2,6-Dichlorbenzonitril

Herbicides

Active substance -> EU Pesticides database: Not approved

Pesticides -> Herbicides, Nitrile

Pesticide

Environmental transformation -> Pesticides (parent, predecessor)

Pesticides -> Herbicides

log Kow = 2.74

2.64

2.65

In water, 14.6 mg/L at 20 °C

Solubility in solvents (w/v) (approx): acetone 5% at 8 °C; benzene 5% at 8 °C; cyclohexanone 7% at 15-20 °C; ethanol 5% at 8 °C; furfural 7% at 8 °C; methylene chloride 10% at 20 °C; methylethylketone 7% at 15-20 °C; tetrahydrofuran 9% at 8 °C; toluene 4% at 20 °C; xylene 5% at 8 °C.

Solubility in water: none

518 °F at 760 mmHg (USCG, 1999)

270 °C

270 °C

293 to 294.8 °F (USCG, 1999)

144-145 °C

145-146 °C

Warning

H312: Harmful in contact with skin [Warning Acute toxicity, dermal]

P273, P280, P302+P352, P317, P321, P362+P364, P391, and P501 (click each P-code to see the statement)

Warning

H312 (99%): Harmful in contact with skin [Warning Acute toxicity, dermal]

P273, P280, P302+P352, P317, P321, P362+P364, P391, and P501 (click each P-code to see the statement)

Commission Regulation (EC) No 1490/2002

Dichlobenil is listed in the dataset of EPA Human Health Benchmarks for Pesticides under the Safe Drinking Water Act (40 eCFR 141)

Status: Active Update: 26-08-2022 https://echa.europa.eu/registration-dossier/-/registered-dossier/12680

Dichlobenil: Does not have an individual approval but may be used under an appropriate group standard

The New Jersey Worker and Community Right to Know Act requires public and private employers to provide information about hazardous substances at their workplaces. (N.J.S.A. 34:5A-1 et. seq.)

Class 9

Class 9

Not flammable. (USCG, 1999)

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

Not combustible. Gives off irritating or toxic fumes (or gases) in a fire.

SOLID: Harmful if swallowed. (USCG, 1999)

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

A nitrile herbicide; [Hayes, p. 771] Listed as potential inducer of chloracne; [Rosenstock, p. 714] According to Recognition and Management of Pesticide Poisonings, it has an acute LD50 of greater than 4,460 mg/kg and has minimal toxic, irritant effects. [EPA Pesticides, p. 119] A major metabolite of the herbicide chlorthiamid; Can be absorbed through skin; May cause chloracne; [ICSC] Reports of chloracne in a manufacturing facility; [HSDB] Causes hepatitis in animal experiments; [Reference #1]

The major hazards encountered in the use and handling of dichlobenil stem from its toxicologic properties as a pesticide. Dermal effects appear to be the most common: ranging from possible contact burns to the skin and eyes, to dermatitis, including chloracne. However, dichlobenil also may be fatal if sufficiently high doses are inhaled, swallowed, or absorbed through the skin. Breathing of dichlobenil's aromatic, off-white, crystaline dust, and its contact with skin or eyes should be avoided. Where avoidance is not possible, wear boots and protective clothing, gloves, and goggles (also, a positive pressure breathing apparatus in emergency situations). Remove and isolate contaminated clothing at the exposure site and wash exposed skin well with soap and water, particularly before smoking, eating or using toilet facilities. Formulated dichlobenil is nonflammable. However, when heated to decomposition, it may evolve highly toxic fumes including phosgene or cyanide. If dichlobenil is involved in a fire, extinguish the fire using an agent suitable for the type of surrounding material. Fire-control water should be diked, as necessary to prevent dichlobenil from entering water sources and sewers. While dichlobenil is non-corrosive and thermally stable, it nevertheless should be stored in a cool, dry place, in tightly closed containers, and away from alkalis, feed and feedstuffs. Containers of dichlobenil may be shipped via air, water, road, or rail. Small spills of dichlobenil should be carefully shovelled into a clean dry container (liquid dichlobenil is first absorbed by a non-combustible material, like sand) for later disposal. Large land spills should be deposited in excavated pits, ponds, or holding areas that have been sealed with an impermeable flexible membrane liner (solids also should be covered with plastic sheeting). Spills of dichlobenil in bodies of water, first may need to be treated with activated carbon ... Before permanent land disposal of dichlobenil, consult with environmental regulatory agencies.

