PMEP Home Page --> Pesticide Active Ingredient Information --> Fungicides and Nematicides --> Fungicides, A to E --> Chlorothalonil --> Chlorothalonil - Chemical Fact Sheet 9/84

Chlorothalonil - Chemical Fact Sheet 9/84

                             CHEMICAL FACT SHEET FOR:


                       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
  Chemical Company


- 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

Chemical Characteristics

- 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.

Toxicological Characteristics

- 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
  enzyme systems.
- 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.

Environmental Characteristics

- 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.

Ecological Characteristics

- 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
  (>79 ppb).
- An aquatic field monitoring study is required that reflects residue
  concentrations likely to occur under actual use conditions.

Tolerance Assessments

- 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
  of chlorothalonil.
- 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.


- 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
    marine/estaurine organisms.
  - 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
       physical/chemical characteristics.(2)
     - 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
(703) 557-1800