|Chemical Abstract Number (CAS #)||
||EPA Method 619|
Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound.
|Use|| A selective herbicide used pre- & post-emergence to control broad leaved & grass weeds
in bananas, citrus, cocoa, coffee, maize, oil palms, pineapples, sugarcane, tea, in potatoes (as vine
desiccant) & in noncrop area.
|Consumption Patterns|| HERBICIDE, OF WHICH APPROXIMATELY 85% IS USED ON FIELD CROPS
AND 15% ON CORN (1975)
|Apparent Color|| COLORLESS POWDER; WHITE, CRYSTALLINE; Colorless, crystals. From
|Melting Point|| 88-89 DEG C
|Molecular Weight|| 227.35
|Density|| 1.190 g/cu cm @ 20 deg C
|Sensitivity Data|| Slight irritant to skin of rabbits
|Environmental Impact|| Ametryne may be released to the environment during its manufacture, transport, storage,
formulation and use as a selective herbicide for the control of annual broadleaf and grass weeds. It
is applied as an aqueous suspension for preemergence, postemergence, or post-directed
applications on crops such as pineapple, sugarcane, bananas, plantain, grapefruit and oranges.
Ametryne is a weak base with a pKa of 3.12, indicating that it is almost entirely undissociated at
environmental pHs. When ametryne is applied to soil, it will adsorb moderately to the soil
(average Koc = 388). It is fairly persistent in soil; its half-life in soil is reported to be 6.0 months
at 15 deg C and 4.5 months at 30 deg C). Degradation is more rapid in acidic soils than in neutral
ones. An important mechanism by which ametryne may be lost from soil is by volatilization.
Chemicals with low Henry's Law constants may rise to the soil surface with evaporating water
and as its concentration increases at the soil-air interface, so will the amount of chemical
volatilizing. If released into water, ametryne will partially adsorb to sediment and particulate
matter in the water column. It should undergo photolysis in surface layers of water (half-life ca.
10.2 hr); the rate of photodegradation will be higher at low pHs and in the presence of some
sensitizers. No biodegradation rates in water are available for natural water; biodegradation would
be expected to be slow. Volatilization and bioconcentration in fish should not be significant.
Ametryne would generally be released to the atmosphere as an aerosol while spraying and will be
removed by gravitational settling. In the atmosphere, vapor-phase ametryne would degrade by
reaction with photochemically produced hydroxyl radicals; its estimated half-life is 2.5 hr.
Exposure to ametryne will be primarily occupational by skin contact. It is most likely to occur
while applying the herbicide or contact with treated soil or vegetation. Exposure by inhalation
may occur when entering recently treated fields.
|Environmental Fate|| TERRESTRIAL FATE: Research results from most of the continental USA indicate that
the persistence of ametryn in soils compares quite closely to prometryn.
TERRESTRIAL FATE: Neither ametryn nor its hydroxy metabolite leach past 6 inch depth with
normal rainfall. However, since both compounds are persistent they may leach under exaggerated
rainfall or flood and furrow irrigation. This behavior is seen with other triazines.
TERRESTRIAL FATE: If released into soil, ametryne will adsorb moderately to soil; the
average Koc reported for 32 soils being 388.4(8). It will slowly leach into the soil, especially after
heavy applications . Ametryne is moderately persistent in soil; its half-life in soil has been
reported to be 6.0 and 4.5 months at 15 and 30 deg C, respectively(1,2). Degradation generally
appears to be microbial rather than chemical in nature(6) and is more rapid in acidic soils than
neutral ones . Oat seedlings were viable in soil 116 days after treatment with ametryne at 2
lb/acre, but not at 4 lb/acre . Seedlings did not survive when planted 42 days posttreatment.
Five months after 2.9 kg/ha of ametryne was applied to a sugar cane field in Oahu, Hawaii, no
ametryne residue was detected in the soil . In a greenhouse experiment using a ryegrass
bioassay it took 4.5-20 and 20-60 weeks for 50% and 80% of ametryne activity to disappear from
soil treated with 1.0 lb of ametryne per acre(7). At an application rate of 4.0 lb/acre >60 weeks
were required for half of its phytotoxicity to disappear.
AQUATIC FATE: If released into water, ametryne would adsorb moderately to sediment and
particulate matter in the water column. Ametryne should undergo photolysis in surface layers of
water (half-life 10.2 hr at pH 6.8 ). The rate of photodegradation increases with decreasing pH
and is more rapid in the presence of some sensitizers. While ametryne may biodegrade in natural
waters, or undergo catalyzed hydrolysis, no rates of reactions are available .
ATMOSPHERIC FATE: Ametryne will generally enter the atmosphere as an aerosol during
spraying operations and will be removed from the air by gravitational settling. In the atmosphere,
vapor-phase ametryne would be expected to degrade by reaction with photochemically produced
hydroxyl radical. Its estimated half-life is 2.5 hr(1,SRC).
TERRESTRIAL FATE: In the field, Ametryn degraded with a half life of 125 to 250 days.
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|| Ametryn has been found in 2 of 1, 190 surface water samples analyzed and in 24 of 560
ground water samples. Samples were collected at 215 surface water locations and 513 ground
water locations, and ametryn was found in 6 states. The 85th percentile of all nonzero samples
was 0.1 ug/l in surface water and 210 ug/l in ground wate sources. The maximum concentration
found was 0.1 ug/l in surface water and 450 ug/l in ground water.