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Ammonium Sulfamate

Publication Date: 9/93

TRADE OR OTHER NAMES

Amicide, Amidosulfate, Ammate, Amcide, Ammate X-NI, AMS, Fyran 206k, Ikurin, Sulfamate, AMS.

REGULATORY STATUS

Ammonium sulfamate is a general use herbicide. Check with specific state regulations for local restrictions which may apply.

Products containing ammonium sulfamate must bear the signal word "Caution." Discontinued by Du Pont in 1988 (29).

INTRODUCTION

Ammonium sulfamate (AMS) is an herbicide used to control many types of woody plants, trees, herbaceous perennials, and annual broadleaf weeds and grasses (27). AMS is a contact herbicide which means that it injures only those parts of the plant to which it is applied (29). It is used primarily to control undesired growth along rights-of-way and for general weed and poison ivy control around homes, commercial buildings and fruit orchards (10, 28). AMS is also used as a fertilizer.

Ammonium sulfamate is applied in water solution or oil-water emulsion as a leaf, or foliar spray for control of woody plants, or it is applied as crystals or concentrated solution to cuts in the bark or on freshly-cut stumps of undesirable trees to prevent resprouting (6).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Ammonium sulfamate is moderately toxic to human beings. The effects of acute exposure to AMS include irritation of the skin, eyes, and digestive tract, nausea, vomiting, diarrhea, slowed breathing, convulsions, hallucinations, coma, physical or mental exhaustion, and collapse (5, 9). Contact with ammonium sulfamate may cause burns to the skin and eyes (24, 30). The dust of ammonium sulfamate is irritating to the nose and throat and can cause coughing or difficult breathing if it is inhaled (23). Inhalation of 5,000 mg/m3 of air is immediately dangerous to life or health (18). Ingestion of ammonium sulfamate may cause gastrointestinal disturbances, such as nausea or diarrhea, in humans (18).

Repeated applications of a 4% solution to the front side of one arm of each of five human subjects for five days showed no skin irritation (15). It did not cause irritation when it was injected just under the skin (subcutaneously) in rats; when applied to rabbits eyes, it did not cause conjunctivitis (8).

Studies show that 1,600 mg/kg to 3,900 mg/kg of AMS are lethal to one-half of the rats that are experimentally fed the herbicide (3, 20). This amount of AMS is referred to as its oral lethal dose fifty, or LD50, and indicates that it takes 1,600 to 3,900 milligrams of AMS, for each kilogram of body weight of the rat, to kill 50 percent of the rats tested. (The lower the LD50 is for a chemical, the more toxic it is; the higher the LD50 the less toxic is the chemical).

CHRONIC TOXICITY

In a 105-day study with rats, continuous feeding of 500 mg/kg/day. AMS did not cause signs of poisoning. Some slow-down, or inhibition, of growth was seen at doses of 1,000 mg/kg/day (7, 28). There was no skin irritation, nor any signs of systemic toxicity, when 20% and 50% water- based (aqueous) solutions were applied to the shaved skin of rats (7).

Reproductive Effects

Reproduction was not impaired in a study during which rats were given dietary doses of 17.5 or 25 mg/kg/day of AMS for 15 months (26). The fertility of quail was not affected during two 10-day periods during which they were fed 150 mg/kg per day (4).

Teratogenic Effects

No data were found on this aspect of ammonium sulfamate.

Mutagenic Effects

There are limited data available on the status of AMS as a mutagen. AMS showed negative results on a test called the Ames/Salmonella assay, indicating that it may not have the ability to cause permanent changes (mutations) in genetic material (26).

Carcinogenic Effects

A three-generation rat reproduction study did not show harmful effects at a feeding level of 25 mg/kg/day, suggesting that AMS may not be carcinogenic at this level (26). Due to a lack of data, EPA has not classified the carcinogenicity status of AMS (31).

Organ Toxicity

Gastrointestinal tract problems may be caused if ammonium sulfamate is eaten (22).

Fate in Humans and Animals

Following oral administration of AMS to dogs for 5 days, 80 to 84% of the dose was excreted as sulfamic acid in the urine, indicating that AMS is readily absorbed into the bloodstream from the gastrointestinal tract (31).

ECOLOGICAL EFFECTS

Effects on Birds

AMS is highly toxic to birds. The oral LD50 in wild birds is 2,370 micrograms (ug)/kg (15). The oral LD50 in quail is 3000 mg/kg (15, 2, 23). The oral LD50 in ducks is 4,200 mg/kg (15). In a 14-day feeding study, 150 and 590 mg/kg AMS per day had no effect on quail. Quail fertility was not affected by two 10-day periods during which 150 mg/kg/day was mixed with their feed (27).

Effects on Aquatic Organisms

Ammonium sulfamate is not very toxic to fish. Testing for the toxicity of AMS to fish was carried out in water with a temperature of 10 to 16 degrees C and a pH of 7.2 to 7.6. The levels at which a 46% solution of AMS becomes toxic (threshold value for toxic activity) in perch is 300 milligrams per liter (mg/l). The threshold level for toxic activity of the same preparation to roach is 400 mg/l (10). Death occurred in one-half of a population of carp that was exposed to a 1,000 to 2,000 ppm solution of AMS over a 48-hour period (27). Half of the harlequin fish exposed died after a 24-hour exposure to a 1,250 ppm solution of AMS sprayed in the air (19).

Effects on Other Animals (Nontarget species)

When it is used according to the directions on the product label AMS is not hazardous to livestock (3). Deer were not harmed when they were fed AMS-treated leaves (11, 27). The herbicide is relatively nontoxic to bees, and can be used around them with minimum injury (14). A concentration of 30 ppm ammonium sulfamate had no effect on small aquatic invertebrates (23).

