PESTICIDE RESIDUES IN FOOD - 1979
Sponsored jointly by FAO and WHO
Joint meeting of the
FAO Panel of Experts on Pesticide Residues
in Food and the Environment
WHO Expert Group on Pesticide Residues
Geneva, 3-12 December 1979
Chlorothalonil was evaluated in 1974. In 1977 it was reviewed in the
light of information received in response to needs recorded in 1974,
also in response to requests for clarification of the past
recommendations received from the 9th Session of CCPR.
In 1977, temporary MRLs for whole and pulp of bananas were suggested
on a basis of a minimum of acceptable data. Since then the results
from field trials involving revised patterns of use have been
The 1977 Meeting also recorded requirements for additional information
(i) to resolve the lower dose limits for kidney effects in rats, and
(ii) to define the growth reduction after administration of
chlorothalonil or its metabolite,
4-hydroxy-2,5,6-trichloro-isophthalonitrile (DAC-3701) in pups
relative to ingestion or secretion into milk.
Information was also considered to be desirable on (i) observations in
humans, (ii) the extent of metabolism to
4-hydroxy-2,5,6-trichloroisophthalonitrile (DAC-3701) in mammals, and
(iii) the effects of cooking on residues.
The further information received is reviewed in this monograph
EVALUATION FOR ACCEPTABLE DAILY INTAKE
Two groups of 4 male Sprague-Dawley rats, 9 weeks of age, were
intubated (following overnight fasting) with polyethylene glycol 400
solutions of <99 percent pure
14C-hydroxy-2,5,6-trichloroisophthalonitrile (DAC-3701) at dosage
levels of 4.3 or 42.6 mg/kg body weight. The 14C label was believed
to be evenly distributed in the phenyl ring. Following dosing, rats
were maintained individually in metabolism cages. Urine, faeces and
cage washings were obtained every 24 hours until execution for tissue
analysis at 96 hours post-dosing. Cumulative percentage recovery of
administered 14C in faeces and urine was unaffected by dose level.
However, faecal levels were approximately 10 times greater than
urinary levels. At 96 hours, approximately 78% of the administered
dose had been recovered in feces (about 70 percent) and urine (about 8
percent). Excretory half-life was about 48 hours. Residues of
14C/gm of tissue was highest in the large intestine (27 and 384 ppm
equivalents), followed by small intestine (14 and 161 ppm), liver (17
and 139 ppm), and blood (4 and 41 ppm) following 4.3 and 42.6 mg/kg
doses. Low levels were found in all other tissues analyzed. Total
accountability of 14C was approximately 1O2% at both does levels.
The data are suggestive of hepatic conjugation and biliary excretion
of the 14C-labelled test material (Jarrett, et al., 1978).
Special Studies on Carcinogenicity
Groups of 50 male B6C3F1 mice were fed chlorothalonil (98 percent
purity technical material) at either 10,000 ppm for 2 weeks followed
by 2,500 ppm for 78 weeks, and a pre-sacrifice withdrawal period of
11-12 weeks (time-weighted average dose 2,688 ppm) or 20,000 ppm for 2
weeks followed by 5,000 ppm for 78 weeks and a 12 week pre-sacrifice
withdrawal period (time-weighted average dose 5,375 ppm). Similar
groups of female mice were fed either 10,000 ppm for 2 weeks, 5,000
ppm for 10 weeks, and 2,500 ppm for 68 weeks, with an 11 week
presacrifice withdrawal period (time-weighted average dose, 3,000
ppm), or 20,000 ppm for 2 weeks, 10,000 ppm for 10 weeks, and 5,000
ppm for 68 weeks, with a 12 week presacrifice withdrawal period
(time-weighted average dose, 6,000 ppm). Matched controls comprised
10 male and 10 female mice were maintained for 91 weeks.
A dose related decrease in body weight gain in males was observed.
Survival, gross, and histopathology were comparable in all groups.
Total incidence of male mice with tumors was 30, 18, and 2 percent at
control, low, and high dose levels. Malignant tumor incidence was 20,
4, and 2 percent and benign tumors incidence was 10, 12.5, and 0
percent. Comparable percentages in females are total tumors, 30, 12,
and 17 percent, malignant tumors, 0, 6, and 8 percent, and benign
tumors, 30, 6, and 8 percent in control, low, and high dose levels,
respectively. There was no evidence of change in tumor incidence in
specific organs or organ systems (NCI, 1978).
