PESTICIDE RESIDUES IN FOOD - 1979
Sponsored jointly by FAO and WHO
EVALUATIONS 1979
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, 3-12 December 1979
CARBOFURAN
Explanation
This pesticide was evaluated in 1976 when a temporary ADI and some
limits were established.
Short term dietary studies in rodents were listed as a requirement for
reviewing the temporary nature of the ADI. Findings from comparative
biochemical studies with a view to defining the apparent sensitivity
of juveniles and further information on residues resulting from
approved uses on major crops were also recorded as desirable.
At its 11th Session, the CCPR requested clarification of the
commodities to be covered by the previously recommended limit for
"other animal feeds".
New information on these points is reviewed in this monograph
addendum.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
TOXICOLOGICAL STUDIES
Special Studies on Cholinesterase Inhibition
Groups of rats were fed carbofuran in the diet at dosage levels of 0,
10, 20, and 100 ppm for two years. At periodic intervals, animals
were sacrificed and plasma, red blood cell, and brain cholinesterase
activity was measured in 10 rats of each dietary level at 6, 12, and
18 months of the study. At 24 months, cholinesterase activity was
determined in 20 animals per sex per treatment level. Technical
carbofuran was found to cause no physiologically significant
depression (<25 percent vs. control) in erythrocyte cholinesterase
activity at any dietary level (10, 20 or 100 ppm) in both male and
female rats at 6, 12, 18, and 24 months. No depression (< 15 percent
vs. control) was observed in brain cholinesterase activity at 10 and
20 ppm in male and female rats at 6, 12, 18 and 24 months. A
depression of brain cholinesterase activity was observed at 100 ppm in
males at 18 and 24 months, and in females at all time intervals. The
cholinesterase inhibition in brain at 24 months was shown to be 21
percent in males and 43 percent in females (Case and Wilson 1979).
Special Study on Mutagenicity
Carbofuran was tested for mutagenicity by the in vitro Salmonella
assay ("Ames test") for screening chemicals for point-mutations.
Mammalian metabolism was simulated by the 9000 g fraction of mammalian
livers (S-9 mix). All groups were tested with the S-9 mix, and
additionally, the highest dose group was tested without an S-9 mix.
The following doses were tested: 0, 1.2, 3.7, 11.1, 33.3, and 100
µg/plate. The solvents used were DMSO for carbofuran and distilled
water for endoxane (positive control, tested at 500 ug/plate).
Doses of up to and including 100 µg/plate did not cause bacterial
toxicity. The test provided no indication of mutagenic effect induced
by carbofuran. The numbers of mutants neither showed a dose-related
increase nor were they doubled. On the other hand, the positive
control increased the number of mutants to more than double that found
in the negative control (Herbold, 1978).
COMMENTS
Carbofuran was evaluated for an acceptable daily intake by the Meeting
in 1976 and a temporary ADI was established. Preliminary results of a
study to define the level causing no cholinesterase depression were
reviewed. In addition, data were reviewed which showed no evidence of
mutagenic potential as suggested by microbial bioassays. The Meeting
was informed that several toxicological studies are in progress and
decided to extend the temporary ADI.
TOXICOLOGICAL EVALUATION
Levels Causing No Toxicological Effect
Rat: 10 ppm in the diet, equivalent to 0.5 mg/kg body weight
Dog: 50 ppm in the diet, equivalent to 1.25 mg/kg body weight
Estimate of Temporary Acceptable Daily Intake for Man
0-0.003 mg/kg body weight
RESIDUES IN FOOD AND THEIR EVALUATION
RESIDUES RESULTING FROM SUPERVISED TRIALS
Brassica leafy vegetables, Maize Leek and Onion
Field trials were carried out with granules (Currater 5%) at various
locations of Germany, the Netherlands in 1976-1978 and Denmark
(Furadan 10) in 1975. The treatments were in accordance with
recommended uses. The details are summarized in Table 1.
