DICLORAN JMPR 1977
Explanation
Dicloran was evaluated by the Joint Meeting in 1974 (FAO/WHO, 1975). A
temporary acceptable daily intake for man was estimated to be 0.03
mg/kg body weight and recommendations were made for temporary maximum
residue limits in a range of fruits and vegetables.
The Meeting considered that further studies on the ocular disturbance
observed in dogs to confirm and clarify this effect and further
information on the fate in livestock (since plant material containing
residues may be fed to animals) were required before the temporary ADI
and recommended maximum residue limits could be confirmed. The Meeting
also considered that it was desirable to have information on the
following points.
1. Effects on hepatic microsome systems in several species.
2. Further observations in humans.
3. Further information on the fate of residues during storage,
transport and processing of fruit and vegetables.
4. Information on transfer of residues from grapes to wine and on
possible influence on wine processing.
5. Further information on soil residues and their possible uptake into
subsequent crops.
6. Further data to clarify inconsistencies in the residue levels found
in different berries.
The Codex Committee on Pesticide Residues at its 9th Session (1977)
considered a request to increase the maximum residue limits for
dicloran on apricots to 15 mg/kg and to include a similar
recommendation for nectarines.
Information on some of these matters together with information about
the nature and level of dicloran residues on various crops was
available for evaluation by the Meeting and is summarized in the
following monograph.
Attention is drawn to a number of errors which appear in the 1974
monograph (FAO/WHO, 1975.)
Page 215 "DinitranilR" is not a registered trade mark for
dicloran. "RegisanR" is another trade mark for dicloran. Solubility
in glacial acetic acid is 0.8 g, not 8.8 g/100 ml.
Page 216 The technical material typically contains not less than
96% dicloran.
Page 225 Use pattern -- dicloran is registered and sold in the
following countries -- Australia, Brazil, Canada, Egypt, Greece,
Holland, Israel, Italy, Japan, New Zealand, South Africa, UK, USA,
Zambia.
Third paragraph -- delete "thiram (TMTD)" and insert "captan".
Page 235 Page 235 should appear between page 237 and 238.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
BIOCHEMICAL ASPECTS
Absorption, distribution and excretion
Prolonged oral administration of dicloran to dogs (25 and 50
mg/kg/day) produces lesions in the cornea and lens of the eye, but
this occurs only in the light (Curtis et al., 1968; Bernstein et al.,
1970; Earl et al., 1971). Comparable studies in miniature swine (Earl
et al., 1971) and in human volunteers (0.4 mg/kg/day) for 3 months
(Upjohn, 1962) produced no similar ocular symptoms. Toxicity studies
carried out on rats and Rhesus monkeys show that the oculotoxicity is
confined to the dog (Serrone et al., 1967).
14C-dicloran (100 mg/kg/day for 5 days) was administered orally to
dogs (4), pigs (4) and rats (8). The radiolabelled residues in dog and
pig tissues were similar and higher than in the rat. All 3 species
showed a high residue in the liver but in dogs and pigs the highest
residues were found in the pigmented tissues of the eye. Nonpigmented
eye tissues (cornea and lens) had low residues and there was no
correlation between oculotoxicity and tissue residues of dicloran and
its metabolites. A more rapid increase of plasma levels of 14C occurs
in the dog. At 3 days of dosing the plateau plasma levels in pig and
dog were similar (10-15 mg/kg 24 hours after dosing).
The levels of radioactivity excreted in the bile of dogs and pigs were
high. The spectrum of metabolites, on preliminary examination, shows
significant species differences (Hamilton, 1977).
Biotransformation
10-40 mg/kg of dicloran was administered orally or interperitoneally
to rats. Following i.p. injection 83% of the dose was excreted in the
urine in 3 days (70% in 24 hrs) and 1.5% was excreted in the faeces;
after oral administration 91% of the dose was excreted in the urine in
3 days (77% in 24 hrs) and 1% was excreted in the faeces. Little
appears to be excreted in the bile of the rat (2% of the dose in 6 hrs
after i.p., 5% in 12 hrs after oral).
The major metabolite present in the urine was
4-amino-3,5-dichlorophenol (50% of the dose, 70% of the urinary
activity) and the only other metabolite detected in the urine was
4-amino-2,6-dichloroaniline (Matè et al., 1967).
