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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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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

2,4-DB

Trade and Other Names: 2,4-DB is 4-(2,4-dichlorophenoxy)butyric acid. Trade names for products containing 2,4-DB include Butoxone, Butyrac, Butirex, Embutone, Embutox, and Venceweed. 2,4-DB may also be found in formulations with other herbicides such as cyanazine, MCPA, benazolin, linuron, and mecoprop.

Regulatory Status: 2,4-DB is a General Use Pesticide (GUP). The U.S. Environmental Protection Agency has classified it as toxicity class III - slightly toxic. Products containing it bear the Signal Word CAUTION.

Chemical Class: phenoxy compound

Introduction: 2,4-DB is a selective systemic herbicide in the phenoxy family. It is used for the control of many annual and perennial broad-leaved weeds in alfalfa, peanuts, soybeans, and other crops. In the plant, the compound changes to 2,4-D and inhibits growth at the tips of stems and roots.

This compound is not to be confused with another phenoxy compound, 2,4-D, and its derivatives, or with the derivatives of 2,4-DB, such as the sodium salt, the isooctyl ester, or the butyl ester. Each of these are slightly different compounds and thus have different toxicities and environmental characteristics. It is found in formulations as a soluble concentrate and as an emulsified concentrate. All of the material in this profile refers to the acid form of 2,4-DB unless specifically stated otherwise. Well over 1 million pounds of 2,4-DB were used in the U.S. in 1990.

Formulation: It is found in formulations as a soluble concentrate and as an emulsified concentrate.

Toxicological Effects:

• Acute toxicity: 2,4-DB is a slightly toxic compound through oral exposure. It has an oral LD50 ranging between 370 mg/kg and 700 mg/kg in rats. The sodium salt has a substantially lower toxicity with an LD50 of 1500 mg/kg in rats and 400 mg/kg in mice [6,7]. In rabbits 2,4-DB is only slightly toxic when exposure is through the skin. The acute dermal LD50 of 2,4-DB is greater than 2000 mg/kg [6].
• Chronic toxicity: At 25 and 80 mg/kg/day, dogs experienced changes in body weight and tissue effects [33]. In a longer-term chronic feeding study with rats, 30 mg/kg effects noted included decreases in body weight, a decrease in heart weight, and changes in blood chemistry [33].
• Reproductive effects: Female rats fed high doses of 75 mg/kg/day of 2,4-DB, experienced a number of chronic effects, including lower ovarian weights and fewer offspring born [33]. These data suggest that reproductive effects are not likely in humans at expected exposure levels.
• Teratogenic effects: No data are currently available.
• Mutagenic effects: Chromosome changes occurred due to exposure to 2,4-DB in Chinese hamster cells; however, the exposure was relatively high (just below a threshold of significant cell toxicity) and for relatively prolonged periods of time (17 or more hours). Tests over 2 hours produced no chromosome changes [33]. The Ames test produced no chromosomal abnormalities in bacterial cells. The data, though minimal, indicate that 2,4-DB is weakly or nonmutagenic.
• Carcinogenic effects: Preliminary evidence suggests that 2,4-DB can cause liver cancer in mice (hepatocellular carcinomas) [33]. However, in another study with rats fed lower doses (to 30 mg/kg/day), no cancer-related changes occurred [33]. Thus the carcinogenic status of 2,4-DB is not clear.
• Organ toxicity: Target organs identified in long-term animal studies include the heart and liver.
• Fate in humans and animals: No data are currently available.

Ecological Effects:

• Effects on birds: Several dietary feeding tests indicate that 2,4-DB is practically nontoxic (LC50 values in excess of 5000 ppm) to waterfowl and upland game birds [33].
• Effects on aquatic organisms: 2,4-DB is slightly to moderately toxic to fish. The LC50 value for the compound is 18 mg/L in the fathead minnow, 7.5 to 17 mg/L in the bluegill sunfish, and 2 to 14 mg/L in the rainbow trout [33,34]. No studies were available on the toxicity of the compound to freshwater or marine invertebrates.
• Effects on other organisms: 2,4-DB is nontoxic to bees [7].

Environmental Fate:

• Breakdown in soil and groundwater: In soil, 2,4-DB is broken down by the action of soil microbes to the product 2,4-D. The half-life for 2,4-DB is about 7 days (21). Because of the risk of groundwater contamination from the whole family of 2,4-D related compounds, special advisories are required on the labels of end-use products related to 2,4-D including 2,4-DB. 2,4-DB has been detected in only 1 well in Texas (out of 928 tested) [23]. It had a concentration of 0.002 mg/L of 2,4-DB.
• Breakdown in water: No data are currently available.
• Breakdown in vegetation: The compound is taken up by the roots and moved throughout the plant. In plants, the compound 2,4-DB is degraded to 2,4-D, which is then broken down further to less toxic materials. In plants tolerant to the herbicide, the breakdown from 2,4-DB to 2,4-D is very slow [6].

Physical Properties:

• Appearance: 2,4-DB is a colorless to white crystal with a slightly phenolic odor. It is slightly corrosive to iron [6].
• Chemical Name: 4-(2,4-dichlorophenoxy)butyric acid [6]
• CAS Number: 94-82-6
• Molecular Weight: 249.10
• Water Solubility: 46 mg/L @ 25 C [6]
• Solubility in Other Solvents: acetone v.s.; ethanol v.s.; diethyl ether v.s.; benzene s.s.; toluene s.s.; and kerosene s.s. [6]
• Melting Point: 117-119 C [6]
• Vapor Pressure: Negligible (acid and salts) [6]
• Partition Coefficient: Not Available
• Adsorption Coefficient: 20 (estimated) (salt) [21]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 8 x 10-3 mg/kg/day [31]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Rhone-Poulenc Ag. Co.
P.O. Box 12014
2 T.W. Alexander Drive
Research Triangle Park, NC 27709

• Phone: 919-549-2000
• Emergency: 800-334-7577

References:

References for the information in this PIP can be found in Reference List Number 7

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.