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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
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and the Institute for Environmental Toxicology, Michigan State
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
DCPA is also called chlorthal or chlorthal-dimethyl. Trade names
for products containing DCPA include DAC 893, Dacthal, and
Dacthalor. It may be formulated with other herbicides such as
methazole and propachlor.
DCPA is classified as a General Use Pesticide (GUP). The U.S. EPA
classifies it as toxicity class IV - practically nontoxic.
Products containing DCPA bear the Signal Word CAUTION. Its only
restrictions apply in Washington State which requires
supplemental labeling for Dacthal W-75.
DCPA is a phthalate pre-emergent herbicide used on annual grasses
and annual broadleaf weed species in a wide range of vegetable
crops. About 20% of the use of this compound in the U.S. is for
homes and gardens. Products containing DCPA may be formulated as
wettable powders, granules, or as suspension concentrates.
While there is no toxicological concern for DCPA per se, the
technical product DCPA may contain very small amounts of dioxin
(2,3,7,8, TCDD) and Hexachlorobenzene (HCB) as impurities, which
may be of toxicological concern.
containing DCPA may be formulated as wettable powders, granules,
or as suspension concentrates.
- Acute toxicity: The compound has a very
low toxicity to mammals. The LD50 values for DCPA in rats
range from greater than 3000 mg/kg to 12,500 mg/kg. DCPA
in rabbits and beagle dogs has an LD50 of greater than
10,000 mg/kg. The dermal LD50 in rabbits is greater than
2000 mg/kg. DCPA is not a skin sensitizer. It is a mild
eye irritant. The inhalation LC50 (4-hour) is greater
than 5.7 mg/L for rats [5,7].
- Chronic toxicity: A 3 mg dose in a
rabbit eye produced mild irritation, which disappeared in
24 hours. Dogs given high doses of 800 mg/kg/day for a
month showed some adverse effects in the liver. In
longer-term studies with rats (90 days), similar doses
(about 750 mg/kg/day) caused no adverse effects . In
a 2-year study with rats, a dose of around 50 mg/kg/day
was responsible for changes in the adrenal weights of the
females and in the kidney weights of the males .
- Reproductive effects: Rats fed high
doses of DCPA (500 mg/kg/day) showed no changes in
fertility, gestation, live births, or lactation . The
study was conducted over one full generation. These data
suggest that the compound does not cause reproductive
- Teratogenic effects: Available data
indicate that DCPA is not teratogenic. Pregnant rabbits
fed moderate doses (up to 300 mg/kg) of DCPA on days 8 to
16 of gestation showed no skeletal or organ abnormalities
in the offspring .
- Mutagenic effects: No mutagenicity was
seen in a number of tests, including mutation frequency
and activity, cytogenetic tests, DNA repair, and dominant
lethal tests . This evidence indicates that DCPA is
- Carcinogenic effects: No carcinogenic
effects were noted in rats in a 2-year study where diets
contained up to 500 mg/kg/day of DCPA . Thus, DCPA
does not appear to be carcinogenic.
- Organ toxicity: Long-term studies in
test animals have indicated the liver and adrenal glands
as target organs.
- Fate in humans and animals: Much of the
compound that is ingested is not absorbed. Cows excreted
nearly all of a small dose of DCPA within 5 days, and
dogs absorbed only small amounts (3%) of the compound.
The remaining amount was eliminated within 4 days. When
dairy cows were fed diets with up to 200 ppm of DCPA for
24 days, 0.26 ppm of the compound or its metabolites were
found in milk, while 30 to 90 ppm for 9 or 23 days
resulted in residues of 0.036 ppm and 0.066 ppm in milk.
Residues in other tissues were generally less than 1 ppm
- Effects on birds: DCPA appears to be
moderately toxic to some young wildfowl, and practically
nontoxic to the young of other species and to adult
birds. The LD50 in young bobwhite quail is 5500 mg/kg
. Young mallards and young quail were more sensitive
to the herbicide than adult birds. Diets containing about
250 mg/kg caused heavier mortality to young ducks in the
first 5 days. Older birds had a higher survival rate
- Effects on aquatic organisms: DCPA is
slightly toxic to practically nontoxic to fish depending
on the species. It is practically nontoxic to bluegill
sunfish and slightly toxic to rainbow trout. The compound
is practically nontoxic to estuarine and marine organisms
(invertebrates and some fish). The available data suggest
that DCPA poses no hazard to endangered aquatic species
- Effects on other organisms: At high
doses of DCPA, there was only 3% bee mortality. Thus,
DCPA is only slightly toxic to bees .
- Breakdown in soil and groundwater: DCPA
is moderately persistent. The half-life is from 14 to 100
days in most soils . However, moisture is essential
for degradation. In one study, there was no apparent
buildup of pesticide residues in soil even after repeated
application. The DCPA concentration declined slowly to 75
or 80% in 28 days. Later sampling showed a continued
decline of DCPA and its breakdown products [7,34]. The
DCPA metabolite, tetrachloro-terephthalic acid (TTA or
diacid), is much more water soluble than the parent
compound, and is subject to leaching in some soils. This
metabolite has been detected in groundwater in the onion
growing areas of eastern Oregon . It has been
detected in several other states in the U.S. as well .
- Breakdown in water: There is virtually
no degradation of DCPA in water ranging from moderately
acidic to moderately alkaline (pH 5.0 to pH 9.0).
Breakdown is due to the action of sunlight and the
half-life is greater than 1 week .
- Breakdown in vegetation: Plants may
metabolize DCPA to the same two breakdown products that
are seen in soils, with the proportion varying in
different species. DCPA affects the seed and
pre-emergence stage, but has little effect on crops or
weeds after they have emerged. Limited information
suggests that plants may remove the chlorine molecules of
DCPA (8). In one study, pine trees took up nearly 1% of
the soil applied chemical. The majority of the compound
taken up by the trees remained in the root system, where
it was rapidly diluted.
- Appearance: DCPA consists of colorless
- Chemical Name:
- CAS Number: 1861-32-1
- Molecular Weight: 303.90
- Water Solubility: 0.5 mg/L @ 25 C 
- Solubility in Other Solvents: benzene
v.s.; toluene v.s.; acetone v.s.; carbon tetrachloride s.
- Melting Point: 155-156 C 
- Vapor Pressure: 0.33 mPa @ 25 C 
- Partition Coefficient: Not Available
- AdsorptionCoefficient: 5000
- ADI: Not Available
- MCL: Not Available
- RfD: 0.5 mg/kg/day 
- PEL: Not Available
- HA: 4.0 mg/L (lifetime) 
- TLV: Not Available
5966 Heisley Road
P.O. Box 8000
Mentor, OH 44061-8000
- Phone: 216-357-4100
- Emergency: 216-357-7070
References for the information in this PIP can be found in
Reference List Number 7
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