Thidiazuron

220.25

220.25

257-356-7

0091WH7STF

DTXSID0032651

Colorless crystals

95.2

1.77 at pH 7.3

white odourless crystalline solid

1.5±0.1 g/cm3

211 °C (decomp)

410.5±55.0 °C at 760 mmHg

202.1±31.5 °C

1.722

soluble in DMSO

0-6°C

2.30X10-11 mmHg at 25 deg C

Oral-Rat LD50: 5350 mg/kg; Oral-Mouse LD50: 3740 mg/kg

Combustion produces toxic nitrogen oxide and sulfur oxide gas

Odorless

Henry's Law constant = 3.3X10-13 atm-cu m/mole at 25 °C (est)

pKa = 8.86

Hydrolytically stable at room temperature from pH 5-9

UN 3077 9 / PGIII

3

36/37/38-51/53

22-26-36-61

YU1395000

Xi,N

The warehouse is ventilated, low temperature and dry; stored and transported separately from food materials

Stable at normal temperatures and pressures.

P273-P305 + P351 + P338-P391-P501

H315-H319-H335-H410

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.|Do not discharge effluent containing this product into lakes, streams, ponds, estuaries, oceans, or other waters unless in accordance with the requirements of a National Pollution Discharge Elimination System (NPDES) permit and the permitting authority has been notified in writing prior to discharge.

USEPA/Office of Prevention, Pesticides and Toxic Substances; Reregistration Eligibility Decision Document - Thidiazuron EPA 738-R-04-012 (September 2005). The RED summarizes the risk assessment conclusions and outlines any risk reduction measures necessary for the pesticide to continue to be registered in the U.S.[Available from, as of May 27, 2009: http://www.epa.gov/pesticides/reregistration/status.htm]|USEPA, Office of Prevention, Pesticides, and Toxic Substances; Revised HED Human Health Risk Assessment for Thidiazuron (51707-55-2) (August 2005). EPA Docket No.: EPA-HQ-OPP-2004-0382-0017.

|Warning|H312 (97.76%): Harmful in contact with skin [Warning Acute toxicity, dermal]|P261, P264, P271, P280, P302+P352, P304+P312, P304+P340, P305+P351+P338, P312, P321, P322, P332+P313, P337+P313, P362, P363, P403+P233, P405, and P501|Aggregated GHS information provided by 134 companies from 5 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Personal Protective Equipment (PPE): All mixers, loaders and applicators must wear long sleeved shirt, long pants, and shoes and socks.

Fire extinguishing media: water, foam, dry powder, CO2.

SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a POTW is acceptable only after review by the governing authority. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal. If it is not practicable to manage the chemical in this fashion, it must meet Hazardous Material Criteria for disposal.

SRP: Contaminated protective clothing should be segregated in such a manner so that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. Quality assurance to ascertain the completeness of the cleaning procedures should be implemented before the decontaminated protective clothing is returned for reuse by the workers. Contaminated clothing should not be taken home at end of shift, but should remain at employee's place of work for cleaning.|Follow manufacturer's instructions for cleaning/maintaining PPE. If no such instructions for washables exist, use detergent and hot water. Keep and wash PPE separately from other laundry.|Users should wash hands before eating, drinking, chewing gum, using tobacco, or using the toilet.|Users should remove clothing/ PPE immediately if pesticide gets inside. Then wash thoroughly and put on clean clothing.|For more Preventive Measures (Complete) data for Thidiazuron (8 total), please visit the HSDB record page.

Thidiazuron is not a dermal sensitizer or a skin irritant ...

Occupational exposure to thidiazuron may occur through inhalation of dust and dermal contact with this compound at workplaces where thidiazuron is produced or used. The general population may be exposed to thidiazuron by dermal contact with this compound near application areas such as cotton fields. (SRC)

moderately

LD50 Rat dermal >4000 mg/kg.|LD50 Rat oral > 2000 mg/kg|LD50 Rat dermal > 5000 mg/kg|LD50 Rat oral 5350 mg/kg|For more Non-Human Toxicity Values (Complete) data for Thidiazuron (8 total), please visit the HSDB record page.

