PESTICIDE RESIDUES IN FOOD - 1983
Sponsored jointly by FAO and WHO
EVALUATIONS 1983
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
Geneva, 5 - 14 December 1983
Food and Agriculture Organization of the United Nations
Rome 1985
DICHLOFLUANID
TOXICOLOGY
Explanation
Dichlofluanid was evaluated by the Joint Meetings in 1969, 1974,
1977, 1979, 1981 and 1982 (see FAO/WHO 1970, 1975, 1978, 1980, 1982
and 1983).1 A temporary acceptable daily intake (ADI) of 0 - 0.3
mg/kg body weight was established at the 1974 JMPR and extended at the
same level in 1977. The temporary ADI was based on the no-effect level
observed in a 2-year study in dogs at 25 mg/kg body weight. Further
work and information were required to elucidate the effects of the
possible accumulation in the thyroid of this organic fluorine
compound. The meetings in 1979 and 1982 did not consider dichlofluanid
and the temporary ADI was extended for a further year, pending
submission of the requested information.
Some information was available from Belgium, Finland, Norway, and
The Netherlands on use patterns, results of supervised trials,
residues in commerce and national maximum residue levels.
The additional data submitted to WHO and FAO have been reviewed
and are summarized in the following monograph addendum.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
TOXICOLOGICAL STUDIES
Special Studies on Mutagenicity
Dichlofluanid was tested for potential mutagenicity by the sister
chromatid exchange method in the bone marrow of male and female
Chinese hamsters. Cyclophosphamide was used as the positive control.
Groups of five male and five female Chinese hamsters were administered
doses of 1 000 and 2 000 mg/kg b.w. orally by intubation. The positive
control group received 20 mg/kg/b.w. of cyclophosphamide and the
negative control the suspension agent only (0.5 percent cremophor
emulsion). Animals were killed after 24h. Two hours before the
administration of the test substance, a tablet of 50 mg
5-bromo-deioxyuridine was implanted subcutaneously into each animal
and 2 h before sacrifice they received 4 mg/kg b.w. colchicin by
intra-peritoneal injection to arrest mitoses at the metaphase stage.
For each animal, 50 metaphases were examined and the incidence of
sister chromatid exchanges per metaphase was established. Wilcoxon's
non-parametric rank sum test was used for the statistical evaluation
of the results.
1 See Annex 2 for FAO and WHO documentation.
There were no indications of a mutagenic effect for doses up to
2 000 mg/kg/b.w., no biologically relevant increase in the SCE rate
was noted compared to the distinct mutagenic effects seen in the
positive control group (Herbold 1980).
Special Studies on Embryotoxicity
Rabbit
Groups of 15 inseminated Himalayan female rabbits were dosed
orally by gavage with 0, 10, 30, 100 mg/kg b.w, dichlofluanid from day
6 through day 18 of gestation. All dams survived and generally no
changes were observed.
The results demonstrated that pregnant rabbits tolerated oral
administration of 10 and 30 mg/kg dichlofluanid without evidence of
maternal toxicity. Administration of 100 mg/kg induced moderate
maternal toxicity as evidenced by weight loss, reduced food
consumption and premature delivery of two litters.
Administration of dichlofluanid at doses of 10 and 30 mg/kg did
not alter significantly the incidence of resorbed implantations among
the faetal population, indicating that the test compound was not
embryo-lethal. Neither of these doses, when administered during the
period of organogenesis, produced a faetotoxic response in rabbits; no
deleterious effects on faetal body weight, placental weight or weight
of gravid uteri were observed. In the 100 mg/kg dose group, the
weights of the gravid uteri, the number of implantation sites and live
foetuses were significantly lower in comparison with the control
group.
The higher incidence of the number of litters with anomalies in
the 30 or 100 mg/kg group was of no biological significance and was
not considered related to dichlofluanid, as these anomalies
occasionally occur spontaneously in this strain of rabbits.
In conclusion 30 mg/kg can be considered as the no-effect level
(NOEL) for maternal, embryotoxic and/or faetotoxic effects. No
teratogenic effects were noted (Parish 1982).
Special Study on Skin and Eye Irritation
Skin treatment in White New Zealand rabbits by dichlofluanid
produced slight irritation, not completely reversible after 72 h. When
placed in the conjunctival sac of the rabbit's eye, a moderate mucosal
irritation was observed (Pauluhn 1982).
Special Study on the Effect on the Thyroid
Rat
The dose-time effect relationship on the thyroid of dichlofluanid
was evaluated in groups of 80 male rats fed for nine weeks at dietary
concentrations of 0, 150, 500, 1 500 and 4 500 ppm. The animals showed
no alterations in appearance, behaviour or mortality that could be
related to the treatment during the entire period. Food consumption
was about 5 percent lower than the controls at 4 500 ppm. Body weight
did not differ significantly from the controls up to doses of 500 ppm.