Table 1. Residues Resulting from Supervised Trials with Carbofuran (Years 1975-1978)
Single
applications Residues1 in mg/kg, at intervals (days) after application
Crop granules
at a.i. 50-51 59-62 70 79-80 92 104-109 115-125 136-151 161-176
Cabbage 0.1 g/m 13.4 6.4 8.2 7.6
/savoy/ 0.1 g/m 0.3 0.1 0.1 0.1
0.1 g/m 2.02 1.12 2.43 0.26
Kohlrabi 0.1 g/m 0.2 0.2 <O.1 <0.1
0.1 g/m 0.15 0.12 <0.1 <0.1
0.1 g/m 23.72 0.192 23.22 0.54
Cabbage 0.5 kg/ha 0.07 0.04
1 kg/ha 0.1 0.05
2kg/ha 0.3 0.23
Kohlrabi 0.5 kg/ha <0.05 <0.05
1.0 kg/ha 0.05 <0.05
2.0 kg/ha 0.07 0.1
Leek 0.06 g/m <0.1 <0.1
0.06 g/m <0.05 <0.05
1.25 kg/ha 0.5 0.26 0.13
Onions 0.5 kg/ha 0.07
0.04
0.06
0.05 g/m <0.1 <0.1
0.05 <0.1 <0.1
1.5 kg/ha <0.1
1.5 kg/ha <0.1
Table 1. Continued...
Single
applications Residues1 in mg/kg, at intervals (days) after application
Crop granules
at a.i. 50-51 59-62 70 79-80 92 104-109 115-125 136-151 161-176
Maize 0.075 g/m 0.3 0.7 0.4
<0.13
0.075 g/m 0.4 0.6 0.3
<0.13
0.075 g/m 0.3 0.8 0.9
<0.13
1 Sum of carbofuran and 3-hydroxy carbofuran
2 leaf samples
3 in kernel
Alfalfa
Carbofuran (as Furadan 4F) was applied to mixed stands of alfalfa at a
rate of 0.3, 0.6, 1.12 kg a.i/ha 7, 14, 28 days before harvest
respectively in 10 states of US with two replicates at each location.
Carbamate and phenolic residues were determined. The limit of
determination was 0.25 mg/kg for each carbamate derivatives and 0.5
mg/kg for the phenols. The composition of stands varied between:
alfalfa 50-80%, orchard grass 20-50%, bromegrass 15-50% fescue 0-10%,
other grass weeds 0-15%. The average moisture content of samples was
76% (66-86%).
The residue found was mainly 3-OH-carbofuran. Intact carbofuran was
detected /0.26 mg/kg only in one of the 60 treated samples. 12
samples were analysed for phenols but residues were at or below the
limit of determination /0.5 mg/kg/ (FMC 1976a). The total carbamate
residues /mg/kg/ ranged at does rates:
0.3 kg ai./ha 0.25-4.54 / 7 days after treatment/
0.6 kg ai./ha 0.29-4.4 /14 days after treatment/
1.12 kg ai./ha 0.25-3.18 /28 days after treatment/
Alfalfa and bromegrass samples were taken from 11 locations of Canada.
The treatments were made (with Furadan 4.8 F) at dose rates of 0.3 kg
a.i/ha and 2 × 0.15 kg a.i/ha. Samples were analysed for the residues
of carbofuran (CF), 3-hydroxycarbofuran (3OHCF), their phenols and
3-ketocarbofuran phenol. The carbamate residues are summarised in
Table 2. Measurable phenol residues (2.09, 1.46 mg/kg) were only
found 1 day after treatment in alfalfa and none was in bromegrass (FMC
1976b).
The results of these experiments agree with those discussed above.
