Chloroxuron

Signs and Symptoms of Chloroxuron Exposure: Acute exposure to chloroxuron may produce the following signs and symptoms: dilated pupils, visual disturbances, methemoglobinemia, cyanosis, chest pain, irregular heartbeat, abdominal pain, nausea, vomiting, diarrhea, anorexia, dehydration, urinary retention, and urinary tract irritation. Muscular weakness, aching, tremors, mental confusion, and central nervous system depression may also be noted. Contact with chloroxuron dust may produce irritation of the eye and mucous membranes of the respiratory system.

Incinerate in a unit with effluent gas scrubbing. Recommendable method: Incineration.

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

Only clean clothing and underwear should be worn and clothing should be changed daily for freshly washed clothes. Contaminated equipment should not be taken home. Adequate sanitary facilities and washing water should be provided for workers to wash before meals. Smoking and the consumption of alcoholic drinks before or during the handling of herbicides should be forbidden. Contaminated clothing should be removed immediately and a hot bath taken if possible. /Herbicides/

Fully enclosed processes, remote control and exhaust ventilation should be used. /Herbicides/

Herbicides should not be removed from their original containers. Injurious concentrates should be used in small containers that are easy to handle and to destroy. /Herbicides/

Tolerances for combined negligible residues of the herbicide chloroxuron (3-[p-(p-chlorophenoxy) phenyl]-1,1-dimethylurea) and its metabolites containing the p-(p-chlorophenoxy) aniline moiety calculated as chloroxuron in or on raw agricultural commodities are established as follows: 0.15 ppm in or on soybeans and soybean forage; and 0.1 ppm in or on carrots, celery, onions (dry bulb), and strawberries.

0.91 [mg/m3]

10 [mg/m3]

68 [mg/m3]

For emergency situations, wear a positive pressure, pressure-demand, full facepiece self-contained breathing apparatus (SCBA) or pressure- demand supplied air respirator with escape SCBA and a fully-encapsulating, chemical resistant suit. (EPA, 1998)

The use of personal protective equipment such as glasses, synthetic gloves and face masks is important. /Herbicides/

LC50 Rainbow trout 0.43 mg/l/96 hr @ 12 °C (95% confidence limit 0.36-0.51 mg/l), wt 0.7 g. Static bioassay without aeration, pH 7.2-7.5, water hardness 40-50 mg/l as calcium carbonate and alkalinity of 30-35 mg/l.

LC50 Channel catfish 0.43 mg/l/96 hr @ 18 °C (95% confidence limit 0.16-1.24 mg/l), wt 1.3 g. Static bioassay without aeration, pH 7.2-7.5, water hardness 40-50 mg/l as calcium carbonate and alkalinity of 30-35 mg/l.

LD50 MALLARD DUCK ORAL GREATER THAN 2000 MG/KG, 3-4 MO OLD FEMALES /50% WETTABLE POWDER/

LC50 KILLIFISH (ORYZIAS LATIPES) >15 PPM /CONDITIONS OF BIOASSAY NOT SPECIFIED/

For more Ecotoxicity Values (Complete) data for CHLOROXURON (7 total), please visit the HSDB record page.

Terrestrial fate: Duration of residual activity in soil is about 4 months.

TERRESTRIAL FATE: The recommended Koc value for chloroxuron in soil is 2820, with values ranging from 1323 to 6220(1). A recommended regression-derived equation(2), indicates that chloroxuron is expected to have slight mobility in soil(SRC). Volatilization of chloroxuron from moist soil surfaces is not expected(SRC) given an estimated Henry's Law constant of 4.03X10-10 atm-cu m/mole(SRC), using an experimental vapor pressure and water solubility(3,4). Chloroxuron is not expected to volatilize from dry soil surfaces based on an experimental vapor pressure of 3.9X10-9 mm Hg(3,SRC). The field dissipation half-life of chloroxuron has a recommended value of 45 days; however, values range from 30 to 60 days(1). The half-life of chloroxuron in silt loam soil under aerobic conditions is recommended as 110 days(1). Bacterial suspensions derived from humus soil were demonstrated to metabolize chloroxuron to N-(4-chlorophenoxy)-phenyl-N-methylurea, N-(4-chlorophenoxy)-phenylurea, and (4-chlorophenoxy)-aniline(5).