Nitriles

Nitriles

FOLMAR EC; US FISH WILDL SERV TECH PAP (88): 1-16 (1977). REVIEW: TOXICITY TABLES FOR HERBICIDES INCL DICHLOBENIL LIST TEST ORGANISMS, TYPES OF TESTS, EXPTL CONDITIONS AND TEST RESULTS. EACH TABLE IS FOLLOWED BY A LIST OF REFERENCES.

Hill EF, Camardese MB; US Fish Wildl Serv Fish Wildl Tech Rep 2: 1-147 (1986). The report provides the most comprehensive data base available for avian subacute dietary toxicity tests and is primarily intended for use in ranking toxicities by a standard method that has a reasonable degree of environmental relevance.

Rice TR JR, Duke TW JR; US Fish Wildlife Serv Circ 335: 1-33 (1970). The effects of dichlobenil on the biota and energy budget of a coastal pond ecosystem.

USEPA/Office of Pesticide Programs; Reregistration Eligibility Decision Document - Dichlobenil. EPA-738-R-98-003 October 1998. 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 7, 2006: http://www.epa.gov/pesticides/reregistration/status.htm]

Tolerances are established for the combined residues of the herbicide dichlobenil (2,6-dichlorobenzonitrile) and its metabolite 2,6-dichlorobenzamide in or on the following raw agricultural commodities: apple; blackberry; blueberry; cranberry; filbert; fruit, stone, group 12; grape; pear; and raspberry.

Based on the reviews of the generic data for the active ingredients dichlobenil, the Agency has sufficient information on the health effects of dichlobenil and on its potential for causing adverse effects in fish and wildlife and the environment. The Agency has determined that Dichlobenil products, labeled and used as specified in this Reregistration Eligibility Decision, will not pose unreasonable risks or adverse effects to humans or the environment with the exception of sewer and granular backpack application use sites. Therefore, the Agency concludes that products containing dichlobenil for the remaining uses are eligible for reregistration under the conditions specified in this RED.

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Dichlobenil is found on List A, which contains most food use pesticides and consists of the 194 chemical cases (or 350 individual active ingredients) for which EPA issued registration standards prior to FIFRA, as amended in 1988. Case No: 0263; Pesticide type: herbicide; Registration Standard Date: 03/23/87; Case Status: RED Approved 09/97; OPP has made a decision that some/all uses of the pesticide are eligible for reregistration, as reflected in a Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): dichlobenil; Data Call-in (DCI) Date(s): 11/22/93, 03/17/94, 10/13/95; AI Status: OPP has completed a Reregistration Eligibility Decision (RED) document for the case/AI.

A halogenated nitrile. Nitriles may polymerize in the presence of metals and some metal compounds. They are incompatible with acids; mixing nitriles with strong oxidizing acids can lead to extremely violent reactions. Nitriles are generally incompatible with other oxidizing agents such as peroxides and epoxides. The combination of bases and nitriles can produce hydrogen cyanide. Nitriles are hydrolyzed in both aqueous acid and base to give carboxylic acids (or salts of carboxylic acids). These reactions generate heat. Peroxides convert nitriles to amides. Nitriles can react vigorously with reducing agents. Acetonitrile and propionitrile are soluble in water, but nitriles higher than propionitrile have low aqueous solubility. They are also insoluble in aqueous acids.

DICHLOBENIL is a chlorinated benzonitrile. Nitriles may polymerize in the presence of metals and some metal compounds. They are incompatible with acids; mixing nitriles with strong oxidizing acids can lead to extremely violent reactions. Nitriles are generally incompatible with other oxidizing agents such as peroxides and epoxides. The combination of bases and nitriles can produce hydrogen cyanide. Nitriles are hydrolyzed in both aqueous acid and base to give carboxylic acids (or salts of carboxylic acids). These reactions generate heat. Peroxides convert nitriles to amides. Nitriles can react vigorously with reducing agents. Acetonitrile and propionitrile are soluble in water, but nitriles higher than propionitrile have low aqueous solubility. They are also insoluble in aqueous acids.

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

In case of fire in the surroundings, use appropriate extinguishing media.

Fresh air, rest.

