Chloridazon

221.65

221.64

216-920-2

26X5RK7X7W

DTXSID3034872

Colorless solid

2933990017

60.91000

0.73

Colourless, odourless solid; (tech., brown, almost odourless solid)

1.54 g/cm³ @ Temp: 20 °C

206 °C

312.2±52.0 °C at 760 mmHg

142.6±30.7 °C

1.668

25.5 [ug/mL]

0-6°C

4.50X10-7 mm Hg at 20 deg C

Oral-Rat  LD50: 647 mg/kg; Oral-Mouse LD50: 1000 mg/kg

Combustion produces toxic chloride and nitrogen oxide gases

Odorless

Henry's Law constant = 3.33X10-10 atm-cu m/mol at 25 °C (est)

pKa = 3.38 at 25 °C (UV method); pKa = 3.30 at 25 °C (polarography)

141.59 Ų [M+H]+ [CCS Type: TW]|143.06 Ų [M-H]-

DECOMP AT 207 °C|VAPOR PRESSURE = LESS THAN 10 MICROPASCALS AT 20 °C|Hydroxyl radical reaction rate constant = 4.02X10-11 cu cm/molec-sec at 25 °C (est)

NONCORROSIVE

IRRITANT

3077

43-50/53

24-37-60-61

UR6125000

Xi,N

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

STABLE IN ACID MEDIA

P273-P280-P501

H317-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.

USEPA/Office of Pesticide Programs; Reregistration Eligibility Decision Document - Pyrazon EPA 738-F-05-014 (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 February 27, 2007: http://www.epa.gov/pesticides/reregistration/status.htm]

|Warning|H317: May cause an allergic skin reaction [Warning Sensitization, Skin]|P261, P272, P273, P280, P302+P352, P321, P333+P313, P363, P391, and P501|H317 (100%): May cause an allergic skin reaction [Warning Sensitization, Skin]|Aggregated GHS information provided by 286 companies from 3 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.|Not Classified

Handler PPE requirements established by the RED for all pyrazon products. All mixers, loaders, applicators, and other handlers must wear: long-sleeved shirt, long pants, shoes and socks.|Restricted-Entry Interval: Do not enter or allow worker entry into treated areas during the restricted entry interval (REI) of 12 hours. Early Entry Personal Protective Equipment established by the RED: ... minimum ... PPE required for early entry to treated areas that is permitted under the Worker Protection Standard and that involves contact with anything that has been treated, such as plants, soil, or water, is: coveralls, shoes plus socks, chemical-resistant gloves made of any waterproof material.|Pilots must use an enclosed cockpit that meets the requirements listed in the Worker Protection Standard (WPS) for agricultural pesticides [40 CFR 170.240(d)(6)].

DRY POWDER, NONFLAMMABLE.

Remove contaminated clothing and wash skin with soap and water|AVOID CONTACT WITH SKIN, EYES & CLOTHING.|Do not apply directly to water, or to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwater or rinsate. ... Do not apply this product in a way that will contact workers or other persons, either directly or through drift. Only protected handlers may be in the area during application. ... Do not apply this product through any type of irrigation system. Delete any application instructions /on the product labels/ referring to use with irrigation equipment.|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. Users should remove PPE immediately after handling this product. Wash the outside of gloves before removing. As soon as possible, wash thoroughly and change into clean clothing. 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.

SOIL: The concn of pyrazon at four sites in central Chile after treatment was determined by taking integrated core samples up to 30 cm in depth along transects. The results were (time after treatment, concn): 14 days, 590 ppb; 87 days, 9.5 ppb; 205 days, 4.1 ppb; 236 days, 5.1 ppb; 277 days, 2.3 ppb(1).|SEDIMENT: Pyrazon concentrations in suspended solids from the Rhine and Meuse delta, Germany were 0.12 and 0.075 ug/kg dry weight organic matter, respectively, sampled from 1993-1994.

