SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 140410
CASRN 140-41-0
SynonymsMONURON
1,1-Dimethyl-3-(Para-chlorophenyl)Urea; CNV-Weed-Killer; Rosuran; Karmex-W
Molecular FormulaC9H11C1N2O

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

UseThe only known use of monuron is as a broad-spectrum herbicide for the control of many grasses and herbaceous weeds on non-cropland areas, such as right-of-way, industrial sites and drainage ditch banks. AS A SOIL STERILANT MONURON IS PREFERRED ON MEDIUM TO HEAVY SOILS AND UNDER INTERMEDIATE RAINFALL CONDITIONS. AT STERILANT DOSAGES IT CONTROLS A WIDE RANGE OF ANNUAL AND PERENNIAL GRASSES AND BROADLEAF WEEDS ON NONCROP AREAS. /FORMER USE/ A plant growth regulator. ... Sugarcane flowering suppressant. 100% AS HERBICIDE FOR USE ON CROPS (1971)
Apparent ColorWhite plates from methanol
OdorOdorless solid
Boiling Point N/A
Melting Point 170.5-171.5 DEG C
Molecular Weight198.65
Misc NON-CORROSIVE DENSITY: 1.27 @ 20 DEG C/20 DEG C log Kow= 1.94 (est) PH: 6.26 SATURATED AQ SOLUTION SOLUBILITY: VERY SLIGHTLY SOL IN NUMBER 3 DIESEL OIL; MODERATELY SOL IN METHANOL, ETHANOL, PRACTICALLY INSOL IN HYDROCARBON SOLVENTS ; SLIGHTLY SOL IN OIL & POLAR SOLVENTS; Solubility (ppm): water 230 (@ 25 deg C), acetone 52,000 (@ 27 deg C), benzene 2900 (@ 27 deg C) ; Sol in benzene: 3 g/kg at 27 deg C MAX ABSORPTION: 247 NM ****; Intense mass spectral peaks: 72 m/z (100%), 198 m/z (19%), 73 m/z (7%), 200 m/z (6%) ****; IR: 10667 (Sadtler Research Laboratories Prism Collection) ****; UV: 20884 (Sadtler Research Laboratories Spectral Collection) ****; NMR: 16056 (Sadtler Research Laboratories Spectral Collection) ****; MASS: 161 (Aldermaston, Eight Peak Index of Mass Spectra, UK) VAP: 0.067 mPa @ 25 deg C COMMERCIAL PRODUCT MELTS @ 176-177 DEG C VAPOR PRESSURE: 178X10-5 MM HG @ 100 DEG C DECOMP @ 185-200 DEG C The rate of hydrolysis at room temp and pH 7 is negligible . Monuron-TCA is a crystalline solid; mp 78-81 deg C. Solubility (room temperature): 918 mg/l water; 400 g/kg 1,2-dichloroethane; 177 g/kg methanol; 91 g/kg xylene. It is acidic in reaction and incompatible with alkaline materials. /Monuron Trichloroacetate/ ... Used at 10-15 kg/ha for total weed control of uncropped areas. /Monuron Trichloroacetate/ Henry's Law constant= 5.72X10-10 atm-cu m/mole (est). Evaluation: No data were available from studies in humans. There is limited evidence in experimental animals for the carcinogenicity of monuron. Overall evaluation: Monuron is not classifiable as to its carcinogenicity to humans (Group 3). 1. SKIN CONTAMINATION SHOULD BE REMOVED PROMPTLY BY WASHING WITH SOAP AND WATER. CONTAMINATION OF THE EYES SHOULD BE TREATED IMMEDIATELY BY PROLONGED FLUSHING OF THE EYES WITH COPIOUS AMOUNTS OF CLEAN WATER. IF DERMAL OR OCULAR IRRITATION PERSISTS, MEDICAL ATTENTION SHOULD BE OBTAINED WITHOUT DELAY. /OTHER HERBICIDES/ [R2] 2. INGESTIONS OF THESE HERBICIDES ARE LIKELY TO BE FOLLOWED BY VOMITING AND DIARRHEA DUE TO THE IRRITANT PROPERTIES OF MOST OF THE TOXICANTS. ... A. IF LARGE AMOUNTS OF HERBICIDE HAVE BEEN INGESTED, AND IF THE PATIENT IS FULLY ALERT, INDUCE EMESIS WITH SYRUP OF IPECAC, FOLLOWED BY SEVERAL GLASSES OF WATER. DOSAGE FOR ADULTS AND CHILDREN OVER 12 YEARS: 30 ML; DOSAGE FOR CHILDREN UNDER 12 YEARS 15 ML. WHEN VOMITING HAS STOPPED, GIVE ACTIVATED CHARCOAL. ADD SORBITOL TO THE CHARCOAL SLURRY UNLESS DIARRHEA HAS ALREADY COMMENCED. IF, FOR SOME REASON, THE PATIENT IS NOT FULLY ALERT, PUT IN PLACE A CUFFED ENDOTRACHEAL TUBE TO PROTECT THE AIRWAY, THEN ASPIRATE AND LAVAGE THE STOMACH WITH A SLURRY