SUBSTITUTE CHEMICAL PROGRAM
INITIAL SCIENTIFIC
MINIECONOMIC REVIEW
MARCH 1975
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDE PROGRAMS
CRITERIA AND EVALUATION DIVISION
WASHINGTON, D.C. 20460
EPA-540/1-75-006
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This report has been compiled by the Criteria
and Evaluation Division, Office of Pesticide
Programs, EPA in conjunction with other sources
listed in the Preface. Contents do not
necessarily reflect the views and policies of
the Environmental Protection Agency, nor does
mention of trade names or commercial products
constitute endorsement or recommendation for
use.
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PREFACE
The Alternative (Substitute) Chemicals Program was initiated under
Public Law 93-135 of October 24, 1973, to "provide research and testing
of substitute chemicals." The legislative intent is to prevent using
substitutes, which in essence are more deleterious to man and his environ-
ment, than a problem pesticide (one that has been suspended, cancelled,
deregistered or in an "internal review" for suspected "unreasonable
adverse effects to man or his environment"). The major objective of the
program is to determine the suitability of substitute chemicals which now
or in the future may act as replacements for those uses (major and minor)
of pesticides that have been cancelled, suspended, or are in litigation
or under internal review for potential unreasonable adverse effects on
man and his environment.
The substitute chemical is reviewed for suitability considering all
applicable scientific factors such as: chemistry, toxicology, pharma-
cology and environmental fate and movement; and socio-economic factors
such as: use patterns and costs and benefits. EPA recognizes the fact
that even though a compound is registered it still may not be a practical
substitute for a particular use or uses of a problem pesticide. The -
utilitarian value of the "substitute" must be evaluated by reviewing its
biological and economic data. The reviews of substitute chemicals are
carried out in two phases. Phase I conducts these reviews based on data
bases readily accessible at the present time. An Initial Scientific
Review and Minieconomic Review are conducted simultaneously to determine
if there is enough data to make a judgment with respect to the "safety
and efficacy" of the substitute chemical. Phase II is only performed if
the Phase I reviews identify certain questions of safety or lack of benefits.
The Phase II reviews conduct in-depth studies of these questions of safety
and cost/benefits and consider both present and projected future uses of
the substitute chemicals.
The report summarizes rather than interprets scientific data reviewed
during the course of the studies. Data is not correlated from different
sources. Opinions are not given on contradictory findings.
This report contains the Phase I Initial Scientific and Minieconomic
Review of Bromacil (5-bromo-3-sec-butyl-6-methyluracil). Bromacil was
identified as a registered substitute chemical for certain cancelled and
suspended uses of 2,4,5-T. Where applicable, the review also identifies
areas where technical data may be lacking so that appropriate studies may
be initiated to develop desirable information.
The review covers all uses of bromacil and is intended to be adaptable
to future needs. Should bromacil be identified as a substitute for a problem
pesticide other than 2,4,5-T, the review can be updated and made readily
available for use. The data contained in this report was not intended to be
iii
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complete In all areas. Data-searches ended in December, 1974. The review
was coordinated by a team of EPA scientists in the Criteria and Evaluation
Division of the Office of Pesticide Programs. The responsibility of the team
leader was to provide guidance and direction and technically review information
retrieved during the course of the study. The following EPA scientists were
members of the review team: Fumihiko Hayashi, Ph.D. (Team Leader); Carroll
Collier (Chemistry); William Burnam (Pharmacology and Toxicology); John Bowser
(Fate and Significance in the Environment); John Leitzke (Fate and Significance
in the Environment); Richard Petrie (Registered Uses); Jeff Conopask (Economics),
Data research, abstracting and collection were primarily performed by
Midwest Research Institute, Kansas City, Missouri (EPA Contract #68-01-2448).
RvR Consultants, Shawnee Mission, Kansas, under a subcontract to Midwest
Research, assisted in data collection. E. I. du Pont de Nemours and Company,
a manufacturer of bromacil, made certain comments and additions to this report.
iv
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GENERAL CONTENTS
Page
List of Figures vi
List of Tables vii
Fart I. Summary 1
Part II. Initial Scientific Review 10
Subpart A. Chemistry 10
Subpart B. Pharmacology and Toxicology 25
Subpart C. Fate and Significance in the Environment . . 39
Subpart D. Production and Use 55
Part III. Minieconomic Review 70
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FIGURES
No. Page
1 Production Schematic for Bromacil ..... . 13
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TABLES
No. Page
1 Weight Losses on Combustion of a Commercial Bromacll
Formulation (percent) 20
2 Consumption of Bromacll 27
3 Mortality of Rats Consuming Bromacll 28
4 Results of Multiple Oral Dosing of Bromacll In Cattle,
Sheep, and Chickens 31
5 Bromacil 80Z Wettable Powder (Hyvar^X) Label 58
6 Estimated Uses of Bromacll In the U.S. by Regions and
Categories, 1972 64
7 Bromacll Uses in California by Major Crops and Other
Uses, 1970-1973 66
8 Use of Bromacil in California in 1972 by Crops and Other
Uses, Applications, Quantities, and Acres Treated ... 68
9 Use of Bromacil in California in 1973 by Crops and Other
Uses, Applications, Quantities, and Acres Treated ... 69
vii
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PART I. SUMMARY
CONTENTS
Production and Use
Toxicity and Physiological Effects . . .
Food Tolerances and Acceptable Intake .
Environmental Effects
Limitations in Available Scientific Data
Efficacy and Cost Effectiveness ....
Faze
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This section contains a brief summary of the "Initial Scientific
and Minieconomic Review" on bromacil. The section summarizes rather
than intreprets data reviewed.
Production and Use
Bromacil (5-bromo-3-sec-butyl-6-methyluracil) is one of a family
of substituted uracils used as herbicides. Three reactions are required
for its manufacture:
see-but ylamine
COC12
phosgene
2HC1
sec-butylurea (I)
(I) + CH,COCH9C09C9H«
j / / ^ :
ethyl acetoacetate
H20
ethanol
sec-C
Br2
3-sec-butyl-6-methyluracil (II)
HBr
Bromacil
The only domestic manufacturer of bromacil and other substituted
uracils is E. I. du Pont de Nemours and Company, Inc. Their produc-
tion facility, which is located in La Porte, Texas, has an estimated
capacity of 20 million pounds per year of total uracils.
The chemistry of bromacil reported in available literature primarily
concerns degradation reactions. Bromacil is reported to be slowly de-
composed in strong acid, but is stable in water, aqueous base, common
organic solvents, and at temperatures up to its melting point (158 to
159° C). Degradation by ultraviolet radiation has also been reported.
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Bromacil is a broad-spectrum herbicide used for control of annual
and perennial grasses and broadleaf weeds, for nonselective weed and
brush control on noncropland, and for selective weed control on a limited
number of crops. Bromacil is commercially available in formulation as
a single active ingredient, and in combination with diuron, sodium meta-
borate, and sodium chlorate.
An estimated 3 million pounds of bromacil active ingredient (AI)
were used domestically in 1972. Of that quantity, about 400,000 Ib AI
were used for agricultural purposes (primarily for weed control in citrus
groves located in the Southwestern states, and in pineapple fields in
Hawaii); 2,300,000 Ib AI were used by industrial and commercial organi-
zations; and about 300,000 Ib AI by government agencies. Bromacil is
not registered for home and garden use.
Estimated 1972 regional uses of bromacil are: South Central states—
about 25%, Southwestern states—about 20%, Southeastern states—about
20%, North Central states—13%, and the Northeastern and Northwestern
states—less than 10% each.
Toxicity and Physiological Effects
No data was found on effects of bromacil on humans, either on an
acute basis or under field conditions or in the manufacturing processes.
Bromacil, however, is not a highly toxic compound. The spectrum of its
toxicity as evaluated in rats is as follows:
Acute oral toxicity - LD5Q = 5,200 mg/kg.
Acute inhalation toxicity - No deaths occurred after 4 hr in a 4.8 mg/liter
environment.
Subacute oral toxicity (10-day study) - No deaths occurred after 10 daily
doses of 650 mg/kg, and five out of six animals survived 10 daily doses
of 1,035 mg/kg. In contrast, four out of five animals died after five
doses of 1,500 mg/kg. At both the 650 and 1,035 mg/kg doses, pathological
changes were observed in the liver immediately after the final (10th) dose.
No pathological changes were observed in the livers, after a 14-day
recovery period.
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Chronic oral toxicitv (2-year study) - Female rats on the highest dose
level tested (1,250 ppm) suffered weight retardation during first and
second years. There were no clinical signs of toxicity. No unusual
alterations were observed during hematological, urinalysis, and clinical
chemistry evaluations. There were no gross pathological lesions. There
appeared to be a dose-related effect on the thyroid. Slight hyperplasia
of the thyroid was noted at the highest dose level.
An acute oral toxicity evaluation could not be obtained in dogs
because of ernes is. Five grains per kilogram, as a single dose or as
divided doses, produced excessive ernesis. Emesis was still observed at
the 200 to 250 mg/kg level. Signs of toxicity in dogs were salivation,
weakness, loss of coordination, excitability, diarrhea and nydriosis.
In long term studies with rats, bromacil did not appear to accumulate
in tissues.
In a 2-year chronic oral toxicity test, groups of dogs were
maintained on 0.005, 0.025, and 0.125% bromacil in the diet. Only one
death occurred, and that dog was on the 0.005% diet; the cause of death
was not associated with the compound. A loss in weight was noted at the
high dose at the beginning of the experiment.
Bromacil is moderately toxic to ruminants. Cattle suffered weight
loss and were poisoned with a single dose at 250 mg/kg. Sheep were also
poisoned and had a weight loss after three 250 mg/kg doses of bromacil
were given by drench or capsule; a dose (drench) of 100 mg/kg also caused
poisoning and weight loss. None of the ruminants died.
In ±a vitro tests, bromacil reduced the amount of dry matter digested
by rumen bacteria. Bromacil did not effect volatile fatty acid production.
A decrease in the number of ciliated protozoa in rumen fluid in the
presence of bromacil was noted.
Chickens appear to tolerate a dose of 500 mg/kg. There was a sig-
nificant reduction in weight gain at this level.
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The effect of bromacil on the reproduction of rats was evaluated
in a three-generation study. Addition of 0.025% bromacil to the diet
did not markedly effect the reproductive performance; no deformed
young were produced.
Very little information exists as to the site of bromacil metabo-
lism, distribution or retention, the enzymes involved, and the cofactor
requirements.
Bromacil is metabolized and excreted as six metabolites by rats,
one being 5-bromo-3-8ec-butyl-6-hydroxymethyluracil. In cases of
human industrial exposure, bromacil and its primary metabolite, 5-bromo-
3-sec-butyl-6-hydroxymethyluracil was detected in urine.
No gross manifestations of teratogenic effects were observed in
the fetuses of pregnant rabbits consuming as much as 250 ppm from the
eighth day of pregnancy to the 16th day.
There is no Indication from the literature review that bromacil
produces oncogenic effects.
Food Tolerances and Acceptable Intake
Bromacil has not been reported as a significant residue in any
class of food, but is not necessarily detected by the analytical system
routinely used to monitor pesticide residues in food.
Tolerances have been established for bromacil on only two crops
in the United States, citrus fruits and pineapples. Both tolerances
have been set at 0.1 ppm.
An acceptable daily intake (ADI) has not been established for
bromacil. An ADI has not been considered by the Food and Agricultural
Organization/World Health Organization (FAO/WHO).
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Environmental Effects
Brotnacil displayed a low order of toxicity to six fish species
as well as tadpole, crawfish and waterflea. The eight-day dietary
LCso for both the mallard duck and the bobwhite quail was? 10,000 ppm.
Bromacil was tested as a spray at 10,000 ppm against housefly, roach
aphid (systemic) and mite and was found to be totally lacking in
insecticidal or acaricidal activity.
Stains of Euglena. an aquatic algae, were not affected by 40 ppm
bromacil, and were only partially Inhibited by 100 ppm. One wild strain
of Euglena. however, was markedly inhibited by 2 ppm and completely
inhibited by 10 ppm (none of the strains were affected by bromacil in
the dark).
A number of soil fungi have shown uninhibited growth with bromacil.
Ten soil fungi (Aspergillus tamarii, A. niger. A. flavus. A. oryzae.
Curvularla lunata. Mucor pusillus. Trichoderma vlride. Penicillium
funiculosum. £. brevicompactum. and Myrothecium verucaria) were cultured
on liquid broth media with bromacil levels from 250 to 5,000 ppm for
5 days. Bromacil, up to 2,000 ppm did not inhibit the growth of the
fungi; except A. niger. which was inhibited by bromacil levels less than
1,500 ppm.
No statistically significant differences were found in the ammonium
and nitrate nitrogen contents of, nor in the amounts of carbon dioxide
evolved from untreated sandy loam and that from loam treated with 4 ppm
bromacil (twice the application rate recommended for this type of soil).
The available data indicates that certain soil microorganisms are
capable of degrading bromacil, and that normal bromacil concentrations
in the soil, i.e., those that might be expected from its use in accord-
ance with label directions, do not appear to adversely affect the soil
microflora.
Available data indicates that bromacil is not strongly adsorbed on
soil colloids.
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Bromacil residues In the soil appear to be quite persistent. In
one test, the half-life of a A Ib Al/acre application to the surface of
& Butlertown silt loam was found to be about 5 to 6 months. At higher
application rates, the herbicidal activity of brotnacil seemed to persist
for two or more seasons.
Other investigations involving the application of 1 and 4 Ib of
bromacil per acre to six California locations found bromacil to be
persistent. One year after application (for both application rates)
plots remained toxic to barley, milo, sugar beets, alfalfa, tomatoes,
and wheat.
In vitro studies show that some microorganisms have the ability
to metabolize bromacil. The solubility of bromacil in water could be
resulting rainfall being a factor in soil persistence.
Regarding bromacil residues in air, one study showed that the rate
of bromacil volatilization in an air circulation oven maintained at 120°F
was less than 0.1%/week. Other studies indicated that bromacil is very
stable to phctodecomposition.
Limitations in Available Scientific Data
The review of scientific literature was based on available sources
given limitations of time and resources. Data was not found in a
number of pertinent areas.
1. The effect of bromacil on humans.
2. Intraperitoneal and intravenous 11*50 values on at least one
species.
3. Inhalation data on more species than the rat.
4. A long-term (2 years) study in rats at a dose level higher
than 0.125%.
5. Data related to behavioral effects and the effects on tissue
culture growth and viability.
6. Field data on effects on fish.
7. Field data on effects of wildlife.
8. Additional data on the effects on the soil microflora and on
effects on soil microfauna.
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9. Data from national or regional soil monitoring studies on
pesticide residues.
10. Laboratory or field data on effects on lower aquatic organisms.
11. Additional information on the presence, fate, and persistence
of bromacil residues in water, sediment, or other elements of
the aquatic ecosystem.
12. Additional data on the presence, fate, or persistence of
bromacil residues in air.
13. Data on the possible bioaccumulation or biomagnification of
bromacil.
14. Specific data on the environmental transport mechanisms of
bromacil.
Bromacil is used primarily as a nonselective industrial herbicide
on noncropland, and limitations in environmental data should be evaluated
in terms of this use pattern.
Efficacy and Cost Effectiveness
Bromacil is used as a broad-spectrum herbicide to control annual
and perennial grasses and brush in pineapple and citrus orchards, along
railroads and highway right-of-ways, around utility poles, and along
drainage ditches, canals and fences.
Bromacil has effectively controlled Bermuda grass, Vasey grass,
nutsedge, crabgrass, Bahia grass and sweetgrass. It also controls willow,
cottonwood, water locust, post oak, blackjack oak, hickory, maple, wild
cherry, sweet gum, elm and a wide variety of other brush.
The economic benefit from using bromacil on oranges was determined
from one experiment in Florida. At a rate of 3.5 Ib/acre, the economic
benefit amounted to $27.25/acre from the increased yield of oranges (based
on 1972 cost data). No other economic benefit data was found.
Economic benefits from noncrop applications (e.g., grass and brush
control along highways, utility lines, and railroads) are best measured
by an alternative costing method. Alternative methods to chemical con-
trol include mechanical control such as mowing, discing, bulldozing and
the use of brush cutting machines. Hand labor is often required for
mowing around trees, poles and other objects and for weeding or cutting
brush. In some cases burning for control of grasses along canal banks
is an alternative.
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The true economic benefits cannot be measured because much of the
noncrop weed control is for aesthetic reasons such as beautification of
highways. It is also a form of preventative maintenance to keep fires
from causing damage when grasses are dry. Therefore, the cost of the
chemical control should be subtracted from the alternative control cost,
such as hand labor or mechanical control, to determine the economic
benefit from the use of bromacil.
Selected tests comparing the use of chemical treatment to alterna-
tive methods such as mechanical or hand labor control for noncrop weed
and brush removal showed economic benefits ranging from a decreased cost
of $6.50/acre for chemical control of weeds and brush along irrigation
ditches in California, to a $175.00/acre cost reduction for treatment of
flood control dikes in West Springfield, Massachusetts. However, a more
accurate assessment of economic benefits would require cost data over at
least a 3-year period because initial costs of chemical treatment are
much higher than subsequent chemical treatment costs.
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PART II. INITIAL SCIENTIFIC REVIEW
SUBPART A. CHEMISTRY
CONTENTS
Page
Synthesis and Production Technology 11
Physical Properties of Bromacil 12
Analytical Methods. 14
Composition and Formulation 17
Chemical Properties, Degradation and Decomposition Processes. . . 17
Photochemical Decomposition 18
Degradation in Soil 19
Thermal Decomposition 19
Other Decomposition Processes 21
Occurrence of Bromacil Residues in Food and Feed Commodities. . . 21
Acceptable Daily Intake 21
Tolerances 22
References 23
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This section reviews available data on bromacil's chemistry and presence
in foods. Eight subject areas have been examined: Synthesis and Production
Technology; Physical Properties of Bromacil; Composition and Formulation;
Chemical Properties, Degradation and Decomposition Processes; Occurrence and
Residues in Food and Feed Commodities; Acceptable Daily Intake; and Tolerances.
The section summarizes rather than interprets scientific data reviewed.
Synthesis and Production Technology
Bromacil is one of a. family of substituted uracils used as herbi-
cides. The production steps are similar for all members of the family,
the differences being primarily in the starting materials. The chemical
synthesis of bromacil is as follows (von Rumker et al., 1974)I/:
COC12 + NH3 > C4HgNHCONH2 + 2HC1 (1)
sec-butylamine phosgene ammonia sec-butylurea
'sec-C^ j}^ , (2)
H20 + C2H5OH
sec-butylurea ethyl acetoacetate
r* •• "r»«^ ^TT
ethanol
3-sec-butyl-6-methyluracil
3-sec-butvl-6-methyluracil Bromacil
I/ von Rumker, R., E. W. Lawless, and A. F. Meiners, "Production, Dis-
tribution, Use and Environmental Impact Potential of Selected
Pesticides," Final Report, Contract No. EQC-311, for Council on
Environmental Quality, Washington, D.C. (1974).
11
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E. I. du Pont de Nemours and Company is the only manufacturer of
bromacil. The manufacturing plant is located in La Porte, Texas and
has an estimated total capacity of 20 million pounds per year for all
substituted uracils.
A proposed schematic for bromacil production is shown in Figure 1.
A series of substituted uracils is covered by U.S. Patent No.
3,235,357 (Loux, 1966)!/, but this is primarily a use patent and the
method suggested for preparing bromacil is a laboratory method.
The preparation of bromacil is described as follows:
"A solution of 182 parts of 3-sec-buty1-6-methyluracil in
700 parts of acetic acid containing 82 parts of sodium acetate
was treated with 160 parts of bromine. After standing over-
night, the mixture, which contained some solid, was evaporated
to a solid under reduced pressure. The solid was recrystallized
from an ethanol-water mixture to give, as a white crystalline
solid, 2-sec-butyl-5-br6mo-6-methyluracil melting at 157.5 to
160°C."