The low or not detectable residues soon after the treatments may be
due to rainfall which appears to remove the carbofuran carbamate
residues from the plant surfaces of alfalfa and bromegrasses. The
quantity of rain after the treatments was as follows:
No. of exp. Rain /mm/ after treatment /days/
2 3.2 mm /2/ 39.5 mm /3/ 6.6 mm /4/ 58.1 /5/
4 2.7 mm /3/ 1 mm /4/ 19.6 mm /5/
6 6.6 mm /0/ 1.7 mm /1/ 2.5 mm /2/
7 16.2 mm /3/
Table 2. Residues of Carbofuran and 3-hydroxycarbofuran resulting from Supervised Trials in Canada in 1976
Spray
application Residues in mg/kg, at intervals/days/after application
Crop No. rate
kg a.i./ha 0 1 3 7 14 dry /14/
(4.8F formulation) CF 3OHCF CF 3OHCF CF 3OHCF CF 3OHCF CF 3OHCF CF 3OHCF
Alfalfa 2 0.15 4.66 nd 3.50 nd 1.3 nd 0.93 nd nd nd <0.5 <0.5
3.8 nd 4.37 nd 0.9 nd 0.50 nd nd nd <0.5 <0.5
Alfalfa 2 0.15 5.09 nd 2.33 nd nd <0.5 nd <0.5 nd <0.5 nd <0.5
6.4 nd 3.9 <0.5 nd <0.5 nd <0.5 nd <0.5 nd <0.5
Bromegrass 2 0.15 9.79 nd 7.5 nd 5.38 1.0 nd 0.97 nd <0.5 nd 1.3
14.2 nd 10.3 nd 3.42 1.0 nd <0.5 nd <0.5 nd 0.98
17.9 nd nd 0.52
Bromegrass 2 0.15 5.03 nd 2.67 nd <0.5 <0.5 nd nd nd nd nd <0.5
4.28 nd 1.94 nd 0.77 <0.5 nd nd nd <0.5 nd <0.5
Alfalfa 2 0.15 3.86 <0.5 3.16 0.58 <0.5 0.88 nd <0.5 nd <0.5 nd <0.5
4.76 0.58 3.2 1.85 <0.5 1.02 nd <0.5 nd nd nd nd
Bromegrass 2 0.15 15.7 nd nd <0.5 nd nd nd nd nd nd nd nd
14.6 nd nd nd nd nd nd nd nd <0.5 nd nd
Alfalfa 2 0.15 14.4 nd 8.35 nd nd <0.5 nd 0.5 nd 0.56 nd 0.8
7.07 nd 5.58 nd nd 0.74 nd 0.63 nd 0.5 nd 1.0
Alfalfa 1 0.3 15.1 5.29 nd 2.08 nd 2.4 nd 0.98 nd 4.3
14.3 5.38 nd 2.14 nd 2.16 nd 1.72 nd 4.24
Alfalfa 1 0.3 9.46 4.07 nd 1.62 nd 1.40 nd 1.45 <0.5 4.88
9.58 4.07 nd 2.35 nd 1.53 nd 1.60 <0.5 3.66
Alfalfa 1 0.3 10.4 0.7 3.53 2.14 0.76 3.5 nd 1.79
12 nd 2.5 2.62 0.5 2.9 nd 1.18
nd = non detectable
Egg Plants
Egg plants from three locations in Mexico were analysed for carbofuran
and 3-hydroxy-carbofuran. Treatment was one soil application (as
Furadan 3 G at 2 kg ai/ha following by three individual foliar
applications of 75 WP at 1 kg ai/ha per application. Sampling was 7
and 14 days after treatment. No residues were detected at <0.05
mg/kg limit (FMC 1977a).
Garlic
Garlic cloves were treated with 30% seed treater at a rate of 0.5%
ai/100 kg of seed immediately before planting in Argentina. Samples
were taken at harvest 176 days after planting and 0.18 mg/kg
carbofuran but none of 3-hydroxy-carbofuran were detected.
Potatoes
Potatoes from test plots located in ten different states of US were
analysed for carbamate and phenolic residues of carbofuran. The
treatments were 3.4 kg ai/ha (Furadan 10G) at planting plus 3 times of
11 kg ai/ha foliar spray (Furadan 4 F)/experiment A/ applied with a
dose of 6 times 1.1 kg ai/ha/experiment B/. The total residue values
in each sample have been calculated by adding in nondetectable
residues as being equal to the limit of determinations and placing a
"less than" prefix with the sum. The limit of determination for the
various compounds analysed was not reported. The average residue in
10 samples taken at the same time, was calculated by adding in ND as
zero and less than values in as the listed number disregarding the
less than symbol (FMC 1978a). The average, minimum and maximum
residue values found after application are listed in Table 3.
In Canada, Furadan 1OG and 4.8 F were applied on potato field to give
a total toxicant per hectare ranging from 2.2-3.1 kg. At harvest the
residues (carbofuran and 3-hydroxycarbofuran) in 8 samples fell in the
range of 0.01-0.17 mg/kg. The harvested tubers were stored at 5°C and
analysed for carbofuran and 3-hydroxycarbofuran at 0, 30, 60, 90 days.
The total residues were in the range of 0.06-0.11 mg/kg after 90 days.
There was no evidence for conversion of parent compound to its
metabolite during storage (Canada).
Carbofuran applied at a dosage rate of 5-10 kg ai/ha at seeding in
four supervised trials resulted in nondetectable residues in potatoes
134 days after treatment in Finland.