OF ACTIVATED CHARCOAL. LEAVE A QUANTITY OF CHARCOAL, WITH SORBITOL, IN THE STOMACH BEFORE WITHDRAWING THE STOMACH TUBE. REPEATED ADMINISTRATION OF CHARCOAL AT HALF OR MORE THE INITIAL DOSAGE EVERY 2-4 HOURS MAY BE BENEFICIAL. /OTHER HERBICIDES/ [R3] 2. B. IF THE AMOUNT OF INGESTED HERBICIDES WAS SMALL, IF EFFECTIVE EMESIS HAS ALREADY OCCURRED, OR IF TREATMENT IS DELAYED, ADMINISTER THE ACTIVATED CHARCOAL AND SORBITOL BY MOUTH. C. IF SERIOUS DEHYDRATION AND ELECTROLYTE DEPLETION HAVE OCCURRED AS A RESULT OF VOMITING AND DIARRHEA, MONITOR BLOOD ELECTROLYTES AND AND FLUID BALANCE AND ADMINISTER INTRAVENOUS INFUSIONS OF GLUCOSE, NORMAL SALINE RINGER'S SOLUTION, OR RINGER'S LACTATE TO RESTORE EXTRACELLULAR FLUID VOLUME AND ELECTROLYTES. FOLLOW THIS WITH ORAL NUTRIENTS AS SOON AS FLUIDS CAN BE RETAINED. FLUIDS SERVE TO SUPPORT EXCRETION OF THE TOXICANTS. D. SUPPORTIVE MEASURES ARE ORDINARILY SUFFICIENT FOR SUCCESSFUL MANAGEMENT OF EXCESSIVE EXPOSURES TO THESE HERBICIDES. /OTHER HERBICIDES/ [R3] OF LOW MAMMALIAN TOXICITY ... RATS FED WITH 500 MG/KG/DAY SURVIVED 10 TREATMENTS BUT SHOWED LOSS OF WT. RATS MAINTAINED FOR 6 WK ON DIET CONTAINING 0.5, 0.05 & 0.005% ... SHOWED DEPRESSED GROWTH EFFECTS @ 0.05% LEVEL. 33% PASTE NON-IRRITANT TO GUINEA PIGS WITH NO SIGNS OF SENSITIZATION. FOUR GROUPS OF 30 MALE & 30 FEMALE 4 WK OLD ALBINO RATS (ROCHESTER, EX-WISTAR) WERE FED DIETS CONTAINING 0 (CONTROL), 0.0025, 0.025 OR 0.25% MONURON FOR UP TO 2 YR. ... 24 TUMORS (MAINLY LYMPHOMAS & MAMMARY FIBROADENOMAS) OCCURRED IN GROUP KILLED @ 2 YR, & ABOUT 30 RATS DIED WITH TUMORS BEFORE 2 YR. TOTAL TUMOR INCIDENCE WAS REPORTED TO BE WITHIN RANGE OF THAT IN CONTROL RATS OF THAT COLONY. ... 50 RANDOM-BRED MALE RATS ... GIVEN 450 MG/KG MONURON IN FOOD DAILY FOR 18 MO ... TUMORS OCCURRED IN 14 RATS & INCL 2 STOMACH TUMORS, 1 MALIGNANT TUMOR OF INTESTINE, 1 HEPATOMA, 2 LIVER CELL CARCINOMAS, 2 ALVEOLAR CARCINOMAS, 4 SMALL CELL CARCINOMAS OF LUNG & 2 SEMINOMAS. ... NO TUMORS ... IN 50 CONTROLS . ... 25 C57BL MICE ... WERE GIVEN 6 MG/ANIMAL MONURON IN MILK BY STOMACH TUBE WEEKLY FOR 13 MO, AT WHICH TIME THE 25 SURVIVORS WERE KILLED. ... 7 HAD TUMORS, COMPRISING 1 LYMPHOMA OF THE INTESTINE, 2 HEPATOMAS, 2 LIVER CELL CARCINOMAS, 1 LUNG TUMOR, & 1 MALIGNANT KIDNEY TUMOR. ... ONE HEPATOMA OCCURRED AMONG C57BL CONTROLS ... . ... 25 RANDOM BRED ... MICE WERE GIVEN 6 MG/ANIMAL MONURON IN MILK BY STOMACH TUBE WEEKLY FOR 13 MO, AT WHICH TIME THE 23 SURVIVORS WERE KILLED. ... A TOTAL OF 13 TUMORS OCCURRED ... COMPRISING 1 STOMACH ADENOCARCINOMA, 4 HEPATOMAS, 4 HEPATOCELLULAR CARCINOMAS, 2 LUNG TUMORS & 2 MALIGNANT KIDNEY TUMORS. ... NO TUMORS OCCURRED IN ... RANDOM-BRED CONTROLS ... . ... 18 MALE & 18 FEMALE (C57BL/6XAKR)F1 MICE RECEIVED COMMERCIAL MONURON (95% PURE) ... 215 MG/KG BODY WT ... AT SEVEN DAYS OF AGE BY STOMACH TUBE AND THE SAME AMOUNT DAILY UP TO 4 WK OF AGE; SUBSEQUENTLY, THE MICE WERE GIVEN 517 MG/KG OF DIET. THE EXPERIMENT WAS TERMINATED WHEN THE MICE WERE ABOUT 78 WK OF AGE, AT WHICH TIME 16 & 17 MICE, RESPECTIVELY, WERE STILL ALIVE. ... TUMOR INCIDENCES WERE COMPARED WITH THOSE IN 90 /CONTROL/ NECROPSIED MICE OF EACH SEX. ... TUMORS OCCURRED IN 6/16 NECROPSIED MALES (6 LUNG ADENOMAS) AND 3/17 NECROPSIED FEMALES (1 RETICULUM CELL SARCOMA AND 2 LUNG ADENOMAS). TUMOR INCIDENCES WERE SIGNIFICANTLY DIFFERENT ONLY FOR LUNG ADENOMAS IN MALES ... (6/16 COMPARED WITH 9/90) ... . REPEATED DOSES IN RATS PRODUCE ANEMIA. METHEMOGLOBINEMIA MAY OCCUR IF METABOLIC HYDROLYSIS PRODUCED P-CHLOROANILINE. MONURON & ITS CONGENERS INDUCED BACK MUTATIONS IN SALMONELLA