CHLOROTHALONIL JMPR 1977
Explanation
Chlorothalonil was reviewed by the 1974 Joint Meeting (FAO/WHO, 1975)
and the following information was required by 1977.
1. Additional studies to resolve lower limit for kidney effects in the
rat.
2. Determination of growth reduction in pups relative to dietary
ingestion or secretion into maternal milk.
3. Data on residues of chlorothalonil and the 4-hydroxy metabolite in
crops that may be fed to animals.
4. The results of feeding studies on dairy cattle, understood to be in
progress, to determine the level and nature of residues in milk and
tissues.
In addition, the following information was considered to be desirable.
1. Observation in humans.
2. Residue data for food moving in commerce.
3. Further information on the effects of processing, including
household cooking, on residues.
The Codex Committee on Pesticide Residues at its 9th session (Alinorm
78/24, paras. 144, 145) also asked the Joint Meeting to present the
residues levels and pre-harvest intervals in a more understandable
manner so that countries would be in a better position to judge the
data. Justification was requested for the suggested one day
pre-harvest interval for such crops as sugar beets, carrots and
potatoes.
A considerable amount of information was submitted by the principal
manufacturer concerning the specific requirements of the 1974 Joint
Meeting, which is reviewed below.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
BIOCHEMICAL ASPECTS
Single cows were fed either 250 ppm technical chlorothalonil, 2 ppm
pure 4-hydroxy metabolite of chlorothalonil, or normal diet for 44
days. A 15-day recovery period with all animals on normal diet
preceded sacrifice of the test animals. Milk production was reduced in
the cow receiving the 4-hydroxy-metabolite. Food consumption was
comparable in all animals. Neither test animal showed any gross
pathological lesions at sacrifice (IBT). No residues of chlorothalonil
were detected in either meat or milk. The 4-hydroxy metabolite
occurred in the milk of both test animals, being present as 23% of the
administered dose of the 4-hydroxy-metabolite, and as 0.2% of the
administered chlorothalonil dose (Ladd et al., 1971; Wolfe & Stallard,
1971). Further details are given in the section "Fate of Residues",
"In animals".
Degradation of chlorothalonil in cow bovine rumen fluid has been shown
to result in 4-5% of the administered dose of chlorothalonil being
converted to the 4-hydroxy metabolite in vitro (Duane, 1971).
TOXICOLOGICAL STUDIES
Special study on reproduction
Five groups of 10 male and 20 female rats were fed 0, 10, 50, 100 or
200 ppm 4-hydroxy-2,5,6-trichloroisophthalonitrile in a three
generation, one litter/generation reproduction study. Increased
irritability in adults in the Fo, F1 and F2 generations and rough
thin coats in weanlings of the F1, F2 and F3 generations were noted
at 200 ppm. Soft stools occurred occasionally at 100 and 200 ppm. Body
weight of offspring in all generations showed a decreased weight gain
at 50, 100 and 200 ppm, the decrease being marginal (10-15%) at 50
ppm. In post-weaning animals, body weight gain was decreased in
females of the Fo generation at 200 ppm. In other generations weight
gain was similar to controls, but the initial losses during weaning
were not recovered. Fertility index was reduced in the F2 parents at
100 and 200 ppm and in F1, parents at 200 ppm. Gestation index was
comparable in all groups. The viability index was normal for all
groups up to 24 hrs, decreased at 200 ppm in F2 and F3 and at 50
ppm in the F3 offspring over the 0-4 day period, decreased at 200 ppm
in the F2 and F3 and at 50 & 100 ppm in the F3 offspring over the
0-7 day period. After culling to 10/litter at 7 days, viability index
over the 7-14 day period was reduced at 200 ppm in all generation, and
at 100 ppm in the F3 generation. Total pup mortality was increased in
all generations at 200 ppm, at 100 ppm in the F2 and F3 litters, and
at 50 ppm in the F3 litters. A marginal increase also occurred at 10
ppm in the F3 litters.Litter size was reduced at 200 ppm in all
generations, and at 100 ppm in the F3 litters. Incidence of
stillbirths was comparable in all groups. Examination of pups from
F1, F2 & F3 generations either grossly or by alizarin staining did
not reveal terata (Hastings, 1975). Histopathological examination of
F3 weanlings (5 male and 5 female/group) did not reveal any
abnormalities (Ferrell, 1975).
Pups, culled at 7 days of age, were subject to analysis of stomach
content. No solid matter was found in the stomach. Levels of
4-hydroxy-2,5,6-trichloroisophthalonitrile increased with
increasing-dose level (Ferrel, 1975).
