SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 145733
CASRN 145-73-3
SynonymsEndothall
Endothal
7-Oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid,
Analytical Method EPA Method 548.1
Molecular FormulaC8H10O5

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use It is used as a desiccant on lucerne and on potato, for the defoliation of cotton and to control algae and aquatic weeds. Pre- and post-emergence herbicide, defoliant, desiccant, aquatic algicide growth regulator. For sugar beets, turf, hops sucker suppression; alfalfa, clover desiccants; cotton harvest aids; potato vine killers. SALTS OF ENDOTHAL ARE RECOMMENDED FOR PRE- & POST-EMERGENCE CONTROL OF WEEDS IN RED BEET, SPINACH AND SUGAR BEET AT 2-6 KG AI/HA OR IN COMBINATION WITH PROPHAM. USED AS DESICCANT ON LUCERNE & ON POTATO, FOR DEFOLIATION OF COTTON & TO CONTROL AQUATIC WEEDS & ALGAE.
Consumption Patterns Cotton production, 95.6%; Sugarbeets, 3.9%; Remainder in landscape maintenance or "public health pest control" (1984) California use, calculated from table
Apparent Color CRYSTALLINE, WHITE SOLID
Odor Odorless
Melting Point WHEN HEATED RAPIDLY, MELTS @ ABOUT 144 C, DECOMPOSING INTO ANHYDRIDE & WATER
Molecular Weight 186.18
Density 1.431
Sensitivity Data May be very irritating to skin, eyes, mucous membranes.
Environmental Impact 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. 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. Chemical hydrolysis and volatilization are not expected to be significant. If released to water, endothall should rapidly biodegrade under aerobic conditions (half-life approx 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, bioaccumulate or adsorb to suspended solids or sediments in water. 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 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.
Environmental Fate TERRESTRIAL FATE: If released to soil, endothall is expected to rapidly biodegrade under aerobic conditions. The half-life of endothall is reported to be 4 to 5 days in clay soils and 9 days in soils with high organic content . Endothall should be highly mobile in soil; however, rapid degradation would limit the extent of leaching. Chemical hydrolysis and volatilization are not expected to be significant fate processes. AQUATIC FATE: If released to water, endothall should rapidly biodegrade under aerobic conditions (half-life approx 1 week or less). Glutamic acid is a major biotransformation product of endothall under aerobic conditions. Endothall is not expected to oxidize, chemically hydrolyze, photolyze, volatilize, bioaccumulate or adsorb to suspended solids or sediments. Endothall applied to a pond at various concentrations ranging from 0.3 to 10 ppm was undetectable after an average of 2.5 days and a maximum of 4 days and in another study, 1.2 ppm endothall added to pond water was 55% removed after 12 days . In experimental greenhouse pools treated with 0.03, 1.6 or 4.5 ppm endothall, an overall half-life of 4 days was reported . In farm reservoirs, approx 71% removal of 0.3 to 1.4 ppm endothall was observed in 12 days . Endothall added to the water of irrigation supply ponds at 2 ppm decreased linearly with the predicted concentration of zero at 26 days (half-life 12 days) . 30 days after addition of endothall to anoxic water, only 28% removal of added endothall was observed . ATMOSPHERIC FATE: If released to the atmosphere, endothall is expected to exist predominantly on particles and should either settle out or wash out in precipitation. Endothall is not expected to chemically react or photolyze in the atmosphere. A mixture of diquat dibromide and potassium endothall was applied at 2.83 liters of each chemical per 0.4 surface acre to the 1093 acre Chickahominy Reservoir, Virginia because of nuisance populations of Egeria densa Planchon (egeria). There were no measurable changes in water quality after treatment and macrophyte die off with the exception of a general decrease in dissolved oxygen. Both herbicides declined to very low levels in the water 3 days after treatment and were undetectable within 16 days after treatment. No endothall was found in bottom sediments. Neither was found in fish muscle tissue. To obtain residue data from the application of the algicide endothal in Italian rice paddy fields, 2 experiments were carried out using a 50 g/kg granular formulation in a small pond and the same granular and liquid formulations in actual paddy fields of the Italian rice growing area. Endothal decay in the pond water was very rapid, reaching residue levels of 0.01-0.02 mg/l in 2 days and 0.004-0.01 mg/l at the third day. The muddy soil of the pond was free from measurable endothal residues (<0.02 mg/kg). In the paddy field waters, the endothal decay was slower, with an average half-life time of 3.3 days, independently of the type of formulation. The actual residues in water after 6 days ranged from 0.3 to 1.3 mg/l according to the initial amount of product applied, and, consequently, to the initial concn in water. Rice samples collected at the normal harvest time from the two paddy fields, treated with three different formulations, showed no endothal residue at the min. detectable level of 0.01 mg/kg. Accurate prediction of chemical fate and persistence using general aquatic fate models requires model parameterization, ie, the determination of site-specific environmental and chem parameters for model input. The capability of 1 model, the Exposure Anal Modeling System (EXAMS), to predict the fate of endothall, an aquatic herbicide, in a reservoir was compared using 2 different parameterization methods. The 1st method, limited parameterization, used only literature and limited field data. The 2nd method, intensive parameterization, employed lab, expterimental pool and field data. Differences of <1 order of magnitude were observed among theendothallfate predictions from Exposure Anal Modeling System in this reservoir using either method. Predicted endothall aq half-lives were greater than the observed half-life by a factor of 5 to 9. Predicted endothall concn in sediment were consistently below the min detectable level (0.01 mg/kg) for endothall, whereas endothall concn were measured in reservoir sediments in the field. In this case, the results indicate that limited parameterization of Exposure Anal Modeling System provides predictions of endothall persistence that are as accurate as those provided by intensive parameterization, thus saving time and reducing costs. Limited parameterization produced relatively accurate predictions in this study, possibly because only 1 fate process, biotransformation, was important. For chemicals affected by numerous fate processes, the errors associated with each fate process input could significantly affect the accuracy of predictions.

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