CAMPHECHLOR JMPR 1973
Explanation
This insecticide was previously evaluated (as Toxaphene) in 1968
(FAO/WHO, 1969b) at which time no recommendations were made because of
the many unresolved questions related to this compound.
New toxicological data relating to reproduction have become
available. These data and all the previous data were considered by the
meeting although only new data summarized in the following monograph
addendum.
IDENTITY
Camphechlor is a complex mixture of chloro bicyclic terpenes
resulting from the chlorination of camphene.
Absorption and gas-liquid chromatography separate camphechlor
into at least 175 C10-polychloro compounds including C16, C17, C18,
C19 and C110 derivatives (Casida, 1973). One toxic component has been
isolated and its structure determined to be 2,5-endo, 2,6-exo,
8,9,10-heptachlorobornane. More than 100 octochloro structures are
possible, hence, control of camphene feedstock quality, chlorine
content and process variables is important in achieving a material of
uniform composition. Examination of infrared spectra, electron capture
gas chromatograms and bioassays shows that camphechlor produced by
Hercules Incorporated over a 25-year period has been a reproducible
product with uniform biological, chemical, and physical properties.
For example, bioassay of 10 samples of camphechlor produced during the
period 1949-1970 had an average LD50 to female houseflies of
19.34 mg/g with a range of 18.9-19.9 mg/g (Buntin, 1970).
Infrared spectra and electron capture gas chromatograms obtained
from these samples also demonstrate the uniformity of camphechlor. The
information which follows has been obtained from investigations
conducted on commercial camphechlor of uniform composition meeting
official FAO specifications 23/1/S/5.
EVALUATION FOR ACCEPTABLE DAILY INTAKE
Biochemical aspects
Following a single oral dose of camphechlor to rats (20 mg/kg)
recovery of 36Cl was found to be predominantly in the faeces (70%)
with the urine having 29.1%. Total recovery following single dose was
in the range of 40-50% in urine and faeces. The major quantity was
eliminated within 24-48 hours after dosing (Crowder, 1973). At the end
of nine days following single dose, 3.65% of 36Cl was observed in the
fatty tissue (Crowder, 1973).
TOXICOLOGICAL STUDIES
Special studies on reproduction
Mouse. Groups of mice (four males and 14 females per group) were
fed camphechlor in the diet at levels of 0 and 25 ppm in a
five-generation, two litters per generation, reproduction study. There
were no effects noted with camphechlor on any of the reproduction
parameters measured (Keplinger et al., 1970).
Rat. A three-generation, six-litter reproduction study was
conducted with toxaphene. Groups of weanling rats were fed 25 ppm and
100 ppm for 79 days before mating. All animals were continued on their
respective dietary concentration of toxaphene during the mating,
gestation, weaning of two generations, or for a period of 36 to 39
weeks. Weanlings from the second litter were selected as parents lot
the second generation and continued on their respective diets until
after weaning of a second litter. A third generation was selected in
the same manner. Complete gross and histological examination was
performed on all three parental generations after 36 weeks of
toxaphene administration. The only pathologic changes found were
slight alterations in the livers of the 100 ppm group similar to those
changes seen in long-term studies. Reproductive performance, fertility
and lactation were normal. The progeny were viable, normal in size and
anatomical structure. Findings among all test animals, three parental
generations and six litters of progeny were comparable to control
animals for all parameters (Kennedy et al., 1973).
Special studies on teratogenicity
Camphechlor was injected into the yolk of fertile eggs after
seven days incubation at doses ranging from 0 to 1.5 mg/egg. No
effects on hatchability or teratogenic potential were observed (Smith
et al., 1970).
Short-term studies
Rat. Toxaphene did not significantly affect the physical appearance,
gross pathology, weight gain or liver cell histology of albino rats
given levels from 2.33 to 189 ppm in their diets for up to 12 weeks.
There were male-female differences in liver cell diameters, as well as
in weight gain and residue patterns. Dunnett's comparison test
indicated that significant levels of toxaphene were present in liver,
omental fat and whole body samples (minus liver and omental fat) with
each dose at four, eight and 12 weeks (Clapp et al., 1971).
Administration to rats of 1.2 mg/kg technical polychlorcampher
for 12 months resulted in changes in the liver function evidenced by
increased sleeping time and hippuric acid synthesis (Spinu et al.,
1970). At higher doses (4.8 mg/kg) hypoglycaemia resulted while at 2.4
mg/kg the increase in sleeping time was noted after two months and on
cessation of treatment returned to normal on the fourth month
(Grebenjuk, 1970).
Observations in man
No porphyrin was found in the urine of 45 workers daily exposed
to a variety of pesticides, predominantly parathion, toxaphene, DDT,
and dieldrin. The qualitative method used was capable of detecting 0.4
µg/ml. No correlations were found between serum pesticide levels and
urinary excretion of ALA, PBG, and CCA. Parathion depressed plasma
and/or red cell ChE in five workers. The negative findings suggest
that ordinary occupational exposure to the pesticides noted above has
no strong porphyrinogenic or sympathotonic effects (Embry et al.,
1972).