Table 3. Residues in Potatoes mg/kg
Days Experiment A Experiment B
after carbamates Phenols carbamates phenols
Treatment average min. average min. average min. average min.
max. max. max. max.
ND 0.1 ND 0.2
0-2 0.1 0.64 0.4 1.03 0.05 0.2 0.34 0.7
ND 0.1 ND 0.1
12-15 0.08 0.23 0.3 0.48 0.06 0.1 0.3 0.5
ND ND ND 0.2
27-43 0.05 0.3 0.02 0.45 0.05 0.16 0.34 0.06
Soybean
Two separate plots were treated with a foliar spray (Furadan 4F) at a
rate of 0.28 kg ai/ha. One plot received a single application and was
sampled 63 days after treatment. The second plot was treated twice
and the samples were taken 36 days after last application. The
observed carbamate residue was solely carbofuran in the range of
0.05-0.1 mg/kg (FMC 1979b).
Sweet Corn
Sweet corn at various locations of U.S. was treated (with Furadan 10G)
at rates of:
- 4.5 kg ai/ha in furrow at planting;
- 2.24 kg ai/ha at planting as a band of 29-37 cm width;
- 4.5 kg ai/ha in furrow at planting and twice (with Furadan 3G) at a
rate of 0.56 kg ai/ha as foliar spray;
- 1.12 kg ai/ha in furrow at planting and four times (with Furadan 4F)
at a rate of 0.56 kg ai/ha at intervals of 4-6 days during ear
formation.
The carbofuran and hydroxycarbofuran residues in the cobs, kernels,
husks and stalks were determined using nitrogen selective Coulson
detector. The limit of determination was 0.05 mg/kg for carbofuran
and 0.1 mg/kg for 3-hydroxycarbofuran.
The kernels contained no detectable residues regardless of type of
treatment. The residues in cobs were at or about the limit of
determination. The highest residue (4.09 mg/kg) was observed in stalk
87 days after treatment (FMC 1976c, 1976 d). The ranges of residues
measured are summarized in Table 4.
Sugarcane
Supervised trials were carried out in South Africa at dose rates of 3
kg ai/ha (registered dosage) and 4.5 kg ai/ha. The residue in sugar
cane was lower than limit of determination (0.2 mg/kg) in both
experiments.
Table 4. Residues of Carbofuran and 3-hydroxyfuran in Sweet Corn
Sample Dose Rate Days Minimum - maximum residues mg/kg
Type No. Kg a.i./ha Lapsed CF 3OHCF Total Reference
Cobs 16 4.5 66-111 nd 0.1 nd nd nd 0.1 MC-1371
Kernels 16 nd nd nd nd nd nd
Husks 16 nd 0.35 nd 0.95 nd 1.3
nd 0.99 nd 3.1 nd 4.09
Cobs 2 4.5+2 × 0.56 28 0.09 0.1 0.13 0.14 0.22 0.26
Kernels 2 nd nd nd nd nd nd
Husks 2 0.1 0.2 0.5 0.7 0.9 1.2
Stalks 2 0.33 0.7 0.9 1.24 1.2 1.94
Cobs 16 2.24 76.81 nd nd nd nd nd nd
Kernels 16 nd nd nd nd nd nd
Husks 16 nd 0.1 nd 0.1 nd 0.2
Stalks 16 nd 0.1 nd 0.14 nd 0.24
Cobs 10 4.5+3 × 0.56 7 nd 0.08 nd nd nd 0.08
Kernels 10 7 nd 0.05 nd nd nd 0.05
Husks 10 7 0.06 0.44 nd 0.45 0.08 0.89
Stalks 6 21-27 0.2 0.38 0.37 1.82 0.59 2.19
Tobacco
Burley tobacco fields at five locations of U.S. were treated (with
Furadan 10 G or 4 F) before planting at a dose rate of 4.5 kg ai/ha;
another 12 plots received 6.73 kg ai/ha.
Upon harvesting each tobacco plant was separated into upper, middle
and lower leaves for separate analysis. All samples were taken at
normal harvest and then commercially air cured before analysis.
Following the 4.5 kg/ha dose, the total carbamate residues found (CF +
3OHCF) ranged from non-detectable to a maximum of 13.6 mg/kg in lower
leaves, 8.27 mg/kg in middle leaves and 4.72 mg/kg in upper leaves.
