monocarbamide (Enquik, WilThin) Herbicide Profile 12/87
EPA Pesticide Fact Sheet
Name of Chemical: MONOCARBAMIDE DIHYDROGEN SULFATE
Reason for Issuance: NEW CHEMICAL REGISTRATION
Date Issued: Dec. 30, 1987
Fact Sheet Number: 151
1. DESCRIPTION OF CHEMICAL
Chemical Name: Monocarbamide dihydrogen sulfate
Other Name: Monourea sulfuric acid adduct
Trade Name: ENQUIK
OPP Internal Control Number: 078001
Year of Initial Registration: 1987
Pesticide Type: Herbicide/Desiccant
U.S. and Foreign Producers: Union Chemicals Division, Unocal Corp
2. USE PATTERNS AND FORMULATIONS
- Application sites: Herbicide uses include; Onions (green & dry bulb),
leeks, shallots, spring onions, garlic, peanuts, peas, lentils,
dry beans, garbanzos and grass seed. Desiccant uses include; dry
beans, peas, lentils, peppermint and potato vines.
- Types of formulations: liquid, 81.6% active ingredient
- Types and methods of.application: Applied postemergence to crops and
weeds as a contact pesticide. Diluted with water and applied as a
spray for broadcast, directed or shield spray treatments, using ground
equipment. A wetting agent or non-ionic surfactant may be added.
- Application rates: 20 to 309 lbs. a.i./A, depending upon application
- Usual carriers: water
3. SCIENCE FINDINGS
Summary science statement
- Acute toxicology data indicate that the chemical.is extremely caustic
and corrosive. The appropriate toxicity category is I (DANGER), based
on primary eye and skin irritation studies. Chronic toxicology and
environmental fate data requirements are waived. Avian dietary
studies indicate that the formulated product is practically nontoxic
to mallard ducks and bobwhite quail. Diluted monocarbamide dihydrogen
sulfate is less hazardous to wildlife than the undiluted chemical.
Application is restricted to use of the diluted chemical only.
Potential hazard to fish and wildlife including endangered species is
minimized due to label restrictions against aerial application and
limiting use to the following states; Alabama, Georgia, Idaho,
Michigan, Oregon and Washington.
- Physical state: Viscous liquid
- Color: Colorless
- Odor: Odorless
- Density: 13.14 pounds per gallon
- Miscibility: Limited miscibility in polar organic solvents.
Not miscible with hydrocarbons and lipids.
- Vapor pressure: Negligible up to decomposition temperature of 80oC.
- Crystallization point: 2 degrees C
- pH: 1 (aqueous solution)
- Unusual handling characteristics: Corrosive to nylon, cotton,
leather, aluminum and copper alloy such as brass. Corrosive to skin
and eyes. Explosively decomposes above 160 degrees F. Do not mix with
nitrogen fertilizers as explosive mixtures may result.
- Acute toxicology results:
- Acute oral toxicity (rat): 1,200 mg/kg (male) 350 mg/kg (female)
Toxicity Category II
- Acute dermal toxicity (rabbit): greater than 2 g/kg. Study as
terminated at 48 hours because of extreme caustic action and dermal
necrosis. Toxicity category was not determined.
- Primary skin irritation (rabbit): Caustic on intact and abraded skin
at 24 hours. Study was terminated at 24 hours after similar results
were obtained with 1:4 v/v dilution with water. Toxicity Category I
- Primary eye irritation (rabbit): Severe corneal involvement, grade 4
chemosis of conjunctivae at 24 hours. Because of severity of
reaction, study was terminated at 24 hours. Toxicity category I
- Acute inhalation toxicity (rat): greater than 10.8 mg/l Toxicity
- Additional data not required on acute dermal and primary eye
irritation studies, in accordance with EPA-540/9-82-025,
October 1982, Pesticide Assessment Guidelines Subdivision
(Section 81-2(a)(1)) and Subdivision F (Section 81-4(d)(2)),
- Chronic toxicology results. Additional toxicology studies
(including a three-generation reproduction study) were waived in
accordance with provisions of 40 CFR 162.45 (c). Toxicological
concerns over heavy metal impurities in the sulfuric acid, have been
adequately resolved. Recycled (spent) sulfuric acid will not
be used to manufacture the active ingredient.