Groups of 50 male and 50 female Osborne-Mendel rats were dosed with
chlorothalonil (technical 98 percent purity, technical 98.5 percent
purity, or analytical grade, pure material) at dose levels of either
10,000 ppm for 1 week, followed by 5,000 ppm for 79 weeks and a 30
week presacrifice withdrawal period (time-weighted average dose, 5,063
ppm) or 20,000 ppm for 1 week followed by 10,000 ppm for 79 weeks and
a 31 week presacrifice withdrawal period (time-weighted average dose,
10,126 ppm). Contemporary control groups comprised of 10 male and 10
female rats were maintained for 110 weeks.
Body weight data showed a dose-related decrease in weight gain in both
sexes. During the second year of the study, treated rats showed
ataxia, tachypnea hematuria, hyperactivity, vaginal bleeding, a high
incidence of abscess formation and bright yellow urine. Survival was
decreased in both male test groups. The report indicates the only
non-spontaneous pathological lesions noted were a dose-related
increase in renal tubular epithelial tumors in both sexes.
(Unfortunately, the test and tabular data in the report differ with
regard to the incidence of renal tubular epithelial tumors, rendering
an evaluation impossible.) The tabular data does not indicate any
cause for concern regarding renal tumor incidence (NCI, 1978).
A detailed review of the available data on the NCI bioassay indicates
that the tabular data on incidence of renal tubular epithelial
neoplasms appears to be correct. No reported tumors were noted in the
pituitary, where the incidence of adenomas was, in males 0/8, 5/45,
and 0/49, and in females 0/10, 3/47, and 3/42 in control, low, and
high dose groups. Similar errors were found in the reported incidence
of adrenal adenomas, where in the females, the original report
indicated 1/10, 0/47, and 0/47, the corrected data indicating 1/10,
9/47, and 9/47 (Weinberg, 1979).
Short Term Studies
Seven groups of 15 male and 15 female young adult Wister 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 elated 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 was removed and grossly
examined. Most kidneys had fat-like nodules on them, and a number of
livers were mottled and discoloured (Hastings and Jessop, 1975).
Histopathology of the kidney has been reported in detail, and although
interstitial nephritis and regenerative epithelium were noted, no dose
or compound related effects were observed (Busey, 1975). A second
examination of the slides of kidney tissue confirmed the absence of
dose or compound related effects (Newberne, 1975).
A previous Meeting requested additional data which, in part, were made
available and reviewed by this Meeting. A detailed histopathology
review of the previous study, by two independent pathologists,
alleviated the concerns of the previous Meeting on potential kidney
effects. Information on pup growth reduction requested by a previous
meeting is still lacking, but information was available to indicate
that a new 3-generation study is underway. The conflicting data
available from the rat carcinogenicity bioassay, especially with
regard to the incidence of renal tubular epithelial tumors, and of
adrenal adenomas precluded a full evaluation of these data. The
Meeting agreed to extend the temporary ADI for two years.
Level Causing No Toxicological Effect
Rat: 60 ppm in the diet equivalent to 3 mg/kg body weight.
Dog: 120 ppm in the diet equivalent to 3 mg/kg body weight.
Estimate Of Temporary Acceptable Daily Intake For Man
0-0.03 mg/kg body weight
RESIDUES IN FOOD AND THEIR EVALUATION
Chlorothalonil is proposed for use to control foliar diseases of
bananas and plantains, primarily by low volume aerial applications of
a flowable formulation containing 54% a.i. or a wettable powder
containing 75% a.i. This use pattern will result in some applications
being made to fruiting plants, however it is common practice to place
plastic bags over the developing stems to protect the fruit until
harvest. Since this agricultural practice is established in 80% or
more of the commercial banana growing areas of the world it will be
described in some detail as follows.