Remove contaminated clothes. Rinse and then wash skin with water and soap.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Rinse mouth. Do NOT induce vomiting. Refer for medical attention .

Call a physician.

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

TIH (Toxic Inhalation Hazard) - Term used to describe gases and volatile liquids that are toxic when inhaled. Some are TIH materials themselves, e.g., chlorine, and some release TIH gases when spilled in water, e.g., chlorosilanes. [ERG 2016].

The shelf life in storage is at least 2 yr when stored in a cool, dry place. In view of its volatility, the product should be packed in tightly closed containers.

Rooms used for storage only should be soundly constructed and fitted with secure locks. Floors should be kept clear and the pesticides clearly identified. /Pesticides/

Store in a dry place. Do not store with propagative structures such as seeds, bulbs, tubers, nursery stock etc, or with food or feed products.

Provision to contain effluent from fire extinguishing. Separated from oxidants, food and feedstuffs. Store in an area without drain or sewer access.

Safe Storage of Pesticides. Always store pesticides in their original containers, complete with labels that list ingredients, directions for use, and first aid steps in case of accidental poisoning. Never store pesticides in cabinets with or near food, animal feed, or medical supplies. Do not store pesticides in places where flooding is possible or in places where they might spill or leak into wells, drains, ground water, or surface water.

Spills of pesticides at any stage of their storage or handling should be treated with great care. Liquid formulations may be reduced to solid phase by evaporation. Dry sweeping of solids is always hazardous: These should be removed by vacuum cleaning or by dissolving them in water or other solvent in the factory environment. /Pesticides/

Environmental considerations: Land spill: Dig a pit, pond, lagoon, holding area to contain liquid or solid material. /SRP: Pits, ponds, lagoons, soak holes or holding areas used to contain the chemical should be sealed with a impermeable flexible membrane liner./ Cover solids with a plastic sheet to prevent dissolving in rain or fire fighting water.

Environmental considerations: Water spill: If dissolved, in region of 10 ppm or greater concentration, apply activated carbon at ten times the spilled amount.

Personal protection: P2 filter respirator for harmful particles. Do NOT let this chemical enter the environment. Sweep spilled substance into sealable containers; if appropriate, moisten first to prevent dusting. Carefully collect remainder, then remove to safe place.

For more Cleanup Methods (Complete) data for DICHLOBENIL (6 total), please visit the HSDB record page.

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

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.

Safe Disposal of Pesticides. The best way to dispose of small amounts of excess pesticides is to use them - apply them - according to the directions on the label. If you cannot use them, ask your neighbors whether they have a similar pest control problem and can use them. If all of the remaining pesticide cannot be properly used, check with your local solid waste management authority, environmental agency, or health department to find out whether your community has a household hazardous waste collection program or a similar program for getting rid of unwanted, leftover pesticides. These authorities can also inform you of any local requirements for pesticide waste disposal.

Safe Disposal of Pesticides. An empty pesticide container can be as hazardous as a full one because of residues left inside. Never reuse such a container. When empty, a pesticide container should be rinsed carefully three times and the rinsewater thoroughly drained back onto the sprayer or the container previously used to mix the pesticide. Use the rinsewater as a pesticide, following label directions. Replace the cap or closure securely. Dispose of the container according to label instructions. Do not puncture or burn a pressurized container like an aerosol - it could explode. Do cut or puncture other empty pesticide containers made of metal or plastic to prevent someone from reusing them. Wrap the empty container and put it in the trash after you have rinsed it.

Personal protection: particulate filter respirator adapted to the airborne concentration of the substance. Do NOT let this chemical enter the environment. Sweep spilled substance into covered sealable containers. If appropriate, moisten first to prevent dusting. Carefully collect remainder. Then store and dispose of according to local regulations.

