PMEP Home Page --> Pesticide Active Ingredient Information --> EXTOXNET: The Extension Toxicology Network --> Metiram to Propoxur --> Molinate

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.

  Pesticide
Information
Profile
Molinate

Publication Date: 9/93

TRADE OR OTHER NAMES

Some trade names include Molinate, Hydram, Ordram and Yalan.

REGULATORY STATUS

Molinate is a registered as a general use pesticide by the EPA. Products containing molinate must bear the signal word "Warning" or "Caution" (4).

INTRODUCTION

Molinate is a selective herbicide which belongs to the thiocarbamate chemical class. It is used to control weeds in rice paddies (1, 4, 6, 8). It is toxic to germinating broad-leafed and grassy weeds. Molinate is available in granular and emulsifiable liquid formulations (4).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Molinate is moderately toxic by ingestion and slightly toxic by dermal absorption . It may cause skin irritation or sensitization (9, 10). Symptoms of exposure to molinate include nausea, diarrhea, abdominal pain, fever, weakness and conjunctivitis (3, 9).

Molinate is volatile and may be irritating when inhaled (11). Inhalation exposure to large amounts of thiocarbamates may cause itching, scratchy throat, sneezing and coughing (9). In male rats, the lowest dosage that will produce a toxic effect when inhaled (TDlo) is 0.6 to 0.64 mg/m3 over 6 hours of exposure (NIOSH RTECS Online File # 85/8406).

The amount of a chemical that is lethal to one-half (50%) of experimental animals fed the material is referred to as its acute oral lethal dose fifty, or LD50. The oral LD50 for molinate is 369-955 mg/kg in rats, and 530 mg/kg in mice (3, 9). For granular formulations (10G) the oral LD50 in rats is greater than 5,000 mg/kg (4). The dermal LD50 for the rabbit is 3536 to greater than 10,000 mg/kg (3, 4). The inhalation LCLO for molinate in both rats and cats is 200 mg/m3 (9). An LCLO is the lowest dose to produce deaths in test animals.

CHRONIC TOXICITY

Prolonged or repeated exposure to molinate may cause symptoms similar to the pesticide's acute effects. Chronic dermal exposure may cause sensitization dermatitis or conjunctivitis.

Reproductive Effects

Administration of molinate to young male rats at a rate of 3.2 mg/kg/ day for 2 months caused changes in spermatozoa but did not decrease sperm fertility. When these rats were mated to normal females, many of the embryos were resorbed and postnatal mortality was increased (3).

Teratogenic Effects

Molinate is suspected of being a human teratogen (10).

Mutagenic Effects

No information found.

Carcinogenic Effects

No information found.

Organ Toxicity

Molinate causes conjunctivitis (swelling of the tender inner layer of the eyelid) (10). Chronic exposure of test animals inhibited thyroid functions and decreased energy metabolism (9).

Fate in Humans and Animals

Molinate is only fairly well absorbed through oral, dermal and inhalation exposure. It is metabolized in the liver. No accumulation occurs. Excretion is primarily through the urine with a small amount lost in the feces. Excretion of radio-labeled molinate by rats was 95-96% complete in 48 hours. Approximately 88% of the eliminated molinate was in the urine and 11% in the feces. Less than 1% was expired to the air (3).

ECOLOGICAL EFFECTS

Harmful Effects on Birds

Molinate appears to be fairly low in toxicity to birds such as mallards.

Harmful Effects on Fish

The toxicity of molinate varies in fish. The lethal concentration fifty, or LC50, is that concentration of a chemical in air or water that kills half of the experimental animals exposed to it for a set time period. The 96-hour LC50 is 1.3 mg/l for rainbow trout and 30 mg/l for goldfish (4, 8). Cold water fish species seem to be more susceptible to molinate poisoning than others (Spence. Guide to Chem. in Crop Protection 1982). In some species, like carp, molinate produces anemia.

Effects on Other Animals (Nontarget species)

The symptoms of poisoning in wildlife species are similar to those in humans, and may include excessive salivation and tearing of the eyes, difficulty walking, weakness, tremors, and labored breathing (Rumack. Poisondex. 1975).

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Water

Because molinate is highly soluble in water and because it has a soil half-life of moderate duration (12 days), it is expected to have a large potential to contaminate groundwater. Molinate binds strongly to soil particles (7).

Soil microorganisms are responsible for most of the breakdown of molinate. It is relatively stable to breakdown by hydrolysis (3). When applied at recommended rates, it does not persist in soil. Molinate has a soil half-life of 3 weeks (4, 8).

