|Chemical Abstract Number (CAS #)||
||EPA Method 505||EPA Method 525.2
||EPA Method 619
||EPA Method 8141
Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound.
|Use|| IT IS A PRE-EMERGENCE HERBICIDE RECOMMENDED FOR CONTROL OF
BROAD-LEAVED & GRASSY WEEDS DEEP-ROOTED CROPS SUCH AS ARTICHOKES,
ASPARAGUS, BERRY CROPS, BROAD BEANS, CITRUS, COFFEE, FORESTRY, HEVEA,
HOPS, OIL PALMS, OLIVES, ORCHARDS (POME & STONE FRUITS) ORNAMENTALS,
SISAL, SUGARCANE, TEA, TREE NURSERIES, TURF, VINEYARDS & NONCROP
AREA, MAJOR USE IS ON MAIZE; IN THE USA IT IS ALSO USED TO CONTROL
VEGETATION & ALGAE IN FARM PONDS, FISH HATCHERIES, ETC
/Simazine is used with AAtrex for weed control in corn; with paraquat for apples, peaches,
pecans, almonds, pears, cherries, corn, grapes, & oranges; with Roundup, or Oust for noncrop
land use: with Surflan on Christmas trees; with Dual on corn & ornamentals.
|Consumption Patterns|| HERBICIDE, OF WHICH APPROXIMATELY 49% IS USED ON CORN, 8% ON
CITRUS, 6% ON DECIDUOUS FRUITS, 5% ON FIELD CROPS, 3% ON VEGETABLES,
17% FOR INDUSTRIAL/COMMERCIAL USES, & 13% FOR AQUATIC USES (1975)
|Apparent Color|| Colorless powder; WHITE SOLID
|Melting Point|| 225 DEG C
|Molecular Weight|| 201.67
|Density|| 1.302 g/cu cm @ 20 deg C
|Sensitivity Data|| Simazine is a moderate eye and dermal irritant.
|Environmental Impact|| Simazine may be released to the environment via effluents at manufacturing sites and at
points of application where it is employed as a herbicide. If released to water, simazine is not
expected to bioconcentrate in aquatic organisms, adsorb to sediment and suspended particulate
matter, or to volatilize. Slow biodegradation of simazine may occur in water based upon the slow
biodegradation observed in soil. Simazine is fairly resistant to hydrolysis with reported half-lives
for hydrolysis in aqueous buffer solutions at 25 deg C at pH 5, 7, and 9 of 70, >200, and >200
days, respectively. The product of simazine hydrolysis is
2-hydroxy-4,6-bis(ethylamino)-1,3,5-triazine. If released to soil, the mobility of simazine will be
expected to vary from slight to high in soil-types ranging from clay soils to sandy loams soils,
respectively, based upon soil column, soil thin-layer chromatography, and Koc experiments.
Therefore may leach to groundwater; adsorption of simazine in soil has been observed to increase
as titratable acidity, organic matter and, to a lesser extent, clay content of the soil increased.
Simazine may be susceptible to slow hydrolysis in soil based upon reported half-lives for
degradation (purportedly mainly soil catalyzed hydrolysis) of simazine in two soil 45 and 100
days. Simazine can be utilized by certain soil microorganisms as a source of energy and
mineralization. 10.4% of 14C-labeled simazine to CO2 has been observed in 110 days in a
clay-lime soil. No degradation of simazine was detected in a soil suspension test without the
addition of glucose as an energy source suggesting that degradation of simazine in these soil
experiments was due to cometabolism. 2-Chloro-4-amino-6-ethylamino-1,3,5-triazine and
2,4-dihydroxy-6-amino-1,3,5-triazine have been identified as microbial transformation products of
simazine in soil. Reported persistence of simazine in soil varies from a half-life of <1 month to no
degradation being observed in 3.5 months. Simazine is not expected to volatilize from near
surface soils or surfaces under normal environmental conditions. If released to the atmosphere,
simazine is expected to exist almost entirely in the particulate phase. Vapor phase reactions with
photochemically produced hydroxyl radicals in the atmosphere may be important (estimated
half-life of about 2.8 hr). Photolysis may be an important removal mechanism in the atmosphere.
The most probable exposure should be occupational exposure which may occur through dermal
contact or inhalation at places where simazine is produced or used as a herbicide.
|Environmental Fate|| AQUATIC FATE: PERSISTENCE OF SIMAZINE IN PONDS IS DEPENDENT
UPON MANY FACTORS INCLUDING LEVELS OF ALGAE & WEED INFESTATION.
