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in 1996. EXTOXNET no longer updates this information, but it may be useful
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E X T O X N E T
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
EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
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.
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.
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.
products consist of the sodium salt or mixed sodium and magnesium
salts of dalapon.
- 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 . 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 .
Dalapon is an acid which may cause corrosive injury to
body tissues . 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 . 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 .
- 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
- Reproductive effects: Tests indicate
that dalaopn does not produce adverse effects on
fertility or reproduction, except at extremely high doses
- Teratogenic effects: Sodium dalapon was
not teratogenic in the rat at doses as high as 2000
- Mutagenic effects: Dalapon was not
mutagenic when tested in several organisms .
- 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 . Repeated
or prolonged exposure to dalapon may cause irritation to
the mucous membrane linings of the mouth, nose, throat,
lungs, and to the eyes . 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
- Fate in humans and animals: The
half-life of dalapon in human blood is 1.5-3 days .
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
- 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 . Reproduction was depressed in mallard ducks
that were fed one fourth the dose of dalapon that caused
- Effects on aquatic organisms: Dalapon is
practically nontoxic to fish . 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 . 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].
- Breakdown in soil and groundwater:
Dalapon has a low to moderate persistence in soil. It
remains in the soil for 2 to 8 weeks . Dalapon has
residual activity in soil for 3 to 4 months when it is
applied at high rates (22 kg/hectare) . 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 .
In a national groundwater survey, dalapon was not found
in groundwater .
- Breakdown in water: In ponds and
streams, dalapon disappears via microbial degradation,
hydrolysis, and photolysis . 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 . 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 . 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 .
- Appearance: Dalapon is a type of acid
that is usually formulated with sodium and magnesium
salts . The acid itself is not used directly.
Commercial products usually contain 85% sodium salt or
mixed sodium and magnesium salts of dalapon . 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
- CAS Number: 127-20-8 (sodium salt);
- Molecular Weight: 164.95
- Water Solubility: 900,000 mg/L @ 25 C
(sodium salt) 
- Solubility in Other Solvents: alkali
solvents, v.s.; ethanol v.s.; acetone, benzene, and
methanol s. 
- Melting Point: (with decomposition)
166.5 C (sodium salt) 
- Vapor Pressure: 0.01 mPa @ 20 C (sodium
- Partition Coefficient: 0.778 
- Adsorption Coefficient: 1 (sodium salt)
- ADI: Not Available
- MCL: 0.2 mg/L 
- RfD: 0.03 mg/kg/day 
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
Agricultural Products Group
P.O. Box 13528
Research Triangle Park, NC 27709-3528
- Phone: 800-669-2273
- Emergency: 800-832-4357
References for the information in this PIP can be found in
Reference List Number 6
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