fenthion in broadbean
plants and blackcurrants following topical application, by taking
samples every second day until biological activity could no longer be
traced. Fenthion disappeared quickly and four metabolites were
identified as fenthion sulphoxide, fenthion sulphone, fenoxon
sulphoxide and fenoxon sulphone. Fenthion sulphoxide was the most
durable compound, still being found 30 days after application to beans
and 64 days after treating currants.
Glogowski et al. (1974) studied the rate of degradation of fenthion
residues in apples, plums and sweet cherries over two cropping seasons
in Poland. Residues of fenthion and its metabolites in apples averaged
5.1-5.3 mg/kg immediately after treatment, 0.1-1.5 mg/kg after 14 days
and always less than 1 mg/kg at 21 days. By the 35th day, the residues
were below the limit of determination (0.05 mg/kg). During the 35-day
post-treatment period the average weight of each apple had increased
from 3 to 44 g. Part of the reduction is thus due to growth dilution.
In the case of sweet cherries, the same workers showed that the
initial deposit of about 20 mg/kg had declined to about 0.5 mg/kg by
the 21st day after spraying. The fruit in this time had increased in
weight from about 1 g. to 6 g. The similar pattern was observed in
plums where the concentration of residues declined from 10 mg/kg to
0.05 mg/kg in 28 days. In all these trials the treatment had been
applied at the optimum time for the control of the major pest species.
These studies indicate there is considerable similarity in the rate of
decline of fenthion residues on the different fruits, apples, cherries
and plums. Table 2, sets out the data from the work of Glogowski et
al. (1974) in a manner that permits ready comparison between the
residue levels on different species of fruit, and different cultivars,
in succeeding years. It is obvious that the effect of season and
cultivar is at least as great as the influence of fruit variety. This
study provides valuable insight into the variability of residue levels
notwithstanding efforts to standardize conditions and test procedures.
It provides a warning of the danger of establishing maximum residue
limits on the basis of limited trials data.
In applying these findings it should be recognized that the residues
resulting from a treatment 21 days before harvest, for example, would
not necessarily be the same as that found 21 days after a spraying
applied at a stage when the fruit would not normally be picked for
about 35 days (i.e. to very much more immature fruit).
In processing and cooking
Trials made in Turkey in 1968 and 1969 involved the treatment of tea
bushes with fenthion sprays and the subsequent harvesting of leaves
for the manufacture of (fermented) tea. The application of fenthion
sprays containing 50g. fenthion per 100 l of spray produced a residue
in manufactured tea ranging from 0.48 to 1.60 mg/kg when the leaves
were picked 17 days after the second of two sprays: when the spray
concentration was increased to 63g/100 l and the leaves harvested 24
days after a single spray the residues in the manufactured tea reached
1.38 mg/kg. Fenthion has not yet been adopted for use on tea crops in
Turkey.
In soil
The paper of Walnofer et al. (1976) demonstrates that the soil fungus
Rhizopus japonicus in nutrient solution is capable of oxidizing
fenthion to yield the sulphoxides of both fenthion and its oxygen
analogue. The only product of enzymic hydrolysis was the "phenol
sulphoxide" (3-methyl-4-methylsulphinylphenol).
In water
Fredrickson and Nichols (1976) studied the photodecomposition of
fenthion in aqueous solution of concentration 5 mg/l at 5°C and 25°C
using artificial illumination closely approximating sunlight. They
showed that fenthion decomposed with a half-life of 55 minutes at 5°C,
15 minutes at 25°C and 10 minutes when sensitized with 2% acetone.
TABLE 2 Disappearance of fenthion residues from apples, plums, cherries (Glogowski et al., 1974)
Residue, mg/kg, in (fruit, cultivar and year)
Days after Apples Apples Apples Apples Plums Plums Cherries Cherries
spraying A B C B D E G G
1969 1969 1970 1970 1969 1970 1970 1971
0 5.32 8.20 10.06 15.11 7.11 10.85 19.15 19.00
1 8.05 2.92
3 1.94 3.07 4.12 2.65 2.82 9.45 6.14 12.54
7 1.20 1.06 2.73 1.66 0.85 3.72 3.58 6.45
10 0.42 0.38 1.82 1.19 - 0.91 2.78 2.37
14 0.11 0.11 1.55 0.41 0.20 0.80 1.32 2.03
21 0.08 0.06 0.40 0.35 0.11 0.60 0.35 0.70
28 0.03 0.03 0.20 TRACE 0.06 0.05 0.24 -
35 TRACE TRACE 0.16 - - TRACE TRACE -
Degradation products were the sulphoxide, sulphone, oxygen analogue
and its sulphoxide together with the corresponding phenol, phenol
sulphoxide and phenol sulphone. Up to 39% of the radioactivity
represented polar degradation products believed to be polymeric.
EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION
Information supplied by the US Food and Drug Administration indicated
that in the course of monitoring residues in domestic food commodities
during 1975 and 1976, fenthion residues were found in peaches (0.02
mg/kg), paprika (0.04 mg/kg), peppers (0.022 mg/kg) and potatoes
(trace). No other information came to hand.
APPRAISAL
Following evaluation by the Joint Meeting in 1971 a request was made
for additional information on the occurrence of residues in citrus
fruit, coffee, cucurbits, onions, potatoes, sugar beet roots and tops.
The 9th (1977) Session of the Codex Committee on Pesticide Residues
requested a review of the maximum residue limits in the light of
information provided by governments and other relevant data such as
disappearance.