moderately toxic

Pyrazon [5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone], also known as chloridazon, is an herbicide belonging to the pyridazinone class of pesticides. It works as an herbicide by blocking electron transport in photosystem II in green plants, thereby inhibiting photosynthesis. Pyrazon is registered for pre-plant, pre-emergence, and early post-emergence use on sugar beets and red table beets to control certain weeds. Approximately 10% of the U.S. sugar beet crop and 50% of the U.S. table beet crop are treated with pyrazon annually. Pyrazon is also registered for commercial use on ornamentals, including bulb crops and roses. The available toxicity data on pyrazon are adequate to assess the chemical's hazard potential. Pyrazon is an herbicide considered to be of low toxicity without highly specific responses in mammals. Technical pyrazon has low (category III/IV) acute toxicity via the oral, dermal, and inhalation routes of exposure. It is not an eye or skin irritant (category IV) and does not cause dermal sensitization. In longer-term studies, reduced body weight associated with reduced food consumption appears to be the most significant effect of pyrazon exposure in laboratory animals. At higher doses, conditions such as poor general appearance and some motor effects considered to be associated with poor nutrition are noted in rats. In dogs, renal distal tubule vacuolation results at higher doses. No systemic effects resulted from dermal exposure to pyrazon. In both the rat and rabbit prenatal developmental studies, pyrazon did not demonstrate any effects on the fetuses to indicate increased susceptibility. There were no effects on the reproductive performance of rats. Based on the lack of pre- and/or postnatal susceptibility resulting following exposure to pyrazon, and considering the lack of residual uncertainties for pre- and/or postnatal toxicity, no special FQPA safety factor is needed. Therefore, the special FQPA safety factor was reduced to 1X. No neurobehavioral alterations or evidence of neuropathological effects were observed in the available rat and rabbit prenatal developmental toxicity studies or the rat multi-generation reproduction study. In addition, pyrazon is not considered to be neurotoxic from other guideline studies or in open literature reports. Some clinical signs suggesting neurotoxicity were noted at very high doses in the rat, but these were attributed to the weight loss and general poor condition of the rats. Based on the weight of evidence, a developmental neurotoxicity (DNT) study is not required for pyrazon. Pyrazon may be classified as "not likely to be a carcinogen in humans" based on the lack of evidence of carcinogenicity in the rat and mouse carcinogenicity studies.

In the presence of 10 mmol sodium thiocyanate and 0.1 mole sodium nitrite at pH 1 (similar to stomach conditions), 10 mmol pyrazon reacts to n-methyl-nitroso-aniline. When mutagenicity was tested using Escherichia coli K-12 (343/113) in an in vitro system, pyrazon was not mutagenic. The derivatives induced mutations in the presence of metabolically active liver microsomes.

LD50 Rat oral 3600 mg/kg|LD50 Mouse oral 2500 mg/kg|LD50 Guinea pig oral 3200 mg/kg|LD50 Rat oral 2000 mg/kg|For more Non-Human Toxicity Values (Complete) data for PYRAZON (9 total), please visit the HSDB record page.