In vitro studies with mouse-liver microsomes gave equal and small
amounts each of 4-amino-3,5-dichlorophenol (aminophenol) and
4-amino-2,6-dichloroaniline (phenylenediamine).
Similar routes of metabolism have been found in rats, dogs and monkeys
(Bachmann et al., 1971).
Dicloran stimulated rat liver mixed function oxidases at oral doses of
10 mg/kg or more; doses of 500 mg/kg, decreased mitochondrial
oxidation of succinate without concomitant uncoupling of oxidative
phosphorylation (Bachmann et al., 1971). In single dose experiments,
oxidative phosphorylation was not affected at any dose level. Dicloran
does not affect brain or liver mitochondrial function of mice.
Daily administration of 1000 mg/kg to rats produced uncoupling of
oxidative phosphorylation after 4 days. The metabolite of dicloran,
4-amino-3,5-dichlorophenol was as active as 2,4-dinitrophenol, in
vitro, in uncoupling oxidative phosphorylation, whereas dicloran was
only one-tenth as effective. The phenylenediamine metabolite had no
effect in vitro on mitochondrial respiration or oxidative
phosphorylation (Bachmann et al., 1971).
It should be remembered that the metabolite 4-amino-3,5-dichlorophenol
is excreted in the urine of rats as a conjugate (Matè et al., 1967)
and conjugation of this metabolite in the liver would lead rapidly to
its deactivation in vivo.
Dicloran and its metabolite, 3,5-dichloro-4-aminophenol, inhibited
electron transport and uncoupled oxidative phosphorylation at 10-5M
in vitro, whereas the metabolite 2,6-dichlorophenylenediamine showed
only slight uncoupling at 10-4M. These inhibitory effects in vitro
cannot be considered as serious adverse effects since they are not
confirmed by similar observations in vivo. Mitochondria isolated
from rats treated with dicloran or its metabolites were functionally
normal (Gallo at al., 1976).
TOXICOLOGICAL STUDIES
Special study on mutagenicity
Dicloran was shown not to be a mutagen in strains of
B.subtilis, S. typhimurium and E.coli (Shirasu at al., 1976).
These studies did not include metabolic activation of the test
chemical (dicloran) with rat liver microsomal preparations.
Special study on carcinogenicity
One study describes dicloran as non-toxic and non-carcinogenic. The
number of animals on test at the higher dose level (about 500
mg/kg/day, for 1 year) was only 5. The number on test at the lower
level (29 animals at about 150 mg/kg) was sufficient to detect a very
low order of carcinogenicity (Hadidian at al., 1968).
An LD50 in the rat of 1500-4040 mg/kg is reported by Jones et al.
(1968) and Backmann et al. (1971).
Short term studies
Rat
The experiments are summarised as follows:
500 mg/kg/day for 4 days; 500 mg/kg/day for 30 days; 500 mg/kg/day for
12 weeks; 1000 mg/kg/day for 4 days; (Gallo et al., 1976).
Doses of 400 mg/kg/day to rats for 3 months were without apparent
serious adverse effects, but is not noted that at 1000 mg/kg/day there
were some deaths (Serrone et al., 1967).
Monkey
It has been reported that oral doses of 160 mg/kg/day were lethal to
monkeys within 3 months, and that these dosages were more toxic to the
male animals than to the females. It was observed further that the
urine of rats receiving dicloram chronically was orange-coloured, but
that the samples obtained from monkeys were not (Serrone et al.,
1967).
Long term studies
Rat
In an experiment, rats were dosed according to the regimen: oral
administration 5 days/week for a total of 260 doses. Dicloran was
given at 3 dose levels: 30, 100 and 300 mg/rat/day. The last of these
dosages killed 2/3 animals, while at 100 mg/rat/day the mortality was
0/3 males and 1/3 females. At the 30 mg/rat/day level the mortality
was 0/14 males and 0/15 females. (Average survival times are given as
556 days for the males and 563 days for the females at 100 mg/rat/day;
497 and 499 days, respectively, for the males and females at 30
mg/rat/day. Since the initial weights of the 100 mg/rat/day males
averaged 57 g and the final weights averaged 369 g (for the females,
55 "illegible") the 100 mg/rat/day regimen provided an average
intake of about 500 mg/kg/day for the males, and of about 550
mg/kg/day for the females. Similarly, the 30 mg/animal/day regimen
provided mean intakes of about 140 mg/kg/day for the males and of 175
mg/kg/day for the females (Hadidian et al., 1968).
