CALIFORNIA DEPARTMENT OF PESTICIDE REGULATION
PUBLIC REPORT 2003-6
Flumioxazin
Tracking ID Number 191861 N
DESCRIPTION OF ACTION
Valent U.S.A. Corporation submitted an application seeking California registration of
Chateau™ Herbicide SW to control certain grassy and broad-leaf weeds in various
agricultural crops. This product contains the new active ingredient flumioxazin.
The Department of Pesticide Regulation (DPR) evaluated the product label and scientific
data supporting registration of the product and found them to be acceptable to support a
conditional registration. The acute health risks from exposure to flumioxazin are
minimal due in part to its low mammalian toxicity. The precautionary and first aid
statements on the product label in conjunction with the required personal protective
equipment (PPE) adequately mitigate potential health risks to persons who may come in
contact with the pesticide. DPR does not expect significant adverse environmental
impacts to result from registration of this product.
DPR accepted Valent’s application for registration of Chateau™ Herbicide SW
concurrently with Valent’s submission of an application to the United States
Environmental Protection Agency (U.S. EPA) for federal registration. U.S. EPA
conditionally registered Chateau™ Herbicide SW on April 12, 2001. The Agency
required the following studies be submitted within two years or the registration will be
subject to cancellation: a more specific confirmatory analytical method for plant
commodities, two aqueous photolysis studies, two anaerobic soil/aqueous metabolism,
and two field dissipation studies. These studies have since been completed and reviewed
by DPR.
BACKGROUND
Registrant:
Valent U.S.A. Corporation
Common name:
Flumioxazin
Chemical name:
2-[7-fluro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazin-
6-yl]-4,5,6,7-tetrahydro-1H-isoindole-1,3(2H)-dione
Brand names:
Chateau™ Herbicide SW
Uses:
Weed control in peanuts and soybeans and sites to be planted to
cotton, field corn, rice, sorghum, sugarcane, sunflowers, tobacco
or wheat.
Pests controlled:
Certain grassy and broad-leaf weeds, such as crabgrass, Russian
thistle, and velvetleaf.
Type of registration: Conditional for two years
Chateau™ Herbicide SW is formulated as a water dispersible granule with 51%
flumioxazin. Flumioxazin is a light-dependent peroxidizing herbicide that blocks
chlorophyll biosynthesis resulting in the accumulation of photo-toxic porphyrins in the
plant tissues. Flumioxazin is active on a broad spectrum of broad-leaf weeds and some
grassy weeds. Chateau™ Herbicide SW can be applied in peanuts and soybeans prior to
crop emergence to control existing weeds. Rainfall, a light irrigation or cultivation are
needed to activate flumioxazin. Chateau™ Herbicide SW can also be applied as a
“burndown” treatment on sites that will later be planted with the crops listed on the
product label. In California, the predominant use will probably be to “burndown” weeds
before planting cotton, field corn, rice, sorghum, sunflowers, or wheat. The label
recommends applying 2 to 3 ounces of product per acre (0.064-0.096 lb. active
ingredient) with one application per year. Applications can be made with ground and
aerial application equipment. However, application of the product through any type of
irrigation system is prohibited. For aerial applications, the product label requires a 40
foot buffer zone between the target crop and non-labeled crops and plants to mitigate the
potential for crop damage from drift.
SCIENTIFIC REVIEW
A. Chemistry
1. Product Chemistry: DPR evaluated the submitted chemistry studies for
flumioxazin and summarized the results in the following table.
Table I. Physical and Chemical Properties of Chateau™ Herbicide SW
Properties
Values
Physical state
Light tan solid
Odor
Odorless
Density*
1.51 g/cm3 at 20o C
Bulk density
0.37 g/ml (22.8 lb. ft3)
Partition Coefficient*
3.54 x 102 at 20o C
Solubility (water)*
1.79 mg/L at 25o C
pH in water
6 at 22o C
Vapor pressure*
2.41 x 10-6 mm Hg at 22o C
Stability
Stable one year in commercial pkg.
* These properties were derived using technical flumioxazin as the test substance.
DPR found the product chemistry data satisfactory to meet the regulatory data
requirements to support the registration of this product.
2. Residues in Food and Animal Feed: The submitted residue studies support the
harvest and use limitations listed on the Chateau™ Herbicide SW label for peanuts
and soybeans. The residue levels are well within the tolerances established by the
U.S. EPA for peanuts and soybeans. The established tolerances are listed in the
following table.
Table II. Tolerances for Residues of Flumioxazin
Commodity
Parts Per Million
Peanuts
0.02
Soybean seed
0.02
Valent U.S.A. Corporation submitted rotational crop studies to support the
“burndown” uses for the listed crop sites and the rotational crop statements for non-
listed crops. DPR determined the data to be adequate.