/BIRDS and MAMMALS/ Birds. The Registrant submitted studies satisfy /EPA/ test guidelines for avian acute oral toxicity (71-1) and avian dietary toxicity (71-2). The oral study conducted with bobwhite quail (Acceptable /to EPA/) yields an oral LD50 of >2,000 mg a.i./kg body weight and an acute oral NOAEL > 1000 mg ai/kg body weight. The dietary studies conducted with mallard duck and bobwhite quail show an LC50 of > 5000 ppm diet for bobwhite quail (Acceptable) and 4254 mg ai/kg diet for mallard duck (Acceptable). Additionally, based on these studies, the dietary NOAEC is 625 mg ai/kg diet (for both Mallard and Bobwhite). Therefore, pyrazon is classified as practically nontoxic to avian species on either an acute oral or an acute dietary basis.|/BIRDS and MAMMALS/ There are exceedances of the acute endangered species LOC (level of concern) for listed birds with every modeled maximum application rate use scenario. There is a potential concern for listed birds species for which the acute LOC is exceeded and for listed species that may be dependent upon birds with LOC exceedances. These concerns are limited to situations where exposure to the stressor actually occurs. Acute RQs (Risk quotients) exceed the endangered species LOC for listed species of mammals for all the maximum use rate scenarios, except for the lowest rate (1.69 lbs a.i./A). The RQs range from 0.1 to 0.4. There are some chronic RQs that exceed the LOC for all the maximum use rate scenarios. RQs range from 1 to 76. There is potential concern for mammalian species for which the LOC is exceeded and for listed species for which there is dependency upon mammals with LOC exceedances. These concerns are limited to situations where exposure to the stressor actually occurs. EPA does not expect pyrazon to pose a significant chronic risk to mammals...|/AQUATIC SPECIES/ The compound was also dangerous to fish, esp the young, @ 50 mg/L in aquaria, it produced 100% mortality in 3 days among crucian carp and guppies.|/AQUATIC SPECIES/ Two studies (test species rainbow trout, and bluegill sunfish /acceptable to EPA/ were submitted to establish the toxicity of pyrazon to freshwater fish. These studies satisfy the guideline requirements for Fresh Warm Water Fish Acute Toxicity (72-1c) and Fresh Cold Water Fish Acute Toxicity (72-1a), respectively. The data show 96-hour LC50 values of 88.7 mg a.i./L in bluegill sunfish and >32 but <46 mg ai/L in rainbow trout. Based on these values, pyrazon is categorized as slightly toxic to freshwater fish on an acute basis. Taking the most conservative approach, this assessment uses the lowest LC50 of 32 mg a.i./L of the rainbow trout as a surrogate to evaluate acute toxic exposure to all freshwater fish species. Using this value may result in an overestimation of risk since the true LC50 is higher than 32 mg ai/L. One acute toxicity study was conducted with the rainbow trout using the principle metabolite B-1. This study (Acceptable) was conducted with rainbow trout. The 96-hour LC50 from this study was >105.5 mg a.i./L Since metabolite B-1 appeared to be less toxic than the parent compound, pyrazon, risks associated with potential exposures to metabolite B-1 were not evaluated quantitatively in this assessment.|For more Ecotoxicity Excerpts (Complete) data for PYRAZON (11 total), please visit the HSDB record page.

Pyrazon's production may result in its release to the environment through various waste streams; it's use as a herbicide on some vegetables and ornamentals such as roses(1) will result in its direct release to the environment(SRC).

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values ranging from 33(2) to 380(3) indicate that pyrazon is expected to have very high to high mobility in soil(SRC). Volatilization of pyrazon from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 3.3X10-10 atm-cu m/mole(SRC), derived from its vapor pressure, 4.5X10-7 mm Hg(4), and water solubility, 400 mg/L(5). Pyrazon is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(4). On soil, a photolysis half-life of 69 days has been reported(6). An aerobic biodegradation half-life of up to 152 days (anaerobic metabolism of 307-607 days depending on soil texture) suggests that biodegradation is not an important environmental fate process in soil(6).|TERRESTRIAL FATE: Pyrazon persistence in soil has been reported as: approximately 6-8 weeks under sufficiently moist conditions(1); 6-7 month at application rates of 4 ppm(5); and 3-6 months at recommended application rates(5). Reported half-lives in soil are 21 days(6) and 10 days in loam soil at 20 °C(4). In a silty clay loam soil (pH 7.7, 1.28% organic carbon) with a 22% water content, the half-lives of pyrazon were 75.6, 21.3, and 13.6 days at 10 °C, 20 °C, and 30 °C, respectively(2). The half-life increased as the water content of the soil decreased(2). At 10 °C, the half-lives were 133.7 and 41.0 days at 15% and 29% soil water content. At 30 °C, the half-lives were 12.2 and 7.9 days at 15% and 29% soil water content, respectively. In field studies in Northern Italy in which 2.2 liters/hectacre of pyrazon were applied pre-emergence with a tractor sprayer with soil sampling performed over 80 days, the disappearance half-life, assuming first-order kinetics, was 68.3 days(2). After 80 days, 36.9% of pyrazon remained in the 0-5 cm layer of soil. The total recovery for all soil layers was 47%. These studies indicate that in the absence of high rainfall, degradation is the main loss process(2). Pyrazon residues were evident at 5-10 cm, 3 days after application but did not reach significant concns at 10-20 cm until 63 days. After 80 days, 3.94% and 8.96% of the applied herbicide was found at 5-10 cm and 10-20 cm depth(2).|TERRESTRIAL FATE: When pyrazon was applied at pre-emergence 1.30 kg/ha to a field plot of sugar beets as formulated products according to normal agricultural practice in spring 1992, typical concns in drain water during spring/summer flows were 0.03 to 0.15 ug/L(1). The field plot in Germany contained loamy silt soil (1.0% Organic Content) and had subsurface drains spaced at 5 to 9 m at an average depth of 80 to 110 cm. Pyrazon was sprayed uniformly by aerial application on two small field plots (25X10 m) in Elazig, Turkey, containing agricultural land never treated with pesticide; soil samples analyzed within a 6-month period showed pyrazon levels of 2.9 and 0.7 mg/kg at the 0-5 cm and 15-20 cm depth, respectively, following an application rate of 3.25 kg active ingredient/ha(2).|AQUATIC FATE: Based on a classification scheme(1), Koc values ranging from 33(2) to 380(3) indicate that pyrazon is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(4) based upon an estimated Henry's Law constant of 3.3X10-10 atm-cu m/mole(SRC), derived from its vapor pressure, 4.5X10-7 mm Hg(5), and water solubility, 300 mg/L(6). According to a classification scheme(7), a BCF range of 2-23(8), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Pyrazon is stable to hydrolysis at pH 5, 7, and 9, with the major route of degradation in water appearing to be photolysis, half-life of 12.5 days(9). A biodegradation half-life of up to 152 days suggests that biodegradation is not an important environmental fate process(9).|ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), pyrazon, which has a vapor pressure of 4.5X10-7 mm Hg at 20 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase pyrazon is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 10 hours(SRC), calculated from its rate constant of 4.0X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase pyrazon may be removed from the air by wet or dry deposition(SRC). Pyrazon half-life in simulated sunlight (xenon lamp. 210 uEinstein sq m/sec) was 150 hrs at pH 7, in water(4). A major route of degradation in water appears to be photolysis, with a half-life of 12.5 days reported(5).

LOSS FROM PHOTODECOMPOSITION AND/OR VOLATILIZATION: NEGLIGIBLE. RESULTANT AVG PERSISTENCE AT RECOMMENDED RATES: 4 TO 8 WK, DEPENDING UPON SOIL MOISTURE & TEMP.|The rate constant for the vapor-phase reaction of pyrazon with photochemically-produced hydroxyl radicals has been estimated as 4.0X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 10 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). The rate constant for the vapor-phase reaction of pyrazon with ozone has been estimated as 1.6X10-18 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(1). This corresponds to an atmospheric half-life of about 7 days at an atmospheric concentration of 7X10+11 ozone molecules per cu cm(2). Pyrazon is stable to hydrolysis at pH 5, 7, and 9(3). Particulate-phase pyrazon may be removed from the air by wet or dry deposition(SRC). Pyrazon half-life in simulated sunlight (xenon lamp. 2100 uEinstein sq m/sec) was 150 hrs at pH 7, in water(3). A photolysis half-life on soil was reported as 69 days(4).|Solar irradiation of pyrazon in aqueous solution in a pyrex flask resulted in approximately a 50% loss in 1 month(1,2). The reaction products were a dimer, 5-amino-4'-chloro-2,2'-diphenyl-4,5-iminodi 3(2H)-pyridazinone, a compound formed by the further polymerization of the dimer, and 2,5,7,10-tetrahydro-2,7-diphenylpyrazino (2,3-d:5,6-d')-dipyridiazine-1,6-dionone(1). The hydrolysis half-life of pyrazon is reportedly 72-144 days(2).