Rat and monkey
Dicloran administered orally to rats (400 mg/kg/day) produced
significant liver enlargement and increased the activities of the
liver microsomal enzymes (demethylase and desulphurase) after either
single or multiple administrations; liver mitochondrial utilization of
O2 was simultaneously increased. No changes in heart or kidney
mitochondrial oxygen consumption was observed. No enhancement of the
hepatic microsomal enzymes occurred in monkey. Centrilobular fatty
infiltration of liver, and mitochondrial swelling and distortion of
the cristae were observed in liver and kidney, in the monkey (Serrone
et al., 1967).
COMMENTS
Dicloran (2,6-dichloro-4-nitroaniline) was previously evaluated and a
temporary ADI for humans was established. Further studies on the
oculotoxicity observed in the dog and of the fate of dicloran in
livestock were requested. Further work on the effects of dicloran on
the hepatic microsomal enzymes of animal species and further
observations of the effects of dicloran in humans were considered
desirable.
A study of the disposition of orally administered 14C-dicloran in
rats, dogs and pigs has shown substantially higher concentrations of
radioactivity in the tissues of dog and pig than rat. A more rapid
increase in plasma concentration of 14C in the dog than in either pig
or rat, and a different spectrum of the metabolites suggests that
there is a species differences in the kinetics of metabolism. The
higher concentration of 14C in the retina and iris of the eye of the
dog than occurs in other dog tissues or in the pigmented tissues of
the eye of the rat or pig, goes some way to explaining the
photosensitive oculotoxic effects of dicloran which have been observed
in the dog. It is likely that at least some of this radioactivity
present in the pigmented tissues of the dog eye is attributable to the
major metabolite of dicloran, 4-amino-3,5-dichlorophenol; under the
influence of light this would be oxidized to the corresponding
quinoneimine which could diffuse into the non-pigmented tissues of the
eye, the lens and cornea, producing lesions owing to the oxidation of
this metabolite.
The oculotoxic effects in the dog are therefore partly explained by
the different kinetics of dicloran seen in this species and the known
sensitivity of the dog eye to oxidant chemicals. No similar oculotoxic
effects have been seen in rat, pig, Rhesus monkeys or humans dosed
with dicloran.
Dicloran, at doses of 10 mg/kg/day or more, results in induction of
the microsomal mixed function oxidases of rat liver, larger doses (400
mg/kg/day) result in liver enlargement, and still larger doses (500
mg/kg/day) decreased mitochondrial oxidation, but without the
uncoupling of oxidative phosphorylation. Both dicloran and its major
metabolite, 4-amino-3,5-dichlorophenol, inhibit mitochondrial electron
transport and uncouple oxidative phosphorylation in vitro but not
in vivo, probably because of the conjugation of the metabolite(s)
in vivo.
In mutagenicity studies in various strains of B.subtilis and
S.typhimurium and E.coli, with and without activation by rat liver
microsomal enzymes, dicloran was not found to be mutagenic.
In view of the further work carried out to explain the oculotoxicity
of dicloran in the dog, the metabolic and pharmacokinetic studies in
the pig, and studies on the effects of dicloran on liver microsomal
enzymes, in compliance with the requests of the Joint Meeting, 1974,
it was recommended that the previous temporary ADI for humans be made
an ADI for humans at the same level.
TOXICOLOGICAL EVALUATION
Level causing no toxicological effect
Rat: 1000 mg/kg in diet, equivalent to 50 mg/kg bw
Dog: 10 mg/kg in diet, equivalent to 2.5 mg/kg bw
ESTIMATE OF A TEMPORARY ACCEPTABLE DAILY INTAKE FOR
HUMANS
0-0.03 mg/kg/bw
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
In addition to the uses summarized in 1974 (FAO/WHO 1975) dicloran is
recommended and registered for pre-harvest treatment of beans,
cucumbers, endives, gherkins, lettuce, melons, parrika and wetloof
chicory, mostly for the control of Botrytis and Sclerotinia.
