REPORT
of the
M I R E X
ADVISORY
COMMITTEE
Revised March 1, 1972
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REPORT OF THE MIREX ADVISORY COMMITTEE*
TO
WILLIAM D. RUCKELSHAUS, ADMINISTRATOR
ENVIRONMENTAL PROTECTION AGENCY
Revised March 1, 1972**
*Established Under Provisions of Section 4.c. of the Federal
Insecticide, Fungicide, and Rodenticide Act.
**0riginal report dated February 4, 1972.
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CONTENTS
Page
Letter of Transmittal v
Membership of the Advisory Committee vi
Introduction 1
I. Nature and Extent of Problems 5
A. Imported Fire Ant 5
B. Other Pests Controlled by Mi rex 9
1. Western Harvester Ant 9
2. Texas Leaf-Cutting Ant 9
3. Other Ants 10
4. Yellow Jackets 11
II. Present Control Methods and Alternatives 12
A. Present Methods 12
B. Alternative Methods 17
1. Current Insecticidal 17
2. Possible Future Non-Insecticidal 19
III. Benefit-Risk Evaluation 22
IV. Residue Estimates 27
A. Soil 27
B. Water 27
C. Natural Food Chains 28
D. Edible Food 33
1. Plant 33
2. Animal 34
3. Seafood 34
E. Man 37
F. Projections of Expected Environmental Load 39
V. Toxicology 42
A. Acute and Subacute Toxicity 42
B. Reproductive Effects in Mammals 43
C. Carcinogenicity and Mutagenicity 44
D. Toxicity to Aquatic Life 46
E. Toxicity to Wildlife 49
F. Absorption, Metabolism and Excretion 50
G. Biochemical 51
iii
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VI. Miscellaneous 52
' A. Chemistry 52
B. Tolerances 52
C. Possible Analytical Interferences and Misinterpretations 52
D. Analytical Confirmation 53
Conclusions 54
Recommendations 61
Appendices
References 63
Persons Appearing Before the Committee 69
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UNIVERSITY OF FLORIDA
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
UflCHIM; (USEAHCM IXHNSIOK
DEPARTMENT OF FOOD SCIENCE
PESTICIDE RESEARCH LABORATORY
GAINESVILLE. FLORIDA 326O1
March 1, 1972
Mr. William D. Ruckelshaus
Administrator
Environmental Protection Agency
Washington, D. C. 20460
Dear Mr. Ruckelshaus:
On behalf of the membership of the Mirex Advisory Committee, I am
pleased to submit the attached revised report of March 1, 1972. In order
to meet the statutory deadline, the February 4 report inadvertently contained
several statements and interpretations that had not been approved by the
entire committee^ Consequently, a revision was considered necessary in
order to reflect the more significant changes.
It is the opinion of the undersigned that the revision which begins
with the last sentence on page 13 could be misinterpreted to mean that
Lofgren et al. (1970) concluded these trials were a failure since total
eradication was not achieved. In reality, Lofgren and co-workers clearly
stated that all of the problems encountered in the eradication trials were
surmountable and concluded from their data that elimination of the imported
fire ant from very large isolated areas may be technically feasible.
It was on the evaluation of the eradication trials that the undersigned
reached an empasse with several members of this committee, thereby allowing
no possibility for both sides of the controversy to be equitably reflected
in the revised report. This difference of opinion on the Advisory Committee
is certainly understandable since it reflects the same divergent views that
exists within the scientific community most closely associated with this
general subject.
Please accept my apologies for the delay these revisions have caused
in having a final printing of the Report of the Mirex Advisory Committee.
If we can be of any further assistance in clarifying any statements in the
report, please do not hesitate to contact any member of the committee.
Sincerely yours,
C. H. Van Mid del em
Chairman
Mirex Advisory Committee
pts
Attachment
COU_EOE OF AGRICULTURE SCHOOL. OK FOREST RESOURCES AND CONSERVATION COOPERATIVE EXTENSION SERVICE
AGRICULTURAL. EXPERIMENT STATIONS CENTER FOR TROPICAL. AGRICULTURE
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MEMBERSHIP OF MIREX ADVISORY COMMITTEE
C. H. Van Middelem, Ph.D., Chairman
Pesticide Research Laboratory
Food Science Department
University of Florida
Gainesville, Florida
Gerald J. Bakus, Ph.D.
Department of Biological Sciences
University of Southern California
Los Angeles, California
J. R. M. Innes, Ph.D.
Bionetics Research Labs., Inc.
Bethesda, Maryland
Charles Lincoln, Ph.D.
Department of Entomology
University of Arkansas
Fayetteville, Arkansas
Leo D. Newsom, Ph.D.
Head, Department of Entomology
Louisiana State University
Baton Rouge, Louisiana
Jack L. Radomski, Ph.D.
Pharmacology Department
School of Medicine
University of Miami
Miami, Florida
*************
David L. Bowen
Secretariat to Committee
Environmental Protection Agency
VI
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INTRODUCTION
Mirex (Dodecachlorooctahydro-1,3,4-metheno-2H cyclobuta[cd]-
pentalene) has been used extensively during the past decade in
the southeastern states for the control of the imported fire ant,
Solenopsis saevissima richteri Fore!. A suit filed by the
Environmental Defense Fund in August 1970 in the U.S. District
Court for the District of Columbia sought an injunction and
declaratory judgement to restrain the Department of Agriculture
in its efforts to eradicate the imported fire ant.
In a separate case, involving DDT, this same court held on
January 7, 1971, that the Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA) requires the Environmental Protection
Agency (EPA) to initiate the administrative process for cancelling
the registration of a pesticide whenever there is a substantial
question about its safety.
On March 18, 1971, EPA sent a notice to the Allied Chemical
Corporation to cancel the registration of products containing
Mirex. This action was based on a substantial question about
the safety of use of this chemical. Rather than accept the
cancellation, the firm requested that the matter be referred
to an advisory committee as is its right under the FIFRA. This
committee consisting of six scientists was appointed on September
24, 1971, by the Administrator of EPA from a list of names furnished
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by the National Academy of Sciences. The following Charge was
given to the Mi rex Advisory Committee:
The Environmental Protection Agency is presently eval-
uating the use of the pesticide Mi rex. The Agency's
decision concerning the continued registration of Mirex
will involve balancing its benefits against its dangers.
Thus, the Agency must determine and weigh (1) the nature
of the benefit conferred by the use of Mirex or, put
another away, the magnitude of the social cost of fore-
going the use of Mirex, against; (2) the nature and mag-
nitude of the foreseeable hazards associated with the use
of Mirex.
In order to assist the Agency's determination, the
Committee is charged to consider and evaluate all relevant
scientific evidence concerning the use of Mirex, partic-
ularly, for fire ant control and to prepare a report and
recommendations concerning the scientific issues raised
by such use. More specifically, the Committee is charged
to consider the scientific evidence and, based thereon,
express its opinion and recommendations concerning, inter
a!ia, (1) the nature and extent of the problem posed~~5y
the fire ant and the other insects at issue; (2) the
effectiveness of the several types of control measures
which utilize Mirex (e.g., localized use to control
local infestations of fire ants; area-wide use to con-
trol the spread of fire ants; and a multi-state program
to achieve the eradication of the fire ant); (3) the
benefits expected to be achieved by each such control
program, measured against the damage which will occur
if no control were undertaken; and (4) the availability
and effectiveness of, and the hazards connected with,
alternative control measures.
With respect to the hazards associated with the several
uses of Mirex, the Committee is charged to consider
the scientific evidence and, based thereon, express its
opinion and recommendations concerning, inter alia, the
nature, scope-, and possibility of occurrence of any (1)
direct hazard to the user and to the general public; (2)
hazard to vegetation; (3) hazard to non-target verte-
brate and invertebrate animals; and (4) hazard to the
environment generally.
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This report follows an outline which was designed to comply
with all aspects of the Committee charge. It is divided into two
primary sections, the first covers advantages and disadvantages
associated with the use of Mirex for the control of the imported
fire ant and other insects as well as possible present and future
alternative means of control. The second section deals primarily
with possible hazards associated with Mi rex uses.
Initial evaluation included the nature and extent of the problem
involving not only the imported fire ant but other insects controlled
effectively with Mirex. The advantages and disadvantages of the
various present control measures are covered. Currently available
alternative insecticidal control measures as well as possible future
non-insecticidal control techniques presently under investigation
are discussed. The benefits expected to be achieved by the various
control procedures are evaluated against the possible risks to
man and his environment from the continued use of Mirex.
The second section of the report is devoted to an evaluation
of the possible hazards to man and his environment as a result
of past, present and future use of Mirex for the control of the
imported fire ant and other insects. This section includes an
evaluation of the significance of Mirex residues found in soils,
water, natural food chains, human food and man himself as a result
of past Mirex applications. Projections of expected environmental
load are made as a result of past applications and future use of
this toxicant on a more restricted basis. Various aspects of the
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very limited available toxicological information on Mi rex are discussed
t
including acute and subacute toxicology, reproductive effects,
carcinogenicity, mutagenicity, absorption, metabolism and excretion.
A brief section is devoted to the chemistry of Mirex, established
tolerances, possible analytical interferences and suggested confirmation
techniques.
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I. NATURE AND EXTENT OF PROBLEMS POSED BY THE IMPORTED FIRE ANT
AND OTHER PESTS THAT ARE CONTROLLED BY THE USE OF MI REX
A. Imported Fire Ant.
The identity of the imported fire ant, presently known
as Solenopsis saevissima richteri, is in a state of flux. Some
authorities consider that two species have been introduced into
the United States: others think that only color forms are involved,
All agree that a "dark form" first noticed near Mobile, Alabama
about 1920 never dispersed widely and now is known to be the
dominant form in only a restricted area of northeast Mississiopi.
It is similarly agreed that a different ant, smaller and more
aggressive, the so-called "red form" appeared during the late
1930's or early 1940's. It spread quickly across the Gulf Coast
states and now occurs throughout much of the 9-state area from
Texas to North Carolina (Markin 1970).
The pest status of the imported fire ant is controversial.
Claims have ranged from its being of no importance as a pest to
its being the most dangerous and destructive of all pests in the
infested area. Early statements emphasized injury to crops,
particularly potatoes, seeds and young seedlings of a variety of
crops (Wilson and Eads 1949, Wilson 1951, Culpepper 1953). It is
now considered to be more important as a pest of humans than of
agriculture. Previous claims about the destructive nature of the
species as a pest of crops, livestock, and wildlife were greatly
exaggerated. During the last decade, a considerable change has
occurred in views on the pest status of the species.
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Clearly, the imported fire ant is an important nuisance pests.
It stings viciously when disturbed and its presence in areas used
extensively, such as lawns, playgrounds, school grounds, parks,
cemeteries and gardens, interferes with normal human activity
(Mills 1967). Its presence in areas heavily used by small children
is especially undesirable and dangerous.
The true significance of the imported fire ant to human health
has probably not been evaluated properly in the past. A medical
survey in Alabama, Georgia and Mississippi was recently completed
involving almost 2500 medical doctors (Triplett 1971). This survey
shows that for each year in the period 1969-71, over 10,000 patients
were treated as a result of imported fire ant stings. Over 50% of
the patients reported in this survey required medical treatment
for secondary infections. A significant number of the patients
were reported to have experienced some degree of allergic response,
with a small percentage suffering such severe reactions that they
progressed into a state of anaphylactic shock. These reactions
are considered to be at least on a par with anaohylaxis caused
by stings of other venomous Hymenoptera.
Information accumulated during the last 15 to 20 years shows
that the imported fire ant is of virtually no importance as a
direct pest of crops, livestock or wildlife. Occasionally, it
may attack seedling plants such as potatoes, corn, and cabbage
and the flowers and fruit of okra. Indirectly, the imported fire
ant is more important as an agricultural pest. Because of its
sting, it causes serious problems for hand laborers harvesting
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crops such as strawberry, pecan and tuna nuts. Baled hay
is especially attractive to the ants and larqe numbers may con-
gregate under bales that are left in the field for several days.