TYPHIMURIUM (AMES TEST), MICRONUCLEI IN MOUSE BONE MARROW CELLS, & INHIBITION OF TESTICULAR DNA SYNTHESIS (DSI TEST) IN MICE. [R4] IN SHRIMP (PALAEMON ELEGANS) MONURON WAS NOT TOXIC AT 0.1 MG/L. TOXIC CONCENTRATIONS TO THE MOLLUSK CERASTODERMA LAMARCKI WERE TABULATED; MAXIMUM PERMISSIBLE CONCENTRATION OF MONURON WAS 0.00001 MG/L. [R5] Monuron was not mutagenic in Salmonella strains TA98, TA100, TA1535, or TA1537 in the presence or absence of Aroclor 1254-induced rat liver S9. Monuron did induce chromosomal aberrations and sister chromatid exchanges in cultured Chinese hamster ovary cells. [R6, 88-2522] Anemia and methemoglobinemia have been produced in experimental animals. Phytotoxic. Contact with desired plants should be avoided. Non irritating and non sensitizing to skin (guinea pigs) . Female Sprague Dawley rats were given monuron (250-1000 mg/kg diet) for 14 mo. The final body wt was similar to those of controls. No treatment related effects on organ weights were observed at autopsy, except for a dose related increase in spleen wt. The proportion of hemoglobin in the form of methemoglobin increased in the dose group and resulted in a secondary anemia with changes in the morphology of erythrocytes. Hemoglobin adducts of aromatic amines released from the herbicide were present at dose related levels in rats treated with monuron. Compound related lesions were observed histologically in treated rats, with increased pigmentation (hemosiderin) in the spleen, reflecting the response to the hemolytic anemia and methemoglobinemia induced by the herbicides. Pigment deposition consisting of golden brown granules in the cytoplasm of the tubular epithelium in the kidney and in the Kupffer cells in the liver were observed. The hemotoxic effects that were observed may indicate that the formation of adducts between hemoglobin and the parent aromatic amines released metabolically has a role in the splenic toxicity of this compound. [R7] A phage induction assay for screening chlorinated pesticides was described based on the Microscreen phage induction system. The pesticides tested included monuron. The Eschericia coli strains used were WP2S(lambda), which is a lambda lysogen of WP2S(trpE, uvrB), and SR714(trpE, uvrD3) as the indicator strain. Phage induction was tested with and without S9 activation by an assay of plaque formation. Monuron did not induce prophage. Monuron was positive in carcinogenicity in rodents but tested negative in both microbial assays. [R8] LD50 Rat oral 3600 mg monuron/kg In diet: rats and dogs: no effect level: 250-500 ppm LC50 BOBWHITE QUAIL GREATER THAN 5000 PPM/5 DAYS (AGE 17 DAYS, NO MORTALITY TO 5000 PPM) LC50 JAPANESE QUAIL GREATER THAN 5000 PPM/5 DAYS (AGE 12 DAYS, NO MORTALITY AT 1250 PPM, 7% AT 2500 PPM, 21% AT 5000 PPM) LC50 RING-NECKED PHEASANT 4682 PPM/5 DAYS (AGE 15 DAYS, 95% CONFIDENCE LIMIT 3902-5746 PPM) LC50 MALLARD DUCK GREATER THAN 5000 PPM/5 DAYS (AGE 10 DAYS, NO MORTALITY AT 1250 PPM, 10% AT 2500 PPM, 10% AT 5000 PPM) LC50 Japanese quail (Coturnix japonica), 14 days old, oral (5 day ad libitum in diet) >5,000 ppm Carcinogenesis studies of monuron (greater than 99% pure), ... were conducted by feeding diets containing 0, 750, or 1,500 ppm monuron to groups of 50 F344/N rats of each sex ... for 103 wk. Survivors then were fed a control diet for 1 week, killed, and examined. Throughout most of the studies, mean body weights of dosed rats of each sex were lower than those of the controls. Survival rates of low dose female rats ... were increased relative to those of the controls. Nonneoplastic