Antidotes to cyanide poisoning include hydroxocobalamin and sodium nitrite, which release the cyanide from the cytochrome system, and rhodanase, which is an enzyme occurring naturally in mammals that combines serum cyanide with thiosulfate, producing comparatively harmless thiocyanate. Oxygen therapy can also be administered. (L97)

Twenty-four hours following injection of a single dose of the herbicide dichlobenil (2,6-dichlorobenzonitrile) in C57Bl/6 mice a steep dose-response curve for the histopathological toxicity in the olfactory mucosa was observed. Four hours following injection of a toxic dose of [ring-14C]dichlobenil (12 mg/kg) the covalent binding in the olfactory mucosa was 26 times higher than that in the liver. A dose-dependent decrease of nonprotein sulfhydryls (mainly glutathione, GSH) in the olfactory mucosa was observed 2.5 hr following injection of dichlobenil (6, 12, 25 mg/kg). The synthetic GSH precursor N-acetyl-L-cysteine decreased both the dichlobenil-induced toxicity and the covalent binding, whereas N-acetyl-D-cysteine had no effect. No protective effects of the cyanide antidotes nitrite, thiosulfate, or superoxide dismutase on the dichlobenil-induced toxicity were observed. In mice given the GSH-depleting agent phorone and a subtoxic dose of dichlobenil (6 mg/kg), an extensive toxicity and an increased covalent binding in the olfactory mucosa were demonstrated. Autoradiography showed no change in the distribution of covalent (14)C dichlobenil binding to nontarget tissues of phorone-treated mice. In conclusion, the results demonstrate a relationship between the degrees of covalent binding, GSH depletion, and toxicity of dichlobenil in the olfactory mucosa. Hence, the level of GSH appears to be of importance for the dichlobenil-induced toxicity in the olfactory mucosa.

Treatment with 3-aminobenzamide decreased the toxicity and covalent binding of dichlobenil (2,6-dichlorobenzonitrile; 12 mg/kg; i.p.) in the mouse olfactory mucosa.

Exposure to high levels of cyanide for a short time harms the brain and heart and can even cause coma, seizures, apnea, cardiac arrest and death. Chronic inhalation of cyanide causes breathing difficulties, chest pain, vomiting, blood changes, headaches, and enlargement of the thyroid gland. Skin contact with cyanide salts can irritate and produce sores. (L96, L97)

LC50 Ctenopharyngodon idella (grass carp) 14 mg/L/24 hr at 18 to 21 °C (95% confidence limit 11 to 16 mg/L)

LC50 Ctenopharyngodon idella (grass carp) 12 mg/L/48 hr at 18 to 21 °C (95% confidence limit 9.2 to 15 mg/L)

LC50 Ctenopharyngodon idella (grass Carp) 9.4 mg/L/96 hr at 18 to 21 °C (95% confidence limit 7.5 to 12 mg/L)

LC50 Salmo gairdneri (rainbow trout) 140 mg/L/96 hr at 12 °C /weight of test organism= 2.6 g, using 100% technical material of 2,6-dichlorobenzoic acid metabolite/. 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.

For more Ecotoxicity Values (Complete) data for DICHLOBENIL (48 total), please visit the HSDB record page.

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values of 49-323 measured in several soils(2), indicates that dichlobenil is expected to have high to moderate mobility in soil(SRC). Volatilization of dichlobenil from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.0X10-5 atm-cu m/mole(SRC), derived from its vapor pressure, 6.6X10-4 mm Hg(3), and water solubility, 14.6 mg/L(3). Dichlobenil is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(3). The half-life of dichlobenil in soil is typically 1-6 months depending upon soil type, with 2,6-dichlorobenzamide (which is slowly degraded to 2,6-dichlorobenzoic acid) observed as a major metabolite(3). Field studies using a sandy soil plot and application rates of 8.3 and 16.6 kg/ha indicate that the overall persistence time of dichlobenil is approximately one year(4). An initial half-life of approximately 4 weeks was observed for surface applied dichlobenil, which was primarily due to volatilization losses. Incorporation of the granules into the soil by mechanical tillage, resulted in significantly longer persistence due to a decreased rate of volatilization(4).