Physical Properties of Bromacil
Chemical name: 5-bromo-3-sec-butyl-6-methvluracil
Common name: Bromacil
Trade name: Hyvar® X
Pesticide class: Herbicide; substituted uracil
Structural formula: H
u
Br-C. N-CH-CH2-CH3
I **
Empirical formula: CgHj^Br^C^
I/ Loux, H. M. (to E. 1. du Pont de Nemours and Company, Inc.), U.S.
Patent No. 3,235,357 (February 15, 1966).
12
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f—
Sec - Butylamine—^
M I"M i th
I
Urea Unit
I
Purification
~ ~l
1
1
1
|
1
J
th. IMiif"!
Sec-C4H9NHCONH2
1
Ethyl ^
Acetoacetate
Ki..r^ii 1^.
Uracil Unit
\
Purification
Aqueous
Waste
Na Salt of
3 -Butyl ,6- Methyl Uracil
I
i
H^SO'j » Neutralization _ Ku««n. ^
«2:)U4 + Separation
Bromine ^
H^O ih.
NaOH
Stream
j
Bromacil
Unit
Source: von Rlimker et al.f op
^^ Filtrqtion
Drying
i >
1
Bromacil
. cit. (1974).
Biological
Treatment
r
^ Disposal
at Sea
NaBr
Stream
•Discharge
Figure 1. Production schematic for bromacil.
13
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Molecular weight: 261.1
Analysis: C - 41.37%; H - 5.02%; Br - 30.61%; N - 10.73%; 0 - 12.26%
Physical state: White, odorless, crystalline solid
Melting point: 158-159°C
Vapor pressure: 8 x 10~4 mm Hg at 100°C
Stability: Temperature stable up to melting point, but slowly sublimes
at temperatures just below melting point.
Specific gravity: 1.55 25/25°C
Solubility at 25°C: Solvent g/100 ml
Absolute ethanol 13.4
Acetone 16.7
Acetonitrile 7.1
Sodium hydroxide
(3% aqueous) 8.8
Water 0.0815 (= 815 ppm)
Xylene 3.2
Analytical Methods
This subsection reviews analytical methods for bromacil. The review
describes multi-residue methods, residue analysis principles, and formula-
tion analysis principles. Information on the sensitivity and selectivity
of these methods is also presented.
Multi-Residue Methods - Multi-residue methods for detecting bromacil are not
found in either the Association of Official Analytical Chemists methods
manuall/ or the Pesticide Analytical Manual. Volume I (PAM 1971).?J Bromacil
has not been reported as a significant residue in any class of food nor is it
routinely searched for in the FDA multi-residue analytical system which is
used to monitor pesticide residues in food. Adequate individual compound
methods exist for measuring bromacil residues. The apparent reason for the
absence of bromacil residue data is that the pesticide is not widely used on
food and feed items. The absence of bromacil residue data does not mean that
it could not be present in food.
I/ Association of Official Analytical Chemists, Official Methods of Analysis
of the Association of Official Analytical Chemists, llth ed., Washington,
D.C. (1970).
21 U.S. Department of Health, Education and Welfare, Food and Drug
Administration, Pesticide Analytical Manual, Vol. I (1971).
14
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Residue Analysis Principles - Volume II of the Pesticide Analytical Manual
(PAM, 1971)i/ lists two methods of residue analysis for bromacil. The first
is the method described by Pease (1966).I/ This method can be used for soil,
fruits, vegetables, animal tissue, grain and seed. The sample is first
extracted with sodium hydroxide; the extract is acidified with sulfuric acid,
and the bromacil is then extracted into chloroform. The chloroform portion is
separated and the solvent is evaporated. The residue is redissolved in aqueous
sodium hydroxide, acidified, and the bromacil is reextracted into ethyl acetate.
The solvent is again evaporated and the residue is finally dissolved in nitrq-
methane. The final determination is made using gas chromatography and a micro-
coulometric detector. The recoveries are greater than 85%, and the sensitivity
is about 0.04 ppm.
The second PAM method is described in Jolliffe et al. (1967)!/. The
method employs a relatively short (13 in.) gas chromatography column and
an electron-capture detector. The authors claim the method is simple and
fast, but maintains sensitivity and reproducibility. The procedure for
the analysis of soils is slightly different from that for leaves or fruit.
For both procedures, the initial extraction is performed with an aqueous
solution of ammonium sulfate and sodium hydroxide. In soil analysis, the
recoveries are 90 to 110%, and sensitivity is about 0.01 ppm. For leaves
or fruit, the method is not as accurate; recovery is about 60 to 85%, and
sensitivity is 0.1 ppm.
Zweig and Sherma (1972)A/ discuss two additional methods. One is
described by Bevenue and Ogata (1970).!.' This method uses gas chromatog-
raphy with an electron-capture detector and is applicable to plant material,
soil and water. Sample preparations are similar to those used by Pease (1966)
and Jolliffe et al. (1967). The method differs from that of Pease (1966)—a
microcoulometric titrating system is not needed. The method also differs from
that of Jolliffe et al. (1967)—a short gas chromatograph is not used.
Recoveries of bromacil were 85 to 89%, and the limits of detectability were
0.005 ppm. The second method is that of Gutenmann and Lisk (1968) .6/ Their
method for bromacil was tested only on residues in soil. The residue was
extracted directly into ethyl acetate. The herbicide was then isolated by
evaporative co-distillation. Electron affinity detection was employed in the
gas chromatographic procedure. Recoveries of bromacil in the 0.04 to 0.4 ppm
range ranged from 72 to 90%.
I/ U.S. Department of Health, Education and Welfare, Food and Drug
Administration, Pesticide Analytical Manual. Vol. II (1971).
2J Pease, H. L., "Determination of Bromacil Residues," J. Agr. Food Chem.,
14(l):94-96 (1966).
.37 Jolliffe, V. A., B. D. Day, L. S. Jordan, and J. D. Mann, "Method of
Determining Bromacil in Soils and Plant Tissues, "J. Agr. Food Chem..
15(l):174-77 (1967).
kj Zweig, G. and J. Sherma, Analytical Methods for Pesticides and Plant
Growth Regulators. Vol. VI; Gas Chromatographic Analysis, p. 603,
Academic Press, New York, New York (1972).
5_/ Bevenue, A. and J. N. Ogata, "Determination of Bromacil by Gas Chroma-
tography ," J_i_J]hromatog>., 46(1): 110-11 (January 1970).
6J Gutenmann, W. H. and D. J. Lisk, "Estimation of Residues of Uracil
Herbicides by Gas Chromatograjphy After Evaporative Co-Distillation,"
J. Assoc. Offie. Anal. Chem.. 51(3):688-90 (1968).
15
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Formulation Analysis Principles - Pease and Deye (1967)—/ explain the basis
for formulation analysis as follows:
"Bromacil exhibits the properties of a weak acid. It forms water-
soluble alkali salts and can be extracted from aqueous acid into nonpolar
organic solvents. The material can thus be separated, purified, and con-
centrated by appropriate extraction techniques.
"The isolated material is most accurately determined by a differential
infrared analysis at 13.02 pm, the absorption maximum arising from the
uracil configuration of the molecule. Bromacil is too weakly acidic for
titration in water, but can conveniently and easily be assayed with good
precision by nonaqueous titration.
"Ultraviolet analysis of the extracted material is impractical because
of interferences. Gas chromatographic methods are accurate but generally
lack the precision of the differential infrared and nonaqueous titration
methods."
Pease and Deye (1967) then explain the principle of the differential
infrared method:
"The active ingredient, 5-bromo-3-sec-butyl-6-methyluracil. is isolated
by extraction with ethyl ether and is determined by differential infrared
analysis. In the differential infrared method, a solution of known concen-
tration of pure bromacil is placed in the reference beam of the infrared
spectrophotometer, and its absorbance is compared with that of a solution
of the unknown placed in the sample beam. To assure maximal precision,
the solution is scanned three times at slow speed and high gain, and the
average absorbance reading is used."
The standard deviation of this method is approximately 1% in the 40
to 60% concentration of bromacil range, provided there are no extractable
ingredients that absorb at the analytical wavelengths.
The principle of the nonaqueous titration method is explained by Pease
and Deye (1967):
"The active ingredient, 5-bromo-3-sec_-butyl-6-methyluracil, after
isolation from possible interfering formulating ingredients, is dissolved
in acetone and titrated with tetrabutylammonium hydroxide. The titration
is followed potentiometrically with a high impedance pH meter using a
glass-modified calomel electrode system."
The precision of this method is i 0.3%. Other weakly acidic materials
may interfere.
I/ Pease H. L. and J. F. Deye, "Bromacil," Analytical Methods for Pesti-
cide. Plant Growth Regulators, and Food Additives. Vol. V; Additional
Principles and Methods of Analysis, G. Zweig (ed.), Academic Press,
New York (1967).
16
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Composition and Formulation
Bromacil is available in five formulations from the manufacturer:
1. Hyvarfe/X bromacil weed killer, a wettable powder containing
80% bromacil.
2. HyvarOPx-L bromacil weed killer, a water-soluble liquid
containing 2 Ib bromacil per gallon (present as lithium salt).
3. Hyvar®X-P brush killer, pellets containing 10% bromacil.
4. KrovarUivi weed killer, a wettable powder containing 40% bromacil
and 40% diuron.
5. KrovarUxII weed killer, a wettable powder containing 53% bromacil
and 27% diuron.
Commercial femulators prepare other formulations, including some which
contain other pesticides.
Chemical Properties, Degradation and Decomposition Process
Bromacil is a herbicide of a family called substituted uracils.
Many members of this family are strong photosynthesis inhibitors.
Bromacil has been, shown to be an inhibitor of photosynthesis in many
laboratory systems, and this effect is the probable cause of its herbicidal
activity. (Hoffmann et al.i/, Hilton et al..£/).
The lack of activity on nonphotosynthesizing plant tissue was confirmed
by Jordan et al.^.'. They found that bromacil had no effect on the dark growth
of tobacco callus tissue supplied with an organic energy source, except at
much greater concentrations than required for inhibition of photosynthesis.
Couchz/ found that one ppm of bromacil reduced photosynthesis ^C02 -
fixation in corn (Zea mays), cotton (Gossypium hirsutum), and soybeans
(Glycine Max).
I/ Hoffmann, C. E., J. W. McGahen, and P. B. Sweetser, "Effect of Substituted
Uracil Herbicides on Photosynthesis", Nature. 202 (4932):577-8 (1968).
21 Hilton, J. L., T. J. Monaco, D. E. Moreland, and W. A. Centner, "Mode
of Action of Substituted Uracil Herbicides," Weeds. 112:129-131 (1964).
3f Jordan, L. S., T. Murashige, J. D. Mann, and B. E. Day, "Effect of
Photosynthesis - Inhibiting Herbicides on Nonphotosynthetic Tobacco
Callus Tissue." Weeds. 14(2):134-6 (1966).
47 Couch, R. W. and D. Davis, "Effect of Atrazine, Bromacil and Diquat on
14-CO£ - Fixation in corn, cotton, and soybeans", Weeds, 14(3):
251-5 (1966).
17
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The chemical name of 5-bromo-3-sec-butyl-6-methyluracil was origi-
nally used by Chemical Abstract Services (CAS), and is the one accepted
for use on the pesticide label ingredient statement (Caswell, 1972)i/.
CAS now uses the name 5-bromo-6-methyl-3-(l-methylpropyl)-2,4(lH.3H)-
pyrimidinedione.
Photochemical Decomposition - Several investigations have been made of
the ef|ect of ultraviolet (UV) radiation on herbicides. Jordan et al.
(1965)—' subjected samples of several herbicides to various sources of
UV radiation. Three sources of UV radiation were used: far UV (wavelength
range, 240 to 260 nm, peak at 253.7 nm) ; middle UV (275 to 375 nm, peak
at 311 ran); and near UV (320 to 450 nm, peak at 360 nm). The lamps emitted
approximately 15 w at the peak wavelength. The samples were prepared by
allowing solutions (1 x 10"^ molar) to evaporate on 1-in. diameter alum-
inum planchets. The samples were placed 1 ft from the UV sources.
The results showed that the most extensive decomposition of bromacil
was caused by far UV radiation. However, a thin layer of decomposed
product apparently protected the lower layers, indicating that very
little protection is required to prevent photodecomposition. The author
noted that far UV radiation does not occur in natural sunlight. Signifi-
cant UV radiation above 290 nm occurs in sunlight and the photodecomposi-
tion mechanism may be the same at all UV wavelengths, although the rate
may vary. Wright (1967) 2/ also found that far UV radiation produces more
rapid decomposition of bromacil than middle or near UV radiation.
\J Caswell, R. L., D. E. Johnson, and C. Fleck, Acceptable Common Names
and Chemical Names for the Ingredient Statement on Pesticide Labels
(2nd ed.), Environmental Protection Agency, Washington, D.C. (June
1972).
2/ Jordan, L. S., J. D. Mann, and B. E. Day, "Effects of Ultraviolet
Light on Herbicides," Weeds, 13(l):43-46 (January 1965).
3/ Wright, W. L., "Photochemical Breakdown of Herbicides," (Abstract),
Proceedings, 20th Southern Weeds Conference, 20:391 (1967).
18
-------
Hill (1971)I/ reported that, in exposure tests in sunlight and in
several practical field tests, bromacil did not appear to be affected
adversely by sunlight. However, he presented no details of the analy-
tical method or the extent of exposure.
Kearney et al. (1969)27 obtained results showing that ultraviolet
radiation can greatly reduce the phytotoxicity of bromacil. In seeking
a method to decontaminate water supplies, he irradiated various solu-
tions of pesticides in water with a 450-w Hanovia lamp. This lamp is
an intense source of UV radiation and emits strongly in the far, middle
and near UV. The initial concentration of bromacil was 1 ppm. Kearney
used a bioassay for bromacil, but did not report any products formed from
the implied photodecomposition.
Degradation in Soil - Zimdahl (1968)-' studied the kinetics of the degrada-
tion of various herbicides in soil. Nine different herbicides were
applied at 8 ppm, and temperatures were maintained at either 13.2°C or
31.2°C. Moisture was maintained at about 507. of field capacity, and
monthly samples of the soil were analyzed. The following conclusions were
reported:
1. The rate of degradation followed a first order rate law.
2. The degradation was probably nonenzymatic.
3. The herbicides appeared to be attacked by chemical hydrolysis
at the halogen substitutent. (This conclusion was apparently
based upon kinetic data, not analytical data, and no hydrolysis
products were reported.)
Thermal Decomposition - Bromacil is stable up to its melting point of
158 to 159°C. However, it begins to sublime at temperatures below its
melting point (du Font, April, 1972)^./. Bromacil apparently begins to
I/ Hill, G. D., "Characteristics of Herbicides by Chemical Groups,"
Proceedings. 23rd Annual California Weed Conference (January 1971).
21 Kearney, P. C., E. A. Woolson, J. R. Plimmer, and A. R. Isensee,
"Decontamination of Pesticides in Soils," Residue Rev.. 29:137-
149 (1969).
3/ Zimdahl, R. L., "A Kinetic Analysis of Herbicide Degradation in Soil,"
Piss. Abstr. Int.. 29:849-B (1968).
tj E. I. du Pont de Nemours and Company, Inc., Bromacil Technical Data
Sheet, Wilmington, Delaware (April 1972).
19
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decompose above its melting point, but, according to Kennedy et al. (1969}—
the decomposition is not total even up to temperatures as high as 1000°C.
Table 1 shows weight losses of a commercial formulation of bromacil heated
to various temperatures (the exact nature of the formulation was not dis-
closed) .
Table 1. WEIGHT LOSSES ON COMBUSTION OF A COMMERCIAL
BROMACIL FORMULATION (PERCENT)
600CC
88.8
700° C
89.1
800°C
89.4
900°C
90.5
1000° C
91.3
Source: Kennedy et al.. op. cit. (1969).
The data in Table I is not only an indication of volatalization
but also an indication of the decomposition of inorganic carriers or
fillers in the formulation. Kennedy et al. (1969) apparently used a
solid commercial formulation containing 80% bromacil. Under experi-
mental conditions, the bromacil would most likely volatilize completely,
although the contact times were not given.
Kennedy et al. (1972)A/»1/ identified the volatile products of the
combustion of analytical grade bromacil at 900°C as carbon monoxide and
carbon dioxide; however, they noted that there were several unidentified
products. The sample gas was specifically analyzed for hydrogen bromide,
but It was not detected.
In other experiments at the same laboratories, Stojanovlc et al.
(1972)4/ subjected various pesticides to thermoshocking, or partial
degradation at temperatures below that required for complete destruction.
At the temperature employed for bromacil, 250°C for 30 min, the breaking
I/ Kennedy, M. V., B. J. Stojanovic, and F. L. Shuman, Jr., "Chemical
and Thermal Methods for Disposal of Pesticides," Residue Rev.. 29:
89-104 (1969).
2j Kennedy, M. V., B. J. Stojanovic, and F. L. Shuman, Jr., "Chemical
and Thermal Aspects of Pesticide Disposal," J. Environ. Quality,
1(1):63-65 (1972).
3/ Kennedy, M. V., B. J. Stojanovic and F. L. Shuman, Jr. "Analysis of
Decomposition Products of Pesticides" J. Agr. Food Chem., 20(2):
341-3 (1972).
4/ Stojanovic, B. J., Fay Hutto, M. V. Kennedy, and F. L. Shuman, Jr.,
"Mild Thermal Degradation of Pesticides," J. Environ. Quality.
1(4):397-401 (1972).
20
-------
of carbon-carbon bonds appeared to be minimal. The authors found that
bromacil turned black, and lost 342 of its weight. The remaining product
was believed to be 3-sec-butyl-o-methyluracil (infrared spectral analysis).
The formation of this product indicates that the bromine substituent was
lost.
Other Decomposition Processes - Kennedy et al. (1972) reported that con-
centrated sulfuric acid was effective in bringing about changes in bromacil
but did not elaborate on what the changes were. This is in agreement with
the manufacturer's information that bromacil decomposes slowly in strong
acid, but is stable in water, aqueous bases, and common organic solvents
(du Pont, April, 1972).
Hill (1971) reported the results of a volatilization test. Bromacil
was held in an air circulation oven at 120°F for 2 weeks. Losses were
less than O.lZ/week.
Occurrence of Bromacil Residues in Food and Feed Commodities
The Food and Drug Administration (FDA) monitors pesticide residues
in the nation's food supply as part of two programs—a "total diet:
program and a "market basket" study. Much of the data obtained is
published, and the literature is voluminous. However, published data
reveals that bromacil has not been reported as a significant residue
in any food class, nor is it routinely searched for in the FDA's multi-
residue analytical system which monitors pesticide residue in food.
Adequate individual compound methods exist for measuring bromacil residues.
The apparent reason for the absence of bromacil residue data is that the
pesticide is not widely used on major food and feed items. The absence
of bromacil residue data does not necessarily mean that it could not be
present in food.
Acceptable Daily Intake
The acceptable daily intake (ADI) is defined as the daily Intake
which, during an entire lifetime, appears to be without appreciable
risk on the basis of all known facts at the time of evaluation (Lu,
1973)A/- It is expressed in milligrams of the chemical per kilogram
of body weight (mg/kg).
I/ Lu, F. C., "Toxlcologlcal Evaluation of Food Additives and Pesticide
Residues and Their 'Acceptable Daily Intakes' for Man: The Role
of WHO, in Conjunction with FAO," Residue Rev.. 45:81-93 (1973).
21
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The ADI is established only by the FAO/WHO. Since bromacil is
used on so few food crops, the FAO/WHO has not yet determined an ADI
for bromacil.
Tolerances
Tolerances for bromacil are within the purview of tolerance
procedures for pesticide chemicals established under the Food, Drug,
and Cosmetic Act, as amended. Bromacil is primarily a monagricultural
herbicide. Most of its uses are commercial and industrial. Only two
crop sectors in the United States, citrus fruits and pineapple, have
bromacil tolerances. The tolerance for both is 0.1 ppm.i/
I/ Code of Federal Regulations. "USDA Summary of Registered Agricultural
Pesticide Chemical Uses," (Vol. I, 1970), Title 40, Part 180,210.
22
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References
Association of Official Analytical Chemists, Official Methods of Analysis
of the Association of Official Analytical Chemists, llth ed., Washington
D.C. (1970).