PYRIDAZINONE RING-(SUP) (14) C-LABELED PYRAZON WAS SLOWLY DEGRADED IN WATER. 32 DAYS AFTER APPLICATION IN MODEL ECOSYSTEM, ABOUT 66% OF RADIOACTIVITY IN WATER WAS THE PARENT CMPD. COMBINED PARENT COMPOUND AND METABOLITES IN ORGANISMS LIVING IN THE ECOSYSTEM RANGED FROM 0.06 PPM IN FISH TO 0.6 PPM IN CRAB. ANALYSIS OF CRAB EXTRACTS REVEALED THAT PYRAZON CONSTITUTED ABOUT 76% OF THE TOTAL RADIOACTIVITY IN THAT ORGANISM. THERE WAS NO EVIDENCE TO INDICATE THAT PYRAZON AND ITS DEGRADATION PRODUCTS WERE MAGNIFIED THROUGH THE FOOD CHAIN.|A BCF range of 2-23 was measured in fish for pyrazon(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC). Pyrazon did not accumulate in aquatic organisms in a model ecosystem(4). In the model ecosystem which contained algae, clam, crab, daphnia, elodea, fish, mosquito and snail, Pyrazon (0.476 ppm) and a metabolite of Pyrazon were only detected in crab at the end of the 33 day experiment(4).

120.23 L/kg|Reported Koc values of pyrazon are 120(1), 110(2), 89-340(3) and 33(4). According to a classification scheme(5), this estimated Koc value suggests that pyrazon is expected to have very high to high mobility in soil. Pyrazon does not readily leach through clay, clay loam, sandy loam, sandy clay, or loam soil(6).|The soil-water distribution constant, Kd, of pyrazon to 18 natural surface soils from west central Spain ranged from 0.07 to 5.96 at an equilibrium, concn of 225 ug/mL(1). The study showed the effect of both soil organic matter and smectite content on adsorptivity(1). The slope of the adsorption isotherm was higher for soils with a higher organic matter content or smectite content(1). Aside from the soil with the very high Kd of 5.96, Kd values between 0.54 and 1.73 were obtained from samples with %OC >2.8% or smectite content >8%. Kd values between 0.14 and 0.51 were obtained from samples with %OC between 0.7 and 2.8% or with smectite content <8%. Kd values <0.14 were obtained from samples with %OC <0.7% and without smectite in the clay fraction. Adsorption of pyrazon by oxidized soils, montmorillonite, a clay mineral of the smectite group, and humic acids confirm the effect of organic matter and smectite content on the adsorption of natural soils(1).|Pyrazon was generally slightly mobile when evaluated on 7 soils by thin layer chromatography (TLC)(1). However it was moderately mobile in one soil and relatively immobile in two other soils. The relative mobilities did not appear to correlate with pH or percent organic matter of the soil(SRC). The resulting Rf values ranged from 0.07 to 0.42 with a mean of 0.18. Pyrazon forms well defined complexes with montmorillonite(2). According to IR spectra, the N atom of the pyridazone ring and/or the C=O group are involved in the interaction(2).

The Henry's Law constant for pyrazon is estimated as 3.33X10-10 atm-cu m/mole(SRC) derived from its vapor pressure, 4.5X10-7 mm Hg(1), and water solubility, 400 mg/L(2). This Henry's Law constant indicates that pyrazon is expected to be essentially nonvolatile from water surfaces(3). Pyrazon is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(1).