Workers handling the infested bales may be stung severely. Farm
operations such as mowing improved pastures with sickle type
mowers, mowing hay meadows and combine harvesting of crops are
made more difficult and expensive by the presence of imported fire
ant mounds. On heavy clay soils especially, the mounds may be so
large and durable that wear and tear on equipment is excessive.
In addition, time is lost in attempting to avoid the mounds and
in cleaning and repairing equipment.
The ecological status of the imported fire ant in the United
States has not been sufficiently assessed. It is a general predator
and scavenger, relying heavily for food upon insects and related
arthropods that comprise more than 95 percent of its diet (Hays
1958, Hays and Hays 1959, Wilson and Oliver 1969, Markin 1970).
It appears to have competitively displaced the ant species
Solenopsis xyloni, S_. geminata and Pogonomyrmex badius, (Wilson
1951). It has also displaced the Argentine ant, Iridomyrmex
humilis, from some areas. Less is known about its effect on
populations of other species of ants.
Its role in agricultural ecosystems is difficult to establish
as is the case with most species of general predators. It is an
effective predator of the sugarcane borer, Diatraea saccharalis,
(Hensley et^ al_. 1961) and the lone star tick, Ambylomma americanum,
(Harris 1971). It preys heavily upon the eastern subterranean
termite, Reticulitermes flavipes, and many species of leafhopoers
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(Wilson and Oliver 1969). On the other hand, it preys on pre-
f daceous insects to the extent that some entomologists believe
that it seriously upsets the ecology of an area (Markin 1970).
It also tends some species of aphids and protects them from
attack by predators and parasites. Thus, its presence may be
desirable in some situations and undesirable in others.
Acreage infested by the imported fire ant has continued to
expand each year as illustrated in the following table:
Rate of spread of the imported fire ant (Markin 1970, USDA 1971d)
Year Infested Acres (est.)
1932 200,000
1947 2,000,000
1959 26,000,000
1963 31,000,000
1967 106,000,000
1971 126,500,000
These data show that there was a 13-fold increase in number
of acres infested during the 12-year period 1947-59. During the
period 1959-71 an additional 5-fold increase occurred despite the
conduct of large-scale control and eradication programs and the
imposition of Federal and State quarantine and regulatory action
that restricted the movement of infested material, especially
nursery stock. Efforts to prevent movement into new areas have
been notably unsuccessful. There are indications that the pest
may be approaching the northern limits of its range but the extent
of the area that it may eventually infest in the United States
cannot be predicted on the basis of present knowledge.
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B. Other Pests in the United States that are Controlled
Effectively by Use of Ml rex.
In addition to the imported fire ant, the following
species of locally important pests are controlled effectively
by the use of Mirex applied as bait formulations.
1. Western harvester ant.
The western harvester ant, Pogonomyrmex occidentalis,
infests millions of acres of rangeland of the western states.
It annoys man and animals by its painful sting, denudes areas
of vegetation an average of more than 80 square feet around
its mounds, collects seeds, cuts off seedling grass as it
emerges, and damages the shoulders of highways. The unsightly
appearance of the mounds and ability of the species to inflict
a painful sting on humans make undesirable its presence in parks,
playgrounds, lawns, and other areas heavily used by people
(Crowell 1963, Lavigne 1966, Race 1966).
2. Texas leaf-cutting ant.
The Texas leaf-cutting ant, Atta texana, is a serious
pest of pine seedlings, hardwood trees and cereal and forage
crops in some areas of east Texas and west-central Louisiana.
In heavily infested areas, damage to buds, needles and bark of
all species of pine makes it impossible to establish natural
reproduction. Seedling pines are often destroyed in such areas
within a few days of planting. Foliage from a wide variety of
plants is used by the ants as the substrate upon which they
culture a fungus that provides their only known food. Nest
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areas of this species are characterized by numerous crescent-
shaped mounds about one foot in diameter and from 5 to -14
inches in height. The mounds are confined to areas ranging
from about 100 square feet to more than an acre. Huge colonies
develop and foraging ants may range for hundreds of feet to
obtain suitable foliage. These ants are often particularly
destructive to gardens and shrubbery in rural and suburban areas.
In the American tropics leaf-cutting ants are the most destruc-
tive pest of subsistence, "slash and burn" agriculture (Bennett
1958, Echols 1966, Cherrett 1969).
3. Other ants.
Other ants of several species tend and protect aphids,
scales and mealybugs and thus aggravate the injury-producing
capacity of such pests. It has long been recognized that control
of these pests is often best accomplished by controlling the ants.
A classic example is control of the mealybug wilt of pineapple in
Hawaii by the control of ants, especially Pheidole megacephala.
It provides transportation and protection for the pineapple
mealybug, Dysmicoccus brevipes, which is responsible for this
serious disease of pineapple. Spread of mealybug wilt in the
pineapple plantations of Hawaii during the late 1920's was so
rapid that it appeared probable the industry could no longer
exist there. The industry was saved by discovery of the rela-
tionship between the disease and ants and the development of
effective control measures for the latter (Smith 1971).
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4. Yellow jackets.
Yellow jackets, Vespula spp., are ground-nesting
social wasps characterized by aggressive behavior and a painful
sting. Allergic reactions to their stings, similar to those of
many other Hymenoptera including the imported fire ant, are not
uncommon. Populations of these wasps appear to have increased
significantly during the last few decades around parks and picnic
areas in many sections of the United States. The availability of
an abundance of food left by picnickers and campers appears to be
a major cause of the increase in population. Their occurrence in
large numbers in heavily used recreational areas is especially
undesirable because of their aggressive behavior and the fact that
a small percentage of the human population is hypersensitive to
their venom (Parrish 1963, Keh et al. 1968).
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II. PRESENT CONTROL METHODS AND ALTERNATIVES
A. Present methods
Technical Mi rex, dissolved in soybean oil and sprayed
onto corncob grits produces a bait consisting of 0.3 percent
Mi rex, 14.7 percent soybean oil and 85 percent corncob grits.
This bait, used for control of the imported fire ant since 1962,
rapidly replaced other insecticides used in cooperative Federal/
State programs. Currently Mi rex is used exclusively in these
programs except for nurseries and other highly specialized situ-
ations that demand use of long-residual, persistent insecticides
such as heptachlor or dieldrin.
Mirex bait is applied at the rate of 1.25 pounds per acre
containing only 1.7 grams of the toxicant. This represents the
application of an almost unbelievably small amount of insecti-
cide on a per acre basis in comparison with the rates of
application of other insecticides. Few of these are effective
for control of agricultural pests at rates less than 100 times
the amount of Mirex applied for control of the imported fire
ant. Only some insecticidal seed dressings for control of
seedling pests approach its effectiveness (Hays and Arant 1960,
Bartlett and Lofgren 1961, 1964).
The development of such a highly effective and comparatively
selective method of pest control is considered an outstanding
achievement in applied entomology. "Mirex approaches many of
the requirements for an ideal control chemical for the ant. It
is relatively specific as formulated, rather than a broad-spectrum
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toxicant. It is comparatively nontoxic to vertebrates and to many
other animals. It is a highly toxic and advantageously slow-
acting stomach poison for the ants, and can be formulated as an
attractive bait with potential for low-dosage broadcast in granular
form. The chemical itself is exceedingly stable and of low vola-
tility, although present bait formulations do lose their attrac-
tiveness and effectiveness in a relatively short period of time"
(Mills 1967).
Mi rex bait is highly attractive to the foraging workers and
readily accepted by the ant. Its delayed toxic effects allow the
workers to return to the colony with it where it enters the complex
trophallactic food chain and eventually destroys the colony.
Mi rex bait can be used effectively for control of the imported
fire ant on acreage ranging in size from individual mounds in home
lawns to the total infested area of the United States. Its most
effective use from the standpoint of control of the ant would be
for treatment of the entire infested area and the least effective
method would be individual mound treatment (Markin 1971 a). Three
properly timed applications of Mi rex bait, applied at aporooriate
intervals during a period of 1 year to 18 months at the rate of
1.25 pounds per acre per application, a total of 5.1 grams of
Mi rex per acre, to the entire infested area would almost eliminate
the imported fire ant from the United States.
Results of three large-scale eradication trials (Lofgren et al.
1970) showed Mirex bait to be highly effective for control of the
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imported fire ant but eradicaton was not acheived. They also
demonstrate the occurrence of a number of important operational
and technical problems. One of the most important of these is
the inadequacy of available survey and detection methods to
monitor their effectiveness.
An eradication program for the approximate 126 million infested
acres has been considered and rejected by the USDA (USDA 1971c).
The current position of the USDA is that, although it may be techni-
cally feasible, eradication is no longer an objective of the Federal-
State Cooperative Control program because of financial and logistical
limitations. Moreover, they were concerned about the possible adverse
environmental effects resulting from such large-scale use of Mirex
bait.
Next to treatment of the entire infested area in the country,
large-scale programs would give the best results. The residual
activity of Mirex bait is so short that reinvasion of treated
areas occurs rapidly. It appears that the imported fire ant,
unassisted by man, may spread at the rate of about 5 to 10 miles
per year. Clearly, the smaller the area treated, the more
rapidly reinvasion may occur. The individual homeowner, farmer,
cattleman, or a municipality, for example, might have to apply
one application of-the bait per year to suppress populations of
the imported fire ant to acceptable levels.
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Two or three applications of the bait over large areas might
accomplish the same objective for a period of several years.
There would be substantially less of the bait per unit area in
such a program than where applications were made by the indivi-
dual. Individuals, having less efficient means of applying
extremely small quantities of bait, tend to overtreat. However,
individuals would treat only those areas where the presence of
the fire ant constitutes a problem whereas areawide treatments
would be made to substantial areas where the presence of the
fire ant does not constitute a problem. Thus, the relative
amount of Mi rex used by the two methods of treatment might not
differ widely when the total amount applied to an area is
considered.
The present program proposed by the U.S. Department of Agri-
culture (USDA 1971c) for future use in control of the imported
fire ant has been described as follows:
"...After thorough consideration of all relevant factors,
the Department's position on imported fire ant control is as
follows:
1. Mi rex bait will be applied aerially to those
areas where the ant is causing trouble, where the property
owners have expressed concern, and where the State and
local governmental agencies have requested Federal co-
operation in a control program. Under the plan, forested
areas which are not prime fire ant habitat and sensitive
areas such as estuarine areas, and State and Federal game
refuges will not be treated. Application pilots will be
briefed with respect to all sensitive areas, including
water, and instructed to avoid application to those
areas. Compliance will be closely monitored by ground
personnel and aerial supervision.
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2. The Federal Quarantine will be continued to
minimize further spread of infestations. In support
of regulatory activities, outlying isolated infesta-
tions and extensions of peripheral areas beyond the
regulated areas will be treated... .
The above program is designed to provide relief to those
people most seriously affected by the imported fire ant. The
proposed cooperative program would be carried out in those
States where there is an interest and funds are available for
State and/or local participation."
The U.S. Department of Agriculture clarified this proposal
by answering the following three questions posed by the Com-
mittee:
"1. How do we define prime wildlife habitat?
With respect to the imported fire ant control program,
prime wildlife habitat is described as Federal and
State game refuges, estuary and marsh areas, wooded
areas bordering streams, rivers, and other bodies of
water. Heavily wooded areas are not treated because
they do not support imported fire ant populations.
2. What is the largest contiguous block that would be treated
under this one treatment concept?
In open general fanning areas without streams or heavily
wooded areas, 50,000 or more contiguous acres may be
treated. As a general guideline, if 75 percent or more
of the area is open, an electronic guidance system is
employed. Cutouts such as rivers, heavily forested
areas, and game refuges are marked on the pilot's map,
and the recording tape in the aircraft marks these areas
that are cut out. When less than 75 percent of the total
area is to be treated, small aircraft are used due to the
many cutoffs required.