Bevenue, A. and J. N. Ogata, "Determination of Bromacil by Gas Chromatog-
raphy," J. Chromatog.. 46(1):110-11 (January 1970).
Caswell, R. L., D. E. Johnson, and C. Fleck, Acceptable Common Names and
Chemical Names for the Ingredient Statement on Pesticide Labels (2nd ed.),
Environmental Protection Agency, Washington, D.C. (June 1972).
Code of Federal Regulations. "USDA Summary of Registered Agricultural
Pesticide Chemical Uses" (Vol. I, 1970), Title 40, Part 180,210.
Couch, R. W. and D. Davis, "Effect of Atrazine, Bromacil, and Diquaton
14-C02 - Fixation in Corn, Cotton and Soybenas," Weeds. 14:(3):251-255.
E. I. du Pont de Nemours and Company, Inc., Bromacil Technical Data Sheet,
Wilmington, Delaware (April 1972).
Gutenmann, W. H. and D. J. Lisk, "Estimation of Residues of Uracil Herbi-
cides by Gas Chromatography After Evaporative Co-Distillation," J. Assoc.
Offie. Anal. Chem.. 51 (3):688-90 (1968).
Hill, G. D., "Characteristics of Herbicides by Chemical Groups," Proceedings.
23rd Annual California Weed Conference (January 1971).
Hilton, J. L., T. J. Monaco, D. E. Moreland, and W. A. Gentner, "Mode of
Action of Substituted Uracil Herbicides," Weeds. 112:129-131 (1964).
Hoffmann, C. E., J. W. McGahen, and P. B. Sweetser, "Effect of Substituted
Uracil Herbicides on Photosynthesis", Nature. 202(4932):577-8 (1968).
Jolliffe, V. A., B. D. Day, L. S. Jordan, and J. D. Mann, "Method of Deter-
mining Bromacil in Soils and Plant Tissues," J. Agr. Food Chem.. 15(1):
174-77 (1967).
Jordan, L. S., J. D. Mann, and B. E. Day, "Effects of Ultraviolet Light
on Herbicides," Weeds. 13(l):43-46 (January 1965).
Jordan, L. S., T. Murashige, J. D. Mann, and B. E. Day, "Effect of
Photosynthesis - Inhibiting Herbicides on Nonphotosynthetic Tobacco
Callus Tissue," Weeds. 14(2):134-6 (1966).
Kearney, P. C., E. A. Woolson, J. R. Plimmer, and A. R. Isensee,
"Decontamination of Pesticides in Soils," Residue Rev.. 29:137-149 (1969).
Kennedy, M. V., B. J. Stojanovic, and F. L. Shuman, Jr., "Chemical and
Thermal Methods for Disposal of Pesticides," Residue Rev.. 29:89-104 (1969)
Kennedy, M. V., B. J. Stojanovic, and F. L. Shuman, Jr., "Chemical and
Thermal Aspects of Pesticide Disposal," J. Environ. Quality. l(l):63-65
(1972).
23
-------
Kennedy, M. V., B. J. Stojanovic and F. L. Shuman, Jr. "Analysis of
Decomposition Products of Pesticides" J. Agr. Food Chem.. 20(2):341-3 (1972),
Loux, H. M. (to E. I. du Pont de Nemours and Company, Inc.), U.S. Patent
No. 3,235,357 (15 February 1966).
Lu, F. C., "lexicological Evaluation of Food Additives and Pesticide
Residues and Their 'Acceptable Daily Intakes' for Man: The Role of
WHO, in Conjunction with FAO," Residue Rev.. 45:81-93 (1973).
Pease, H. L., "Determination of Bromacil Residues," J. Agr. Food Chem.
14(1):94-96 (1966).
Pease, H. L., and J. F. Deye, "Bromacil," Analytical Methods for Pesti-
cides. Plant Growth Regulation, and Food Additives. G. Zweig (ed.),
Academic Press, New York (1967).
Stojanovic, B. J., Fay Hutto, M. V. Kennedy, and F. L. Shuman, Jr., "Mild
Thermal Degradation of Pesticides," J. Environ. Quality. 1(4):397-401
(1972).
U.S. Department of Health, Education, and Welfare, Food and Drug
Administration, Pesticide Analytical Manual. Vol. II (1971).
von Rumker, R., E. W. Lawless, and A. F. Meiners, "Production, Distribu-
tion, Use and Environmental Impact Potential of Selected Pesticides,"
Final Report, Contract No. EQC-311, for Council on Environmental
Quality, Washington, D.C. (1974).
Wright, W. L., "Photochemical Breakdown of Herbicides," (Abstract),
Proceedings. 20th Southern Weeds Conference. 20:391 (1967).
Zimdahl, R. L., "A Kinetic Analysis of Herbicide Degradation in Soil,"
Piss. Abstr. Int.. 29:849-B (1968).
Zweig, G. and J. Sherma, Analytical Methods for Pesticides and Plant
Growth Regulators.. Vol. VI; Gas Chromatographic Analysis, p. 603,
Academic Press, New York (1972).
24
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SUBPART II. B. PHARMACOLOGY AND TOXICOLOGY
CONTENTS
Page
Acute, Subacute and Chronic Toxicity 26
Acute Oral Toxicity - Rats 26
Acute Inhalation Toxicity - Rats 26
Subacute Oral Toxicity - Rats 26
Chronic Oral Toxicity - Rats 27
Acute Oral Toxicity - Dogs 29
Chronic Oral Toxicity - Dogs 29
Other Toxicological Evaluations 29
Dermal - Acute Toxicity - Rabbits 29
Dermal - Sensitization Test - Guinea Pigs 30
Eye Irritation 30
Toxicity to Domestic Animals 30
Symptomalogy and Pathology Associated with Mammals 32
Metabolism 33
Absorption 33
Excretion 33
Biotransformation 33
Effect on Reproduction 34
Teratogenic Effects 34
Behavioral Effects 35
Toxicity Studies with Tissue Culture 35
Mutagenic Effects 35
Oncogenic Effects 36
Effect on Humans 36
References 37
25
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This section reviews pharmacological and toxicological data on bromacil.
Subsections present information on acute, subacute and chronic studies in
different species of laboratory and domestic animals by various routes of
administration. Information is reviewed concerning effects on reproduction
and mutagenic effects. There was little available data on behavioral effects,
tissue culture studies, oncogenlc effects and the effect on humans. The
section summarizes rather than Interprets scientific data reviewed.
Acute. Subacute and Chronic Toxicity
Acute Oral Toxicity - Rats - The LD50 value for bromacil (as active ingre-
dient in 80% wettable powder) in male rats has been reported in petition
data (Zapp, 1965, EPA Pesticide Petition No. 6F0499 Vol. II, and Edson et
al., 1965)I/>!/ to be 5,200 mg/kg (95% confidence limits 5,024 mg—5,330
mg/kg). Another reported LDso value was 5,175 mg/kg based on active
ingredient (Sherman et al.).!'.
Acute Inhalation Toxicity - Rats - In each test bromacil was atomized into
an inhalation chamber at levels of 2.1 mg/liter and 4.8 mg/liter for 4 hr.
There were four test animals for each exposure and the animals were observed
for 14 days post exposure. All the animals survived. The symptoms displayed
during exposure were rapid and deep respiration and ruffled fur. One of the
animals in the 4.8 mg/litter exposure had dried blood around the nose and
mouth (Zapp, 1965).
Subacute Oral Toxicity - Rats - Bromacil (80% wettable powder) was given to
male rats by intubation as a 15% aqueous suspension five times a week for 2
weeks. Five out of six animals survived 10 daily doses of 1,035 mg/kg of
body weight. Four out of six animals died after four to five doses of 1,500
mg/kg/day whereas there were no deaths when 10 daily doses of 650 mg/kg of
bromacil were administered. The 650 mg/kg and the 1,035 mg/kg levels did
produce some pathological changes in the livers (focal cell hypertropy and
hyperplasia) of animals which were sacrificed after 10 days exposure to the
pesticide. These symptoms were no longer evident in animals after a 14-day
recovery period (Zapp, 1965).
I/ Zapp, J. A., Jr., Report on Bromacil, EPA Pesticide Petition No. 6F0499,
Vol. II, 1965.
2J Edson, E. F., D. M. Sanderson, and D. N. Noakes, "Acute Toxicity Data
for Pesticides (1964)." World Rev. Pest Con.. 4:36-41 (1965).
3/ Sherman, H., et al., Report 12-66, EPA Pesticide Petition No. 6F0499,
Vol. I (1963).
26
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Chronic Oral Toxlclty - Rats - Bromacil (80% wettable powder containing
83.0% AI) was fed to rats for a 2-year period (Sherman, et al., 1963).
Group Number
I (control)
I-A (control)
II
III
IV
Level of
Bromacil in Diet
CPUS/ + 1%
GPLC + 1% Co
GPLC + 1% Co + 0.005% (50 ppm)
GPLC + 1% Co + 0.025% (250 ppm)
GPLC + 1% Co + 0.125% (1,250 ppm)
ja/Ground Purina Laboratory Chow.
b/ Corn oil.
Hematology examinations and urinalysis were run on six males and six
females once a month for the first 3 months and every 3 months thereafter.
Biochemical tests of six males and six females of each group were run at
the end of 1, 3, 6, 9, 12 and 24 months. At the end of 3, 6 and 12 months
of feeding, the number of animals of each sex was reduced to 32, 30 and
24, respectively. The brain, heart, lung, liver, spleen, kidney, testis,
stomach, adrenals and pituitary were weighed and pathological examinations
were made on 26 other body tissues. The daily dosage for male rats ranged
from 154.2 to 38.7 ppm (4:1) and for female rats 143.3 to 39.3 ppm (3.6:1).
It is normal for dosage to decrease since rats consume less per body weight
as they grow larger. J
The actual amounts of bromacil ingested in the various diets are shown
in Table 2. Mortalities which occurred within the group are shown in Table
3.
The female rats on the 0.125% bromacil diet suffered weight retarda-
tion for the first and second year. There were no clinical signs of toxi-
city. During the first year, three control animals died and there were
three deaths in the treated groups.
Table 2. CONSUMPTION OF BROMACIL
Days of test
0.7
105-112
203-210
490-504
602-616
714-728
0.005%
fag/kg)
08
27
83
55
46
1.37
0.025%
(mg/kg)
30.2
11.3
9.6
8.0
6.56
0.125%
(mg/kg)
154.2
56.4
47.6
39.7
37.9
38.7
Source: Sherman, et al., op. cit. (1963),
27
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Table 3. MORTALITY OF RATS CONSUMING BROMACIL
Dietary
level
Killed by Killed Found
design extremis dead
Male Female Male Female Male Female
Survived
24 months
Male Female
0
0
0.005
0.025
0.125
11
10
12
12
12
12
12
12
11
12
2
6
8
3
8
8
8
6
8
3
14
9
8
9
8
3
6
9
5
4
9
11
8
12
10
13
10
9
12
17
Source: Sherman et al. op. cit. (1963).
There were no unusual alterations in the hematology, urinalysis and
clinical chemistry evaluations. No gross pathological lesions were
observed. There appeared to be a dose-related effect on the thyroid.
Focal light cell hyperplasia and focal follicular cell hyperplasia were
noted somewhat in controls but observed slightly more often in the 'hyroids
of rats at the high dose. One follicular cell adenoma occurred in a
female rat at the highest dose level. There were no excessive accumula-
tions of residues in the tissues.
Another investigation (Zapp, 1965) involved a 90-day oral toxicity
test of bromacil in rats. Ten male and 10 female rats were placed in
each group. The dosages were as follows:
Dietary level
•a/
Group Number
1
2
3
4
4A
4B
Ppm
0
50
500
2,500 (0-6 weeks)
5,000 (7-10 weeks)
5,000 (11-13 weeks)
6,000 (llth week)
7,500 (12-13 weeks)
Estimated-'
(mg/kg)
2.5
25.0
125.0
250.0
250.0
300.0
375.0
a/ Estimation by reviewer based on a 500-g rat consuming 25 g of
diet a day.
28
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No deaths occurred and no signs of toxiclty were observed. The male
rats in Groups 4A and 4B exhibited a reduced growth rate during the last
3 weeks of the test. The hematology and urinalysis values were within
normal limits. There were no pathological changes of significance in the
groups receiving 50 and 500 ppm of bromacil. For the groups receiving
5,000 ppm and above, there were microscopic changes in the thyroids,
suggestive of increased glandular activity.
Acute Oral Toxiclty - Dogs - An attempt was made to determine the acute
oral toxiclty of bromacil in dogs (Hazelton Laboratories, 1966).i' Bromacil
(80% wettable powder) as a massive dose (5 g/kg) was given by capsule to a
dog. The dog exhibited excessive emesis, copious salivation, weakness, loss of
coordination, excitability, diarrhea and mydriasis. Forty-eight hr
later, six divided doses were given and repeated emesis, salivation,
mydriasis and sanguineous diarrhea occurred.
The second dog was given two oral doses of bromacil 5 days apart (200
and 250 mg/kg); each dose evoked repeated emesis. A lethal dose was not
obtained in the dog because of emesis.
Chronic Oral Toxicity - Dogs - A 2-year feeding study of bromacil in dogs
was also conducted.^/ Six dogs (three male and three female) in each of
four groups received the following dosages of dietary bromacil:
Group 1 0.0% (Control)
2 0.005%
3 0.025%
4 0.125%
The dogs in the 0.125% level declined in weight at the start of the
experiment and then weights stabilized between 1 to 1.5 kg lower than the
other dogs in the test. Throughout the duration of the test, clinical
signs, such as appearance, rectal temperature, pulse and respirationi
appeared to be normal.
The only death loss was an animal on the 0.005% dosage level. Illness
and death were judged not to be associated with the test compound. A
subdural hemorrage was observed in the spinal column. Throughout the
course of the study, there were no significant alterations in hematology,
urinalysis and blood chemistry. There was no effect on organ weight and
no significant pathology occurred at the microscopic level. There was
no evidence of excessive accumulation of residues in the tissues.
Other Toxicologlcal Evaluations -
Dermal - Acute Toxicity - Rabbits - An acute skin absorption toxicity
tept was made on rabbits. Bromacil was applied to the intact skin (clipped)
of three male rabbits. A 70% aqueous paste was made up to supply 5,000 mg/kg.
The contact period was 24 hr and the animals were observed for 14 days. There
were no signs of toxicity or gross pathological changes. The approximate
lethal dose (AID) was estimated to be greater than 5,000 mg/kg (Zapp, 1965).
I/ Hazelton Laboratories, Report on Bromacil, EPA Pesticide Petition No.
6F0499, Vol. II, 1966.
J2/ Bromacil Report, EPA Pesticide Petition No. 6F0499, Section C.
29
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Dermal - Sensitization Test - Guinea Pigs - Ten guinea pigs were
prepared by clipping fur and abrading the skin. A 50% suspension of
bromacil in 1% aqueous Duponal PT was applied to these areas for 24 hr.
Animals with abraded skin were exposed 3 times a week for 3 weeks. They
were reexposed after 2 or 3 weeks rest. There appeared to be no induced
skin sensitivity. The skin of the younger animals was mildly irritated
(Zapp, 1965).
Eye Irritation - Ten milligrams of bromacil (0.1 ml of a 10% suspension
in mineral oil) was placed on the surface of two rabbits' eyes. One eye of
each rabbit was then washed for 1 minute with tap water, starting 20 seconds
after contact. The other eye of each rabbit was not washed. A mild temporary
conjunctivitus was observed in both washed and unwashed eyes. No corneal
damage was observed in either washed or unwashed eyes. The experiment was
repeated as above, with identical results, using 50% wettable powder (Zapp,1965).
Toxicity to Domestic Animals - Palmer and Radeleff (1969).i/ have evaluated
the toxicity of multiple-dosing of bromacil in cattle, sheep, and chickens.
The results of these tests are given in Table 4.
One dose (250 mg/kg) administered to a yearling calf produced poison-
ing with survival and a 14% weight loss.
The results with sheep were varied. A dose of 50 mg/kg given 10 times
by drench produced no effect. When the dosage was given by capsule, the
animal was poisoned, survived and sustained an 8% weight loss. A 100 mg/kg
dosage in capsule form had no observable effects, while a drench produced
poisoning. At the 250 mg/kg level, poisoning occurred after the third dose,
and, by capsule, eight doses were consumed before poisoning occurred.
Chickens appeared to tolerate a dose of 500 mg/kg. However, there
was a significant reduction in weight gain. Weight gain was also reduced
slightly at the 250 mg/kg level.
The authors commented that bromacil application rates range from 1.6
to 20 Ib/acre. They felt that a rate of 20 Ib/acre would not be hazardous
to cattle or chickens, but rates of application in excess of 5 Ib/acre
would be hazardous to sheep.
Palmer (1964)—/ reported that the administration of five doses of 250
mg/kg each to sheep of bromacil produced tympany and stilted gait within 4
hr after administration of the first dose. After five doses of bromacil the
animal slowly recovered and had marked lameness. When the dosage was
reduced to 100 mg/kg, the administration of 11 treatments produced no
clinical symptoms but there was an 11% weight loss.
I/ Palmer, J. S., and R. D. Radeleff, "The Toxicity of Some Organic
Herbicides to Cattle, Sheep, and Chickens," USDA Prod. Res.. Report
No. 106; 1-26 (1969).
2f Palmer, J. S., "Toxicity of Methyluracil and Substituted Urea and Phenol
Compounds to Sheep," Amer. Vet. Med. Assoc. J.. 145:787-789 (1964).
30
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Table 4. RESULTS OF MULTIPLE ORAL DOSING OF
IN CATTLE, SHEEP, AND CHICKENS^'
Animal
and dosage
received
(me/ke)
Cattle:
100
100
250
Sheep :
25
50
50
100
100
250
250
Chickens!/
100
250
500
Controls
Doses
Number
10
10
10
10
10
10
10
10
5
10
10
10
10
Means of
dosing
Drench
Capsule
Capsule
Drench
Capsule
Drench
Capsule
Drench
Drench
Capsule
Capsule
Capsule
Capsule
Results and remarks
NH£/
NIE
Poisoned after one dose and
survived, 14% weight loss
NIE
Poisoned and survived,
8% weight loss
NIE
NIE
Poisoned and survived,
97. weight loss ,
Poisoned after three doses
survived, 97. weight loss
Poisoned after eight doses
survived, 87. weight loss
49% weight gain
397. weight gain
24% weight gain
48% weieht train
a/Hyvar®X, 80% wettable powder.
b/ Adapted from Palmer and Radeleff (1969).
£/ NIE indicates no ill effects apparent.
d_/ Average results of five treated chickens.
31
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Tympanites is commonly encountered in cattle and sheep dosed with
bromacil. Williams et al. (1963)!/ found that certain chlorinated hydro-
carbons, organophosphates, and carhamate compounds stimulate gas produc-
tion in vitro by rumen holotrich protozoa whereas these compounds had no
appreciable effect when rumen bacteria inoculum was used. In these
experiments total gas production was measured by manometric techniques.
No attempt was made to determine the chemical composition of the gases
produced. Kutches et al. (1970)^.' studied the effect of a number of
insecticides and herbicides on in vitro rumen fermentation. The parameters
of investigation included dry matter disappearance, volatile fatty acid
production, and changes in protozoal numbers. With dosages of 0.0, 100,
250, 500, 750, and 1,000 ppm, the respective values for percent in vitro
dry matter disappearance were: 28.5, 28.4, 27.7, 25.0, 22.8 and 18.5.
The volatile fatty acid production was not affected by 1,000 ppm of
bromacil. The numbers of ciliated protozoa increased slightly in the
presence of 100 ppm bromacil but decreased sharply as the bromacil con-
centration exceeded 500 ppm.
The results indicated that high concentration of bromacil (1,000 ppm)
significantly affected rumen microbial processes. No significant effects
in in vitro forage digestability were noted at lower concentrations (250
ppm and below). Since feedstuff contamination is usually less than 250 ppm,
it was concluded that bromacil would have negligible affect on rumen
digestability or other associative rumen function.
