United States
Environmental Protection
Agency
Office of Water
4601
EPA811-F-95-003h-T
October 1995
National Primary Drinking
Water Regulations
2,4-D
CHEMICAL/ PHYSICAL PROPERTIES
CAS NUMBER: 94-75-7
COLOR/ FORM/ODOR:
Colorless, odorless powder; available
as soluble liquids, powder, dust,
aerosol spray (foam)
M.P.: 138° C B.P.: 160° C
VAPOR PRESSURE: 53 Pa at 160° C
. OCTANOL/WATER PARTITION (Kow):
Log Kow = 2.81
DENSITY/SPEC. GRAV.: 1.42at15°C
SOLUBILITY: 0.5 g/L of water at 20° C;
Slightly soluble in water
SOIL SORPTION COEFFICIENT:
Koc values are 19.6 to 109.1; low to
moderate mobility in soil
ODOR/TASTE THRESHOLDS: N/A
BlOCONCENTRATION FACTOR:
BCFs of 0.003 to 7 for various fish
and aquatic plants; not expected to
bioconcentrate in aquatic organisms.
HENRY'S LAW COEFFICIENT:
1.02x 10-* atm-cu m/mole;
TRADE NAMES/SYNONYMS: "Agent White",
Bladex-B, Brush Killer 64, Dicofur,
Dormon, Ipaner, Moxon, Netagrone,
Pielik, Verton 38, Mota Maskros,
Silvaprop 1, Agricom D, Acme LV4,
Croprider, Femesta, Lawn-Keep,
Pennamine D. Plantgard, Tributon,
Weed-B-Gon, Weedatul, Agroxone,
Weedar, Salvo, Green Cross Weed-No-
More 80, Red Devil Dry Weed Killer,
Scott's 4XD Weed Control, Weed-Rhap
LV40, Weedone 100, 2,4-
Dichlorophenoxyacetic acid
DRINKING WATER STANDARDS
MCLG: 0.07 mg/L
MCL: 0.07 mg/L
HAL(child): 1 day: 1 mg/L
10-day: 0.3 mg/L
HEALTH EFFECTS SUMMARY
Acute: EPA has found 2,4-D to potentially cause
nervous system damage from short-term exposures at
levels above the MCL.
Drinking water levels of 2,4-D which are considered
"safe" for short-term exposures: Fora 10-kg (22 Ib.) child
consuming 1 liter of water per day, a one-day exposure
of 1 mg/L, or a ten-day exposure to 0.3 mg/L.
Chronic: 2,4-D has the potential to cause damage to
the nervous system, kidneys and liver from long-term
exposure at levels above the MCL.
Cancer: There is inadequate evidence to state whether
or not 2,4-D has the potential to cause cancer from
lifetime exposures in drinking water.
USAGE PATTERNS
2,4-D is registered in the US as a herbicide for the
control of broad-leaf weeds in agriculture, and for control
of woody plants along roadsides, railways, and utilities
rights of way. It has been most widely used on such crops
as wheat and corn, and on pasture and rangelands.
Other uses of 2,4-D include brush control in forests, to
increase the latex output of old rubber trees, and as a
jungle defoliant. It may also be used as a plant growth
regulator to control fruit drop, such as on tomatoes to
cause all fruits to ripen at the same time for machine
harvesting.
Production of 2,4-D was steady: from 48.2 million Ibs.
Toxic RELEASE INVENTORY -
RELEASES TO WATER AND LAND:
1987 TO 1993
Water
TOTALS (in pounds) 3,444
Top Five States
HI 0
FL , 5
MO 1,817
Ml 822
TX 800
Major Industries
Cane sugar 0
Agri. chems. 2,616
Plastics, resins 696
Misc. manufact. 0
Gen. Chemical 126
Land
113,358
73,679
38,456
0
8
0
99,886
815
0
400
8
* Water/Land totals only include facilities with releases
greater than a certain amount - usually 1000 to 10,000 Ibs.
October 1995
Technical Version
Printed on Recycled Paper
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in 1978 to 45.1 million Ibs in 1982. 1991 data indicates
only that production exceeded 5000 Ibs. In 1991, it was
estimated that industries consumed 2,4-D as follows:
agriculture, 83 percent; for industrial/commercial uses,
11 percent; for lawns and turf, 3 percent; for aquatic uses,
3 percent.
RELEASE PATTERNS
Major environmental releases of 2,4-D are due to
agricultural applications of systemic herbicides. It is also
released as a result of the production or disposal of 2,4-
D or its by-products.
From 1987 to 1993, according to EPA's Toxic Chemi-
cal Release Inventory, 2,4-D releases to land and water
totalled over 116,000 Ibs., most of which was released to
land. These releases were primarily from cane sugar-
related industries (except refineries). The largest re-
leases (10% or more of the total) occurred in Hawaii.
especially at basic pH's. Its release to the air will also be
subject to photooxidation (estimated half-life of 1 day).
There is no evidence that bioconcentration of 2,4-D
occurs through the food chain. This has been demon;
strated by large-scale monitoring for 2,4-D residues
soils, foods, feedstuffs, wildlife, human beings, and from
examinations of the many routes of metabolism and
degradation that exist in ecosystems.
Human exposure, will be primarily to those workers
involved in the making and using 2,4-D compounds as
herbicides as well as those who work in and live near
fields sprayed and treated with 2,4-D compounds. Expo-
sure may also occur through ingestion of contaminated
food products and drinking water.
ENVIRONMENTAL FATE
There are a variety of microorganisms in soil, freshwa-
ter and marine ecosystems which are capable of degrad-
ing 2,4-D. If released on land, 2,4-D will probably readily
biodegrade (typical half-lives <1 day to several weeks).
Reported experimental (free acid) KOC values are
19.6 to 109.1. Adsorption appears to increase with
increasing organic content and decreasing pH of soil.
Leaching to groundwater will likely be a significant pro-
cess in coarse-grained sandy soils with low organic
content or with very basic soils. In general little runoff
occurs with 2,4-D or its amine salts and runoff behavior
is the inverse of adsorption behavior. Thus, 2,4-D can be
desorbed from mineraf soils, but not from those contain-
ing much organic matter.
Percolating water appears to be the principal means of
movement and diffusion is important only for transport
over very small distance. Upward movement of 2,4-D
occurs when the soil surface dries or if rapid evaporation
occurs. Thus, 2,4-D can be concentrated at the soil
surface, where it can be photolyzed, transported by wind
either on dust or in vapor form, or leached downwards
again.
If released to water, it will be lost primarily due to
biodegradation (typical half-lives 10 to >50 days). It will
be more persistent in oligotrophic waters and where high
concentrations are released. Degradation will be rapid in
sediments (half-life <1 day). Half-lives of 2-4 days were
reported for ultraviolet photolysis in water.
Volatilization of 2,4-D free acid from water and soil is
expected to be negligible based on its extremely low
reported Henry's Law constant (1.02X10-8 atm-cu ml
mole or less). It will not appreciably adsorb to sediments,
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 > 0.0005 mg/L
ANALYSIS:
REFERENCE SOURCE METHOD NUMBERS
EPA 600/4-88-039 515.1; 515.2; 555
TREATMENT:
BEST AVAILABLE TECHNOLOGIES
Granular Activated Charcoal
' \
FOR ADDITIONAL INFORMATION:
* EPA can provide further regulatory and other general information: •
• EPA Safe Drinking Water Hotline - 8007426-4791
4 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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