Short-term studies
Rat
Seven groups of 15 male and 15 female Young adult Wistar rats were fed
1, 2, 4, 15, 30, 60 or 120 ppm chlorothalonil in the diet for 17
weeks. A concurrent control group of 30 male and 30 female rats were
fed normal laboratory chow.
All rats were stated to present a healthy appearance throughout the
study. Body weight, food consumption and survival were comparable in
all groups. At termination of the study, all rats were sacrificed.
Kidney, liver and thyroid from each animal were removed and grossly
examined. Most kidneys had fat-like nodules on them and a number of
livers were mottled and discoloured (Hastings & Jessop, 1975). Kidney
histopathology did not reveal compound or dose-related changes (Busey,
1975).
COMMENTS
The data previously required from additional studies to resolve the
lowest dose limits for kidney effects in the rat and the determination
of growth reduction in pups relative to dietary intake or secretion
into maternal milk were submitted for consideration by the Meeting.
The absence of sufficient detail in the reports on kidney pathology
and discrepancies in body weight data in the rat reproduction studies
made evaluation of these data impracticable. However, since data have
been submitted in response to the previous request, the Committee
extended the current temporary ADI for humans for an additional 2
years.
TOXICOLOGICAL EVALUATION
Levels causing no toxicological effect
Rat: 60 mg/kg in the diet, equivalent to 3.0 mg/kg bw
Dog: 120 mg/kg in the diet, equivalent to 3.0 mg/kg bw
ESTIMATE OF TEMPORARY ACCEPTABLE DAILY INTAKE FOR HUMANS
0-0.03 mg/kg bw
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
As indicated by the 1974 Joint Meeting, chlorothalonil is a wide
spectrum fungicide effective against many fungus diseases of fruits,
vegetables, turf and ornamental crops. A very important use at present
is in tropical areas such as Central and South America and Southeast
Asia for protecting bananas from Sigatoka disease
(Cercospora musae), fruit spot and pitting disease, among others.
The compound is usually formulated as a 75% wettable powder and a 720
g/l suspension concentrate. Additional specific data on use patterns
were submitted by the Netherlands. (Table 1).
RESIDUES RESULTING FROM SUPERVISED TRIALS
The 1974 Joint Meeting made a comprehensive tabulation of the
available data on residues resulting from supervised trials with
chlorothalonil. Although the 9th session of the Codex Committee on
Pesticide Residues expressed its concern that the data presented could
not be readily understood, the absence of the original data sets does
not allow the reviewer to make any changes in the tabulation to make
it clearer. It also appears that the reservations expressed at the
CCPR were due to a misunderstanding since they concerned pre-harvest
intervals used in supervised trials, whereas the recommendations
mention pre-harvest intervals which were used as the basis of the
proposed maximum residue limits.
Additional residue data were provided by the principal manufacturer
for peaches and bananas. In both cases two types of extraction
were used, namely simple surface rinsing and the more exhaustive
total maceration. In the case of peaches the differences between
the two procedures were not significant (Table 2), so surface rinsing
was used to gather residue data from several locations in the
United States (Table 3). Occurence of the metabolite
2,5,6-trichloro-4-hydroxy-1,3-benzenedicarbonitrile (DAC-3701)
was low (Table 4).
In bananas, there also appears to be no significant difference between
the residue levels obtained by surface stripping and maceration (Table
5). Analysis shows that the fungicide remains mainly in the peel and
very little is translocated to the edible portion, as shown in Table
6. Formation of DAC-3701 is also minimal.
Residue data from the Netherlands on gherkins, leeks, potatoes and
wheat are shown in Table 7.
FATE OF RESIDUES
General comments
The only identified metabolite in the degradation of chlorothalonil is
the 4-hydroxy compound, DAC-3701, mentioned previously.