GROUNDWATER: Pyrazon was not detected, detection limit = 0.004 ug/L, in 22 shallow groundwater samples collected from two sandy and two clayey catchment areas in Denmark between 1993 and 1996(1). A calculated concentration of 1.4 ug/L in deep groundwater has been proposed for groundwater in The Netherlands(2).|DRINKING WATER: In a 1984 monitoring program, pyrazon was not detected in 206 waterwork wells in various parts of the Federal Republic of Germany(1).|SURFACE WATER: A study in an agriculturally important watershed in central Chile from Aug 1991 to June 1992, found that the concn of pyrazon in water at the outlet of the watershed was fairly constant up to 180 days post-treatment with values ranging from 0.43 to 1.38 ppb(1). After 277 days, 15 days after the last rain event, it was not detected(1). Pyrazon was not detected (> 0.05 ppb) in grab samples from the northern tract of the Adige River in northern Italy in April and July 1990(2). Pyrazon has been detected in surface water in The Netherlands(3). The concn was not reported. The concn of pyrazon at Nieuwegein on the Rhine River was 0.72 ug/L(3). This is reported to be the result of accidental spills during 1988-89(3).|RAIN/SNOW/FOG: Forty rainwater collected in Hannover and near Peine (lower Saxony, Germany) in 1992 and were tested for pyrazon(1). Chloridazon was detected at a concentraion range of 0.03 to 0.88 ug/L, mean concentration of 0.06 ug/L, detection limit = 0.03 ug/L(1). The compound was not detected in rainwater samples from the Research Station for Floriculture and Glasshouse Vegetables in Naaldwijk and a relative background area situated at the shore of Lake Nieuwkoopse Plassen in Noorden, both located in the province of South Holland, The Netherlands, sampling taking place in summer, 1997(2).

Occupational exposure to pyrazon may occur through inhalation and dermal contact with this compound at workplaces where pyrazon is produced or used. Use data indicate that the general population may be exposed to pyrazon via drmal contact with this compound and other consumer products containing pyrazon. (SRC)

The toxicokinetic data indicate that pyrazon is readily absorbed by the rat gastrointestinal tract. The major excretory route is via the urine with most being excreted in 24 hours for low doses and 48 hours for higher doses. Biliary excretion is significant but a minor route. Females may excrete Pyrazon at lower rates than males based on the 14 day repeat dose study. Tissue burden is low with up to only 3.28% remaining ... Parent compound was detected only in small amounts in the urine and feces. Minor quantitative differences related to gender were identified.|Approximately half amount of pyrazon /fed/ ... to rabbits was excreted in urine within 24 hr ... Urinary excretion products resulting from oral administration of technical pyrazon /to rabbits/ included...unchanged pyrazon and p-hydroxy metabolite ... also isopyrazon, present in technical formulation as impurity, and its p-hydroxy metabolites. Similar results were obtained with cats and dogs ...|Foliar absorption occurs but is not of major importance to herbicidal action. Translocation from treated leaves is limited. ... Root absorption is rapid and subsequent translocation to all plant parts suggests xylem transport.|In lambsquarters, (Chenopodium album L), pyrazon was accumulate in the leaves but metabolized by roots.|For more Absorption, Distribution and Excretion (Complete) data for PYRAZON (6 total), please visit the HSDB record page.

Approximately half amount of pyrazon /fed/ ... to rabbits was excreted ... /as/ unchanged chemical and ... 2-(p-hydroxyphenyl) analog. ... Similar results were obtained with cats and dogs although ... more p-hydroxy metabolite was excreted than unchanged pyrazon. Studies with pyrazon indicated that 5-amino-4-chloro-3-oxo-(2H)-pyridazine was formed after application to beets. A second metabolite was also detected ... but was not identified.|/Pyrazon/ ... /In rats/ A total of 10 fractions (nine metabolites and one isomer) in the urine and 5 fractions in the feces were noted. The major urinary metabolites were sulfate and glucuronide conjugates and the major fecal metabolite was a p-hydroxy derivative of Pyrazon. The sulfate and glucuronide conjugates and p-hydroxy derivative of pyrazon were recognized as the biliary metabolites ...|A photochemically controlled process was involved in the degradation of pyrazon in the leaves of beets. No degradation occurs in the dark. In sugar beets and red beets, pyrazon formed N-glucosylpyrazone. In addition 5-amino-4-chloro-3(2H)-pyridazinone and a strongly hydrophilic compound were formed.

