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The information in this profile may be out-of-date.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

Dalapon

Trade and Other Names: Trade names include Alatex, Basinex P, Dalacide, Dalapon-Na (Dalapon-Sodium), Devipon, Ded-Weed, Dowpon, DPA, Gramevin, Kenapon, Liropon, Radapon, Revenge, and Unipon. Dalapon is also called sodium dalapon or magnesium dalapon.

Regulatory Status: Dalapon is classified by the U.S. Environmental Protection Agency (EPA) as a General Use Pesticide (GUP). Dalapon is in toxicity class II - moderately toxic. Products containing the herbicide bear labels with the Signal Word WARNING.

Chemical Class: organochlorine

Introduction: Dalapon is an organochlorine herbicide and plant growth regulator used to control specific annual and perennial grasses, such as quackgrass, Bermuda grass, Johnson grass, as well as cattails and rushes. The major food crop use of dalapon is on sugarcane and sugar beets. It is also used on various fruits, potatoes, carrots, asparagus, alfalfa, and flax, as well as in forestry, home gardening, and in or near water to control reed and sedge growth. Dalapon is applied both before the target plant comes up and after the plant emerges. Commercial products consist of the sodium salt or mixed sodium and magnesium salts of dalapon.

Formulation: Commercial products consist of the sodium salt or mixed sodium and magnesium salts of dalapon.

Toxicological Effects:

• Acute toxicity: Dalapon is moderately toxic to humans. Skin and inhalation exposure could be of significance to dalapon production workers, pesticide applicators, and some agricultural workers [39]. Symptoms of high acute exposure include loss of appetite, slowed heartbeat, skin irritation, eye irritation such as conjunctivitis or corneal damage, gastrointestinal disturbances such as vomiting or diarrhea, tiredness, pain, and irritation of the respiratory tract [40]. Dalapon is an acid which may cause corrosive injury to body tissues [17]. Eye exposure to this material can cause permanent eye damage. Skin burns may occur from dermal exposure to dalapon, especially when skin is moist. Oral LD50 values range from 9330 mg/kg in male rats to 7570 mg/kg in female rats [4]. The oral LD50 is 3860 mg/kg in female rabbits and greater than 4600 mg/kg in female guinea pigs. Dalapon is moderately irritating to skin and eyes [41,17]. The application of the sodium salt of dalapon (in a dry powder formulation) to rabbit eyes produced pain and irritation, followed by severe conjunctivitis and corneal injury, which healed after several days [17].
• Chronic toxicity: Long-term dalapon feeding studies in dogs and rats did show increased kidney weights in animals fed very high daily doses [17,41]. Rats fed 50 mg/kg/day for 2 years showed a slight average increase in kidney weight. No adverse effects were seen in this study in rats fed 15 mg/kg/day. In a 1-year feeding study with dogs fed 100 mg/kg/day, there was a slight average increase in kidney weight. No adverse effects were seen at 50 mg/kg/day [17,41]. These mild effects on the kidneys are consistent with data that show that ingested dalapon is rapidly excreted in the urine.
• Reproductive effects: Tests indicate that dalaopn does not produce adverse effects on fertility or reproduction, except at extremely high doses [41].
• Teratogenic effects: Sodium dalapon was not teratogenic in the rat at doses as high as 2000 mg/kg/day [42].
• Mutagenic effects: Dalapon was not mutagenic when tested in several organisms [42].
• Carcinogenic effects: No carcinogenic effects were seen in rats fed the sodium salt of dalapon at 5, 15, or 50 mg/kg/day for 2 years [41,42].
• Organ toxicity: Dalapon dust and vapor may be irritating to the respiratory tract [17]. Repeated or prolonged exposure to dalapon may cause irritation to the mucous membrane linings of the mouth, nose, throat, lungs, and to the eyes [17]. Chronic skin contact can lead to moderate irritation or even mild burns, although occasional contact is not likely to produce irritation. Dalapon is not absorbed through the skin in toxic amounts [41].

• Fate in humans and animals: The half-life of dalapon in human blood is 1.5-3 days [39]. Dalapon's half-life in the blood system of dogs is about 12 hours [39,41]. Dalapon and all of its known breakdown products dissolve easily in water. They are readily washed from cells and tissues. Because dalapon is insoluble in organic solvents and lipids, it does not build up in animal tissues. A nonmetabolized form of dalapon was excreted in the urine of animals fed the herbicide. Less than 1% of the ingested dose appeared as residues in the milk of dairy cows that were fed dalapon [17,39].