3. Environmental Fate: The environmental fate data reviewed included studies on
hydrolysis, photolysis (aqueous and soil), aerobic soil metabolism, anaerobic soil
metabolism (aquatic) and terrestrial field dissipation. Flumioxazin is unstable in the
environment with a half-life ranging from 0.01-5 days depending upon pH. The data
indicates hydrolysis is probably the primary pathway for degradation. Flumioxazin is
unstable in the presence of light with a one day half-life in water and 3-8 day half-life
on soil. The aerobic soil metabolism studies observed a moderate rate of metabolism
with a half-life of 5-19 days depending on the soil type. The anaerobic soil
metabolism study with a saturated soil observed a half-life of less than one day.
Terrestrial field dissipation of flumioxazin in loam and sandy soils ranged from 10-42
days. The high value was thought to be due to a lack of rainfall or irrigation during
the sampling period. The degradation of flumioxazin on soil was too rapid to
determine an adsorption/desorption coefficient. Two soil column leaching studies
were conducted using various types of agricultural soils. The majority of the residues
remained incorporated with the organic matter in the soil indicating flumioxazin
resists leaching.
The submitted studies were found to be satisfactory to support a conditional
registration of Chateau™ Herbicide SW. This product may be registered, provided
the registrant conducts and submits the results of a flumioxazin metabolite study in
lactating goats and a terrestrial field dissipation study (now in progress). Chateau™
Herbicide SW is expected to have minimal impact on the environment. When used in
accordance with label directions, there is little potential for flumioxazin to accumulate
or move into ground water.
B. Toxicology
DPR reviewed the toxicology studies submitted by Valent U.S.A. Corp. and found
them adequate to conduct a complete toxicological evaluation for Chateau™
Herbicide SW. DPR evaluated the data to ascertain the potential for acute adverse
health effects from exposure. The acute toxicity parameters are summarized in Table
III.
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Table III. Acute Toxicity of Chateau™ Herbicide SW
Type of Study
Acute Toxicity Values Acute Toxicity Category
Acute oral (rats)
>5000 mg/kg (M/F)
IV
Acute dermal (rabbits)
>2000 mg/kg (M/F)
III
Acute inhalation (rats)
>0.969 mg/l
III
Primary eye irritation (rabbits)
N/A
IV
Primary dermal irritation (rabbits)
N/A
IV
Dermal sensitization (guinea pigs)
N/A
Not a sensitizer
Signal word
N/A
CAUTION
N/A-Not applicable.
DPR’s evaluation indicates that Chateau™ Herbicide SW is low in mammalian
toxicity. The precautionary language on the product label adequately identifies the
acute toxicity hazards noted in the studies.
DPR found the submitted toxicology studies sufficient to satisfy the data
requirements of the Birth Defects Prevention Act (Food and Agricultural Code
section 13121 et.al.). Possible adverse health effects were observed in four of the
toxicity studies. A combined chronic toxicity and oncogenicity study in rats indicated
hypochronic and microcytic anemia. The subchronic dietary rat study noted adverse
effects of anemia and hepatic necrosis. The two-generation rat reproduction study
observed lower pup viability. The rat teratology studies observed malformations in
cardiac and skeletal development. A neurotoxicity study was not submitted. The
Code of Federal Regulations (CFR 40 section 158.340) does not require this study if
the compound is not an organophosphate compound, or does not cause cholinesterase
depression.
DPR has not yet prioritized flumioxazin for risk assessment. DPR prioritizes
pesticide active ingredients for risk assessment based on the nature of the potential
adverse health effects, number of potential adverse effects, number of species
affected, no effect levels (NOELs), potential for human exposure, use patterns and
similar factors. Based on these criteria, pesticides with the greatest potential for
health problems are placed in high priority, with other chemicals being in moderate or
low priority. The purpose of the risk assessment would be to appraise the potential
for flumioxazin to cause adverse health effects in humans if exposed to the pesticide
as the result of a legal use. The potential for exposure from eating food crops treated
with flumioxazin will also be evaluated during the risk assessment. Further toxicity
information is available in DPR’s Summary of Toxicology Data for flumioxazin,
available on DPR public website at:
http://www.cdpr.ca.gov/docs/toxsums/pdfs/5802.pdf.
C. Health & Safety
An evaluation of the medical management information on the Chateau™ Herbicide
SW label and the acute toxicity study results indicate the product label bears all of
the required statements and warnings regarding safety for handlers and other persons
who may be exposed to the pesticide. The product label bears an adequate First Aid
Statement. In addition, the product label requires persons handling and applying
Chateau™ Herbicide SW to wear long-sleeved shirt and long pants, waterproof
gloves, and shoes plus socks. Workers wearing only work clothing are not allowed
to enter a treated field until 12 hours after an application. The product label requires
that persons entering a treated area before the 12 hour restricted-entry interval (REI)
has elapsed, must wear coveralls, waterproof gloves, and shoes plus socks if they are
going to contact treated plants, soil or water.