In the 1 500 ppm group, body weights were significantly lower compared
to the control up to the third study week. Body weight gain was
slightly retarded in the 4 500 ppm group over the entire period.
Slight or significant differences from the controls were found in the
serum levels of calcium and inorganic phosphate in all dose groups,
but the values obtained were within the biological range for rats of
this age, confirming the lack of any effect on the parathyroids by
dichlofluanid. Iodine accumulation in the thyroid, both in respect of
percentage and concentration, was not affected up to 1 500 ppm. In the
4 500 ppm dose group, a significantly increased value was noted in the
first examination. At doses up to 1 500 ppm, the clinical-chemical
(T4) and radioimmunological (T3, T4) determination of the thyroid
hormone did not indicate any treatment-induced effects on the thyroid.
The significantly lower concentrations of both hormones in the 4 500
ppm group at two successive points (7 and 21 days) might be considered
a result of treatment and would point to a slight effect on the
synthesis and/or secretion phase of the thyroid. A permanent
decompensation of the thyroid control system was, however, not
detected. Gross pathology and histopathology produced no evidence of
treatment-induced damage of the thyroid in any of the dose groups.
Organ weights and subsequent histopathological examination did not
reveal any alterations in the adrenals during the treatment. The lower
liver weight at 4 500 ppm for 21 study days is considered a
consequence of the significantly lower animal weights. The higher
liver weights noted at the end of the study might be interpreted as
substance-induced. Histopathological examination did not reveal any
treatment-related alterations in the organs and tissues examined
(thyroid, liver, adrenal and skeletal musculature).
The NOEL was considered to be 500 ppm in the diet, corresponding
to 39.3 mg/kg b.w./day (Krötlinger & Luckhaus 1981).
Acute Toxicity
The symptoms and lethality of a 1:1 combination of the equitoxic
compounds dichlofluanid and captan were determined in an acute oral
toxicity test in rats. No significant additive effect was observed
(Mihail 1980). No synergistic effects were found when a single
combined dose of equitoxic doses of dichlofluanid and triadimefon was
administered orally to male rats (Mihail 1982).
Long-Term Toxicity
Mouse
Groups of 50 male and 50 female mice were fed dichlofluanid for
24 months in their diet at levels of 0, 200, 1 000 and 5 000 ppm. Ten
additional animals/sex/dose were used for laboratory tests; of these
animals, five/sex/dose were sacrificed and dissected after blood
samples had been taken, after six and twelve study months. During the
entire test period, no alterations in appearance, behaviour or the
mortality rate were noted when compared to the control group. Growth
was not affected in the groups up to 1 000 ppm but was significantly
retarded for both sexes at 5 000 ppm over the entire period. Specific
changes in haematological parameters were noted at the dosages
administered but the deviations were considered to be without
toxicological significance. Clinical chemistry, gross pathology and
histopathology did not reveal any indication of liver damage in any of
the dose groups. However, the raised alkaline phosphatase activity in
the 5 000 ppm group after 24 h of the study might be considered
treatment-related. This finding was an isolated one and not confirmed
in later tests. It may have been related to the observed bone
proliferation. Clinical chemistry provided no indications of a
treatment-induced effect on the kidney. Higher values for blood sugar
and cholesterol found at 5 000 ppm at the end of the study were,
however, within the physiological range. An increased thymus weight
was noted in males at the 5 000 and 1 000 ppm level. However, no
pathological alteration was observed and these differences were
therefore not treatment-related.
The bone proliferation detected in the femurs and/or ribs by
gross pathology and histopathology and the hardened crania on female
animals of the 5 000 ppm group can be considered as skeletal
alterations induced by the active ingredient. The findings of gross
pathology and histopathology noted in other organs provided no
indications of substance-induced organ damage. Doses up to 5 000 ppm
gave no indication of any significant dose-related increase in
location, types and total number of tumours. Therefore, in these
conditions, dichlofluanid was non-carcinogenic in the experimental
conditions employed.
The NOEL of dichlofluanid was 1 000 ppm, corresponding to 252
mg/kg b.w./day for male mice, or 273 mg/kg b.w./day for female mice
(Krötlinger and Löser 1982).
COMMENTS
The 1979 Meeting, which extended the temporary ADI for
dichlofluanid, required studies to elucidate the accumulation seen in
the thyroid. A study on rats, over a period of nine weeks,
investigated the dose/time relationship of the thyroid effect at dose
levels up to 4 500 ppm. Increased iodine uptake was observed early in
the study at 4 500 ppm, while decreases in T3 and T4 levels were noted
on days 7 and 21 of the study. The NOEL for the thyroid effects was
greater than 1 500 ppm. However, decreased body weight gain indicates
an overall NOEL of 500 ppm for the study.
