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
Publication Date: 9/93
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.
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.
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).
In animals, acifluorfen adversely affects development and liver and
kidney weights. Research indicates that it is not mutagenic. Studies
on reproductive effects are inconclusive.
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
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).
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).
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).
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).
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.
Acifluorfen is a moderately persistent, selective herbicide.
Light, temperature, and relative humidity influence acifluorfen
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
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-
|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)
|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)
Agr. Prod. Group
P.O. Box 13528
Research Triangle Park, NC 27709-3528
Review by Basic Manufacturer:
Comments solicited: November, 1992
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:
1981. Penetration, translocation, and metabolism of acifluorfen in
soybean, common ragweed, and common cocklebur. Weed Science. 29: 474-
"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: