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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.


Publication Date: 9/95


Trade names for products containing formothion include Aflix, Anthio, Sandoz S-6900, SAN 2441 and SAN 69131 (1, 2, 3).


Formothion is a restricted use pesticide (RUP).


Formothion is an organophosphate product. It is a systemic and contact insecticide used to control spider mites, aphids, psyllids, mealy bugs, whiteflies, jassids, leaf miners, ermine moths, and fruit flies (1). It is used on tree fruits, vines, olives, hops, cereals, sugar cane, rice (3). The U.S. EPA classifies formothion as toxicity class II - moderately toxic. Products containing formothion bear the Signal Word "Warning." Formothion is available as an emulsifiable concentrate and an ultra-low volume spray (4).



Formothion is a cholinesterase inhibitor which means it affects normal nervous system function. Early symptoms of formothion poisoning include nausea or vomiting, dizziness, and weakness. Tightness in the chest and difficulty breathing are common in inhalation exposure. As in other organophosphate poisonings, exposure may cause blurred vision, muscle spasms, or loss of coordination (6).

The LD50, the dose of formothion which kills half of the test animals, is 365-500 mg/kg for rats; 410 - 420 mg/kg for rabbits; 102 mg/kg for mice; and 210 mg/kg for cats (5, 6). The LD50 is greater than 1,000 mg/kg for rats whose skin is exposed to formothion (1). The LC50 (4 hours), the concentration in air which kills half of the test animals, is 4.5 mg/l air for rats. Formothion is non-irritating to skin.


Teratogenic Effects

No evidence of teratogenic or embryotoxic effects was seen in rabbits given formothion from days 6 to 18 of pregnancy at rates of 6 and 30 mg/kg/day.(6)

Reproductive Effects

No information is currently available.

Mutagenic Effects

A number of studies on salmonella bacteria indicate that formothion is not mutagenic (7).

Carcinogenic Effects

Formothion is an organophosphate pesticide. Studies indicate that organophosphate compounds do not have structures resembling known carcinogens. Though no data is currently available on formothion, it is unlikely that it causes cancer.

Organ Toxicity

Cholinesterase is an enzyme critical to proper function of the nervous system. Formothion has been found to inhibit the activity of cholinesterase, impairing normal nervous system functions (3, 6). Also, in rat feeding studies, 16 mg/kg/day of formothion caused growth impairment in males during the first year of a two year study. It also caused slight tremors and muscle spasms in individual rats during the same time period. Rats tended to recover during the second year (6).

Fate in Humans and Animals

Formothion is rapidly absorbed by the stomach of rats. It passes through the liver, kidney, pancreas and thymus. Most (96%) of a dose of formothion is excreted within 24 hours. The majority of a dose (98-99%) is excreted in urine and 2% in feces (6).


Effects on Birds

Formothion is slightly toxic to birds. The oral LD50 for pigeons was 630 mg/kg (3).

Effects on Aquatic Organisms

Formothion is slightly toxic to fish. The LC50 (96 hours) for carp is greater than 50 mg/l (3).

Effects on Other Animals (Nontarget species)

Formothion is toxic to bees (2).


Breakdown of Chemical in Soil and Groundwater

Formothion is relatively non-persistent. The half-life of formothion in loamy soils is one to 14 days (3, 6). There is no danger of formothion residues accumulating in soil, even if plants are subject to repeated treatment (6).

Breakdown of Chemical in Surface Water

No information is currently available.

Breakdown of Chemical in Vegetation

In plants, formothion is metabolized rapidly and dissipates (3).


Formothion is a yellowish liquid or crystalline mass which is non-corrosive. It is extremely stable to acids but decomposes on distillation. It is incompatible with alkaline pesticides (6).

Physical Properties:

Chemical Name: O,O-dimethyl dithiophos- phorylacetic acid N-methyl-N-formylamide
CAS#: 2540-82-1
Melting point: 25-26 degrees C (3).
Solubility: Soluble in alcohols, ether, chloroform, ketones, and xylene (6)
Partition Coefficient: (octanol/water) ca. 30 (3)

Exposure Guidelines:

NOAEL: 4 mg/kg/day (rat) (1)
ADI: 0.2 mg/kg (6)


Sandoz Ltd.
1300 E. Touhy Avenue
Des Plaines, IL 60018
Telephone: 708-699-1616

Review by Basic Manufacturer:

Comments solicited: October, 1994
Comments received:


  1. Meister, R.T. 1992. Farm Chemicals Handbook '92. Meister Publishing Company. Willoughby, OH.
  2. Thomson, W. T. 1983. Agricultural Chemicals, Book I Insecticides. Thomson Publications. Fresno, CA.
  3. The Agrochemicals Handbook, Third Edition. 1994. Royal Society of Chemistry Information Systems, Unwin Brothers Ltd., Surrey, England.
  4. Meister, R.T. 1994. Farm Chemicals Handbook '94. Meister Publishing Company. Willoughby, OH.
  5. Budavari, Susan, (ed.). 1989. The Merck Index, Eleventh Edition. Merck and Company Inc. Rahway, NJ.
  6. U.S. Department of Health and Human Services. 1993. Hazardous Substance Data Base. HHS. Washington, DC.
  7. National Cancer Institute. 1990. Chemical Carcinogenesis Research Information System. U.S. Dept. of Health and Human Services TOXNET. Washington, DC.