The quantitable residue found averaged 24.3% carbofuran and 75.7%
3-hydroxycarbofuran (FMC 1977b). While the total residue ranged from
non-detectable to 19 mg/kg at 6.73 kg ai/ha. The average residue was
2.84 mg/kg for the 72 samples analysed (FMC 1979c). The limit of
determination was 0.5 mg/kg for carbofuran and 1.0 mg/kg for 3-hydroxy
carbofuran in both experiments.
Tomatoes
Two foliar sprays (of Furadan 4.8 F) were applied to ripe tomatoes in
Canada. Samples were taken 1, 3, 6, 10 an 27 days after treatment.
The carbamate residues on fruit declined from 0.25 mg/kg one day after
last application to non-detectability at ten days, with limit of
determination 0.05 mg/kg (FMC 1975).
Experiments on 9 plots treated at planting (with Furadan 10 G) at a
dose rate of 3.36 kg ai/ha in a 29 cm band resulted in non-detectable
residues in the fruits (FMC 1977c).
FATE OF RESIDUES
In Animals
The bio-availability of bound (i.e. unextractables) and conjugated
(i.e. water solubles) carbofuran residues from bean plants was
investigated by administering the radioactive residues orally to
female rats. Whereas the water-soluble metabolites were eliminated
primarily in the urine, most of the bound residues were excreted in
the faeces. In both cases, biliary excretion was minor (Marshall and
Dorough, 1977).
Carbofuran was degraded rapidly also in laying hens (Hicks et al.,
1970); 54% of the dose was hydrolyzed after only 6 hours, and 72% had
been hydrolyzed by the end of 24 hours. Laying hens eliminated most
of the radioactivity in the excreta, in which the 3-hydroxycarbofuran
was identified as the major metabolite. Additionally, free and
conjugated forms of 3-ketocarbofuran, carbofuran phenol,
3-hydroxycarbofuran phenol, 3-ketocarbofuran phenol,
N-hydroxymethylcarbofuran and 3-hydroxy-N-hydroxymethyl carbofuran
were detected in excreta, liver and gizzard. The eggs of laying hens
(Hicks et al., 1970) given an oral dose of radio-labelled carbofuran
[0.3 mg 14C carbofuran/kg body weight; 2.7 mg ring 14C carbofuran/kg
body weight] contained only small amounts of carbofuran equivalents
not exceeding 0.02 mg/kg. All tissues taken from the laying hens for
analysis at 6 and 24 hours contained residues [maximum levels in liver
and kidney amounted to 2.6 mg/kg carbofuran equivalents]. None was
detected thereafter in tissues of hens treated with ring 14C
carbofuran, although certain tissues from the 14C carbofuran-treated
hens contained residues at 3 days. The authors considered that some
of the 14CO carbofuran equivalents may have been naturally occurring
chemicals, which was in agreement with the findings obtained in the
feeding studies on cows (JMPR 1976).
In Plants
Carbofuran was rapidly taken up by plants through the roots from soil,
water or nutrient solution and translocated mainly into the leaves
(Ashworth and Sheets 1972, Penner and Early 1973). The rapidity of
carbofuran degradation differed in the various plant species and the
main metabolite was identified as 3-hydroxycarbofuran.
Soybean seeds and kernels of maize contained only 0.0l% of the applied
radioactivity (Talker et al., 1977) or non-detectable residues - 0.01
mg/kg - (Turner and Caro 1973) respectively at harvest following soil
treatment.
Residues in following crops:
No residues of carbofuran plus 3-hydroxycarbofuran were found in
carrots grown after maize in treated soil. The limit of determination
was 0.1 mg/kg.
In lettuce planted after savoy cabbage, residues of carbofuran plus
3-hydroxycarbofuran amounted to 0.3-0.4 mg/kg 129 days after the final
application, and to n.d.-0.1 mg/kg after 140 and 147 days.
In Soil
The influence of different parameters on carbofuran degradation in
soil was studied. Degradation was seen to accelerate with increasing
pH in laboratory experiments (Stanovick, 1968; Getzin, 1973) and in
field trials (Caro et al., 1973). Degradation was accelerated also by
higher temperature and water contents of the soils (Caro et al.,
1973; Talakar et al., 1977b).