Pyrazon is a substituted pyridazinone herbicide, which is absorbed through roots and leaves. It inhibits plant growth and survival primarily by four mechanisms: 1) inhibition of the Hill Reaction and photosynthetic carbon dioxide fixation; 2) inhibition of carotenoid biosynthesis; 3) photodestruction of chlorophyll; and 4) interference with incorporation of polar lipids in the membranes of chloroplasts. Resistant plant species, such as beets, have the ability to transform the parent compound to less toxic metabolites in the leaves. Sensitive species (millet and tomatoes, for example) are incapable of this transformation.|Inhibits photosynthesis and the Hill-reaction.

/SIGNS AND SYMPTOMS/ Skin rashes ... are common after repeated exposures...|/CASE REPORTS/ ... When Burex production was initiated in Czechoslovakia, a number of cases of worker injury occurred. Clinical and laboratory findings are reported for seven workers injured by the Burex precursors PCC (1-phenyl-4,5- dichlopyridazone-6) and MCA (mucochloric acid). Contact with these substance produced acute local irritation which gradually developed the character of a second-degree burn. Six to ten days later, when the local changes were beginning to resolve, systemic manifestations began. They were mainly characterized by digestive disorders and by slight liver enlargement in patients with more extensive local injuries. Certain biochemical factors were altered in all patients; SGPT and LDH were increased and serum proteins, mucoproteins, and protein fractions were abnormal for up to 2 months. Photosensitization was also noted. /Burex precursors/|/CASE REPORTS/ Poison Control Center Data - 1993 through 2003 A total of 4 cases were located in Poison Control Center records from 1993 through 2003. Three involved ingestion (2 among adults and one child less than six years old) but none of these cases reported any symptoms. The fourth case was an adult seen a health care facility with nausea, classified as an adverse reaction. California Data - 1982 through 2003 - Only one report from 1985 was attributed to exposure to pyrazon. In this case, a hand applicator accidently sprayed his eyes and face with local symptoms only National Pesticide Information Center - On the list of the top 200 chemicals for which NPIC received calls from 1984-1991 inclusively, Pyrazon was not reported to be involved in human incidents.

1-phenyl-4-amino-5-chloropyridazin-6-one

Use in agriculture in 1989: 8.9% on beets; 91.1% on sugarbeets.|Approximately 10% of the US sugar beet crop and 50% of the US table beet crop are treated with pyrazon annually

PYRAMIN FL HERBICIDE Active Ingredient 41.3% Pyrazon|PYRAMIN DF HERBICIDE Active Ingredient 67.7% Pyrazon|PYRAMIN SUPER HERBICIDE Active Ingredient 42.6% pyrazon|PURAMIN 80% WETTABLE POWDER (65.6% PYRAZON & 14.4% RELATED COMPOUNDS). PYRADEX 10 GRANULAR (5.47% PYRAZON, 1.20% RELATED COMPOUNDS & 3.33% DIALLATE). PYRAMIN PLUS (31% PYRAZON, 21% DALAPON, PLUS WETTING AGENT).|For more Formulations/Preparations (Complete) data for PYRAZON (7 total), please visit the HSDB record page.