3. What do we plan to do along the peripheral areas?
Treatments are planned in peripheral areas when
there is threat of spread to uninfested States
or to a new area of an infested State. These
treatments are to be made in support of the
Federal quarantine."
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Economic thresholds, more properly tolerable or comfort thres-
holds, have not been established. For instance, the current position
of the USDA states in part: "Mirex bait will be applied aerially to
those areas where the ant is causing trouble, where the property
owners have expressed concern, and where the State and local govern-
mental agencies have requested Federal cooperation in a control
program" (USDA 1971c). Obviously, these are not objectively deter-
mined thresholds. In an eradication or suppression program the
presence of any imported fire ant may be critical, but in a control
program, treatment thresholds become critical.
Control of other species of ants is normally obtained by indivi-
dual nest treatment or by broadcasting Mi rex bait by hand or ground
equipment with treated areas being from several square feet to a
few acres. An exception would be treatment of crops where ants are
part of an agricultural problem, such as the ant-mealybug complex
on pineapples. Here the entire crop acreage might be treated as
well as adjacent unpopulated dry areas.
Yellow jacket treatment with Mi rex bait is an area treatment
not an individual nest treatment. However, the bait is dispensed in
containers visited by the insects and not released into the environ-
ment. The baited areas would not exceed a square mile or so.
B. Alternative Methods.
1. Current insecticidal
Chlordane, dieldrin, heptachlor and related compounds
are quite effective for control of the imported fire ant, are con-
venient to apply as granules, and give incidental control of ticks,
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chiggers, and some other pests (Blake e_t al_. 1959, Lofgren et al_.
1961, Lofgren ejt a]_. 1964). These alternative materials are inex-
pensive and available. Risk of acute toxicity to people is nil with
formulations and dosages used.
These same insecticides are also quite effective in controlling
many other ant problems in outdoor situations. However, some leaf-
cutting ants are not readily controlled by these insecticides and
fumigation is required. Fumigation with either methyl bromide or
carbon bisulphide or use of arsenic and sulphur dioxide introduces
an acute toxicity hazard to humans.
Baits have a unique advantage for yellow jacket control because
the insects seek it out. Chlordane is reported to be an effective
alternative for Mirex in yellow jacket bait (Grant ejt ^1_. 1968).
Nest control with alternative insecticides is easy if the nest can
be found, but this is often difficult.
The choice between Mirex bait and granular heptachlor and re-
lated materials for control of the imported fire ant and most other
pest species of ants in outdoor situations should be made on the
basis of environmental hazards associated with the two types of
uses. The effective dosage rates of these alternative chemicals
far exceed that used in Mirex bait. Mirex bait was developed
for use in imported fire ant programs because of its relatively
low environmental hazard. Adverse environmental impact of hepta-
chlor, dieldrin and chlordane would be so much greater than that
of Mirex bait that their use would be precluded except in very
restricted situations. Moreover, these alternative insecticides
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are currently registered only for application to limited sites
that are not devoted to the production of food and feed crops.
2. Possible future non-insecticidal
Research, until relatively recent time, has emphasized
chemical control of the imported fire ant since this is the only
practical and effective means of control. Possible alternative
methods to insecticidal control are currently receiving increased
attention primarily by the USDA and also through its cooperative
research grants with various universities. Possible alternatives
to chemical control include biological control with parasites,
pathogens and predators, sterilization, insect hormones, pheromones
and genetic manipulations. The imported fire ant is a remarkably
successful species in the southeastern United States when compared
to other members of the same genus. This phenomenon, not uncommon
with introduced pests, strongly suggests that the imported fire ant
has escaped from biological control agents which are effective
in South America.
Control of the imported fire ant through the possible use
of parasites, pathogens and predators probably offers the best
potential for a successful biological control method. At pre-
sent, there are no known biological agents that are effective
in limiting the imported fire ant infestations in the U.S.
Recent taxonomic studies (Buren 1972) have shown that the most
abundant form of the imported fire ant in the U.S. (red form)
is located only in the interior part of Brazil and possibly
in sections of Paraguay and Bolivia. These areas are remote
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and not easily accessible. A parasitic ant associated with
the black forms of the fire ant was located in Argentina and
Uruguay but its usefulness in the control of the imported fire
ant is doubtful. Natural parasites of the imported fire ant
in the U.S. have been studied for a number of years in an
attempt to find some whose effectiveness could be increased
by either mass rearing or environmental modifications. This
research is currently being expanded to include pathogens of
the imported fire ant.
Considerable research has already been conducted on ant
pheromones but more should be done. Some research has been
initiated on insect hormones but much more remains to be
done before this technique can be properly evaluated as a
possible future control technique. A more thorough under-
standing of the chemical and physical communication system
of the ant colony could possibly lead to new control
approaches.
Because research on the genetics of ants in general is highly
complex, insufficient information is available to assess the practi-
cality of genetic manipulations as a means of controlling the imported
fire ant. For example, attempts to develop basic techniques for
inducing mating or artifically inseminating ants in the laboratory
have not been successful. These techniques are a prerequisite to
laboratory and field studies.
Sterilization is probably an impractical technique for
imported fire ant control for several reasons. There are no
current methods available for mating or rearing large numbers
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of males in the laboratory. Mating of the imported fire ant
occurs during flights throughout the summer months. These
flights usually are localized and not readily predictable.
Consequently, proper timing of sterile male release to coin-
cide with mating flights would be extremely difficult. The
long lifetime of imported fire ant colonies would also com-
plicate the procedure because releases of sterile males would
have to be made over a long period of time. Applications of
chemical sten'1 ants directly in the field with a bait would
also be impractical because they are not species specific,
therefore, other invertebrates and vertebrates would be ex-
posed to the sterilant.
It should be emphasized that at the present time there
are no biological control measures that could be successfully
employed in the near future for the control of the imported
fire ant. Increased research on these non-chemical control
measures is underway and even further expansion is encouraged.
One must be tempered, however, by the reality that a future
successful biological agent might also pose significant
potential hazards to man and his environment.
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III. BENEFIT-RISK EVALUATION
The nuisance effects, public health importance and indirect
effects on agriculture of the imported fire ant are of such mag-
nitude that effective control measures must be made available
for treatment of areas where the need for control exists. The
hazard to human life alone that is posed by hypersensitivity of
a small percentage of the population due to the sting of this pest
requires the availability of effective control measures. Con-
trol of the pest in home lawns, parks, playgrounds, schoolyards
and other recreational areas is imperative if use of these areas
is not to be denied to many individuals. It is generally agreed
that the imported fire ant is a species that the United States
would be much better off without.
Recent findings indicated that Mi rex residues have been found
in varying concentrations in a wide variety of organisms and natural
food chains (Markin 1970, Duggan 1971, USDI 1971, Wilson, N.L. 1971),
Evidence of delayed toxic effects on some species of crustaceans
(Lowe et_a\_. 1971, Ludke eŁ aj_. 1971) and general paucity of infor-
mation on ecological effects of large-scale application of Mi rex
call for reduction in use of this chemical until additional data
are available on the significance of this information.
Consideration of the environmental impact of Mirex applications
plus the technical and operational difficulties encountered in
treating large areas have caused the USDA to reject an eradication
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program for the entire infested area of the Unites States. The
1971 USDA program using Mirex bait for the control of the imported
fire ant avoided treating areas such as heavy woodland, water,
estuaries and other poor ant habitats (USDA 1971c). However,
the proposed Federal-State Cooperative Control program for
1972 would still involve the treatment of very large areas
other than estuarine, heavily forested areas and State and
Federal game refuges. Lack of information on such points
as the metabolic fate of Mirex in plants and animals and the eco-
logical effects of accumulation of substantial residues of the
chemical by non-target species does not permit a final, unequivocal
evaluation of the benefit-risk ratio involved in its continued use.
It seems worthwhile, therefore, to evaluate the available options
for future control of the imported fire ant in the United States
on the basis of the information that is available.
Clearly, some level of control of the pest must be provided
and use of Mirex bait can provide control at far less demonstrated
adverse effect on the environment than any of the other available
insecticides.
Treatment of the total infested area with three properly timed
applications of Mirex bait at the rate of 1.25 pounds of bait per
acre per application (a total of 3.75 pounds of bait per acre con-
taining only 5.1 grams of Mirex) would be by far the most effective
method for suppressing imported fire ant populations. However, it
would involve treatment of large acreages where the presence of the
imported fire ant does not constitute a problem. The environ-
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mental impact of such treatment is too poorly understood and the
expense too great to justify a program of such magnitude. The
USDA is to be commended for changing its position and instituting
programs involving control on more limited acreage.
Large-scale treatments for suppression and prevention of
additional spread would be much more effective for control of
the ant than treatment of limited areas. Treatment by this
method would be by skilled, experienced personnel with sophisti-
cated equipment so that the amount of insecticide applied per
unit area would be minimal. The problem of re-infestation from
adjacent untreated areas would be reduced depending upon the size
of the area treated. Further spread of the pest would be slowed.
The disadvantages of this method are the same, on a reduced scale,
as for treatment of the total area infested in an attempt to
achieve eradication.
Treatment according to the proposal described in the USDA
position on imported fire ant control would result in adequate
control of the pest and in a substantial reduction in further pol-
lution of especially sensitive areas with Mirex. However, the
method of control described would still result in the treatment
of large areas of rangeland, unimproved pastures, land in soil
bank and conservation reserve, and cropland where the imported
fire ant may be abundant but does not pose a problem to people
or interfere with agricultural operations. If the USDA were to
amend its position and consider such areas the same as heavily
forested areas, estuarine areas, and State and Federal game refuges,
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the program would then be one aimed at controlling the species in
all areas where it is a pest rather than attempting to suppress
populations over large areas.
Treatment of individual properties is the least effective
method and would require up to one application per year because of
the high rate of reinfestation from untreated areas. This method
of treatment would allow the ant to infest the total area to which
it is adapted in a relatively short time. It would result in a
considerable amount of overtreatment per unit area because of the
lack of proper equipment for applying the bait and the lack of
training and skill in use of the bait by the property owner. The
advantages of this method would be to confine treatment to those
areas only where the imported fire ant is a problem and to place
the cost of controlling the pest on the individual involved. Ef-
fectiveness and safety of individual property treatments could be
enhanced by an increased educational program through the responsible
state and local agricultural agencies. Because of emphasis on
large-scale suppression programs in the past, proper instructions
at the local level for small-scale treatment may not have re-
ceived adequate attention.
Treatment by trained personnel in an organized program would
avoid the problems of overtreatment and direct exposure of un-
trained persons to the Mi rex bait. If such treatments were
limited to specific locations where there was a demonstrated
need, environmental disturbance would probably be less than
from treatment by individuals and control would be much better.
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It would appear that a method of control combining the best
features of the USDA proposal with treatment confined to the mini-
mum area of demonstrated need would have the most favorable benefit-
risk ratio.
Benefits from use of Mi rex bait to control the western harvester
ant, the Texas leaf-cutting ant, the ant-mealybug complex on pineapple
and yellow jackets far outweight the possible risks.
In summary, the Committee is unanimous in concluding that the
benefits from the continued use of Mi rex for the control of the im-
ported fire ant and certain other pest soecies of ants and yellow
jackets outweight considerably the possible risks, assuming that the
recommendations in this report are implemented. The benefits to
man and his environment are clear, but the risks are largely unknown
at the present time.
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IV. RESIDUE ESTIMATES
A. Soil (Including Sediments, etc.)
Following an application of Mirex bait (1.7 grams per acre)
the theoretical amount of Mirex in a standard 3-inch soil sample
would be approximately 4 ppb. Mirex residues in soils from open
pastures following normal Mirex aerial treatments, have generally
ranged from 0.1 to 10 ppb (Collins and Davis 1971, Markin et al.