Results from a considerable number of supervised residue studies were
provided by the principal manufacturer and by Poland, the Phillipines
and Turkey. Other information was provided by the USA and by published
scientific literature.
This information has confirmed that the maximum residue limits
previously recommended for fenthion residues in apples, cherries,
grapes, peaches and rice are adequate to cover the residues resulting
from approved uses of fenthion provided there is a reasonable pre-
harvest interval. None of the maximum residue limits appear
excessively high in the light of the new data.
One extensive study from Poland carried out over two seasons
demonstrates the rate of decline of fenthion in apples, cherries and
plums. There is considerable similarity between the rates of decline
of residues on the different species of fruit that is partly
influenced by growth dilution. Fourteen or 21 days after spraying, the
difference in residue level between two distinctly different fruits is
often less than the difference between two cultivars of the same
species or between residue levels in the same cultivars in two
succeeding years. This study is a very useful indicator of the
variability of residue levels notwithstanding efforts to standardize
conditions and test procedures. It points to the danger in placing too
much reliance on limited amounts of data as representing the position
in different regions, seasons, cultivars, formulations and application
techniques.
Residue data from studies in Turkey and Japan point to the need to
raise the maximum residue limit for fenthion in citrus fruit where
residues occur mainly in the peel. Studies in Japan show that the use
of fenthion on potato plants does not give rise to measurable residues
in potato tubers.
Information considered by the meeting provides a basis for
recommending additional maximum residue limits in bananas, beans,
onions, pears, plums, potatoes, strawberries, sweet potatoes and
tomatoes.
Extensive studies in Turkey indicate that there is a high risk that
olives treated for the control of fruit flies will contain residues
above the maximum residue limit even when a 30-day pre-harvest
interval is observed.
Further studies have confirmed that fenthion present in livestock feed
or used for the control of external parasites gives rise to low but
transitory residues in milk. The metabolism of fenthion in cattle has
been clarified by these studies.
It has been shown that sunlight causes rapid degradation of fenthion
and the production of polar products believed to be polymeric phenols.
No information was received to assist in resolving the questions about
residues in coffee, cucurbits and sugar beets.
RECOMMENDATIONS
The temporary maximum residue limits previously recommended, with the
exception of the limit for oranges which is replaced by a higher limit
for citrus, are confirmed. New recommendations are listed below.
They refer to the sum of fenthion, fenthion sulphoxide, fenthion
sulphone and the oxygen analogues of these compounds, determined as
the sulphone of the oxygen analogue and expressed as fenthion.
FURTHER WORK OR INFORMATION
REQUIRED (by July, 1978)
1. Adequate two-year feeding studies in the dog in one rodent species.
2. Establishment of the sequence of metabolic changes in humans and
laboratory animals in order to elucidate the mechanism of
cholinesterase inhibition.
TABLE
Commodity Limits, mg/kg Pre-harvest interval on
which recommendations
are based
Bananas 1 post-harvest
Beans 0.1 21
Citrus 2 21
Citrus juice 0.2 21
Onions 0.1 14
Pears 2 10
Plums 1 21
Potatoes 0.05* 28
Sweet Potatoes 0.1 28
Strawberries 2 7
Tomatoes 0.5 7
* at or about limit of determination
DESIRABLE
1. Information from additional countries on crops already considered
and on additional crops in order to confirm the level of residues
following approved uses of fenthion.
2. Information on the effect of processing and cooking on fenthion
residues in fruits and vegetables.
REFERENCES
Avrahami, M., and White, D.A. (1975) Residues in milk of cows after
spot-treatment with 32P-fenthion. New Zealand J. Exptl. Agric. 3,
309-311.
Bayer, A.G. (1977) Residues of Fenthion in Crops - Biologische
Forschsung Submission to FAO, Nov. 1977.
FAO/WHO, (1972) 1971 Evaluations of some pesticide residues in food
- WHO Pesticide Residue Series No. 1; FAO Document AGP -1971/M/9/1.
FAO/WHO, (1976) 1975 Evaluations of some pesticide residues in food
- WHO Pesticide Residues in food - WHO Pesticide Residue Series No. 51
FAO Document AGP 1971/M/13.
Fredrickson, D.R. and Nichols, S.S. (1976) Photodecomposition of
BAYTEX - Chemagro Division, Mobay Chemical Corporation Report No.
49347, Aug. 9, 1976.
Glogowski, K., Welter, M., Czaplicki, E. and Witkowskiy W. (1974)
Studies on the degradation rate of fenthion residues in apples, plums
and sweet cherries sprayed with LEBAYCID - Pflanzenschutz-Nachrichten
Bayer 27(2) 156-166.
Johnson, J.C. and Bowman, M.C. (1972) Responses from cows fed diets
containing fenthion of fentrothion - J. Dairy Sci. 55(6) 777-782.
Kirca, A.C. (1976)Information furnished by the Ministry of Food,
Agriculture and Animal Husbandry - Turkey. Letter to WHO from
Permanent Mission of Turkey, 20 January 1976.
Magallona, E. (1977) Residues resulting from supervised trials
- Submission on behalf of the Phillipines to FAO.
Wallnofer, von P., Sohlemann, F. and Dehlmann, L. (1976) The effect of
fenthion on the organism Rhizopus japonicus.
Pflanzenschutz-Nachrichten Bayer 29/1976(3).
Zadrozinska, J. (1972) A study of fenthion in selected plants (Polish)
- Roca. Panstw. Zakl. Hig. 23 (4) 409-416.