Chemical Properties
White Solid
Uses
Chlorothalonil is a polychlorinated aromatic broad spectrum non-systematic fungicide. Chlorothalonil is used heavily in agriculture field on crops such as peanuts, potatoes and tomatoes. Chlorothaloni
l is a probable human carcinogen (Group B2) and is highly toxic to fish and aquatic invertabrates.
Definition
ChEBI: A dinitrile that is benzene-1,3-dicarbonitrile substituted by four chloro groups. A non-systemic fungicide first introduced in the 1960s, it is used to control a range of diseases in a wide variety of crops.
Uses
Fungicide, bactericide, nematocide. Agricultural and horticultural fungicide.
General Description
Colorless crystals or granules or light gray powder. Melting point 250-251°C. No odor when pure; technical grade has a slightly pungent odor. A fungicide formulated as water-dispersible granules, wettable powder, or dust.
Reactivity Profile
CHLOROTHALONIL(1897-45-6) is stable in neutral or acidic aqueous media. May react violently with strong oxidizing acids [Farm Chemicals Handbook]. Incompatible with other oxidizing agents such as peroxides and epoxides. Breaks down slowly in basic aqueous media (half-life 38.1 days at pH 9. [Farm Chemicals Handbook].
Air & Water Reactions
Insoluble in water.
Potential Exposure
Chlorothalonil is a broad spectrum fungicide; used as fungicide in coatings; caulk, wood preservative, and antifouling systems. Therefore, people involved in its manufacture, formulation, and application can be exposed.
Fire Hazard
Literature sources indicate that this compound is nonflammable.
First aid
If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 2030 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.
Shipping
UN3276 Nitriles, liquid, toxic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required, Potential Inhalation Hazard (Special Provision 5). UN2588 Pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required
Incompatibilities
Contact with strong oxidizers may cause a fire and explosion hazard. Thermal decomposition may include fumes of hydrogen cyanide. 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.
Waste Disposal
Incineration in a unit operating @ 850C equipped with off-gas scrubbing equipment.
Health Hazard
Chlorothalonil is an irritant to
the skin and eyes and has been reported to
produce allergic contact dermatitis in exposed
workers.
Flammability and Explosibility
Notclassified
Agricultural Uses
Fungicide: Chlorothalonil is a broad-spectrum fungicide. It is used on vegetables, peanuts, potatoes, small fruits, trees, turf, roses, ornamentals, and other crops. In California, the top crops are tomatoes, onions, celery, and landscaping. It targets fungal blights, needlecasts, and cankers on conifer
trees. This is the second most used fungicide in the U.S. It can be found in formulations with many other pesticides
Trade name
ATLAS CROPGARD®; BANOL C®; BB CHLOROTHALONIL®; BOMmHgDIER®; BRAVO®; BRAVO® 6 F; BRAVO® 500; BRAVO® 6 F; BRAVO ULTREX®; BRAVO-W-75®; CHILTERN OLE®; CONTACT® 75; DAC® 2787; DACONIL®; DACONIL® 2787 FUNGICIDE; DACONIL® 2787 W; DACONIL® F; DACONIL® M; DACONIL® TURF; DACOSOIL®; DIVA FUNGICIDE®[C]; ECHO®; EXOTHERM®; EXOTHERM TERMIL®; FORTURF®; FUNGINIL®; IMPACT EXCEL®; JUPITAL®; NUOCIDE®; OLE®; PILLARICH®; POWER CHLOROTHALONIL® 50; REPULSE®; RIDOMIL GOLD/BRAVO®; SICLOR®; SIPCAM® UK ROVER 5000; SWEEP®; TER-MIL®; TPN®; TPN (PESTICIDE)®; TRIPART FABER®; TRIPART ULTRAFABER®; TUFFCIDE®
Pharmacology
Mechanism of action of this fungicide may be attributed
to inhibition of physiological activities of fungal cell constituents
by binding reaction. The reaction was observed in
buffer solution to substitute hydroxyethylthio radical(s) of
2-mercaptoethanol for chlorine radical(s) on the benzene
ring of the fungicide molecule preferably at 4-position
(i.e., also 6-) followed by other positions (5). Similar
reactions in fungal cells were observed between the
fungicide and glutathione and high molecular weight cell
constituents having a sulfhydryl group (5,6). The fungicide
inhibits activities of thiol-dependent enzymes such as
alcohol dehydrogenase, gyceraldehyde-3-phosphate dehydrogenase,
and malate dehydrogenase (5,6). Preliminary
addition of glutathione or dithiothreitol protects the thiol
enzymes from inhibition but later addition does not reverse
the enzyme inhibition. Chymotrypsin, a non-thiol enzyme,
was not inhibited by this fungicide. Binding of the fungicide
to the sulfhydryl group of cell constituents appears to
be the primary mode of its action.
Carcinogenicity
Chlorothalonil was not mutagenic in a
variety of assays, nor did it bind to DNA.3 The
compound does not appear to have genotoxic
potential and probably exerts its carcinogenic
action in rodents via a nongenotoxic mechanism.
3 Rodent models may be a poor predictor
of carcinogensis in humans because of species
differences in metabolic pathways leading to
carcinogenesis in the kidney and the lack of a
comparable organ (forestomach) in humans.
The IARC has determined that there is
sufficient evidence for carcinogenicity of
chlorothalonil in experimental animals and
inadequate evidence in humans.