In animals
To determine whether or not dairy cattle fed with a diet containing
chlorothalonil and DAC-3701 will produce milk containing residues, a
study was done in which one cow was fed with 250 mg/kg of 97%
chlorothalonil and another with 2 ppm pure DAC-3701 for 44 days
followed by a 15-day recovery period (Ladd at al., 1971; Wolfe and
Stallard, 1971; referred to in the section "Biochemical aspects). Milk
samples were collected during the test and recovery
TABLE 1. Use pattern of chlorothalonil in the Netherlands
Crop or situation Kind of pest Extent of use/ Application Formulation Treatment Pre-harvest In use
controlled economic importance kg. a.i./ha interval since
(days)
potato Phytophthora small scale 1.5-2.2 w.P. 75T repeated ----- 1966
treatments
mushroom Verticillium small scale 3 g/m2 w.p. 75% first treatment 5 days 1977
sp. after covering;
repeat two
weeks later
after first
harvest
onion Botrytis small scale 2 kp/ha W.P. from 1 4 weeks 1976
squamosa 50% maneb June., repeat
25% every 7-10 days
chlorothalonil
potato Phytorphthora moderate 0.75-1 idem repeated ----- 1976
kg/ha treatments
Wheat powdery mildew moderate 1.2kg/ha w.p. 1 treatment, 6 weeks 1976
ripening diseases 40% sulfur repeated
20% maneb once, if
20% necessary just
chlorothalonil before blossoming
other uses: floriculture and against blue staining of wood
W.P. = wettable powder
TABLE 2. Chlorothalonil residues on peaches by surface and maceration extraction
Application Preharvest
Location Type of Formulation Rate Number interval, days Residues, mg/kg Mean
extraction
Louisiana Surface 720 g/l 1.0 pt. 10 7 2.51 3.55 10.08 5.65
suspension
concentrate
Macerate " 1.0 pt. 10 7 1.86 2.04 2.28 2.06
Surface " 1.0 pt. 10 7 1.76 2.32 1.88 1.99
Macerate " 1.0 pt. 10 7 1.14 0.92 1.60 1.22
Surface " 1.5 pt. 10 7 8.66 5.04 1.16 4.95
Macerate " 1.5 pt. 10 7 2.56 2.64 2.52 2.57
Arkansas Surface " 1.5 pt. 5 15 0.51 0.90 1.02 0.81
Macerate " 1.5 pt. 5 15 0.47 0.52 0.14 0.38
Surface " 1.5 pt. 9 7 4.50 2.66 0.75 2.64
Macerate " 1.5 pt. 9 7 0.24 0.60 1.73 0.86
Surface " 1.5 pt. 9 0 1.56 2.32 3.55 2.48
Macerate " 1.5 pt. 9 0 1.22 1.09 1.08 1.13
Georgia Surface " 1.5 pt. 4 14 0.71 1.13 1.50 1.11
Macerate " 1.5 pt. 4 14 0.80 0.91 0.84 0.85
Surface " 1.5 pt. 4 4 1.92 1.16 2.05 1.71
Macerate " 1.5 pt. 4 4 1.60 1.44 1.52 1.52
Surface " 1.5 pt. 4 1 2.86 2.37 1.80 2.59
Macerate " 1.5 pt. 4 1 1.83 1.80 1.80 1.81
TABLE 3. Residues of chlorothalonil on peaches 1/
Application Residue, mg/kg
Rate per 100 % a.i. Number Preharvest Samples Range Mean
gals.2/ interval analyzed
0 0 - 0 42 ND - 0.20 0.03
0.75 0.015 4 8 3 6.0 - 8.0 6.7
1.0 0.02 4 0 4 6.15 - 15.8 11.49
4-10 7-8 18 0.92 - 10.08 3.42
4 12 33 1.04 - 3.08 1.78
1.25 0.025 7 0 3 7.4 - 19.2 15.0
7 7 3 12.9 - 17.5 14.8
7 14 3 6.4 - 9.8 7.6
1.50 0.03 8-10 0 11 1.08 - 16.2 6.77
4 1-4 12 1.16 - 2.86 1.91
4-11 6-8 27 0.24 - 22.2 5.29
4-6 12-15 27 0.14 - 6.4 2.14
1.75 0.035 6-7 0 12 14.1 - 45.0 29.6
6 4 18 4.4 - 29.5 14.8
6-7 7 12 15.5 - 25.8 21.3
6-7 14 12 4.9 - 16.6 10.1
6 25 9 1.3 - 6.6 4.1
2.0 0.04 4 8 3 26.6 - 28.4 27.8
3.0 0.05 8 0 3 41.3 - 50.5 44.8
4 8 3 32.4 - 54.0 45.1
1/ Refers to both surface and macerated extraction data.
2/ Both using the 75%. w.p. and 720 g/l s.c. formulations.
TABLE 4. Formation of DAC-3701 on peaches treated with chlorothalonil.
Application 1/ Residues, mg/kg
% a.i. Number Preharvest Number Range Mean
interval analyzed
- 0 21 0.00 - 0.09 0.01
0.015 3 0 3 0.12 - 0.31 0.18
3 10 3 0.13 - 0.21 0.18
0.02 3 0 3 0.14 - 0.31 0.30
2-10 4 11 0.01 - 0.37 0.13
10 7 6 0.01 - 0.02 0.02
3-4 10-12 8 0.01 - 0.42 0.14
0.025 3-9 0 6 0.00 - 0.48 0.17
4 1-4 6 0.00 0.00
9-10 7 6 0.00 - 0.01 0.00
3-4 10-12 11 0.01 - 0.22 0.06
1/ Applied either as the W-75 or 6F
TABLE 5. Mean residues of chlorothalonil in whole
bananas using two extraction procedures.
