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Acifluorfen. Pesticide Information
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E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension
Offices of Cornell University, Michigan State University, Oregon State University,
and University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment
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Pesticide
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Acifluorfen
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TRADE OR OTHER NAMES
Acifluorfen is found in several Blazer products. Other trade names include Carbofuorfen,
RH-6201 (sodium acifluorfen), and Tackle. This herbicide is compatible with other
pesticides though its toxicity to crops may increase.
INTRODUCTION
Acifluorfen is a contact diphenolic ether herbicide used to control broadleaf
weeds and grasses in soybeans, peanuts, peas, and rice It can be applied before
or after crop emergence. It is especially effective against cocklebur, velvetleaf,
common lambsquarters, morning glory, and jimsonweed. Acifluorfen selectively controls
broadleaf weeds when applied after soybeans have emerged (6).
The activity of this compound is enhanced by sunlight. Acifluorfen may be toxic
to some crops plant such as soybeans if mixed with fertilizers.
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Acifluorfen is very toxic and is labeled with a DANGER signal word due to its
potential to cause serious eye injury. Other effects occur only at higher doses.
Symptoms of acute exposure to acifluorfen are not recorded for humans. The oral
LD50 of acifluorfen in male albino rats is 1,300 mg/kg (7). In
rabbits, the dermal LD50 of Blazer is 450 mg/kg, while it is 2,000 mg/kg for Tackle
(2).
CHRONIC TOXICITY
In animals, acifluorfen adversely affects development and liver and kidney weights.
Research indicates that it is not mutagenic. Studies on reproductive effects are
inconclusive.
Reproductive Effects
No adverse effects were observed in rodent parents or their offspring when the
parents were fed daily doses well below lethal levels. Body weights, food consumption,
fertility, and pregnancy were comparable in both treated and untreated animals
(2).
However, in another rat study, at higher doses, both parents and offspring
suffered kidney lesions and death. This suggests that levels high enough to
cause toxicity in the mother are needed to affect reproduction (2).
Teratogenic Effects
In one study, rats were given high doses of sodium acifluorfen through a stomach
tube during the critical periods of pregnancy. At these doses, body weights of
the fetuses were lower, and bone development was delayed (2).
Mutagenic Effects
Various mutagenesis assays of acifluorfen products indicate that this pesticide
does not cause mutations. These include studies of both bacteria and cells from
mammals (2).
Carcinogenic Effects
Some studies show acifluorfen to be carcinogenic, while others do not; the main
differences among the studies were the dose levels administered and the lengths
of the studies. One study of mice fed high doses for 18 months showed decreases
in body weight and increases in both benign and malignant liver tumors (2).
As a result, acifluorfen is classified as a probable human carcinogen by the U.S.
Environmental Protection Agency (8).
Organ Toxicity
In addition to being a skin and eye irritant, acifluorfen affects the weight and
functions of the liver, heart, and kidneys at high doses.
Male and female rats fed high daily doses for four weeks showed decreased food
consumption and increased liver and kidney weights (2). In
a one-year study of rats fed lower doses, both sexes experienced decreased body
weight and increased liver weight (2).
In a two year study, beagle dogs were fed high daily doses of acifluorfen.
Irregular heart rhythms were noted in some of the animals. In addition, there
were some blood changes and an increase in liver and kidney weights (2).
ECOLOGICAL EFFECTS
Aciflurofen is slightly toxic to fish. The LC50 values for the compound range
from 31 mg/l for bluegill to 54 mg/l for rainbow trout. The compound is also only
slightly toxic to mallards and is moserately toxic to bobwhite quail. It is non-toxic
to bees. No information on bioaccumulation was found.
ENVIRONMENTAL FATE
Acifluorfen is a moderately persistent, selective herbicide. Light, temperature,
and relative humidity influence acifluorfen activity.
In susceptible plants, such as common cocklebur and ragweed, the compound is
absorbed through the leaves and roots and is translocated only slightly. Maximum
herbicide action occurs three to seven days after it is applied (1).