Symptomalogy and Pathology Associated with Mammals - In the dog, massive
doses of bromacil caused excessive emesis, copious salivation, weakness,
lack of coordination, excitability, diarrhea, and mydriasis (Hazelton
Laboratories,1966). In the rat, a near-toxic dose of bromacil caused an
initial weight loss of the animal. In acute toxicity cases the respiration
rate became very rapid. Discomfort, prostration, salivation and lack of
coordination occurred (Zapp, 1965).
In cattle and sheep, bromacil poisoning caused a weight loss, anorexia
and depression, tympanites, and incoordinated gait (Palmer, 1964; Palmer
and Radeleff, 1969).
I/ Williams, P. P., J. D. Bobbins, J. Gutienez, and R. E. Davis, "Rumen
Bacterial and Protozoal Responses to Insecticides Substrates,"
Appl. Microbiol.. 11:517-522 (1963).
2J Kutches, A. J., D. C. Church, and F. Duryee, "lexicological Effects of
Pesticides on Rumen Function in Vitro." J. Agr. Food Chem.. 18(3):
430-433 (1970).
32
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Metabolism
Absorption - Brotnacil is apparently not excreted via the gastrointestinal
tract of cows, since Gutenmann and Lisk (1970)i/ found no bromacil in feces
of cows fed 5 and 30 ppm bromacil in the feed for 4 days.
Excretion - Gardiner et al. (1969)!/ found that rats fed 1,250 ppm bromacil
for 1 month excreted five to six metabolites in the urine, the main one
being 5-bromo-3-sec_-butyl-6-hydroxymethyluracil. 5-Bromouracil was not
found as a product of bromacil metabolism.
Urine samples from workers at two different locations in a bromacil
production plant were analyzed for bromacil and its metabolites. The
results indicated that bromacil was metabolized by man in a manner similar
to that in rats (bromacil was found and 5-bromo-3-sec-butyl-6-hydroxymethyl-
uracil was found to be the principal metabolite). No 5-bromouracil was
found in either hvdrolyzed or nonhydrolyzed urine samples from humans
(Du Pont, 1966) .!'
Biotransformation - Gardiner et al. (1969) found six metabolites of bromacil
in the urine of rats fed 1,250 ppm bromacil for 1 month. The primary
metabolite, 5-bromo-3-sec-butyl-6-hydroxymethyluracil was present in the
urine as a conjugate which was hydrolyzed with /0"~glucuronidase-arylsulfatase
enzyme solution.
Additional metabolites found in lesser quantities were 5-bromo-3-
(2-hydroxy-l-methylpropyl)-6-methyluracil, 5-bromo-3-(2-hydroxy-l-
methylpropyl)-6-hydroxy-methyluracil, 3-sec-butyl-6-hydroxymethyluracil,
5-bromo-3-(3-hydroxy-l-methylpropyl)-6-methyluracil, 3-sec-butyl-6-
methyluracil, and an unknown bromine-containing compound of mol. wt 339.
McGahen and Hoffmann (1963a)—' found that bromacil was not incorporated
into Escherichia coli DNA. These authors reported (1963b)5/ similar findings
in mice.
17 Gutenmann, W. H., and D. J. Lisk, "Metabolism and Excretion of Bromacil
in Milk of Dairy Cows," J. Agr. Food Chem.. 18(1):128-129 (1970).
2J Gardiner, J. A., R. W. Reiser, and H. Sherman, "Identification of the
Metabolites of Bromacil in Rat Urine," J. Agr. Food Chem.. 17(5):
967-973 (1969).
_3/ Du Pont de Nemours Co., Supplementary Report on Bromacil, EPA Pesticide
Petition No. 6F0499 (1966).
4/ McGahen, J. W., and C. E. Hoffmann, "Action of 5-Bromo-3-sec-butyl-
6-methyluracil on Escherichia coli 15T," Nature. 200(4906):571-572
(1963a).
5/ McGahen, J. W., C. E. Hoffmann, "Action of 5-Bromo-3-sec-butyl-6-
methyluracil as Regards Replacement of Thymine in Mouse DNA,"
Nature. 199(4895):810-811 (1963b).
33
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Effect on Reproduction
The effect of bromacil on reproduction in the rat has been reported.
During a 2-year chronic toxicity study, 12 male and 12 female rats each
were allowed to continue their regular feeding regimin and reproduce. One
of the groups continued to be fed the control diet. The test group
continued to consume 0.025% bromacil in the diet. The original rats were
called the FQ generation. The first litter produced from this group became
the Fia generation and the second mating produced the FU, generation. The
Fib litter was maintained on the same diet and at 100 days of age they were
mated to yield the F2a and F£b litters.
There were no marked differences between the reproductive performance
of the control and test animals. There were no deformed young. The
fertility, gestation, viability and lactation indices were not significantly
different. Furthermore, there were no gross or microscopic pathological
differences. I/
Teratogenic Effects
There were no deformities found in the previously cited reproductive
study on rats.
A study was made of the effects of bromacil on reproduction in the
rabbit (Paynter, 1966) ,2J Bromacil (80% wettable powder) was fed to New
Zealand white rabbits that had an initial weight of 3.0 to 4.7 kg. The
groupings and dosages were as follows:
Number of Dietary level of
Group number rabbits bromacil (ppm)
1 (Control) 9 0
2 9 50
3 8 250
The females were bred and the above dosages were administered starting
with the eighth day of pregnancy and continuing through the 16th day. The
does were returned to the untreated basal diet on the 17th day. On the
28th or 29th day after breeding, three does each from both the control and
50 ppm diet groups were sacrificed. Four does on the 250 ppm diet were
killed. After parturition, all the remaining does were killed and one-
third of the young was prepared for tissue clearing to observe any skeletal
defects.
No gross manifestations of teratogenic effect were observed in the
fetuses and there were no abnormal bone structures.
I/ Bromacil Report, EPA Pesticide Petition No. 6F0499, Section C.
2J Paynter, 0. E., Hazleton Report, Ref. Mro-879, 1966, EPA Pesticide
Petition No. 6F0499, Vol. II.
34
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Behavioral Effects
No studies were found in the literature concerning the behavioral
effects of bromacil.
Toxicity Studies with Tissue Culture
No information was found on toxicity studies with tissue cultures.
Mutagenic Effects
Because of the possibility that bromacil (5-bromo-3-sec-butyl-6-
methyluracil) could be metabolized in vivo to the potent mutagen,
5-bromouracil, experiments have been conducted to determine if bromacil
yields mutagenic effects in laboratory animals and to determine whether
5-bromouracil can be detected as a bromacil metabolite.
No 5-bromouracil was detectable in either urine from bromacil produc-
tion plant works (Du Pont, 1966) or in urine of rats fed bromacil (Gardiner
et al., 1969).
McGahen and Hoffmann (1963b) could not detect bromacil in mouse DNA.
These same authors evaluated the action of bromacil on Escherichia coli
15T using labeled bromacil. In growth experiments, bromacil was not
inhibitory to E. coli 1ST. Escherichia coli 1ST is a thymine-requiring
mutant. E. coli 15T cells in the log phase were exposed to 10 microcuries
of labeled bromacil for various periods, chilled and harvested. The cells
were washed with water and cold 5% trichloroacetic acid. Bromacil was
readily washed from the cells. Furthermore, no radioactivity was detected
in the DNA of cells exposed to bromacil.
McGahen and Hoffman (1966)—' further examined the mutagenic effects
of bromacil on bacteriophage. From their earlier work it was not com-
pletely ruled out that there may be indirect mutagenic effect. They used
mutant AP72, E. coli B and E. coli K12 (X) organisms in a back mutation
rate study, fney observed no mutagenic effect of bromacil. The other
substituted 5-bromouracils did not appear to be mutagenic. The explanation
was given that the alkyl substitution prevents incorporation of bromacil
into DNA or the precursors.
Andersen et al. (1972)—' has evaluated 110 herbicides for their ability
to induce point mutations in one or more of four different microbial systems.
In one test utilizing eight histidine requiring mutants of Salmonella
typhimurium, bromacil tested negative to reversion to histidine independence.
The effect of bromacil in the induction of the r II mutants of T4 bacteri-
ophage was not different from the control. An evaluation was also made on
I/ McGahen, J. W., and C. E. Hoffman, "Absence of Mutagenic Effects of 3-
and 6-Alkyl-5-bromouracil Herbicides on a Bacteriophage," Nature
(London), 209(5029): 1241-1242 (1966).
2J Andersen, K. J., E. G. Leighty, and M. T. Takahashi, "Evaluation of
Herbicides for Possible Mutagenic Properties," J. Agr. Food Chem..
20(3):649-656 (1972).
35
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the reversion of the guanine-cytosine transition r II mutant AP72. In
general, the herbicides evaluated were not mutagenic in this test system.
Siebert and Lemperle (1974)i' found that bromacil did not induce mitotic
gene conversion in a diploid strain of the ascomycete Saccharomyces
cerevisiae heteroallelic at two loci in a test which reacts very sensitively
to compounds that induce base-pair substitution as well as frame-shift
mutations.
Epstein et al. (1972)2/ found that bromacil in the dominant lethal
assay in mice, when administered either by intraperitoneal injection as a
single dose of 150 mg/kg or by gavage for five successive doses of 750 mg/kg
and 1,000 mg/kg, was not mutagenic.
Ficsor and Nil Lo Piccolo (1972)3/ found bromacil was not mutagenic by
the Bacterial-plate assay method. It was inactive in its ability to revert
two E._ coli lac - amber mutants to the lactose - fermenting phenotype and a
cys - and two len - auxotrophs to prototrophy.
Oncogenic Effects
A follicular cell adenoma was found in a female rat that was retained
on a long-term study consuming 0.125% bromacil in the diet (Lawless),^/
During the 2-year chronic toxicity studies in dogs and rats, discussed
previously, no evidence of oncogenic effects due to bromacil administration
was observed in any of the test animals (Sherman, et al., 1966; Zapp, 1965).
Effect on Humans
No information was found on the effect of bromacil to humans on an
acute basis, under field conditions, or in the manufacturing process.
I/ Siebert, D. and E. Lemperle, "Genetic Effects of Herbicides: Induction
of Mitotic Gene Conversion in Saccharomyces cerevisiae," Mutation
Research,(22):111-120 (1974).
2J Epstein, S. S., et. al., "Detection of Chemical Mutagens by the Dominant
Lethal assay in the Mouse," Toxicol. Appl. Pharmacol..(23);288-325
(1972).
3/ Ficsor, G. and G. M. Nii Lo Piccolo, "Survey of Pesticides for Mutageni-
city by the Bacterial - Plate Assay Method," Newslett. Environ.
Mutagen Society.(6);6-8 (1972).
4/ Lawless, E. W., Report on Bromacil, EPA Pesticide Petition No. 6F0499,
Vol. I.
36
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References
Andersen, K. J., E. G. Leighty, and M. T. Takahashi, "Evaluation of Herbicides
for Possible Mutagenic Properties," J. Agr. Food Chem., 20(3):648-656 (1972).
Bromacil Report, EPA Pesticide Petition Ho. 6F0499, Section C.
Du Pont de Nemours and Co., Supplementary Report on Bromacil, EPA Pesticide
Petition No. 6F0499 (1966).
Edson, E. F., D. M. Sanderson, and D. N. Noakes, "Acute Toxicity Data for
Pesticides (1964)." World Rev. Pest Con.. 4:36-41 (1965).
Epstein, S. S., et. al., "Detection of Chemical Mutagens by the Dominant
Lethal Assay in the Mouse," Toxicol. Appl. Pharmacol.. 23: 288-325 (1972).
Fiacor, G., and G. M. Nil Lo Piccolo, "Survey of Pesticides for Mutagenlcity
by the Bacterial - Plate Assay Method," Newslett. Environ. Mutagen Society,
(6): 6-8 (1972).
Gardiner, J. A., R. W. Reiser, and H. Sherman, "Identification of the
Metabolites of Bromacil in Rat Urine," J. Agr. Food Chem.. 17(5):967-973
(1969).
Gutenmann, W. H., and D. J. Lisk, "Metabolism and Excretion of Bromacil in
Milk of Dairy Cows," J. Aer. Food Chem.. 18(1);128-129 (1970).
Hazelton Laboratories, Report on Bromacil, EPA Pesticide Petition No. 6F0499,
Vol. II, (1966).
Kutches, A. J., D. C. Church, and F. Duryee, "lexicological Effects of
Pesticides on Rumen Function in Vitro," J. Agr. Food Chem., 18(3):430-
433 (1970).
Lawless, E. W., Report on Bromacil, EPA Pesticide Petition No. 6F0499,
Vol. I.
McGahen, J. W., and C. E. Hoffmann, "Absence of Mutagenic Effects of 3- and
6-Alkyl-5-bromouracil Herbicides on a Bacteriophage," Nature (London),
209(5029):1241-1242 (1966).
McGahen, J. W., C. E. Hoffmann, "Action of 5-Bromo-3-sec-butyl-6-methyluracil
as Regards Replacement of Thymine in Mouse DNA," Nature. 199(4895):
810-811 (1963b).
McGahen, J. W., and C. E. Hoffmann, "Action of 5-Bromo-3-sec-butyl-6-methyl-
uracil on Escherichia coli 15T." Nature. 200(4906):571-572 (1963a).
Palmer, J. S., "Toxicity of Methyluracil and Substituted Urea and Phenol
Compounds to Sheep," Amer. Vet. Med. ABSOC. J.. 145:787-789 (1964).
37
-------
Palmer, J. S. and R. D. Radeleff, "The Toxicity of Some Organic Herbicides
to Cattle, Sheep, and Chickens," USDA Prod. Res., Report No. 106;1-26
(1969).
Paynter, 0. E., Hazleton Report, Ref. Mro-879, 1966, EPA Pesticide
Petition No. 6F0499, Vol. II.
Sherman, H., et al., Report 12-66, EPA Pesticide Petition No. 6F0499,
Vol. I (1963).
Siebert, D. and E. Lemperle, "Genetic Effects of Herbicides: Induction of
Mitotic Gene Conversion in Saccharomyces cerevisiae." Mutation Research,
22:111-120 (1974).
Williams, P. P., J. D. Robbins, J. Gutienez, and R. E. Davis, "Rumen
Bacterial and Protozoal Responses to Insecticides Substrates," Appl.
Microbiol.. 11:517-522 (1963).
Zapp, J. A., Jr., Report on Bromacil, EPA Pesticide Petition No. 6F0499,
Vol. II, (1965).
38
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SUBPART II. C. FATE AND SIGNIFICANCE IN THE ENVIRONMENT
CONTENTS
Effects on Aquatic Species
Page
Fish .............................. 40
Lower Aquatic Organisms ............ • ........ 40
Effects on Wildlife ........................ 41
Effects on Insects ........................ 41
Effects and Residues in the Soil ................. 41
Interactions with Lower Terrestrial Organisms .......... 41
Residues in Soil/Laboratory Studies ............... 44
Residues in Soil/Field Studies ................. 46
Monitoring Studies ....................... 49
Residues in Water ......................... 49
Residues in Air .......................... 50
Effects and Residues in Nontarget Plants ............. 50
Bioaccumulation, Biomagnification ................. 51
Environmental Transport Mechanisms ................ 51
References ............................ 52
39
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This section contains data on the environmental effects of bromacil,
including effects on aquatic species, wildlife, beneficial insects, soil,
water, air, and nontarget plants. The section summarizes rather than inter-
prets data reviewed.
Effects on Aquatic Species
Fish - TLm values for Bluegill sunfish, Rainbow trout, and carp, based on
an 80% formulation, indicate a low order of fish toxicity:.!/
Bluegill sunfish
TLm for 24 hr. - 103 ppm
TLm for 48 hr. - 71 ppm
Rainbow trout
TLm for 24 hr. - 102 ppm
TLm for 48 hr. - 75 ppm
TLm for 72 hr. - 38 ppm
TLm for 24 hr. - 164 ppm
TLm for 48 hr. - 164 ppm
Yoshida and Nishiuchi£' list the 48 hour TLm values for carp, Jap-
anese goldfish and killifish as 10-40 ppm in each instance. The 48 hour
TLm value for loach is>40 ppm and for tadpole, 230 ppm. The 72 hour value
for crawfish is 40 and the 3 hour value for the waterflea is^40. Data on
the effects of bromacil to fishes under field conditions appears to be non-
existent. Registered labels of bromacil-containing commercial pesticides
do not carry any warning or caution statements regarding fish toxicity.
Lower Aquatic Organisms - Hoffman (1973),!/ in a report on the mode of action
of bromacil and related uracils, stated that a monuron-reslstant strain of
Euglena showed similar resistance to Bromacil; the resistant strain was not
affected by bromacil at 40 ppm, and only partially inhibited at 100 ppm.
By comparison, a wild strain of Euglena was markedly inhibited at 2 ppm and
completely inhibited at 10 ppm. Neither strain was affected by bromacil in
the dark, indicating that inhibition of photosynthesis is one of the mechanisms
of phytotoxic actions of bromacil. No other data was found on the interactions
between bromacil and lower aquatic organisms.
_!/ E. I. du Pont de Nemours and Company, Inc., Personal communication
(1974).
21 Yoshida, K., and Y. Nishiuchi, "Toxicity of Pesticides to Some Water
Organism" Bull of Agr. Chem Inspect. Stn. (Tokyo)12: 122-128 (1972).
3j Hoffman, C. E., "The Mode of Action of Bromacil and Related Uracils,"
Second International Conference of Pesticide Chemical Proceedings.
(1971). In: Ashton and Crafts, Mode of Action of Herbicides. John
Wiley & Sons, pp. 430-431 (1973).
40
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Effects on Wildlife
No data was found regarding laboratory experiments on the toxicity
of bromacil to wildlife, or the effects of bromacil to wildlife under
field conditions. E. I. du Pont de Nemours (1974) reported that the eight-
day dietary LCso of Bromacil for both the mallard duck and the bobwhite
quail is greater than 10,000 ppm.
The Handbook of Toxicity of Pesticide to Wildlife (Tucker and
Crabtree, 1970)i/ contains no entries on bromacil.
Pimentel's summary on "Ecological Effects of Pesticides on Nontar-
get Species" (1971)1/ does not include any data on the effects of bromacil
on wildlife or other nontarget species.
Effects on Insects
Bromacil was tested as a spray at 10,000 ppm against housefly, roach,
aphid (systemic) and mite and was found to be totally lacking in insecticidal
and acaricidal activity Anderson et al., (1971).I/
In laboratory and field studies (mostly spraying) on the effects of
honey bees, Aphis mellifera L., conducted in California between 1950 and 1971,
bromacil (Hyvar(S& was listed as a "relatively non-toxic" herbicide (Anderson
et al., 1971). Atkins et al. (1973)A/ also reported that bromacil (HyvarvB/ X)
is a relatively nontoxic pesticide with a 1.20% mortality at 193.38 micro-
grams per honey bee.
Effects and Residues in the Soil
Interactions with Lower Terrestrial Organisms - Torgeson and Mee (1967)1.'
studied the microbial degradation of bromacil. In laboratory tests, soils
having no history of exposure to bromacil were treated either with 40 ppm
of bromacil in a soil perfusion system, or by mixing bromacil at rates
up to 200 Ib Al/acre. After incubation, fungi and bacteria were isolated
from the treated soil by use of a dilution plate technique. Fifty-five
I/ Tucker, R. K., and D. G. Crabtree, Handbook of Toxicity of Pesticides
to Wildlife. Bureau of Sport Fisheries and Wildlife, Denver Wildlife
Research Center, Resource Publication No. 84 (1970).
2J Pimentel, D., "Ecological Effects of Pesticides on Nontarget Species,"
Executive Office of the President, Office of Science and Technology,
Superintendent of Documents, U.S. Government Printing Office, Washington,
D.C. (1971).
3/ Anderson, L. D., E. L. Atkins Jr., H. Nakakihara and E. A. Greywood,
Toxicity of Pesticides and Other Agricultural Chemicals to Honeybees.
