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Chlorothalonil is a chloronitrile fungicide that was first registered by the EPA in 1966. It is used to control fungi affecting a number of agricultural crops, turf, and paint. It may also be used to kill mildew, bacteria, algae, and insects (#EPA).

Chlorothalonil may be sold under names such as Bravo, Chlorothalonil, Daconil 2787, Echo, Exotherm Termil, Forturf, Mold-Ex, Nopcocide N-96, Ole, Pillarich, Repulse, and Tuffcide (#EXTOXNET).

Chemical Description

Chlorothalonil is a grey to colorless solid that is odorless to slightly pungent (#EXTOXNET). It is environmentally persistent and binds strongly with soil (#EPA). The expected half-life in aerobic soils is one to three months (#EXTOXNET).


Chlorothalonil is approved for use on a number of agricultural crops including coffee, tomato, peanut, onion, garlic, potato, beans, and many other food and feed crops. It is used on some commercial grasses such as golf courses, and it can be found in residential products for ornamental plants and lawns. Chlorothalonil may also be formulated in some paints to prevent fungal growth (#EPA).

The heaviest use of chlorothalonil is agricultural. Of all chlorothalonil used annually, roughly 34% is used on peanuts, 12% on potatoes, 10% on golf courses, and 13% on paint (#EPA).

Chlorothalonil is used to target Alternaria blight, anthracnose, botrytis, brown patch of turf, certain cankers, needle casts, certain scabs and curls, downy mildews, powdery mildews, scab, needle cast, snow molds, rusts, and wood rot fungi. It can also be used against some mites and insects (#EPA).

Human Health Effects

Chlorothalonil has a low acute toxicity to humans. The acute oral LD50 exceeds 10,000 mg/kg in rats (#EPA). Chlorothalonil is rapidly excreted from the body (#EXTOXNET).

A two-year study by the National Cancer Institute, in which rats were fed chlorothalonil daily, found renal carcinomas and gland tumors in both females and males. Other similar studies however, have mixed findings on the presence of carcinogenicity. In another two year study on rats, researchers noted increased kidney weight, hyperplasia of the proximal convoluted tubule of the kidneys, and ulcers in addition to renal tumors (#EPA).

The EPA has listed chlorothalonil as a probable carcinogen in the Toxics Release Inventory (#PANNA).

Chlorothalonil may cause redness, pain, and blurred vision if exposed to the eyes. It can cause redness on skin. Inhalation of chlorothalonil can cause burning sensations. Ingesting chlorothalonil may cause abdominal pain and burning sensations (#PANNA).

Environmental Health Effects

Chlorothalonil is practically nontoxic to birds and bees. The LD50 for mallard is 5000 mg/kg (#EXTOXNET).

Chlorothalonil is highly toxic to fish and other aquatic organisms. The LC50 is 0.25 mg/L for rainbow trout, 0.3 mg/L in bluegill, and 0.43 mg/L for channel catfish. Researchers have noted affects on fish at very low levels, under 1 mg/L (#EXTOXNET).

Chlorothalonil has a relatively low mobility in the environment because it has a high affinity for soil (#EPA).


Chlorothalonil is a General Use Pesticide.

Precautionary Notes

Heating chlorothalonil will cause the release of toxic and corrosive gasses (#NIOSH). Use caution so as not to contaminate water.


Environmental Protection Agency. Reregistration Eligibility Decision- Chlorothalonil. (April 1999). [Accessed 9-3-10].

Extension Toxicology Network. Chlorothalonil. (1996). [Accessed 9-3-10].

National Institute for Occupational Safety and Health. Chlorothalonil. [Accessed 9-3-10].

Pesticide Action Network North America. Chlorothalonil. [Accessed 9-3-10].

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