AQUATIC FATE: Based on a recommended classification scheme(1), a recommended Koc value of 2820(2,SRC) indicates that chloroxuron is expected to adsorb to suspended solids and sediment(s) in water(SRC). Chloroxuron is not expected to volatilize from water surfaces(3,SRC) based on an estimated Henry's Law constant of 4.03X10-10 atm-cu m/mole(SRC), calculated from experimental vapor pressure and water solubility(4,5). Biodegradation of chloroxuron in soil would suggest that biodegradation of chloroxuron in water systems may be important(SRC). According to a classification scheme(6), an estimated BCF value of 295(3,SRC) from an experimental water solubility(5), suggests that bioconcentration in aquatic organisms is high(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), chloroxuron, which has an experimental vapor pressure of 3.9X10-9 mm Hg at 25 °C(2,SRC), is expected to exist solely as a particulate in the ambient atmosphere. Particulate-phase chloroxuron may be physically removed from the air by wet and dry deposition(SRC).

CHLOROXURON IS QUITE STRONGLY ADSORBED ON SOIL PARTICLES & THIS SEEMS TO BE AN IMPORTANT FACTOR IN CONTROLLING ITS AVAILABILITY IN SOIL SOLN & DETERMINING BOTH THE INITIAL TOXICITY & THE RESIDUAL ACTIVITY IN SOME TYPES OF SOILS. THE FOLLOWING CONCN OF CHLOROXURON ADSORBED WERE IN EQUIL WITH 1 PPM SOIL SOLN: 14 UG/G (SANDY LOAM), 40 UG/G (CLAY LOAM), & 110 UG/G (HUMUS SOIL). WITH SOIL COLUMNS (SANDY, CLAY, & HUMUS SOILS) & SIMULATED RAIN (200 MM IN 45 HR), THE BULK OF CHLOROXURON WAS NOT REMOVED FROM THE TOP 1 CM LAYER OF ALL THREE SOILS. LEACHING DOES NOT APPEAR TO BE A FACTOR IN REMOVING CHLOROXURON FROM THE SURFACE OF SOIL.

The recommended Koc value for chloroxuron in soil is 2820, with values ranging from 1323 to 6220(1). According to a recommended classification scheme(2), this estimated Koc value suggests that chloroxuron is expected to have slight mobility in soil(SRC). The mobility of chloroxuron in Hagerstown silt clay loam was determined using soil thin layer chromatography. Results showed an Rf value of 0.09, corresponding to a classification of 1, immobile(3). Adsorption of chloroxuron on montmorillonite ranged from 50 to 400 umol/g(4).

Tenoran (CAS# 1982-47-4) was evaluated for evidence of developmental toxicity. Pregnant Charles River rats (26 rats/group) were dosed with 0, 5, 25, or 125 mg/kg body weight by oral gavage on days 6-15 of gestation. No compound-related mortalities occurred during the study. At 125 mg/kg, 26/26 rats appeared pale. In the 125 and 25 mg/kg groups, treatment related enlarged spleens and a misshappened spleen were observed in 22/26 and 1/26 dams respectively. Additionally, 1/26 rats in the 25 mg/kg dose group had an enlarged and necrotic spleen. One rat with ptosis was observed at the 125 mg/kg dose. One of 26 and 2/26 rats of the 25 and 125 mg/kg dose group had hollow kidney(s). Signs of toxicity at the 125 mg/kg dose included statistically significant (p<0.05) decreased food consumption, body weight, and body weight gain. No compound-related effects on reproductive parameters examined were observed, including the number of corpora lutea, implantation sites, live fetuses, resorptions, dead fetuses, post- implantation, and post-implantation loss. At 125 mg/kg, fetal weights were significantly (p<0.05) decreased. Visceral variations were observed with a similar incidence across all dose groups and were limited to variations in the kidneys and ureters. The incidence of skeletal variations significantly (p<0.05) increased in the 125 mg/kg group and included bipartite and not- ossified vertebral centrum; wavy ribs; not completely ossified os pubis, premaxillae, parietal bones, occipitals and teeth; and not-ossified metacarpals and sternebrae. The maternal and fetal no-observable-effect-levels (NOELS) were 5 and 25 mg/kg, respectively. The maximum tolerated dose (MTD) was 125 mg/kg.

