| Chemical Abstract Number (CAS #) |
21725462
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| CASRN |
21725-46-2 |
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| Synonyms | Cyanazine |
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2-[[4-chloro-6-(ethylamino)-8-triazin-2-yl]amino]-2-methylpropionitrile |
| Analytical Method |
EPA Method 629 |
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| Molecular Formula | C9H13ClN6 |
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Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound. |
| Use | A pre and postemergence herbicide for control of annual grasses and broadleaf weeds.
Early preplant, preemergence or postemergence for field corn. Weed control on fallow cropland.
Outside US for soybeans, oil seed rape, peas and forestry.
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| Apparent Color | White crystalline solid
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| Melting Point | 166.5 - 167 deg C
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| Molecular Weight | 240.7
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| Environmental Impact | Cyanazine is released directly to the environment through its use and application as an
agricultural herbicide. It can undergo surface runoff (via rainfall or irrigation), with subsequent
transport to rivers and lakes, after being applied to fields as a herbicide. If released to soil,
microbial degradation is reported to be the major environmental degradation process. Cyanazine
has moderate mobility in soil; its detection in various ground waters demonstrates that it can
leach. The half-life in soil typically ranges from 12 to 25 days; the USDA's lists a soil half-life of
14 days. If released to water, cyanazine may degrade through microbial degradation and catalyzed
hydrolysis. Un-catalyzed hydrolysis is slow (200 days or more at 25 deg C and pH 5.5-9); natural
water and soil constituents, such as humic and fulvic acid, may catalyze the chemical hydrolysis.
Volatilization from water or soils is not expected to be an important fate process. If released to
the atmosphere, cyanazine can exist in both the vapor and particulate phases; vapor phase
cyanazine degrades readily by reaction with photochemically produced hydroxyl radicals
(estimated half-life of 3 hours). Physical removal from the atmosphere occurs through wet and dry
deposition. Occupational exposure to cyanazine occurs through dermal contact and inhalation of
dust.
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| Environmental Fate | Cyanazine was applied to plots having tile drains. Corn was grown in these plotsand
water samples were collected from the tile outlets. Analyses of the water, using GLC and several
different detectors and columns, indicated the presence of cyanazine amide in addition to
unchanged cyanazine. Some hydroxycyanazine was observed in the soil.
Terrestrial fate: Laboratory tests show that the nitrile group is hydrolysed in plants and soil to
the corresponding carboxylic acid. The chlorine atom may also be replaced by a hydroxy group,
which sometimes forms conjugates. These degradation products have not been detected in crops
following field use.
TERRESTRIAL FATE: Cyanazine is degraded in soil primarily through microbial activity .
Catalyzed aqueous hydrolysis may contribute to its degradation in moist soil ; soil constituents
such as humic and fulvic acid are potential catalytic agents . Cyanazine is reversibly adsorbed to
soil particles ; the degree of adsorption varies with soil texture, water content, organic matter
content and pH . A Koc value of 190 indicates moderate mobility in soil. Detection in
various US ground waters demonstrates that leaching is potentially an important transport
process. Field loss through rainfall runoff can amount to 0.07-1.0% of field application .
Under field conditions, loss through volatilization or photodecomposition is minor . The
half-life in soil typically ranges from 12 to 25 days ; the USDA'S Pesticide Properties Database
lists a soil half-life of 14 days .
TERRESTRIAL FATE: In 1967 to 1970 field trails, the half-life of cyanazine ranged from 1.3 to
5 weeks ; breakdown of cyanazine in soil occurred (at least partially) through hydrolysis of the
nitrile group to the amide and then to the acid ; some hydrolysis of the 2-chloro group also
occurred ; after 32 days, the major degradation product was the acid, together with small
amounts of the hydroxy acid . In another cyanazine metabolite study, cyanazine amide and
de-isopropylated atrazine were detected as soil degradation products ; it was proposed that
hydrolysis preceded microbial degradation to yield the de-isopropylated atrazine . Persistence
studies over a 20-week period at varying temperatures (5, 20, 35 and 50 deg C) found that
cyanazine degraded within 10 weeks at 5 deg C and within 5 weeks at the higher temperatures ;
the initial observed half-lives at the higher temperatures were 1.5-2.0 weeks ; it has been
suggested that degradation of cyanazine at -10 deg C is not very likely . A half-life of 6 days
was observed in a cornfield study in Quebec, Canada .
AQUATIC FATE: The persistence and fate of cyanazine was studied in a model aquatic
ecosystem ; after 35 days, only 18% of the initial cyanazine remained undegraded ; the
following metabolites were identified : 60% N-deethylcyanazine, 0.8% cyanazine amide, 0.3%
N-deethylcyanazine, 1.2% unknown polar metabolites, and 19% unextractable metabolites ;
degradation of the triazine ring to CO2 proceeded slowly ; cyanazine and its metabolites did not
bioconcentrate in the food chain . The exact degradation mechanism in water has not been
determined with certainty, but may be a combination of microbial degradation and catalyzed
hydrolysis. At 25 deg C and pH range 5.5-9, the un-catalyzed aqueous hydrolysis half-life is
at least 200 days . Laboratory studies have suggested, however, that natural water constituents,
such as humic and fulvic acid, may catalyze the chemical hydrolysis . Volatilization from water
is not expected to be an important fate process; volatilization was not an important process
in the model ecosystem study .