changes associated with the long-term administration of monuron to rats included renal tubular cell cytomegaly, mainly involving the proximal convoluted tubules in male and female rats, and dose-related hepatic cytoplasmic changes in male rats.In the 104 wk study, the kidneys and liver of male rats were the primary tissues affected. Under the conditions of these 2 yr feed studies, there was clear euidence of carcinogenicity for male F344/N rats in that monuron caused increased incidences of tubular cell adenocarcinomas of the kidney, tubular cell adenomas of the kidney, and neoplastic nodules or carcinomas (combined) of the liver. Monuron induced cytomegaly of the renal tubular epithelial cells in both male and female F344/N rats. **** [R9] Carcinogenesis studies of monuron (greater than 99% pure), ... were connducted by feeding diets containing ... 0, 5000, or 10000 ppm to groups of 50 B6C3F1 mice of each sex for 103 weeks. Survivors then were fed a control diet for 1 week, killed, and examined. Throughout most of the studies, mean body weights of dosed ... mice of each sex were lower than those of the controls. Survival rates of ... high dose male and female mice were increased relative to those of the controls. In male mice, dose-related decreases occurred in the incidences of hepatocellular carcinomas (6/50 5/49; 2/50) and hepatocellular adenomas or carcinomas (12/50; 8/49; 6/50); incidences of hepatocellular tumors in low dose female mice were reduced, but the decreases were not dose related. The incidences of malignant lymphomas were reduced in dosed female mice (16/50; 8/50; 7/50). Under the conditions of these 2 year feed studies ... there was no evidence of carcinogenicity for female F344/N rats or for male or female B6C3FI mice. Monuron was not mutagenic in Salmonella strains TA98, TA100, TA1535, or TA1537 in the presence or absence of Aroclor 1254 induced rat liver S9. Monuron did induce chromosomal aberrations and sister chromatid exchanges in cultured Chinese hamster ovary cells. [R6, 88-252] Evaluation: No data were available from studies in humans. There is limited evidence in experimental animals for the carcinogenicity of monuron. Overall evaluation: Monuron is not classifiable as to its carcinogenicity to humans (Group 3). SUBSTITUTED UREAS ARE READILY ABSORBED BY PLANT ROOTS & TRANSLOCATED TO ACCUMULATE IN LEAVES ... THEY DO NOT PENETRATE READILY THROUGH LEAVES. AFTER ADMIN OF 175 MG/KG BODY WT/DAY FOR 60 DAYS OR OF 0.1-20.0 MG/KG BODY WT FOR 6 MO, TISSUE RETENTION OF MONURON-RELATED SUBSTANCES OCCURRED /MOST/ IN LUNGS, /DECR RESPECTIVELY IN/ HEART, LIVER, BRAIN & KIDNEYS, MILK, BONE MARROW & THYROID GLAND. IN RATS GIVEN 875 MG/KG BODY WT ORALLY, PEAK BLOOD CONCN OCCURRED 2 HR AFTER DOSING ... CMPD WAS DISTRIBUTED EVENLY THROUGHOUT BODY. 3-(P-CHLOROPHENYL)-1,1-DIMETHYLUREA YIELDS IN COTTON 3-(P-CHLOROPHENYL)-1-HYDROXYMETHYL-1-METHYLUREA; ALSO YIELDS 3-(P-CHLOROPHENYL)-1-METHYLUREA. /FROM TABLE/ COTTON PLANTS DEGRADED MONURON TO MONOMETHYLMONURON & P-CHLORO-PHENYLUREA BY SUCCESSIVE DEMETHYLATIONS & THEN TO P-CHLOROANILINE BY HYDROLYSIS OF AMIDE BOND. IN MAMMALS, MONURON IS METABOLIZED (I) BY OXIDATIVE N-DEMETHYLATION, (II) BY HYDROXYLATION OF AROMATIC NUCLEUS & (III) BY FISSION OF UREA RESIDUE TO GIVE CHLOROANILINE DERIVATIVES. YIELDS OF VARIOUS METABOLITES INDICATE THAT HYDROXYLATION FAVORS 2-POSITION RATHER THAN 3-POSITION. PHENOLIC METABOLITES WERE EXCRETED IN URINE AS CONJUGATES. 