Additional data evaluated included a sister-chromatid exchange
study which was negative at doses of 2 000 mg/kg, and a teratogenicity
study in the rabbit, which demonstrated embryotoxicity, but not
teratogenicity, at a dose level of 100 mg/kg b.w. A mouse long-term
carcinogenicity study did not indicate any evidence of oncogenicity at
dose levels up to 1 000 ppm in the diet.
Since all the requirements of the 1979 Meeting have been
satisfied the present Meeting was able to estimate an ADI.
TOXICOLOGICAL EVALUATION
Level Causing no Toxicological Effect
Rat: 500 ppm in the diet, equivalent to 30 mg/kg/b.w.
Dog: 1 000 ppm in the diet, equivalent to 25 mg/kg/b.w.
Estimate of Acceptable Daily Intake for Man
0-0.3 mg/kg/b.w.
FURTHER WORK OR INFORMATION
Desirable
Observations in humans.
REFERENCES - TOXICOLOGY
Herbold, B. Dichlofluanid - sister chromatid exchange on the Chinese
1980 hamster in vivo to evaluate for mutagenic effect. Report
9391 submitted to WHO by Bayer A.G., F.R.G (Unpublished)
Krötlinger F. & Loser, E. Dichlofluanid - chronic toxicological study
1982 on mice (including pathologic report by Newman, A.J. and
Wood, C.M.). Report No. 10810 submitted to WHO by Bayer
A.G., F.R.G. (Unpublished)
Krötlinger, F. & Luckhaus, G. Dichlofluanid - subchronic toxicological
1981 study to ascertain the dose time-effect relationship in the
effect on the thyroid. Report No. 10312 submitted to WHO by
Bayer A.G., F.R.G. (Unpublished)
Mihail, F. Dichlofluanid and captan - study for acute combination
1980 toxicity. Report No. 9388 submitted to WHO by Bayer A.G.,
F.R.G. (Unpublished)
Mihail, F. Dichlofluanid - study for acute combination toxicity.
1982 Report No. 11206 submitted to WHO by Bayer A.G., F.R.G.
(Unpublished)
Parish, H.M. Embryotoxicity study in rabbits with oral application of
1982 dichlofluanid. Report R2415 from the Institute of
Toxicology, Regensburg, submitted to WHO by Bayer A.G.,
F.R.G. (Unpublished)
Pauluhn, J. Dichlofluanid - study for primary skin and mucosa irritant
1982 effect. Report submitted to WHO by Bayer A.G., F.R.G.
(Unpublished)
RESIDUES
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
Dichlofluanid is registered for use in Finland (Finland 1983) on
apples (0.15-0.2 percent solution) and strawberries and currants (both
0.25 percent solution) and ornamentals. The waiting period is 14 days.
Dichlofluanid is approved in Norway (Norway 1983) for use on
stone fruits, berries, lettuce, onions, tomatoes, cucumbers and
ornamentals. Application rates are 50-125 g a.i./100 1 water. The
preharvest intervals are seven days for stone fruits and berries
(except strawberries), 14 days for onions and lettuce and four days
for cucumbers and tomatoes.
The Netherlands (1983) provided some new information on uses on
grapes (125 g/100 1, 6 weeks preharvest interval, PHI), eggplant (125
g/100 1, 3 days PAI; 75 mg/m2 of 7.5 percent dust as preventive, 3
days PHI) and zucchini (75 mg/m2 of 7.5 percent dust as preventive).
Information on a food survey taken in The Netherlands in 1981 and 1982
showed that most residues in 1981 were less than 2 mg/kg with only six
samples (currants (2), raspberry (3) and strawberry (1) out of 200
having residues above the maximum residue limit (MRL) of 5 mg/kg, with
a maximum of 6.7 mg/kg in currants). In 1982, five samples of currants
(4) and raspberry (1) had residues above the MRL, with a maximum of
32.7 mg/kg in currants. The method of analysis used was not stated.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Additional data was received from Norway on residues in
greenhouse tomatoes from five treatments at 10 to 14 day intervals,
using 0.75 g a.i./100 l. Residues determined at 2, 4, 6 and 8 days
after spraying ranged from 0.1 to 0.2 mg/kg after the first,
treatment, 0.4 to 0.5 mg/kg after the third treatment and 0.6 to 0.7
mg/kg after the fifth treatment. The method of analysis used was not
stated.
