Chlorothalonil - Chemical Fact Sheet 9/84
CHEMICAL FACT SHEET FOR:
FACT SHEET NUMBER: 36
DATE ISSUED: SEPTEMBER 30, 1984
1. DESCRIPTION OF CHEMICAL
- Generic Name: Tetrachloroisophthalonitrile
- Common Name: Chlorothalonil
- Trade Name: Bravo, Nopcocide N-96, Daconil, Chlorothalonil Technical
Termil, Groutcide, Mold-Ex, Brovomil
- EPA Shaughnessy Code: 081901
- Chemical Abstracts Service (CAS) Registry Number: 1897-45-6
- Year of Initial Registration: 1966
- Pesticide Type: Fungicide
- Chemical Family: Chlorinated isophthalic acid derivative
- U.S. and Foreign Producers: SDS Biotech Corporation and Griffin
2. USE PATTERNS AND FORMULATIONS
- Application sites: chlorothalonil is a chlorinated isophthalic acid
derivative registered for use as a fungicide to control a wide variety
of fungal diseases on both crop and noncrop sites. Chlorothalonil is
registered for use on numerous crop sites such as fruits, vegetables,
and peanuts. In non-crop applications, chlorothalonil is used on
ornamental sites, on turf, and as a paint and grout additive.
- Types of formulations: chlorothalonil is available in wettable
powder, granular flowable, pelleted/tableted, liquid suspension, and
soluble concentrate formulations.
- Types and methods of applications: chlorothalonil is applied as
follows: broadcast, band, and soil surface using ground or aerial
- Application rates: 0.75 lbs. a.i./A to 3.0 lbs. a.i./A on crop sites;
and 1.125 lbs. a.i./A to 7.5 lbs. a.i./A on non-crop sites.
- Usual carrier: Water
3. SCIENCE FINDINGS
- Technical chlorothalonil is an odorless or slightly pungent, white
crystalline solid. It is stable towards moisture under conventional
conditions and decomposes at 250-251 degrees Celsius. The chemical
does not exhibit any unusual handling hazards. Technical
chlorothalonil contains low amounts of hexachlorobenzene (HCB) and
pentachlorobenzonitrile (PCBN) as manufacturing impurities.
- Technical chlorothalonil is a severe eye irritant, moderately toxic
via inhalation, and of low toxicity via oral and dermal exposures. The
toxicity categories assigned to chlorothalonil are - I for eye
irritation, II for inhalation, III for oral and dermal toxicities, and
IV for dermal irritation.
- Toxicology studies on chlorothalonil are as follows:
- Oral LD50 in rats: > 28.2 mg/kg body weight
- Dermal LD50 in rats: >10 gm/kg body weight
- Skin irritation in rabbits: not an irritant
- Eye irritation in rabbits: severe irritant
- In a two-year rat chronic feeding study, the no-observed-effect-
level was 60 ppm (3 mg/kg body weight). However, it was not
adequate to address the evaluate oncogenic potential of
- In a two-year feeding study in dogs, the no-observed-effect-level
was 60 ppm.
- In a 24-month mouse oncogenicity study, chlorothalonil produced
tumors in renal cortical tubules and squamous tissue of the
stomach, however there was no dose related response. The study
demonstrates that chlorothalonil may have oncogenic potential. An
additional two-year feeding study in rats is considered a data gap.
- In a three-generation rat reproduction study, the no-observed-
effect-level for chlorothalonil is <0.15% of the diet based on
reduced growth and renal and gastric effects. No teratogenic
effects were observed at any dose level tested under the conditions
of the study. Reproductive effects were observed at 0.15% of the
- In a rabbit teratology study and rat teratology study utilizing
chlorothalonil and a rat and a rabbit teratology study utilizing
the 4-hydroxy metabolite, no significant teratogenic effects were
observed at any dose levels tested under the conditions of the
- Chlorothalonil did not demonstrate any mutagenic effects in a
variety of mutagenicity tests.