Comments
The Joint Meeting considered new data on distribution and
excretion and on the lack of reproductive hazard associated with
camphechlor. The Meeting reaffirmed the principles set forth by the
1968 Joint Meeting that an ADI could not be established for material
whose composition may vary with the method of manufacture.
The 1968 Joint Meeting evaluated the available data indicating
that although adequate work has been done on a product of defined
specifications the materials in worldwide agricultural use may not
conform to the specifications of the original product tested nor to
those specifications set by the FAO. Although the specifications of
FAO have been met by one manufacturer, the product from other sources
cannot be considered in the light of the known data. It was suggested
that the toxicological studies reported over the past 20 years were
performed with a product of uniform reproducible composition. However,
a question was raised concerning certain studies performed 20 years
ago, particularly on the question of carcinogenesis, in light of
current thinking concerning the effects of chlorinated pesticides.
The Meeting was informed of current research with camphechlor
which may resolve some of the problems facing the Meeting in its
evaluation of camphechlor. The Meeting re-affirmed the principles set
forth by the 1968 Joint Meeting and considered that it could not
establish an ADI on the product available on a worldwide basis.
Although available data might be adequate to establish an ADI such
action could not be accomplished where material used in world trade
may not be uniform. The Meeting further hoped that the questions
raised concerning uniformity of the product over the years be more
completely resolved. The Meeting expressed the hope that further
research in progress will aid in resolving the questions on the
uniformity of the product conforming to FAO specifications and those
products used in worldwide agriculture.
RESIDUES IN FOOD AND THEIR EVALUATION
Use pattern
Pre-harvest treatments
Camphechlor is used to control a variety of arthropod pests which
attack agronomic and horticultural crops and livestock. The major
areas of use include cotton, livestock, oil seeds, cereal grains,
vegetables, fruits and nuts. Camphechlor has a particular advantage in
that it can be used on crops such as seed alfalfa and vegetables
without causing great damage to bee pollinators. Crop pest control is
by foliar application of sprays, dust and granules except for the use
of baits against cutworms. Emulsion sprays and dips and oil solutions,
self-applied by backrubbers, are the usual means of treating livestock
with camphechlor for the control of external pest.
Camphechlor is usually applied to crops at rates of 1-3 kg per
hectare and to livestock at concentrations of 0.25-0.5% by dips and
sprays and 2.5-5% by backrubbers. Camphechlor has been especially
valuable in the control of ticks and of mites.
On crops, camphechlor is frequently applied with other pesticides
such as DDT, methyl or ethyl parathion, maneb and others. Camphechlor
is also registered for use in 70 countries. The principal crop and
livestock uses and the geographic areas of use are tabulated below:
Crop use outside United States of America
Geographic area Principal crop use
Central America cotton
South America cotton, small grains, soybean, bananas
Africa cotton, vegetables
Europe cotton, rapeseed, vegetables
Asia cotton, peanuts, vegetables, rice
Oceania cotton
Livestock use outside United States of America
Africa
East, Central and South Africa, including Uganda, Kenya,
Tanzania, Rhodesia, Angola, Nigeria, and South Africa.
South America
Brazil, Columbia, Peru, Venezuela and Ecuador.
Central America
Mexico, Costa Rica, El Salvador and Panama.
North America
Canada
Post-harvest treatment
Camphechlor is not used for post-harvest treatments.
Residues resulting from supervised trials
The available data were summarized as Table 1 in the first
evaluation of camphechlor (FAO/WHO, 1969), which is repeated here for
clarity and continuity. It selectively summarizes camphechlor residue
data on representative crops and livestock when approved agricultural
practices are followed.
Residues in crops
The half-life of camphechlor residues on growing leafy crops is
in the range of 5-10 days; residues from emulsifiable formulations are
typically higher than those from wettable powders or dusts.
Studies of camphechlor residues on alfalfa and clover show that
the half-life (corrected for crop growth dilution) is consistently in
the range of 9-13 days under widely varying climatic conditions.
Studies were conducted in Arizona, California and Delaware (United
States of America).
Residues on crops are kept within established levels by suitable
restrictions such as dosage rate, application before the formation of
edible parts or by appropriate pre-harvest or pre-slaughter intervals.
Residues in livestock
Camphechlor residues can be accumulated in fat of animals from
ingestion and by dermal absorption. The storage level is much less
than that of most other chlorinated hydrocarbon pesticides, and an
equilibrium with the exposure level is rather quickly achieved.
Elimination of camphechlor from the fat is quite rapid when the input
is reduced. This is true at both high and low levels of ingestion.