AVERAGE HALF LIFE FOR SIMAZINE IN PONDS IS 30 DAYS.
TERRESTRIAL FATE: In sandy loam soil, simazine half-life varied from 37 days at 25 deg C &
13% soil moisture to 234 days at 15 deg C & 7% soil moisture.
TERRESTRIAL FATE: DEGRADATION OF SIMAZINE WAS STUDIED IN 3 SOILS IN
TAIWAN (LOAM, SANDY LOAM, & CLAY LOAM) IN LAB & FIELD EXPT. HALF-LIFE
WAS 17.9 TO 52.5 DAYS, DEPENDING ON SOIL TYPE & TEMP (20-40 DEG C).
MOBILITY WAS LIMITED TO UPPER 10 CM LAYER. DEGRADATION CAN BE
PREDICTED BY THE EQUATION H= AM-B (H= HALF LIFE, M= MOISTURE, B=
CONSTANT), COMBINED WITH THE ARRHENIUS EQUATION & THE 1ST ORDER
AQUATIC FATE: Simazine residues may persist up to 3 years in soil under aquatic field
conditions. Dissipation of simazine in pond and lake water was variable, with half-lives ranging
from 50 to 700 days. The degradation compound G-28279 1,3,5-triazine-2,4-diamine,
6-chloro-N-ethyl-; CAS Number 1007-28-9 was identified in lake water samples, but was no
more persistent than that parent compound.
TERRESTRIAL FATE: If released to soil, the mobility of simazine will be expected to vary
from slight to high in soil-types ranging from clay soils to sandy loam soils, respectively, based
upon soil column, soil thin-layer chromatography, and Koc experiments(6). Therefore, it may
leach through certain types of soils to groundwater. Adsorption of simazine in soil has been
observed to increase as titratable acidity, organic matter and, to a lesser extent, clay content of the
soil increased(4,5). Simazine has been observed to leach to >60 cm under field conditions in loam
and silty clay loam soils . However, in another set of field experiments with a sandy loam soil
and a clay soil, very little simazine movement was observed with nearly all of it remaining in the
top 3 cm of the soil . Simazine will be subject to slow to moderate degradation in soil which
may be due to both chemical hydrolysis and biodegradation. The half-lives for degradation
(purportedly mainly soil-catalyzed hydrolysis) of simazine in Hatzenbuhl soil at pH 4.8 and
Neuhofen soil at pH 6.5 are 45 and 100 days, respectively . Simazine is not expected to
volatilize from near surface soils or surfaces.
TERRESTRIAL FATE: It has been reported that simazine and other s-triazines can be utilized
by certain soil microorganisms as a source of energy . Mineralization of 10.4% of 14C-labeled
simazine in 110 days has been reported in a clay-lime soil . No degradation of simazine was
detected in a soil suspension test without the addition of glucose as an energy source suggesting
that degradation of simazine in these soil experiments was due to cometabolism . The products
of microbial degradation of simazine in soil include 2-chloro-4-amino-6-ethylamino-1,3,5-triazine
and 2,4-dihydroxy-6-amino-1,3,5-triazine . Reported persistence of simazine in soil varies from
a half-life of <1 month to no degradation being observed in 3.5 months . The amount of
organic matter in the soil, for example tillage, may have a significant effect on the persistence of
simazine . Additions of 1%, 5%, and 10% leaf compost to soil gave simazine half-lives of about
140, 60, and 40 days, respectively .
AQUATIC FATE: If released to water, simazine will not be expected to bioconcentrate in
aquatic organisms, adsorb to sediment and suspended particulate matter, or to volatilize. The
s-triazine ring of simazine is fairly resistant to microbial attack. Although no information
concerning biodegradation in natural waters was located, slow biodegradation of simazine may
occur in water based upon the slow biodegradation observed in soil. Chemical hydrolysis of
simazine may be more important environmentally than biodegradation at low pH or when various
catalysts are present. Simazine has reported half-lives for hydrolysis in aqueous buffer solutions at
25 deg C at pH 5, 7, and 9 of 70, >200, and >200 days, respectively . The product of simazine
hydrolysis is 2-hydroxy-4,6-bis(ethylamino)-1,3,5-triazine . The rate of hydrolysis may be
increased by various catalysts based upon the observed increase in rate of hydrolysis rates for the
chemically similar herbicide atrazine in water solutions upon addition of sterilized soil and
humic and fulvic acids .
AQUATIC FATE: Photolysis may be an important removal mechanism based upon results for
photolysis of water solutions of simazine irradiated at wavelength of 290nm . However, in other
experiments, photolysis of simazine did not occur in methanol, ethanol, butanol and water at
wavelengths > 300 nm . The photolysis of simazine has been reported to be enhanced by the
presence of the photosensitizer riboflavin . The overall half-life range for simazine in 4 Missouri
ponds was 46-174 days .