Environmental Fate
Biological. From the first-order biotic and abiotic rate constants of chlorothalonil in
estuarine water and sediment/water systems, the estimated biodegradation half-lives were
8.1–10 and 1.8–5 days, respectively (Walker et al., 1988).
Soil. Metabolites identified in soil were 1,3-dicyano-4-hydroxy-2,5,6-trichlorobenzene,
1,3-dicarbamoyl-2,4,5,6-tetrachlorobenzene and 1-carbamoyl-3-cyano-4-hydroxy-2,5,6-
trichlorobenzene (Rouchaud et al., 1988). The half-life was reported as 4.
Groundwater. According to the U.S. EPA (1986) chlorothalonil has a high potential
to leach to groundwater
Plant. Degrades in plants to 4-hydroxy-2,5,6-trichloroisophthalonitrile (Hartley and
Kidd, 1987), 1,3-dicyano-4-hydroxy-2,5,6-trichlorobenzene and 1,3-dicarbamoyl-2,4,5,6-
tetrachlorobenzene (Rouchaud et al., 1988). No evidence of degradation products were
reported in apple foliage 15 days after application. The half-life of chlorothalonil was 4.1
days (Gilbert, 1976)
Metabolic pathway
By in vitro incubation of 14C-chlorothalonil (CTL) with
rat stomach, duodenum, and cecum contents, with
dog stomach, duodenum, and colon contents, and with
human feces and stomach contents, transformation of
CTL mostly occurs in rat cecum contents, dog colon contents, and human feces, in which unchanged
CTL accounts for 46.7, 29.7, and 22.6% of applied
radioactivity, respectively. In those incubations,
the identified metabolites are 2,5,6-trichloro-4-
methylthioisophthalonitrile, 2,5,6-trichloro-4-
thioisophthalonitrile, 3-thia-1-cyano-2,5,6-
trichloroisoindolinone, 2,5,6-trichloro-4-
hydroxyisophthalonitrile, and 2,5,6-
trichloroisophthalonitrile. In rats, CTL is transformed
to 4,6-bis(N-acetylcystein-S-yl)-2,5-
dichloroisophthalonitrile.
The photolysis of CTL solutions in alcohols
(ethanol and methanol separately) with exposure to
UV irradiation yields 4,5,7-trichloro-6-cyano-3-
methylbenzo-g -lactone and dichlorobenzo-bis-g -lactone
derivatives as major degradation products in ethanol.
In methanol, 4,5,7-trichloro-6-cyanobenzo-g -lactone is
the only photoproduct detected.
Metabolism
Degradation pathways of chlorothalonil in upland and
paddy soils (7) and by soil bacteria (8) were studied,
and most initial products were identified to be the
results of chlorine substitution reactions, by hydrogen
(i.e., dechlorination), by hydroxyl, and by methylthio
groups. These reactions took place first at the 4-position
of the ring followed by reactions at other positions as
in the reaction with thiol compounds. Paddy
soil degraded the fungicide faster than did upland
soil. Chlorine substitution reaction at 4-position of the
fungicide molecule was also reported in benzene solution
under sunlight, and the phenyl-substituted product was
identified (9). Similar photolysis was observed in
other aromatic hydrocarbon solutions but not in acetone,
hexane, and ether solutions.
storage
Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with chlorothalonil you should be trained on its proper handling andstorage. Store in tightly closed containers in a cool, wellventilated area. Metal containers involving the transfer ofthis chemical should be grounded and bonded. Drums mustbe equipped with self-closing valves, pressure vacuumbungs, and flame arresters. Use only nonsparking tools andequipment, especially when opening and closing containersof this chemical. Sources of ignition, such as smoking andopen flames, are prohibited where this chemical is used,handled, or stored in a manner that could create a potentialfire or explosion hazard. A regulated, marked area shouldbe established where this chemical is handled, used, orstored in compliance with OSHA Standard 1910.1045
Degradation
Chlorothalonil is stable to aqueous hydrolysis at pH values above 7. It is
hydrolysed slowly at pH 9 via dechlorination to yield 4-hydroxy-2,5,6-
trichloroisothalonitrile (2) and oxidation/hydration of one of the nitrile
groups to yield 3-cyano-2,4,5,6-tetrachlorobenzamide (3) (Szalkowski and
Stallard, 1977).
Toxicity evaluation
Chlorothalonil’s production and use as a broad-spectrum,
nonsystemic, protectant pesticide results in its direct release to the
environment. Its uses as a wood protectant, antimold and antimildew
agent, bactericide, microbiocide, algaecide, insecticide,
and acaricide are additional routes of release. If released to air,
chlorothalonil will exist in both the vapor and particulate phases
in the ambient atmosphere. Vapor-phase chlorothalonil will be
degraded slowly in the atmosphere by reaction with
photochemically produced hydroxyl radicals (reaction half-life
～7 years). Direct photolysis may also occur. Chlorothalonil is
removed from the atmosphere by wet and dry deposition. If
released to soil, chlorothalonil is expected to have lowmobility or
be immobile, based on Koc values in the range of 900–7000
measured in four soils. Volatilization from moist or dry soil
surfaces is not expected to be important based on a Henry’s Law
constant of 2.5×10-7 atm-cummol-1. Aerobic biodegradation
half-lives of chlorothalonil in four different soils ranged from
10 to 40 days. If released into water, chlorothalonil is expected
to adsorb to suspended solids and sediment in the water column.