Molinate rapidly volatilizes if the soil is wet. To prevent loss of the herbicide to evaporation, molinate should be plowed into the soil. Molinate may be broken down by sunlight once in the air (J. Environ. Sci. Health B. 15 (6):755-793. 1980).

Breakdown of Chemical in Water

Some hydrolysis occurs in the breakdown of molinate (8).

Breakdown of Chemical in Vegetation

Molinate is rapidly taken up by plant roots and transported to the leaves. In the leaves, molinate inhibits leaf growth and development (2, 8). It is rapidly metabolized in non-susceptible plants. Resistant plants produce carbon dioxide and other naturally occurring plant products such as amino acids, organic acids, etc. (7).

PHYSICAL PROPERTIES AND GUIDELINES

Molinate is a non-corrosive, clear liquid with an aromatic or spicey odor (3, 9). It is stable under normal temperatures and pressures, but thermal decomposition may release toxic oxides of nitrogen and sulfur (9).

Like the organophosphates and other carbamates, molinate has several important drug interactions. Poisoning victims should not be given any of the following drugs: morphine, aminophylline or theophylline, major tranquilizers (phenothiazines) or reserpine, high ceiling diuretics like furosemide (lasix) or ethacrynic acid (12).

Occupational Exposure Limits:

No occupational exposure limits have been established for molinate by OSHA, ACGIH or NIOSH (9).

Physical Properties:

CAS #: 2212-67-1
Solubility in Water: 800 mg/L at 21 degrees C (3, 5) or 0.088% (9).
Solubility in other solvents: Molinate is soluble in acetone, benzene, 2-propanol, methanol, xylene, ethanol, kerosene, and 4-methylpentan-2-one (9).
Boiling point: 202 degrees C at 10 mm Hg (3, 5).
Flash point: 139 degrees C (2).
Specific gravity: 1.0626-1.0669 at 20 degrees/20 degrees C (4)
Vapor pressure: 0.0056 mm Hg at 25 degrees C (3, 13).
Density: 1.5156 at 30 degrees C (Spencer. guide to chem. in crop protection. 1982).
Koc: 50 g/ml (7).

BASIC MANUFACTURER

Zeneca Ag Products
Wilmington, DE 19897
Telephone: 800-759-4500

Review by Basic Manufacturer:

Comments solicited: November, 1992
Comments received:

REFERENCES

  1. Meister, R.T. (ed.) 1987. Farm Chemicals Handbook. Willoughby, OH: Meister Publishing Co.
  2. WSSA Herbicide Handbook Committee. 1983. Herbicide Handbook of the Weed Science Society of America. 5th Ed. WSSA, Champaign, IL.
  3. Hayes, W.J. and E.R. Laws (ed.). 1990. Handbook of Pesticide Toxicology, Vol. 3, Classes of Pesticides. Academic Press, Inc., NY.
  4. Meister, R.T. (ed.). 1991. Farm Chemicals Handbook '91. Meister Publishing Company, Willoughby, OH.
  5. Worthing, C.R. (ed.). 1987. The pesticide manual: A world compendium. 8th Ed. British Crop Protection Council. Croydon, England.
  6. Hayes, Wayland, Jr. 1982. Pesticides Studied in Man. Baltimore, MD: Williams & Wilkins.
  7. U.S. Department of Agriculture, Soil Conservation Service. 1990 (Nov). SCS/ARS/CES Pesticide Properties Database: Version 2.0 (Summary). USDA - Soil Conservation Service, Syracuse, NY.
  8. Hartley, D. and H. Kidd, (eds.) 1983. The agrochemicals handbook. Nottingham, England: Royal Society of Chemistry.
  9. Occupational Health Services, Inc. 1992 (Dec. 12). MSDS for Molinate. OHS Inc., Secaucus, NJ.
  10. Hallenbeck, W.H. & K.M. Cunningham-Burns. 1985. Pesticides and human health. New York: Springer-Verlag.
  11. Gosselin, R.E. 1984. Clinical toxicology of commercial products. 5th Ed. Baltimore, MD: Williams & Wilkins.
  12. Morgan, D.P. 1982. Recognition and management of pesticide poisonings. Iowa Pesticide Hazardous Assessment Project. 1982. Iowa City, IA.
  13. Sunshine, I. 1969. Handbook of analytical toxicology. Cleveland, OH: Chemical Rubber Co.