Storage/feed ratios for various animal species are summarized as
follows:
Storage/feeda Observation
ratio period
Rat 0.4 2 years
Dog 0.3 2 years
Sheep 0.3 16 weeks
Cattle 0.5 16 weeks
a Storage/feed ration = ppm in fat
ppm in feed
TABLE 1. CAMPHECHLOR RESIDUES RESULTING FROM SUPERVISED TRIALS
Rate of No. of Pre-harvesta Residue
application treatments interval at harvest Comments
(kg/ha) (days) (ppm)
Vegetables
Lettuce 5.5 1-1 10 5.8-7.9 whole head
Kale 5.0 4 36 3.3-7.2
Cabbage 1.9-1.2 2-6 9-38 0.8-6.6 on outer leaves
Spinach 5.0 4 30 16.7-18.8
Celery 1.1-1.6 9 13 1.8 stalks washed
6.5 leaves
Cauliflower 3.8 1 8 1.1 (processed commercially
Broccoli 10 1 8 3.4 and frozen before analysis)
Tomatoes 1.3-2.5 8-9 5-7 2.0-4.3
Green beans 7.5 1 7 1.3 unwashed
Lima Beans 3.9 1 14 0.3 shelled beans
Carrots 25 2-4 0.9-3.3 soil application 1 year
Potatoes 0.95-2.5 6 21 0 detected
Field peas 2.5 3 4 1.8
Oil seeds
Cotton (seed) 3.9-5.0 15 6 3.6-5.2 lint bearing seed
Soybeans 3.8 3 60 0.5
Peanuts
(shelled) 25-50 1 0 detected soil treatment
Fruit
Oranges 5.7 2 7-70 0-10.9 skins
0-0.3 pulp
TABLE 1. (Cont'd.)
Rate of No. of Pre-harvesta Residue
application treatments interval at harvest Comments
(kg/ha) (days) (ppm)
Bananas 3.8 1 1 0.3-1.3 whole fruit
Pineapple 2.8 2 81-96 1.3-2.7 whole fruit
Cereal grains
Wheat 1.9-3.8 1 14-21 0.5-1.8
Barley 1.9-3.8 1 7-28 0.7-14.2
Oats 1.9-3.8 1 7 1.0-2.6
Rice 1.9-3.8 1 7-28 1.5-5.6 unfinished grain
Sorghum 2.5 1 28 2.5-3.1
Corn (maize) 2.5 1 12 0.08 kernels
Fat of meat
Animals
Beef 0.5% 12 28 5.0 12 weekly sprays
Swine 0.5% 2 28 0-0.6 2 sprays
Shelled nuts
Almonds 4.0 3 136 1.5
a Interval from last application if multiple applications were made.
The rapid elimination of camphechlor residues from the fat of
animals allows it to be used for ectoparasite control on livestock
within 28 days of slaughter. Where shorter preslaughter intervals are
required, other pesticides must be used.
Residues in milk
Consistent with the fat-storage properties of camphechlor in
livestock, transmission of camphechlor residues to milk follows the
same pattern (Claborn et al., 1960; Zweig et al., 1963). Equilibrium
with input is reached within about one week, and the ratio of
camphechlor concentration in the feed to that in the milk is about
100:1. Excretion of camphechlor in milk declines quickly when exposure
ceases.
In feeding trials, milk free of camphechlor residues was produced
within two weeks after cessation of feeding 10 ppm in the ration. At a
feeding level of 20 ppm in the daily diet for 11 weeks,
camphechlor-free milk was produced four weeks after
camphechlor-containing feed was discontinued.
Restrictions against the application of camphechlor to dairy
animals and against feeding dairy animals certain forages and crop
refuse treated with camphechlor have been successful in preventing
unwanted camphechlor residue in fluid milk and other dairy products as
indicated by the results of the United States Food and Drug
Administration market basket surveys and other surveillance
programmes.
Fate of residues
On plants
Evaporation
Camphechlor is not systemic. Residues on crops are therefore
essentially confined to the surface of leaves and other plant parts.
The observed half-life of camphechlor residues on plants ranges from
5-13 days. Recent studies have established that volatility is a major
factor in the loss of thin films of camphechlor from glass plates and
from the surface of leaves. Sunlight has little effect on the rate of
loss of camphechlor from thin films on glass plates. Camphechlor is
easily washed from smooth glass surfaces by heavy rains in contrast to
deposits on crops, which are much more resistant to wash-off by rain
(Carlin, 1970b, Hercules Inc., unpublished report, 1970a).
Chemical nature of the residue
There is no evidence of the existence of camphechlor conversion
products in weathered crop residues. Such residues are composed of
unaltered camphechlor.
Klein and Link (1967) examined residues on camphechlor-sprayed
kale and found that over 99% of the original residue was lost during
the first two weeks. Gas chromatographic analysis of the residues
indicated a modest loss of early-eluting GLC components. However, the
composition of the residue even after four weeks was readily
recognizable as camphechlor from the GLC elution pattern. Carter et
al. (1950) examined weathered camphechlor residues on alfalfa and
found insecticidal activity was the same as that of camphechlor.
Carlin (1970a) concluded that no camphechlor conversion products
were formed in alfalfa allowed to weather after being treated with
camphechlor. These conclusions were based on measurements by "total
chloride" methods, electron capture GLC, and bioassays, the last
showing no greater toxicity than authentic camphechlor. A study of
residues on cotton plants led to the same conclusion.
