|Chemical Abstract Number (CAS #)||
|Synonyms||Chlorothalonil||1,3-Benzenedicarbonitrile, 2,4,5,6-tetrachloro-||2,4,5,6-Tetrachloroisophthalonitrile||Daconil 2787||Bravo||Sweep||Vanox
||EPA Method 508||EPA Method 8081
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 &
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.
|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
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 .