TERRESTRIAL FIELD DISSIPATION: Dichlobenil dissipated with a calculated half-life of 241 days from the upper 3 inches of silt loam soil in field plots that were planted to arborvitae in Hillsboro, Oregon. The average dichlobenil concentrations from the deeper soil layers were <0.024 ppm at all sampling intervals except for 0.084 ppm in the 48 inch to 58 inch depth. There were dichlobenil detections at 36-48, 48-50, and 50-60 inches. The degradate, 2,6- dichlorobenzamide, was detected to a depth of 96 inches(1). Dichlobenil degraded from sandy loam soil with a calculated half-life of 13 weeks; most of the dissipation was due to volatilization of dichlobenil(1). Of the 61.0% of total 14C trapped, 56.8% was 14C-dichlobenil and 2.3% was 14CO2. When correcting for the volatilization, the calculated half-life of dichlobenil was 46.3 weeks. One degradate identified, 2,6-dichlorobenzamide, was 13.1% (maximum concentration) at 50 weeks(1). Dichlobenil dissipated with a calculated half-life of 3.7 months from the upper 3 inches of a loamy sand soil in an established commercial apple orchard located in the Town of Huron, New York; the orchard was treated with dichlobenil (Norosac, 4% G) at 6 lb ai/A on May 18, 1987(1). Dichlobenil was detected to a 12-inch depth in the treated plots. The degradate 2,6-dichlorobenzamide was detected to a depth of 72 inches(1). Dichlobenil dissipated with a calculated half-life of 16 days from the upper 3 inches of Hanford sandy loam soil located in Madera, California(1). A loss of 80% of the applied dichlobenil was not accounted for after a 7-day period and was attributed to volatilization. Dichlobenil was detected at a 6-inch soil depth in the treated plots. The degradate 2,6-dichlorobenzamide was consistently detected to a 48-inch soil depth.

IN SOIL, HALF-LIFE ... WAS 28 WK @ 6.7 °C (AFTER INITIAL 10 WK LAG PERIOD) & 19 WK @ 26.7 °C. ... THE ONLY DETECTABLE METABOLITE WAS 2,6-DICHLOROBENZAMIDE.

KALE PLANTS WERE EXPOSED TO DICHLOBENIL SOLN THROUGH ... SOIL TREATMENT. ... HALF-LIFE OF DICHLOBENIL @ 2.5 MG/POT WAS 44 DAYS; @ 0.5 MG/POT WAS 46 DAYS; & @ 0.25 MG/POT WAS 46 DAYS.

For more Environmental Fate (Complete) data for DICHLOBENIL (7 total), please visit the HSDB record page.

Dichlobenil has frequently been identified as a pesticide detected in food items under the FDA Pesticide Residue Monitoring Program. Dichlobenil was identified, not quantified, in an undisclosed number of food items under the Pesticide Residue Monitoring Program each year from 1993-1994, and 2000-2003(1). No detections were reported for food items from the 1995-1999 surveys(1). Dichlobenil was identified, not quantified, in a single orange sample during an analysis of the Pesticide Residue Monitoring Program from 1989-1991(2).

The substance can be absorbed into the body by inhalation, through the skin and by ingestion.

Oral (L96) ; inhalation (L96) ; dermal (L96)

Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)

/BIRDS and MAMMALS/ Dichlobenil was tested in a 5 day diet of young 14 day old Japanese Quail and a 10 day old ring-necked pheasant. There was no mortality at 1250 ppm, 12% at 2500 ppm, and 19% at 5000 ppm in the quail. LC50 in pheasant was approx 1500.

/AQUATIC SPECIES/ Only 0.31-1.28 mg dichlobenil/L caused hypertrophy and hyperplasia of gill epithelial cells in rainbow trout and the accumulation of dichlobenil in the tissues was concentration related.

/AQUATIC SPECIES/ Goldfish were treated for 3 months with dichlobenil. Body wt was decrease & the behavior of the animals was abnormal only at the highest concentration (6.4 mg/L) tested. The no toxic effect level for goldfish and continuous exposure during 3 months may be given as between 0.4 and 1.6 mg/L in water. The corresponding no toxic effect residue in the whole fish is between 8 and 29 ppm.

/AQUATIC SPECIES/ ... Catfish, exposed to a 20 ppm dose of dichlobenil displayed a reduction in G alpha q/G alpha 11 antigenicity.

For more Ecotoxicity Excerpts (Complete) data for DICHLOBENIL (8 total), please visit the HSDB record page.

Cough.

MAY BE ABSORBED!

Redness.

Cyanide poisoning is identified by rapid, deep breathing and shortness of breath, general weakness, giddiness, headaches, vertigo, confusion, convulsions/seizures and eventually loss of consciousness. (L96, L97)

Tolerances are established for the combined residues of the herbicide dichlobenil (2,6-dichlorobenzonitrile) and its metabolite 2,6-dichlorobenzamide in or on the following raw agricultural commodities: apple; blackberry; blueberry; cranberry; filbert; fruit, stone, group 12; grape; pear; and raspberry.