In 1977, two experiments on bananas were carried out in the
Philippines and one in Honduras. In the first Philippine experiment,
banana trees received three applications a month for five months
followed by two applications per month for six months for a total of
twenty seven applications at a rate of 1.75 kg (1.31 kg a.i.) Daconil
2787 W-75/ha/application. On or about April 2, the banana fruit were
covered by plastic bags as is the cultural practice in the area of the
field tests. The last six applications were made after the bananas
were bagged. On June 18, following that day's spray application,
fruit for residue determination were collected.
In the second Philippine experiment, banana trees received nine
applications of Daconil 2787 W-75 at a rate of 1.5 kg
a.i./ha/application. The test period lasted 191 days and some banana
fruit stems were covered with plastic bags and some left uncovered.
Samples for analysis were taken on the day of the final spray
application from both bagged and unbagged stems.
In the Honduras experiment banana trees received twelve applications
of BRAVO 6F at a rate of 1.5 pounds a.i./acre/application over the 103
day test period for a total of 18 lbs. a.i./acre. In the test, some
of the banana fruits were covered with plastic bags according to the
cultural practice in the area. On the day of the twelfth application
replicates consisting of four stems of bagged and four stems of
unbagged green bananas were harvested for analysis.
Uses on various crops in New Zealand
New information on use pattern was received from New Zealand which
replaces that previously published in 1974 and 1977 (New Zealand,
Table 1. Uses of Chlorothalonil in New Zealand
Crop/Disease Application Rate Preharvest
Potatoes/early blight 0.8-1.3 kg ai/ha 7 days
Beans/anthracnose 1.2-1.7 kg ai/ha 7 days
Brassicas/rust 1.2-1.7 kg ai/ha 7 days
Celery/downy mildew 150-200 g ai/100 litres 7 days
Cucurbits/leaf spots 150-200 g ai/100 litres 1 day
Lettuce 150-200 g ai/100 litres 14 days
Use on peanuts in South Africa
The Republic of South Africa supplied information on the registered
use (Oct. 36/1947) of chlorothalonil on groundnuts (peanuts) for the
control of leaf diseases of great economic importance (S. Africa,
1979). The information used is WP 75% at 1125 g/ai/ha with a
withholding period of 56 days for peanut foliage as fodder.
Use on potatoes in Sweden
Information was received from Sweden that chlorothalonil is used in
that country mainly against potato blight (Phytophtera) (Sweden,
1979). Since the pre-harvest interval for the bisdithiocarbomates was
extended from 1 to 4 weeks, chlorothalonil with a withholding period
of only 1 week has come to be used for the last fungicide application
before potato haulm desiccation and harvest. Chlorothalonil is also
used against disease (Alternaria and Erysiphe) on cucumber
(withholding period 2 days), and Botrytis on ornamentals in
glasshouses. Formulations: WP 75% (in glasshouses, however, as a 20%
fumigant) at a rate of application of 1.2-1.5 kg/ha.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Some of the bananas obtained during the experiments referred to under
`Use Pattern' were analysed green as harvested, others after ripening
with ethylene in the laboratory. They were also examined before and
after placement in a washing tank and treatment for 15 minutes with
400 ppm a.i. thiabendazole flowable and 1% alum according to common
commercial practice. Whole fruit, edible pulp and surface extractions
were examined from each handling and treatment level and 6 to 8
replicate analyses were undertaken on each sample of treated bananas.
In Philippine experiment (1) no residue equal or greater than 0.02
mg/kg was found on washed or unwashed green whole bananas, or edible
pulp from green bananas, washed or unwashed ripe whole bananas or
edible pulp from ripe bananas. Treated and nontreated samples gave
identical results. In Philippine experiment (2), unbagged whole fruit
from treated areas contained a maximum chlorothalonil residue of 0.11
mg/kg (mean, 0.04 mg/kg). Post-harvest washing reduced the mean value
from 0.04 to 0.01 mg/kg. Bananas protected by plastic bags during
treatment contained no residue of chlorothalonil above 0.01 mg/kg and
no detectable residue of DAC-3701. The levels of chlorothalonil
obtained by macerated extraction were comparable to those obtained by
surface stripping. Edible pulp from treated bananas contained no
residues of chlorothalonil or DAC-3701 at the detection limit of 0.01
mg/kg. In the Honduras experiment, unwashed bananas from unbagged
plots had a maximum residue of 0.17 mg/kg with a mean of 0.08 mg/kg
which was reduced to 0.02 mg/kg by washing. No DAC-3701 residues
greater than 0.01 mg/kg were found in any samples including the edible
pulp. No chlorothalonil residues greater than 0.01 mg/kg were found
in edible pulp.