Tenoran (CAS# 1982-47-4) was evaluated for reproductive toxicity in a 2-generation test. The test material was fed at dietary levels of 0, 10, 100, or 1000 ppm to Charles River rats (30/sex/group). The treatment period was continuous (7 days/week) prior to cohabitation, throughout cohabitation, gestation and lactation. There were no treatment related effects in the 10 ppm group. Minimal effects were observed in the F1 parental generation at 100 ppm including slight reductions in mean body weight gains, and the single occurrence of lesions of the spleen. In the 1000 ppm group, treatment related changes in the F0 and F1 parental generations included: clinical signs of pale eyes and/or pinnae and extremities; statistically significant (p<0.05) reduced mean body weight, body weight gain and mean food consumption; alterations in mean absolute and/or relative ovarian and/or testicular weights; enlarged spleens, characterized by congestion, hemosiderosis, and extramedullary hematopoiesis in the majority of the parental F0 females, all parental F1 females, and one parental F1 male. No remarkable gross or macroscopic findings were observed in any of the reproductive organs or the pituitary glands examined were noted in the F0, F1, and F2 generations. No treatment-related effects were noted on precoital interval, gestation duration, mating, fertility and gestation indices, mean numbers of implantation sites and viable neonates, mean calculated or percentages of post-implantation loss, mean numbers and percentages of stillbirths, F1 or F2 pup survival, pup sex ratios or pup malformations. At 1000 ppm, statistically (p<0.05) reduced mean F1 and F2 male and female pup weights throughout the postpartum period, nor were enlarged and/or darkened spleens seen in F1 weanling. The maximum tolerated dose (MTD) was achieved or exceeded at 1000 ppm, given the large reductions in body weight. The no-observable effect level (NOEL) was 10 ppm.

CHLOROXURON WAS N-DEMETHYLATED BY MICROORGANISMS FROM BOTH LOUISIANA & INDIANA SOILS. METABOLISM WAS PREDOMINANTLY BY DIRECT HYDROLYSIS TO THE ANILINE, WHICH IN TURN UNDERWENT FURTHER TRANSFORMATIONS.

BACTERIAL SUSPENSIONS DERIVED FROM HUMUS SOIL METABOLIZE CHLOROXURON TO THE MONOMETHYLATED, DIMETHYLATED, & THE (4-CHLOROPHENOXY)ANILINE DERIVATIVES.

SUBSTITUTED UREAS ARE ALL QUITE STABLE CHEMICALLY & ARE DEGRADED ONLY SLOWLY BY SOIL MICROFLORA, RESULTING IN COMPARATIVELY LONG SOIL HALF-LIFE. /SUBSTITUTED UREAS/

Dealkylation is an important pathway of metabolism, and chloroxuron is converted sequentially to the mono- and bis-N-demethylated products in cultured soil bacteria of several crop and weed species.

For more Environmental Biodegradation (Complete) data for CHLOROXURON (9 total), please visit the HSDB record page.

An estimated BCF value of 295 was calculated for chloroxuron(SRC), using an experimental water solubility of 3.7 mg/l(1,SRC) and a recommended regression-derived equation(2). According to a classification scheme(3), this BCF value suggests that bioconcentration in aquatic organisms is high, but not very high(SRC).

The Henry's Law constant for chloroxuron is estimated as 4.03X10-10 atm-cu m/mole(SRC) from its experimental values for vapor pressure, 3.9X10-9 mm Hg(1), and water solubility, 3.7 mg/l(2). This value indicates that chloroxuron will be essentially nonvolatile from water surfaces(3,SRC). Chloroxuron's Henry's Law constant(1,2,SRC) indicates that volatilization from moist soil surfaces is not expected(SRC). Chloroxuron is not expected to volatilize from dry soil surfaces based on a measured vapor pressure of 3.9X10-9 mm Hg(1).

Tolerances for combined negligible residues of the herbicide chloroxuron (3-[p-(p-chlorophenoxy) phenyl]-1,1-dimethylurea) and its metabolites containing the p-(p-chlorophenoxy) aniline moiety calculated as chloroxuron in or on raw agricultural commodities are established as follows: soybeans and soybean forage; and carrots, celery, onions (dry bulb), and strawberries.