---

The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

---

E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

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

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Prometryn

Trade and Other Names: Trade names include Caparol, Gesagard, Mercasin, Promet, Prometrex, and Primatol Q.

Regulatory Status: Prometryn is a slightly to moderately toxic compound which is classified as a member of toxicity class II or III, depending on the formulation. It is classified as a General Use Pesticide (GUP). Labels for products containing prometryn must bear the Signal Words CAUTION or WARNING, depending on the formulation.

Chemical Class: triazine

Introduction: Prometryn is a selective herbicide which controls annual grasses and broadleaf weeds in a variety of crops including cotton and celery. It inhibits photosynthesis in susceptible species. Prometryn is available in wettable powder and liquid formulations.

Formulation: Prometryn is available in wettable powder and liquid formulations.

Toxicological Effects:

• Acute toxicity: Prometryn is slightly to practically non-toxic by ingestion, with reported oral LD50 values of 3750 to 5235 mg/kg in rats, 3750 mg/kg in mice, and greater than 2020 mg/kg in rabbits [6,15]. Via the dermal route, it is slightly toxic with reported dermal LD50 values of greater than 2000 mg/kg to greater than 3100 mg/kg in rabbits [6,15]. Technical prometryn does not cause skin irritation in rabbits or skin sensitization in guinea pigs, and may cause slight eye irritation in rabbits [15]. Some formulations (e.g., Caparol), may be mild eye irritants and/or slight skin irritants in rabbits [6,15]. The 4-hour LC50 for prometryn in rats is 5.2 mg/L [15]. Symptoms of high acute exposure may include sedation, muscle incoordination, breathing difficulty, bulging eyes, constricted pupils, diarrhea, excessive urination, and convulsions.
• Chronic toxicity: The results of long-term feeding studies do not indicate obvious, nor severe, toxicity from prometryn exposure. Rats fed dietary doses of 37.5 mg/kg/day and dogs given 4 mg/kg/day over a 2-year period didn't show observable gross or microscopic signs of systemic toxicity [15]. Effects which occurred at higher dose rates in these animals included changes in relative weights of the kidney and liver [15].
• Reproductive effects: In a three-generation study, no reproductive effects were seen in rats fed up to 5 mg/kg/day [37]. In another study, reduced offspring body weights, but no other reproductive effects, were seen in rats at doses of up to 75 mg/kg/day [15]. From the data, it appears that prometryn is unlikely to cause reproductive effects.
• Teratogenic effects: No teratogenic effects were seen in the offspring of rats fed 250 mg/kg/day, the highest dose tested [37]. In another study, no teratogenic effects were seen in rats at doses of 50 mg/kg/day [15]. No teratogenic or developmental effects were seen in rabbits at doses of 72 mg/kg/day [15]. Prometryn does not appear to cause birth defects.
• Mutagenic effects: Eleven different tests for mutagenicity involving hamsters, bacteria, or mammalian cell cultures have all produced negative results, indicating that prometryn is not a mutagen [38].
• Carcinogenic effects: Prometryn was not carcinogenic in a 2-year rat feeding study at doses of up to 62.5 mg/kg/day [37]. Carcinogenic effects were not seen in mice at doses of up to 300 mg/kg/day over 18 months. The available data suggest that prometryn is not carcinogenic.
• Organ toxicity: Target organs identified through animal studies include the liver, kidneys, and bone marrow.

• Fate in humans and animals: The triazines are generally well-absorbed by the mammalian gut, and probably across the skin [16]. While the breakdown of prometryn is not adequately understood, available data indicate that, in rats, most of the herbicide is excreted in urine and feces within 48 hours of administration [39]. No detectable residues of prometryn or its metabolites were found in the muscle, fat, blood, liver, kidney, and other organs of sheep and cattle fed up to 100 ppm for 4 weeks. However, prometryn or its breakdown products were found in whole milk samples taken from cows that were fed up to 100 ppm in their diet for 21 days [39].

Ecological Effects:

• Effects on birds: Prometryn is practically nontoxic to birds; the acute oral LD50 values in bobwhite quail and mallard ducks are greater than 2150 mg/kg and greater than 4640 mg/kg, respectively. The reported 5- to 7-day dietary LC50 values are greater than 10,000 ppm for these same species [15].
• Effects on aquatic organisms: Prometryn is moderately toxic to fish, with reported 96-hour LC50 values of 2.5 to 2.9 mg/L in rainbow trout, 10.0 mg/L in bluegill sunfish, 3.5 mg/L in goldfish, and 8 mg/L in carp [15,40,41]. It is highly toxic to guppies [39]. It is slightly toxic to freshwater invertebrates [41]. A 19% decrease in shell growth was observed in oysters exposed to 1.0 mg/L of the herbicide for 48 hours. Pink shrimp were unaffected by exposure to 1.0 mg/L of the herbicide for 48-hours [40]. However, the compound has a 48-hour LC50 in the invertebrate Daphnia of 18.9 mg/L [15,41]. The observed concentration of prometryn in bluegill and in rainbow trout is 9 to 10 times the ambient water concentration, indicating a low potential for bioaccumulation [41].
• Effects on other organisms: Prometryn is nontoxic to bees and earthworms, with a reported contact LD50 of greater than 99 ug/bee, and a 48-hour LC50 of 153 mg/kg in earthworms [6,15].

Environmental Fate:

• Breakdown in soil and groundwater: Prometryn is moderately persistent in the soil, with a field half-life of 1 to 3 months [20]. It will persist longer under dry or cold conditions, which are not conducive to chemical or biological activity [15,38]. Following multiple annual applications of the herbicide, prometryn activity can persist for 12 to 18 months after the last application [38]. Soil microorganisms readily break down prometryn in the soil [15. The amount of the herbicide evaporating from soil increases with temperature and soil moisture content, but volatilization is not significant under most field conditions [15,38]. Prometryn is weakly bound to most soils, and is slightly soluble in water [20]. It may thus be mobile in some soils. However, it adsorbs more strongly to soils with higher proportions of clay and organic matter [38]. Field leaching studies indicate that prometryn stays in the top 12 inches of treated soil [38].
• Breakdown in water: No significant hydrolysis, or breakdown in water, was found when prometryn was tested over a period of 28 days in water ranging from slightly acidic to slightly alkaline and over a variety of test temperatures [38]. These data indicate that prometryn is potentially persistent in the water environment.
• Breakdown in vegetation: Prometryn is rapidly absorbed through both the foliage and roots of plants, and is translocated to the growing shoots [15]. Removal or degradation by the plant is rapid in non-susceptible plants, but very slow in susceptible species [15].

Physical Properties:

• Appearance: Prometryn is a colorless, crystalline solid [6].
• Chemical Name: N2,N4-di-isopropyl-6-methylthio-1,3,5-triazine-2,4-diyldiamine [6]
• CAS Number: 7287-19-6
• Molecular Weight: 241.37
• Water Solubility: 48 mg/L @ 20 C [6]
• Solubility in Other Solvents: s. in organic solvents, including ethanol, methanol, acetone, dicloromethane, and toluene [6]
• Melting Point: 118-120 C [6]
• Vapor Pressure: 0.13 mPa @ 20 C [6]
• Partition Coefficient: 3.3404 [6]
• Adsorption Coefficient: 400 [20]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.004 mg/kg/day [26]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Ciba-Geigy Corporation
P.O. Box 18300
Greensboro, NC 27419-8300

• Phone: 800-334-9481
• Emergency: 800-888-8372
  

References:

References for the information in this PIP can be found in Reference List Number 8

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.