Attention is drawn to the fact that dicloran is a fungistat rather
than a fungicide. It is fungistatic to the mycelium and spores of
Botrytis cinerea. It delays germination and causes a severe check to
hyphal growth. It is suggested that dicloran is a structurally
non-specific toxicant exerting its effect by disorganizing cell growth
and division in particular plant pathogens.
To exert its effect and to maintain treated fruit and vegetables in a
disease-free condition there must be a biologically effective
concentration of dicloran evenly distributed over the surface of
commodities susceptible to attack by these rot-producing
micro-organisms.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Apricots
No new information was available to enable the Meeting to judge the
necessity to raise the maximum residue limit from 10 mg/kg to the
proposed level of 15 mg/kg. The data from extensive residue studies in
California in 1964 which were evaluated by the 1974 Meeting were
re-examined. It was judged that the summary in the 1974 monograph
(FAO/WHO 1975) reflects the findings in these trials. It is
recognized that a number of countries have established maximum residue
limits higher than 10 mg/kg for apricots to reflect the residues
resulting from both pre-harvest and post-harvest use and it is noted
that the data on which these limits were established will be furnished
to a future Joint Meeting.
Berry fruit
No additional information has become available to throw light on the
matter of the wide variation in residue levels reported in trials
evaluated in 1974. However, the raw data from these trials have been
examined and there appear to be no anomalies in the conduct of the
trials or in the analysis of samples.
There were several species of berries involved and a number of
different cultivars of separate species. Although the trials were
mostly conducted in the northwest of the USA, the ecological and
environmental conditions were obviously different at the different
trial sites. All the data show a distinct trend for the highest
residue levels to be found following the application of the highest
rate of dicloran and for the residues to be higher when the interval
between last treatment and harvest is shortest.
Since the analyses were all carried out in the same laboratory by the
same methods of analysis, it must be concluded that the variation that
was found is typical of that occurring with berry fruits under
practical conditions. No doubt the surface structure of the berries
affects the retention of the spray. Whether minor variations in
spraying, technique or spray equipment contribute to the variation
cannot be determined from the information available, but this seems
highly probable.
TABLE 1. Dicloran residues resulting from supervised trials
Application Residues (mg/kg) at intervals (days) after application
Crop Country Year no. rate formulation 0 1 3 7 14 21 27
kg a.i./ha
Gherkin Netherlands, 1970 1 0.7 smoke 0.4 0.2 <0.2
generator
1972 0.7 " 0.6 0.1
Lettuce Netherlands 1970 1 0.7 5.1 < 0.3 < 0.3
2 0.7 0.3
1970 1 1.4 < 0.3
1970 2 1.4 0.3
1970 1 2.8 2.2
1970 2 0.7 3.9 5.0 2.9
1970 2 0.7 4.6 4.8 4.6
1970 2 0.7 2.6 0.7
1973 3 0.7 + 6.4 smoke
generator 20.3 2.2 0.7 0.2
&
soil
treatment
1973 3 " 12.0 3.8 2.0 0.9
1973 3 " 5.6 3.1 1.8
1973 3 " 8.3 3.1 1.0 0.7
Gherkins
Studies in the Netherlands where dicloran was applied by means of a smoke generator to gherkins growing in glasshouses showed that, generally,
the residue deposited on the fruit is less than 1 mg/kg immediately after treatment. The residue level declines rapidly and thus the fruit, which
must be harvested continuously, is unlikely to contain more than 1 mg/kg of dicloran residues. See Table 1.
Lettuce
Extensive studies in the Netherlands in 1970-73 showed that when lettuce in glasshouses is treated with dicloran applied by means of a smoke
generator the residue levels vary greatly irrespective of the amount applied. The rate of decline of residues is relatively slow, being
influenced by the confined environment of the glasshouse. A combination of soil treatment and treatment by means of smoke generator produces
higher residues which decline at least as rapidly as those deposited by the smoke generators alone.
Chicory
The use of dicloran in the production of chicory (Wetloof) in forcing beds has been practiced since 1961. Trials carried out in the Netherlands
have shown that the spray application of dicloran as dust or wettable powders at rates up to 20 mg/kg on the roots and forcing beds produces
residues ranging from 1-35 mg/kg on the roots but only up to 0.5 mg/kg on the edible portion, the sprouts. Likewise the dripping of chicory roots
prior to planting leads to dicloran residues of up to 35 mg/kg in the roots but less than 0.5 mg/kg in the sprouts. Significant residues occur in
waste products used for animal feed.