Talekar et al. (1977b) noted that in subtropical soils, carbofuran was
more persistent during the dry and relatively cooler autumn and winter
months than in summer. After ten months, only 0.6% of the residues
present initially could be recovered as parent compound. In
laboratory studies, flooding of soils was likewise found to accelerate
degradation (Venkateswarlu et al., 1977). Only 20 to 35% of
carbofuran remained intact after 40 days of flooding, except in a
relatively acid soil /PH 4.2/ from which 77% unchanged parent compound
was recovered. On the other hand, in a laboratory study, the rate of
carbofuran dissipation was observed to increase, in the order: sandy
loam, silt loam, muck soil (Stanovick, 1968).
Getzin (1973) found that the effect of soil sterilization upon the
degradation rate of carbofuran varied in different soils. Whereas
only slight or no differences were noted in silt loam and organic
soils, the rate of degradation was slower in irradiated, sterilized
clay loam. Williams et al. (1976b) found that the rate of degradation
of carbofuran was forty times greater in non-sterile soil during the
second week after application.
Carbofuran seemingly is metabolized to a lesser extent in soil than in
animals and plants. Several authors (Stanovick, 1968; Caro et al.,
1973; Getzin, 1973) found that unchanged parent compound accounted for
most of the radioactive residue. Getzin (1973) established that most
of the radioactivity - up to 79% - from the degraded carbonyl-labelled
carbofuran was expired as CO2. With ring 14C carbofuran, an
increase in soil-bound radioactivity was observed as time progressed.
Metabolites detected were carbofuran phenol (Stanovick, 1968; Getzin,
1973, Gupta and Dewan, 1975) which accounted for a maximum of 0.8% of
the total activity added as carbofuran 3-keto-carbofuran which
accounted for 5-10% of the carbofuran present and 3-keto-carbofuran
phenol (Caro et al., 1973); Gupta and Dewan, 1975 and Talekar et
al., 1977b).
Carbofuran phenol was immediately bound to the soil constituents and
slowly metabolized by micro-organisms (Stanovick, 1968; Getzin, 1973).
3-ketocarbofuran disappeared from the soil at about the same rate as
carbofuran (Caro et al., 1973). In soil 3-hydroxycarbofuran, the
principal carbofuran metabolite in some plants and animals, either was
not found at all (Gupta and Dean, 1975) or was recovered only in
traces (Caro et al., 1973; Talekar et al., 1977b). On the other
hand, Thinrumurthi et al. (1975) found in experiments with
unlabelled carbofuran at 1 kg ai/ha that 3-hydroxycarbofuran was the
principal metabolite in soil, reaching a maximum of 12.70 mg/kg on Day
20.
In Water
The rate of hydrolysis is strongly pH-dependent. In buffer solution
at pH 5/28°C the carbofuran was stable for 28 days, 48.4% of
carbofuran remained unchanged at pH 7/28°C after 21 days, while 50% of
the compound hydrolysed at pH 9/26°C in 0.46 days. (Cook and Robinson
1972).
The results are in good agreement with the findings of other authors
(McDonald, 1972, Metcalf, 1968).
In field experiments, the behaviour was studied in rice paddy water
(Deuel, 1975). Applied in granular form (as Curaterr) to flood water,
carbofuran was dissipated within 96 hours. No significant levels of
3-keto or 3-hydroxycarbofuran were found in the water.
Metcalf et al. (1974) treated water with 0.1 mg/kg carbofuran. At
13-20°C the residues declined from 0.08 mg/kg immediately after
treatment to 0.01 mg/kg on Day 21 post-treatment. At temperatures of
23-32°C, no more residues were detectable after only 7 days.
In Processing
Tomato fields were treated at planting (with Furadan 10 G) at a dose
rate of 3.36 kg ai/ha in a 29 cm band. The crops were processed.
Samples were taken from tomatoes, juice, puree, juice pomace and puree
pomace and were analysed for the carbamate and phenolic residues of
carbofuran. All samples contained residue of less than the 0.05 mg/kg
limit of determination. Since all processed products of tomatoes are
acidic, any carbamate or phenol residues in tomato samples should
likely be present in the processed products. Thus the negative
results indicate that the residues in tomatoes are much lower than the
0.05 mg/kg limit of determination (FMC 1977c).
EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT
CONSUMPTION
26 samples of barley, sugarbeet, maize, onion, rape, carrot, known to
have been treated with carbofuran at sowing were taken and analysed
for carbofuran, but none contained detectable residues (Hungary,
1979).