1971 a). Mud samples taken from pond bottoms and drainage ditches
have yielded Mirex residues in about the same range as has been
reported for soils (Collins and Davis 1971). Sediment samples
from freshwater ponds pretreated with Mirex contained residues
ranging from 0.01 to 21 ppb (Markin eŁ al_. 1971 a). An exception
to these rather low concentrations would be the analysis of mud
from four ponds pretreated with 0.1 ppm Mirex which resulted in
reported residues from 0.09 ppm, 7 days after treatment to as high
as 32.7 ppm in one pond 112 days after application (Van Valin
et^ a\_. 1968). From these studies, it was concluded that residues
of Mirex are very stable in mud, water and aquatic vegetation.
B. Water
Mirex is essentially insoluble in water, therefore, its
residues reported in fresh or sea water were probably adsorbed
on particulate matter suspended in the water. Most analyses of
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both fresh and salt water samples indicated Mi rex residues at
below the limit of detection (0.01 ppb). Residues of 0.5 to
1.0 ppb were found in water samples taken from ponds pretreated
with 0.1 and 1.0 ppm Mirex, respectively (Van Valin et_ a\_. 1968,
Collins and Davis 1971, Duke 1971, Markin ejt al_. 1971a, Markin
1971b, Maxwell et al.. 1971).
C. Natural Food Chains
Following a single application, most of the Mirex bait
on the ground is promptly picked up by the foraging fire ants and
carried into their mound for transfer to other ants in the colony.
The ants do not consume all of the Mirex, some remains inside the
discarded grit and is returned to the soil surface. Among ter-
restrial communities, unused Mirex grits may be consumed directly
by various insect scavengers (e.g., certain ants, crickets, wood
roaches, ground beetles). These scavengers are in turn preyed on
by certain spiders, reptiles, amphibians and insectivorous birds
and mammals. The toxicant may be leached from the bait, washed
or occasionally blown directly into aquatic habitats or carried
there via food chains by immigrating organisms (Ludke et al.
1971, Markin 1971b, USDI 1971). Mirex bait is apparently
resistant to leaching in seawater (Lowe e_t aj_. 1971) but
is easily leached out by fresh water (Ludke e_t al_. 1971).
Preliminary information indicates that Mirex is not readily
degraded by biological systems and organisms. Since Mirex is
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essentially insoluble in water, it probably becomes adsorbed to
organic detritus and to sediments (Odum je_t a\_. 1969, Maxwell
ejt al_. 1971). Species of freshwater and estuarine communities
(e.g., crayfish, river shrimps, penaeid shrimps, fiddler crabs
and blue, crabs) are general scavengers and accumulate Mi rex by
consuming detritus and sediments (Darnell 1958, Miller 1961,
Tagatz 1968). Under laboratory conditions some of these soecies
appear to assimilate Mirex as efficiently as would be expected
of their natural food sources (calculated from data in Lowe
e_t a]_. 1971). The levels of Mirex residues that are lethal to
certain aquatic crustaceans are far below those for fish,
amphibian, avian and mammalian species (Baker 1964, Dewitt
et al_. 1964, Naber and Ware 1965, Tucker and Crabtree 1970,
Allied Chemical Exhibit No. 21, 1971, Lowe et al_. 1971,
Ludke et^ jil_. 1971, USDI 1971). These curstaceans are eaten by
fishes and by birds and mammals that consume both crustaceans
and fishes.
Certain aquatic algae have been found to contain relatively
high values of Mirex compared to residues in surrounding bottom
sediment and water (Markin et^ al_. 1971a). Mirex residues can usually
be detected in most fish taken from waters near treated areas,
including edible species such as bass, bream, catfish and
mullet. Bass and bream usually contain less than 0.5 ppm in
their edible portions. Wild catfish and mullet have been
found to contain residues as high as 1.0 to 5.0 ppm (Baetcke
et al. 1971, Markin 1971b). Catfish residues, in general,
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have been found to decrease rapidly following a period of time
since Mirex was applied, but wild freshwater catfish have been
reported to contain up to 0.65 ppm Mirex six months after
treatment (Collins and Davis 1971). Commercially raised catfish
from artificial ponds in areas that had received a countywide
coverage of Mirex bait contained no Mirex in 50 samples
taken from 25 separate pond sites (Hawthorne jB_t a]_. 1971).
Mirex residues have been detected in a significant per-
centage of marine-estuarine animals monitored in treated areas
including oysters, whelks, brachyuran and anomuran crabs and
shrimps. Residue levels in these marine species are usually
less than 1.0 ppm. Organisms that are believed to feed directly
on Mirex bait and the predators of these organisms appear to show
a rapid loss of Mirex residues 12 months after the original
treatment. Most of these invertebrates exhibited a 90% or greater
decrease in Mirex residues during this period. However, a slower
decrease was noted for some vertebrates (Allied Chemical Exhibit
21, 1971b, Markin 1971b).
Mirex residue levels are extremely low (<0.05 ppm) or
nondetectable in terrestrial plants and in phytophagous animals
selected from Mirex-treated areas. Most terrestrial inverte-
brates have been found to contain less than 0.1 ppm but general
scavengers such as crickets and wood roaches may consume Mirex
bait directly and have been reported to contain Mirex residues
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ranging from 10 to 30 ppm. However, within a year after treat-
ment, formerly depleted species are still present but contain
Mi rex residues that have decreased considerably. Predaceous
arthropods, such as spiders, have been found to contain higher
residues than general invertebrate populations. Spiders may
contain in excess of 1.0 ppm Mirex one year after treatment.
Predaceous amphibians and reptiles that have been monitored
usually contain relatively high levels of Mirex (1.0 to 5.0 ppm).
Several toads have been found with residues of 10 ppm or higher.
Birds, as a group, appear to contain relatively high levels
of Mirex. Most insect-eating birds collected in or near a treated
area contained Mirex residues in excess of 1.0 ppm, with a few
having as high as 10.0 ppm or even higher. The only wild bird
egg samples that have been analyzed are from cattle egrets, five
of which averaged approximately 13 ppm. It is not known what
adverse effect, if any, residues of this level in eggs might have
on reproduction. Much higher levels fed to chickens, mallard ducks
and bobwhite quail resulted in no apparent adverse reproductive
effects (Naber and Ware 1965, Heath 1971). Mirex is a very stable
compound chemically and residues in certain species are remarkably
persistent. For example, adult snowy egrets contained up to 0.64 ppm
and nestlings were analyzed to have up to 3.5 ppm Mirex one year after
treatment. Insectivorous land birds have been reported to contain
from 0.22 to 9.1 ppm Mirex six to twelve months after treatment
(Markin 1971 a).
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Mi rex residues can be detected in most small mammals following
bait treatment, but are quite variable and apoarently depend upon
the feeding habits of the species. Most mammals contain less than
1.0 ppm Mirex. An apparent exception is the shrew, which is an
insect feeder. Two specimens were found to have residues of 6.6
and 41.3 ppm. In one study involving a large number of monitored
samples, most raccoons were found to contain residues well below
1.0 ppm, but a small percentage was observed to have values in the
range of 2 to 5 ppm. Raccoons have been noted to contain as high
as 1 ppm Mirex one year after final treatment (USDI 1971).
Mirex residue levels, as well as rates and direction of
transfer in the natural food chain, are difficult to interpret
or predict for several reasons: (1) Numerous organisms (e.g.,
omnivores, detritus feeders, filter feeders) cannot be classified
into traditional trophic levels, their feeding habits change from
larval stage(s) to adult and many are opportunistic feeders as
adults (Bakus 1969). (2) Certain species may move considerable
distances (e.g., marsh birds, raccoons, blue crabs) and carry
residues with them. (3) Tidal flushing, storms and hurricanes
can suspend sediments in fresh water lotic and lentic systems
and in estuaries. Spring turnover in lakes (upmixing of nutrients
from bottom sediments) may also cause resusoension of Mi rex-
bearing sediments. (4) Mirex residues measured in the past may
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be partially confused with the polychlorinated biphenyl, Aroclor
1260, and/or Dechlorane, which is chemically identical to Mirex.
From the data currently available, it is evident that Mirex
is reaching some non-target organisms as a result of previous
large-scale application for the control of the imported fire
ant. It is also apparent that Mirex can be transferred through
simple two-level food chains (Lowe Łt al_. 1971) as well as further
up certain food chains. Current and future restrictions on
applications of Mirex to sensitive areas plus the possible reduc-
tion in dosage rates should result in a significant decrease in
future Mirex residues at various levels of natural food chains.
D. Edible Food
1. Plant
In considering all types of biological samples for
Mirex residues, the smallest amounts appear to be found in plants
(Markin et. aj_. 1971a). Earlier work by Allied Chemical Corporation
indicated that no Mirex residues could be found in a large selection
of field and vegetable crops (Allied Chemical Corporation 1971a).
There is some indication that extremely low levels of Mirex may
be translocated from the soil into growing plants such as
bahiagrass roots and foliage. These were reported to contain
from 0.3 to 17 ppb Mirex (Markin et al_. 1971a).
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2. Animal
Milk from cows fed 3 weeks on a daily ration with
0.01 ppm Mirex contained no detectable Mirex, whereas from 0.02
to 0.08 ppm was detected in the raw whole milk from cows fed 3
weeks on a diet containing 1.0 ppm Mirex (USDA 1971b). Milk
from cows that had grazed in previously treated areas contained
from 2 to 8 ppb. An average of 0.01 ppm Mirex was reported in
the fat of raw milk selected from 12 cows grazed in previously
treated areas (Baetcke ejt al_. 1971). No detectable Mirex residues
(sensitivity 0.3 ppb) were found in 60 milk samples selected from
5 different states involved in the use of Mirex for fire ant
control.
Fat samples taken from 63 of 75 beef cattle raised in areas
in Mississippi and Georgia, where Mirex has been used to control
the imported fire ant, contained very low levels of Mirex (from
0.001 to 0.126 ppm). In general, the Mirex residues detected in
these samples comprised a very small fraction of the total organo-
chlorine residue detected (Ford et al_. 1971). Mirex residues
ranging from 0.05 to 1.6 ppm were found in adipose tissues of
deer, quail, wild turkey and beef cattle (Baetcke e_t al_. 1971).
3. Seafood
A recent sampling by the Food and Drug Administration
of commercial fishes in Louisiana waters resulted in the detection
of Mirex residues in 10 out of 21 total samples. These residues
ranged from 0.01 to 0.18 ppm on an edible portion basis. The
FDA has not encountered any Mirex residues in other foods
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tested, including its Total Diet Studies (Duggan 1971). Mirex
residues can usually be detected in most fish from treated areas
including edible species such as bass, bream and catfish. Usually
less than 0.5 ppm Mirex is found in bass and bream. Catfish and
mullet have been found to contain 1 to 2 pom Mirex immediatelv
following treatment, although subsequent monitoring indicated that
within 24 to 48 hours the residues drooped to below the 0.5 pom
level (Markin e_t a\_. 1971a). This raoid decrease in Mirex residues,
suggests that these bottom-feeding fish had ingested individual
Mirex grits just prior to the time of analysis.
In marine estuaries, marshes and bays which have been treated,
Mirex residues have been found in almost all marine animals
including oysters, shrimps, crabs, bottom-feeding and swimminq
fishes. Three days after a third aerial anolication of 0.3% Mirex
bait to an entire area, Mirex residues of from 0.32 to 2.59 pnm
were detected in oysters, shrimps, crabs, catfish and mullet
(Markin 1970).
The buildup of Mirex residues in uncaqed channel catfish
has been reported (Collins and Davis 1971), whereas caged catfish
acquired almost no Mirex. One plausible explanation is that uncaged
fish obtain their Mirex through the food chain, whereas the caged
fish did not have access to the natural energy sources. Buildup
of Mirex in uncaged channel catfish increased from no residues
detected 10 days after an aerial application (0.3% bait) to the
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pond and surrounding drainage area, to 0.65 ppm Mirex six months
after application. On the other hand, only 0.03 ppm was detected
in the caged fish six months after application (Collins and Davis
1971).