Onions
Dicloran has proved effective for controlling storage rots of onions, especially those caused by Botrytis alii and Sclerotinia cepivorum, when
applied as a dust (8%) to the onions in storage bins. The dust is used at the rate of 1 kg/tonne of onions. Studies in Australia (Allen, 1973)
showed that the residue level is directly related to the rate of application. The bulk of the dicloran is confined to the outer layers,
especially to the loose paper-like layers surrounding the bulb. It was observed that the process of sorting and packaging, which incidentally
results in dislodging much of the outer paper-like layer, reduces the residue to approximately half. The results of these studies are summarised
in Table 2.
TABLE 2. Dicloran residues on onions treated post-harvest
Residue level mg/kg
Rate of application Inner layer Outer layer Whole bulb
1 kg 8% dust/tonne 1.09 21.63 10.20
2 kg 8% dust/tonne 1.32 47.6 21.00
dust-after sorting
and packaging 1.14 20.90 9.56
Nectarines, peaches
Allen et al. (1973) carried out a trial to determine the effect of a
new colloidal formulation of dicloran on residue levels on peaches and
nectarines dipped in suspensions containing 0.065% and 0.075%
dicloran. Residues were determined at 1, 2, 4, 6, 8, 10, 12 and 14
days after dipping. The residue level varied from 3 to 12 mg/kg in the
case of peaches and 2 to 6 mg/kg for nectarines. Obviously the nature
and condition of the skin of the fruit affects the uptake and
retention of dicloran. There was considerable variation between
samples analysed on various days with no consistent trend; in fact the
highest residue was found on the samples taken 14 days after dipping.
These data support the recommendation made in 1974 for peaches and
suggest that nectarines are similar to apricots in their capacity to
take up and retain dicloran residues. See also "Fate of residues", "In
plants".
FATE OF RESIDUES
In animals
Hamilton (1977) has reported the results of a study designed to
determine the distribution of dicloran in the tissues of rats, dogs
and pigs following repeated oral dosing at 100 mg/kg/day. For further
details of this and other metabolic studies see "Biotransformation".
Pigs slaughtered 24 hours after the administration of the last of 5
daily doses of dicloran equivalent to 100 mg/kg were found to have
varying levels of radioactivity in many different tissues ranging from
1 mg/kg dicloran equivalent in brain through 2 mg/kg in muscle, 8
mg/kg in fat and kidney to 24 mg/kg in liver, with somewhat higher
levels in sections of the eye. The experiment was not designed to
determine the rate of build-up or rate of excretion of dicloran
following consumption by pigs.
Wright (1968) reported that the administration to dairy cows of high
levels of dicloran (50 mg/kg/day) resulted in easily detectable milk
residues which persisted for up to 7 days following treatment. The
maximum level detected in milk following 2 to 3 days of administration
was 7 mg/kg. This however was in a cow whose milk production dropped
to one-quarter to that observed prior to beginning treatment. The
highest concentration detected in the milk of other cows in the trial
was 0.2 mg/kg. The concentration of dicloran residues in the milk 24
to 36 hours after discontinuing administration was only of the order
of 0.05 mg/kg. The limit of determination of the method used (GLC) was
0.01 mg/kg.
In a parallel trial Wright (1968) administered dicloran in the rations
of dairy cows at levels of 0, 5, 20 and 80 ppm in the total diet,
daily for 28 days. The residue picture of the milk from all 9 cows
receiving dicloran was not significantly different from that of
control cows receiving unmedicated rations. In view of the level of
residues found in agricultural commodities following the use of
dicloran as a fungistat, these results provide assurance that residues
are not likely to occur in milk following the feeding of dairy cows
with food wastes containing dicloran residues.
In processing and storage
Chamberlain (1963 a,b) investigating the effect of home preparation
and cooking on residues of dicloran on tomatoes, Brussels sprouts and
beans found that tomatoes with obviously visible residues could not be
cleaned satisfactorily by hand brushing. The removal of the visible
deposit was easy using water. He carried out two series of tests on
fruit picked 7 and 14 days after spraying. The fruit was analysed
after a further 1, 3 and 6 days at room temperatures. Though the
residue on the unclean fruit fell by about 30% (7 to 5.2 mg/kg) the
simple cleaning, as might be practised in the home, reduced the
residue from 7 to 0.5 mg/kg.