Based on the reviews of the generic data for the active ingredients dichlobenil, the Agency has sufficient information on the health effects of dichlobenil and on its potential for causing adverse effects in fish and wildlife and the environment. The Agency has determined that Dichlobenil products, labeled and used as specified in this Reregistration Eligibility Decision, will not pose unreasonable risks or adverse effects to humans or the environment with the exception of sewer and granular backpack application use sites. Therefore, the Agency concludes that products containing dichlobenil for the remaining uses are eligible for reregistration under the conditions specified in this RED.

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Dichlobenil is found on List A, which contains most food use pesticides and consists of the 194 chemical cases (or 350 individual active ingredients) for which EPA issued registration standards prior to FIFRA, as amended in 1988. Case No: 0263; Pesticide type: herbicide; Registration Standard Date: 03/23/87; Case Status: RED Approved 09/97; OPP has made a decision that some/all uses of the pesticide are eligible for reregistration, as reflected in a Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): dichlobenil; Data Call-in (DCI) Date(s): 11/22/93, 03/17/94, 10/13/95; AI Status: OPP has completed a Reregistration Eligibility Decision (RED) document for the case/AI.

Persons in charge of vessels or facilities are required to notify the National Response Center (NRC) immediately, when there is a release of this designated hazardous substance, in an amount equal to or greater than its reportable quantity of 100 lb or 45.4 kg. The toll free number of the NRC is (800) 424-8802. The rule for determining when notification is required is stated in 40 CFR 302.4 (section IV. D.3.b).

Dichlobenil is designated as a hazardous substance under section 311(b)(2)(A) of the Federal Water Pollution Control Act and further regulated by the Clean Water Act Amendments of 1977 and 1978. These regulations apply to discharges of this substance. This designation includes any isomers and hydrates, as well as any solutions and mixtures containing this substance.

Dichlobenil acts primarily on growing points and root tips. Definite characteristics at the toxic level in intact plants include a rapid growth inhibition, followed by a gross disruption of tissues, notably in the meristems and phloem, which may result in the swelling or collapse of stem, root, and petiole, and a generalized brown discoloration, frequently accompanied by the exudation of gummy material from shoots.

Soil applied dichlobenil (2 lb/acre) destroyed phloem, cambium, and associated parenchyma in and above nodes of alligator weed ... Injury to inactive axillary bud tissues was limited... .

Selective systemic herbicide, absorbed by the roots and leaves, with rapid translocation acropetally and slower translocation basipetally. Inhibits actively dividing meristems and germination of seeds, and damages rhizomes. Has no effect on cell respiration or photosynthesis, but inhibits cellulose synthesis.

24 hr following injection of a single dose of the herbicide dichlobenil (2,6-dichlorobenzonitrile) in C57Bl/6 mice a steep dose-response curve for the histopathological toxicity in the olfactory mucosa was observed. 4 hr following injection of a toxic dose of (14)C-dichlobenil (12 mg/kg) the covalent binding in the olfactory mucosa was 26 times higher than that in the liver. A dose-dependent decrease of nonprotein sulfhydryls (mainly glutathione, GSH) in the olfactory mucosa was observed 2.5 hr following injection of dichlobenil (6, 12, 25 mg/kg). The synthetic GSH precursor N-acetyl-L-cysteine decreased both the dichlobenil-induced toxicity and the covalent binding, whereas N-acetyl-D-cysteine had no effect. No protective effects of the cyanide antidotes nitrite, thiosulfate, or superoxide dismutase on the dichlobenil-induced toxicity were observed. In mice given the GSH-depleting agent phorone and a subtoxic dose of dichlobenil (6 mg/kg), an extensive toxicity and an increased covalent binding in the olfactory mucosa were demonstrated. Autoradiography showed no change in the distribution of covalent (14)C dichlobenil binding to nontarget tissues of phorone-treated mice. In conclusion, the results demonstrate a relationship between the degrees of covalent binding, GSH depletion, and toxicity of dichlobenil in the olfactory mucosa. Hence, the level of GSH appears to be of importance for the dichlobenil-induced toxicity in the olfactory mucosa.

