E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Acifluorfen

Trade and Other Names: Acifluorfen and sodium acifluorfen are found in several Blazer products. Other trade names include Carbofluorfen, RH-6201, and Tackle.

Regulatory Status: Acifluorfen is classified as a General Use Pesticide (GUP) by the U.S. EPA. It is toxicity class III - slightly toxic, but products containing it bear the Signal Word DANGER because it can cause serious eye injury.

Chemical Class: diphenolic ether

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 [2]. Its use in the U.S. is estimated to be in excess of 1.4 million pounds per year.

Formulation: Not Available

Toxicological Effects:

• Acute toxicity: The oral LD50 is 2025 mg/kg in male rats and 1370 mg/kg in female rats, indicating slight acute toxicity [1]. The LD50 for sodium acifluorfen is 1300 mg/kg in rats [8]. In rabbits, the dermal LD50 values of acifluorfen and formulated products are all greater than 2000 mg/kg [58]. In rats, the inhalation LD50 (4-hour) is greater than 6.9 mg/L air [1].
• Chronic toxicity: Male and female rats fed high daily doses for 4 weeks showed decreased food consumption and increased liver and kidney weights. In a 1-year study of rats fed lower doses, both sexes experienced decreased body weight and increased liver weight [54]. In a 2-year study, beagle dogs fed high daily doses of acifluorfen showed irregular heart rhythms. In addition, there were some blood changes and an increase in liver and kidney weights [54].
• Reproductive effects: No adverse effects were observed in rodents or their offspring when the parents were fed daily doses of acifluorfen well below lethal levels. Body weights, food consumption, fertility, and pregnancy were comparable in both treated and untreated animals [54]. 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 [54].
• Teratogenic effects: Acifluorfen may have teratogenic effects at high doses. 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 [54]. Teratogenic effects in humans are unlikely at expected exposure levels.
• Mutagenic effects: Various mutagenesis assays of acifluorfen products on both bacteria and mammalian cells indicate that they do not cause mutations [54].
• Carcinogenic effects: One study of mice fed high doses of acifluorfen for 18 months showed decreases in body weight and increases in both benign and malignant liver tumors [54]. These data are not sufficient to characterize the carcinogenicity of acifluorfen [55].
• 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.

• Fate in humans and animals: No data are currently available.

Ecological Effects:

• Effects on birds: Acifluorfen is practically nontoxic to mallards and is moderately toxic to bobwhite quail. The acute oral LD50 of acifluorfen is 2821 mg/kg in mallards, and 325 mg/kg in bobwhite quail [1]. The range in toxicity to these different species makes any generalizations about its overall toxicity to birds difficult.
• Effects on aquatic organisms: Acifluorfen is slightly toxic to fish. The LC50 values for the sodium salt are 31 mg/L in bluegill and 54 mg/L in rainbow trout [56]. It has a low toxicity to crustaceans. The LC50 (96-hour) in fiddler crabs is greater than 1000 mg/L, and is 150 mg/L in freshwater clams [56].
• Effects on other organisms: Acifluorfen is nontoxic to bees [1].

Environmental Fate:

• Breakdown in soil and groundwater: Acifluorfen is moderately persistent in soils. In one study, acifluorfen applied to a silt loam degraded with a half-life of 59 days [54]. Microbial action accounts for the majority of the compound's loss from soil. No leaching of the chemical below 3 inches was observed [54].
• Breakdown in water: Acifluorfen is stable in water; no degradation was observed in laboratory studies lasting up to 28 days. However, when it is exposed to sunlight, it degrades quickly. The half-life under continuous light was 92 hours in water. When it does degrade, the primary breakdown product tends to vaporize [54].
• Breakdown in vegetation: In susceptible plants, such as common cocklebur and ragweed, acifluorfen is absorbed through the leaves and roots and is translocated only slightly [57]. It works by inhibiting a critical plant enzyme. In acifluorfen resistant plants like soybeans, no acifluorfen movement from the treated leaves takes place because plants break down acifluorfen into a nontoxic form [58]. High relative humidity favors herbicide penetration into the plant. High temperatures before and after spraying tend to increase susceptibility and death [59].

Physical Properties:

• Appearance: At 25 C, the acid of acifluorfen is an off-white solid, and the sodium salt is a white powder or brown crystalline powder [1].
• Chemical Name: sodium 5-(2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoate [1]
• CAS Number: 62476-59-9 (sodium salt)
• Molecular Weight: 361.70
• Water Solubility: >250,000 mg/L @ 25 C [1]
• Solubility in Other Solvents: acetone v.s.; ethanol v.s.; xylene s.s [1]
• Melting Point: 142-167 C [1]
• Vapor Pressure: 0.133 mPa @ 20 C [1]
• Partition Coefficient: 1-1.1761 [58]
• Adsorption Coefficient: 113 (estimated) (salt) [11]

Exposure Guidelines:

• ADI: 0.0125 mg/kg/day [12]
• MCL: Not Available
• RfD: Not Available
• PEL: Not Available
• HA: 0.4 mg/L (longer-term) [54]
• TLV: Not Available

Basic Manufacturer:

BASF Corporation
Agricultural Products Group
P.O. Box 13528
Research Triangle Park, NC 27709-3528

• Phone: 800-669-2273
• Emergency: 800-832-4357
  

References:

References for the information in this PIP can be found in Reference List Number 10

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.