Brussels sprouts dipped in dicloran at the standard rate of 0.2 kg of
formulation per 100 l of water were found to have a residue of 3.8
mg/kg. After simple washing the residue declined to 0.7 mg/kg.
Green beans which had been dipped in dicloran suspension at
recommended rates were cooked after being held in storage for 5
different periods ranging from 7 hours to 13 days. Storage alone
caused a decline in residues from 12 to 5.3 mg/kg, and normal domestic
cooking caused a further loss of slightly more than 50% of the residue
present before cooking. In a further series of experiments Chamberlain
was able to show that of the initial dicloran deposit on beans,
approximately 30% is lost in the cooking water, approximately 30% is
lost through volatility in steam and 30 to 50% is retained by the
beans.
The Upjohn Company (1968) carried out an extensive series of
experiments in California designed to obtain registration for the use
of dicloran for post-harvest treatment of peaches for canning. In
these trials peach trees were sprayed with dicloran 13 and 1 days
prior to harvest using both dust and wettable powder formulations. The
harvested peaches were then dipped in dicloran suspensions under
commercial conditions. The crop was then sampled for analysis and the
remainder was subsequently canned commercially. The results indicate
that only small residues (<0.05 mg/kg) result from the pre-harvest
treatment but that the total residues following both pre- and
post-harvest treatment range from 15 to 45 mg/kg with the bulk of the
results being in the range of 20 to 30 mg/kg. None of the samples of
canned peaches from the 16 separate trials contained any detectable
residue of dicloran when analysed by microcoulometric gas
chromatography with a limit of determination of 0.01 mg/kg.
In a parallel series of experiments on plums/prunes the Upjohn Company
determined the level of dicloran residues on unwashed, washed and
washed and canned prunes that had been treated pre-harvest and
post-harvest with dicloran. Whilst the residues on the unwashed fruit
ranged up to 17.5 mg/kg in the case of dusted fruit and 8.7 mg/kg in
the case of sprayed, washing reduced the residue level to the range of
3 to 4 mg/kg. None of the canned fruit from any of the 16 separate
treatments examined contained residues above 3.1 mg/kg showing that
the washing and canning operation reduced the residues considerably,
particularly those which were high owing to the pre-harvest
application of dicloran dust.
The Upjohn Company (1969) studied the effect of applying dicloran to
grapes pre-harvest on the residue level in grapes and wine and on the
fermentation and wine quality. Four types of wine grapes were treated
once or twice at 13 and 7 days prior to harvest. The amount of
dicloran used (2 and 3 kg/ha) was the maximum likely to be needed for
the treatment of grapes. None of the grapes harvested 7 days after
treatment and none of the fractions including juice, stem, pomace or
fermented wine contained detectable residues. The analytical procedure
based on microcoulometric gas chromatography had a limit of
determination of 0.01 mg/kg.
The wines produced from the grapes treated with dicloran were
submitted to a taste panel and the report indicated no evidence that
dicloran-treated grapes adversely affect the smell or taste of wine.
In soil
Van Alfen and Kosuge (1974) studied the effect of various
micro-organisms on dicloran in liquid culture. Escherichia coli and
Pseudomonas cepacia both converted dicloran to
2,6-dichloro-p-phenylene diamine (DCPD) a 4-amino-3,5-dichloro
acetailide (ADCAA). Culture fluids of an unknown bacterium yielded
ADCAA but no detectable amounts of DCPD. The organisms differ in their
capacity to produce these metabolites. P.Cepacia completely
metabolized dicloran within 48 hours and accumulated ADCAA in the
culture fluid as the major metabolite. E. coli rapidly utilised
dicloran but accumulated DCPD as the major metabolite.
Van Alfen and Kosuge (1976) carried out experiments with dicloran on
samples of incubated soil. They found that after 3 days only 7% of the
applied dicloran could be recovered and after 9 days only 3%. The
major metabolite that was extractable from soil was identified as
ADCAA. In the light of these findings it seems unlikely that any
significant amount of dicloran would be available to be taken up by
plants treated during the current or previous cropping cycle.