/AQUATIC SPECIES/ Bluegills (Lepomis macrochirus) exposed to 0.1 ppm of thidiazuron-14C cotton defoliant for 28 days under continuous flow conditions accumulated relatively low levels of radiocarbon. The maximum detected was 5.4 ppm in fillet tissue after 1 day. During a 14 day depuration period, radioactivity declined to 1.0 ppm or less. Fractionation of offal and fillet tissues from bluegills collected at 28 days indicated that most of the radioactive material was water soluble, although appreciable amounts of organosoluble radioactive material also were present. When bluegills were injected intraperitoneally with thidiazuron-14C, metabolism and elimination were relatively rapid. Organosoluble radioactive material isolated from fish tissue included thidiazuron, its 2-hydroxyphenyl derivative, phenylurea, and several unknowns. Channel catfish (Ictalurus punctatus) exposed under static conditions to a system containing 0.15 ppm of thidiazuron-14C incorporated into soil also accumulated only low concentrations of radiocarbon. The maximum detected was 2.5 ppb in offal tissue at 7 days. In fillet tissue, radioactivity did not exceed 0.5 ppb. There was no evidence from these studies to indicate that thidiazuron would pose a hazard to the aquatic ecosystem.

Thidiazuron's production may result in its release to the environment through various waste streams; its use as a cotton growth regulator(1) and defoliation agent(2) will result in its direct release to the environment(SRC).

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 61(SRC), determined from a log Kow of 1.77(2) and a regression-derived equation(3), indicates that thidiazuron is expected to have high mobility in soil(SRC). The pKa of thidiazuron is 8.86(2), indicating that this compound will partially exist in anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4). Volatilization of thidiazuron from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 3.3X10-13 atm-cu m/mole(SRC), based upon its vapor pressure, 2.3X10-11 mm Hg(5) and water solubility, 20 mg/L(6). Thidiazuron is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(5). In aerobic soil metabolism half-lives averages (and ranges) in four soils were approximately 206 (173-254), 253 (187-393), 436 (310-737), and 140 (119-170) days, respectively(7). Crop rotational intervals also provide a measure of thidiazuron's persistence in soil. Product labels list rotational crop intervals as long as one year(7). Studies on thidiazuron's dissipation from terrestrial fields produced linear first-order half-lives of 237 days (California), 173 days (Florida), and 161 days (North Carolina)(7). In the soil in which metabolism was fastest, C-14 labeled thidiazuron appeared to reach an approximately flat maximum concentration of roughly 6-9 percent of applied radioactivity during the period from approximately 88 days to the study end at 168 days(7).|AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 61(SRC), determined from a log Kow of 1.77(2) and a regression-derived equation(3), indicates that thidiazuron may adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(4) based upon an estimated Henry's Law constant of 3.3X10-13 atm-cu m/mole(SRC), derived from its vapor pressure, 2.3X10-11 mm Hg(5) and water solubility, 20 mg/L(6). A pKa of 8.86(2) indicates thidiazuron will partially exist in the anion form at pH values of 5 to 9, and therefore volatilization from water surfaces is not expected to be an important fate process(7). According to a classification scheme(8), an estimated BCF of 6.8(SRC), from its log Kow(2) and a regression-derived equation(9), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Thidiazuron was found to be hydrolytically stable against anaerobic metabolism in water(9). In water, thidiazuron undergoes relatively rapid, pH dependent photolysis into two photoproducts(10). Photolysis half-lives were determined to be approximately 1-2 hours(10).|ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), thidiazuron, which has a vapor pressure of 2.3X10-11 mm Hg at 25 °C(2), is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase thidiazuron may be removed from the air by wet or dry deposition(SRC). Thidiazuron contains chromophores that typically absorb at wavelengths >290 nm(3) and was found to rapidly convert to the photoisomer 1-phenyl-3-(1,2,5-thiadiazol-3-yl)urea under these conditions(4).

Thidiazuron is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(1); it was found to be hydrolytically stable at room temperature and pH 5-9(2). Thidiazuron contains chromophores that typically absorb at wavelengths >290 nm(1) and was found to rapidly convert to the photoisomer 1-phenyl-3-(1,2,5-thiadiazol-3-yl)urea(2). An accelerated stability study found no degradation of thidiazuron after storage at 54 °C for 14 days(2).

An estimated BCF of 6.8(SRC) was calculated for thidiazuron, using a log Kow of 1.77(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

109.65 L/kg|The Koc of thidiazuron is estimated as 61(SRC), using a log Kow of 1.77(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that thidiazuron is expected to have high mobility in soil. The pKa of thidiazuron is 8.86(1), indicating that this compound will partially exist in anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4). Freundlich adsorption coefficients of three German standard soils: 4.4, 7.3, and 16; one United Kingdom soil: 19; and four United States soils: 1.5, 8.3, 2.0, 1.7, indicated thidiazuron has intermediate mobility(5).

The Henry's Law constant for thidiazuron is estimated as 3.3X10-13 atm-cu m/mole(SRC), derived from its vapor pressure, 2.3X10-11 mm Hg(1) and water solubility, 20 mg/L(2). This Henry's Law constant indicates that thidiazuron is expected to be essentially nonvolatile from moist soil(SRC) and water surfaces(3). Thidiazuron is not expected to volatilize from dry soil surfaces based upon its vapor pressure.