In Ontario, Canada, chlorothalonil (as Bravo 5F) was applied to onions
(var. Autumn spice) at 1.6 kg ai/ha (3.25 L product in 561.1 L
water/ha) by a 16-nozzle sprayer in a single spray with the following
results (Canada, 1979):
Table 2. Residues following spraying onions (Ontario)
application chlorothalonil DAC-3701
0-before spray ND (< 0.05) ND (<0.002)
0-after spray 13 0.24
2 7.7 0.15
4 5.8 0.03
6 2.7 0.01
8* 1.4 0.003
10-older outer leaves 2.4 0.008
10-all leaves* 1.5 0.01
10-younger leaves 0.51 0.005
14 0.93 0.005
15 2.2 0.01
22 0.29 ND (<0.002)
The chlorothalonil residues decayed with a half-life of about 3 days
while the 4-hydroxy metabolite (DAC-3701) was fairly constant at about
0.5% of the total residue. Selection of 10% of the initial fungicide
as an unacceptable level suggest a 7-10 day protection period.
In two experiments in Ontario, chlorothalonil was applied to grapes at
1.3-1.9 kg ai/ha as either 7.2 F or 500 F flowable or 75% WP
formulations for 3-6 applications in one case or a single late season
application of WP in the second case (Canada, 1979). Harvest residues
on grapes 46 days-post-spray were 0.8 mg/kg for 6 applications and 0.6
mg/kg for 3 applications for the 75% WP. The flowable formulations
gave 1.0 and 3.3 mg/kg for 6 applications and 2.5 and 1.7 mg/kg for 3
applications. Residues of DAC-3701 were 0.006 mg/kg (6 applications)
and 0.002 mg/kg (3 applications) for the WP whereas the flowable
formulations gave 0.014 and 0.017 mg/kg (6 applications) and 0.008
mg/kg (3 applications). An August application of the WP degraded
slowly from 7.5 to 4.9 and 3.1 mg/kg after 7 and 14 days respectively
and remained at 1.6-2.5 mg/kg between 21 and 36 days post-spray. The
4-hydroxy metabolite residues declined from 0.09 mg/kg to 0.013 over
about the same period. Although some mild phytotoxicity was noted for
the flowable formulations, the possible use of such grapes for wine
indicated that the higher residue levels associated with these
treatments should be considered for recommending maximum residue
* mean of 2 sample replicates.
Potatoes, Tomatoes (New Zealand)
Information on supervised trials from New Zealand showed that potatoes
treated 10 times at 1.7 kg ai/ha with a preharvest interval of 6 days
had non-detectable (20-5 mg/kg) residues (New Zealand, 1979).
Tomatoes treated 5 times with 180 g ai/100 litres (1.5 kg ai/ha) had
residues of 11.4, 2.8, 0.9, N.D., and N.D. at preharvest intervals of
1, 3, 7, 10 and 14 days respectively.
Peanuts (South Africa)
Information from South Africa on residues on peanut foliage (leaves)
following treatment by 4 applications at 10 day intervals at a rate of
1125 g ai/ha is shown in the following table (South Africa, 1979).
Table 3. Residues on peanut foliage (South Africa)
Days after chlorothalonil DAC-3701
last treatment mg/kg mg/kg
0-1 57.5:55.0 0.5:0.5
0 77.5:80.0 0.7:0.8
1 68.0:74.0 0.6:0.6
7 39.0:47.0 0.3:0.4
14 20.5:25.0 0.3:0.2
28 7.0:8.5 0.2:0.3
Recovery at 5 mg/kg = 80% for chlorothalonil and 70% for DAC-3801.
Limit of detection = 0.1 mg/kg.