Possible metabolites of camphechlor
Attempts to introduce functional groups into camphechlor by in
vitro chemical reaction have been unsuccessful, and the availability
of model compounds as authentic reference standards for various
separation and detection systems has been limited.
Recently, samples of "keto-camphechlor" and "hydroxy-camphechlor"
were prepared by Buntin. Camphor was chlorinated to a value
corresponding to the addition of seven atoms of chlorine. The
resulting "keto-camphechlor", a viscous pale yellow liquid, was
reduced with lithium aluminum hydride to form "hydroxy-camphechlor".
These compounds are less toxic to flies and rats than camphechlor; gas
chromatography shows they elute with the early peaks of camphechlor.
Clean-up techniques applied to keto-camphechlor and
hydroxy-camphechlor show that the former survives fuming sulfuric
acid, but that hydroxy-camphechlor does not. Dehydrohalogenation (as
applied to camphechlor prior to gas chromatography) showed that these
compounds are retained in the alkaline aqueous phase when it is
extracted with hexane. Both compounds are extracted by hexane from
distilled water.
Weathered camphechlor residues from alfalfa were examined for the
possible presence of keto-camphechlor or hydroxycamphechlor. No
evidence for their presence was found.
In animals
As discussed above, the accumulation of residues in animal fat as
the result of typical application or ingestion of camphechlor is
characterized as follows:
(1) At any given subacute level of intake, a certain storage level is
attained and additional intake does not result in further
increase.
(2) When the source of camphechlor is removed, the residue is rapidly
eliminated.
(3) The level of storage is lower and elimination more rapid than
with most other chlorinated hydrocarbons.
As with weathered residues on crops, stored residues in animal
fat consist of unmodified camphechlor. Carter et al. (1950) reported
that residues in the fat of steers wintered on camphechlor-treated
alfalfa hay were similar in infrared absorption and insecticidal
activity to authentic camphechlor.
Recently 36Cl-labelled camphechlor was orally administered to
rats in a preliminary study of the metabolic fate of camphechlor in a
mammal. Each rat was given a single oral dose of 25 mg/kg bw. The rats
were sacrificed 72 h after dosing. Faeces, urine (up to 72 hours),
kidneys, liver, and fat were analysed as were the remainder of each
carcass. The bulk of the activity found was found in the urine,
faeces, and carcass with only small amounts present in the fat, liver,
and kidney. Of the total activity detected in the rats (including
urine and faeces), one-half was ionic 36Cl, one-quarter was
water-soluble but not ionic 36Cl and one-quarter was hexane soluble
(Hercules Inc.).
Very similar results were obtained by Casida et al. (1973) who
administered 36Cl-camphechlor orally to rats at about 14 mg/kg to
determine the extent of dechlorination and rate of elimination over a
14-day period. Less than 0.7% of the 36Cl appeared in urine and less
than 3% in faeces as unmetabolized camphechlor. Approximately 25% of
the 36Cl appeared in urine and faeces (mostly) as partially
dechlorinated metabolites of camphechlor. The remainder, 44-57% of
dose, appeared as chloride ion (36Cl-) in the urine.
These studies are being continued to define more completely the
composition of technical camphechlor and the structure, metabolic fate
and environmental persistence of the various components.
In the honey bee
A study of camphechlor residues in rape-seed oil, honey, and bees
was conducted by Jumar and Sieber (1967). They prepared a 36Cl-tagged
camphechlor and determined that residues were transmitted to rape-seed
oil in the range of 0.3-1.5 ppm, depending on the method of
application to the rape-seed plant. Honey made by bees exposed to the
camphechlor-treated plants contained less than 0.01 ppm camphechlor.
The study on camphechlor in bees employed 82Br-camphechlor (one Cl
atom replaced by 82Br). More than 95% of camphechlor absorbed by bees
from feeding was stored briefly in the body before release as a
chlorine-containing water-soluble compound which was not identified.
In animal feeds and forage
Residues of camphechlor in forages such as alfalfa and clover
typically have a half-life of 9-13 days (corrected for dilution by
crop growth). As previously discussed, the major mechanism of loss is
by evaporation.
In water
The solubility of camphechlor in water is 0.4 mg/1. Camphechlor
is stable in distilled water and in dilute emulsions but recent
evidence demonstrates that changes may occur in natural waters and in
sediments, probably as a consequence of microbial activity. The lower
limit of detection by taste is about 5 ppb camphechlor. Treatment of
water with activated carbon is an effective means of removal to
produce potable water (Cohen et al., 19-60; ibid., 1961).
In soils
Camphechlor is not normally used to control soil insects with the
exception of surface sprays and baits for cutworm control. Most
camphechlor residues in soil therefore result from foliar sprays which
missed the target and to a lesser extent to residues from
non-harvested portions of treated crops.
Camphechlor residues in and on soil may be detected for varying
periods of time after application depending on soil type, climate, and
rate of application. In recent work with 36Cl-labelled camphechlor
the half-life varied from 70 days for moist sandy soil to 179 days in
a moist clay soil. The half-life in these same soils kept dry was 136
and 705 days respectively (Hercules Inc.).