U.S. Department of Agriculture, Agricultural Extension Service Report,
University of California Press, Berkeley, Calif. (1971).
kj Atkins, E. L., E. A. Greywood, and R. L. Macdonald, Toxicity of Pesticides
and other Agricultural Chemical to Honeybees. U.S. Department of
Agriculture, Agricultural Extension Service Report, University of
California Press, Berkeley, Calif. (1973).
5/ Torgeson, D. C., and H. Mee, "Microbial Degradation of Bromacil,"
Northeastern Weed Control Conference Proceedings. 21:584 (1967).
41
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fungal and 73 bacterial cultures were studied in regard to their ability
to degrade bromacil by growing them in a Czapek-Dox broth containing 20
ppm of bromacil. The amount of bromacil remaining was periodically de-
termined by a bioassay technique sensitive to less than 1 ppm of bromacil,
using buckwheat as the test organism. None of the bacteria degraded
bromacil; but four of the fungi exhibited this capability. The most active
of these, Penicillium paraherquei. was studied further. No signigicant
amounts of bromacil were detectable 15 to 20 days after Czapek-Dox broth
containing 20 ppm of the herbicide had been inoculated with this fungus.
Sterile soil treated with bromacil at the rate of 3.1 Ib Al/acre
was still toxic to buckwheat after 56 days. No herbicidal effects were
detected 21 days after treatment with 6.2 Ib Al/acre, or 28 days after
treatment with 12.5 Ib Al/acre in sterile soil inoculated with I>. para-
herquei. The herbicidal effectiveness of bromacil applications at 25
and 50 Ib Al/acre was reduced to 50 and 80%, respectively, after 56 days.
In liquid and solid Czapek-Dox media, P_. paraherquei grew normally
at concentrations of bromacil up to 200 ppm. At higher concentrations
of bromacil, growth of the fungus was slower and abnormal in appearance.
The organism failed to grow in a liquid mineral salts medium containing
bromacil as the sole carbon and nitrogen source. A variant of f_. para-
herquei isolated from liquid media containing 800 to 1,000 ppm of broma-
cil appeared to be capable of growing slowly on bromacil as the sole sub-
strate.
Pancholy and Lynd (1969)—' studied the interactions between bromacil
and plants, cultures of fungi, and nitrification in the laboratory. In
Eufaula sand, bromacil reduced the growth of oat seedlings at concentra-
tions of 0.25 to 1.0 ppm, and the growth of sorghum seedlings at concen-
trations of 1.0 to 4.0 ppm. Organic matter amendments added to the sand
at rates of 1, 2, and 4 ppm significantly reduced the phytotoxicity of
bromacil to both oats and sorghum. Oats were more sensitive than sorghum;
at 0.25 ppm, the growth of sorghum was not adversely affected by bromacil.
Ten soil fungi (Aspergillus tamarii, A. niger, A. flavus, A. oryzae,
Curvularia lunata, Mucor pusillus. Trichoderma viride, Penicillium
funiculosum, £. brevicompactum. and Myrothecium verucaria) were cultured
on liquid broth media with bromacil levels of 0, 250, 500, 1,000, and
5,000 ppm for 5 days at 22 to 28°C. Bromacil up to 2,000 ppm did not in-
hibit the growth of the fungi, except A. niger, which was inhibited by
bromacil levels less than 1,500 ppm. This fungitoxic effect was par-
tially offset by increasing the inorganic nitrogen levels to 500 ppm,
and/or by 1,000 ppm of presynthesized growth factor additive (cyanoco-
balamin, yeast extract, peptone). Bromacil at 100 ppm reduced nitrifi-
cation temporarily.
I/ Pancholy, S. K., and J. Q. Lynd, "Bromacil Interactions in Plant
Bioassay, Fungi Cultures, and Nitrification," Weed Sci.. 17(4):
460-463 (1969).
42
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Wehr and Klein (1971)1/ studied the effects of bromacil and other
herbicides on Bdellovibrio bacteriovorus parasitism of a soil pseudomonad.
]5. bacteriovorus, a small endoparasitic bacterium indigenous to soil, mud
and sewage can attack and penetrate other susceptible gram-negative bacteria,
causing host lysis and release of parasite progeny into the surrounding
environment. Bromacil showed only a slight inhibition against a Bdellovibrio
strain and its Pseudomonas species host using disc assay techniques.
Using three types of soil from Puerto Rico, Liu and Cibes-Viade (1972)2J
studied the effects of bromacil and several other herbicides on the respira-
tion of soil microorganisms. At 10 ppm (equivalent to an application of
4 Ib Al/acre), most of the herbicides tested including bromacil, inhibited
oxygen consumption slightly in Goto clay soil. None of the herbicides inhibited
oxygen consumption noticeably in Fraternidad clay at 10 ppm, but at 100 ppm,
oxygen uptake was generally inhibited. In San Anton sandy loam, bromacil
and most of the other herbicides tested increased oxygen consumption at 10 ppm,
and the respiration rate at 100 ppm.
Steyn and Wolff (1969)—' investigated the influence of bromacil on the
nitrifying and respiratory capacities of soil. Sandy loam was treated with
an 80% wettable powder formulation of bromacil at the rate of 4 ppm, which
is twice the application rate recommended for this type of soil. No statis-
tically significant differences were found in the ammonium and nitrate nitrogen
contents, nor in the amounts of carbon dioxide evolved from treated as compared
to untreated soils. Those authors noted that according to the literature,
nitrification organisms are relatively sensitive to soil-applied chemicals
and are therefore useful indicator organisms. They concluded that the use of
bromacil in accordance with the specified label directions would have no
statistically significant detrimental effect on the soil microflora.
Kutches et al. (1970)A' studied the effects of bromacil and several other
pesticides on the microbial activity of sheep rumen liquor in vitro. Dry
matter disappearance, volatile fatty acid production, and alterations in
rumen ciliated protozoa numbers were the criteria measured. Relat-ively high
concentrations (500 pg/ml) of bromacil (and of the other pesticides) were
tolerated by rumen microorganisms without deleterious effects on rumen function
I/ Wehr, N., D. Klein, "Herbicide Effects on Bdellovibrio Bacteriovorus
Parasitism of a Soil Pseudomonad", Soil Biol. Biochem.. 3(2)1 143-9 (1971)
2J Liu, L. C., and H. R. Cibes-Viade, "Effect of Various Herbicides on
the Respiration of Soil Microorganisms," J. Agr. Univ. P.R.. 56(4):
417-425 (1972).
3/ Steyn, P.L., and S. W. Wolff, "The Influence of 5-Bromo-3-secondary
butyl-6-methyluracil on the Nitrifying and Respiratory Capacities
of Soil." Phytophylactica. 1:157-160 (1969).
4/ Kutches, A. J., D. C. Church, and F. L. Duryee, "lexicological Ef-
fects of Pesticides on Rumen Function In Vitro," J. Agr. Food
Chem.. 18(3):430-433 (1970).
43
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as measured by the three aforementioned parameters. The authors concluded
that the concentrations of bromacil (and of the other pesticides studied)
that might be ingested by ruminents by way of contaminated feedstuffs would
have no, or negligible, effects on rumen digestibility or other rumen
functions. Pesticide residues that might be found on contaminated feed-
stuffs would be expected to be much lower than those studied.
The reports reviewed in this subsection indicate that certain soil
microorganisms are capable of degrading bromacil, and that bromacil concen-
trations in the soil that might be expected from its use in accordance with
label directions do not appear to effect soil microflora adversely.
No reports were found on the effects of bromacil on the soil microfauna.
Laboratory Studies - Gardiner et al. (1969)i/ synthesized ^C - labeled
bromacil for disappearance and metabolism studies. This molecule
was labeled in the 2-position so that the l^C - label would be retained
by all metabolites in which the uracil ring had not been degraded. In
laboratory studies, soil samples were treated with bromacil at a rate
equivalent to 20 Ib Al/acre. Of the bromacil applied, 25.3% was decomposed
to l^C-labeled carbon dioxide in nine weeks.
Zimdahl et al. (1970) 2/ investigated the degradation of bromacil and
several other herbicides in Chehalis loam soil in the laboratory. Bromacil
was added to this soil at the rate of 8 ppm (by weight). The treated soil
was stored at two different temperatures, i.e., 13.2 and 31.2°C. The degra-
dation of bromacil followed a first order rate law with no induction period.
Evaluation of the rate constants at the two temperatures permitted calculation
(from the Arrhenius equation) of an energy of activation of 3.0 kcal/mole for
bromacil degradation. Decomposition of bromacil appeared to occur by breakage
of the carbon-halogen bond.
Dowler (1969).3/ used a cucumber bioassay test to determine the persist-
ence of soil residues of bromacil and several herbicides. Cucumber plants
were grown in steam-sterilized sand to which the herbicides were added at
concentrations ranging from 0.001 to 2.187 ppm weight. Concentrations of
bromacil as low as 0.001 to 0.027 ppm weight could be detected by this method.
This paper provides details of the bioassay method, but not persistence data.
I/ Gardiner, J. A., R. C. Rhodes, J. B. Adams Jr., and E. J. Soboczenski,
"Synthesis and Studies with 2-l^C-labeled Bromacil and Terbacil,"
J. Agr. Food Chem.. 17(5):980-986 (1969).
2J Zimdahl, R. L., V. H. Freed, M. L. Montgomery, and W. R. Furtick,
"The Degradation on Triazine and Uracil Herbicides in Soil," Weed
Res.. 10:18-26 (1970).
_3_/ Dowler, C. C., "A Cucumber Bioassay Test for the Soil Residues of
Certain Herbicides," Weed Sci., 17(3):309-310 (1969).
44
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Rhodes et al. (1970)!/ studied the mobility and adsorption of broma-
cll and several other pesticides on soils in the laboratory. 2-1*0
bromacil at concentrations ranging from 1 to 20 ppm was added to four
agricultural soils from different locations, selected to represent a
variety of soil types. Soil pH ranged from 5.4 to 6.7; organic matter
content from 0.7 to 83.5%. The Freundlich isotherm constants were de-
termined, and the mobility of the test compounds was evaluated by pre-
paring radioautograms of soil thin-layer chromatographic plates. In
each of the four different soils, bromacil was relatively more mobile
than the other four chemicals studied. Bromacil also showed greater
lateral diffusion than the less mobile materials.
Haque and Coshow (1971)2/ studied the adsorption of bromacil from
aqueous solutions onto mineral surfaces including illite, montmorillon-
ite, silica gel, humic acid, and kaolinite surfaces. Freundlich-type
Isotherms best represented the adsorption process. The humic acid
surface adsorbed considerably more chemical than other surfaces. Montmo-
rillonite and kaolinite showed a concave-type, humic acid a convex-type
adsorption. From the adsorption data at two temperatures, the isosteric
heats of adsorption in relation to the amount of chemical sorbed were
calculated. The results suggested that for most of the surfaces, the
adsorption occurs through physical forces. At very low surface coverage,
some hydrogen-bond formation was noticed.
Volk (1972)!/ studied the physicochemical aspects of the interac-
tions between bromacil (and several other pesticides) and soil. Cation
saturation and time of exposure did not appreciably affect the adsorption
of bromacil on montmorillonlte. In another test series, an aqueous solu-
tion of bromacil (0.1 meq) was titrated with 0.1 N HC1 or NaOH. No
inflection points were obtained, indicating that bromacil cannot be titrated
in an aqueous solution. However, titration in nonaqueous media indicated
that it is weakly acidic.
If Rhodes, R. C., I. J. Belasco, and H. L. Pease, "Determination of
Mobility and Adsorption of Agrichemicals on Soils," J. Agr. Food
Chem.. 18(3):524-528 (1970).
2] Haque, R., and W. R. Coshow, "Adsorption of Isocil and Bromacil
from Aqueous Solutions onto Some Mineral Surfaces," Environ. Sci.
Technol.. 5(2):139-141 (1971).
I/ Volk, V. V., "Physico-Chemical Relationships of Soil-Pesticide Inter-
actions," Oreg. State Univ. Environ. Health Sci. Cent. Annu.
Progr. Rep., pp. 186-199 (1972).
45
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Residues in Soil/Field Studies - Gardiner et al. (1969) also studied the
disappearance of 2-l^C-labeled bromacil applied at the rate of 4 Ib AI/
acre to the surface of a Butlertown silt loam. Sections of 4-in. diameter
stainless steel tubes were driven into the ground to isolate undistrubed
columns of soil. About 1.5 in. of each cylinder was left protruding above
the ground surface. The radiolabeled bromacil was applied to the soil
surface and watered into the soil with five separate rinses, which in
total were equivalent to about 0.25 in. of rain. The half-life of broma-
cil was about 5 to 6 months. After 1 year, about 75% of the total radio-
activity applied had disappeared. Bromacil constituted, about 90% of the
remaining residues, indicating that there was little accumulation of
unknown metabolites. No 5-bromouracil was formed as a metabolite, though
5-bromo-3-sec-butyl-6-hydroxymethyl uracil and a few related minor metabolites
have been identified as metabolites of bromacil in soil. Evaluation of thin-
layer chromatography radioautograms of soil extracts indicated that one
mode of degradation of bromacil proceeds through hydroxylation of the side
chain alkyl groups, presumably followed by ring opening and complete metab-
olism to carbon dioxide, ammonia, and hydrobromic acid.
Tucker and Phillips (1970)!/ studied the movement and degradation of
bromacil (and several other pesticides) in Florida citrus soil which had
been treated repeatedly with these herbicides for up to 5 years. Soil
samples were obtained from experimental plots and commercial citrus groves
from different areas in Florida. Samples were taken at depths up to 18 in.
from the middle of tree rows and kept in frozen storage until analyzed.
Bromacil content was determined by gas chromatography. From a total amount
of 100 Ib Al/acre of bromacil applied in Leon Immokalee fine sand over a
5-year period at the rate of 20 Ib Al/acre annually, approximately 1.0 Ib
AI was present in the soil (0- to 18-in. depth) 13 months after the last
application. This represents a 99% loss over the 5-year period.
Bromacil residues were found throughout the 18-in. layer of soil.
Its movement into the lower soil layers was shown to be a function of
the chemical's water solubility, its adsorption on soil colloids, and soil
type. Factors affecting soil persistence include microbial degradation,
rainfall, and the degree of uptake by plants. Bromacil is quite water soluble,
and may be leached into deeper soil layers in sandy soils. The authors
concluded that their results "preclude the possibility of any toxicity
(phytotoxicity) to citrus trees due to a buildup of bromacil in the soil
following repeated applications at recommended rates."
I/ Tucker, D. P., Jr., and R. L. Phillips, Jr., "Movement and Degrada-
tion of Herbicides in Florida Citrus Soil," Citrus Ind., 51(3):
11-13 (1970).
46
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Lange et al. (1968)i/ studied residues of bromacil and other herbi-
cides remaining in California soils following use under typical field
conditions at six locations. Bromacil, applied at 1 and 4 Ib Al/acre,
was among the most persistent of 13 herbicides tested. One year after
application, both rates were still toxic to barley, milo, sugar beets,
alfalfa, tomato, and wheat. Among these plants, alfalfa was most sensi-
tive, followed by wheat and tomato. Phytotoxicity was still evident in
the bromacil-treated plots 24 and 30 months after the initial applica-
tion. Among the 13 herbicides tested, bromacil generally lasted the
longest. At every test location, the bromacil plots were visibly obvious.
The authors point out that bromacil is a long-term, broad-spectrum soil
sterilent, and that it will find little, if any, use as a selective herbi-
cide on annual crops because of its long-lasting residual effects.
The authors do not provide disaggregate information on the properties
of the soils in which these studies were conducted. The organic matter
content of the soils ranged from 1.3 to 12.6%; sand, from 24 to 607.;
silt, from 27 to 56%; and clay, from 9 to 32%. The amount of moisture
received was approximately 30 to 45 in.
Tucker and Phillips (1970) do not provide data on rainfall, and
neither Lange et al. (1968) nor Tucker and Phillips (1970) provide data
on soil temperatures, soil pH, or other parameters that might help to
explain their seemingly divergent observations concerning the persistence
of bromacil residues.
Weber and Best (1972)!/ studied the activity and movement of broma-
cil and 12 other soil-applied herbicides as influenced by soil reaction.
Broadleaf weeds were more prevalent in neutral (pH 7) than in acid soils
(pH 5). The opposite was true for grass weeds. Bromacil was the second
\J Lange, A., B. Fischer, W. Humphrey, W. Seyman, and K. Baghott,
"Herbicide Residues in California Agricultural Soils," California
Agr.. pp. 2-4 (August 1968).
2J Weber, J. B., and J. A. Best, "Activity and Movement of 13 Soil-
Applied Herbicides as Influenced by Soil Reaction," Proc. S. Weed
Sci. Soc.. 25:403-413 (1972).
47
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most active herbicide against broadleaf weeds and was the most active against
the grass weeds. Its activity appeared to be unaffected by soil pH. When
the relative mobilities of the herbicides were measured by their movement
over the soil surface into adjacent untreated areas, bromacil was very
mobile. It also was the most persistent of all herbicides studied.
Stecko (1970)!/ studied the persistence and vertical movement of
bromacil in clay and sandy soils in field tests in Sweden. Herbicides
were applied to the surface of the test soils at 2.7, 5.3, and 10.7 Ib
Al/acre. The herbicides were not incorporated into the soil. Soil samples
were taken from six different layers ranging from 0 to 9.4 in., and the
residual toxicity was determined by bioassay with white mustard and oats.
Within 120 days after treatment, bromacil had moved downwards beyond the
9.4-in. level. Bromacil persisted longer in the sandy soil than in the clay
soil, and its phytotoxic residues disappeared more rapidly from the upper
than from the lower soil layers.
Stecko states that it is difficult to explain why bromacil disappeared
more rapidly from the clay than from the sandy soil. He suggests that
there may have been differences in the populations of microorganisms in the
two soil types. Another explanation might be that during the summer, the
microbial activity in the clay soil was inhibited due to drought.
Horowitz (1969).2/ evaluated the persistence of bromacil and nine other
herbicides in soil in the greenhouse, using an oat bioassay test. Bromacil
was applied at concentrations ranging from 0.4 to 12.8 ppm weight. Under
these conditions, bromacil was rated as "moderately persistent," its
residual activity decreased rather slowly. In general, four triazines and
bromacil were the most active among the 10 herbicides studied.
_!/ Stecko, V., Jr., "Comparison of the Persistence and the Vertical
Movement of the Soil-Applied Herbicides Simazine and Bromacil,11
10th British Weed Control Conference Proceedings, 1:303-306 (1970).
2J Horowitz, M., "Evaluation of Herbicide Persistence in Soil," Weed
Res., 9(4):314-321 (1969).
48
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The data reviewed in this subsection on the behavior and persistence
of bromacil in the soil indicated that it is not strongly adsorbed on soil
colloids. Bromacil appears to be more mobile (both laterally and verti-
cally) in the soil than most other herbicides. Bromacil residues in the
soil are moderately persistent. Microbial activity as well as nonbiological
factors appear to contribute to its degradation in the soil. In one test,
the half-life of a 4 Ib Al/acre application of bromacil was about 5 to 6
months. When applied at higher rates, the herbicidal activity of bromacil
seems to persist for two or more seasons.
Monitoring Studies - None of the published reports from the National Soils
Monitoring Program for pesticides include data on reported uses of broma-
cil, or records of detection of bromacil residues. Reports scanned in this
regard include those by Stevens et al. (1970),I/ Crockett et al, (1970)-£'
and Wiersma et al (1972) .I/
Since the results of the 1972 National Soils Monitoring Program were not
published at the time of review, data from this source is not included.
Residues in Water
A technical data sheet on bromacil (E. I. du Pont de Nemours and
Company, Wilmington, Delaware)states that the water solubility of bromacil
is 815 ppm at 25°C, and that it is stable in water and aqueous bases.
Davis and Rahn (1970)—' investigated the possible contamination of
surface water following the use of bromacil for nonselective weed control.
Surface runoffs from an industrial site treated with bromacil were collected
and analyzed by gas chromatography. Insignificant amounts of bromacil were
found in surface water from the bromacil-treated industrial site following
heavy rains within 2 to 4 weeks after application. These amounts were far
below levels reported to be injurious to animal or plant life.
