Technical Factsheet on: ENDOTHALL
List of Contaminants
As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication:
National Primary Drinking Water Regulations
Drinking Water Standards
MCLG: 0.1 mg/L
MCL: 0.1 mg/L
HAL(child): 1 - to 10-day: 0.8 mg/L; Longer-term: 0.2 mg/L
Health Effects Summary
Acute: EPA has found endothall to potentially cause the following health effects from acute exposures at
levels above the MCL: depressed breathing and heart rate.
Drinking water levels which are considered "safe" for short-term exposures: For a 10-kg (22 lb.) child
consuming 1 liter of water per day, upto a ten-day exposure to 0.8, or up to a 7-year exposure to 0.2
mg/L.
Chronic: Endothall has the potential to cause the following health effects from long-term exposures at
levels above the MCL: increased organ weights and organ-to-body weight ratios of stomach and intestine.
Cancer: There is inadequate evidence to state whether or not endothall has the potential to cause cancer
from a lifetime exposure in drinking water.
Usage Patterns
Endothall is used as a defoliant for a wide range of crops and as a herbicide for both terrestrial and
aquatic weeds. It is used as a desiccant on lucerne and on potato, for the defoliation of cotton, to control
aquatic weeds and as an aquatic algicide growth regulator. It has been used for: sugar beets, turf, hops
sucker suppression; alfalfa, clover desiccants; potato vine killers.
EPA estimated total domestic usage in 1982 to have been approximately 1.5 million lbs. In California in
1984, 87,000 lbs. of the mono(N,N-diethylalkylamine) salt were used; 4,000 lbs. of the dimethylamine salt
were used; minor amounts of the dimethylalkylamine and dipotassium salts were used. Its estimated
applications in California were as follows: Cotton production, 95.6%; Sugarbeets, 3.9%; Remainder in
landscape maintenance or "public health pest control."
Release Patterns
Release of endothall to the environment is expected to occur primarily during its use as a pre-emergence,
post-emergence, turf and aquatic herbicide and harvest aid. Other sources of release include loss during
manufacturing, formulation, packaging or disposal of this herbicide.
Since endothall is not a listed chemical in the Toxics Release Inventory, data on releases during its
manufacture and handling are not available.
Environmental Fate

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If released to soil, endothall is expected to rapidly biodegrade under aerobic conditions. The half-life of
endothall in soil is reported to be 4 to 9 days. Endothall should be highly mobile in soil; however, rapid
degradation would limit the extent of leaching. Its persistence in soil may be prolonged by adsorption to
organic matter or by factors inhibiting microbial activity. Chemical hydrolysis and volatilization are not
expected to be significant.
If released to water, endothall should rapidly biodegrade under aerobic conditions (half-life approximately
1 week or less) and biodegrade more slowly under anaerobic conditions. Glutamic acid is a major
biotransformation product of endothall under aerobic conditions. Endothall is not expected to oxidize,
chemically hydrolyze, photolyze, volatilize or adsorb to suspended solids or sediments in water. The soil
adsorption coefficient (Koc) of endothall in sediment/water systems has been measured to be < 2.
If released to the atmosphere, endothall is expected to exist predominantly on particles and should either
settle out or wash out in precipitation. It is not expected to chemically react or photolyze in the
atmosphere.
The whole body bioconcentration factor (BCF) of endothall in bluegill (Lepomis macrochirus) has been
measured to be < 1. Based on a its water solubility, a BCF of < 1 has also been calculated. With these
BCF values, endothall is not expected to bioaccumulate in aquatic organisms.
The most probable routes of human exposure to endothall are inhalation and dermal contact of workers
involved in the manufacture, handling or application of endothall. The general public could potentially be
exposed through use for lawn weed control.
Chemical/ Physical Properties
CAS Number: 145-73-3
Color/ Form/Odor: Odorless, white crystals
M.P.: 144 C (decomposes)
Vapor Pressure: very low at room temp.
Octanol/Water Partition (Kow): N/A
Density/Spec. Grav.: 1.431 at 15 C
Solubility: 100 g/L of water at 20 C; Very soluble in water
Soil sorption coefficient: Koc <2; high mobility in soil
Odor/Taste Thresholds: N/A
Henry's Law Coefficient: N/A
Bioconcentration Factor: BCF <1 in fish; not expected to bioconcentrate in aquatic organisms.
Trade Names/Synonyms: Hexahydro-3,6-endo-epoxy-1,2-benzenedicarboxylic acid; Accelerate;
Aquathol; Des-i-cate; Endothall Turf Herbicide; Endothall Weed Killer; Herbicide 273; Hydrothol; Herbon
Pennout; Hydout.

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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 > 0.009 mg/L
Analysis:
Reference Source Method Numbers
EPA 600/4-88-039 548.1
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 toxicological 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

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