The application of camphechlor at the rates used for insect
control has not resulted in the build-up of residues in the soil in
areas of regular usage. Bradley et al. (1972) working on small plots
of loamy sand and sandy loam soils in North Carolina applied
camphechlor foliar sprays at approximately weekly intervals from early
June until September 1969. The total amount applied was 23.9 lb per
acre. Only 5-10% remained in the soils in September 1969; 4% was found
the following March. Less than 1% was accounted for in water and
sediment run-off.
Stevens et al. (1970) made a nationwide survey of pesticide
levels in soils. Samples were taken from 51 locations about equally
divided between areas where pesticides were used regularly, areas with
no history of pesticide use and areas which had received at least one
pesticide application. No evidence of camphechlor build-up was found.
In areas of regular pesticide use, 60% of the vegetable and/or cotton
field samples and 12% of small grain and root crop field samples
contained camphechlor residue. The data show that the residues of
camphechlor from crop applications made over periods of 1-14 years
were present at only small fractions of the amount applied. No
camphechlor was found in soils from areas where pesticides had been
used infrequently or areas where no pesticides were used.
More recently Wiersma et al. (1972) have reported the 1969
results of the National Soils Monitoring Study. Pesticide residues
found in cropland soil for 43 states and for non-cropland soils for 11
states are summarized. Dieldrin was found to be the most widely
distributed organochlorine pesticide. Detectable residues of dieldrin
were found at 27.8% of the sites sampled. Toxaphene (camphechlor)
residues occurred at only 4.2% of the sites in spite of the fact that
the 43 states from which cropland soil was sampled include the areas
of major camphechlor use with the exception of Texas. Camphechlor
occurred in a single sample of 199 non-cropland soil samples.
Camphechlor residues in soil do not leach appreciably and
downward migration through the soil does not occur to a significant
degree. Nash and Woolson (1968) determined the vertical distribution
of camphechlor over a three-year period. Between 85% and 90% of the
camphechlor remaining, three years after the last application was
found in the upper 23 cm, corresponding to the cultivated zone. Thomas
(1970) studied the distribution of camphechlor in Texas soils to a
depth of 5 ft. He found that very little camphechlor occurred below a
depth of 1 ft. Only about 20% of the camphechlor applied in the
preceding 10 years could be accounted for in the soil profile.
The longer period of biological activity of camphechlor
mechanically mixed with soil (Mulla, 1961) in contrast to camphechlor
applied to the soil surface (Shaw and Riviello, 1961) suggests that
persistence on the soil surface is less than when incorporated into
the soil. Recent work on the mechanism of the decline of camphechlor
residues indicates that a major mechanism is evaporation. Studies with
36Cl-labelled camphechlor (Hercules Inc.) confirm that camphochlor
disappears from the surface of soil by evaporation as well as by
chemical reaction involving the formation of chloride.
Camphechlor residues in soil are subject to degradation by soil
microorganisms. Both soil bacteria and fungi degrade camphechlor, the
bacteria using it as a source of carbon (Smith and Wengel, 1947). This
work and other evidence of microbial degradation has been summarized
by Paris and Lewis (1973).
During storage, processing, cooking
Farrow et al. (1968) have demonstrated that in commercial
canning, surface residues are reduced by washing, peeling, and
abrasive peeling. Since camphechlor is non-systemic, surface residues
of camphechlor will be removed by these operations both in commercial
canning and in the preparation of fruits and vegetables for culinary
purposes in the home.
Washing alone will remove significant amounts of camphechlor
residues. Thompson and Van Middelem (1955) found that washing with
water removed significant amounts of the residues on certain
vegetables. The addition of 0.1% synthetic detergent or 1.0% neutral
soap to the wash water increased the percentage removed.
Percentage of initial camphechlor residues removed
Washing treatment
Green Mustard
Tomatoes Beans Celery greens
Water N.S.a 20 57 57
1% neutral soap N.S.a 67 73 91
0.1% alkyl-aryl N.S.a 58 72 90
polyether alcohol
a Not significant.
Since camphechlor residues are located in the fat of meat,
trimming to remove excess fat will reduce the residue. Cooking at
temperatures sufficiently high to render out fat will also physically
remove some of the residue (Liska and Stadelman, 1968).
Heat processing used in producing canned foods will also
significantly reduce camphochlor residues initially present on the raw
product. Elkins et al (1972) fortified apricots and spinach at 7 ppm
(the United States tolerance level for these products). Samples were
analysed immediately after processing and after storage for one year
at ambient temperature. Processing of spinach resulted in a 27%
reduction in residue level and a 60% loss after processing followed by
storage for one year. Losses in apricots were somewhat less, 7% due to
processing and 35% after processing and storage.
Evidence of residues in food moving in commerce or at consumption
Camphechlor is registered for a variety of uses on food crops and
livestock. During 1965-1968, United States Food and Drug
Administration market-basket surveys showed camphechlor to be
virtually absent from these samples. The frequency of occurrence of
camphechlor residues in these studies was less than that of the first
15 most commonly found pesticides. The market-basket samples represent
the total diet of a 16-19-year-old male, and are obtained from retail
stores in five regions at bi-monthly intervals. Food is prepared for
consumption and analysed for pesticide residues using gas-liquid
chromatography methods.