No detectable Mirex residues were found in 50 samples of
commercially raised catfish in Mississippi (limit of sensitivity
0.01 ppm) (Hawthorne e_t al_. 1971). The lack of detectable Mirex
residues in this study would indicate that the claim of wide-
spread contamination by Mirex appears to be unfounded. It is also
doubtful that Mirex residues could be responsible for the deformation
or death of fishes (Hawthorne e_t al_. 1971).
The edible portion of bluegill fish was found to contain
from 0.12 to 0.39 ppm Mirex, whereas largemouth bass contained
0.44 to 0.76 ppm in their edible tissue (USDA 1971a). Catfish
caught in the mouth of two rivers in Georgia contained 0.008
to 0.030 ppm Mirex (Curley 1971). Oysters from Savannah, Georgia,
contained from 0.004 to 0.036 ppm Mirex, whereas oysters from the
Gulf Breeze, Florida and Charleston, South Carolina areas contained
no detectable Mirex.
Very low Mirex residues were found in a variety of marine
life from the Savannah, Georgia area where Mirex bait had been
applied several times (Markin et al_. 1971c). The monitoring
program, in general, failed to indicate that detectable Mirex
residues were accumulating in marine life throughout the remainder
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of the southeastern United States, even though Mirex residues could
have reached the sampled marine environment via streams and rivers
draining previously treated areas.
In general, it would appear that Mirex residue concentrations
currently found in soils, water, vegetables and field crops as well
as in meat and milk selected from areas previously treated with
Mirex, are so low as to be insignificant as far as any possible
hazard to humans. If there is any possible hazard in certain
seafoods, it would appear to be restricted to several bottom-
feeding fishes in areas that had recently been treated several
times with Mirex.
E. Man
Very little data are available on possible residues of
Mirex in human beings as a result of treatments for the control
of the imported fire ant. Only since April 15, 1971, have the
contracting laboratories, Human Monitoring Survey of the States
Services Branch of the Division of Pesticide Community Studies
in the Environmental Protection Agency, been looking at possible
residues of Mirex in the human samples which they collect and
analyze. Prior to that time, analyses would not have revealed the
presence of Mirex, if indeed any were present. Since that time,
contract laboratories have reported the results of more than 700
adipose tissue analyses. These were collected by 55 pathologists
in 23 states, including Macon and Atlanta, Georgia; and Pensacola,
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Florida; areas where Mirex has been used for the control of the
imported fire ant. In only 12 of these samples have peaks been
observed in the area where Mirex elutes on the gas chromatograph.
Two of these were in Louisville, Kentucky; one in Little Rock,
Arkansas; one in Atlanta, Georgia; two in Macon, Georgia; and
three in Togus, Maine. The highest value observed was 1.03
ppm in the adipose tissue of one of the specimens from Macon,
Georgia (Yobs 1971). It must be emphasized that identification
of Mirex by gas chromatography in these samples is tentative at
best. Considerable doubt is placed on this identification by
the presence of significant concentrations of polychlorinated
biphenyls (PCBs), several of which are known to elute in the
same area on the gas chromatograph. Confirmatory identification
of these samples is currently underway but the final results are
not available. Further doubt, on the validity of these analytical
identifications, is cast by the consideration that half of the
12 samples were reported from three cities which are a considerable
distance from areas previously treated with Mirex for the control of
the imported fire ant. It should also be noted that the same
chemical substance has been widely used as a fire retardant under
the trade name Dechlorane. There is the possibility that these
human tissue levels, suspected to be Mirex, may be due to exposure
to Dechlorane. Actually, it would be extremely surprising if
Mirex were found in human tissue at this time, considering the
relatively modest quantites of the insecticide used for the control
of the imported fire ant and the fact that very little or no
Mirex has been found in the human food chain.
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F. Projections of Expected Environmental Load
Trends in the accretion, if any, of Mi rex in the
environment cannot be projected with any degree of confidence
at the present time. Additional comprehensive studies need to
be conducted in order to effectively evaluate the result of past
and current applications of Mirex. As in the case of most other
similar persistent pesticides found in the environment, the routes
of movement of Mirex have not been well documented. Improved
sampling methods are essential for valid censusing of key natural
populations of terrestrial and aquatic organisms. Current data
from monitoring and total diet studies by the Food and Drug
Administration indicate that very little or no Mirex residues
were found in man's food supplies (Duggan 1971).
Many of the key environmental species in the areas treated
by Mirex for the imported fire ant have been monitored in the
past. These monitoring studies are continuously being improved
for the future projections of the environmental impact by the
continued use of Mirex. Currently available monitoring information
clearly indicates that residues of Mirex are appearing in most
invertebrate and vertebrate animals that are in close proximity
to treated areas. Some invertebrate species that may feed
directly on Mirex bait in treated areas suffer significant
population declines for a period of time following treatment.
However, after a year of no further Mirex treatment, these
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invertebrate populations appear to recover in the previously
treated areas. There is no available information to indicate
that any vertebrate populations have been adversely affected
despite rather high Mirex residues in certain terrestrial animals
such as toads, lizards and insect-eating birds. Vertebrates
exposed to Mirex in the field generally contain considerably
less of the chemical than that required to affect laboratory
animals in controlled studies.
Most monitoring studies in the past few years have been
conducted in areas that had been subjected to eradication tests,
where three closely spaced applications of Mirex were applied
more or less indiscriminately to all parts of the environment
including estuaries, marshes and other sensitive areas.
Current and future control programs will attempt to avoid all
sensitive areas in the environment and will involve only one appli-
cation per year versus the previous three-application treatment.
Continuous improvement in the Mirex-latex bait should assure
that less Mirex will be available to non-target organisms.
There is also a very good possibility that a lower dosage level
of active toxicant will be utilized to control the imported fire
ant. It is projected, therefore, that future Mirex residues
encountered in the treated areas of the environment should
show a continuous decline.
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Since Mirex is a very persistent pesticide and apparently
is not readily metabolized in nature, its residues, however
minute, are expected to remain in the environment for the fore-
seeable future. However, because of the extremely small quantity
used and the restrictions that have been and will be enforced,
the environmental load of Mirex is not considered to be alarming
in comparision with other persistent pesticides currently in the
environment.
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V. TOXICOLOGY
A. Acute and Subacute Toxicit.v
Very little data are available on the acute and subacute
toxicity of Mirex to experimental animals and none on its chronic
toxicity. One single study reports that Mirex has an acute LD5Q
of 365 mg/kg in female Sherman rats (Gaines and Kimbrough 1970).
This figure is somewhat lower than that reported previously in
Sherman strain rats which was 740 mg/kg in males and 600 mg/kg in
females (Gaines 1969). In addition, the chronicity factor of
Mirex was determined by the technique described by Hayes (1969).
The chronicity factor is defined as the single dose LD5Q in mg/kg
divided by the 90-dose LD5Q in mg/kg per day. The 90-dose oral
LD^Q of Mirex was found to be 6 mg/kg per day giving a chronicity
factor of 60.8 (Gaines and Kimbrough 1970). This chronicity factor
is by far the highest observed of any pesticide to date. It may be
compared to a chronicity factor of less than 5.6 for DDT and of
12.8 for Dieldrin, both of which are considered to be highly per-
sistent compounds. Male and female rats were also fed Mirex at 0,
1, 5 and 25 ppm in the diet (10 animals per group) for 166 days.
The livers of these animals were examined by light microscopy in
both males and females. At the 5 ppm feeding level, approximately
one-half of the rats developed significant, but minimal, pathologic
changes. They exhibited slightly enlarged liver cells, vacuolated
cytoplasm and occasional inclusions. At the 25 ppm feeding level,
most of the rats had definitely enlarged liver cells which were
multinucleated with smooth or vacuolated cytoplasm, which showed
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cytoplasmlc inclusions and biliary stasis. Examination of these
livers by electron microscopy showed an increase in smooth
endoplasmlc reticulum, free ribosomes, lipid vacuoles, myelin
figures and osmophilie-dense bodies.
In other subacute toxicity experiments, M1rex was fed to rats
in the diet for 13 weeks at concentrations of 0, 5, 20, 80, 320
and 1280 ppm (Larson 1968). Deaths were observed at the highest
dose level and growth suppression at 320 ppm. Enlarged livers and
pathologic changes including swelling and vacuolatlon of liver
cells were found at 80 ppm. The same investigator also fed Mi rex
to dogs daily at concentrations of 0, 4, 20 and 100 ppm. Deaths
were observed at the 100 ppm feeding level, but at 20 ppm no effects
were observed. Further studies demonstrated that Mirex was absorbed
through skin of rabbits producing toxic effects. Two of 10 rabbits
died when a 5% Mirex 1n corn oil solution was applied at a rate of
10 mill1l1ters per kilo.
B. Reproductive Effects In Mammals
Very few experiments have been conducted on the reproductive
effects of Mirex on experimental mammals. Female Sherman rats were
fed 25 ppm of Mirex in the diet for 45 and 102 days (Gaines and Kim-
brough 1970). The males to which these females were bred were exposed
to Mirex in their diet only during the seven-day breeding period. In
these animals, significantly fewer offspring were born alive and
fewer survived to weaning than the control rats. Furthermore, 33
to 46% of the offspring of these breedings developed cataracts,
whereas none were observed 1n the control animals. At the
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44 -
5 ppm feeding level, however, no reproductive effects were observed.
Further experiments indicated that the pathologic effects of Mirex
on the eyes of newborn rats is primarily due to the ingestion of
Mirex during the suckling period.
Another study involved large scale feeding of two strains of
mice to measure the effect of 5 ppm Mirex fed in the daily diet
(Ware and Good 1967). With one strain, Mirex produced a signifi-
cant increase in parent mortality, whereas parent mortality was
not affected in the other strain of mice. In both strains of
mice, the Mirex diet resulted in reduced litter size and number
of offspring produced per day.
C. Carcinogenicity and Mutagenicity
Only one experimental evaluation has been reported on the
possible carcinogenicity of Mirex (Innes eŁ ^1_. 1969) but none on
its mutagenicity. Mirex was selected as one of the pesticides
to be tested at the Bionetics Research Laboratory in a unique
massive screening program for tumorigenicity. In this study, a
total of 130 compounds was evaluated of which 104 were pesticides.
Seven known carcinogens were included as positive controls as well
as 19 industrial chemicals. The compounds to be studied were selected
on the basis of widespread usage, suggestive chemical structure and
evidence of toxicity described in the literature suggesting a potential
hazard to man.
Each compound was tested by two routes of administration, oral
and subcutaneous, in two hybrid strains of mice. Eighteen male and
18 female mice of each strain were utilized for each test procedure.
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In the subcutaneous test, Mi rex was administered in a maximally
tolerated single dose of 1000 mg/kg. In the oral experiments, a
dose of 10 mg/kg per day was given from the 7th to the 28th
day. The mice were then fed for the duration of the experiments
at the level of 26 ppm in the diet. All mice in both experiments
were sacrificed approximately 18 months after the beginning of the
experiment.
In the subcutaneous experiment, almost all of the 72 mice sur-
vived the 18-month test period to sacrifice. The primary tumors
observed in these animals were reticulum cell sarcomas Type I (10/72),
pulmonary adenomas (3/72) and hepatomas (7/72). Of the 72 mice to
which Mi rex had been administered, a total of 20 were found to bear
tumors. The incidence of mice developing reticulum cell sarcomas
and hepatomas as well as the total tumor-bearing mice fed Mi rex
was significantly different from the controls at the 99% level.
In the oral administration tests, all mice died prior to the
completion of the experiment at 18 months. Twenty-nine of 72 mice
developed hepatomas, compared to 14 of 338 control mice (99% signi-
ficance).
The significance of this bioassay is enhanced by the demon-
stration that the seven known carcinogens were found clearly to be
tumorigenic by this testing procedure. Mirex by oral admini-
stration in this bioassay procedure was judged to have a relative
risk of 0.945 by comparison with an average of the seven known car-
cinogens. This would mean that by this bioassay procedure Mirex is
very close to being equal in carcinogenic potency to the seven known
carci nogenic compounds.