FATE OF RESIDUES
The hydrolytic stability of dichlofluanid was determined at pHs
4, 7 and 9 and at temperatures of 20°, 30° and 40°C. Decomposition was
rapid at pH 7, with only 25-30 percent remaining after 40 h. At pH 4,
47 percent remained after eight days at 30°, while 17 percent was left
after seven days at 40°. The hydrolysis constant at 20° and pH 7 was
7.5 x 10-6/sec (Wilmes 1982a).
About 1 mg of dichlofluanid was applied to a thin-layer plate and
exposed to artificial light for four weeks, at which time 30-42
percent of the original concentration remained. In aqueous solution
(2.6 mg/l) exposed to a mercury vapour lamp, dichlofluanid had a half-
life of about 10 h. In addition to the hydrolysis product
dimethylsulfanilid, an unidentified polar photoproduct was formed
(Wilmes 1982b).
RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION
Information was available from Belgium on the results of a survey
conducted over the years 1979-1982 for residues occurring in food in
commerce. Dichlofluanid never exceeded the Belgian tolerance of 5
mg/kg and was non-detectable in the range of 73-100 percent of the
samples. When present, it was found in a maximum of 27 percent of
samples at values not exceeding 0.8 mg/kg (Geloux 1983).
Surveys of domestic and imported food in commerce in Finland were
reported to the meeting (year unspecified). For domestic food, the
distribution and frequency is shown in Table 1 while Table 2 gives the
results for imported food. Again the analytical methodology employed
was not stated.
No residues were found in or on other fruits and vegetables. Only
15 samples of food (all strawberries) out of a total of 1 081 had
residues exceeding 1 mg/kg.
APPRAISAL
New information was received from Finland on permitted uses
(apples, strawberries, and currants, with a waiting period of 14
days). Surveys of domestic and imported food in commerce showed that
residues of dichlofluanid were rarely found, usually at less than 0.1
mg/kg, and only exceeded 1 mg/kg in 15 samples out of 1 081.
Information on the results of surveys of food in commerce in
Belgium covering the years 1979-1982 showed that dichlofluanid never
exceeded the local MRL of 5 mg/kg, with the maximum level found being
0.8 mg/kg. It was non-detectable in 73 to 100 percent of the samples.
Table 1. Dichlofluanid Residues in Domestic Commodities, Finland
Commodity No. Residue (mg/kg)
<0.1 0.11-1.0 1.1-2.0 >2.1
Strawberries 486 221 164 6 8
Currants 114 1 1
Gooseberries 15
Apples 129 2
Table 2. Dichlofluanid Residues in Imported Commodities, Finland
Commodity No. Residue (mg/kg)
<0.05 0.05 0.51 1.1->2.0 Max.
0.20 1.0 2.0
Cabbage
(chinese) 130 1 2 0.13
Plums 142 1 1 0.10
Strawberries 54 1 1 0.68
Brussels sprouts 11 1 0.17
Information on approved uses in Norway was available, where it is
permitted on stone fruits, berries, lettuce, onions, tomatoes and
cucumbers. The results of supervised trials on greenhouse tomatoes in
Norway, treated at recommended rates, gave a maximum residue of 0.7
mg/kg two days after a fifth biweekly treatment.
The Netherlands provided new information on uses on grapes,
eggplant and zucchini, along with data from their 1981 and 1982 food
surveys. Residues in excess of the MRL of 5 mg/kg occurred in about 3-
4 percent of the samples, mainly in currants and raspberries.
In all of the preceding submissions, it was not clear whether the
analytical method employed measured parent compound only or parent
plus metabolites. Only the procedure measuring dichlofluanid alone can
be properly used in evaluations.
Data from Germany was available on the results of hydrolytic and
photo stability tests. Decomposition in water at pH 7 and 20° was
rapid, with only 25-30 percent remaining after 48 h. Photodegradation
on a TLC plate resulted in 30-42 percent remaining after four weeks
exposure to artificial light. In aqueous solution, it had a photolytic
half-life of about 10 h.
RECOMMENDATIONS
All previous temporary MRLs are replaced by MRLs at the same
levels.
REFERENCES-RESIDUES
Finland. Information on uses of dichlofluanid in Finland.
1983
Norway. Information on uses of dichlofluanid in Norway. Data on
1983 residues in greenhouse tomatoes from supervised trials.
Netherlands. Information on uses and food surveys in The Netherlands.
1983
Wilmes, R., Behaviour of crop protection products in water. Bayer A.G.
1982a report PF-A/CE-PIQ-ENA. (Unpublished)
Wilmes, R., Orientating studies on stability to light. Bayer A.G.
1982b report PF-A/CE-PIQ-ENA. (Unpublished)
Geloux, M. Note technique du Central de Recherches Agronomiques de
1983 l'Etat, Gembloux, Belgique, No. 9/25, 9/26, 9/31 and 9/32,
Sept. 1979 - June 1982.