No additional reports were found on the presence (or absence) of bro-
macil residues in water, sediment, or other elements of aquatic ecosystems.
i/ Stevens, L. J., C. W. Collier, and D. W. Woodham, "Monitoring Pesticides
in Soils from Areas of Regular, Limited, and No Pesticide Use,"
Pest. Monit. J.. 4(3):145-164 (1970).
2/ Crockett, A. B., G. B. Wiersma, H. Tai, W. G. Mitchell, and P. J. Sand,
"National Soils Monitoring Program for Pesticide Residues - FY 1970,"
U.S. Environmental Protection Agency, Techinical Services Division,
unpublished manuscript (1970).
3/ Wiersma, G. B., H. Tai, and P. F. Sand, "Pesticide Residue Levels in
Soils, FY 1969-National Soils Monitoring Program," Pest. Monit. J..
6(3):194-201 (1972).
4/ Davis, W. A., and E. M. Rahn, "Atrazine, Trifluralin and Bromacil in
Surface Water from Selected Agricultural and Industrial Sites,"
Northeastern Weed Control Conference Proceedings. 24:283 (1970).
49
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Residues in Air
Hill (1971)i/ reported that the rate of volatilization of bromacil
was measured for weeks at 120°F in air circulation oven. Losses were
less than 0.1%/week.
Bingetnan et al. (1962)J?/ reported that (based on tests at elevated
temperatures and with long exposures to sunlight) loss of bromacil from
soil by volatilization and photodecomposition is negligible.
Moilanen and Crosby (1974).-L/ investigated the action of sunlight
on dilute (1 to 10 ppm) aqueous solutions of bromacil. Even upon pro-
longed irradiation, only very low yields of the one detectable photo-
product (5-bromo-6-methyluracil) were obtained. The starting material
was recovered almost quantitatively. The results indicate that bromacil
is very stable toward sunlight and undergoes only N-dealkylatlon. The
slow breakdown of bromacil in sunlight indicates that photodecomposition
probably makes only a minor contribution to the environmental disappearance
of this herbicide.
No additional reports were found within the time frame allocated for
this review on the presence, fate or persistence of bromacil residues in air.
The data reviewed indicates that bromacil does not volatilize from treated
soil to any appreciable extent and that it is stable to photodecomposition
in sunlight.
Effects and Residues in Nontarget Plants
Since bromacil is primarily a broad-spectrum nonselective herbicides,
there are no "nontarget" higher plants per se. However, two noteworthy
reports were found on "nontarget" higher plants.
Sterret et al. (1972)_L/ studied antagonistic effects between bromacil
and another herbicide (picloram) on oats. It was observed that field appli-
cations of combinations of picloram and bromacil in pellet form were less
effective in controlling broomsedge (Andropogon virginicus), dallisgrass
(Paspalum dilatatum), and several panicums (Panicum sp.) than was bromacil
alone. Further experiments were conducted on oats in soil in the greenhouse
and in nutrient solution in controlled environment chambers to study this
apparent interaction. When oats were grown in soil treated with combinations
of picloram (5 or 10 Ib Al/acre) and bromacil (10 Ib Al/acre), there was less
I/ Hill, G. D., "Characteristics of Herbicides by Chemical Groups. II.
Hyvar X Bromacil," California Weed Conference Proceedings. 23:171-174
(1971).
2J Bingeman, C. W., G. D. Hill, R. W. Varner, and T. A. Weidenfeller,
North Central Weed Control Conference Proceedings. 19:42-43 (1962).
In: Herbicide Handbook of the Weed Science Society of America.
3rd ed., p. 68 (1974).
3/ Moilanen, K. W., and D. G. Crosby, "The Photodecomposition of Bromacil,"
Arch, of Environ. Contain, and Toxicol.. 2(1):3-8 (1974).
^/ Sterrett, J. P., J. T. Davis, and W. Hurtt, "Antagonistic Effects
Between Picloram and Bromacil with Oats," Weed Sci., 20(5):440-444
(1972).
50
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plant Injury than in plants treated with bromacil alone. The higher rate of
picloram in combination with bromacil resulted in an almost twofold decrease
in response as compared to plants treated with bromacil alone. In nutrient
culture experiments, it was found that the uptake of 14C-labeled bromacil
alone by oats was nearly double that of ^C-bromacil combined with picloram.
Thin-layer chromatographic analyses showed that 47% of the radioactivity from
bromacil in the oat was intact bromacil, and 70% of the labeled activity from
picloram was unaltered picloram. Roots of oats treated with picloram alone
or picloram and bromacil in combination were significantly shorter than the
roots of untreated plants, or of plants treated with bromacil alone. Reduction
of root length by picloram could be responsible for the reduction in adsorption
of bromacil.
Hiranpradit and Foy (1973)J^ found that soil applications of subtoxic
levels of bromacil (0.03 to 0.09 ppm) markedly retarded the senescence of
corn leaves. Plants treated with bromacil showed increased chlorophyll reten-
tion and incorporation. The authors point out that bromacil does not contain
a purine ring, yet it exhibited a cytokinin-like effect of retarding leaf
senescence.
Bioaccumulation, Biomagnification
There were no reports found on the possible bioaccumulation or biomag-
nification of bromacil.
Environment Transport Mechanisms
According to Hill (1971), bromacil has relatively low solubility in water
(0.08 or 815 ppm) and a K value (Freundlich constant) of 1.5 on a Keyport
silt loam. This combination of water solubility and low soil adsorption
results in considerable mobility of bromacil in soil profiles.
In a recent review, Helling et al. (1971)—' ranked a number of pesti-
cides by their relative mobility in soils by mobility classes from 1 (immobile)
to 5 (very mobile). In this scheme, bromacil was placed in Class 4. Of
82 pesticides included in this tabulation, bromacil was among the 14 materials
(mostly herbicides) rated most mobile in the soil.
This data, along with those reviewed in the preceding subsections,
indicate that bromacil is relatively stable in the soil, subject to leaching
and surface transport via runoff, not strongly adsorbed on soil solids,
and not subject to significant volatization from treated soil.
JL/ Hiranpradit, H., and C. L. Foy, "Retardation of Leaf Senescence in
Maize by Subtoxic Levels of Bromacil, Fluometuron, and Atrazine,"
Botanical Gazette. 134(1):26-31 (1973).
2] Helling, C. S., P. C. Kearney, and M. Alexander, "Behavior of Pesti-
cides in Soils," Advances in Agronomy. 23:147-240(1971).
51
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References
Anderson, L. D., E. L. Atkins Jr., H. Nakakihara, and E. A. Greywood, Toxicity
of Pesticides and Other Agricultural Chemicals to Honeybees. U. S. Department
of Agriculture, Agricultural Extension Service Report, University of Calif-
ornia Press, Berkeley, Calif. (1971).
Atkins, E. L., E. A. Greywood, and R. L. Macdonald, Toxicity of Pesticides and
Other Agricultural Chemical to Honeybees. U. S. Department of Agriculture,
Agricultural Extension Service Report, University of California Press, Berkeley,
Calif. (1973).
Bingeman, C. W., G. D. Hill, R. W. Varner, and T. A. Weidenfeller, North
Central Weed Control Conference Proceedings. 19:42-43 (1962). In:
Herbicide Handbook of the Weed Science Society of America, 3rd ed.,
p. 68 (1974).
Crockett, A. B., G. B. Wiersma, H. Tai, W. G. Mitchell, and P. J. Sand,
"National Soils Monitoring Program for Pesticide Residues - FY 1970,"
U.S. Environmental Protection Agency, Technical Services Division,
unpublished manuscript (1970).
Davis, W. A., and E. M. Rahn, "Atrazine, Trifluralin and Bromacil in
Surface Water from Selected Agricultural and Industrial Sites," North-
eastern Weed Control Conference Proceedings, 24:283 (1970).
Dowler, C. C., "A Cucumber Bioassay Test for the Soil Residues of Cer-
tain Herbicides," Weed_§£ii, 17(3):309-310 (1969).
E. I. du Pont de Nemours and Company, Inc., Personal communication (1974).
Gardiner, J. A., R. C. Rhodes, J. B. Adams, Jr., and E. J. Soboczenski,
"Synthesis and Studies with 2-lAC-Labeled Bromacil and Terbacil," J^
Agr. Food Chem.. 17(5):980-986 (1969).
Haque, R., and W. R. Coshow, "Adsorption of Isocil and Bromacil from
Aqueous Solution onto Some Mineral Surfaces," Environ. Sci. Techno1.,
5(2):139-141 (1971).
Helling, C. S., P. C. Kearney, and M. Alexander, "Behavior of Pesticides
in Soils," Advances in Agronomy. 23:147-240 (1971).
Hill, G. D., "Characteristics of Herbicides by Chemical Groups. II.
Hyvar X Bromacil," California Weed Conference Proceedings, 23:171-174
(197n-
Hiranpradit, H., and C. L. Foy, "Retardation of Leaf Senescence in Maize
by Subtoxic Levels of Bromacil, Fluometuron, and Atrazine," Botanical
Gazette. 134(1):26-31 (1973).
52
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Hoffman, C, E., "The Mode of Action of Bromacil and Related Uracils,"
Second International Conference of Pesticide Chemical Proceedings.
(1971). In: Ashton and Crafts, Mode of Action of Herbicides. John
Wiley & Sons, pp. 430-431 (1973).
Horowitz, M., "Evaluation of Herbicide Persistence in Soil." Weed Res,,
9(4):314-321 (1969).
Kutches, A. J., D. C. Church, and F. L. Duryee, 'lexicological Effects
of Pesticides on Rumen Function In Vitro.11 J. Agr. Food Chem. t 18(3):
430-433 (1970).
Lange, A., B. Fischer, W. Humphrey, W. Seyman, and K. Baghott, "Herbi-
cide Residues in California Agricultural Soils," California Agr.,
pp. 2-4 (August 1968).
Liu, L. C., and H. R. Cibes-Viade, "Effect of Various Herbicides on the
Respiration of Soil Microorganisms." J. Agr. Univ. P.R.. 56(4):417-
425 (1972).
Moilanen, K. W., and D. G. Crosby, "The Photodecomposition of Bromacil,"
Arch, of Environ. Contain, and Toxicol.. 2(1):3-8 (1974).
Pancholy, S. K., and J. Q. Lynd, "Bromacil Interactions in Plant Bio-
assay, Fungi Cultures, and Nitrification," Weed Sci.. 17(4):460-463
(1969).
Pimentel, D., "Ecological Effects of Pesticides on Nontarget Species,"
Executive Office of the President, Office of Science and Technology,
Superintendent of Documents, U.S. Government Printing Office,
Washington, D.C. (1971).
Rhodes, R. C., I. J. Belasco, and H. L. Pease, "Determination of Mobility
and Adsorption of Agrichemicals on Soils," J, Agr. Food Chem., 18(3):
524-528 (1970).
Stecko, V., Jr., "Comparison of the Persistence and the Vertical Movement
of the Soil-Applied Herbicides Simazine and Bromacil," 10th British Weed
Control Conference Proceedings. 1:303-306 (1970).
Sterrett, J. P., J. T. Davis, and W. Hurtt, "Antagonistic Effects Between
Picloram and Bromacil with Oats," Weed Sci. 20(5):440-444 (1972).
Stevens, L. J., C. W. Collier, and D. W. Woodham, "Monitoring Pesticides
in Soils from Areas of Regular, Limited, and No Pesticide Use," Pest.
Monit. J.. 4(3):145-164 (1970).
53
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Steyn, P. L., and S. W. Wolff, "The Influence of 5-Bromo-3-secondary-
butyl-6-methyluracil on the Nitrifying and Respiratory Capacities of
Soil," Phytophylactica. 1:157-160 (1969).
Torgeson, D. C., and H. Mee, "Microbial Degradation of Bromacil," North-
eastern Weed Control Conference Proceedings, 21:584 (1967).
Tucker, D. P., Jr., and R. L. Phillips, Jr., "Movement and Degradation
of Herbicides in Florida Citrus Soil," Citrus Ind.. 51 (3):11-13 (1970).
Tucker, R. K., and D. G. Crabtree, Handbook of Toxicity of Pesticides to
Wildlife. Bureau of Sport Fisheries and Wildlife, Denver Wildlife
Research Center, Resource Publication No. 84 (1970).
Volk, V. V., "Physico-chemical Relationships of Soil-Pesticide Interac-
tions," Oreg. State Univ. Environ. Health Sci. Cent. Annu. Progr. Rep..
pp. 186-199 (1972).
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(1971).
Wiersma, G. B., H. Tai, and P. F. Sand, "Pesticide Residue Levels in
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6(3):194-201 (1972).
Yoshida, K., and Y. Nishiuchi, "Toxicity of Pesticides to Some Water
Organism," Bull, of Agr. & Chem Inspect. Stn. (Tokyo) 12:122-128 (1972)
Zimdahl, R. L., V. H. Freed, M. L. Montgomery, and W. R. Furtick, "The
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54
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SUBPART II. D. PRODUCTION AND USE
CONTENTS
Page
Registered Uses of Bromacil 56
Federally Registered Uses 56
State Regulations 57
Production and Domestic Supply 57
Volume of Production 57
Imports 61
Exports 61
Domestic Supply 62
Formulations 62
Use Patterns of Bromacil in the United States 63
General 63
Agricultural Uses of Bromacil 63
Nonagricultural Uses of Bromacil 65
Bromacil Uses in California 65
References . 75
55
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This section contains data on the registered uses, and on the pro-
duction, domestic supply, and use patterns of bromacll. The section
summarizes rather than interprets scientific data reviewed.
Registered Uses of Bromacil
Federally Registered Uses - Bromacil is a broad-spectrum general herbi-
cide. It controls a wide range of annual and perennial grasses and
broadleaf weeds. Annual weeds are controlled at lower rates, perennial
weeds (including grasses) and brush at higher rates.
Bromacil is registered and reconmended for nonselective weed and
brush control on noncropland, and for selective weed control on a few
crops.
Commercially available bromacil formulations are discussed below
in the subsection on production and domestic supply.
Bromacil is currently registered in the United States for the fol-
lowing major uses:
1. Nonselective weed and brush control on noncropland areas including
railroad, highway and pipeline right-of-ways; petrochemical tanks;
lumber yards; storage areas; industrial plant sites; and drainage
ditches using the following applications, as found on registered
use labels:
a. 2.4 to 4.8 Ib Al/acre for the control of annual weeds and
grasses;
b. 5.6 to 9.6 Ib Al/acre for the control of perennial weeds and
grasses;
c. 12.0 to 24.0 Ib Al/acre for the control of Johnson grass and
other hard-to-kill perennial weeds and grasses;
d. 5.6 to 24.0 Ib Al/acre (broadcast treatment) for the control
of undesirable woody plants (rate of application dependent
upon suspectibility of target brush and soil adsorptivity;
higher rates required on adsorptive soils);
e. 2.0 Ib AI in 5 gal. of water for basal (spot) treatment, to be
applied at the rate of 1 to 2 fluid ounces/stem, 2 to 4 in. in
basal diameter.
2. Selective weed control in crops using the following applications:—'
a. 1.6 to 6.4 Ib Al/acre for the control of annual and perennial
weeds in citrus plantings (oranges, grapefruit, lemons), to be
applied as a band or broadcast treatment beneath and/or between
trees, lower rates for the control of annual weeds and on light
soils; higher rates against perennial weeds, especially grasses,
and on silt and clay loams. Do not plant treated areas to any
crop within two years of last treatment.
T7U.S. Environmental Protection Agency, EPA Compendium of Registered
Pesticides. Vol. I (1970).
56
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b. 1.6 to 4.8 Ib Al/acre (restricted to Hawaii) for the control of
seedling weeds In pineapple, for broadcast application immediately
after planting and before the planting material begins to grow.
A second application of 1.6 Ib Al/acre may be made prior to
differentiation, If needed, as a directed interline spray. Do not
replant to any crop other than pineapple within two years of last
application.
c. 0.6 to 3.2 Ib Al/acre (restricted to Puerto Rico) at planting time
is recommended on pineapple. Single overall application immedi-
ately after planting. Do not replant to any crop other than
pineapple within two years of last application.
For further details on these registered uses of bromacil, including
necessary use precautions, specific weeds controlled at different rates,
retreatment, moisture requirements, type and duration of efficacy, and
other directions to users see Table 5, illustrating a commercial label
for bromacil 802 wettable powder (Trademark: Hyvar^X).
Registered uses of bromacil on crops (i.e., citrus and pineapple),
established tolerances, dosage rates, and use limitations are tabulated
in the EPA Compendium of Registered Pesticides. Tolerances established
for bromacil residues on raw agricultural commodities are recorded in the
Code of Federal Regulations Jy
Bromacil is also registered and recommended for use in combination
with diuron. Two wettable powder formulations containing different ratios
of these two herbicides are commercially available under the trademark
"Krovar." These products are registered and used for the same weed con-
trol purposes as formulations containing only bromacil.
State Regulations - In a number of states, the sale and use of pesticides
is subject to state pesticide laws and regulations, in addition to Federal
laws and regulations. For instance, in the State of California, 42 spe-
cific pesticides have been designated as "injurious or restricted materi-
als." The use of pesticides in this category is subject to special re-
strictions under regulations administered by the California State Department
of Agriculture. Bromacil has not been designated as an "Injurious or re-
stricted" pesticide. As far as could be determined, bromacil is not subject
to intrastate use restrictions in any state.
Production and Domestic Supply
Volume of Production - Accordii
and 1973 final reports!/ on synthetic organic chemicals, there has been
Volume of Production - According to United States Tariff Commission's 1972
si/ on (
T7Code of Federal Regulations. "USDA Summary of Registered Agricultural
Pesticide Uses," (Vol. I, 1970), Title 40, Part 180-210, p. 22.
2J U.S. Tariff Commission, Synthetic Organic Chemicals. U.S. Production
and Sales. T. C. Publication 681 (1972, 1973).
57
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Table 5. BROMACIL 807. WETTABLE POWDER
(HWAR® X) LABEL
V.to observe the following: Do not apply (exeep ,.,,,„„„. ... ,
equipment on or near desirable trees or other plant}, eronl Mitt whsra their roots may <
In Ittiitloiw where the chemical may be washet^jOfInured Wp(pr.Ud tottHtyelr —'
•use cr. lawns, walks, driveways, tennis wurto, of ilmflar attj»$. P.«yent,drfftof < —,..,..
i j spray to desirable plnrrts. Do not contaminate; » tracos'of, "HyVar", X fronj applfcatjoi:
E. I. cfy Pont de
[ Biochemlcals DepartrhehtVVIlrnl
Source: Label for HYVAR*'X bromacil weed killer 807. wettable
powder, 4-lb bag, EPA Registration No. 352-287.
58
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Table 5. (Continued)
NON-CROP USE
WEED CONTROL
To control most w»edi lor in extended period of lima on non-cropland area* fuch as RAILROAD, HIGH-
WAY and PIPELINE RIGHT OFAVAYS. PETROLEUM TANK FARMS. LUMBERYARDS. STORAGE AREAS and
INDUSTRIAL PLANT SITES: l
Apply 3 to C Ibs. per acr* to control ANNUAL WEEDS and GRASSES such » foxtail, ryegrats. wild oats,
crabgrass. cheatgrass. bromegrass. ragweed, lambsquarters. puncturevine and turkey mullein. When applied
fust prior to or attar •mergence of annuals, rain ai low ai 2 Ibs. par acre control many annual weeds and
(raises In low rainfall areas and give short-term control In higher rainfall areas.
Apply 7 to 12 Ibs. per acre to control PERENNIAL WEEDS and GRASSES such as smooth brome. Bahla-
grass, bluegrass, redtop. purpletop. quackgrass, broomsedge, aster, dandelion, dog fennel, goldenrod.
plantain and wild carrot. In areas with low or seasonal rainfall, rates as low as 5 Ibs. per acre control many
perennial weeds and grasses.
Apply IS to 30 Ibs. per acre to control JOHNSONGRASS; use at the same rate for OTHER HARD-TO-
KILL PERENNIAL WEEDS and GRASSES such as Bermudagrass, Dallisgrass, nutgrass. vaseygrass, salt-
grass, bouncingbet, dogbane, bracken fern and horsetail. Where limited rainfall (usually less than 4 inches)
occurs during the active growth period, such as some areas of Ihe West, "Hyvar" X usually will not provide
satisfactory control of hard-to-kill, deep-rooted perennial weeds such as Johnsongrass.