- Major routes of exposure: Mixers, loaders and applicators would
be expected to receive the most exposure via skin contact and
Physiological and biochemical behavioral characteristics
- Mechanism of pesticidal action: Monocarbamide dihydrogen sulfate
is a contact herbicide and desiccant. The chemical disrupts cell
membrane structures in a catalytic non-acid consumptive reaction. The
rate of activity is dependent upon the amount of waxy cuticle present
on the surface of treated plants. Plants with a significant wax
coating are less susceptible to damage than others.
- The environmental fate of urea and sulfuric acid are well known from
the literature. Environmental fate data requirements are waived.
- Hazards to fish and wildlife:
- Avian dietary toxicity (Mallard): greater than 5620 ppm (49% a.i.)
- Avian dietary toxicity (Bobwhite): greater than 5620 ppm (49% a.i.)
- Simulated avian field Study: Results indicate that eye and foot
damage may be pronounced for birds exposed to direct applications
of undiluted monocarbamide dihydrogen sulfate. Application of a
diluted solution caused some but much less damage.
- Avian re-entry field study: Results indicate that birds that can
escape during ground application are unlikely to be harmed if they
enter treated fields after application.
- pH study in ephemeral ponds and irrigation water: The study
indicates that under most conditions the acidifying effect of ENQUIK
will be temporary. Only shallow ponds receiving an over-spraying of
ENQUIK would be affected by a lowering of pH.
- Potential problems related to endangered species: Contamination of
habitat areas is not likely to occur as a result of runoff, since the
chemical, once it reaches the soil, is expected to be neutralized.
Potential hazard may exist for those endangered species receiving a
direct spraying of ENQUIK. However, geographical restrictions and a
prohibition against aerial application should minimize any potential
hazard to endangered species .
- Tolerance assessments: Monocarbamide dihydrogen sulfate is exempted
from the requirement of tolerance when used as a herbicide or
desiccant in or on all raw agricultural commodities (40 CFR 10.1084).
4. SUMMARY OF REGULATORY POSITION AND RATIONALE:
- Use, formulation, geographical restrictions: Pesticidal use is
limited to the following states; Alabama, Georgia, Idaho, Michigan,
Oregon and Washington. Aerial application is prohibited.
Unique label warning statements
Physical or Chemical Hazards
"ENQUIK is corrosive to nylon, aluminum, and any copper
alloy such as brass. Do not use pumps or fittings
containing nylon, mild steel, aluminum, brass, leather,
natural rubber or bunam. Non-nylon plastic and 316-L
stainless steel are recommended for application equipment.
Diluted ENQUIK is more corrosive to steel than the
concentrate. Do not allow ENQUIK to be heated above
160 degrees F as explosive decomposition may occur. Do not weld
equipment containing ENQUIK.
Do not mix with nitrogen fertilizers as explosive mixtures
may result. Do not mix with other materials without specific
authorization as hazardous combinations may result.
Clothing: ENQUIK can attack cotton, nylon, and leather
clothing. If ENQUIK contacts clothing of this type,
flush with plenty of water to minimize damage. Wear non-
nylon plastic protective clothing."
"Corrosive. Causes irreversible eye damage and burns to skin.
Face shields or goggles must be worn. Wear suitable protective
equipment to protect skin, such as synthetic rubber or non-nylon
plastic apron, gloves, pants and boots. Wash after contact with
skin. Shower at the end of the working day. Do not wear
contaminated clothing. Avoid spray. Avoid breathing spray mist."
"This product may be harmful to wildlife directly sprayed. Keep
out of lakes, ponds and streams. Do not apply directly to water
or wetlands. Do not contaminate water by cleaning of equipment
or disposal of wastes. Do not apply near waters already damaged
by acid pollution or in areas with soils of poor buffering
capacity if important aquatic resources are adjacent."
5. SUMMARY OF DATA GAPS
6. CONTACT PERSON AT EPA:
Robert J. Taylor
Product Manager (25), (TS-767C)
Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
DISCLAIMER: The information presented in this Pesticide Fact Sheet is
for informational purposes only and may not be used to fulfill data
requirements for pesticide registration and reregistration.