[(14)C-aniline] thidiazuron was fed at a dose exaggeration of 1.9x to a lactating cow at a rate of 10 ppm for seven days. The animal was sacrificed within 24 hours of administration of the final dose. Parent equivalent radioactivity found was 0.05 ppm, 0.1 ppm, 1.5 ppm, and 1.0 ppm in fat, muscle, kidney and liver, respectively. Radioactivity reached a plateau in milk on the second day (0.2 ppm). Analysis was performed using HPLC and TLC.|[(14)C-aniline] thidiazuron was fed once daily at a dose exaggeration of 100x to six hens for fourteen days at a rate of 8 ppm. Radioactivity did not plateau in eggs during this period. All tissues were first treated with protease and beta-glucuronidase prior to extraction. Parent equivalent radioactivity found was 0.02 ppm, 0.27 ppm, 1.11 ppm, 0.66 ppm, 0.10 ppm, 0.10 ppm and 0.34 ppm in fat, gastrointestinal tract, gastro-intestinal tract contents, liver, muscle, skin and blood, respectively.|In a metabolism study groups of male and female Sprague-Dawley CD rats were dosed with (14)C-thidiazuron [((14)C-aniline) thidiazuron or ((14)C-thiadizaole) thidiazuron (purity: >97% a.i.; batch No: 1695-3 and 1695-4)] at a single oral gavage dose (10 or 1000 mg/kg) or 14-day repeated oral doses of thidiazuron at 10 mg/kg followed by a single oral dose of (14)C-thidiazuron at 10 mg/kg ... The results of the pilot study showed that less than 0.2% of administered radioactivity was eliminated as (14)CO2 from administration of either ((14)C-aniline) thidiazuron or ((14)C-thiadizaole) thidiazuron. In addition, the study showed no significant differences in the percentages eliminated through urine or feces from administration of the two radiolabeled forms. Absorption of thidiazuron was rapid but incomplete at both doses, and appeared decreased at the high dose relative to the low dose. Elimination of thidiazuron was relatively rapid at the single low oral dose level. The major route of elimination was shown to be via urine. The single low, single high, and multiple low oral dose studies indicate that the total radioactivity recovered within 5 days after dosing in the urine and feces were 91-104% of administered dose. At the low dose, the radioactivity recovered in the urine and feces was 60-66% and 29-31% of the dose over a 5-day period, respectively. At the repeated low oral dose, the radioactivity recovered in the urine and feces was 73-75% and 26-28% of the dose over a 5-day period, respectively. At the high dose, the radioactivity recovered in the urine and feces was 41-47% and 56-60% of the dose over a 5-day period, respectively. Administration of a single high dose resulted in a decreased percentage of thidiazuron derived radioactivity eliminated in urine (approximately 20%), with concomitant rise in fecal elimination. This alteration is likely due to reduced absorption of test material at the high dose. Terminal tissue distribution data showed that highest concentrations of thidiazuron derived radioactivity at sacrifice were found in the liver, kidneys, thyroid, whole blood and adrenals at both low and high doses. Repeated oral dosing did not significantly affect distribution of thidiazuron derived radioactivity.|In a dermal penetration study Thidiazuron (99.9 %a.i., batch # OR 1844 (SEL/1098), [phenyl-U-(14)C]-thidiazuron) was administered to 5 male Sprague Dawley CD rats/dose to a 12 sq cm area of the back in a formulation and water dilution thereof at dose levels of 5.0, 0.04 and 0.004 mg/sq cm ... The mean total recoveries were in the range 88% and 99.54% dose for all groups. The amount in the stratum corneum was 0.73%, 10.68% and 8.14% at 24 hours for the high, middle and low dose groups respectively after a 24-hours exposure and 0.41%, 3.24% and 5.37% at 120 hours following 8-hours exposure for the high, middle and low dose groups respectively. However, the results showed that the majority of the radioactive material in the stratum corneum was lost by desquamation and upward renewal of the stratum corneum with time.|Thidiazuron (N-phenyl-N'-1,2,3-thiadiazol- 5-ylurea) cotton defoliant was administered for 10 consecutive days to lactating goats and laying hens. The vast majority of the radioactive material (> 70%) was eliminated in goat urine and feces; less than 1.5% of the administered radioactivity was in the milk. Hens excreted 72% of the total consumed radioactive material during the 10-day feeding period. In addition to the parent compound, which was present in low levels in goat milk and in chicken excreta, eggs, liver, and kidney, N-4-hydroxyphenyl- N'-1,2,3-thiol-5- ylurea or 4-hydroxyphenyl thidiazuron and phenylurea were detected. 4-Hydroxyphenyl thidiazuron was the major thidiazuron metabolite and was present in the free and/or conjugated form in goat and hen excreta, milk, eggs, and certain tissues. Phenylurea was detected only in goat urine. Other unidentified compounds also were present.