The herbicide works by inhibiting a critical plant enzyme. In acifluorfen-resistant
plants like soybeans, no acifluorfen movement from the treated leaves takes
place. These plants can metabolize acifluorfen into a non-toxic form (4).
High relative humidity favors herbicide penetration in the plant. High temperatures
before and after spraying tend to increase weed susceptibility and death (3).
Acifluorfen usually lasts from four to six weeks in the soil. In one study,
acifluorfen applied to a silt loam degraded with a half-life of 59 days. Microbial
action accounts for the majority of the compounds loss from soil. No leaching
of the chemical below three inches was observed (2). Acifluorfen
was looked for, but not found, in a number of wells throughout the United States.
Acifluorfen is rather stable in water; no degradation was observed in laboratory
studies lasting up to 28 days (2). However, when it is exposed
to sunlight in the water, it degrades quickly. The half-life under continuous
light was 92 hours in water (2). When it does degrade, the
primary breakdown product tends to vaporize (2). Because of
its sensitivity to light, this chemical has an atmospheric half-life of about
4.5 days. It evaporates from the soil surface.
PHYSICAL PROPERTIES AND GUIDELINES
In its physical state at 25 degrees C, acifluorfen is most often an off-white
solid as an acid, or a white powder or brown crystalline powder as a sodium salt.
It should not be mixed with oils, surfactants, liquid fertilizers, and other pesticides.
It is a member of the phenolether chemical family. Its chemical name is sodium
5-[2-chloro-4- (trifluoro-methyl)phenoxy]-2-nitrobenzoate.
Physical Properties:
CAS #: |
62476-59-9 (sodium salt); 5094-66-6 (white solid) |
Solubility in water: |
>25g/100g |
Melting point: |
124-125 degrees C (white powder); 151.5-157 degrees C (acid) (2) |
K(ow): |
-4.85 (acid; calculated) (2) |
Exposure Guidelines:
NOEL: |
1.25 mg/kg/day (2) |
ADI: |
0.0125 mg/kg/day (2) |
Drinking water health advisory: |
|
Drinking Water Equivalent Level (DWEL): |
0.427 mg/L (2) |
BASIC MANUFACTURER
BASF Corp.
Agr. Prod. Group
P.O. Box 13528
Research Triangle Park, NC 27709-3528
Telephone: 919-361-5722
Review by Basic Manufacturer:
Comments solicited: November, 1992
Comments received:
REFERENCES
- Johnson, W.O.; Kollman, G.E.; Swithenbank, C; and Yih, R.Y. 1978. RH-6201
(Blazer): A new broad spectrum herbicide for postemergence use in soybeans.
J. Agric. Food Chem. 26 (1): 285-286.
- U.S. Environmental Protection Agency, Office of Drinking Water. "Acifluorfen
Health Advisory." Draft Report. August 1987.
- Ritter, R.L. and Coble, H.D. 1981. Influence of temperature and relative
humidity on the activity of acifluorfen. Weed Science. 29: 480-485.
- 1981. Penetration, translocation, and metabolism of acifluorfen in soybean,
common ragweed, and common cocklebur. Weed Science. 29: 474- 480.
- "SAP Makes Draft Recommendations on Two of Eight Pesticides."
Pesticide and Toxic Chemical News, 16 December 1987, p. 32.
- Wills, G.D. and McWhorter, C.G. 1981. Effect of environment on the translocation
and toxicity of acifluorfen to showy crotalaria. Weed Science. 29: 397-408.
- Windholz, M. et al., eds. The Merck Index. 10th edition. p.16, Rahway, N.J.:
Merck & Co. Inc., 1983.
- Quest, John A., Whang Phang, Karen L. Hamernik, Marcia van Gemert, Bernice
Fisher, Richard Levy, Theodore M. Farber, William L. Burnam, and Reto Engler.
1989. Evaluation of the Carcinogenic Potential of Pesticides, 1. Acifluorfen.
Regulatory Toxicology and Pharmacology 10: 149-159. /OL>
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