SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 1897456
CASRN 1897-45-6
SynonymsChlorothalonil
1,3-Benzenedicarbonitrile, 2,4,5,6-tetrachloro-
2,4,5,6-Tetrachloroisophthalonitrile
Daconil 2787
Bravo
Sweep
Vanox
Analytical Methods EPA Method 508
EPA Method 8081
Molecular FormulaC8Cl4N2

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use FUNGICIDE ON A VARIETY OF VEGETABLE CROPS, PEANUTS, LAWNS & TURFS BACTERICIDE; NEMATOCIDE It is effective against a broad range of plant pathogens attacking many agronomic and vegetable crops. Also used as a preservative in paints and adhesives.
Consumption Patterns FUNGICIDE, OF WHICH APPROXIMATELY 63% IS USED ON PEANUTS, 17% ON VEGETABLE CROPS OTHER THAN POTATOES, 9% IN PAINTS, 6% ON POTATOES, & 6% ON LAWNS & TURF (1975)
Apparent Color WHITE CRYSTALLINE SOLID; Pure chlorothalonil forms colorless crystals.
Odor ODORLESS
Boiling Point 350 DEG C @ 760 MM/HG
Melting Point 250-251 DEG C
Molecular Weight 265.89
Density 1.7 @ 25 DEG C/4 DEG C
Environmental Impact Chlorothalonil may be released to the environment primarily during agricultural spraying operations. If released to the atmosphere, degradation of vapor-phase chlorothalonil by reaction with photochemically produced hydroxyl radicals will not be important (estimated half-life of 7 yrs). Photolysis may be important and particulate-phase chlorothalonil will be removed from air via dry deposition. If released to soil, biodegradation may be the primary fate process. Metabolites are isophthalonitrile, mono-, di- and tri- chlorinated isophthalonitriles, 2,5,6-trichloro-4-hydroxyisophthalonitrile and 2,5,6-trichloro-4-methoxyisophthalonitrile. Photolysis may be important on soil surfaces exposed to sunlight and hydrolysis in alkaline moist soils may contribute to the removal of chlorothalonil from soil. Adsorption will take place (Koc of 1,800) resulting in a low amount of leaching. A degradation half-life of 30 days was estimated for chlorothalonil in soil. In water, biodegradation (half-lives of 0.18-8.8 days) will be the primary fate process and hydrolysis in alkaline waters (half-life of 38.1 days at pH 9) may be important. Volatilization will not be important. Exposure of the general population to chlorothalonil may occur through ingestion of contaminated foods as well as inhalation of dust and dermal contact resulting from its use. Workers may be exposed via dermal contact and inhalation of dust.
Environmental Fate Terrestrial Fate: Half-life in soil 1.5-3 mo, depending on moisture content and temperature. TERRESTRIAL FATE: According to all available data in the U.S. Department of Agriculture's Pesticide Properties Database, a degradation half-life of 30 days was estimated for chlorothalonil in soil . One grab sample test indicates rapid biodegradation in soil to: isophthalonitrile, mono-, di- and tri- chlorinated isophthalonitriles, 2,5,6-trichloro-4-hydroxyisophthalonitrile and 2,5,6-trichloro-4-methoxyisophthalonitrile . In moist alkaline soils, hydrolysis probably takes place in conjunction with biodegradation; aqueous hydrolysis half-life of 38.1 days at pH 9 . Chlorothalonil (1 ppm) in benzene solution disappeared in 30 minutes when exposed to sunlight(6) suggesting that chlorothalonil may be removed from soil surfaces via direct photolysis. An experimental Koc value of 1,800 indicates low soil mobility. However, some leaching may occur; chlorothalonil leached into a farm's outflow water during snow melt after the soil had thawed . AQUATIC FATE: Several grab sample tests and a screening study indicate that chlorothalonil will readily biodegrade under aerobic and anaerobic conditions in aquatic ecosystems; half-lives range from 0.18-8.8 days(1-3). Volatilization from water will not be important based on a Henry's Law constant of 2X10-7 atm-cu m/mole at 25 deg C . An experimental Koc value of 1,800(6) indicates adsorption from the water column to sediment and suspended material may occur. A BCF can be estimated to be about 820 based on the water solubility(1,5) indicating that bioconcentration in fish may be an important aquatic fate process. At pH 9, chlorothalonil in water may hydrolyze to 4-hydroxy-2,5,6-trichloro-isophthalonitrile and 3-cyano-2,4,5,6-tetrachlorobenzamide; half-life of 38.1 days(7). ATMOSPHERIC FATE: Based on a reported water solubility of 0.6 mg/L at 25 deg C and a measured Henry's Law constant of 2X10-7 atm-cu m/mole at 25 deg C , the vapor pressure for chlorothalonil can be estimated to be 3.4X10-7 mm Hg at 25 deg C. This vapor pressure value suggests that chlorothalonil will exist in both the vapor- and the particulate-phases in the ambient atmosphere . Vapor-phase chlorothalonil is very slowly degraded in the ambient atmosphere by reaction with photochemically formed hydroxyl radicals; the half-life for this reaction in air can be estimated to be about 7 yrs(1,SRC). Chlorothalonil (1 ppm) in benzene solution disappeared in 30 minutes when exposed to sunlight(6) suggesting that chlorothalonil may be removed from the atmosphere via direct photolysis. Particulate-phase chlorothalonil is removed via dry deposition.
Drinking Water Impact GROUNDWATER: As a result of normal agricultural use, chlorothalonil has been identified in groundwater from 2 states at a maximum concn of 12.6 ppb(1-2). Chlorothalonil residues were detected at concns ranging from 10.1 to 272.2 ug/L in 1982 and 0.4 to 9 ug/L in 1983 in one of two groundwater wells from a commercial farm in southwest Portage la Prairie, Manitoba, Canada . EFFL: On May 4th, 1982, chlorothalonil residues were detected at concns ranging from 0.04-0.74 ug/L in a tile drain outflow from a commercial farm in southwest Portage la Prairie, Manitoba, Canada ; however, chlorothalonil was not applied until July 2, 1982 indicating that chlorothalonil applied in 1981 leached into the outflow water from snow melt after the soil had thawed . In July, August, and September of 1982 after application, chlorothalonil was detected in the tile drain outflow at concns ranging from 0.04-3.66 ug/L .

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