SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 314409
CASRN 314-40-9
SynonymsBromacil
5-Bromo-3-sec-butyl-6-methyluracil
Borea
Bromax
Urox 'B'
Analytical Methods EPA Method 633
EPA Method 8321
Molecular FormulaC9H13BrN2O2

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

Use Bromacil is used primarily for the control of annual and perennial grasses and broadleaf weeds, both nonselectively on noncrop lands and selectively for weed control in a few crops (citrus and pineapple). It appears to act in plants by inhibiting photosynthesis and to be primarily absorbed through the roots. BROMACIL IS A NON-SELECTIVE INHIBITOR OF PHOTOSYNTHESIS & RECOMMENDED FOR GENERAL WEED CONTROL ON NON-CROP LAND @ 5-15 KG ACTIVE INGREDIENT/HA; FOR SUBSEQUENT ANNUAL MAINTENANCE 2-4 KG/HA IS ENOUGH. IT MAY ALSO BE USED FOR ANNUAL WEED CONTROL IN ESTABLISHED CITRUS PLANTATIONS @ 1.6-3.2 KG/HA; FOR PERENNIAL GRASSES & ANNUAL WEEDS AT 3.2-8.0 KG/HA; IN PINEAPPLE PLANTATIONS AT 1.8-5.5 KG/HA. AT HIGHER RATES ITS EFFECT USUALLY PERSISTS FOR MORE THAN ONE SEASON. Total weed and brush control on non-crop land; and selective control of annual and perennial weeds and grasses in citrus and pineapple plantations. For selective control of annual and perennial weeds in orange, grapefruit, and lemon orchards .
Consumption Patterns APPROX 77% FOR INDUSTRIAL/COMMERCIAL USE AS AN HERBICIDE; APPROX 13% FOR AGRICULTURAL USE AS AN HERBICIDE; AND APPROX 10% FOR GOVERNMENT AGENCY USE AS AN HERBICIDE (1972)
Apparent Color WHITE CRYSTALLINE SOLID; Colorless crystals
Odor ODORLESS
Melting Point 157.5-160 DEG C
Molecular Weight 261.11
Density 1.55 @ 25 deg C/25 deg C
Environmental Impact Bromacil's use as a contact herbicide releases the compound directly to the environment through applications in sprays and other routes of application. If released to the atmosphere, bromacil will degrade rapidly in the vapor phase by reaction with photochemically produced hydroxyl radicals (half-life of about 7.6 hr). Particulate phase bromacil will be removed physically from air by wet and dry deposition. If released to soil or water, bromacil can slowly biodegrade. Rapid photo-sensitized photodegradation may occur in natural waters containing sufficient concns of sensitizing agents. Numerous Koc measurements, which typically range between 20 and 130, indicate that bromacil can be highly mobile in soil. Bromacil's detection in ground waters demonstrates that leaching can occur. Results of various persistence studies indicate that bromacil is relatively persistent in soil. The US Dept of Agric's Pesticide Properties Database lists a soil half-life of 60 days for bromacil, but it may typically range from 2 to 8 months. Occupational exposure to bromacil occurs through dermal contact and inhalation of sprays, especially to workers applying the compound as a herbicide.
Environmental Fate IN LAB STUDIES, 25-30% OF HERBICIDE APPLIED TO SOIL WAS LOST AS CO2 IN 6-9 WK. At 18 mo after spraying 22.4 kg bromacil/ha on abandoned field sites overgrown mainly by little bluestem (Andropogon scoparius), poverty grass (Danthonia spicata), timothy (Phleum pratense), quackgrass (Agropyron repens), goldenrod (Solidago) and Kentucky bluegrass (Poa pratensis), the max recovery of detectable bromacil residues occurred in the loamy sand, followed by decr amt in the silt loam, silty clay loam, and light silty clay loam. Org matter content, cation-exchange capacity, total nitrogen and sol salt concn were significantly correlated with residue persistence and incr depth in all 4 soils. TERRESTRIAL FATE: BROMACIL WAS INCUBATED IN VARIOUS SOILS TO DETERMINE ITS PERSISTENCE. HALF-LIFE IN FLOODED SOIL WAS 155 DAYS; IN FLOODED SOIL PLUS BEAN STRAW, 198 DAYS. TERRESTRIAL FATE: Duration of residual activity in soil is approx 7 months. TERRESTRIAL FATE: When sterilant rates are applied, activity usually is noted for more than one season. The half life of 2-(14)C-labeled bromacil was determined to be approximately 5 to 6 months when 4 lb/A were applied to the surface of Butlertown silt loam. TERRESTRIAL FATE: Results of screening studies have demonstrated that bromacil degrades primarily through microbial degradation in soil(1-3). Losses from soil due to photodecomposition or