Thidiazuron (N-phenyl-N'-1,2,3-thiadiazol- 5-ylurea) cotton defoliant was administered for 10 consecutive days to lactating goats and laying hens. The vast majority of the radioactive material (> 70%) was eliminated in goat urine and feces; less than 1.5% of the administered radioactivity was in the milk. Hens excreted 72% of the total consumed radioactive material during the 10-day feeding period. In addition to the parent compound, which was present in low levels in goat milk and in chicken excreta, eggs, liver, and kidney, N-4-hydroxyphenyl- N'-1,2,3-thiol-5- ylurea or 4-hydroxyphenyl thidiazuron and phenylurea were detected. 4-Hydroxyphenyl thidiazuron was the major thidiazuron metabolite and was present in the free and/or conjugated form in goat and hen excreta, milk, eggs, and certain tissues. Phenylurea was detected only in goat urine. Other unidentified compounds also were present.|/In/ an oral metabolism study in rats ... identification of urinary metabolites indicated the presence of oxidative metabolite (4-hydroxy thidiazuron) in urine and the presence of sulfate and glucuronide conjugates of 4-hydroxy thidiazuron. In feces, the major metabolites identified were 4-hydroxy thidiazuron at the low dose and unmetabolized thidiazuron at the high dose.

/SRP:/ Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR if necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on the left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Poisons A and B/|/SRP:/ Basic treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if needed. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 mL/kg up to 200 mL of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . Cover skin burns with dry sterile dressings after decontamination ... . /Poisons A and B/|/SRP:/ Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Consider administering a beta agonist such as albuterol for severe bronchospasm ... . Monitor cardiac rhythm and treat arrhythmias as necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... . Treat seizures with diazepam or lorazepam ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Poisons A and B/

/SURVEILLANCE/ Since 1992, the Office of Pesticide Program's Incident Data System has only reported 5 incidents as a result of thidiazuron exposure, which all show similar symptoms such as skin rash, nausea, and weakness. However, no medical treatment was required.|/GENOTOXICITY/ In independently performed mammalian cell cytogenetic (chromosome aberration) assays lymphocyte cultures prepared from human peripheral blood were exposed to Thidiazuron (98.7% a.i., Batch/Lot #: CH107623-02) in dimethyl sulfoxide for 4 hours at concentrations of 0, 9.4, 18.75, 37.5, 75, 150, 200, or 250 ug/mL both in the presence and absence of S9-activation, and for 20 hours at concentrations of 0, 4.7, 9.4, 18.75, 37.5, 75, 150, or 200 ug/mL in the absence of S9-activation. Cells were harvested at 20 hours after initiation of treatment. Thidiazuron was tested up to cytotoxic concentrations (mitotic suppression; 53-60% at 150 ug/mL [+/-S9] at 4 hours of exposure and 51% at 37.5 ug/mL [-S9] at 20 hours of exposure). No significant increases in aberration frequency were observed at up to 150 ug/mL (+/-S9) after 4 hours of exposure or at up to 37.5 ug/mL (-S9) after 20 hours of exposure. The positive controls induced the appropriate response. There was no evidence of chromosome aberration induced over background in the presence or absence of S9-activation at either time point.

1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea

Thidiazuron registered formulations include wettable powders (WP) (50 percent active ingredient), soluble concentrates (SC) (12 percent active ingredient), and emulsifiable concentrates (EC) (8.4-50 percent active ingredient).|Dropp 50WP Cotton Defoliant; Active ingredient 50.00% Thidiazuron|Ginstar EC Cotton Defoliant; Active ingredients 6.00% Diuron and 12.00% Thidiazuron|Dropp SC Cotton Defoliant; Active ingredient 41.00% Thidiazuron|For more Formulations/Preparations (Complete) data for Thidiazuron (27 total), please visit the HSDB record page.

The WHO Recommended Classification of Pesticides by Hazard identifies Thidiazuron as unlikely to present an acute hazard in normal use; Main Use: none listed.|The predominant usage is in the major cotton producing areas of the Mid-South, Southeast, and Western United States. Approximately 30% of the annual U.S. cotton crop is treated with thidiazuron.

Method: EPA-OGWDW/TSC 532; Procedure: high performance liquid chromatography with an ultraviolet/visible (UV/Vis) detector; Analyte: thidiazuron; Matrix: drinking waters; Detection Limit: 0.047 ug/L.

Agrochemicals -> Plant Growth Regulators