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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 (1, 211, 226). The
amine salt of endothall is also called Hydrothol (22).
REGULATORY STATUS: Endothall is a general use pesticide (GUP). When used as an aquatic herbicide, some water
use restrictions may apply (307).
INTRODUCTION: Endothall is a member of the dicarboxylic acid chemical class (308,207). 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 (1). The EPA has classified endothall as
Toxicity Class II - moderately toxic. Products containing endothall bear the SIGNAL WORD: WARNING (223).
FORMULATION: It is available as granules or as a soluble concentrate (1).
- Acute Toxicity: 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 (31, 211). The LD50 is 750 mg/kg for
rats and 100 mg/kg for rabbits whose skin is exposed to disodium endothall (31, 227, 309). In humans, ingestion of 7 to
8g of disodium endothall causes repeated vomiting, hemorrhages, swelling in the lungs, and bleeding in the
gastrointestinal tract (310). 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 (31, 1). The oral LD50 for technical endothall is 38 mg/kg for rats. Endothall is very irritating
to the eyes, skin, and mucous membranes (31, 1, 308).
- Chronic Toxicity: Information follows.
- Reproductive Effects: 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 (310).There were no observable signs of developmental toxicity at dose levels
that were fatal to the females (310).
- Teratogenic Effects: Technical endothall was not teratogenic at the highest dose tested, 30 mg/kg/day (310).
- Mutagenic Effects: 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 (310).
- Carcinogenic Effects: 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
- Organ Toxicity: 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 (310).
- 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(310).
- Effects on Birds: No information is currently available.
- Effects on Aquatic Organisms: Endothall is toxic to some species of fish (1). 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 (312). Endothall has a low toxicity to crustaceans and a medium toxicity to aquatic
insects (226). Long-term ingestion may cause severe damage to the digestive tract, liver and testes in fish (30).
- Effects on Other Animals (Nontarget species): Endothall is not toxic to bees (1).
- 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 (1). 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
- Breakdown of Chemical in Surface Water: Endothall is rapidly degraded in water (1, 65). Its half-life is 4 to 7 days
for dipotassium endothall and about 7 days for technical endothall in surface water (312). It biodegrades more slowly
when air is not present (9).
- Breakdown of Chemical in Vegetation: No information is currently available.
PHYSICAL PROPERTIES AND GUIDELINES
Physical Properties: All properties are for technical endothall unless otherwise noted.
- Appearance: Technical endothall is a colorless or white crystal which is stable to light, weak acidic media and weak
- Chemical Name: 3,6-endoxohexahydrophthalic acid (technical endothall),Disodium-3,6-endoxohexahydrophthalate
(disodium endothall), 3,6-endoxohexahydrophthalic acid amine salt (amine salt of endothall)
- CAS Number: 145-73-3 (technical endothall), 129-67-9 (disodium salt of endothall), 6385-60-0 (amine salt of
- Molecular Weight: 186.2
- Water Solubility: 100 g/kg at 20 degrees C (1, 9)
- Solubility in Other Solvents: Soluble in benzene, isopropanol, acetone, dioxane, and methanol (disodium salt of
endothall and technical endothall) (1)
- Melting Point: 144 degrees C (1)
- Vapor Pressure: 2.09 x 10-5 mPa (24.3 degrees C)
- Partition Coefficient: Not Available
- Adsorption Coefficient: -0.87 (9)
Exposure Guidelines: All guidelines are for technical endothall unless otherwise noted.
- ADI: 0.02 mg/kg (310)
- MCL:0.1 mg/l (65)
- RfD: 0.02 mg/kg/day (310)
- PEL: Not Available
- HA: 0.8 mg/l (310)
- TLV: Not Available
ELF Atochem, North America
Three Parkway, Room 619
Philadelphia, PA 19102
References for the information in this PIP can be found in Reference List Number 10
DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide
product label/ing or other regulatory requirements. Please refer to the pesticide product label/ing.