Carbofuran

2021-06-04

Carbofuran is one of the most toxic carbamate pesticides. It is marketed under the trade names Furadan, by FMC Corporation and Curater, among several others. The technical or chemical name of carbofuran is 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate and its CAS number is 1563-66-2. It is manufactured by the reaction of methyl isocyanate with 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran. [1] Carbofuran is a white crystalline solid with a slightly phenolic odour. [2] It is a systemic insecticide, which means that the plant absorbs it through the roots, and from here the plant distributes it throughout its organs where insecticidal concentrations are attained. Carbofuran also has contact activity against pests. [1]

Uses [2]

Carbofuran is a broad spectrum insecticide that is sprayed directly onto soil and plants just after emergence to control beetles, nematodes and rootworm. The greatest use of carbofuran is on alfalfa and rice, with turf and grapes making up most of the remainder. Earlier uses were primarily on corn crops. Carbofuran is allowed for use on only a few U.S. crops and will soon be banned for use on corn and sorghum in California.

Environmental Fate

Breakdown in Soil and Groundwater

  • Carbofuran is soluble in water and is moderately persistent in soil. Its half-life is 30 to 120 days. In soil, carbofuran is degraded by chemical hydrolysis and microbial processes. Hydrolysis occurs more rapidly in alkaline soils.
  • Carbofuran breaks down in sunlight.
  • Carbofuran has a high potential for groundwater contamination
  • Carbofuran is mobile to very mobile in sandy loam, silty clay, and silty loam soils; moderately mobile in silty clay loam soils; and only slightly mobile in muck soils. Small amounts of carbofuran have been detected (1 to 5 ppb) in water table aquifers beneath sandy soils in New York and Wisconsin.

Breakdown in Water

In water, carbofuran is subject to degradation by chemical hydrolysis under alkaline conditions. Photodegradation and aquatic microbes may also contribute to degradation. The hydrolysis half-lives of carbofuran in water at 25 C are 690, 8.2, and 1.0 weeks at pH values of 6.0, 7.0, and 8.0, respectively. Carbofuran does not volatilise from water, nor does it adsorb to sediment or suspended particles.

Breakdown in vegetation

The half-life of carbofuran on crops is about 4 days when applied to roots, and longer than 4 days if applied to the leaves.

Routes of Exposure [3]

Carbofuran is highly toxic by inhalation and ingestion and moderately toxic by dermal absorption. Carbofuran causes cholinesterase inhibition in both humans and animals, affecting nervous system function. As with other carbamate compounds, carbofuran’s cholinesterase-inhibiting effect is short-term and reversible. Carbofuran is poorly absorbed through the skin. It is metabolised in the liver and eventually excreted in the urine. The half-life in the body is from 6 to 12 hours. Less than 1% of a dose will be excreted in a mother’s milk. It does not accumulate in tissue.

Health Effects [3]

Acute Effects

Symptoms of carbofuran poisoning include: nausea, vomiting, abdominal cramps, sweating, diarrhoea, excessive salivation, weakness, imbalance, blurring of vision, breathing difficulty, increased blood pressure, and incontinence. Death may result at high doses from respiratory system failure associated with carbofuran exposure. Complete recovery from an acute poisoning by carbofuran, with no long-term health effects, is possible if exposure ceases and the victim has time to regain their normal level of cholinesterase and to recover from symptoms. The oral LD50 is 5 to 13 mg/kg in rats, 2 mg/kg in mice, and 19 mg/kg in dogs. The dermal LD50 is >1000 mg/kg in rabbits. The LC50 (4-hour) for inhalation of carbofuran is 0.043 to 0.053 mg/L in guinea pigs.

Chronic Effects

Rats given very high doses (5 mg/kg/day) for two years showed decreases in weight. Similar tests with mice gave the same results. Prolonged or repeated exposure to carbofuran may cause the same effects as an acute exposure.

Reproductive Effects

Consuming high doses over long periods of time caused damage to testes in dogs, but carbofuran did not have any reproductive effects on rats or mice. Available studies indicate carbofuran is unlikely to cause reproductive effects in humans at expected exposure levels.

Teratogenic Effects

Studies indicate carbofuran is not teratogenic. No significant teratogenic effects have been found in offspring of rats given carbofuran (3 mg/kg/day) on days 5 to 19 of gestation. No effects were found in offspring of mice given as much as 1 mg/kg/day throughout gestation. In rabbits, up to 1 mg/kg/day on days 6 to 18 of gestation was not teratogenic.

Mutagenic Effects

Weak or no mutagenic effects have been reported in animals and bacteria. Carbofuran is most likely nonmutagenic.

Carcinogenic Effects

Data from animal studies indicate that carbofuran does not pose a risk of cancer to humans.

Safety [4]

First Aid Measures

  • Inhalation: If breathed in, move person into fresh air. If not breathing, give artificial respiration. Consult a physician.
  • Dermal contact: Wash off with soap and plenty of water. Take victim immediately to hospital. Consult a physician.
  • Eye contact: Flush eyes with water as a precaution.
  • Ingestion: Never give anything by mouth to an unconscious person. Rinse mouth with water. Consult a physician.

Personal Protection Equipment

  • Respiratory protection: Where risk assessment shows air-purifying respirators are appropriate use a full-face particle respirator type N100 (US) or type P3 (EN 143) respirator cartridges as a backup to engineering controls. If the respirator is the sole means of protection, use a full-face supplied air respirator. Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
  • Hand protection: Handle with gloves. Gloves must be inspected prior to use. Use proper glove removal technique (without touching glove’s outer surface) to avoid skin contact with this product. Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. Wash and dry hands. The selected protective gloves have to satisfy the specifications of EU Directive 89/686/EEC and the standard EN 374 derived from it.
  • Eye protection: Face shield and safety glasses Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
  • Skin and body protection: Complete suit protecting against chemicals, the type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
  • Hygiene measures: Avoid contact with skin, eyes and clothing. Wash hands before breaks and immediately after handling the product.

Regulation [1,2,5,6,7]

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.

References

http://en.wikipedia.org/wiki/Carbofuran

http://water.epa.gov/drink/contaminants/basicinformation/carbofuran.cfm

http://extoxnet.orst.edu/pips/carbofur.htm

http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=AU&language=en&productNumber=426008&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Faldrich%2F426008%3Flang%3Den

http://www.osha.gov/dts/chemicalsampling/data/CH_225200.html

http://www.safeworkaustralia.gov.au/sites/SWA/AboutSafeWorkAustralia/WhatWeDo/Publications/Documents/639/Workplace_Exposure_Standards_for_Airborne_Contaminants.pdf

http://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/eh52_aust_drinking_water_guidelines_1.pdf