- The 4-hydroxy metabolite is not oncogenic in rats at doses of 20.0
mg/kg body weight/day Highest Dose Tested (HDT)| or less and in
mice at doses of 215 mg/kg body weight/day (HDT) or less under the
conditions of the study.
- The 4-hydroxy metabolite did not demonstrate any mutagenic effects
in a variety of mutagenicity studies.
Physiological and Biochemical Behavioral Characteristics
- Translocation: chlorothalonil is translocated in plants.
- Mechanism of pesticidal action: The mode of action of chlorothalonil
involves its reaction with thiol groups of the pathogenic fungi's
- Metabolism and persistence in plants and animals: The metabolism of
chlorothalonil is not adequately delineated in both plants and
animals. However, the major metabolite is the 4-hydroxy metabolite.
- The available environmental fate data are insufficient to fully assess
the potential for exposure of humans and non-target organisms to
chlorothalonil. When additional studies are submitted, a complete
environmental exposure assessment can be made. However, chlorothalonil
is moderately mobile in sand and the 4-hydroxy degradate is moderately
mobile in most soils.
- Avian oral LD50: chlorothalonil (>10,000 mg/kg) uses are not expected
to affect avian wildlife. 4-hydroxy degrate (2000 mg/kg), is
moderately toxic to birds. Reproduction studies using both mallard
ducks and bobwhite quail for each, chlorothalonil and the 4-hydroxy
degrate, are required.
- LC50 to fish: chorothalonil (47-84 ppb) is highly toxic to fish. The
4-hydroxy degradate (16-45 ppm) is slightly toxic to fish.
- Fish reproduction: Chlorothalonil may affect fish populations at low
levels (3 - 6.5 ppb).
- LC50 aquatic invertebrates: chlorothalonil is highly toxic to aquatic
invertebrates and may affect their reproduction at low concentrations
- An aquatic field monitoring study is required that reflects residue
concentrations likely to occur under actual use conditions.
- A reassessment of the tolerances cannot be completed at this time. The
residue data on the amounts of impurities in or on the commodities,
the rat oncogenicity/chronic feeding study, and metabolism data, need
to be submitted and evaluated before any assessment of the present
tolerances can be made.
Summary of Science Findings
- Chlorothalonil breaks down in aerobic soil with a half-life of 1 to 2
months with the formation of a major degradate, 4-hydroxy-2,
5,6-trichloroisophthalonitrile, and several lesser degradates. This
breakdown appears to be primarily the result of microbial degradation,
since chlorothalonil is relatively stable to hydrolysis and
photolysis. Chlorothalonil is immobile in most soil types, except sand
in which it is moderately mobile. The 4-hydroxy degradate is
moderately mobile in most soil types.
- Chlorothalonil is not toxic to birds. However, the major degradate is
moderately toxic to birds. Additional studies are required for
chlorothalonil and the 4-hydroxy degradate in order to determine
whether residues of these compounds will produce an effect on the
reproduction of birds.
- Chlorothalonil and its 4-hydroxy degradate are highly toxic to fish,
aquatic invertebrates and marine/estuarine organisms. Low amounts of
residues will affect the reproduction of these organisms. An
additional field monitoring study is required that would record the
effects of residues occurring in water resulting from registered uses
- The metabolism of chlorothalonil in plants and animals is not
adequately elucidated. However the major metabolite is the 4-hydroxy-
2,5,6-trichloroisophthalonitrile. At low concentrations,
chlorothalonil is expected to be excreted in the feces and urine
within 24 hours. The amount of residues expected to be in or on raw
agricultural commodities from use of chlorothalonil will be reassessed
when the data on plant and animal metabolism are submitted along with
the additional residue data.
- The impact of the manufacturing impurities of hexachlorobenzene and
pentachlorobenzonitrile in chlorothalonil cannot be made until plant
and animal residue data is submitted for these impurities.