The metabolic activation of the herbicide dichlobenil (2,6-dichloro (ring-(14)C) benzonitrile) in the olfactory mucosa of C57BL mice and Sprague Dawley rats was examined. In homogenates of the olfactory mucosa (mouse 1000 x g supernatants; rat microsomes), dichlobenil was metabolized and covalently bound to protein. The apparent Km, Vmax and V/K values showed that the olfactory mucosa had both a higher affinity for dichlobenil and a higher capacity/mg protein to activate dichlobenil in comparison to the liver. The covalent binding was dependent on NADPH and was inhibited by the addition of dithionite, metyrapone and glutathione indicating an oxidative cytochrome P-450 dependent activation of dichlobenil into an electrophilic intermediate. The covalent binding was also inhibited by the addition of superoxide dismutase whereas catalase, mannitol or dimethylsulfoxide had no effect indicating the involvement of O2- but not of H2O2 or OH. in the activation. In explants of the olfactory mucosa incubated with (14)C dichlobenil a preferential covalent binding was observed in the Bowman's glands suggesting an activation of dichlobenil in these structures. The highly efficient metabolic activation of dichlobenil to reactive intermediates in the olfactory mucosa is suggested to be of importance for the potent dichlobenil-induced toxicity in this tissue.

In the unhydrolyzed urine of rats ... Metabolites were found: 2,6-dichloro-3-hydroxybenzonitrile and 2,6-dichloro-4-hydroxybenzonitrile and their glucuronides and sulfate, and the ester glucuronides of 2,6-dichlorobenzoic acid and 2,6-dichloro-3-hydroxybenzoic acid. An unknown aromatic acid and two sulfur containing metabolites--possibly mercapturic compounds--were also observed. ... Urine of rabbits & rats fed dichlobenil showed the presence of residues in amounts of 2% and 6%, respectively ... in the form of the 4-hydroxy analog; & 23% and 22%, respectively, in form of the 3-hydroxy analog. The hippurate conjugate was also observed ... .

When dichlobenil was applied to soil surrounding 8-yr-old apple trees ... leaves accumulated dichlobenil, BAM /2,6-dichlorobenzamide/, 2,6-dichloro-3-(& 4-) hydroxybenzamide, 2,6-dichloro-3-(& 4-) hydroxybenzonitriles, & some unidentified material ... /In Phaseolus vulgaris l/ seedlings ... hydroxylation, followed by conjugation, is primary pathway. In addition to formation of 2,6-dichloro-3-(& 4-) hydroxybenzonitrile ... hydrolysis of dichlobenil to 2,6-dichlorbenzamide & 2,6-dichlorobenzoic acid also occurred. Seedlings of wheat ... & rice ... were exposed to labeled dichlobenil by immersion of their roots in /water/ solution ... In wheat /& in rice at lower rate it/ ... was hydroxylated to 3- and 4-hydroxy analogs & converted to soluble and insoluble conjugates.

When dichlobenil was applied to water cress, Rorippa nasturtium-aquaticum, chromatography indicated the presence of the 3-OH and 4-OH analogs in roots and 2,6-dichlorobenzamide in the stems. The 3-OH and 4-OH compounds seemed to be present in stems and roots of narrow-leafed water parsnip, Berula erecta and 2,6-dichlorobenzamide possibly present in Berula erecta leaves. The 3-OH and 4-OH metabolites were present in all regions of reedgrass, Phragmites commums.

Hydrolysis of the nitrile group and hydroxylation at the 3-position of the phenyl ring of dichlobenil are the main metabolic routes in the initial degradation step, but all routes eventually yield the polar metabolite, 3-hydroxy-2,6-dichlorobenzoic acid.

For more Metabolism/Metabolites (Complete) data for DICHLOBENIL (9 total), please visit the HSDB record page.

2,6-dichlorobenzonitrile has known human metabolites that include 2,4-dichloro-7-oxabicyclo[4.1.0]hepta-2,4-diene-3-carbonitrile and 1,3-dichloro-7-oxabicyclo[4.1.0]hepta-3,5-diene-2-carbonitrile.

Dogs (Beagles) & rats (Porter strain) did not show species differences in patterns of elimination of metabolites ... Single labeled doses ... were almost entirely eliminated in 4 days. Less than 0.5% ... was present in carcass & viscera after removal of gut ... upwards of 60% appeared in urine.