4-CHLORO-2-HYDROXYANILINE WAS EXCRETED AS THE N-ACETYL CMPD 2-ACETAMINO-5-CHLOROPHENOL. ... URINARY METABOLITES ... IN RATS ARE N-(4-CHLOROPHENYL)-N'-METHYLUREA, N-(4-CHLOROPHENYL)UREA (14% OF DOSE), N-(2- HYDROXY-4-CHLOROPHENYL)-N',N'-DIMETHYLUREA, N-(2-HYDROXY-4-CHLO ROPHENYL)-N'-METHYLUREA (1.5%), N-(2-HYDROXY-4-CHLOROPHENYL)UREA (6.5%), 2-ACETAMINO-5-CHLOROPHENOL & N-(3-HYDROXY-4-CHLOROPHENYL)UREA (2.2%). N-Hydroxymethylation of monuron causes the formation of beta-D-glucoside, and other polar, unknown methanol-soluble metabolites and insoluble residues in higher plants. The terminal demethylation product is p-chlorophenylurea. /Undergoes/ ... metabolism via the liver microsomes. Sweet orange seedlings took up monuron and metabolized it to 3-(4- chlorophenyl)-l-methylurea and 4-chlorophenylurea. Water soluble metabolites developed over the period of one day to 10 weeks of exposure. TLC, IR, MS and enzymatic hydrolysis indicated that monuron was conjugated with fructose. Incubation of monuron with Rhizopus japonicus produced 1-(4-chlorophenyl)3-methylurea. Young leaves were cut from 2 week old plants of bean (Phaseolus vulgaris var Black Valentine) and corn (Zea mays L. var. Batam Cross) and exposed to carbonyl-(l4)C-labeled monuron in water. After monuron uptake by the leaves, analyses showed the presence in both plants of: 1-(4-chlorophenyl)-3-methylurea; 4-chlorophenylurea; an unidentified conjugate: and l,l-dimethyl-3-(2-hydroxy-4-chlorophenyl) urea. Although the conjugates were not identified, these studies indicated the presence of a monuron-polypeptide larger than 5000 and three glucose conjugates. The latter were identified as mono-beta-D-glucose conjugates of 2-hydroxy-4-chlorophenylurea; l-(2-hydroxy-4-chlorophenyl)-3-methylurea; and l,l-dimethyl-3-(2-hydroxy-4-chlorophenyl) urea. SUBSTITUTED UREAS ... IN LEAVES ... CAUSE COLLAPSE OF PARENCHYMA VESSELS. ... THEY INHIBIT PHOTOSYNTHESIS ... AND ARE POWERFUL INHIBITORS OF OXIDATION OF WATER TO OXYGEN (HILL REACTION) ... SUGGESTED THAT MONURON BLOCKS PHOTOSYNTHESIS AT SITE OF ELECTRON TRANSFER BY FLAVIN MONONUCLEOTIDE . INTC: IN PRESENCE OF MODERATE AMT OF CARBARYL, DEGRADATION /OF MONURON IN COTTON PLANTS/ BEYOND MONO-DEMETHYLATION WAS INHIBITED. ... 4-BENZOTHIOPHENE-N-METHYLCARBAMATE WAS AS EFFECTIVE AS CARBARYL. FLAVINS (FLAVINMONONUCLEOTIDE) HAVE BEEN SHOWN TO CAUSE PHOTOINACTIVATION OF PHENYLUREAS, SUCH AS MONURON, IN VITRO. Monuron is a herbicide recommended for use in non-crop areas for total control of weeds, and it would be released to the environment as a result of this use. Monuron's registration with EPA for use as a herbicide was cancelled in 1977, and therefore if its is still manufactured, it would be manufactured for export. In soil, monuron is transformed to its metabolites primarily by biodegradation. The half-life of monuron in field soils ranges from less than 30 days to 166 days. Monuron has a moderate mobility in most soils. Although biodegradation is slow, it is probably the major degradative pathway in water. Loss of monuron due to hydrolysis and volatilization will not be important processes. However, some loss may result due to photolysis in surface layers of water. Monuron is not expected to bioconcentrate in aquatic organisms. The reaction with hydroxyl radicals with an estimated half-life of 5.5 hr may be the most important loss process for vapor phase monuron in the atmosphere. Removal of atmospheric monuron may also occur by dry and wet deposition. Monuron is not registered for use in the US and therefore exposure of applicators, other workers to monuron will be limited. (SRC) Monuron is not known to occur naturally(1). [R10] Since monuron is commercially