In the later period, June 1968 April 1969, camphechlor was
detected in 13 of the 360 composite samples analysed. Range of
residues was 0.02-0.33 ppm in food categories, garden fruit,
vegetables, and meat fat.
A summary of the United States Food and Drug Administration
surveillance programme and market-basket results for camphechlor in
the period 1964-1969 (Duggan et al., 1971) using the food categories
established by the United States Food and Drug Administration is given
in Table 2. These data reflect the widespread usage of camphechlor on
vegetables and the retention of some of the residue in the processed
(canned, dried, or frozen) food. Camphechlor residues were sixth most
frequent in occurrence of all pesticides in processed foods, but few,
if any, were in excess of the 7 ppm tolerance.
Camphechlor finds its most intensive agricultural use on cotton.
It is also used to a lesser extent on other oil seed crops such as
soybeans, peanuts, and corn. Analysis of oil and other products
derived from these crops show camphechlor is found in about 30% of the
cotton-seed samples, 8% of the soybean samples, and 2% of the peanut
samples. Above-tolerance residues have not been a problem either in
the raw agricultural commodities or in the processed oils and meals.
Duggan and Corneliussen (1972) calculated the daily intake of
pesticide residues in the United States from market-basket sample
data. The period covered was June 1968 to April 1970.
For the period June 1968 to April 1969, the calculated daily
intake of camphechlor (in milligrams per day) was 0.001 in leafy
vegetables; 0.002 in garden fruits; and less than 0.001 each in meat,
fish, and poultry, in legume vegetables, and in root vegetables. For
the period June 1969 to April 1970, the calculated daily intake of
camphechlor (in milligrams per day) was 0.001 in garden fruits and
less than 0.001 in leafy vegetables. In the six-year period 1965-1970,
the average daily intake of camphechlor as measured in this series of
studies was only 0.0015 mg per day.
In addition to the FDA surveillance and market-basket programme,
the United States Department of Agriculture regularly examine tissues
from meat animals and poultry slaughtered in federally inspected
plants. A tabulation of their findings for the year 1969 and the first
six months of 1970 is given in Table 3. It is notable that, in spite
of the widespread use of camphechlor on grains and other ingredients
of animal feeds and its application to animals for ectoparasite
control, camphechlor was found in only two of the 3169 meat samples in
1969 and in but two of the 2199 poultry samples in the same year. In
the first half of 1970, three of 1871 meat samples and none of 1486
poultry samples contained camphechlor. In comparison, DDT was found in
2671 meat samples in 1969 and in 1432 samples in the first half of
1970. Because of the low levels of camphechlor in the environment and
the ability of the animals to quickly excrete camphechlor, residues of
camphechlor in meat and poultry are virtually non-existent.
TABLE 2. CAMPHECHLOR RESIDUES IN FOOD BOTH DOMESTIC PRODUCTION AND
IMPORTED - UNITED STATES, 1964-1969 (DUGGAN ET AL., 1971)
No. samples Incidence % Average ppm
Food group
Dom. Imp. Dom. Imp. Dom. Imp.
Fluid milk (fat basis) 12 989 - - - - -
Dairy products (fat basis) 6 231 1 981 - - - -
Large fruits 6 763 2 495 0.2 0.4 T 0.02
Small fruits 2 695 496 0.9 0.2 0.01 T
Grain and cereals (human use) 8 005 104 0.4 - T
Leaf and stem vegetables 13 864 153 7.9 2.7 0.20 1.24
Vine and ear vegetables 8 072 1 791 1.3 5.0 0.01 0.02
Root vegetables 13 561 533 1.4 - 0.01 -
Beans 1 492 144 1.1 1.4 0.01 T
Meat (fat basis) 12 146 3 674 1.4 0.1 0.01 T
Poultry (1968-1969) 3 414 - -
Eggs 4 046 121 0.1 - T -
Fish 2 150 378 1.9 0.8 0.04 T
Shellfish 830 167 - - - -
Grain (animal) (1966-1969) 1 168 60 - - - -
Infant and junior foods 2 078 - -
Tree nuts 418 128 T T 0.2 1.6
Peanut products
Nuts 229 1.3 0.005
Crude oil 41 2.4 0.008
Meal (cake) 36 - -
Refined oil 11 - -
Cotton-seed products
Seed 31 29 0.017
Crude oil 282 1.1 0.008
Meal (cake) 287 3.5 0.002
Refined oil 48 10.4 0.12
Soybean products
Soybeans 690 7.1 0.006
Crude oil 118 8.5 0.114
Meal (cake) 248 - -
Refined oil 34 2.9 T
TABLE 2. (cont'd)
No. samples Incidence % Average ppm
Food group
Dom. Imp. Dom. Imp. Dom. Imp.