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From the results of this testinq procedure in which Mirex,
fed at relatively high dosaqes, was found to be tumorigenic in
two strains of mice of both sexes, it was concluded that this
substance is tumorigenic for this soecies. These results, however,
could certainly not be translated to man. No satisfactory testing
procedure for orally ingested carcinoqens to which man may be ex-
posed in his diet has been developed. In lieu of this, reliance
must be placed on the concept that man is but one species of
animal and that testing must be carried out in as many species
as possible. If a consistent result is obtained in a number of
species, this result probably has significance for man. Therefore,
it is urgently desired that Mirex be tested for carcinogenicity in
other species so that conclusions about its possible carcinogenic
potential for humans can be reached.
D. Toxicity to Aquatic Life
Exposure to Mirex under laboratory conditions affects certain
estuarine crustaceans by causing irritability, loss of equilibrium,
paralysis and even death. The most susceotible soecies were found
to be juvenile brown and pink shrimp and juvenile blue crabs, whereas
pinfish apparently were not affected by the Mirex treatments (Lowe
et_ al_. 1971). The toxicity of Mirex bait is directly related to
temperature, that is, there is a greater manifestation of lethal
effects at higher temperatures (McKenzie 1970). Studies on juve-
nile brown shrimp verify the phenomenon of delayed toxicity
exhibited by Mirex which has been previously reported in several
other aquatic and terrestrial species (Mahood e_t aj_. 1970,
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Markin 1970, Ludke ejt al_. 1971, Markin et al_. 1971a, and W. E. Martin,
written communication 1971).
Under controlled laboratory conditions, decreases in popu-
lation density were observed to occur in ciliate protozoa when
placed in a suspension of 1 ppb Mirex (Duke 1971). Two species
of freshwater crayfish (Procambarus blandingi and P_. hayi) were
found to be extremely sensitive to Mirex under laboratory con-
ditions (Ludke et^al_. 1971). An earlier study of adults of another
species of crayfish (P_. clarki) indicated that they were not
sensitive to Mirex (Muncy and Oliver 1963). This was confirmed
by a recent study of P_. clarki in south-central Louisiana which
indicates that Mirex is not an important threat to the crayfish
industry (Markin ert al_. 1971b). Such discrepancies in results
between laboratory experiments and field studies emphasize the
species specific effects of Mirex on animal populations.
Mortality of adult crabs and shrimps was observed in a
small pond on Cat Island after exposure to higher than normal
dosages of Mirex (Markin 1971b). Similar mortalities were not
noted in other ponds or a bay on the same island.
In 1969 a cooperative USDA and USDI experiment was initiated
at Charleston, South Carolina to study the effects of Mirex on
crab and shrimp populations (Duke 1971). Mirex was applied to
a 2-square mile area of marshland and estuaries. Samples of
crabs and shrimps within the treated areas were collected at
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biweekly intervals during the three-bait application and for
10 weeks afterwards and analyzed for Mirex residues. Mirex
residues in crabs averaged 0.02 ppm during the experiment.
There was no observed mortality and crabs and shrimps could
be caught at all times following the Mirex bait applications.
Paralysis or death of fiddler crabs may occur within one
to several weeks following the ingestion of a single Mirex
bait granule under controlled laboratory conditions (Lowe
ejt al_. 1971). However, in the Cat Island experiment (Markin
1971b), fiddler crab populations were observed to be high at
the time of the third Mirex application. No population decline
was observed at varying lengths of time following the last of
the three applications.
It has been reported that wild catfish in Mirex-treated areas
may feed directly upon the bait or obtain Mirex through the food
chain. Commercial catfish in 25 ponds in Mississippi from areas
where Mirex was used contained no detectable Mirex at 0.01 ppm
limit of sensitivity of the method (Hawthorne et a]_. 1971).
Another study (Maxwell 1971) reported no adverse effects or
mortality to catfish fed 10 and 15 ppm Mirex in their diet for
6 weeks.
There is little evidence to corroborate the lethal effects
of Mirex found under controlled laboratory conditions with
those in natural aquatic communities. Based on all available
monitoring data, there is also little evidence at this time of
any serious hazards to populations of fish and crustaceans as a
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result of standard Mi rex bait applications for the control of
the imported fire ant. However, previous sampling methods
usually have not been adequate for valid censusing of these
natural populations. Additional and much more comprehensive
studies should be conducted on population densities of Mirex-
sensitive aquatic organisms in their natural habitats.
E. Toxicity to Wildlife
Although a decline in populations attributed to Mi rex
has been reported for crickets, oil-loving ants, and ground
beetles (Wilson, N.L. 1971), there is no evidence available to
indicate that these populations are permanently affected. A number
of 1050 values nas been established for Mi rex and these values
indicated that this pesticide is rather low in its toxicity to
rats and a few species of adult birds (Larson 1968, Gaines 1969,
Gaines and Kimbrough 1970, Baetcke e_t a^. 1971).
Despite the fact that significant Mi rex residues are being
found in numerous key environmental species being monitored in
areas previously treated with multiple aerial applications,
there is no evidence to date of any significant adverse effects
on natural populations of fishes, amphibians, reptiles, birds
and mammals. Investigations are still required to evaluate any
possible latent effects of Mirex residues on key vertebrate
species in the field to determine possible adverse effects on
their behavior, brood size and survivorship. There is always
the possibility of subtle adverse effects on certain wildlife
species subjected to long-term, sublethal residues of Mirex
in treated areas.
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F. Absorption, Metabolism and Excretion
Even less data are available on the absorption rate
and excretion of Mi rex in experimental animals than on the bio-
logical effects. A single unpublished and incomplete report is
available on the administration of carbon-14 labeled Mirex
(Matthews 1971). Following a single dose to rats, the radio-
activity of various tissues and excreta were determined. As
might be expected, Mirex was found to be stored in adipose
tissue. Data from this report indicate that Mirex has a half-
life of at least 25 days, which is considerably longer than the
half-life values cited for other persistent pesticides. This
half-life value for Mirex probably constitutes an underestimation
of the extrapolated data (Matthews 1971). Thin-layer chromatog-
raphy of extracts of the tissues and excreta revealed the presence
of no metabolites. Mirex was incubated with homogenized liver
fractions of rats, mice and rabbits for a period of up to 36
hours. These studies indicate that there is no evidence of any
metabolites of Mirex. Very preliminary information from the U.S.
Forest Laboratory at the Research Triangle indicated that Mirex
at the concentrations used exhibited no effect on populations
of soil microorganisms, and that Mirex was not found to be
degraded by the microorganisms under the conditions of the
experiment (Matthews 1971).
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G. Biochemical
Fragmentary evidence is available which indicates that
Mirex is a stimulator of the liver microsomal oxidative metabolism
pathway (Baetcke et al_. 1971). Proliferation of the endoplasmic
reticulum and an increase in oxidative metabolism has been
observed.
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VI. MISCELLANEOUS
A. Chemistry
The chemical name for Mirex is dodecachlorooctahydro-1,3,4-
metheno-2H cyclobuta[cd]pentalene and the empirical formula is
C10C112- Mirex has a closed 10-carbon structure, with all valence
points chlorinated. It is nonflammable and insoluble in water.
Since Mirex is totally chlorinated and has no free reactive groups
readily available for chemical attack, it is a very stable compound
chemically (Markin 1970).
B. Tolerances
Established tolerances for residues of Mirex in or on raw
agricultural commodities were published in the Federal Register (36
FR 3965 March 3, 1971) as follows: 0.1 ppm (negligible residue) in
the fat of meat of cattle, goats, hogs, horses, poultry, and sheep;
0.1 ppm (negligible residue) in milk fat and eggs; and 0.01 ppm
(negligible residue) in or on all other raw agricultural commodities.
C. Possible Analytical Interferences and Misinterpretations
It is quite possible that some earlier Mirex residues, particu-
larly in aquatic samples, may have been partially misidentified.
As with many other chlorinated pesticides, Mirex can be confused
with PCBs eluting from a gas chromatograph. For example, Aroclor
1260 has an almost identical retention time with Mirex on many
commonly used gas chromatographic columns. Adequate techniques
for separating PCBs from organochlorine pesticides were not avail-
able until 1970 and were not developed and tested for Mirex until
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more recently. In one particular study (Markin ejt al_. 1971c), the
first analyses of samples by a standard cleanup method indicated
that 40% contained Mi rex residues. However, utilizing a new
technique to separate Aroclor 1260 from Mi rex, it was determined
that the first analyses had been in error since part or all of
the original gas chromatographic peak could be attributed to Aro-
clor 1260.
Another possible source of analytical misinterpretation
might result if a commercial fire retardant called Dechlorane
was present in environmental samples being analyzed for Mi rex
residues. Since this contaminant is chemically identical to
Mi rex, it would be impossible to differentiate between the two
compounds by gas chromatographic or any other usual means of
analyses. Sales of Dechlorane in the past decade have been
over four times those for Mi rex during the same period (Com-
munication to Mi rex Advisory Committee by Allied Chemical
Company December 21, 1971). The distribution of Dechlorane
in the environment is unknown.
D. Analytical Confirmation
It is very important to employ adequate analytical confir-
mation techniques before publishing pesticide or PCB residue
data obtained from environmental samples. Even the use of two
gas chromatographic columns of varying polarity may not be
adequate. Further confirmation should be made by thin layer
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CONCLUSIONS
In compliance with its charge to consider and evaluate all relevant
scientific evidence concerning the use of Mirex, particularly for
fire ant control, the Mirex Advisory Committee has reached the fol-
lowing conclusions based on careful evaluation of all available data.
A. Problems Posed by the Imported Fire Ant
1. The imported fire ant currently infests more than 126,000,000
acres in nine southern states and continues to expand its range.
2. The imported fire ant is a major nuisance pest because of its
sting. Its presence restricts the use of recreational and other
public areas as well as private property.
3. The imported fire ant is a health hazard because of the
development of secondary infection and allergic reactions to its
venom. A small percentage of its victims are hypersensitive to the
venom and may suffer anaphylactic shock.
4. The imported fire ant is of relatively minor importance as
an agricultural pest. The threat of being stung interferes with
hand labor involved in the cultivation and harvest of some crops and
the mounds may damage mowing machines and combine harvesters.
5. The imported fire ant is an aggressive predator of other
arthropods including both pests and beneficial species. Present infor-
mation Is not adequate for an evaluation of its impact on the popula-
tions of these organisms. It is also a scavenger of undetermined
significance.
B. Control of the Imported Fire Ant
1. Mirex bait is effective for control of the imported fire
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ant when applied in minute amounts of active ingredient per acre.
One application usually eliminates more than 90 percent of the
mounds in a treated area. Three applications at about six-month
intervals virtually eliminates all mounds exposed to treatment.
2. Mirex bait may be used on a scale ranging from a single
application to one mound to multiple applications to the entire
infested area of the southern states. The degree of control of
the imported fire ant would be correlated with the size of the
area treated and the number of applications.
a. Individual mound treatment is the least effective of
all control programs. Broadcast treatment of individual properties
would give adequate short-term control in the areas treated. Retreat-
ment on an annual basis would be required in such a program because
of reinvasion from adjacent untreated areas. Environmental contam-
ination would be minimal. Handling of bait by untrained people
would result in the possibility of excessive application rates and
more direct human exposure than in other methods of control.
b. A publicly sponsored control program involving appli-
cation of Mirex bait as needed, based on pest population assessment,
offers the greatest relief with minimal environmental impact. Such
a program would give satisfactory control of the pest for a year
or more with one application. Subsequent single applications
would be made as needed.
c. Multiple treatment of large contiguous areas for
suppression of imported fire ant populations results in effective
control of the pest for several years and reduces reinvasion from
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untreated areas, but would do little more to alleviate the problem
than a control program such as that considered in the preceding
paragraph. Large areas where the ant is not a pest would be treated
with Mirex resulting in the possibility of unnecessary environmental
contamination and greater initial costs.
d. A successful eradication program would yield the
greatest long-term benefits. The possibility of adverse environmen-
tal impact is such that it could only be considered if success were
assured. The possibility that eradication of the imported fire ant
could be achieved with current technology is still a controversial
issue. However, eradication of the pest is no longer an objective
because of financial and logistical limitations and possible adverse
environmental effects.