D. Fish & Wildlife
The registrant submitted fish and wildlife toxicity studies, including studies on
northern bobwhite, mallard duck, rainbow trout, bluegill sunfish and daphnia magna.
The submitted data are adequate to characterize the toxicity to wildlife and aquatic
animals from an environmental exposure. Table IV summarizes the results of these
studies.
Table IV. Summary of Toxicity Studies for Wildlife
Test Animal
Type of Study
Acute Toxicity Valuea
Relative Toxicity
Rat (male, female)
Single acute oral dose
>5000 mg/kg(LD50)
Relatively non-toxic
Bluegill sunfish
Water exposure (96 hrs.) >21 mg a.i./l (LC50)
Slightly toxic
Sheepshead minnow Water exposure (96 hrs.) 4.7 mg a.i./l (LC50)
Moderately toxic
Rainbow trout
Water exposure (96 hrs.) >2.3 mg a.i./l (LC50)
Moderately toxic
Daphnia magna
Water exposure (48 hrs.) 17 mg a.i./l (LC50)
Slightly toxic
Mysid shrimp
Water exposure (96 hrs.) 0.23 mg a.i./l (LC50)
Highly toxic
Oyster shell
Water exposure (96 hrs.) 2.8 mg a.i./l (EC50)
Moderately toxic
Bobwhite quail
Single oral acute dose
>2250 mg/kg (LD50)
Relatively non-toxic
Bobwhite quail
Feeding study (8 days)
>5620 mg/kg (LC50)
Relatively non-toxic
Mallard duck
Feeding study (8 days)
>5620 mg/kg (LC50)
Relatively non-toxic
Honeybee
Single dermal dose
105 µg/bee (LD50)
Relatively non-toxic
Values expressed as: 1. LD50= lethal dose that will kill 50% of test population; and 2. LC50= lethal
environmental concentration that will kill 50% of test population. The test substance used for the
studies was technical flumioxazin.
The data indicate flumioxazin is relatively non-toxic to vertebrate animals, birds and
honey bees, and moderately toxic to fish. The data indicate that flumioxazin is highly
toxic to some salt water invertebrates. The label bears adequate precautionary
statements regarding the toxicity of the product to aquatic invertebrates. The
environmental fate data indicates flumioxazin is unstable in the environment and
degrades rapidly. The water solubility is low with a very low vapor pressure
indicating movement off-site should be minimal. The use of Chateau™ Herbicide
SW in production agricultural sites is not expected to pose a threat to wildlife when
used in accordance with label directions.
E. Efficacy
The submitted field studies were adequate to demonstrate the efficacy of Chateau™
Herbicide SW to control the weeds listed on the label. The field data also indicate
that unacceptable levels of phytotoxicity do not occur when recommended rotational
intervals are followed on crops grown in midwestern or southern soil types.
However, no data were submitted to demonstrate that Chateau™ Herbicide SW can
be safely used on crops grown under California climatic conditions and soils.
The submitted data are adequate to support a two-year conditional registration in
California. Additional phytotoxicity data are needed to demonstrate the labeled
preplant intervals are adequate for crops grown in California. An aerial spray drift
study is also needed to support the adequacy of the required buffer zones for sensitive
crops growing adjacent to treatment sites..
ALTERNATIVES
Chateau™ Herbicide SW is a contact herbicide which is active on a wide range of broad-
leaf weeds and some grassy weeds. It can also be used in combination with other
herbicides to broaden the spectrum of weeds controlled with a “burndown” application.
With a maximum use rate of 1.5 oz of A.I. per acre, Chateau™ Herbicide SW can
provide weed control at much lower use rates than most conventional contact herbicides.
Its use can help to reduce the amount of herbicide needed for weed control in the labeled
crops. Flumioxazin is low in mammalian toxicity and is safer for pesticide handlers to
work with compared to many other contact herbicides.
CONCLUSION
DPR evaluated the product label and scientific data submitted to Chateau™ Herbicide
SW and found them acceptable to support a two year conditional registration. The acute
health risks to humans from exposure to flumioxazin are minimal due in part to its low
mammalian toxicity. The precautionary and first aid statements on the product label, as
well as the required PPE mitigate potential health risks to persons who may be exposed to
the pesticide. If, after a risk assessment, DPR determines that exposure to flumioxazin
may result in unacceptable margins of exposure, further restrictions will be placed on the
use of flumioxazin at that time. The submitted data also indicate significant adverse
environmental impacts are not expected to occur from the use of Chateau™ Herbicide
SW. When used in accordance with label directions, this product should be effective for
the intended use.
DPR is proposing a two-year conditional registration of Chateau™ Herbicide SW. The
registrant is required to conduct and/or submit the results of the following studies: a
terrestrial field dissipation study conducted in California, a metabolism study in lactating
goats, field data to support the aerial application buffer zones for sensitive crops, and
phytotoxicity data that demonstrates the preplant intervals for crops grown under
California climatic and soil conditions are adequate.