NATIONAL MRLs REPORTED TO THE MEETING
Country Crops MRLs in Preharvest
mg/kg Intervals/days
Argentina Apples, pear 60
peaches 45
tobacco, tomatoes no waiting-times
corn, potatoes fixed
Austria general 35
Belgium sugar-beet, corn grains 0
corn fodder 0.5
general 150
Brazil milk 0.02
rice 0.2 30
cabbages 1 90
peanut and cotton seed 0.1 14
Canada carrots, rutabages, turnips 0.5
corn, grain 0.1
strawberries 0.4
Country Crops MRLs in Preharvest
mg/kg Intervals/days
Cyprus potatoes, bananas
vegetables, beans, brassicas
tomatoes, eggplants,
cucumbers, onions, etc,
groundnuts, fodder beets,
tobacco 21-28
Fed. Republic corn, hops, beets fixed by registered
of Germany application
cabbage 70
wine grapes 56
German potatoes 21
Democratic drift-treated cultures
Republic /provisions/ 21
drift-treated cultures
/fodder/ 14
Hungary general 0.1 30
Italy sugar-beet 0.1
Kenya maize grain 0.1
sugar cane 0.1
rice 0.2
turnips 0.5
Mexico alfalfa 7-14
cotton 10
sugar cane 17
potatoes 14
Netherlands onions 0.1
others 0
New Zealand grapes, pipfruit 42
pastures 42
Switzerland Field applications 21
mushrooms 0.8
corn 0.1
Spain beet, corn, sorghum 60
South Africa corn, fodder 56
mealies/green 0.2
sugar cane
Country Crops MRLs in Preharvest
mg/kg Intervals/days
Taiwan vegetables 15
fruits 10
rice 21
APPRAISAL
Carbofuran is applied at planting or sowing or as foliar treatment at
various times during the growing season. Trials indicate that the
residues in treated crops such as egg plant, potatoes, soybean sweet
corn, tomatoes are generally very low or not detectable even if a
foliar treatment was applied shortly before harvest.
Only plants having a large leaf surface such as alfalfa, cabbage,
forage, grasses, maize and tobacco, contain high residues, which
consist mainly of the intact carbofuran and the conjugated
3-hydroxycarbofuran. The residue found in mixed stands of alfalfa and
forage grasses is covered by the limit given for alfalfa. There are
no data available for the residue in fodder beet or animal feeds other
than those discussed in 1976 or in this addendum, and no new data were
provided for Brussels Sprouts.
Most of the bound residues in bean plants administered orally to
female rats were excreted in the faeces, whereas the conjugated
metabolites were excreted in the urine. Carbofuran was degraded
rapidly in laying hens and eliminated in the faeces, in which
3-hydroxycarbofuran was the major metabolite. The eggs contained less
than 0.02 mg/kg residues calculated as carbofuran.
No residues of carbofuran or 3-hydroxycarbofuran were found in carrots
grown after maize, but in lettuce planted after cabbage, the residue
amounted to 0.3-0.4 mg/kg 129 days after the final application.
The degradation of carbofuran in soil is influenced by several factors
such as pH, humidity, temperature, soil type and microbial activity.
Carbofuran phenol was immediately bound to the soil and slowly
metabolized by micro-organisms.
The new information on methods of analysis supports the conclusions of
the 1976 Meeting.
RECOMMENDATIONS
In the light of the data available, the limits recommended previously
for "fodder beets" and "other animal feeds not otherwise listed" are
withdrawn. The limit for sugar beet leaves in amended. The remaining
recommendations of the previous Meeting are supported by more recent
studies. In addition, new limits are recommended for kohlrabi and egg
plants, as follows:
New or Amended Recommendations
Commodity Temporary MRL, Pre-harvest intervals on which
mg/kg recommendations are based/days
Egg plants 0.1 14
Kohlrabi 0.1 80
Sugar beet
leaves 0.2
FURTHER WORK OR INFORMATION
Required by July 1980:
1. Submission of the long-term feeding studies in appropriate
species.
2. Teratogenicity and reproduction studies.
Desirable:
1. Comparative animal studies to evaluate the apparent sensitivity of
juveniles with respect to adults.
2. Observations in occupationally exposed people.
3. Further information on the level of residues in brassica cole
leafy vegetables, especially Savoy cabbage and Brussels sprouts, and
in bulb vegetables resulting from approved uses of carbofuran.
4. More information on use patterns on sugar cane and on the residue
in the cane, raw sugar and refined sugar.
5. Selective surveys of residues in crops known to have been treated
under practical circumstances.
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