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

Ammonium sulfamate can persist in soil for one to three months, depending on soil type, climatic conditions, and the levels of minute organisms (microbes) in the soil (19). Under the humid conditions of the eastern U.S., the poisonous effect to plants (phytotoxicity) of AMS in the soil disappeared after six to eight weeks. This was measured by the growth of various grasses and crops. Residual activity of AMS may last longer in drier conditions. In regions with less moisture, traces of AMS and its breakdown products (metabolites) may remain on or in soil, water, or a crop for longer periods of time (27). It can be decomposed by soil microbes in a 6 to 8-week period (10). Soil may become temporarily nonproductive if AMS is used at high rates (3).

AMS does not readily bind, or adsorb, to soil particles. It dissolves readily in soil moisture, and moves, or leaches , through the soil with groundwater. Based on its potential to contaminate groundwater, AMS is one of the herbicides for which environmental fate data have been requested from manufacturers by EPA. It should not be used where leaching could contaminate aquifers or wells (12, 26, 27).

Breakdown of Chemical in Water

Ammonium sulfamate is hygroscopic, or readily moisture absorbent, as well as highly water soluble, meaning that it dissolves easily in water (3, 27). The use of this herbicide should be avoided near drinking water reservoirs, ponds, streams, or lakes. AMS spraying equipment should not be drained or flushed near water sources (26).

Breakdown of Chemical in Vegetation

Ammonium sulfamate causes leaf damage. It is absorbed rapidly through leaves, as well as through cut surfaces on wood and is translocated to other parts of the plant (10, 29). It should not be used on vegetation valued by the grower since it is nonselective, capable of killing more than the species of plants for which it is intended. AMS equipment should not be drained or flushed near desirable plants for the same reason (26). Ammonium sulfamate is a contact herbicide, and causes injury only to the parts of the plant to which it is applied. It is transferred from one part of the plant to another in a process called translocation (3).

PHYSICAL PROPERTIES AND GUIDELINES

Ammonium sulfamate is colorless, odorless, hygroscopic, water- soluble crystalline solid (3, 10). It is compatible with other water- soluble herbicides or wettable powders as long as their active ingredients are not sensitive to acids. It is incompatible with the herbicide bromacil (10). Ammonium sulfamate is readily oxidized by bromine and chlorine, and forms addition products with aldehydes (28). The technical grade product contains 70-90% of the active ingredient with 10-30% impurities, such as water, ammonium salt of iminodisulfonic acid, and ammonium sulfate (13).

Since ammonium sulfamate is hygroscopic, it can pull moisture out of the atmosphere and should only be stored in airtight containers which are kept closed and away from moisture (7). Whenever possible it should be kept in its original container, otherwise it should be kept in nonmetallic containers only. Ammonium sulfamate has fire retardant properties (27). Ammonium sulfamate is corrosive to metal. Spray equipment should be washed thoroughly after use to remove all AMS and decrease its potential to corrode (27, 28). AMS will not vaporize or become a gas (it is not volatile) (3). Toxic gases and vapors such as ammonia, hydrogen sulfide, oxides of nitrogen or sulfur, and carbon monoxide may be released when AMS decomposes at 160 degrees C or in a fire (15, 23, 30). In the presence of acids, AMS may undergo spontaneous hydrolysis with the liberation of much heat (30).

Prolonged skin contact with ammonium sulfamate should be avoided. Wash off with plenty of water in case of skin contact (3). Contact with eyes and inhalation of spray mists (e.g. drift) should also be avoided (10). To prevent these kinds of exposure it is recommended that the following be worn when using this chemical: goggles, impervious protective clothing, including gloves and self-contained breathing apparatus (18, 23).

Ammonium sulfamate has stronger herbicidal effects than all other salts of this acid. While it is used at dosages of 100-200 kg/ha to clear out weeds, at dosages of 400-600 kg/ha it can temporarily sterilize soil (13).

Occupational Exposure Limits:

5 mg/m3 OSHA TWA (respirable fraction)
10 mg/m3 OSHA TWA (total dust)
10 mg/m3 ACGIH TWA
5 mg/m3 NIOSH Recommended TWA (respirable fraction)
10 mg/m3 NIOSH Recommended TWA (total dust) (30)

Physical Properties:

CAS#: 7773-06-0
Specific gravity: >1 (30)
H2O solubility: 357% at 50 degrees C (18); 68.4% at 25 degrees C (30)
Solubility in other solvents: Slightly soluble in hydrophobic organic solvents (13) Insoluble in alcohol (2) Liquid ammonia; slightly soluble in ethanol; moderately soluble in glycerol, glycol, formamide (18)
Melting Point: 125-132 degrees C (2, 3)
Boiling point: 320 degrees F (160 degrees C) (30)
Decomposition temperature: 160 degrees C (27)
Vapor pressure: Negligible, approximately 0 torr at 20 degrees C (2)
Koc: From its behavior in field plots and its lack of response to soil type, it was concluded that AMS is not retained in soil, but moves with soil moisture (23).
Kd: Extremely mobile in 2 column studies (25)
pH: 4.9 at 0.2 M (30)
Chemical Class/Use: inorganic salt; herbicide

BASIC MANUFACTURER

Du Pont Agricultural Products
Walker's Mill, Barley Mill Plaza
PO Box 80038
Wilmington, DE 19880-0038

Review by Basic Manufacturer:

Comments solicited: October, 1992
Comments received: November, 1992

REFERENCES

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