Surface Striping Maceration
Treatment Chlorothalonil Chlorothalonil DAC-3701
(g a.i./1H2O)
0.75 0.03 0.02 ND
1.5 0.52 0.30 ND
3.0 1.49 1.32 ND
Control - 0.04 ND
TABLE 6. Distribution of chlorothalonil residues in bananas.
Treatment Chlorothalonil DAC-3701 Chlorothalonil DAC-3701
(g a.i./1H2O)
0.75 0.02 ND 0.09 ND
2.0 0.02 ND 0.22 ND
4.0 0.03 ND 3.80 0.01
Control 0.05 ND -- 0.01
TABLE 7. Residues of chlorothalonil in various crops (supervised trials, Netherlands).
Application Residues (mg/kg) at intervals (days) after application
Crop Year No. Rate Formulation 0/ 3 7 14 41 41 41
kg a.i./ha
Potato 1971 6/7 2.2 75% WP <0.02
(washed,
unpeeled
potatoes)
Leek 1971 11 1.5 75% WP 13 7.7
(11-16) (4.8-9.9)
Gherkin 1973 1 2.2 75% WP unwashed unwashed
(glasshouse) 4.1 0.83
(2.9-5.4) (0.64-1.13)
washed washed
1.2 0.30
(0.9-1.7) (0.24-0.37)
Wheat 1974 2 1.2 75% WP whole
kg/ha in ear
combination 0.52
with 2.4 kg (0.36-0.94)
sulphur and
1.2 mg maneb
1974 2 " 75% WP 0.46
(0.27-0.93) Whole bran
grain
1976 1 " 75% WP 0.37-0.78 0.04-0.06 1.5-3.4
TABLE 8. DAC-3701 residues in milk of cows fed chlorothalonil or DAC-3701.
DAC-3701, mg/kg, in milk of
Test Period Control Chlorothalnil-fed DAC-3701 fed
Cow Cow
(250 PPM in diet) (2.0 ppm in diet)
Pre-test 0.05 0.05 0.05
2 0.05 0.10 0.19
4 0.04 0.27 0.19
8 0.04 1.30 0.75
16 0.04 0.62 0.66
18 0.09 0.84 0.94
20 0.01 0.96 1.54
22 0.01 0.92 0.96
26 0.10 1.19 1.27
30 0.13 0.94 1.12
32 0.02 0.97 0.90
34 0.01 0.83 1.26
38 0.01 1.00 0.95
44 0.01 0.59 1.16
Recovery Period
1 0.01 0.60 1.30
3 0.01 0.42 1.10
6 0.04 0.37 0.90
10 0.06 0.23 0.56
15 0.04 0.19 0.32
period. The animals were then milked and samples of liver, kidney,
muscle and fat were analyzed.
No chlorothalonil was detected in the milk of the cow fed with
chlorothalonil but DAC-3701 was detected in the milk of both cows
(Table 8). Only 0.2% of the ingested chlorothalonil was eliminated in
the milk as DAC-3701. Residues of the metabolite became constant after
about 18 days of treatment but declined rapidly during the recovery
period. In the tissues, no residues of either compound could be
detected in the muscle or fat but 0.7 and 1.2 mg/kg of DAC-3701 were
detected in the kidneys of the chlorothalonil- and DAC-3701- fed cows,
respectively. Traces (0.1 mg/kg) of DAC-3701 were found in the liver
of the cow fed with DAC-3701.
In silage
The effect of ensiling treated foliage is important in view of its
probable effect on the residue levels in milk or meat of animals
consuming the silage as feed. This is particularly important with
chlorothalonil since residues are expected to remain in the treated
plant material prior to ensiling. On the other hand, chlorothalonil is
biodegradable and this could minimize residue levels. This latter
observation was borne out by ensiling studies which showed that with
corn silage, 90% degradation was observed after 18 days (from 30 mg/kg
to 3 mg/kg) and the half-life was approximately 4 days. No formation
of DAC-3701 was observed. In a second experiment in which the bound
materials in the silage were converted to an extractable form,
DAC-3701 constituted only 2% of the chlorothalonil in the silage on
the first day of ensiling.