produced and used as a herbicide(1), it will be released to the environment during the manufacture and particularly during the use of the herbicide(SRC). Accidental spills during loading/unloading and shipment will also release monuron in the environment(SRC). [R11] TERRESTRIAL FATE: Biodegradation appears to be the major process by which monuron may be lost from most soils(1-2). The loss of monuron from soil surface by photolysis may account for a small fraction of loss of monuron as most of the monuron would move deeper into soil with rain(1). Volatilization loss of monuron from dry soil or wet soils should not be important(1). Monuron may moderately leach in most soils(3-4). Depending on the nature of soil and climatic conditions, the field half-life of monuron in soil range from less than 30 days to 166 days(5-7). [R12] AQUATIC FATE: At low concns (on the order of ug/l), the major process for the loss of monuron from water appears to be biodegradation(1-2). Neither hydrolysis nor any other chemical reaction is important for the loss of monuron in water(1,3). Monuron may photolyze in surface layers of water where sunlight penterates(1). The photolysis half-life of monuron in aqueous solution by natural sunlight is estimated to be 15 days(4). Photolysis is accelerated by the presence of surfactants(5). Based upon the low vapor pressure(6) and high water solubility(7), monuron should not volatilize from water. Monuron is not expected to bioconcentrate in aquatic organisms(7). [R13] ATMOSPHERIC FATE: Based upon on its vapor pressure, 5.03X10-7 mm Hg at 25 deg C(1), monuron is expected to be present partially in the vapor phase and partially in the particulate form in air(2,SRC). Vapor phase monuron will react with photochemically produced hydroxyl radicals with a half-life of 6.7 hr(3-4). Monuron may also be removed from the atmosphere by dry and wet deposition(SRC). [R14] /INVESTIGATORS/ ... WERE ABLE TO ISOLATE FROM BROOKSTON SILTY CLAY LOAM A BACTERIUM OF GENUS PSEUDOMONAS WHICH UTILIZED MONURON AS SOLE SOURCE OF CARBON. Several pure cultures of bacteria including Pseudomonas, Xanthomonas, Sarcina, and Bacillus and fungi including Penicillium and Aspergillus are capable of degrading monuron(1-3). The major process for the loss of monuron from water is biodegradation(3). At a concentration of 6-7 mg/l, no loss of monuron by mixed microorganisms from river water and sewage was observed in 16 wk(5). However, in a soil-water system, appreciable biodegradation occurred after 16 weeks and 15% of monuron was recovered after 128 wk(4). At an initial concn of 10 ug/l in sewage water, monuron started to mineralize on day 45 and about 20% of monuron mineralized by day 84(6). No mineralization of monuron was observed in 84 days at a concn of 10 mg/l(6). Besides carbon dioxide, products with chromatographic characteristics of 4-(chlorophenyl)urea and 4-chloroaniline were also identified(6). [R15] Monuron is lost from soil primarily through biodegradation(1,3). Monuron loss from two soils was about 40% in 22 wk at a concn of 4 ppm(1). In a clay loam soil, approx. 10% of monuron mineralized to carbon dioxide in 90 days(1). Hydroxylation products of monuron have been identified in soil(5). Except for most heavily treated soils (above 16 lbs/acre), approx. 