SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 330552
CASRN 330-55-2
SynonymsLinuron
Urea, N'-(3,4-dichlorophenyl)-N-methoxy-N-methyl-
Afalon
Lorox
Linex
Linurex
1-Methoxy-1-methyl-3-(3,4-dichlorophenyl)urea
Analytical Methods EPA Method 553
EPA Method 632
Molecular FormulaC9H10Cl2N2O2

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

Use Selective herbicide recommended for pre-emergence use in asparagus, beans, cotton, maize, peas, potatoes, soyabeans, and for pre-emergence or post-emergence use in carrots and winter wheat. Controls germinating and newly established broadleaf weeds and grasses in crops such as sorghum, wheat (Pacific Northwest only), celery and parsnips. It is also used for short-term control of annual weeds in noncropland areas such as roadsides and fence rows. With a suitable surfactant as a directed spray in certain crops, it controls weeds up to 5 inches high; without surfactant as a non-directed postemergence spray in carrots, it controls emerged grasses up to 2 in and broadleaf weeds up to 6 in high. Control of annual grass and broad-leaved weeds, and some seedling perennial weeds in artichokes parsley, fennel herbs and spices celeriac, onions, leeks, garlic field beans cereals sorghum flax, sunflowers, sugar cane, ornamentals, established vines, bananas, cassave, coffee, tea, rice, groundnuts, ornamental trees and shrubs, and other crops.
Apparent Color WHITE CRYSTALLINE SOLID; COLORLESS CRYSTALS; Fine flakes or coarse powder
Odor ODORLESS
Melting Point 93-94 DEG C
Molecular Weight 249.11
Sensitivity Data MAY IRRITATE EYES, NOSE, THROAT, & SKIN.
Environmental Impact Linuron, 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea, may be released to the environment during its application as a herbicide on soybean, carrots, cotton, potatoes, carrots, and celery. Releases will be primarily to soil, although releases to water may occur from spills or runoff. Releases may also occur during production, formulation, preparation for spraying, cleanup, transport, and storage. Linuron is strongly adsorbed to soil and will generally remain in the upper 2.5 cm of soil and should photolyze on the soil surface. In most soils, at normal application rates, linuron degrades within 3-4 months. Linuron residues do not accumulate in soil and progressive buildup of residues is not observed after repeated treatment. If released in water, linuron will adsorb to sediment and particulate matter in the soil column and photolyze in surface waters. Bioconcentration in fish is minimal. In the atmosphere, linuron will exist predominantly as the vapor and degrade by reaction with photochemically produced hydroxyl radicals with an estimated half-life of 11.4 hr. Human exposure will be primarily occupational. Occupational exposure will be by inhalation and dermal contact and most generally would occur during formulation and application of the herbicide and by touching soil and vegetation that were sprayed. The general population may be exposed to linuron by ingesting contaminated vegetables, primarily carrots.
Environmental Fate ACCUM FROM ANNUAL APPLICATIONS TO THE SAME SOIL IS NOT A PROBLEM. Terrestrial fate: Movement by leaching is least in soils high in clay and/or organic matter; greatest in sand. Bioassays of oats have shown no significant soil residues 3 to 4 months after treatment at selective rates, and fall-sown cover crops have grown normally. Half-life under field conditions is 2 to 5 mo. TERRESTRIAL FATE: When applied to soil, linuron will adsorb moderately strongly and remain primarily in the upper 2.5 cm of the soil. It should photolyze on the soil surface. Loss due to biodegradation will also occur and will increase with increasing organic matter and moisture content of the soil and temperature(1,3,5). In most soils, at normal application rates, linuron degrades within 3-4 months . The dissipation of linuron was followed in field plots planted with potatoes and treated with linuron at 1 and 2 kg/ha . The disappearance of linuron was very fast and followed first order kinetics with a half life of 25 and 22 days, respectively, at the two application rates . After about 75 days, the residual concn of linuron in the soil was constant, suggesting that a small amount of linuron is strongly adsorbed to soil colloids and not available to microbial attack . In