ATMOSPHERIC FATE: If released to the atmosphere, simazine is expected to exist almost
entirely in the particulate phase based upon a reported vapor pressure of 6.1X10-9 mm Hg at
20 deg C . The rate constant for the vapor-phase reaction of simazine with photochemically
produced hydroxyl radicals has been estimated to be 137.2 cu cm/molecule-sec at 25 deg C which
corresponds to an atmospheric half-life of about 2.8 hr at an atmospheric concn of 5X10 5
hydroxyl radicals per cu cm . Photolysis may be an important removal mechanism in the
TERRESTRIAL FATE: THE LONG SOIL PERSISTENCE OF THESE CMPD DOES
CREATE THE PROBLEM OF SOIL CARRY OVER, WHICH CAN DAMAGE
SUCCEEDING CASH CROPS. THEREFORE EXTREME CAUTION MUST BE TAKEN IN
THEIR APPLICATION ON CROPLAND TO AVOID SUCH INJURY TO FOLLOWING
|Drinking Water Impact|| DRINKING WATER: EPA MONITORING SYSTEMS HAVE IDENTIFIED 699
BIOREFRACTORIES IN US WATER SUPPLIES. FROM AN ORIGINAL LIST OF 309
BIOREFRACTORIES IN 1977, THE NCI HAS IDENTIFIED & CLASSIFIED 23 ONE OF
WHICH WAS SIMAZINE.
The levels of simazine in water collected from 11 agricultural watersheds merging into Lake
Huron, Lake St. Clair, Lake Erie and Lake Ontario between 1975 and 1977 were reported .
Simazine was detected (detection limit of <0.04 ug/l) in 9% of the water at a mean concentration
of 0.05 ug/l, and a concentration range of none detected to 3.4 ug/l.
39 streams flowing into Lake Ontario in 1977 for simazine level were monitored, 28% of the
stream waters had detected levels of simazine (detection limit 0.03 ug/l). The mean concentration
of simazine in all the water samples was 0.3 ug/l.
DRINKING WATER: Simazine has been identified at trace levels (<0.1 ppb) in 3 New Orleans
LA drinking water supplies sampled in 1974 .
GROUNDWATER: Simazine has been found in groundwater from new wells in the Northern
Italy province of Bergamo at a concn range of 0 to 200 parts/trillion . Simazine was detected in
5 of 237 wells in Ontario, Canada during 1969-1978 with the concn of 3 samples ranging between
0.1 to 1.0 ug/l, and 1 sample between 1.1-10 ug/l and one greater than 10,000 ug/l . Simazine
was detected in 4 of 112 wells suspected of contamination due to runoff and spray drift between
1979 and 1984 in rural Ontario, Canada, and the concn in 3 of the shallow wells were 0.1, 2.8,
and 6.0 ug/l, respectively .
SURFACE WATER: Simazine was detected in the following numbers of samples out of 708
total samples from Central European streams in spring 1976 to fall 1977 within the indicated
concn ranges: 7 samples 1.1-10 ppb; 25 samples 0.4-1.0 ppb; 86 samples <0.4 ppb . Simazine
was found in Swedish stream waters (1985-1987) in 3 of 153 samples taken during July-Sept at a
max concn of 1.1 ppb and not detected in 106 samples taken during April-May and in Oct .
Simazine was detected, not quantified, in 37% of creek water samples from the Hillman Creek
watershed in southwestern Ontario, Canada . The residues were consistently higher at upstream
sites than at the mouth . Simazine was found in 9.3% of samples of waters collected from 11
agricultural watersheds in Ontario, Canada during 1975-1976 at a max concn of 3.4 ng/l . The
avg concn ranged from not detected to 0.04 ng/l and from not detected to 0.37 ng/l during May
1975-April 1976 and May 1976-April 1977, respectively, and the overall averages were 0.02 and
0.06 ng/l, respectively .
SURFACE WATER: Simazine was found in samples of water from the mouths of the following
rivers in Ontario, Canada from 1981-1985: Thames River, 8 of 201 samples positive, avg concn
0.6 ug/l; Saugeen River, 1 of 143 samples positive, avg concn 0.1 ug/l; Grand River, not detected
in 85 samples . Simazine was detected in water from the mouths of the above rivers at the
following concn: Grand River, 1975-1976, 20 samples, not detected to 10 ng/l, 5.8 ng/l avg,