Hole-Use the higher levels of the dosage ranges on adsorptive soils (those high in organic matter or carbon).
Retnetment-Apply 2 to 6 Ibs. per acre when annual weeds and grasses reappeer on sites where weed
growth has been controlled.
For Small Anus-V* cupful of "Hyvar" X per 250 sq. ft. Is approximately IS Ibs. per acre.
BRUSH CONTROL
To control undesirable woody plants on non-cropland areas such as RAILROAD RIGHT-OF-WAYS, STORAGE
AREAS. INDUSTRIAL PLANT SITES, and DRAINAGE DITCHES:
Apply In spring or summer as a broadcast or basal (spot) treatment; for use on drainage ditches, apply
•s a basal (spot) treatment only. Note: For effective brush control and prevention of damage to desirable
vegetation: do not apply to brush standing In water; do not use water from treated ditches for irrigation;
do not use in Irrigation ditches nor on right-of-ways or other sites where marketable timber or other
desirable trees or shrubs are immediately adjacent to the treated area.
Broadcast Treatment-Apply 7 to 12 Ibs. per acre to control oak, willow, sweet gum, and pine; apply 15
to 30 Ibs. per acre to control brush such as American elm, winged elm. haekberry, sumac, and cotton-
wood. Use the higher levels of the dosage ranges on adsorptive soils (those high in organic matter or carbon).
Basal (Spot) Treatment-Mix 2V, Ibs. in 5 gals, of water and apply at the rate of I to 2 fl. oz. per stem 2"
to 4" In basal diameter; wet base of stem to run-off. Treatment controls woody plants such as cottonwood,
haekberry. maple, oak. poplar, red bud. sweet gum. wild cherry, willow, and winged elm.
SELECTIVE USE IN CROPS i
"Hyvar" X should be used only in accordance with recommendations on this label, or in separate
Du Pont bulletins available through local dealers.
All dosages of "Hyvar" X are expressed as broadcast rates. For band treatment, use proportionately less;
for example, use H of the broadcast rate when band treating V> of the area.
Moisture is necessary to activate the chemical; best results are obtained if moisture is supplied by rainfall
or irrigation within two weeks after application.
CITRUS (Oranges, Grapefruit, Umons)
Apply as a band or broadcast treatment beneath and/or between trees. Avoid contact of foliage and fruit
with spray or mist. Temporary yellowing of citrus leaves may occur fallowing treatment.
Because Injury to citrus trees may result: do not use on soils low in organic matter (less than 1%) nor on
poorly drained soils; do not apply more than 8 Ibs. per acre per yean do not treat trees planted in Irriga-
tion furrows: do not treat diseased trees such as those with foot rot. Do not use in citrus orchards inter-
planted with other trees or desirable plants, nor m home citrus plantings or in areas where roots of other
valuable plants or trees may extend as plant injury may result. Treated areas may be planted to citrus
trees one year after last application; do not replant to other crops within 2 years after last application as
plant injury may result.
Trees Established for Four Years or More
Annual Weedt-lncluding crsbgrass. crowfoot. Coloradograss. natalgrass (red top), barnyardgrass (water-
grass), sandspur. purslane. Florida pusley. sprangietop, puneturevme. mustard, lambsquarters. henbit,
annual sedge and turkey mullein, apply 2 to 4 Ibt per acre. Apply anytime ol the year, preferably shortly
before or after weed growth begins when adequate moisture is available.
Perennial Weeds-Best results are obtained if application is made shortly before or shortly after weed
growth begins: if dense growth is present, remove lops and spray the ground. Effects on perennial weeds
are slow to appear, usually progressing over a period of several months.
Make a single application per year during the period from winter to early summer; use at the following rates:
20" J»f» Uw. "Hyvar" X Per Acre
Sand, loamy sand 4 to 5
Sandy loam 5 to 6
Silt team, day loam 6 to 8
Alternatively, make two applications of 3 to 4 Ibs. "Hyvar" X per acre per year, lii Florida, Tent, and
Louisiana, apply in spring and summer, in California and Arizona, apply in tell and soring.
59
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Table 5. (Continued)
NeU— Partial control usually occur* with •
single treatment; repeat applications art re-
quired to control perennials. "Hyvar" X con-
trols the following:
Bermudagrass All areas U.S.
Torpedograss. paragrass.
pangolagrass,
Bahiagrass Florida
Johnsongrass Texas
Nutsedge Texas. California
Control of perennials may be Improved by cul-
tivation prior to treatment: otherwise, avoid
working the soil as long as weed control con-
tinues or else effectiveness of the treatment
may be reduced.
Torpedogftss Control-Barrier Strip Treatment
For control of torpedograss adjacent to citrus
graves to prevent spread of the weed Into
groves, apply 30 IDS. per acre. Treat a border
strip 10 to 20 ft wide adjacent to the citrus
grove, but not closer than 10 ft. to the drip-
line of citrus trees. Examine treated area
every four months after application and spot-
treat Invading or surviving torpedograss at
30 IDS. per acre (11 oz. per 1000 sq. ft.). For
best result* apply in late winter or early spring
after the torpedograss has broken dormancy
and Is actively growing. For later season
application where growth Is rank, mow or
disc the area prior to treatment.
PINEAPPLE
Do not replant treated areas to any crop
other than pineapple within 2 years after last
application as injury to subsequent crops
may result.
Hawall-For control of seedling weeds such as
crabgrass, wiregrass, foxtail, chloris. Hlaloa,
Flora's paintbrush, balsam apple and Amar-
•nthus, apply 2 to 6 Ibs. per acre broadcast
Immediately after planting and before the
planting material begins to grow. Use the
lower rates in low rainfall areas (5 to 10
Inches annually) and on clean-culture fields;
use the higher rates in high rainfall areas
(above 10 inches annually) and for trash-
mulch fields. An additional application of
2 Ibs. per acre may be made prior to dif-
ferentiation, if needed, as a directed interline
•pray. Do not spray over top of plants.
Puerto Rlco-For control of seedling weeds
such as crabgrass. goosegrass, jungle rice,
pigweed, and purslane, apply 2 to 4 Ibs. per
acre broadcast immediately after planting
and before planting material begins to grow.
NOTICE TO BUYER
Seller warrants that this product conforms
to the chemical description on the label thereof
and is reasonably fit for purposes stated on
such label only when used in accordance with
directions under normal use conditions. This
warranty does not extend to use of this prod-
uct contrary to label use directions, or under
abnormal use conditions, or under condi-
tions not reasonably foreseeable to seller;
buyer assumes all risk of any such use. Seller
makes no other warranties, express or implied.
Made in U.S.A. Printed In U.S.A.
GENERAL INFORMATION
Du Pont "Hyvar" X Bromadl Weed Killer Is a
wettable powder to be mixed in water and
applied as a spray for control of weeds and
brush. It I* non-corrosive to equipment, non-
flammable and non-volatile.
"Hyvar' X Is an effective general herbicide for
the control of many annual weeds at low rates
and perennial weeds and brush at higher rates
and Is particularly useful for control of peren-
nial grasses. It may be used on non-cropland
for non-selective weed and brush control and
for selective weed control In certain crops.
Effects are stow to appear and may not become
apparent until the chemical has bean carried
Into the root zone of the weeds by moisture.
The degree of control and duration of affect
will vary with the amount of herbicide applied.
soil type, rainfall, and other conditions.
DIRECTIONS
Apply "Hyvar" X as a spray just before or dur-
ing the period of active growth of plants to be
controlled. If dense growth is present, results
will be Improved If vegetation Is removed bat ore
treatment. Do not apply when ground Is frozen.
Before spraying, calibrate equipment to deter-
mine quantity of water necessary to uniformly
cover measured area to be treated. Weigh the
proper amount of "Hyvar" X and mix Into
necessary volume of water.
For crop use, apply with a fixed-boom power
sprayer property calibrated to a constant spaed
and rate of delivery. For calibration instruc-
tions, see Du Pont Bulletin, "Instructions for
Applying Du Pont Weed Killers for Selective
Weed Control In Crops". Use sufficient water
(min. 40 gals, per acre) to provide thorough
and uniform coverage of the ground. Spray
booms must be shut off while starting, turn-
ing, slowing or stopping, or Injury to the crop
or successive crops may result.
For non-crop use, application also may be made
with a hand-gun sprayer using at least 200
gals, spray per acre to Insure uniform cover-
age. For small areas, a hand sprayer or sprink-
ling can may be used.
Nozzle screens should be 50 mesh or larger.
Continuous agitation In the spray tank is re-
quired to keep the material in suspension.
Agitate by mechanical or hydraulic means In
the spray tank. If by-pass or return line Is
used, it should terminate at bottom of tank
to minimize foaming. Do not use air agitation.
60
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one major producer of bromacil in the United States, du Pont. The
moat recent issues of the Farm Chemicals Handbook!/ (1973, 1974)
list only du Font as basic producer of bromacil.
In the Tariff Commission pesticide reports, the production and
sale volumes of bromacil are not reported individually. Bromacil is
included in a large category "all other cyclic herbicides and plant
hormones" which includes, in addition to bromacil, all other cyclic
herbicides and plant hormones except maleic hydrazide and the dimethy-
lamine salt of 2,4-D. This group includes such large-volume herbicides
as: atrazine and other triazines; 2,4-D acid, esters, and salts;
amiben esters and salts; trifluralin; dimethylurea compounds; and many
other specified and unspecified herbicides. The reported production
volumes for this composite category was 344,789,000 Ib AI in 1972 and
357,310,000 Ib in 1973.
In comparison to many other herbicides in this category, the pro-
duction and sales volume of bromacil is so small that it is difficult
to make quantitative estimates on bromacil. However, based on studies
by Midwest Research Institute and R.V.R. Consultants!./ it is estimated
that in 1972, the volume of production of bromacil in the U. S. was
approximately 4 million pounds AI.
Imports - Imports of pesticides that are classified as benzenoid chemicals
(this group includes bromacil) are reported in a U.S. Tariff Commission
annual report .27
According to the report there were no imports of bromacil into the
United States in 1972.
Exports - Pesticide exports are reported in a Bureau of the Census annual
report.
Technical (unf emulated) bromacil is cited in the report .A/ In
addition to bromacil, a number of other specified synthetic organic her-
bicide active ingredients are included.
Farm Chemicals Handbook. Meister Publishing Co., Willoughby, Ohio,
1973, 1974.
von Rumker, R., E. W. Lawless, and A. F. Meiners, "Production, Distri-
bution, Use and Environmental Impact Potential of Selected Pesticides,"
Final Report, Contract No. EQC-311, for Council on Environmental
Quality, Washington, D. C. (1974).
U. S. Tariff Commission, Imports of benzenoid Chemicals and Products.
T.C. Publication 601, (1973).
U. S. Bureau of the Census, U. S. Exports. Schedule B. Commodity by
Country. Section 512.0629, Report FT 410.
61
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Formulations of bromacil are also Included.—' In addition to several
specified bromacil-containing formulations, a number of other formulated
herbicides are included.
Total exports of herbicides for 1972 were reported as 34,796,185 Ib
for technical herbicides and 38,967,237 Ib for herbicidal preparations.
The Foreign Trade Division reports indicate that both technical and
formulated bromacil are being exported from the United States. However,
bromacil exports represent only a small share of the total volume of ex-
port of technical and formulated herbicides, respectively. Therefore, the
export statistics provide only minimal help in estimating the export volume
of bromacil. However, based on information obtained from pesticide trade
sources and overseas pesticide markets, it is estimated that the 1972
export volume of bromacil was 0.5 to 1.0 million pounds AI, probably closer
to 1.0 million pounds AI.
Domestic Supply - Subtracting estimated exports from estimated total pro-
duction and assuming no imports, it is estimated that about 3 million pounds
of bromacil AI were used domestically in 1972.
A comparable estimate for 1973 cannot be made at this time because
all necessary U.S. Tariff Commission and Bureau of the Census Pesticide
Reports for 1973 were not available at the time of review.
Formulations - The following bromacil formulations are commercially available
in the United States:
1. Hyvar ® X bromacil weed killer, a wettable powder containing 80%
bromacil.
2. Hyvar ® X-L bromacil weed killer, a water soluble-liquid containing
2 Ib bromacil per gallon (present as lithium salt).
3. Hyvar ® X-P brush killer, pellets containing 10% bromacil.
4. Krovar ® I weed killer, a wettable powder containing 40% bromacil
and 40% diuron.
5. Krovar ® II weed killer, a wettable powder containing 53% bromacil
and 27% diuron.
In addition, formulators offer combination formulations containing bromacil,
including the following:
1. 1.5% bromacil + 66.5% sodium metaborate tetrahydrate + 30.0 %
sodium chlorate (UreaborUv), applicable in dry form or as an
aqueous spray.
\J U. S. Bureau of the Census, U. S. Exports, Schedule B. Commodity
by Country. Section 599,2080, Report FT 410.
62
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2. 4.0% bromacil + 64.0% sodium metaborate tetrahydrate + 30.0%
sodium chlorate (Hibor®), applicable in dry form or as an
aqueous spray.
3. 4.0% bromacil + 94.0% sodium metaborate tetrahydrate
applicable in dry form or as an aqueous spray.
Use Patterns of Bromacil in the United States
General - As discussed in the subsection on the registered uses of
bromacil in the United States, this product is a broad-spectrum herbicide
for nonselective control of many annual and perennial grasses and broad-
leaf weeds, including brush, on noncropland; and (at lower rates of appl-
ication) for selective control of annual and perennial weeds in citrus
groves, and for the control of seedling weeds in pineapple, Bromacil is
primarily an Industrial herbicide; agricultural uses comprise only 10 to
15% of its estimated domestic consumption.
The herbicidal potential of bromacil was first recognized and described
in the early 1960's. Bromacil has been in commercial use in the United
States since the mid-1960's, and its use volume appears to be still on the
increase. Data on the uses of bromacil by industrial, commercial and
institutional organizations, and by government agencies was obtained by the
Midwest Research Institute (von Rumker et al., 1974). In the same project,
RvR Consultants obtained information on the farm uses of bromacil from the
following sources:
1. Survey of the Federal/State Cooperative Extension Services in all
50 states and in Puerto Rico (conducted in 1973);
2. Analyses of state pesticide use recommendations;
3. Pesticide use reports from the states of Arizona and California;
4. Data on pesticide uses supplied by the EPA Community Pesticide
Studies Project in Arizona, Hawaii and Texas;
5. Estimates and information obtained from basic producers of bro-
macil and other pesticides, and from pesticide trade sources;
6. Agricultural Statistics, an annual publication of the U.S.
Department of Agriculture.
Information on the uses of bromacil from all of these sources were
utilized in arriving at the estimates summarized in Table 6 and discussed
below.
Agricultural Uses of Bromacil - Midwest Research Institute estimates that in
1972 about 400,000 Ib of bromacil AI were used for agricultural purposes in the
U.S., primarily in the Southwestern states for weed control in citrus groves
63
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Table 6. ESTIMATED USES OF BROM&CIL IN THE U.S.
BY REGIONS AND CATEGORIES, 1972
Category
Region
Agri-
culture
Industrial/
commercial
Sub-
totals
Government
agencies^'
Home
and
garden
Total,
all
categories
Northeast^/
Southeast^,/
North central^/
South central—'
Northwest6./
Southwest!/
Total, all regions
40
Neglected
360
400
200
500
400
800
200
200
2,300
(Thousands of pounds AI)
200
540
400
800
200
560
2,700
300
None
200
540
400
800
200
560
3,000
al New England States, New York, New Jersey, Pennsylvania.
b/ Maryland, Delaware, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida.
£/ Ohio, Indiana, Illinois, Michigan, Wisconsin, Minnesota, Iowa, Missouri, North Dakota, South
Dakota, Nebraska, Kansas.
d/ Kentucky, Tennessee, Arkansas, Louisiana, Mississippi, Alabama, Oklahoma, Texas.
e/ Montana, Idaho, Wyoming, Colorado, Utah, Washington, Oregon, Alaska.
f/ New Mexico, Nevada, Arizona, California, Hawaii.
&/ No regional breakdown available.
Sources: MRI-RvR estimates. See text.
-------
and in pineapple fields in Hawaii. It is also estimated that a small quantity
of bromacil (approximately 40,000 Ib) was used on the same crops in the South-
eastern states and in Puerto Rico, and an even smaller amount on citrus in Texas.
There were no other major agricultural uses of bromacil in the United
States in 1972. However, California data suggests other uses.
Nonagricultural Uses of Bromacil - It is estimated that in 1972 about 2,300,000
Ib of bromacil AI were used by industrial and commercial organizations, and
about 300,000 Ib by government agencies. Bromacil is not registered or rec-
ommended for any home garden uses.
In the industrial/commercial weed control sector, the largest quan-
tity of bromacil, about 800,000 Ib, was used in the South Central states
in 1972; followed by the Southeastern states, 500,000 Ib; the North Central
states, 400,000 Ib; and the Northeastern, Northwestern, and Southwestern
states, about 200,000 Ib each. This estimated distribution pattern corre-
sponds largely to the length and intensity of weed infestation pressure
on noncropland areas as determined primarily be the climate in these
regions.
Government agencies, including federal,, state, county, and local
government units, highway departments, etc., used an. estimated 300,000
Ib of bromacil in 1972 nationwide. No regional breakdown is available
for this estimate.
Thus, considering all domestic uses of bromacil combined (Table 6),
Midwest Research Institute estimates indicate that slightly more than 25%
of the total quantity used in 1972 was used in the South Central states;
about 13% in the North Central states; the balance (less than 10% each) in
the Northeastern and Northwestern states.
Bromacil Uses in California - The State keeps detailed records of pesticide
uses by crops and commodities. These reports are published quarterly and
summarized annually. Table 7 summarizes the uses of bromacil in California
by major crops and other uses for the 4-year period 1970 to 1973.
In California, bromacil is not subject to the special restrictions
and reporting requirements imposed upon the sale and use of pesticides
designated as "injurious or restricted materials." For this reason, the
percentage of bromacil use reported to the State Department of Agricul-
65
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Table 7. BROMACIL USES IN CALIFORNIA BY MAJOR
CROPS AND OTHER USES, 1970-1973
Crop/use
1973
Year
1972
1971
1970
Citrus
Other fruit and
nut crops—
Vegetable and
field crops—'
All other uses—'
Total, all uses
(Thousands of pounds AI)
16.3 20.7 16.4
0.4
0.6
64.9
82.2
0.6
0.4
131.5
153.2
0.3
0.4
48.0
65.1
9.4
Neglected
None
79.6
89.0
a/ Includes almonds, avocados, grapes, plums, nectarines, peaches,
strawberries (bromacil not registered or recommended for use
on any of these crops).
b/ Includes cauliflower, broccoli, melons, corn, cucumbers, lettuce,
potatoes, tomatoes, cotton, alfalfa (bromacil not registered
or recommended for use on any of these crops).
£/ Includes Federal, state, county and city agencies; the University
of California; irrigation, flood control, water resource, and
vector control districts or agencies; school districts: resi-
dential, structural and turf uses; and uses on industrial and
other nonagricultural areas.
Source: California Department of Agriculture, Pesticide
Use Reports for 1970, 1971, 1972 and 1973.
66
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ture (and included in its statistics) is probably lower than the percent-
age for restricted use pesticides. However, the State Department of
Agriculture and others familiar with pesticides uses in California be-
lieve that the department's statistics do include a high percentage of
the actual uses of nonrestricted pesticides, and that these statistics
are representative of the use patterns by crops and other uses in
California.
According to the California State Pesticide Use Reports (Table 7),
the use of bromacil in California for all purposes varied between 65,100
Ib in 1971 and 153,200 Ib in 1972, with the quantities used in 1970 and
1973 within that range.
The use of bromacil on citrus fruits during this period varied from
a low of 9,400 Ib in 1970 to a high of 20,700 Ib in 1972.