3(2H)-Pyridazinone, 5-amino-4-chloro-2-phenyl-: ACTIVE|Pyrazon is formulated as a wettable powder or flowable liquid, and is applied by ground broadcast, with and without soil incorporation, by banded methods and by aerial broadcast methods.|The WHO Recommended Classification of Pesticides by Hazard identifies Chloridazon (technical grade) as unlikely to present an acute hazard in normal use; Main Use: herbicide.|Pyrazon is registered for pre-emergence and early post-emergence application to control weeds in beet crops. Pre-emergence application is made before weeds are more than 2 inches tall. Postemergence applications are made before weeds have more than 2 true leaves but after beets have 2 true leaves. Applications can be made either in the spring or in the fall. Pyrazon is formulated in a wettable powder or as a flowable liquid and is applied through broadcast (for pre-emergence applications) or banded (early post-emergence) methods. In western regions of the U.S., banded preemergence application with sprinkler irrigation or banded, shallow, pre-plant soil incorporation with furrow irrigation is suggested. Pyrazon can also be used as part of pesticide mixtures, including phenmedipham and desmedipham, to control additional weeds. The label-recommended application rate for pyrazon is equivalent to 3 to 3.5 lbs ai/acre with a maximum seasonal application rate of 7.31 lbs ai/acre in certain circumstances. The lower rate (3 lbs a.i./Acre) is for use on sandy loam soils and soils with organic content less than 3%. The higher rate (3.5 lbs ai/acre) is used on loams, silt loams, and clays. The maximum seasonal application rate of 7.31 lbs ai/acre is applicable for single pre-emergence treatment of sugar beet crops in the Red River Valley of Minnesota and North Dakota grown in soils with organic content between 5 and 7 %, and for combined pre-and post-emergence applications to red table beet crops. The label recommended rates are designed to optimize weed control while minimizing crop damage.|Pyrazon, pyramin, is an herbicide primarily used to control weeds in agricultural fields where sugar beets, red beets, and fodder beets are grown. It is sold both as a wettable powder and a liquid. Pyramin products can be applied by ground broadcast, aerial spray, or banding methods, which can result in transport of pyrazon to non-target nearby terrestrial and aquatic areas through spray drift, runoff/erosion, and leaching to groundwater. The maximum annual application rate for pyrazon based on the labels is equivalent to 7.31 lbs active ingredient per acre. The typical application rates (from Biological and Economic Analysis Division (BEAD)) range from 0.9- to 2.6 lbs ai/A, 0.5-0.8 lbs ai/A, 0.9-1.0 lbs ai./A, 0.3-0.6 lbs ai/A, 0.7-1.2 lbs ai/A, and 0.7-0.8 lbs ai/A for California, Idaho, Michigan, North Dakota, Ohio, and Wyoming, respectively. Typical is this case is defined as "average" use rate. Between 2001 and 2003, BEAD estimates of poundage applied to beet and sugar beet crops in the U.S. ranged from 81,000 to 153,000 lbs with an average of 109,000 lb. According to the registrant, the "typical" application rates were 0.41 to 0.54 lb ai/A|For more General Manufacturing Information (Complete) data for PYRAZON (12 total), please visit the HSDB record page.

A METHOD FOR THE ANALYSIS OF TECHNICAL SAMPLES OF PYRAZON BY SPECTROPHOTOMETRY IS PRESENTED.|ACTIVE MATERIAL IS EXTRACTED AND SPLIT WITH METHANOLIC SODIUM HYDROXIDE, OBTAINED ANILINE IS REMOVED BY DISTILLATION AND DETERMINED COLORIMETRICALLY AS AZO-DYE.|AN ANALYTICAL METHOD IS DESCRIBED FOR QUANTITATIVE DETERMINATION OF PYRAZON RESIDUES IN WATER WHICH INVOLVES HIGH PERFORMANCE LIQUID CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION @ 270 NM AND A RANGE FROM 2 PPB TO 1 PPM.|PRODUCT ANALYSIS: ... BY IR SPECTROSCOPY.|For more Analytic Laboratory Methods (Complete) data for PYRAZON (6 total), please visit the HSDB record page.

A SPECTROPHOTOMETRIC METHOD IS DESCRIBED FOR STUDYING PHENAZON IN RABBIT BLOOD SERUM @ A SENSITIVITY OF 4 UG/ML, AND IN THE AIR OF EXPTL ANIMAL CAGES.|Rapid extraction and capillary gas chromatography for diazinine herbicides in body fluids.

Agrochemicals -> Herbicides|Pharmaceuticals|Herbicides|Pesticides -> Herbicides -> Pyridazinone herbicides|Environmental transformation -> Pesticides (parent, predecessor)

Chloridazon has known environmental transformation products that include Chloridazone-desphenyl and Chloridazone-methyl-desphenyl.|Chloridazon has known environmental transformation products that include Chloridazon Metabolite B and Chloridazon Metabolite B-1.