E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Publication Date: 9/95
TRADE OR OTHER NAMES
Endothall is endothal in Great Britain. Trade names for the acid form of
endothall (technical endothall) include Aquathol, Hydrothal-47 and Hydrothal-
191. Trade names for the disodium salt of endothall (disodium endothall)
include Accelerate, Des-I-Cate, Tri-endothal, Ripenthol, Hydrothol, and
Niagrathol (4, 5, 6). The amine salt of endothall is also called Hydrothol
Endothall is a general use pesticide (GUP). When used as an aquatic
herbicide, some water use restrictions may apply (2).
Endothall is a member of the dicarboxylic acid chemical class (7, 8). It
is a selective contact herbicide. The potassium and amine salts of endothall
are used as aquatic herbicides to control a variety of plants including
plankton, pondweed, niad, coontail, milfoil, elodea, and algaes in water
bodies and rice fields. Endothall is also used to control annual grass and
broadleaf weeds in sugar beets, spinach and turf. It reduces sucker branch
growth in hops. Endothall is a desiccant to aid the harvest of alfalfa,
potatoes, clover, and cotton (4). The EPA has classified endothall as Toxicity
Class II - moderately toxic. Products containing endothall bear the SIGNAL
WORD: WARNING (9). It is available as granules or as a soluble concentrate
Endothall is moderately toxic. The LD50 is the dose which kills half of
the test animals treated. The oral LD50 for disodium endothall is 51 mg/kg for
rats and 250 mg/kg for guinea pigs (3, 5). The LD50 is 750 mg/kg for rats and
100 mg/kg for rabbits whose skin is exposed to disodium endothall (3, 10, 11).
In humans, ingestion of 7 to 8g of disodium endothall causes repeated
vomiting, hemorrhages, swelling in the lungs, and bleeding in the
gastrointestinal tract (12).
The LD50 for the amine salt of endothall is 206 mg/kg for rats and 143
mg/kg for rabbits whose skin is exposed to it (3, 4). The oral LD50 for
technical endothall is 38 mg/kg for rats. Endothall is very irritating to the
eyes, skin, and mucous membranes (3, 4, 7).
A three generation study was conducted by feeding male and female rats
disodium endothall until they were 100 days old and then mating them. Three
successive generations were maintained on the test diet for 100 days and then
bred to produce the next generation. When examined at 21 days, rat pups in all
three generations whose parents were given 15 mg/kg/day of disodium endothall
had decreased body weights. No adverse reproductive effects were observed
(NOEL) at 5 mg/kg/day (12).There were no observable signs of developmental
toxicity at dose levels that were fatal to the females (12).
Technical endothall was not teratogenic at the highest dose tested, 30
Studies show that technical endothall is not mutagenic in Salmonella
bacteria nor in mouse cells. Aquathol K, a formulation of dipotassium
endothall, is not mutagenic in fruit flies, mold, or human white blood cells.
However, "commercial endothall," with no further description, was mutagenic in
fruit flies (12).
No statistically significant numbers or types of tumors were observed in
rats fed as much as 125 mg/kg/day of disodium endothall for two years. Thus,
available evidence suggests that endothall does not cause cancer (12).
In male dogs, high doses of 20 mg/kg/day of disodium endothall for 6
weeks caused vomiting, diarrhea, damaged intestinal walls, and hemorrhages in
the stomach. In rats, very high doses of 50 mg/kg/day of disodium endothall
for four weeks caused liver and kidney damage (12).
Fate in Humans and Animals
In rats dosed with technical endothall, over 95% of the dose was excreted
within 48 hours. Within 72 hours after dosing, 99% of the dose was excreted.
Approximately 90% of a dose of technical endothall is excreted in the feces
and 7% in urine (12).
Effects on Birds
No information is currently available.
Effects on Aquatic Organisms
Endothall is toxic to some species of fish (4). Inorganic salts of
endothall in aquatic formulations are safe to fish in 100-500 ppm
concentrations. However, amine salts of endothall are more toxic to fish than
the dipotassium endothall (17). Endothall has a low toxicity to crustaceans
and a medium toxicity to aquatic insects (6). Long-term ingestion may cause
severe damage to the digestive tract, liver and testes in fish (13).
Effects on Other Animals (Nontarget species)
Endothall is not toxic to bees (4).
Breakdown of Chemical in Soil and Groundwater
Endothall is highly mobile in soil, however rapid degradation limits the
extent of leaching. Endothall disappears from soil in 7-21 days (4). The half-
life, the amount of time needed for the concentration to be reduced by half,
of endothall in soil is 4-5 days in clay soils and 9 days in soils with high
organic content (14).