FATE OF RESIDUES
Since hexachlorobenzene (HCB) can and does occur as a manufacturing
impurity in chlorothalonil, the question arises as to the extent of
its occurrence in the residue spectrum of chlorothalonil. Information
from the manufacturer indicates that specifications permit no more
than 0.02% in W-75 wettable powder. At a typical application rate of
1.5 kg a.i./ha this would result in approximately 0.3 g of HCB per
hectare per application. Since the agricultural practice on bananas
could result in as many as twenty-seven applications, a total
calculated HCB residue of 8.1 g/ha is theoretically possible assuming
no losses by volatilization or rain wash-off. However, since HCB is
not systemic, any traces of residue would occur on the peel where it
could be largely removed by the usual washing process and would not
occur in the edible pulp. The situation with respect to other
commodities requiring a multiplicity of applications merits
In storage and processing
The effects of cooking on chlorothalonil and DAC-3701 were
investigated using plain water, green beans, and tomatoes in four
cooking techniques. Fifty gram samples of water, chopped green beans,
and tomatoes were each fortified with 14C-chlorothalonil and cooked
for 10 minutes in a vessel containing 20 ml of boiling water. The
cooking methods were: (1) in a 600 ml beaker without a cover, (2) in a
500 ml flat bottomed flask fitted with a reflux condenser, (3) in a
500 ml flat bottomed flask fitted with a distillation column and an
acetone trap cooled in dry ice/acetone, (4) in a 6 qt. pressure cooker
with and without a tightly sealed cover. A similar group of test
samples were also fortified with 14C-DAC-3701 and subjected to
cooking methods (1) and (4). After using appropriate extraction and
cleanup procedures, the residues were quantitated by liquid
scintillation counting and characterized by thin layer chromatography
and autoradiography. Separate tests without cooking gave complete
recovery of the fortified 14C-radioactivity under all test conditions
indicating that the extraction and partition procedures were reliable.
The results of the cooking experiments are shown in Tables 4, 5 and 6.
For all three test samples, cooking under open conditions resulted in
volatilization of chlorothalonil (94-98% loss) whereas cooking under
closed conditions resulted in partial hydrolysis to DAC-3701 and
either 3-cyano-2,4,5,6-tetrachlorobenzamide (water) or unidentified
residues (tomatoes and beans). Only chlorothalonil was found in the
distillate. Pressure cooking without a cover resulted in loss of a
major portion of the chlorothalonil through volatilization. However,
with the cover tightly sealed (15 Psi), the major portion of the
chlorothalonil remained unchanged and no significant amounts of
DAC-3701 were detected. The later result is postulated to be due to
instant sublimation which prevented hydrolysis. The parallel
experiments with 14C-DAC-3701 indicated that DAC-3701 is stable and
neither chemical change nor loss will occur during cooking.
In the previously described experiments in Canada (see "Residues from
Supervised Trials"), the effect of 3- and 6-spray programmes of 3
formulations of chlorothalonil on carry-over of residues into grape
juice are shown in table 7 (Canada, 1979).
Table 4. Effect of cooking on 14C-chlorothalonil with water
14C-Chlorothalonil Recovery of 14C-radioactivity (dpm)
Fortified Organic Aqueous
Sample (dpm) Phase Phase Distillate Total Loss, %
Open beaker 1,000,000 29,400 2,700 - 32,100 96.8
Reflux 1,000,000 987,160 7,335 - 994,495 0.6
Distillation 1,000,000 800,400 10,500 200,500 1,011,400 0.0
Table 5. Effects of cooking on 14C-chlorothalonil with tomatoes
14C-Chlorothalonil Recovery of 14C-radioactivity (dpm)
Fortified Organic Aqueous
Sample (dpm) Phase Phase Distillate Total Loss, %
Open beaker 1,400,000 20,500 7,065 - 27,565 98.0
Reflux 1,000,000 797,100 346,430 - 1,041,160 0.0
Distillation 1,000,000 805,600 14,600 107,100 927,300 7.3
Table 6. Effects of cooking on 14C-chlorothalonil with green beans.