volatilization are minor(3-4). Measured Koc values, which typically fall in a range from 20 to 130(5-10), indicate that bromacil can be highly mobile in soil. In one adsorption study, it was determined that a rainfall of 20-23 cm could displace over 96% of applied bromacil(9). Bromacil's detection in ground waters demonstrates that leaching can occur(11). TERRESTRIAL FATE: Bromacil is relatively persistent in soil. The US Dept of Agric's Pesticide Properties Database lists a soil half-life of 60 days for bromacil . In a laboratory study using a sandy loam soil and saturated soil conditions, bromacil had an observed half-life of 144-198 days . In an apple orchard study where bromacil was applied annually for 6-7 yrs, bromacil had an apparent half-life of approximately 8 months . In field plots treated with 4 lb bromacil per acre, bromacil had a half-life of 5 to 6 months ; identified metabolites included 5-bromo-3-sec-butyl-6-hydroxymethyl uracil, 5-bromo-3-(2-hydroxy-1-methylpropyl)-6-methyluracil, and 5-bromo-3-(3-hydroxy-1-methylpropyl)-6-methyluracil . Degradation of 31-65% was observed in six soils after incubation for 6 months under laboratory conditions . Laboratory half-lives of 4-5 months were determined for a loam soil at temperatures of 13.2 and 31.2 deg C(6); faster degradation occurred at warmer temperatures(6). AQUATIC FATE: Bromacil may degrade in natural water through microbial degradation and photo-sensitized degradation. Biodegradation is a major fate process in soil . In a laboratory study, bromacil was debrominated under methanogenic conditions in aquifer slurries ; 100% degradation occurred after 160 days of incubation ; almost no degradation occurred in sterile controls . Bromacil has been observed to undergo a rapid photosensitized photolysis in sunlight in the presence of photosensitizers such as methylene blue or riboflavin(3-7); the sensitized degradation rate generally increases with an increase in the pH(6); in one study using riboflavin and methylene blue(6), about 10-15% of initial bromacil degraded at pH 7 with 30-min irradiation period(6); at pH 10, 80-90% was degraded(6); no degradation occurred in the absence of the sensitizers(6). The rate of photodegradation in natural water could vary dramatically depending upon concn of sensitizing agents and sunlight intensity. Aquatic volatilization, bioconcentration and adsorption to sediment are not expected to be important fate processes. ATMOSPHERIC FATE: Based upon a reported vapor pressure of 2.5X10-7 mm Hg at 25 deg C , bromacil can exist in both the vapor and particulate-phases in the ambient atmosphere(2,SRC). It will degrade rapidly in the vapor-phase by reaction with photochemically produced hydroxyl radicals with an estimated half-life of about 7.6 hr(3,SRC). Particulate-phase bromacil and aerosols released to air during applications of bromacil herbicides will be removed from air physically by dry and wet deposition.
Drinking Water Impact GROUNDWATER: According to an interim report of the USEPA's Groundwater Data Base, bromacil has been detected in groundwaters from NY and CA at a max concn of 22 ppb and a median concn (of positive detections) of 9 ppb . Monitoring analyses of 10,929 wells in CA during 1975 to 1989 detected bromacil (detection limit and concns not reported) in 4 wells . As of June 1984, bromacil was not detected (detection limit not reported) in a Wisconsin monitoring study that had analyzed 1508 samples from 358 wells . A bromacil ground water concn of 300 ppb has been reported for an unnamed FL site . Max bromacil concns of 1.25 ppm were detected in groundwater (depths of 4.5-6 meters) three months after the herbicide was applied to a surface of Lakeland, FL sandy soil bearing scrub vegetation of small oaks and poor grasses . Bromacil concns of 30 to 147 ug/L have been reported for upper ground water samples collected in West Germany(7); concns of <0.1-1.8 ug/L were reported for water samples from bore holes (15-40 m deep) in three provinces in the Netherlands(6). In a 1979-1984 analysis of 7 wells in Ontario, Canada that were in the vicinity of bromacil herbicide use, bromacil was detected (detection limit 0.1 ug/L) in only well(7).

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