In each of the 4 years covered in Table 7, the largest share of the
total bromacil volume used in California (about 75 to 907.) was used by
Federal, state, county, and city agencies; irrigation, flood control,
water, and vector control districts and agencies; school districts; and
for weed control on industrial and other nonagricultural sites.
Tables 8 and 9 present the bromacil uses in California by crops and
other uses, number of applications, pounds AI, and numbers of acres treated,
for 1972 and 1973, the two most recent years for which data is avail-
able. These tables provide a detailed breakdown of the bromacil uses
summarized in Table 7 for the years 1972 and 1973.
67
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Table 8. USE OF BROMACIL IN CALIFORNIA IN 1972 BY CROPS AND OTHER USES,
APPLICATIONS, QUANTITIES, AND ACRES TREATED
Commodity
Alfalfa
Almond
Avocado
Cauliflower
Citron, melon
Citrus
City agency
Corn--sweet
County agricultural commissioner
County or city parks
County road
Crucifer
Cucumber or pickle
Federal agency
Fallow (open ground)
Flood control
Grapefruit
Grape
Industrial areas
Irrigation district
Lemon
Lettuce/head
Lime
Nonagricultural areas
Orange
Other agencies
Plum
Potato
Reclamation district
Residential control
School district
Soil (fumigation only)
State highway
Structural control
Tangelo
Tomato
Turf
University of California
Vector control
Water areas
Water resources
Applications^/
1
1
4
1
1
129
1
1 CR
2
8
20
3
2
94
15
2
132
327
1
5
1
1
11
2
46
Lb
13.33
117.60
411.20
2.40
42.90
4,185.46
1,541.15
15.10
6,222.26
69.60
4,827.87
57.60
6.70
146.90
115.82
2,933.30
408.57
46.20
25.60
3,347.44
5,498.03
76.50
14.40
4,087.49
10,584.68
93,018.93
1.60
64.02
52.00
3,546.75
45.38
14.40
1,124.40
34.00
16.00
122.19
13.40
739.20
1,164.87
1,907.80
5,608.08
Acres
100.00
49.00
136.00
6.00
5.50
2,628.40
38.00
24.00
57.00
49.50
516.00
43.00
10.50
2,873.65
309.00
4.50
987.04
7,747.43
10.00
197.00
1.50
20.00
409.00
5.00
394.95
Total
809
152,155.92 16,573.97
til Only agricultural applications are tabulated in this column.
Source: California Department of Agriculture Pesticide Use
Report 1972.
68
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Table 9. USE OF BROMACIL IN CALIFORNIA IN 1973 BY CROPS AND OTHER USES,
APPLICATIONS, QUANTITIES, AND ACRES TREATED
Commodity
Alfalfa
Alfalfa fur seed
Almond
Apricot
Avocado
Citrus
City agency
Cotton
County agricultural commissioner
County or city parks
County road
Federal agency
Fallow (open ground)
Flood control
Flowers
Grapefruit
Crape
Industrial areas
Irrigation district
Lemon
Lettuce/head
Line
Nectarine
Nonagricultural areas
Nursery stock
Orange
Ornamentals
Ornamental bedding plants
Other agencies
Peach
Potato
Reclamation district
Residential control
School district
Soil (fumigation only)
Squash, summer
State highway
Strawberry
Structural control
Tangerine
Tomato
Turf
University of California
Vector control
Water areas
U-Water areas*-/
Water resources
Applications^/
8
1
1
1
8
61
1
5
3
54
2
8
151
2
1
3
132
1
400
1 CR
1
1
2
8
1
6
1
7
3
22
1
Lb
248.46
50.00
18.00
24.00
269.00
2,455.11
812.48
52.99
5,632.10
20.29
1.489.80
176.74
30.24
3.008.00
6.00
776.05
34.80
77.92
2,453.74
4,106.39
14.76
2.00
7.60
2,155.03
18.52
8,921.63
5.83 CR
1.40
36,084.84
31.80
192.92
73.60
4,025.75
131.09
21.21
0.80
1,260.80
32.37
16.80
5.92
59.14
10.79
350.40
1,287.71
3,738.99
32.00
1,947.15
Acres
390.50
40.00
30.00
40.00
134.50
1,915.50
300.00
20.23
30.00
787.50
29.00
39.00
2,577.90
45.00
1.00
24.00
513.09
1.93
7,463.34
22.00 C
7.00
40.00
182.00
9.93
4.00
132.00
4.00
155.55
3.00
320.25
0.01
Total
895
82,161.30
15,218.22
a/ Only agricultural applications are tabulated in this column.
b/ 0 • miscellaneous units.
Source: California- Department of Agriculture', Pesticide Use
Report 1973.
69
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PART-III. MINIECONOMIC REVIEW
CONTENTS
Page
Introduction 71
Citrus 73
Efficacy Against Pest Infestation 74
Cost Effectiveness of Pest Control 74
Noncrop Brush and Weed Control 75
Efficacy Against Pest Infestation 75
Cost Effectiveness of Pest Control 76
References 78
70
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This section contains a general assessment of the efficacy and cost
effectivensss of bromacil. Data on the production of bromacil in the
United States as well as an analysis of its use patterns at the regional
level and by major application are conducted as part of the Scientific
Review (Part II) of this report. The section summarizes rather than
interprets scientific data reviewed.
Introduction
The efficacy and cost effectiveness of a specific pesticide should
be measurable in terms of the increased yield or improved quality of a
treated crop which would result in a greater income or lower cost than
would be achieved if the pesticide had not been used. Thus, one should
be able to pick an isolated test plot of a selected crop, treat it with
a pesticide, and compare its yield with that of a nearby untreated test
plot. The difference in yield should be the increase due to the use of
the pesticide. The increased income (i.e., the yield multiplied by the
selling price of the commodity) less the additional cost (i.e., the
pesticide, its application and the harvesting of the increased yield)
is the economic benefit due to the use of the pesticide.
Unfortunately, this method has many limitations. The data derived
is incomplete and should be looked on with caution. Review of the
literature and EPA registration files revealed that experimental tests
comparing crops treated with specific pesticides to the same crop with-
out treatment are conducted by many of the state agricultural experimental
stations. Only a few of these, however, have attempted to measure
increased yield and most of this effort has been directed toward just a
few crops such as cotton, potatoes, and sorghum. Most other crop tests
measure the amount of reduction in pest levels which cannot be directly
related to yield.
Even the test plot yield data are marginally reliable, since these
tests are conducted under actual field conditions that may never be
duplicated again and are often not representative of actual field use.
Thus, yield is affected by rainfall, fertilizer use, severe weather con-
ditions, soil type, region of the country, pesticide infestation levels
and the rate, frequency and method of pesticide application.
Because of these factors, yield tests at different locations and
in different years will show a wide variance ranging from a yield de-
cline to significant increases. For example, in a year of heavy pest
infestation, frequent pesticidal use can result in a high yield increase
71
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because the crop from the untreated test plot is practically destroyed.
Conversely, in a year of light infestation, the yield increase will be
slight.
The use of market price to estimate the value received by the pro-
ducer also has its limitations. If the use of the pesticide increases
the yield of a crop and the national production is increased, then the
market price should decline. According to J. C. Headley and J. N. Lewis
(1967),A/ a 1% increase in quantity marketed has at times resulted in a
greater than 1% decrease in price. Thus, the marginal revenue from the
increased yield would be a better measure of value received.
A third limitation to the quantification of the economic costs and
benefits is the limited availability of data on the quantities of the
pesticide used by crop or pest, the acres treated, and the number of
applications. In most cases the amount of bromacil used on each crop
(or noncrop) application is not available.
As a result of these limitations an overall economic benefit by
crop or pest cannot be determined. This review presents a range of the
potential economic benefits derived from the use of bromacil for control
of a specific pest on a specific crop. This economic benefit or loss
is measured in dollars per acre for the highest and lowest yield developed
from experimental tests conducted by the pesticide producers and the state
agricultural experimental stations. The high and low yield increases are
multiplied by the price of the crop and reduced by the cost of the broma-
cil applied to generate the range of economic benefits in dollars per
acre.
Economic benefits from noncrop applications (e.g., grass and brush
control along highways, utility lines, and railroads) are best measured
by an alternative costing method. Alternative methods to chemical con-
trol include mechanical control such as mowing, discing, bulldozing and
the use of brush cutting machines. Hand labor is often required for
mowing around trees, poles and other objects and for weeding or cutting
brush. In some cases burning for control of grasses along canal banks
is an alternative.
\J Headley, J. C., and J. N. Lewis, The Pesticide Problem; An Economic
Approach to Public Policy, Resources for the Future, Inc., pp.
39-40 (1967).
72
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The true economic benefits cannot be measured because much of the
noncrop weed control is for aesthetic reasons such as beautification of
highways. It is also a form of preventative maintenance to keep fires
from causing damage when grasses are dry. Therefore, the cost of the
chemical control should be subtracted from the alternative control cost,
such as hand labor or mechanical control, to determine the economic
benefit from the use of bromacil.
Bromacil is a broad-spectrum pesticide used as a herbicide and soil
sterilant. It controls a wide variety of annual and perennial grasses
such as Johnson grass, Bermuda grass, nutsedge and dallisgrass. Brush
such as blackjack and post oak, hackberry, maple, oak, poplar, sweet
gum, wild cherry and others are also controlled.
Bromacil is a relatively new herbicide having been introduced dur-
ing the past decade* Although there is a significant number of references
relating to the efficacy of bromacil, little is available regarding the
economics of its use. This latter situation arises from the difficulty
in measuring its true economic value; bromacil often takes two to three
years to control vegetation effectively, but the quantity needed to
maintain control declines after the initial application .
Most of the bromacil is used to control grass and brush along rail-
roads, utility lines, roads, fences, buildings, and other noncrop areas.
It is used for beautification of.the area by removal of the weeds, but
may be used to prevent fires along railways, or because of federal or
state requirements for weed and brush control.
The only registered crop uses are for control of weeds and grasses
in pineapple and citrus groves.
The following subsection summarizes available literature on the
efficacy and cost effectiveness of bromacil.
Citrus
Bromacil is recommended for control of annual and perennial grasses
in citrus groves. Control of grasses can promote faster tree growth by
reducing the competition for water. It also improves spraying effective-
ness and yields.
73
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Efficacy Against Pest Infestation
Only one reference was found in the literature which relates broma-
cil use' to improved yields. Tucker et al. (1971)i/ initiated experiments
in Florida in 1967 to evaluate several soil residual herbicides over a
3-year period. These herbicides were tested on oranges and tangelos.
The results showed that bromacil consistently proved to be the most
wide-spectrum herbicide and provided the best control over the 4-month
period at all locations. Its "burndown" action was good without a sur-
factant and its residual control was satisfactory. Bermuda grass was
the main grass controlled. Spanish needles, pigweed and Vasey grass be-
came a problem in some of the plots. Control of weeds by bromacil
averaged from 75 to 907. in the four counties under test.
Tree growth varied in each county and was usually faster with the
bromacil treatment. Tree growth was associated with degree of weed re-
moval and depth of tree feeder roots. Mechanical hoeing severely pruned
the feeder roots in some areas limiting growth.
The influence of bromacil on fruit yield and quality was measured
in one test. With bromacil applied at a rate of 3.5 Ib/acre, the yields
compared to a mechanically hoed check increased from 200 boxes/acre to
225 boxes/acre.
Cost Effectiveness of Pest Control
The price of oranges in 1972 averaged $2.42/box (Agricultural
Statistics 1973)—', and the cost of bromacil averaged $9.50/lb of active
ingredient (Bost, 1974)!/.
Using the above prices and costs the increased income for the 25-
box yield increase would be $60.50/acre, Bromacil costs at an applica-
tion rate of 3.5 Ib/acre would be $33.25. This would result in an eco-
nomic benefit of $27.25/acre based upon this test.
I/ Tucker, D. P. H., and R. L. Phillips, "Weed Control Demonstrations
in Florida Citrus Groves," Southern Weed Science Society Proceed-
ings. 24:235-240 (1971).
£/ United States Department of Agriculture (1973). Agricultural
"~ Statistics 1973.
3i/ Bost, W. M., Director, Cooperative Extension Service, Mississippi
*~ State, Mississippi, personal letter to D. F. Hahlen (1974).
74
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The actual economic benefits for this test would be greater
since the yield comparisons were made with a mechanically hoed test
plot. A completely untreated field could have produced a much
lower yield than the hoed plot.
Noncrop Brush and Weed Control
Efficacy Against Pest Infestation
Bromacil is used for a wide variety of weed and brush control ap-
plications by industry, commercial firms and local governments. It is
used along railroad right-of-ways, in drainage ditches, around utility
poles and lines, on farm fence rows and along embankments. It controls
a wide number of grasses and woody plants. Walls (1971)-i/ evaluated
bromacil for control of highway weeds in Georgia, North Carolina, and
South Carolina, and found that bromacil controlled 1007. of the annual
weeds and grasses, 60% of perennial weeds, 107. of Bermuda grass and 307.
of the nut sedge when applied at a rate of 4 Ib/acre. Almost 1007. con-
trol was achieved when applied with 2,4-D and 2,4,5-T amine and Dowpon C.
Rogers (1967)2.7 tested bromacil for control of brush in drainage
ditches in the south and achieved 957. control of willow, cottonwood, and
water locust with doses ranging from 7.5 to 15 Ib Al/acre. Persimmons,
American elm, green ash and hackberry were 957. controlled with 15 to 20
Ib Al/acre.
Lewis (1968)2/ tested several soil sterilants on sand soil in West
Florida for control of annual grasses and weeds such as Bahia, spurge,
pokeweed, Bermuda grass, vasey grass, nutsedge, crabgrass, and smut
grass. He concluded that bromacil had the longest residual action
and was most effective at 10 or 20 Ib/acre.
I/ Walls, C. E., "Post-Emergence Control of Vegetation in Asphalt
Highway Shoulders," Southern Weed Conference Society Proceedings,
24:308-309 (1971).
2/ Rogers, A. G., "Bromacil Effective for Control of Willow and
Cottonwood in Drainage Ditches," Southern Weed Science Society
Proceedings. 20:218-220 (1967).
3_/ Lewis, W. F., "Test of Soil Sterilants in West Florida on Sand
Soil," Southern Weed Science Society Proceedings. 22:273-274
(1968).
75
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Peevy (1973)JV evaluated bromacil and picloram for control of south-
ern hardwoods. Bromacil-treated plots showed a crown reduction after 17
months of 98% for post oak, 93% for blackjack oak, and 89% for hickory
when applied at 5 to 10 Ib/acre. It was much less effective against
huckleberry (16%), American beauty berry (34%) and sassafras (48%).
Similar results were achieved by Peevy (1971)2/ for control of black-
jack and post oak.
Harris et al. (1971)V reported on tests to control woody plants in
Ohio, Michigan, Indiana, and Kentucky in 1968. At applications of
7 ounces/stem, 100% root kill was achieved on maple, sweet gum, box elder,
wild cherry, oak, sumac, white ash, elm, sassafras, hackberry, red bud,
dogwood, poison ivy, winged elm, willow and cottonwood.
Dunn (1967)ft/ evaluated sterilants for control of grasses and trees
on riprap along Lake Pontchartrain levees in New Orleans. He found broma-
cil the most suitable herbicide for control of false willow, tallow,
Bermuda and Vasey grasses when applied at rates of 12 to 16 Ib/acre.
Cost Effectiveness of Pest Control
The economic benefits of the use of bromacil will vary depending
upon the system being controlled, the degree of control and the cost of
alternate treatment. Data that compared the costs of alternate methods
of control is summarized here.
The town of West Springfield, Massachusetts (Chemical Brush Program,
1973)JL/ estimated a cost of $300.00 to $400.00/acre for cutting and
chopping small trees and dense brush thickets along flood control dykes.
A program of chemical control using bromacil cut this figure in half
resulting in economic benefits of $150.00 to $200.00/acre.
I/ Peevy, F. A., "Bromacil and Picloram Under Southern Upland Hardwoods,"
Weed Sci.. 21:54-56 (1973).
2f Peevy, F. A., "Application Data and Dosage Influence Kill of Hard
woods by Soil Application of Bromacil, Fenuron, and Picloram,"
Southern Weed Science Society Proceedings. 24:271-273 (1971).
3/ Harris, C. B., Jr., and Turney J. Hernandez, "Basal Stem Soil Appli-
cations of Bromacil for Woody Plant Control," Southern Weed Science
Society Proceedings, 24:321-322 (1971).
I\J Dunn, C. R., "Riprap Test Work on Lake Pontchartrain Levees,"
Southern Weed Science Society Proceedings, 20:207-211 (1967).
5_/ "Chemical Brush Program Helps Guard a City," Reprinted from Public
Works, 104:3 (March 1973).
76
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Offutt (1967)!/ compared mechanical and chemical weed control meth-
ods for the lower Tule River irrigation district. Mechanical control
cost $134.00/mile or $34.00/acre. Chemical control costs averaged
$324.00/mile the first year but were projected at an average of $110.007
mile or $27.50/acre for future control. This would result in an economic
benefit of $6.50/acre, assuming that bromacil use averaged 1 Ib/acre/year
and application was 2 Ib/acre every 2 years or 3 Ib/acre every 3 years.
In evaluating the economic benefits of chemical weed control, initial
costs are often high, because high dosage rates are usually required for
initial applications of bromacil, but subsequent applications for main-
tenance of the area require significantly less chemical. Therefore, tests
should cover at least a 3-year period and projections of future costs to
maintain the area should be taken into consideration when evaluating
chemical control.
I/ Offutt, J. R., "Chemical Weed Control Replaces Mechanical Weed
Control in Ditch Maintenance," California Weed Conference
ProrP-edingSj 19:32-37 (1967).
77
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References
Boat, W. M., Director, Cooperative Extension Service, Mississippi State,
Mississippi, Personal Letter to D. F. Hahlen (1974).
"Chemical Brush Program Helps Guard a City," Reprinted from Public Works,
104:3 (March 1973).
Dunn, C. R., "Riprap Test Work on Lake Pontchartraln Levees," Southern
Weed Science Society Proceedings. 20:207-211 (1967).
Farm Chemicals Handbook. Meister Publishing Co., Willoughby, Ohio, 1973,
1974.
Harris, C. B., Jr., and T. J. Hernandez, "Basal Stem Soil Applications
of Bromacil for Woody Plant Control," Southern Weed Science Society
Proceedings. 24:321-322 (1971).
Head ley, J. C., and J. M. Lewis, The Pesticide Problem; An Economic
Approach to Public Policy, Resources for the Future, Inc., pp. 39-40
(1967).
Lewis, W. F., "Test of Soil Sterilants in West Florida on Sand Soil,"
Southern Weed Science Society Proceedings, 22:273-274 (1968).
Offutt, J. R., "Chemical Weed Control Replaces Mechanical Weed Control
in Ditch Maintenance," California Weed Conference Proceedings, 19:
32-37 (1967).
Peevy, F. A., "Application Date and Dosage Influence Kill of Hardwoods
by Soil Application of Bromacil, Fenuron, and Picloram," Southern
Weed Science Society Proceedings. 24:271-273 (1971).
Peevy, F. A., "Bromacil and Picloram Under Southern Upland Hardwoods,"
Weed Sci.. 21:54-56 (1973).
Rogers, A. G., "Bromacil Effective for Control of Willow and Cotton-
wood in Drainage Ditches," Southern Weed Science Society Proceedings,
20:218-220 (1967).
Tucker, D. P. H., and R. L. Phillips, "Weed Control Demonstrations in
Florida Citrus Groves," Southern Weed Science Society Proceedings,
24:235-240 (1971).
U.S. Bureau of the Census, U.S. Exports, Schedule B, Commodity by
Country, Report FT 410.
U.S. Department of Agriculture, Agricultural Statistics 1973.
U.S. Environmental Protection Agency, EPA Compendium of Registered
Pesticides, Vol. I.
78
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U.S. Tariff Conies ion, Imports of Benzeooid Cheaicals and Products,
TC Publication 601 (1973).
Walla, C. E., "Poat-Eaergence Control of Vegetation in Aaphalt Highway
Shoulders," Southern Weed Conference Society Proceedings. 24:308-
309 (1971).
79
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