3. A program involving multiple applications of Mirex bait
to the periphery of the infested areas has probably delayed, but
not prevented, continuing spread of the pest. Lack of adequate
survey methods results in treatment of some uninfested areas and
failure to treat some infested areas. Because of the size of the
infested area in the United States, effective treatment of the
peripheral areas would require repetitive application of Mirex
bait to a contiguous area that would involve millions of acres.
C. Control of Miscellaneous Pests
The Western harvester ant, the Texas leaf-cutting ant, and
other species of ant pests are controlled with Mirex bait applied
to individual nests or small areas. The most effective way of
controlling some serious agricultural pests, particularly aphids,
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scale insects and mealybugs, is to control the ants that protect
and transport these pests. Yellow jackets are nuisances in recre-
ational areas, and a small percentage of people stung are hyper-
sensitive to the venom. Mirex baits provide highly effective and
comparatively selective control for all of these pests. Compared
to effective alternative methods of control, such baits are safe
and have little, if any, adverse environmental effects.
D. Alternative Control Measures
1. For the past several years, the USDA has conducted a
continuing screening program for new, less persistent insecticides
to replace Mirex. Although several compounds have shown promise in
laboratory tests, none has proved to be an effective alternative in
field experiments.
2. Aldrin, chlordane, dieldrin and heptachlor used to control
the imported fire ant prior to the development of Mirex remain as
available alternatives. However, these compounds are currently
registered for use only for limited sites that are not devoted to
production of food and feed crops and could not be used for broad-
cast applications over extensive areas. The effective dosage rates
of these alternative chemicals far exceed that use in Mirex bait
and, therefore, their substitution is considered inadvisable.
3. A search is underway for an effective biological control
agent to replace chemical control of the imported fire ant. No
method of biological control presently under investgation shows
promise in the immediate future of effectively supplementing or
replacting chemical control.
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E. Potential Hazards Associated With the Use of Mi rex
1. No instances of any acute intoxication to users have
been reported due to the handling or application of Mi rex bait in
over a decade of use.
2. There is no evidence of damage to vegetation from the use
of Mirex bait. No significant absorption of Mirex by, or trans-
location of residues from soil into, plants consumed by man or his
domestic animals has been reported. Residues of Mirex in edible
food or feed are nonexistent or extremely low. The significance,
if any, of these minute residues to the health of man or his domestic
animals is unknown.
3. Most investigations of the effects of Mirex on inverte-
brates and vertebrates in the natural habitat have failed to demon-
strate any significant changes in their populations. Field studies
have shown significant population declines of several terrestrial
invertebrate species, most but not all of which apparently feed
directly on the Mirex bait. Sampling methods have not been
adequate for censusing some natural populations of terrestrial
and aquatic organisms. Laboratory experiments have shown toxic
effects on juvenile crustaceans exposed to low concentrations of
Mirex. Monitoring studies have indicated considerable Mirex resi-
dues in some invertebrates and vertebrates, especially those that
are preclaceous on ants and other insects.
4. Mirex residues in water appear to be non-detectable or
minimal as a result of normal Mirex treatments to control the
imported fire ant. Residues in soil occur where Mirex has been
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used and are minimal in magnitude. Mi rex residues, although
occurring at low concentrations in aquatic sediments, may be
of some biological importance because of the probable ingestion
of organic detritus and other components by bottom-feeding crusta-
ceans. Very preliminary studies indicate that Mirex residues
are not degraded by biological systems and organisms.
5. Monitoring of Mirex in certain edible food products
selected from treated areas indicates insignificant residues, if
indeed they occur at all, presently in the human food chain de-
spite the widespread apolication of Mirex during the past decade
for the control of the imported fire ant in the infested areas.
In preliminary studies, only a small percentage of human adipose
tissue samples analyzed showed the presence of suspected and
unconfirmed Mirex residues.
6. Insufficient data are available on most mammals for an
accurate evaluation of the acute toxicity of Mirex. In rats, it
exhibits a low degree of acute toxicity, but subacute studies
indicate pathologic changes in the liver at low feeding levels.
Subacute feeding experiments in dogs produced no pathological
effects at low chronic feeding levels.
7. No data are available on the chronic toxicity of Mirex
for experimental animals. Such data are urgently needed before
valid conclusions on the possible hazards of Mirex to man can be
drawn.
8. Mirex caused significant reproductive effects in rats
when fed at relatively high levels in the diet but no effects when
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fed at rates likely to occur on food or feed as a result of
applications made for control of the imported fire ant. Mirex
produced no measurable reproductive effects in bobwhite quail
or mallard ducks when fed at relatively high levels in the diet
in long-term studies.
9. Based on meager and preliminary data from a rat feeding
experiment, no metabolites of Mirex have been detected. It is
stored in the fat depots of animals and appears to have a bio-
logical half-life of at least 25 days.
10. Mirex has been demonstrated to be tumorigenic to
two strains of mice when fed relatively high dosages. However,
no conclusions can be reached concerning the carcinogenicity
of Mirex for man until it has been studied in other mammalian
species.
F. Miscellaneous
During the past decade, Dechlorane, which is chemically
identical to Mirex, has been used for numerous industrial
applications in amounts far greater than amounts of Mirex used
for imported fire ant control. The degree of environmental
pollution from this source is unknown.
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RECOMMENDATIONS
1. The registration of products containing Mirex should be
continued with labeling restrictions to minimize environ-
mental contamination.
2. Publicly supported control programs should be limited to Mirex
application, according to need based on pest population assess-
ment, to infested areas where the imported fire ant is a problem
because of use by people or interference with agricultural
operations. Estuaries and other aquatic habitats, wildlife
refuges, and heavily forested areas should not be treated.
3. Where publicly sponsored programs are unavailable, broadcast
treatment of lawns, pastures, school grounds, parks, and similar
areas by individuals is recommended instead of mound treatment.
Educational programs should instruct infested property owners
as to how Mirex can be applied for the most effective control
of the imported fire ant with minimal environmental contamination.
4. To implement control programs, much more information is needed to
establish economic or nuisance threshold levels requiring Mirex
treatment as well as on rates of reinfestation and population
recovery in areas receiving a single bait treatment.
5. Considerably more research on the possible hazards of Mirex to
man and his environment must be conducted before the role of
Mirex, as a pesticide, can be accurately assessed. Chronic
toxicity, carcinogenicity, mutagenicity, teratogenicity and the
metabolic fate of this compound in multiple species should be
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further studied. Additional work on the biological stability,
persistence and routes of movement of Mirex under field con-
ditions is needed. Continued and expanded monitoring of key
environmental carriers and selected commercially important
species for Mirex residues should be carried out with emphasis
on the detection of any significant contamination of the human
food chain. More thorough studies on the effects of Mirex on
aquatic crustaceans are needed, especially the monitoring of
population densities in the field. Greater effort should be
made to correlate laboratory and field research. Increased
research is to be encouraged for the non-insecticidal control
of the imported fire ant.
Respectfully submitted,
C. H. Van Middelem, Ph.D., Chairman March 1, 1972
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REFERENCES
Allied Chemical Corporation: Memorandum of Allied Chemical Corporation
in support of opposition to cancellation of registrations. I.F.&R.
Docket No. 146, llOpp plus appendices (1971a).
Allied Chemical Corporation: Exhibits to Memorandum in support of opposi-
tion to cancellation of mirex registrations. Exhibits 1-32 (1971b).
Baetcke, K. P., Cain, J. D., and Poe, W. E.: Mirex and DDT residues in
wildlife in Mississippi. MS submitted to Pest. Monit. J. 31pp. Sched-
uled for publication June 1972. (1971).
Baker, M. F.: Studies on possible effects of mirex bait on the bobwhite
quail and other birds. Proc. 18th Ann. Conf. S. E. Assoc. Fish and Game
Comm. 153-159 (1964).
Bakus, G. J.: Energetics and feeding in shallow marine waters. Intern.
Rev. Gen. Exp. Zoo! . 4:275-369 (1969).
Bartlett, F. J. and Lofgren, C. S.: Field studies with baits against
Solenopsis saevissima v. rich ten', the imported fire ant. J. Econ.
Entomol. 54:70-73 (T961 ) .
Bartlett, F. J. and Lofgren, C. S.: Control of native fire ant, Solenopsis
geminata, with mirex bait. J. Econ. Entomol. 57:602 (1964).
Bennett, W. H.: The Texas leaf-cutting ant. USDA Forest Pest Leaflet 23
4pp (1958).
Blake, G. H., Jr., Eden, W. G., Hays, K. L.: Residual effectiveness of
chlorinated hydrocarbons for control of the imported fire ant. J. Econ.
Entomol . 52:1-3 (1959).
Buren, W. F. : Revisionary studies on the taxonomic identity and character-
ization of the imported fire ant. MS submitted to J . Ga . Entomol . Soc .
Cherrett, J. M.: Baits for control of leaf-cutting ants. I-formulation.
Trop. Agr. Trinidad 46:81-90 (1969).
Collins, H. L. and Davis, J.: Residues of the insecticide mirex in channel
catfish and other aquatic organisms. Unpubl . presentation. 9pp 3 table.
Ann. Meet. Entomol. Soc. Amer. (1971).
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Crowell, N. N.: Control of the western harvester ant Pogonomyrmex
occidental is with poisoned bait. J. Econ. Entomol. 56:525-532 (1963).
Culpepper, G. H.: Status of the imported fire ant in the Southern States
in July 1953. USDA, Bur. Ent. PI. Quar. E-867, 8pp (1953).
Curley, A.: Report to the Surgeon General's Office on mirex in seafood
samples from Savannah, Georgia. Special Rept. 3pp (1971).
Darnell, R. M.: Food habits of fishes and invertebrates of Lake
Pontchartrain. Publ. Univ. Tex. Inst. Mar. Sci. 5:353-416 (1958).
DeWitt, J. B., Menzie, C. M., Spann, J. W., and Vance, C.: Evaluation of
chemicals. In: Pesticide-Wildlife Studies, 1963. USDI Circ. 199:
78-79, 97-112 (1964).
Duggan, R. E.: Letter to Mirex Advisory Committee dated November 11, 1971.
Duke, T. W.: Accumulation and movement of mirex in selected estuaries of
South Carolina. Unpubl. MS 95pp (1971).
Echols, H. W.: Texas leaf-cutting ant controlled with pelleted mirex bait.
J. Econ. Entomol. 59:628-631 (1966).
Ford, J. H., Hawthorne, J. C., and Markin, G. P.: Monitoring for mirex and
other organochlorine pesticides in beef cattle in the southeastern United
States. MS submitted to Pest. Monit. J. 25pp (1971).
Gaines, T. B.: Acute toxicity of pesticides. Toxicol. Appl. Pharmacol.
14:515-534 (1969).
Gaines, T. B. and Kimbrough, R. D.: Oral toxicity of mirex in adult and
suckling rats. Arch. Environm. Health 21:7-14 (1970).
Grant, C. D., Rogers, C. J., and Lauret, T. H.: Control of ground-nesting
yellow jackets with toxic baits--a five-year program. J. Econ. Entomol.
61(6):1653-1656 (1968).
Harris, W. G.: The relationship of the imported fire ant, Solenopsis
saevissima (F. Smith), to the populations of the lone star tick, Amblpyomma
americanum (Linnaeus), and the effects of mirex on populations of arthropods
Ph.D. dissertation on file Louisiana State Universtiy (1971).
Hawthorne, J. C., Ford, J. H., Collier, C. W., and Markin, G. P.: Residues
of mirex a_nd other chlorinated pesticides in commercially raised catfish.