During processing
The 1974 Joint Meeting reported the effect of washing with water on
chlorothalonil residues. For the present Meeting, the principal
manufacturer submitted the results of studies of the effect on
residues of processing tomatoes and peaches. For tomatoes, it was
shown that 94% of the chlorothalonil residues were removed by washing
fresh tomatoes and that no detectable chlorothalonil or DAC-3701 was
found in the products canned tomato pulp, tomato paste or tomato
juice. The dry cannery waste (tomato pomace), which is sometimes used
for feed, contained less than 1 mg/kg of total residues at roughly a
6:1 chlorothalonil:DAC-3701 ratio.
Washing peaches with water followed by a caustic wash removed 97% of
the field residues remaining on the peaches. The caustic wash will
increase chlorothalonil removal because chlorothalonil is unstable at
pH 10 and above. No chlorothalonil or DAC-3701 could be detected in
canned peach puree.
RESIDUES IN FOOD MOVING IN COMMERCE
No data were made available but the principal manufacturer mentioned
that this could be supplied by the United States Food and Drug
Administration, presumably through the Chairman of the U.S. Delegation
to the Codex Committee on Pesticide Residues.
APPRAISAL
The compound was re-evaluated in the light of information requested by
the 1974 Joint Meeting and the decision of the 1977 Codex Committee on
Pesticide Residues to change the temporary maximum residue limit in
oranges to encompass all citrus fruits. The 1974 Meeting recommended a
maximum residue limit of 30 mg/kg in peaches, but the principal
manufacturer suggested that this could be reduced to 25 mg/kg.
Supporting data, mainly from the United States, justifies such a
reduction. In bananas, the fungicide remains mainly in the peel.
When dairy cows were fed diets containing very high levels of
chlorothalonil or 2,5,6-trichloro-4-hydroxy-1,3-benzocarbonitrile
(DAC-3701), approximately 0.2% of the chlorothalonil and 23% of the
DAC-3701 were eliminated in the milk as DAC-3701. Of the tissues
examined, only the kidneys contained residues above the limit of
determination.
After being ensiled for 18 days, maize forage was found to contain 10%
of the initial residues.
Washing removed up to 94% of the chlorothalonil residues in tomatoes
and up to 97% in peaches and residues could not be detected (< 0.01
mg/kg) in tomato and peach processing products.
RECOMMENDATIONS
The temporary maximum residue limits recommended in 1974 are
maintained as temporary limits with the exception of that for peaches
which is lowered and for "oranges" which is changed to "citrus fruit".
An additional temporary limit is recommended for bananas.
Commodity Limit, mg/kg
Peaches 25
Citrus fruit 5
Banana (whole) 4
Banana (pulp) 0.1
FURTHER WORK OR INFORMATION
Required (before July 1979)
1. Additional studies to resolve the lower dose limits for kidney
effects in rats.
2. Studies to define the growth reduction after administration of
chlorothalonil or its metabolite 4-hydroxy-2,5,6-trichloroisothalonile
in pups relative to ingestion or secretion into milk.
Desirable
1. Observations in humans.
2. Information on the extent of metabolism to
4-hydroxy-2,5,6-trichloroisothalonile in mammals.
3. Information on the effects of cooking on residues.
REFERENCES
Busey, W.M. (1975) Project 24-201. Unpublished Report by Experimental
Pathology Laboratories Inc. submitted to WHO by Diamond Shamrock Corp.
Duane, W.C. (1971) Reinvestigation of the degradation of
Chlorothalonil by Bovine Rumen Fluid. Unpublished Report submitted to
WHO by Diamond Shamrock Corp.
Ferrell, J.F. (1975) Pathology Report on F3 Rats. Unpublished Report
by Experimental Pathology Laboratories Inc. submitted to WHO by
Diamond Shamrock Corp.
Hastings, T.F. (1975) Three generation Reproduction Study in Albino
Rats DAC-3701. Unpublished Report by Bio/Tox Research Laboratories
Inc., submitted to WHO by Diamond Shamrock Corp.
Hastings, T.J. and Jessop, D.C. (1975) 4-Month Dietary Toxicity Study
- Rats. Chlorothalonil. Final Report. Unpublished Report by Bio/Tox
Research Laboratories Inc. submitted to WHO by Diamond Shamrock Corp.
Ladd, K., Jenkins, D.H. and Kepplinger, M.L. (1971) Meat and Milk
Residue Study with Technical Daconil 2787 - 97% and pure DAC-3701 in
Dairy Cattle. Unpublished Report by Indistrial Biotest Laboratories,
submitted to WHO by Diamond Shamrock Corp.
Wolfe, A.L. and Stallard, D.E. (1971) Supplementary Milk and Meat
Study. Unpublished Report submitted to WHO by Diamond Shamrock Corp.
FAO/WHO (1975) 1974 evaluations of some pesticide residues in food.
AGP:1974/M/11; WHO Pesticide Residues Series, No. 4.