United States Office of Water EPA 811-F-95-003mT
Environmental Protection 4601 October 1995
Agency
«>EPA National Primary Drinking
Water Regulations
Diquat
CHEMICAL/ PHYSICAL PROPERTIES OCTANOL/WATER PARTITION (Kow): ODOR/TASTE THRESHOLDS: N/A
' Log Kow = -3.05
CAS NUMBER: 85-00-7 BIOCONCENTRATION FACTOR:
DENSITY/SPEC. GRAV.: 1.22 -1.27 at 20° C Not expected to bioconcentrate in
COLOR/ FORM/ODOR: .. aquatic organisms.
Colorless to yellow crystals; water SOLUBILITY: 700 g/L of water at 20° C;
solution is dark reddish brown VerY soluble in water HENRY'S LAW COEFFICIENT:
N/A; no evaporation from water/soil
M.P.: 335-340° C B.P.: N/A SOIL SORPTION COEFFICIENT:
Koc N/A; very low mobility in soil TRADE NAMES/SYNONYMS:
VAPOR PRESSURE: 1.3x10-5 mm Hg at 20° C .1,1 -Ethylene 2,2-dipyridylium dibromide;
Reglone
DRINKING WATER STANDARDS . patterns were as follows: Industrial/commercial uses,
MCLG: 0.02 mg/L 67%; aquatic uses, 33%.
MCL: 0.02 mg/L
RELEASE PATTERNS
HAL(child): none
Diquat is released into the environment during its use
HEALTH EFFECTS SUMMARY as a contact herbicide, aquatic weed control agent, seed
desiccantandsugarcanefloweringsuppressantagent.lt
Acute EPA has found diquat to potentially cause the may a,so be re|eased into wastewater or in spills during
following health effects from acute exposures at levels jts manufacture, transport and storage.
above the MCL: dehydration - n. ,. .• • .
Since diquat is not a listed chemical in the Toxics
Drinking water levels which are considered "safe" for Re|ease inventory, data on releases during its manufac-
short-term exposures have not been established ture and nand|ing are not available.
Chronic: Diquat has the potential to cause the follow-
ing health effects from long-term exposures at levels ENVIRONMENTAL FATE
above the MCL' cataracts
Diquat is rapidly adsorbed by clay constituents of soil
Cancer: There is inadequate evidence to state whether and jn the sorbed state is resistant to biodegradation and
or not diquat has the potential to cause cancer from a photodegradation. The duration of residual activity in soil
lifetime exposure in drinking water. is a few days; the deactivation resulting from its binding
to the soil. In some soils such as montorillonite clay,
USAGE PATTERNS adsorption is considered irreversible. There is some
Diquat is a herbicide that has been used extensively in ?vidence of a !"ore 'ooselv bound component, the frac-
the US since the late 1950s to control both crop and tlon of whlch dePends on the ^ of SO|L
aquatic weeds. Its uses include potato haulm destruc- Diquat is removed rapidly from aquatic systems, prin-
tion; as a desiccant and defoliant to aid harvesting cotton, cipally by adsorption. If adsorption is initially to weeds,
rapeseed and other oil seed crops; to pre-wilt silage, biodegradation to soluble or volatile products occurs in
standing hay, etc. for storage; a plant growth regulator several weeks. When sorbed to sediment, little or no
•id sugar cane-flowering suppressant. degradation probably occurs. In any case, the diquat
Diquatusagein1980wasestimatedtobe200,000lbs. disappears from the water in 2-4 weeks. Diquat will
•f active ingredient. 1982 data indicates that diquat was Photodegrade in surface layers of water in 1-3 or more
not produced domestically, but imports were nearly weeks when not adsorbed to part.culate matter.
835,000 Ibs. In 1982 it was estimated that diquat usage Should diquat be released to the atmosphere during
October 1995 Technical Version Printed on Recycled Paper
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spraying operations, it would be associated with aero-
sols. It will be subject to photolysis (half-life approx 48
hrs) and gravitational settling.
Little or no bioconcentration in fish will occur, as is
expected for a chemical whose log octanol/water parti-
tion coefficient is -3.05. No residues were detected in
organs or tissues of channel catfish collected from pools
5 months after a single application or 2 months after a
second treatment of 1 ppm diquat.
Human exposure will principally be by agriculture
workers or others who use the chemical or are in the
vicinity of fields or bodies of water where diquat is used.
OTHER REGULATORY INFORMATION
MONITORING:
FOR GROUND/SURFACE WATER SOURCES:
INITIAL FREQUENCY- 4 quarterly samples every 3 years
REPEAT FREQUENCY- If no detections during initial round:
2 quarterly per year if serving >3300 persons;'
1 sample per 3 years for smaller systems
TRIGGERS - Return to Initial Freq. if detect at > 0.0004 mg/L
ANALYSIS:
REFERENCE SOURCE METHOD NUMBERS
EPA 600/4-88-039 549.1
TREATMENT:
BEST AVAILABLE TECHNOLOGIES
Granular Activated Charcoal
FOR ADDITIONAL INFORMATION:
* EPA can provide further regulatory and other general information:
• EPA Safe Drinking Water Hotline - 800/426-4791
* Other sources of lexicological and environmental fate data include:
• Toxic Substance Control Act Information Line - 202/554-1404
• Toxics Release Inventory, National Library of Medicine - 301/496-6531
• Agency for Toxic Substances and Disease Registry - 404/639-6000
• National Pesticide Hotline - 800/858-7378
October 1995
Technical Version
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