MS submitted to Bull. Environm. Contam. Toxicol. 12pp, 1 map, 3 tabs. (1971)
Hayes, W. J., Jr.: The 90-dose LD5Q and a chronicity factor as measures of
toxicity. Toxicol. Appl. Pharmacol. 11:327-335 (1969).
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Hays, K. L.: The present status of the imported fire ant in Argentina.
J. Econ. Entomol. 51:111-112 (1958).
Hays, S. B. and Arant, F. S.: Insecticidal baits for control of the
imported fire ant Solenopsis saevissima richteri. J. Econ. Entomol.
53:188-191 (1960).
Hays, S. B. and Hays, K. L.: Food habits of Solenopsis saevissima richteri
Forel. J. Econ. Entomol. 52:455-457 (1959JI
Heath, R. G.: Preliminary report of mirex studies on avian reproduction.
Report submitted to Advisory Committee. 3 pp (1971).
Hensley, S. D., Long, W. H., Roddy, L. R., McCormick, W. J., and Concienne,
E. J.: Effects of insecticides on the predaceous arthropod fauna of
Louisiana sugarcane fields. J. Econ. Entomol. 54:146-149 (1961)
Innes, J. R. M., Ulland, B. M., Valerio, M. G., Petrucelli, L., Fishbein, L.,
Hart, E. R., Pallotta, A. J., Bates, P. R., Falk, H. L., Gart, J. J.,
Klein, M., Mitchell, I., and Peters, J.: Bioassay of pesticides and
industrial chemicals for tumorigenicity in mice: A preliminary note.
J. Nat. Cancer Inst. 42:1101-1114 (1969).
Keh, B., Brownfield, N. T., and Person, M. E.: Experimental use of bait
with mirex lethal to both adult and immature Vespula pennsylvanica
(Hymenoptera: Vespidae). Calif. Vector Views 15:115-118 (1968).
Larson, P. S.: Toxicologic studies on the effects of adding mirex to the
diet of albino rats for a period of three months. Unpubl. Rept. furnished
to Mirex Advisory Committee December 21, 1971, 12 pp (1968).
Lavigne, R. J.: Individual mound treatment for control of the western
harvester ant Pogonomyrmex occidental is in Wyoming. J. Econ. Entomol.
59:525-532 (1966T
Lofgren, C. S., Adler, V. E., and Barthel, W. F.: Effects of some variations
in formulation or application procedure on control of the imported fire ant
with granular heptachlor. J. Econ. Entomol. 54:45-47 (1961).
Lofgren, C. S., Adler, V. E., Banks, W. A., and Pierce, N.: Control of
imported fire ants with chlordane. J. Econ. Entomol. 57:331-333 (1964).
Lofgren, C. S., Banks, W. A., Glancey, B. M., and Weidhaas, D. E.: Interim
report on imported fire ant trials. Submitted December 1971 to Mirex
Advisory Committee (1970).
Lowe, J. I., Parrish, P. R., Wilson, A. J., Jr., Wilson, P. D., and Duke,
T. W.: Effects of mirex on selected estuarine organisms. Unpubl. MS
25pp (1971).
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Ludke, J. L., Finley, M. T., and Lusk, L.: Toxicity of mirex to crayfish,
Procambarus blandingi. Bull. Environm. Contam. Toxicol. 6:89-96 (1971).
Mahood, R. K., McKenzie, M. D., Middaugh, D. P., Bollar, S. J., Davis,'J. R.
and Spitsbergen, D.: A report on the cooperative blue crab study. South
Atlantic States. USD I 32pp (1970).
Markin, G. P.: Affidavit of George P. Markin No. 1. Filed November 6,
1970, in U.S. District Court for District of Columbia. Civil No. 2319-70
63pp (1970).
Markin, G. P.: Methods of controlling the imported fire ant. Special Rept.
USDA, PPD, Gulfport, Miss. 8pp (1971 a).
Markin, G. P.: Residues of the insecticide mirex following treatment of
Cat Island. Unpubl. MS 13pp (1971b).
Markin, G. P., Ford, J. H., Hawthorne, J. C., Spence, J. H., Davis, J., and
Loftis, C. D.: Environmental monitoring for the insecticide mirex. MS to
be submitted to Pest. Monit. J. (1971a).
Markin, G. P., Ford, J. H., and Hawthorne, J. C.: Mirex residues in wild
populations of the edible red crayfish (Procambarus clarkii). MS to be
submitted to Bull. Environm. Contam. Toxicol. 15 pp (1971b).
Markin, G. P., Hawthorne, J. C., Collins, H. L., and Ford, J. H.: Levels
of mirex and some other organochlorine residues in seafood from Atlantic
and Gulf Coast States. MS to be submitted to Pest. Monit. J. 28pp (1971c),
Martin, W. E.: Communication to Mirex Advisory Committee dated
November 23, 1971.
Matthews, H. B.: Mirex studies at NIEHS. Presented to Mirex Advisory
Committee November 18, 1971. 8pp (1971).
Maxwell, F. G., Project Coordinator: Levels of chlorinated hydrocarbons in
catfish in Alabama, Arkansas, Florida, Georgia, Louisiana, and Mississippi
Final Rept.-Draft. Miss. State University 61pp (1971).
McKenzie, M. D.: Fluctuations in abundance of the blue crab and factors
affecting mortalities. S.C. Wildlife Resources Dept. Tech. Rept. 1
45pp (1970).
Miller, D. C.: The feeding mechanism of fiddler crabs, with ecological
considerations of feeding adaptations. Zoologica 46:89-100 (1961).
Mills, H. B., Chairman: Report of committee on the imported fire ant
to Administrator, Agricultural Research Service, U.S. Department of
Agriculture Sept. 28, 1967. National Academy of Sciences, National
Research Counci1. 15pp (1967).
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Muncy, R. J. and Oliver, A. D., Jr.: Toxicity of ten insecticides to
the red crayfish, Procambarus clarki (Girard). Trans. Amer. Fish. Soc.
92(4):428-431 (1963).
Naber, E. C. and Ware, G. W.: Effect of kepone and mirex on reproductive
performance in the laying hen. Poultry Sci. 44:875-880 (1965).
Odum, W. E., Woodwell, G. M., and Wurster, C. F.: DDT residues absorbed
from organic detritus by fiddler crabs. Science 164:576-577 (1969).
Parrish, H. M.: Analysis of 460 fatalities from venomous animals in
the United States. Amer. J. Med. Sci. 245:129-141 (1963).
Race, S. R.: Control of western harvester ants on rangeland. N. Mex.
State Univ. Agr. Exp. Sta. Bull. 502 21pp (1966).
Smith, J. B.: Testimony of Pineapple Growers Association of Hawaii
before Mirex Advisory Commission. Given before the Mirex Advisory
Committee November 17, 1971. llpp plus 5pp Attachm. (1971).
Tagatz, M. E.: Biology of the blue crab, Callinectes sapidus Rathbun.
in the St. Johns River, Florida. Fish. Bull. 67:17-33 (1968).
Triplett, R. F.: Statement presented to the Mirex Advisory Committee on
October 28, 1971. 17pp (1971).
Tucker, R. K. and Crabtree, D. G.: Handbook of Toxicity of Pesticides to
Wildlife. USDI Resource Publ. No. 84 131pp (1970).
U. S. Department of Agriculture: A plan for a pilot study to monitor mirex
residues in terrestrial, amphibious, and aquatic organisms in the Dublin,
Georgia, treatment area. 17pp (1971 a).
U. S. Department of Agriculture: Feeding study to determine mirex residues
in milk of dairy cows that may accumulate over time. 2pp; Mirex residues
in milk from cows fed the insecticide in daily rations. Ip (1971b).
U. S. Department of Agriculture: USDA Statement on the imported fire ant
and its control. 69pp (1971c).
U. S. Department of Agriculture, APHS: Work Accomplishment Summary —
Imported Fire Ant. Unpubl. (Dedember 1971d).
U. S. Department of Interior: Mirex residues in birds and raccoons of
South Carolina estuaries. Special Rept. Pesticide Field Appraisal.
35pp (1971).
Van Valin, C. C., Andrews, E. K., and Eller, L. L.: Some effects of mirex
on two warm-water fishes. Trans. Amer. Fish. Soc. 97:185-196 (1968).
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Ware, G. W. and Good, E. E.: Effects of insecticides on reproduction in
the laboratory mouse. II. Mirex, Telodrin, and DDT. Toxicol. Appl.
Pharmacol. 10:54-61 (1967).
Wilson, E. 0.: Variation and adaptation in the imported fire ant.
Evolution 5:68-79 (1951).
Wilson, E. 0.: Affidavit on the impact of mirex on the environment.
2pp (1971).
Wilson, E. 0. and Eads, J. H.: A report on the imported fire ant
Solenopsis saevissima var. richteri Forel in Alabama. Ala. Dept.
Conserv. Special Rept. 53pp (1949).
Wilson, N. L.: Effects of mirex bait on some nontarget arthropod popu-
lations. Six Months Progress Rept. Imported Fire Ant Lab., USDA,
ARS, PPD, Gulfport, Miss. 14pp (1971).
Wilson, N. L. and Oliver, A. D.: Food habits of the imported fire ant
in pasture and pine forest areas in southeastern Lousiana. J. Econ.
Entomol. 62:1268-1271 (1969).
Yobs, A. R.: Report to the Mirex Advisory Committee. Presented to
the Mirex Advisory Committee November 18, 1971. Ip (1971).
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PERSONS APPEARING BEFORE THE COMMITTEE
First Meeting
October 27 & 28, 1971
Mr. Harold G. Alford, Pesticides Regulation Division, Environmental
Protection Agency
Dr. W. G. Eden, University of Florida
Mr- Leo G. K. Iverson, Animal and Plant Health Service, U. S. Department
of Agriculture
Dr. William A. Knapp, Allied Chemical Corporation
Mr. Donald J. Mulvihill, Attorney for Allied Chemical Corporation
Mr. George A. Robertson, Office of General Counsel, Environmental
Protection Agency
Dr. R. Faser Triplett, Mississippi Allergy Clinic, Jackson, Mississippi
Dr. Robert J. Weir, Bionetics Research Labs., Inc.
Second Meeting
November 17 & 18, 1971
Dr. Karl Baetcke, Mississippi State University
Dr. R. R. Bates, National Cancer Institute, National Institutes of
Health
Mr. J. Phil Campbell, Under Secretary, U. S. Department of Agriculture
Dr. Thomas W. Duke, Gulf Breeze Marine Laboratory, Environmental
Protection Agency
Dr. 0. Garth Fitzhugh, Office of Pesticides Programs, Environmental
Protection Agency
Mr. James 0. Lee, Jr., Animal and Plant Health Service, U. S. Department
of Agriculture
Dr. Robert J. Livingston, Florida State University
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Dr. George P. Markin, Animal and Plant Health Service, U. S.
Department of Agriculture, Gulfport, Mississippi
Mr. William E. Martin, Fish and Wildlife Service, U. S. Department
of the Interior
Dr. H. B. Matthews, National Institutes of Environmental Health
Services
Dr. F. J. Mulhern, Animal and Plant Health Service, U. S. Department
of Agriculture
Mr. M. T. Pender, Animal and Plant Health Service, U. S. Department
of Agriculture
Mr. D. R. Shepherd, Animal and Plant Health Service, U. S. Department
of Agriculture
Dr. James Smith, Pineapple Growers Association of Hawaii
Dr. D. Weidhaas, Entomology Research Division, U. S. Department of
Agriculture, Gainesville, Florida
Dr. Anne Yobs, Division of Community Studies, Environmental Protection
Agency
Third Meeting
December 21 & 22, 1971
Mr. Roy Bailey, Allied Chemical Corporation
Dr. Frederick Coulston, Albany Medical College of Union University
Dr. William A. Knapp, Allied Chemical Corporation
Mr. Donald J. Mulvihill, Attorney for Allied Chemical Corporation
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