What is Carbofuran?

Chemical Name: 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate

CAS Number: 1563-66-2

Carbofuran is a white crystalline solid with a slightly phenolic odour. It is widely known as one of the most toxic carbamate pesticides. A systemic insecticide, carbofuran is absorbed through the roots and distributed throughout plant tissues, reaching insecticidal concentrations across the plant. It also exhibits contact activity against pests.

Marketed under trade names such as Furadan (FMC Corporation) and Curater, among others, carbofuran is synthesised by the reaction of methyl isocyanate with 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran.

What is Carbofuran used for?

Carbofuran is a broad-spectrum insecticide primarily used for early-season pest control. It is applied to soil and plants just after emergence to manage beetles, nematodes, and rootworms. Its major applications are on alfalfa and rice, with lesser usage on turf and grapes. Previously used extensively on corn crops, its use has become more restricted. In California, for example, it is being phased out for corn and sorghum.

Environmental Fate

Breakdown in Soil and Groundwater

Carbofuran is moderately persistent in soil, with a half-life ranging from 30 to 120 days. It degrades via chemical hydrolysis and microbial activity, with hydrolysis occurring more rapidly in alkaline soils. The chemical is also light-sensitive, breaking down in sunlight.

Due to its solubility in water and high mobility in soils such as sandy loam, silty clay, and silty loam, carbofuran has a high potential for groundwater contamination. It is less mobile in muck soils. Trace amounts (1–5 ppb) have been detected in water table aquifers under sandy soils in New York and Wisconsin.

Breakdown in Water

In water, carbofuran undergoes chemical hydrolysis, particularly under alkaline conditions. It also degrades via photodegradation and aquatic microbes. Hydrolysis half-lives at 25°C are:

• pH 6.0: 690 weeks
• pH 7.0: 8.2 weeks
• pH 8.0: 1.0 week

Carbofuran does not volatilise from water, nor does it adsorb to sediment or suspended particles.

Breakdown in Vegetation

When applied to plant roots, the half-life is around 4 days and slightly longer when applied to leaves.

Routes of Exposure

Carbofuran is highly toxic via inhalation and ingestion and moderately toxic through dermal exposure. Like other carbamates, it inhibits cholinesterase, disrupting the nervous system. However, its effects are reversible and short-term. It is poorly absorbed through the skin, metabolised in the liver, and excreted in urine. The biological half-life is 6–12 hours, with less than 1% of the dose excreted in breast milk. It does not accumulate in tissues.

Health Effects

Acute Effects

Acute exposure may result in:

• Nausea, vomiting, cramps
• Diarrhoea, excessive salivation
• Weakness, blurred vision
• Respiratory difficulty, elevated blood pressure
• Incontinence

In severe cases, death may result from respiratory failure. Recovery is possible with timely treatment. Reported toxicity levels include:

• Oral LD50: 5–13 mg/kg (rats), 2 mg/kg (mice), 19 mg/kg (dogs)
• Dermal LD50: >1000 mg/kg (rabbits)
• Inhalation LC50 (4-hr): 0.043–0.053 mg/L (guinea pigs)

Chronic Effects

Long-term studies in rats and mice (5 mg/kg/day for 2 years) showed weight loss. Repeated exposure may result in similar effects to acute poisoning.

Reproductive Effects

High-dose exposure caused testicular damage in dogs, though no reproductive effects were observed in rats or mice. At expected exposure levels, carbofuran is unlikely to cause reproductive effects in humans.

Teratogenic Risk

Studies have shown no teratogenic effects:

• Rats: 3 mg/kg/day during gestation days 5–19
• Mice: Up to 1 mg/kg/day
• Rabbits: Up to 1 mg/kg/day (gestation days 6–18)

Mutagenic Effects

Weak or no mutagenic effects have been observed. Carbofuran is considered nonmutagenic.

Carcinogenic Effects

Animal studies have not shown evidence of carcinogenicity in humans.

Safety

First Aid Measures

• Inhalation: Move to fresh air. Give artificial respiration if needed. Seek medical attention.
• Dermal contact: Wash thoroughly with soap and water. Get medical attention immediately.
• Eye contact: Flush eyes with plenty of water.
• Ingestion: Do not give anything orally to an unconscious person. Rinse mouth and consult a physician.

Personal Protective Equipment

• Respiratory Protection: Use N100 or P3 respirators. For high exposure, use full-face supplied-air respirator.
• Hand Protection: Chemical-resistant gloves (compliant with EN 374/EU Directive 89/686/EEC).
• Eye Protection: Safety goggles and face shield (NIOSH or EN 166).
• Skin Protection: Full chemical-resistant suit.
• Hygiene: Avoid skin, eye, and clothing contact. Wash hands after handling.

Regulation

United States

• Under the Safe Drinking Water Act, the U.S EPA has set a Maximum Contaminant Level (MCL) = 0.04 milligrams per Litre (mg/L) or 40 parts per billion (ppb) and a Maximum Contaminant Level Goal (MCLG) = 0.04 mg/L or 40 ppb 
• In May 2009 the U.S EPA cancelled all food tolerances, an action which amounts to a de facto ban on its use on all crops grown for human consumption. 
• American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 0.1 mg/m3 TWA (Inhalable Fraction) (Vapour and Aerosol); Appendix A4 - Not Classifiable as a Human Carcinogen; BEI 
• National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): 0.1 mg/m3 TWA 

Australia

• Safe Work Australia has set an exposure standards of 0.1 TWA (mg/m3)
• Under the Australia Drinking Water Guidelines (2011), based on human health concerns, carbofuran in drinking water should not exceed 0.01 mg/L.

European Union

• The use of carbofuran has been banned in the European Union.