Corn products
Grain 1 314 - -
Crude oil 28 - -
Refined oil 10 - -
Oleomargarine 85 - -
T = Less than 0.005 ppm.
- = Not detected.
TABLE 3. CHLORINATED PESTICIDE RESIDUES IN MEAT AND POULTRY -1969 AND 1970
No. of tissues No. with
Species analysed No. with a residue toxaphene
1969 1970 1969 1970 1969 1970
(6 months) (6 months)
Meat
Cattle 739 583 712 a 2 0
Calves 142 67 141 a 0 0
Swine 1 964 1 076 1 741 a 0 2
Sheep 312 137 303 a 0 1
Goats 12 8 10 a 0 0
Total 3 169 1 871 2 907 1 721 2 3
Table 3. (cont'd)
No. of tissues No. with
Species analysed No. with a residue toxaphene
1969 1970 1969 1970 1969 1970
(6 months) (6 months)
Poultry
Young chickens 1 909 1 405 1 898 a 2 0
Mature chickens 78 - 77 a 0 0
Turkeys 169 67 164 a 0 0
Ducks 42 8 41 a 0 0
Geese 1 2 1 a 0 0
Other - 4 - a 0 0
Total 2 199 1 486 2 181 1 472 2 0
a Breakdown by species not available from 1970 interim report.
The level of camphechlor in the four positive samples was in the range
of 0.11-0.50 ppm as shown in Table 4.
TABLE 4. NUMBER OF ANIMAL AND POULTRY SAMPLES SHOWING A SPECIFIC AMOUNT
OF CHLORINATED HYDROCARBON INSECTICIDE RESIDUES
(Parts per million - fat basis)
Insecticide 0.01 0.11 0.51 11.01 2.01 4.01 6.01 7.01 15.01
to to to to to to to to to
0.10 0.50 1.00 2.00 4.00 6.00 7.00 15.00 above
Animal
Aldrin 13 1
Benzene hexachloride 479 37 2 1 3 1
Chlordane 1 1
Dieldrin 1 156 169 8 1 1 1
DDT and metabolites 924 1 341 229 113 39 12 5 7 1
Endrin 23 4
TABLE 4. (cont'd)
(Parts per million - fat basis)
Insecticide 0.01 0.11 0.51 11.01 2.01 4.01 6.01 7.01 15.01
to to to to to to to to to
0.10 0.50 1.00 2.00 4.00 6.00 7.00 15.00 above
Heptachlor 637 114 1
Lindane 456 48 1
Methoxychlor 20 40 10 2 2
Toxaphene 2
Poultry
Aldrin 3 3
Benzene hexachloride 275 19
Chlordane
Dieldrin 1 363 274 2
DDT and metabolites 312 1 512 284 63 11 6 1
Endrin 75 10 2
Heptachlor 276 36 1
Lindane 192 5
Methoxychlor 6 19 2 1
Toxaphene 2
Methods of residue analysis
The recommended method for the residue analysis of camphechlor
involves a sulfuric acid-Celite 545 column cleanup followed by
dehydrochlorination and gas chromatography with electron capture
detection. The sulfuric acid column removes fat and oils, and the
dehydrochlorination gives a characteristic, reproducible pattern for
dehydrochlorinated camphechlor. If additional clean-up is required,
this can be accomplished by Florisil column chromatography. Details of
this and other methods are given by Hercules and by Zweig (1972). It
should be noted that unequivocal identification of camphechlor in
samples of unknown history cannot be achieved by these or any known
chromatographic methods other than combined gas chromatography-mass
spectrometry.
National tolerances
The following tolerances for camphechlor residues in raw
agricultural crops have been established and were in effect as of May
1973 in the United States of America, Canada, Germany, and the
Netherlands:
United States of America:
Soybeans 2 ppm
Pineapples
Bananas (0.3 ppm in edible pulp) 3 ppm
Grain barley oats, rice, rye, sorghum grain,
wheat, cotton-seed) 5 ppm
Crude soybean oil 6 ppm
Fruits (stone, pome, citrus, cane, and
strawberries)
Nuts (hazel, hickory, pecan, walnut)
Meat fat (beef, sheep, goat, swine, horse)
Vegetables (beans, black-eyed peas, broccoli,
brussels sprouts, cabbage, cauliflower,
carrots, celery, collards, corn, cowpeas,
eggplant, green beans, horseradish, kale,
kohlrabi, lettuce, lima beans, okra, onions,
parsnips, peanuts, peas, peppers, radishes,
rutabagas, snap beans, spinach, tomatoes) 7 ppm
Canada:
Oats, rye, wheat, pineapples 3 ppm
Barley, grain sorghum, rice 5 ppm
Fruits (citrus, pears, strawberries)
Meat fat (cattle, goats, sheep, swine)
Vegetables (beans, black-eyed peas, broccoli,
brussels sprouts, cabbage, cauliflower,
celery, eggplant, kohlrabi, lettuce, okra,
onions, peas, tomatoes) 7 ppm
Germany:
Pears, strawberries, raspberries, cherries,
plums 0.4 ppm
The Netherlands:
Fruit, vegetables (except potatoes) 0.4 ppm
Australia:
Fruit 3 ppm
Appraisal
The data evaluated and recommendations made in this monograph
addendum refer only to camphechlor meeting FAO specifications
AGP:CP/43-
Camphechlor is widely used as a pre-harvest foliar treatment for
the control of a variety of insect pests on cotton, oil seed crops,
cereal grains, vegetables, fruits, and nuts. Control of external
livestock pests is also a major area of use in many countries.