Roots and cut stems readily absorb dichlobenil from aqueous or nutrient solutions... . Dichlobenil is often absorbed and accumulated in root tissues... before it is translocated upward. ...Under favorable concentration gradients, root-absorbed dichlobenil was excreted back into nutrient solution.

...Radiocarbon from (14)carbon dichlobenil accumulates in parenchyma cells surrounding main veins of bean seedling leaves. Movement and accumulation of radiocarbon in these cells may be result of... transport via intercellular space or across the plasma lemma, adsorption to chloroplasts or other cellular components, and immobilization of conjugated phenolic metabolites as bound "terminal" residues ... (14)carbon balance and vapor-trapping studies have established that substantial amount of translocated radiocarbon is rapidly lost as... dichlobenil by evaporation from aerial portions of intact plants. ...It is also absorbed and translocated by aerial portions of plant. Absorption has been reported... from vapor... and from lanolin paste ... It was translocated in acropetal direction with very limited basipetal movement... .

Studies with (14)carbon dichlobenil showed that more of it was absorbed by rabbits than by rats. ... Unchanged dichlobenil was not found in the urine but was found in the feces.

For more Absorption, Distribution and Excretion (Complete) data for DICHLOBENIL (8 total), please visit the HSDB record page.

Used as herbicide for cranberry bogs, orchards, vineyards, berry fields, ornamentals, nurseries, public easements, industrial areas, railroads, and sewers; Also used as a preservative (adhesives and industrial); [HSDB] Casoron G (67.5% active ingredient): Ready-to-use granular formulation used in the EU for weed control in vineyards; [EFSA]

Working with Glues and Adhesives [Category: Other]

For Dichlobenil (USEPA/OPP Pesticide Code: 027401) ACTIVE products with label matches. /SRP: Registered for use in the U.S. but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./

Herbicide (eg, weed growth inhibitor for fruit trees)

Casoron for weed control in cranberry bogs, orchards, nurseries, ornamentals, vineyards, public green areas, industrial sites, railway lines and under asphalt.

Industrial preservatives (adhesives, industrial)

(1977) 3.24X10+5 G (PRINCPL CUSTMS DISTS)

(1982) 7.06X10+10 G (PRINCPL CUSTMS DISTS)

(1977) Not produced commercially in USA

(1982) Not produced commercially in USA

Chlorination of 2,6-dichlorotoluene followed by hydrolysis to aldehyde, conversion to oxime & dehydration.

... Method of synthesis involved joint oxidation of 2,6-dichlorotoluene & ammonia with vanadium pentoxide catalyst at 360 °C. Other methods ... include chlorination of either 2-chloro-6-nitrobenzonitrile or 2-amino-6-chlorobenzonitrile ... .

... Friedel-crafts reaction of 2,6-dichlorobenzamide with mixed chloride salt (NaCl.AlCl3) was reported for synthesis ... .

Made from 2,6-dichlorotoluene via the benzaldehyde ... .

Reaction of 2,6-dichlorobenzaldehyde with hydroxylamine monosulfonate to form anti-2,6-dichlorobenzaldoxime & ... /then/ dehydration ... in boiling acetic anhydride ... .

USEPA/OPP Pesticide Code 027401; Trade Names: Casoron, Prefix D, Nia 5996, H 133, Du-sprex, Norosac.

59% wettable powder; 75% granules.

Available formulations are 'Casoron' wp, 'Casoron g', containing 45% & 6.75% dichlobenil respectively.

Technical grade dichlobenil is > or =98% pure.

For more Formulations/Preparations (Complete) data for DICHLOBENIL (9 total), please visit the HSDB record page.

Environmental transformation -> Pesticides (parent, predecessor)

Pesticides -> Herbicides

HERBICIDES

Applications using normal herbicidal rates remain effective for a period of 2-6 mo, under favorable conditions even for a period of 1 yr.

For germinating seeds, rhizomes, & young seedlings; early postemergence spring application in tolerant crops is recommended.

Recommended rates are: for selective post-emergence control on fruit & other crops 2.5-10 kg/hectare; for aquatic weed control 4.5-12 kg/hectare; for total weed control < -20 kg/hectare.

Some conifers are susceptible to dichlobenil vapor, due to their bark structure.

The maximum application rate was reduced in 1998 from 20 lbs ai/acre to 10 lbs ai/acre