ATMOSPHERIC FATE: Based upon an extrapolated vapor pressure of 1.38X10-7 mm Hg at
25 deg C , cyanazine can exist in both the vapor and particulate phases in the ambient
atmosphere(2,SRC). It will degrade rapidly in the vapor phase by reaction with photochemically
produced hydroxyl radicals with an estimated half-life of about 3 hr(3,SRC). Physical removal
from air by wet deposition (dissolution in clouds, rainfall, etc) and dry deposition (particulate
settling, etc) will also occur. Cyanazine has been detected in widespread rainwater
monitoring studies ; degradation rates while associated with rainwater and clouds are
unknown; these monitoring studies suggest that widespread atmospheric dispersal is
possible .
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| Drinking Water Impact | DRINKING WATER: Drinking water samples collected in Dresden, Ontario between
1982 and 1987 contained annual mean cyanazine levels ranging from <0.05 to 4.6 ug/l ; the
highest reported level was 10 ug/l . In July 1986, 33 treated public water sources were analyzed
for cyanazine following a rainstorm ; cyanazine was detected in 30 of 33 waters at levels of
0.12-20 ug/l .
SURFACE WATER: Between 1983 to 1991, the US Geological Survey collected and analyzed
more than 4000 water samples collected at 8 monitoring stations located on rivers and tributaries
of the Lake Erie basin ; maximum cyanazine concns detected at the stations ranged from 1.36
to 24.77 ug/l ; most samples were below detection limits (0.05 ug/l) ; avg concn of positive
detections ranged from 0.05 to 0.40 ug/l ; most detections occurred during agricultural use
seasons indicating field runoff . During a Jan 1981 to Dec 1985 water monitoring analysis of
the mouths of Grand, Saugeen and Thames Rivers (Ontario, Canada), cyanazine was detected at
concns of the 1 ug/l magnitude in 8 of 96 Grand River samples, 5 of 143 Saugeen River samples,
and 32 of 222 Thames River samples ; during a Jan 1986 to Dec 1990 water monitoring
analysis of the mouths of Grand, Saugeen and Thames Rivers (Ontario, Canada), cyanazine was
detected in 2 of 250 Grand River samples, 2 of 154 Saugeen River samples, and 3 of 70 Thames
River samples . Water samples collected from the Sydenham River (Dresden, Ontario) between
1982 and 1987 contained annual mean cyanazine levels ranging from 0.5 to 3.6 ug/l ; the
highest reported level was 10 ug/l .
SURFACE WATER: Monitoring of the Des Moines River (Iowa) and an associated reservoir
during Sep 1977 to Nov 1978 found the highest cyanazine concns (71-457 ng/l) during the
agriculturally active months of May through Aug ; it was noted that agricultural runoff from the
upstream watershed was a major source of river pollution ; levels during Sep to Dec were
2-151 ng/l and below detection limits during Jan to Apr . Cyanazine was positively detected in
15 water samples collected from various Swedish streams during 1985-1987 with max concns of
0.7 ug/l . Cyanazine was detected in 4 of 31 NJ surface water samples at concns of 0.025 to
0.07 ppb (sampling dates and locations not reported) . Monitoring conducted by the US
Geological survey at 17 sampling stations on the Mississippi River and its tributaries during May
to Jun 1988 detected cyanazine levels ranging from 17 to 647 ng/l . Water samples collected
from the Cedar River (IA) from May 1984 through Nov 1985 were found to contain cyanazine at
levels below 1 ug/l .
GROUNDWATER: In a 1969 to 1978 monitoring analysis of well water from 237 wells from
agricultural areas of Ontario, Canada, cyanazine was detected in only two wells at levels of 0.1-10
ug/l . Cyanazine was reportedly found at 1.1 ppb concn in one of 82 wells in a central PA study
where the water level was about 75 below land surface ; it was also detected at low levels
(0.1-1.0 ppb) in three wells in Iowa during springtime(2-3). According to the USEPA's
Groundwater Data Base, cyanazine has been detected in groundwaters from IA, IL, MD, MN, PA
and VT and concns ranging from 0.01 to 80 ppb .
RAIN/SNOW: Collection of 14 to 24 rainwater samples at each of four US sites (West
Lafayette, IN; Tiffin, OH; Parsons, WV; Potsdam, NY) in the spring and summer of 1985 resulted
in cyanazine detections ranging from 0.1 (detection limit) to 1.0 ug/l ; cyanazine was found in
nearly 35% of all samples collected .
EFFL: In a study of two watersheds in GA, seasonal losses of cyanazine via field runoff have
been reported to range from 0.07 to 1.0% of total field application .
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