Dejonckheere et al. (1975) compared the uptake of quintozene,
hexachlorobenzene (HCB), dicloran and pentachloroaniline from soil by
lettuce. They found that lettuce grown in soil containing 2.13 mg/kg
of dicloran took up 0.13 mg/kg into lettuce harvested early in the
season and 0.08 mg/kg in lettuce harvested two weeks later. The ratio
of the concentration in lettuce to that in the soil was 0.04 in the
case of dicloran, 0.53 in the case of quintozene and greater than 1 in
the case of HCB.
Casanova and Dubroca (1973) carried out an investigation of residues
of various fungicides used in the treatment of lettuce crops under
glass. They were able to show that following soil treatment
considerable residues of quintozene appeared in harvested lettuce.
Residues of dithiocarbamates could be kept within acceptable limits
provided there was an adequate interval between treatment and harvest.
In the case of dicloran even the application of a combined soil and
foliage treatment gave rise to only very low residues.
Evidence of residues in food in commerce or at consumption
The U.S. Food and Drug Administration advises that during routine
monitoring of raw agricultural commodities throughout the USA in 1975
and 1976, 111 samples of fruits and vegetables were examined. Of these
11 were found to contain dicloran residues above the US tolerances.
Four of these were samples of cabbages for which there is no US
tolerance and 5 were potatoes where the tolerance is only 0.25 mg/kg.
The details are given in Table 3.
The Netherlands Food Inspection Services reported that of 970 samples
of domestically produced fruits and vegetables analysed in 1976 for
dicloran 40 (4%) contained residues above national maximum residue
limits. The bulk of these were cauliflowers (11), celery (9) and
radish (9) for which the limit is only 0.1 mg/kg. Few violations
occurred in samples of endive, lettuce and chicory where maximum
residue limits have been established at 3, 3 and 1 mg/kg respectively.
Details are given in Table 4.
The Netherlands Food Inspection Services reported that of 663 samples
of glasshouse lettuce collected at auction and analysed in 1975/1976
89% contained less than 0.2 mg/kg of dicloran. Four samples contained
dicloran residues above the limit of 3 mg/kg, 2 ranging up to 15
mg/kg.
APPRAISAL
Following the evaluation of dicloran in 1974, the Joint Meeting listed
information that was required before maximum residue limits could be
confirmed. Some of this information has been provided and was
evaluated.
The question of wide variation in residue levels in berry fruits was
considered in the light of further study of the extensive data
evaluated in 1974. It was judged that the variations were normal and
reflected the several species of berries involved, the different
cultivars of each species and the varying ecological and environmental
conditions. Experience with other pesticides applied to berries has
indicated that spraying technique and spray equipment can also
contribute to variations in residue levels.
When exaggerated levels of dicloran are administered to pigs and
cattle, significant residues can be found in various edible tissues
with the highest concentration in liver. However, cows receiving
rations containing dicloran residues at concentrations likely to be
found in agricultural commodities following the use of dicloran
produced milk without detectable traces of dicloran.
TABLE 3. Dicloran Residues in Commerce, USA 1975/76
Cabbage Carrots Celery Cherries Lettuce Okra Peaches Plums Potatoes Sweet Potatoes Tomatoes
mg/kg
0 - 0.10 2 4 2 1 1 24 12 2 1
0.101 - 0.30 1 5 1 14 3
0.301 - 0.50 1 4 1 5 2
0.501 - 1.00 1 1 4 1 1 1
1.001 - 2.00 1 5 1 1
2.001 - 3.00 2
3.001 - 5.00 2 2
5.001 - 10.00 3 1 1
>10.00 1 1
Total 4 4 12 1 13 1 50 1 20 4 1
Violations 4 0 0 0 1 1 0 0 5 0 0
national tolerance
TABLE 4A. Dicloran residues in Commerce, Netherlands, 1976
Endive Lettuce Purslane Turnip-tops Celery Spinach Corn salad Cauliflower Curled
kale
mg/kg
0.0 - 0.10 50 224 2 3 3 17 2 23 2
0.101 - 0.30 2 126 0 4 2 11
0.301 - 0.50 0 58 0 4
0.501 - 1.00 3 49 1 1
1.001 - 2.00 2 41 1
2.001 - 3.00 1 10
>3.00 4
Total 970 58 512 2 5 12 17 4 34 2
Violations 40 - 4 - 2 9 - - 11 -
= national tolerance
TABLE 4B. Dicloran residues in Commerce, Netherlands, 1976
Savoy Brussels Butter bean French Chicory Leek Cucumber Melon Paprica Tomato
Cabbage sprouts bean
mg/kg
0.0 - 0.10 1 7 7 29 150 2 22 7 11 24
0.101 - 0.30 0 1 19 1 1
0.301 - 0.50 0 1 1
0.501 - 1.00 1 6
1.001 - 2.00 0
2.001 - 3.00 2
>3.00
Total 1 8 7 30 178 2 23 7 11 26
Violations - 1 - 1 2 - - - - 1
= national tolerance
TABLE 4C. Dicloran residues in Commerce, Netherlands, 1976
Celeria Beet root Radish Apple Mushroom
mg/kg
0.0 - 0.10 1 3 14 1 3
0.101 - 0.30 5
0.301 - 0.50 2
0.501 - 1.00 2
1.001 - 2.00
2.001 - 3.00
>3.00
Total 1 3 23 1 3
Violations - - 9 - -
= national tolerance
Simple washing processes remove over 90% of dicloran residues.
Cooking removes approximately 50% of the residue from beans while the
canning of peaches removes all delectable residue from fruit treated
both pre- and post-harvest.
No detectable residues (<0.01 mg/kg) of dicloran or its metabolites
were found in wine made from grapes that had been treated with
dicloran. No adverse effect on fermentation or quality of wine could
be observed following the treatment of grapes shortly before harvest.
Micro-organisms readily convert dicloran into
2,6-dichloro-p-phenylenediamine and 4-amino-3,5-dichloroacetanilide.
None of several studies indicate any appreciable uptake of residues of
dicloran or its metabolites from soil by plants, including vegetables.
RECOMMENDATIONS
On the basis of the additional information before the Meeting the
temporary maximum residue limits previously recommended are confirmed
as maximum limits. In addition the following limits are recommended.
Commodity Limit, mg/kg
Onions 20
Nectarines 10
Chicory 1
FURTHER WORK OR INFORMATION
Desirable
1. Further observations in humans.
2. Results of further studies of the level and fate of dicloran
residues on apricots and nectarines, particularly following
post-harvest treatment.
REFERENCES
Allen, S.J., (1973) Dicloran residues on onions. Report of The Boots
Company (Australia) dated 26th July 1973.
Allen, S.J., Osborne, W.B., and Winton, E.C., (1973) Dicloran residues
on peaches and nectarines following dipping in 1 % "Allison Col."
-Report of The Boots Company (Australia) March 1973.
Bachman, Goldberg and Thibodeau. Aspects of the determination of
biphenyl hydroxylase activity in liver homogenates. 111. Influence of
administration of 2,6-dichloro-4-nitroaniline to rats, Exp. Mol.
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Casanova, M. and Dubroca, J. (1973)- Investigation of residues of
various fungicides used in the treatment of lettuce under glass. (In
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sprouts and beans. Report to Boots Pure Drug Go. (Australia) Ltd. May
1963.
Chamberlain, W.J. (1963b) - Fate of dicloran residues in beans. Report
to Boots Pure Drug Co. (Australia) Ltd. May 1963.
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dogs and pigs following repeated oral dosing at 100 mg/kg/day. Boots
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K.H. Jones, D.M. Sanderson and D.N. Noakes, Ibid. 7: 138, 1968.
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Shirasu, Moriya, Kato, Furuhashi and Kada. Mutagenicity screening of
pesticides in the microbial system. Mutation Res. 40, 19 (1976).
The Upjohn Company (1968) - Residue determinations for DCNA on peaches
before and after canning Report No. 212A-9760-1 to 10
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wine. Report No. (1969) 212-9760-5.
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fungicide 2,6-dicloro-4 nitroaniline. J. Agr. Food Chain. 22 (2)
221-224
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2,6-dichloro-4-nitroaniline in soil. J. Agr. Food Chem. 24, (3)
584-588.
Wright, W.M. (1968) - Dichloro-4-Nitroaniline. Residue Study in Milk
Cows. -The Upjohn Company Report No. 212B-9760-6. Dated December 10,
1968.
FAO/WHO (1975) 1974 evaluations of come pesticide residues in food.
AGP:1974/M/11; WHO Pesticide Residues Series# No. 4.