14C-Chlorothalonil Recovery of 14C-radioactivity (dpm)
Fortified Organic Aqueous
Sample (dpm) Phase Phase Distillate Total Loss, %
Open beaker 1,400,000 59,000 27,420 - 86.420 93.8
Reflux 1,000,000 772,080 269,080 - 1,041,100 0.0
Distillation 1,000,000 786,000 7,200 160,000 953,200 4.7
Table 7. Residues in Grapes and Juice (Canada)
Formulation Grape berries, mg/kg Grape juice, mg/kg
and program chlorothalonil DAC-3701 chlorothalonil DAC-3701
Full season: 6 applications
75 W.P. 0.3 <0.002 0.3 0.0005
7.2 F 0.8 0.006 0.7 0.0005
500 F 1.6 0.008 0.9 0.002
Late season: 3 applications
75 W.P. 0.2 <0.002 0.3 <0.0005
7.2 F 0.7 0.011 0.8 <0.0005
500 F 0.6 0.006 0.2 0.004
Check <0.002 <0.002 <0.001
EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION
Chlorothalonil is detectable by the analytical methods employed for
the Total Diet Study conducted in the United States by the Food and
Drug Administration. During the 1976 and 1977 periods, no residues of
chlorothalonil were detected at a sensitivity of slightly less than
0.01 mg/kg (Weasel, 1979).
Finland and Sweden
In the course of monitoring of imported produce during 1978 (Finland,
1979), several lots of imported fruits, vegetables, and rootcrops were
analysed with detectable residues only in the following cases:
strawberries, 3 samples, 0.02-0.15 mg/kg; chinese lettuce, 6 samples,
0.01-0.86 mg/kg; peaches, 2 samples, 0.12-1.2 mg/kg. In Sweden,
thirty-four samples of Swedish potatoes were analysed during 1979
(Sweden 1979). No sample contained detectable levels (0.005 mg/kg) of
METHODS OF RESIDUE ANALYSIS
A specific GLC method for chlorothalonil and its major metabolite,
4-hydroxy-2,5,6-trichloroisophthalonitrile (DAC-3701) in soil, water,
green leafy vegetables, tomatoes, and dry oily crops such as soybeans,
dry beans, and peanuts has been developed and published (Ballee,
1976). Recoveries ranged from 85-100% for both compounds at a
sensitivity level of 0.01 mg/kg.
The method of analysis used in the field trials on bananas (Diamond
Shamrock, 1979a) was essentially the same as that reported in the
initial evaluation of chlorothalonil (FAO, 1975) differing only in
details such as the composition of the Florisil eluting mixtures used
- 20% dichloromethane in hexane (Eluent A) and 50% dichloromethane,
1.5% acetonitrile, 48.5% hexane (Eluent C) instead of 5% acetone, 95%
dichloromethane for chlorothalonil and 50% acetone, 50%
dichloromethane for DAC-3701 - and in the use of
1-n-propyl-3-p-tolyltriazene to form the propyl ether of DAC-3701
instead of diazomethane to form the methyl ether. Although the
propylated DAC-3701 has desirable GLC properties, its use cannot be
recommended due to toxicological hazards associated with the
derivitizing agent which has led to its general lack of availability.
The original recommended procedure using diazomethane is therefore
still the method of choice for determining DAC-3701. As the data
herein shows, there is no significant difference in residue results
obtained on whole bananas either by surface stripping or by
maceration; due to the additional cleanup required when maceration is
used the surface stripping technique is preferred. The mean recovery
for whole bananas was 93% for chlorothalonil and 84% for DAC-3701; on
macerated whole bananas the figures were 72% and 83% respectively. The
mean recovery for edible pulp was 71% for chlorothalonil and 64% for
For screening purposes where only chlorothalonil and not the sum of
the residues of chlorothalonil plus DAC-3701 is required, the
multiresidue method described in the U.S. Food and Drug Administration
Pesticide Analytical Manual (PAM), Vol. I, sections 212.1 plus 252 for
nonfatty foods can be used. The procedure yields a partial (75%)
recovery and has a limit of 0.005 mg/kg. Alternately PAM I, 212.2 can
be used; also with a limit of 0.005 mg/kg. For fatty foods PAM I,
212.2 plus 252 can be used with a limit of 0.03 mg/kg fat.