Breakdown of Chemical in Surface Water
Endothall is rapidly degraded in water (4, 15). Its half-life is 4 to 7
days for dipotassium endothall and about 7 days for technical endothall in
surface water (17). It biodegrades more slowly when air is not present (14).
Breakdown of Chemical in Vegetation
No information is currently available.
PHYSICAL PROPERTIES AND GUIDELINES
Technical endothall is a colorless or white crystal which is stable to
light, weak acidic media and weak alkaline media. It is stable to temperatures
up to about 90 degrees C. Above that temperature, it undergoes a slow
conversion to anhydride. When heated to decomposition, endothall emits acrid
smoke and fumes (3). Because it is a dibasic acid, it forms amine and alkali
All properties are for technical endothall unless otherwise noted.
|CAS #:||145-73-3 (technical endothall)
129-67-9 (disodium salt of endothall)
6385-60-0 (amine salt of endothall)
|Chemical names:||3,6-endoxohexahydrophthalic acid (technical endothall)
Disodium-3,6-endoxohexahydrophthalate (disodium endothall)
3,6-endoxohexahydrophthalic acid amine salt (amine salt of endothall)
|Solubility in water:||100 g/kg at 20 degrees C (4, 14)
|Sulubility in other solvents:||Soluble in benzene, isopropanol, acetone, dioxane, and methanol (disodium salt of endothall and technical endothall) (4)
|Melting point:||144 degrees C (4)
|Log octanol/water partition coefficient:||-0.87 (14)
All guidelines are for technical endothall unless otherwise noted.
|ADI:||0.02 mg/kg (12)
|HA (lifetime):||0.8 mg/l (12)
|NOAEL:||0.08 mg disodium endothall/kg/day (dog) (12)
|RfD:||0.02 mg/kg/day (12)
|MCL:||0.1 mg/l (15)
|MCLG:||0.1 mg/l (15)
ELF Atochem, North America
Three Parkway, Room 619
Philadelphia, PA 19102
Review by Basic Manufacturer:
Comments solicited: October, 1994
National Institute for Occupational Safety and Health (NIOSH). 1979.
Registry of Toxic Effects of Chemical Substances (RTECS). NIOSH. Cincinnati,
U.S. Department of Health and Human Services. 1993. Hazardous
Substance Data Base. HHS. Washington, DC.
Sax, N.I. 1984. Dangerous Properties of Industrial Materials, Sixth
edition. Van Nostrand Reinhold. NY, NY.
The Agrochemicals Handbook, Third Edition. 1994. Royal Society of
Chemistry Information Systems, Unwin Brothers Ltd., Surrey, England.
Meister, R.T. 1992. Farm Chemicals Handbook '92. Meister Publishing
Company. Willoughby, OH.
Briggs, Shirley. 1992. Basic Guide to Pesticides. Hemisphere
Publishing. Washington, DC.
Bohmont, Bert. 1981. The New Pesticide Users Guide. B & K Enterprises.
Fort Collins, CO.
Thomson, W.T. 1982. Agricultural Chemicals, Book II Herbicides.
Thomson Publications. Fresno, CA.
Meister, R.T. 1994. Farm Chemicals Handbook '94. Meister Publishing
Company. Willoughby, OH.
Hayes Jr., W. R. and E.R. Laws, Jr. (eds.) 1991. Handbook of Pesticide
Toxicology Volume 1. Academic Press, Inc. New York, NY.
Ware, G.W. 1986. Fundamentals of Pesticides - A Self Instruction
Guide, Second edition. Thomson Publications. Fresno, CA.
U.S. Environmental Protection Agency. Office of Drinking Water. 1987.
Endothall Health Advisory. USEPA. Washington, DC.
R.E. Gosselin. 1984. Clinical Toxicology of Commercial Products,
Section II. p.32. William Watkins. Baltimore, MD.
Howard, Phillip (ed.). 1991. Handbook of Environmental Fate and
Exposure Data for Organic Chemicals Volume 3 Pesticides. Lewis Publishers.
U.S. Environmental Protection Agency Office of Water. 1994. National
Primary Drinking Water Standards. EPA 810-94-001A. Washington, DC.
U.S. Environmental Protection Agency. 1992. Accession no. 252010,
document # 005257. USEPA. Washington, DC.
Reinert, K.H. and J.H. Rodgers. 1987. Fate and Persistence of Aquatic
Herbicides. Springer Verlag. New York, NY.