- Chlorothalonil is a severe eye irritant. It is moderately toxic via
inhalation and demonstrates low toxicity via dermal and oral
exposures. Chlorothalonil is not considered to be mutagenic,
teratogenic, or cause reproductive effects. Studies demonstrated that
the chemical could have oncogenic potential, but additional data are
needed to confirm this.
- The major metabolite is not considered to be an oncogen or mutagen.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- No use, formulation, or geographical restrictions are required.
- Chlorothalonil will be provisionally regulated as an oncogen. This
position is based on a study in which chlorothalonil has exhibited
renal adenomas and carcinomas in male mice and somewhat flawed NCI
studies that indicate an oncogenic effect in the rat, but not in mice.
This position will be reconsidered after the review of the ongoing rat
chronic feeding/oncogenicity study in 1985. As a result of this
evaluation, chlorothalonil may be referred to a Special Review.
- Skin sensitization study is a data gap. However, information received
through the Pesticide Incident Monitoring System indicates that skin
sensitization is a potential problem.
- Unique labeling statements:
- Under Hazards to Humans and Domestic Animals, the words Skin
Sensitizer must be added.
- Under First Aid, the following statement must be added: Note to
Physician: Persons having an allergic reaction respond to treatment
with antihistamines or steroid creams and/or systemic steroids.
- Under Environmental Hazards, the following must be used: This
product is toxic to fish, aquatic invertebrates, and
- Under Directions for Use, the following statements must be added:
Note to User: This product may produce temporary allergic side
effects characterized by redness of the eyes, mild bronchial
irritation and redness or rash on exposed skin areas. Person having
allergic reaction should contact a physician. Note to User: Wear
long sleeve shirt, long pants, and gloves when mixing, loading and
applying this product. Note to User: Do not enter treated area to
perform hand labor within 24 hours of application unless protective
clothing is worn. Note to User: Do not rotate to crops other than
those listed on the label within one year from last application.
Leafy vegetables may be rotated after one year from last
5. SUMMARY OF MAJOR DATA GAPS
- a. The following toxicology data are required:
- An oncogenic study in rats (currently underway) is required to be
submitted within one year.
- A skin sensitization study is required to be submitted within one
- A 21-day subchronic dermal study is required to be submitted
within one year.
- b. The following environmental fate data are required:
- Hydrolysis test, (2)
- Photodegradation test in water, (2)
- Photodegradation test on soil, (2)
- Photodegradation test in air, (2)
- Metabolism test in anaerobic soil, (1)
- Metabolism test in aerobic soil, (1)
- Leaching study, (2)
- Mobility (volatility) test in the laboratory, (2)
- Mobility (volatility) test in the field, (2)
- Dissipation study in soil, (1)
- c. The following ecological effects data are required:
- A field study is needed to determine the effects of residues on
fish and aquatic invertebrate occurring as a result of the
terrestrial use of chlorothalonil. (1)
- Mallard duck and bobwhite quail reproduction study with
chlorothalonil and with it 4-hydroxy degrate are needed. (1)
- d. The following residue chemistry data are required:
- Data related to the manufacturing process, formation of
impurities, preliminary analysis of the technical product,
certification of ingredient limits, analytical methodology, and
- Field residue data for several raw agricultural commodities.
- Studies pertaining to the metabolism of chlorothlonil residues in
plants and animals. (1)
- Residues studies regarding the presence of hexachlorobenzene and
pentachlorobenzonitrile in plants and in animals. (1)
NOTE: (1) Long-term studies must be submitted within 15 months after
receipt of the guidance package. (2) Short-term studies must be
submitted within six months after receipt of the guidance
6. CONTACT PERSON AT EPA
Henry M. Jacoby
Product Manager (21)
Environmental Protection Agency (T5-767C)
401 M Street, S.W.
Washington, DC 20460
DISCLAIMER: THE INFORMATION PRESENTED IN THIS CHEMICAL INFORMATION FACT
SHEET IS FOR INFORMATIONAL PURPOSES ONLY AND NOT TO BE USED TO FULFILL
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.