Ecological Effects:

• Effects on birds: Dalapon is practically nontoxic to birds. When dalapon was fed to 2-week old birds for 5 days, followed by untreated feed for 3 days, the LC50 of dalapon was more than 5000 ppm in mallards, ring-necked pheasants, and Japanese quail [17,43]. The acute oral LD50 of dalapon is 5660 mg/kg for chickens. While dalapon is practically nontoxic to birds, reproduction rates of birds are decreased at very high doses [17]. Reproduction was depressed in mallard ducks that were fed one fourth the dose of dalapon that caused death [43].
• Effects on aquatic organisms: Dalapon is practically nontoxic to fish [43]. While there were no deaths reported in goldfish after a 24-hour exposure to 100 mg/L of dalapon, all fish died after a similar exposure to 500 mg/L or above [17]. The 1-to-21-day LC50 values for dalapon in fish are all on the order of 100 mg/L for several species tested [9,17]. The LC50 for dalapon in bluegills is 105 mg/L [9,17]. Its toxicity to aquatic invertebrates varies, depending on the species. Values can be as low as the 48-hour effective concentration (EC) of 1 mg/L in brown shrimp, or as high as the 96-hour LC50 of 4800 mg/L in other crustaceans. Aquatic crustaceans and insects are the most dalapon-sensitive of the aquatic invertebrates. Dalapon is only slightly toxic to mollusks [9,17].
• Effects on other organisms: Dalapon is relatively nontoxic to honeybees and other insects and has low toxicity to soil microorganisms [9,17].

Environmental Fate:

• Breakdown in soil and groundwater: Dalapon has a low to moderate persistence in soil. It remains in the soil for 2 to 8 weeks [14]. Dalapon has residual activity in soil for 3 to 4 months when it is applied at high rates (22 kg/hectare) [9]. Dalapon does not readily bind to soil particles. In clay and clay loam soils, there may be no adsorption. Since it does not adsorb to soil particles, dalapon has a high degree of mobility in all soil types and leaching does occur. However, dalapon movement in soil is usually limited by rapid and complete breakdown of the herbicide into naturally-occurring compounds by soil microorganisms [12,14]. Dalapon is not found below the first 6-inch soil layer. Higher temperatures and increased soil moisture speed up degradation. At higher temperatures, dalapon can also be degraded by ultraviolet light from the sun [39]. In a national groundwater survey, dalapon was not found in groundwater [17].
• Breakdown in water: In ponds and streams, dalapon disappears via microbial degradation, hydrolysis, and photolysis [12]. Microbial degradation tends to be the most active form of its breakdown in water. In the absence of microbial degradation, the half-life of dalapon, by chemical hydrolysis, is several months at temperatures less than 25 C. Hydrolysis is accelerated with increasing temperature and pH [39,42].
• Breakdown in vegetation: Dalapon is absorbed by plant roots and leaves and moved (or translocated) within plants [9]. It tends to build up in the areas of greatest plant metabolic activity, such as developing seeds and in the tips of roots, shoots, and leaves. At high rates of application, dalapon precipitates out of solution as an acid, and has immediate and local acute effects on foliage [17]. It is easily washed off foliage. In addition to herbicidal activity, dalapon is a plant-growth inhibitor. Conditions of increased light and high temperature may cause nutrient solutions or soil applications of dalapon to build up in the tops of plants, via transpiration [17].

Physical Properties:

• Appearance: Dalapon is a type of acid that is usually formulated with sodium and magnesium salts [44]. The acid itself is not used directly. Commercial products usually contain 85% sodium salt or mixed sodium and magnesium salts of dalapon [17]. In its pure acid form, dalapon is a colorless liquid with an acrid odor. As sodium-magnesium salts, it is a white to off-white powder [9,39].
• Chemical Name: 2,2-dichloropropionic acid [9]
• CAS Number: 127-20-8 (sodium salt); 75-99-0 (acid)
• Molecular Weight: 164.95
• Water Solubility: 900,000 mg/L @ 25 C (sodium salt) [9]
• Solubility in Other Solvents: alkali solvents, v.s.; ethanol v.s.; acetone, benzene, and methanol s. [9]
• Melting Point: (with decomposition) 166.5 C (sodium salt) [9]
• Vapor Pressure: 0.01 mPa @ 20 C (sodium salt) [9]
• Partition Coefficient: 0.778 [17]
• Adsorption Coefficient: 1 (sodium salt) [14]

Exposure Guidelines:

• ADI: Not Available
• MCL: 0.2 mg/L [8]
• RfD: 0.03 mg/kg/day [8]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

BASF Corp.
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 6

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.