Recent investigations (unpublished) using absorption and
gas-liquid chromatography have revealed that camphechlor can be
separated into at least 175 ClO-polychloro compounds including
Cl6, Cl7, Cl8, Cl9 and Cl10 derivatives. One toxic component
has been shown to be 2,5-endo 2,6-exo, 8, 9,
10-heptachlorobornane.
Analytical methods based on gas chromatography are available for
the identification and quantitation of camphechlor by comparison with
a standard sample of FAO specification camphechlor. The GLC trace
gives multiple peaks and it is convenient to measure the total area
under the whole trace but preferably to dehydrochlorinate the sample
and compare the height of the major peak with the corresponding peak
of a dehydrochlorinated standard.
Residues on plants resulting from the application of camphechlor
consists of unaltered camphechlor. Decline in camphechlor crop
residues is believed to be primarily the result of evaporation. There
is no evidence to indicate the presence of camphechlor conversion
products in weathered crop residues.
Camphechlor residues in animals treated with or fed camphechlor
can accumulate in the fat, although the storage level is much less
than that of most other chlorinated hydrocarbon pesticides.
Equilibrium with the exposure level is quickly achieved. Rapid
elimination of the residue from the fat occurs when input of
camphechlor is stopped. Evidence to date indicates extensive
degradation in mammalian systems, with excretion of water-soluble
products, 60% of which is chloride ion.
Camphechlor is useful for controlling a variety of arthropod
pests of vegetables. Since camphechlor is not systemic, foliage
applications result in camphechlor residues in the edible parts of
root crops only indirectly through contact at harvest. Traces of
camphechlor in the soil may also lead to incidental residues.
Camphechlor is applied to bananas for the control of a number of
species of leaf-eating caterpillars. Analytical data show that the
residue is confined to the peel of the banana; none occurs in the
edible pulp. Residues on mature banana fruit resulting from the
application of camphechlor at the maximum rate do not exceed the
recommended tolerance of 2 ppm.
Use of camphechlor on pineapples is confined to Puerto Rico for
the control of the Batrachedin moth. Two spray applications at the
maximum rate of 2.25 lb camphechlor per acre properly timed for the
control of this pest resulted in residues at harvest of 1.3 ppm to 2.7
ppm. The recommended tolerance is 2 ppm.
The refining of vegetable oils to produce products suitable for
human consumption normally removes the entire residue present on the
oil seed. However, United States surveys have shown that trace residue
of camphechlor occasionally occurs in refined oils. To accommodate
these occasional residues, a tolerance of 0.5 ppm camphechlor is
recommended.
RECOMMENDATIONS
As no acceptable daily intake could be established no tolerances
are recommended. Following officially acceptable use in various
countries residues of camphechlor can occur in the following
commodities up to the levels indicated.
The figures apply to the total camphechlor residue determined by
gas-chromatography.
Guidelines
Fat of meat of cattle, sheep, goats and pigs 5 ppm
Broccoli, brussels sprouts, cabbage, celery,
collards, eggplant, kale, kohlrabi, lettuce,
okra, peppers, pimentos, spinach, tomatoes,
barley, rice (rough), rye, sorghum, bananas
(whole), pineapple, beans (snap, dry, lima),
peas, cauliflower, oats, wheat, shelled nuts,
carrots, onions, parsnips, radishes, rutabagas 2 ppm
Soybeans, peanuts (ground-nut), cotton-seed oil
(refined), rape-seed oil (refined), soybean
oil (refined), peanut oil (refined), maize,
rice (finished) 0.5 ppm
Milk and milk products (fat basis) 0.5 ppm
FURTHER WORK OR INFORMATION
Required (before an acceptable daily intake can be established)
1. Adequate toxicological information on camphechlor as
currently marketed, including a carcinogenicity study.
2. Comparative studies evaluating the toxicological hazard
associated with polychlorinated camphene of different manufacture
used in worldwide agriculture.
3. Before recommendations can be made concerning residues
from the use of camphechlor, other than that conforming to FAO
specifications, information is needed on the composition, uses,
and residues arising from such products.
Desirable
1. Further results of research now in progress on the
chemical composition and the metabolism of individual components
of camphechlor conforming to FAO specifications.
2. Information from supervised trials (in progress) designed to
determine the residues likely to be found in fat of poultry and
in eggs from ingestion of feed containing residues.
3. Data on residues in fat of cattle in areas where tick
control requires dipping shortly before slaughter.
4. Information on the need for use on vegetables and cereals
at application rates and frequencies that would require a residue
limit greater than that recommended.
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