90% of monuron disappeared in 1 yr. During the second year, loss averaged about 62%(3). Monuron's degradation is a function of application rate(2). Biodegradation is favored by high temperature adequate moisture and high soil organic matter content(2). When monuron was incubated with sediments from a pond under anaerobic conditions, no ring-substituted products were detected in 73 days(4). Therefore, monuron may persist in soil and sediments under anaerobic conditions(SRC). [R16] Monuron was stable in sterile aqueous solution at pH values normally found in natural waters(1). solution of monuron in the dark was found to be stable towards chemical reactions(2). The disappearance of monuron in soil by non-biological degradation was concluded to be unimportant in most cases(2). When a 88.3 ppm aqueous solution of monuron was exposed to sunlight, 83% loss was observed in 48 days(2). The half-life for the photodegradation of aqueous solution of monuron in natural sunlight has been estimated to be 15 days(5). Addition of surfactants enhanced the photolysis rate of monuron in solution(3). Five substituted biphenyl photoproducts were identified from the photolysis of monuron(4). Besides these biphenyl photoproducts, demethylated, completely monodemethylated, and a phenolic product, 3-(2-hydroxy-4-chlorophenyl)-1,1-dimethylurea have been isolated as photoproducts of monuron(6-7). [R17] Based on an estimation method(1-2), the rate constant for reaction of monuron with hydroxyl radicals in the atmosphere is 3.8X10-11 cu cm/molecule-sec(SRC). If the 12 hr daylight average concentration of hydroxyl radicals in the atmosphre is assumed to be 1.5X10-6 radicals/cu cm(1), the half-life of this reaction would be 6.7 hr(SRC). [R18] The 4-halogen substituent was replaced by hydroxyl when linuron and monuron wereexposed to sunlight in aqueous solutions; demethylation also occured. Monuron, on irradiation in water under aerobic conditions, gives 3-(4-chloro-2-hydroxyphenyl)-1,1-dimethylurea, together with 1,3-bis(p-chlorophenyl)urea and a number of oxidized and polymeric compounds. 1,3-Bis(p-chlorophenyl)urea may be formed by a reaction which proceeds via an ioscyanate intermediate; dimethylamine is eliminated from monuron to form p-chlorophenyl isocyanate, which can react with free p-chloroaniline. When incubated with the fungus Cunninghamella echinulata Thaxter, monuron yielded 3-(4-chlorophenyl-methylurea and 4-chlorophenylurea. UV irradiation of saturated aqueous solutions of monuron produced the following identified compounds: 3-(4-chlorophenyl)-1-formyl-1-methylurea; 3-(4-chlorophenyl)-1-methylurea; 3-(4-hydroxyphenyl)-1-formyl-methylurea; 4,4'-dichlorocarbanilide; 3-(4-hydroxyphenyl)-dimethylurea; 3-(4-chloro-2-hydroxyphenyl)- dimethylurea; the dimer, 3-[4-(N-(N',N'-dimethylaminocarbonyl)-4'-chloroanilino)phenyl]- dimethylurea; the p-hydroxy dimer; a dihydroxy dimer; the monodealkylated dimer; and tentatively a trimeric product. Saturated aqueous solutions of monuron were treated with ferrous sulfdte + hydrogen peroxide (Fenton's reagent). Products were characterized spectroscopically: 3-(4-hydroxyphenyl)- dimethylurea; 4-chlorophenylurea; 3-(4-chlorophenyl)-1-methylurea; 4-chloro-2hydroxyphenylurea; 3-(4-chloro-2-hydroxyphenyl)-1-methylured; 3-(4- chloro-2-hydroxyphenyl)-dimethylurea; 4-chloro-2-henzoxazolinone; 4-chloro-2,4'-dihydroxycarbanilide; and 4-chloro-4'-hydroxycarbdnilide. From its water solubility and a regression equation, the bioconcentration factor (BCF) for monuron in aquatic organisms has been estimated to be 29(1). Based on a log Kow value of 1.94(2) and a regression equation(3), the BCF value can be estimated to be 17(SRC). Both these values indicate that bioconcentration of monuron in aquatic organisms should not be important(1,SRC). The low rate of uptake and fast depuration (depuration half-life of 