E X T O X N E T

Extension Toxicology Network A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

P esticide

I nformation

P rofile Glyphosate



Publication Date: 5/94

TRADE OR OTHER NAMES

INTRODUCTION

Glyphosate is usually formulated as an isopropylamine salt. While it can be described as an organophosphorus compound, glyphosate is not an organophosphate ester but a phosphanoglycine, and it does not inhibit cholinesterase activity.

Glyphosate is a general use pesticide.

TOXICOLOGICAL EFFECTS

Acute Toxicity

In a number of human volunteers, patch tests produced no visible skin changes or sensitization.

Chronic Toxicity

Hens fed massive amounts over three days and again 21 days later showed no nerve related effects.

Reproductive Effects

Teratogenic Effects

Rats given doses up to 3,500 mg/kg on days 6 to 19 of pregnancy had offspring with no teratogenic effects, but other toxic effects were observed in both the mothers and the fetuses. No toxic effects to the fetuses occurred at 1,000 mg/kg/day.

Mutagenic Effects

Carcinogenic Effects

Organ Toxicity

Fate in Humans and Animals

Cows, chickens, and pigs fed small amounts had undetectable levels (less than 0.05 ppm) in muscle tissue and fat. Levels in milk and eggs were also undetectable (less than 0.025 ppm). Nearly all glyphosate residues were rapidly eliminated by fish that had been exposed for 10 to 14 days once these fish were transferred to glyphosate-free water. Glyphosate has no significant potential to accumulate in animal tissue (9).

ECOLOGICAL EFFECTS

Glyphosate is practically non-toxic to fish. However, Roundup was more toxic to fish than was glyphosate. In rainbow trout, for instance, the 96-hour LC50 was 8.3 mg/l with Roundup and 38 ppm with glyphosate. The LC50 for glyphosate was 120 mg/l for bluegill sunfish. An additive used in the Roundup formulation (modified tallow amine used as a surfactant) is apparently more toxic to fish than many common surfactants. For this reason, the formulation for use in aquatic situations (Rodeo) omits this ingredient. The surfactant is used to allow the compound to readily dissolve in solution and to keep the compound from balling up on the leaf surface.

There is a very low potential for the compound to build up in the tissues of aquatic invertebrates or other aquatic organisms. Glyphosate is relatively non-toxic to honeybees. Its oral and dermal LD50 is greater than 0.1 mg/ bee (7).

ENVIRONMENTAL FATE

In water, glyphosate is strongly adsorbed to suspended organic and mineral matter and is broken down primarily by microorganisms also. Its half-life in pond water ranges from 12 days to 10 weeks.

Glyphosate may be extensively metabolized by some plants while remaining intact in others (2). Once in the plant tissue, the chemical is translocated throughout the plant, including to the roots.

Exposure Guidelines:

NOEL (rabbit): 175 mg/kg/day HA: 0.7 mg/l (lifetime) ADI: 0.03 mg/kg (EPA)

0.3 mg/kg (WHO) LEL: 300 mg/kg/day (rabbit)

Physical Properties:

CAS #: 1071-83-6 Chemical name: N-(phosphonomethyl) glycine Chemical class/use: Phosphanoglycine herbicide Solubility in water: 900,000 mg/l Solubility in other solvents: insoluble in common organics Melting Point: 200 degrees C Vapor Pressure: negligible (Monsanto) Dissociation values: 2.27 (pKa) Partition Coefficient: 0.17 x 10 to the minus 2 power at 20 ppm; 0.6 x 10 to the minus 3 power at 100 ppm

BASIC MANUFACTURER

Review by Basic Manufacturer:

REFERENCES

National Library of Medicine (1992). Hazardous Substances Databank. TOXNET, Medlars Management Section, Bethesda, MD. Grossbard, E. and D. Atkinson, Editors (1985). The Herbicide Glyphosate, Butterworths, Boston, MA. U.S. Environmental Protection Agency (1987). Health Advisory, Office of Drinking Water. Forest Service (1984). Pesticide Background Statements, Vol. I Herbicides. United States Dept. of Agriculture, Agriculture Handbook No. 633. Monsanto Company (1985). Toxicology of Glyphosate and Roundup Herbicide, Department of Medicine and Environmental Health, St. Louis, MO. Stevens, James T. and Darrell D. Sumner. 1991. Herbicides in Handbook of Pesticide Toxicology Volume 3, Cases of Pesticides. Wayland J. Hayes and Edward R. Law editors. Academic Press, NY. The Agrochemicals handbook. 1991. The Royal Society of Chemistry, Cambridge, England. U.S. Environmental Protection Agency (1992). Pesticide Tolerance for Glyphosate. Federal Register 57 (49): 8739-40. Malik, J., G. Barry and G. Kishore. 1989. Minireview: The herbicide glyphosate. BioFactors 2 (1): 17-25.