test field plots in an onion growing area of Ontario, 64% of linuron had dissipated in 5 months from the organic soil (92% organic matter) . It was concluded that linuron residues did not accumulate in soil in onion farms of area growers . TERRESTRIAL FATE: The half-life of linuron in cropped fields was 8-25 weeks; residues were undetectable after 6 mo(1-2). No progressive buildup was observed after repeated treatment(1-2). Four weeks after a half normal, normal, and double normal spray of linuron in May on corn, carrots, bean and potato crops planted in loamy soil, an average of 40% of the applied dose was recovered . After 3 months, only 25% of the linuron was recovered . At the end of the winter months, <0.4% of the linuron was recovered . In Greenhouse experiments linuron's persistence was 25-60 weeks . AQUATIC FATE: If released in water, linuron will adsorb to sediment and particulate matter in the water column. Linuron biodegrades in soil and therefore would be expected degrade in aerobic sediment. Linuron degrades in anaerobic sediment, although no degradation rates are available . Photolysis will occur in surface waters. In one experiment, 43% of linuron exposed to sunlight outdoors was photolyzed in 24 days . While linuron biodegrades in soil, no linuron biodegraded when incubated with river water and sewage for 4 months . Linuron would not be expected to volatilize or hydrolyze. Bioconcentration in aquatic organisms should be minimal. After linuron (1 ppm) was added to each of three 1 cu m outdoor ecosystems, linuron concns in the water columns declined exponentially over the 42-day experiment; the calculated half-lives ranged from 16 to 42 days . It was not determined what happened to the linuron. The half-life of linuron in Lake Balatan (Hungary) water was 10 weeks . ATMOSPHERIC FATE: In the atmosphere, linuron will primarily exist in the vapor phase . In the vapor phase, it will degrade by reaction with photochemical-produced hydroxyl radicals with an estimated half-life of 11.4 hours . It will also undergo direct photolysis, although there are no data as to how fast photolysis might proceed in air.
Drinking Water Impact GROUNDWATER: In a survey of 201 rural wells in 8 agricultural areas of Missouri, linuron was found in 2 wells at 1.8 and 1.9 ppb . These wells were located in areas planted with soybeans. Sampling was performed in December. According to EPA's Pesticides in Groundwater database, linuron has been found only in Wisconsin groundwater; the contamination was judged to result from normal agricultural use . The concn median and maximum were 1.9 and 2.7 ppb, respectively . In a 1986-1987 study of 179 farm wells in Ontario with suspected contamination, 28 wells contained linuron above the 0.1 ppb detection limit . In a British study in which 700 samples of rivers, reservoirs and groundwaters were analyzed, linuron was not detected in any groundwater(DL 0.2 ug/l) . SURFACE WATER: The concn of linuron was monitored at 7 stations on Lake Erie tributaries draining agricultural watersheds from 1983 to 1991, during which time over 4000 samples were analyzed . The maximum and 95th percentile linuron concns at these stations ranged from 1.36-24.77 ppb and 0.27-2.07 ppb, respectively . The time-weighted average and flow-weighted average concns ranged from 0.04-0.17 ppb and 0.00-0.20 ppb . Twenty five water samples taken from 4 Michigan rivers during runoff season, from April to September 1985, and analyzed for linuron were above the detection limit and linuron levels ranged from 0.146-2.813 ppb . While linuron is used on corn and soybean fields bordering Chesapeake Bay and its tributaries, including one in which an estimated 45,000 kg of linuron drains into the discharge basin, <0.2 ppb of linuron was found in 79 water samples from tributaries of Chesapeake Bay during two successive summers . A farm pond in Ontario contained 12 ppb of linuron that was attributed to runoff . EFFL: Runoff was collected after each rainfall or series of rainfalls from test plots (silty clay loam graded to a slope of 0.2%) planted with soybeans in the 2 to 4 month period following treatment with linuron as a preemergence herbicide. Concns of linuron in runoff in three years were: trace - 28 ppb, trace - 14 ppb, and trace - 124 ppb

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