0.45 days) of monuron from catfish (Ictalurus melas)(4) also indicates that bioconcentration will not be important(SRC). [R19] The Koc values for monuron determined from experimental adsorption isotherms or estimated using recommended regression equations range from 83 to 225(1-6). According to a suggested classification scheme(9), Koc values of this magnitude indicate that monuron is moderately to highly mobile in soil. Soil thin layer chromatographic studies also indicate that monuron is moderately mobile in soil(5,7). The adsorption of monuron in soil is virtually independent of pH and clay content of soil, but the adsorption increases with increase in organic carbon content(6,8). However, other investigators concluded that the adsorption of monuron increases with an increase in the clay content of soil(10). [R20] Volatilization from water should not be important transport process for monuron. Based on a value of Henry's Law constant of 5.72X10-10 atm-cu m/mole estimated from the ratio of vapor pressure(2) and water solubility(1), the volatilization half-life of monuron from a 1 m deep model river flowing at a speed of 1 m/sec and a wind speed of 5 m/sec is estimated to be about 165 yr(3,SRC). If the effect of sorption is considered, the half-life will be even longer. The volatilization half-life of monuron from 1 to 10 cm soil depth has been estimated to be about 160-170 days(4). The volatilization of monuron coevaporating with water vapor in soil was found to be insignificant(5). Therefore, the loss of monuron due to volatilization from both dry and wet soil should not be an important environmental fate process(SRC). [R21] GROUNDWATER: Monuron was detected in one groundwater sample from a rural area in Ontario, Canada that was contaminated with the herbicide as a result of a spill(1). [R22] IN RATS GIVEN 875 MG/KG BODY WT ORALLY, ... MONURON RELATED MATERIAL WAS ... SECRETED INTO MILK OF LACTATING ANIMALS. Monuron is not registered for use in the U.S. and therefore there should be no exposure of monuron by field applicators and formulators(SRC). If monuron is manufactured for export, occupational exposure of workers involved in manufacturing and loading monuron would most likely be through dermal contact. (SRC) PRODUCT ANALYSIS IS BY HYDROLYSIS AND TITRATION OF THE 4-CHLOROANILINE WITH PERCHLORIC ACID. RESIDUE ANALYSIS IS BY ALKALINE HYDROLYSIS, AND COLORIMETRIC DETERMINATION OF THE 4-CHLOROANILINE, BY GLC AND HPLC. RAPID BIOLUMINESCENCE METHOD CAPABLE OF DETERMINING LOW CONCN OF PHOTOSYNTHESIS-INHIBITING HERBICIDES, SUCH AS MONURON, IN WATER & SOIL . Sample matrix: Specified fruit and vegetables. Sample preparation: Alkaline hydrolysis to release para-chloroaniline; diazotize; couple with N-(1-naphthyl) ethylene-diamine; clean-up and separate resulting dyes on cellulose column. Assay procedure: TLC. Sample matrix: Residues. Sample preparation: Hydrolyse to para-chloroaniline using sodium hydroxide; distil; acidify distillate; wash with hexane or dichloromethane; neutralize; extract with hexane. Assay procedure: GC with FID COLORIMETRIC REACTION, SPECTROPHOTOMETRY @ 560 NM, FOR DETERMINATION OF MONURON. GC HAS BEEN USED TO DETERMINE MONURON & ITS HYDROLOSIS PRODUCTS. ... TLC SCREENING TEST FOR PHENYLUREA HERBICIDES /INCLUDING MONURON/ THAT INHIBIT CERTAIN ENZYMIC ACTIVITIES /HAVE BEEN DESCRIBED/. Product analysis of monuron is by hydrolysis and titration of the liberated amine and of monuron-TCA by infrared spectrometry. Residues of monuron may be determined by GLC.

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