NATIONAL MRLs REPORTED TO THE MEETING
Country Commodity MRL
United States Banana (whole) 0.5 mg/kg
Banana (pulp) 0.05 " "
New Zealand Celery 15 " "
Lettuce 10 " "
cucurbits, tomatoes 5 " "
South Africa Shelled Ground Nuts 0.1 " "
Chlorothalonil was re-evaluated in response to information desired by
the 1977 Joint Meeting on the effects of cooking on residues and to a
request from the 1979 Codex Committee on Pesticide Residues to review
the recommended temporary maximum residue limits on bananas (whole and
pulp) in light of extensive new data available from field trials
reflecting improved agricultural practice.
In tests conducted in Honduras and the Philippines, repeated low
volume aerial applications of chlorothalonil formulations were made on
bananas for control of foliar diseases. Although this use will result
in some applications being made to fruiting plants it is common
practice to place plastic bags over the developing stems to protect
the fruit until harvest. Samples of mature banana fruits from bagged
and unbagged stems were analyzed for chlorothalonil and its metabolite
DAC-3701. No residues (<0.01 mg/kg) of chlorothalonil or DAC-3701
were detected in edible pulp of any samples. Commercial washing of
the banana fruits prior to export resulted in an average of 75%
reduction in residual chlorothalonil. The data support a reduction in
the recommended temporary maximum residue limits from 4 mg/kg (whole
banana) and 0.1 mg/kg (banana pulp) to 0.2 mg/kg (whole banana) and
0.05 mg/kg (banana pulp).
Data on residues in onions, grapes, potatoes, and tomatoes from
supervised trials in various countries were available. These
confirmed the previous recommendations for onions, potatoes, and
tomatoes and permit the recommendation of a temporary MRL for grapes.
Although it is theoretically possible to have a detectable residue of
the manufacturing impurity hexachlorobenzene on whole bananas if many
repeat applications are made, calculations based on a specification of
not more than 0.02% HCB in a commercial formulation indicate that this
would not be a problem in bananas since no residues should occur in
edible pulp. The situation for other agricultural commodities needs
investigation and clarification.
Chlorothalonil would be detected by the multiresidue methods of
analysis for fatty and non-fatty foods described in the FDA Pesticide
Analytical Manual, Vol. I, and equivalent procedures utilized in other
countries but DAC-3701 would not. Therefore the multiresidue methods
are useful for screening purposes, but if the presence of
chlorothalonil is indicated, need to be followed by the more specific
methods developed for chlorothalonil and DAC-3701 for regulatory
The effect of cooking upon chlorothalonil with plain water, tomatoes,
or green beans was evaluated. Under open cooking conditions,
chlorothalonil was lost (94-98%) through volatilization. Under closed
cooking conditions, hydrolysis to 4-hydroxy-
2,5,6-trichloroisophthalonitrile (DAC-3701) and
3-cyano-2,4,5,6-tetrachlorobenzamide (DS-19221) occurred. When cooked
in a tightly sealed pressure cooker, chlorothalonil remained
unchanged. Under similar test conditions, neither losses nor chemical
changes were observed, for DAC-3701.
A temporary maximum residue limit for grapes is recommended in
addition to those temporary MRL's previously recommended. The
temporary maximum residue limits recommended in 1977 for bananas are
amended as follows:
Preharvest interval on which
recommendations are based;
Commodity Limit, mg/kg days
Grapes 5 46
Bananas (whole) 0.2 none
Bananas (pulp) 0.05 none
FURTHER WORK OR INFORMATION
Required by 1981:
1. Studies to define the growth reduction after administration of
chlorothalonil or its major metabolite (DAC-3701) in pups relative
to ingestion or secretion into milk.
1. Experimental information on the possible occurrence of
hexachlorobenzene residues on crops requiring multiple
2. Results of on-going studies on the effects of cooking under closed
conditions on residue levels and composition.
3. Elucidation of the discrepancies in the carcinogenicity studies.
4. Observations in occupationally exposed humans.
5. Information on the extent of metabolism of chlorothalonil in
Ballee, D.L., Duane, W.C., Stallord, D.E.,and Wolfe, A.L. "Analytical
Methods for Pesticides and Plant Growth Regulators," Vol. VIII, pp.
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