Pyrethrin
The pyrethrins are a class of
Pyrethrins are gradually replacing
Chemistry
Group | Pyrethrin I | Pyrethrin II | ||||
---|---|---|---|---|---|---|
Chemical compound | Pyrethrin I[3][4] | Cinerin I[5][4] | Jasmolin I[6] | Pyrethrin II[7][4] | Cinerin II[8][4] | Jasmolin II[9] |
Chemical structure | ||||||
Chemical formula | C21H28O3 | C20H28O3 | C21H30O3 | C22H28O5 | C21H28O5 | C22H30O5 |
Molecular mass (g/mol) | 328.4 | 316.4 | 330.5 | 372.5 | 360.4 | 374.5 |
Boiling point (°C) | 170 | 137 | ? | 200 | 183 | ? |
Vapor pressure at 25 °C (mmHg) | 2.03×10−5 | 1.13×10−6 | ? | 3.98×10−7 | 4.59×10−7 | ? |
Solubility in water (mg/L) | 0.2 | 0.085 | ? | 9.0 | 0.03 | ? |
History
The pyrethrins occur in the seed cases of the
Biosynthesis
Well after their use as insecticides began, their chemical structures were determined by
Production
Commercial pyrethrin production mainly takes place in mountainous equatorial zones. The commercial cultivation of the Dalmatian chrysanthemum (C. cinerariifolium) takes place at an altitude of 1600 to 3000 meters[15] above sea level.[16] This is done because pyrethrin concentration has been shown to increase as elevation increases to this level. Growing these plants does not require much water because semiarid conditions and a cool winter deliver optimal pyrethrin production. The Persian chrysanthemum C. coccineum also produces pyrethrins but at a much lower level. Both may be planted in low-altitude zones in dry soil, but the pyrethrin level is lower.[15]
Most of the world's supply of pyrethrin and C. cinerariaefolium comes from
Processing the flowers to cultivate the pyrethrin is often a lengthy process, and one that varies from area to area. For instance, in Japan, the flowers are hung upside down to dry which increases pyrethrin concentration slightly.[15] To process pyrethrin, the flowers must be crushed. The degree to which the flower is crushed has an effect on both the longevity of the pyrethrin usage and the quality. The finer powder produced is better suited for use as an insecticide than the more coarsely crushed flowers. However, the more coarsely crushed flowers have a longer shelf life and deteriorate less.[15]
Use as an insecticide
Pyrethrin is most commonly used as an insecticide and has been used for this purpose since the 1900s.[18] In the 1800s, it was known as "Persian powder", "Persian pellitory", and "zacherlin". Pyrethrins delay the closure of voltage-gated sodium channels in the nerve cells of insects, resulting in repeated and extended nerve firings. This hyperexcitation causes the death of the insect due to loss of motor coordination and paralysis.[19] Resistance to pyrethrin has been bypassed by pairing the insecticide with synthetic synergists such as piperonyl butoxide. Together, these two compounds prevent detoxification in the insect, ensuring insect death.[20] Synergists make pyrethrin more effective, allowing lower doses to be effective. Pyrethrins are effective insecticides because they selectively target insects rather than mammals due to higher insect nerve sensitivity, smaller insect body size, lower mammalian skin absorption, and more efficient mammalian hepatic metabolism.[21] Also, mammals are able to process pyrethrin quickly and have higher body temperatures which prevent pyrethrin from working effectively [22]
Although pyrethrin is a potent insecticide, it also functions as an insect repellent at lower concentrations. Observations in food establishments demonstrate that flies are not immediately killed, but are found more often on windowsills or near doorways. This suggests, due to the low dosage applied, that insects are driven to leave the area before dying.[23] Because of their insecticide and insect repellent effect, pyrethrins have been very successful in reducing insect pest populations that affect humans, crops, livestock, and pets, such as ants, spiders, and lice, as well as potentially disease-carrying mosquitoes, fleas, and ticks.
As pyrethrins and pyrethroids are increasingly being used as insecticides, the number of illnesses and injuries associated with exposure to these chemicals is also increasing.[24] However, few cases leading to serious health effects or mortality in humans have occurred, which is why pyrethroids are labeled "low-toxicity" chemicals and are ubiquitous in home-care products.[21] Pyrethrins are widely regarded as better for the environment, and can be harmless if used only in the field with localized sprays, as UV exposure breaks them down into harmless compounds. Additionally, they have little lasting effect on plants, degrading naturally or being degraded by the cooking process.[25]
Specific pest species that have been successfully controlled by pyrethrum include: potato, beet, grape, and six-spotted leafhopper, cabbage looper, celery leaf tier, Say's stink bug, twelve-spotted cucumber beetle, lygus bugs on peaches, grape and flower thrips, and cranberry fruitworm.[26]
Toxicity
Pyrethrins are among the safest insecticides on the market due to their rapid degradation in the environment.
Similarities between the chemistry of pyrethrins and synthetic pyrethroids include a similar mode of action and almost identical toxicity to insects (i.e., both pyrethrins and pyrethroids induce a toxic effect within the insect by acting on sodium channels).[27]
Some differences in the chemistry between pyrethrins and synthetic pyrethroids have the result that synthetic pyrethroids have relatively longer environmental persistence than do pyrethrins. Pyrethrins have shorter environmental persistence than synthetic pyrethroids because their chemical structure is more susceptible to the presence of UV light and changes in pH.[citation needed]
The use of pyrethrin in products such as natural insecticides and pet shampoo, for its ability to kill fleas, increases the likelihood of toxicity in mammals that are exposed. Medical cases have emerged showing fatalities from the use of pyrethrin, prompting many organic farmers to cease use. One fatal case of an 11-year-old girl with a known asthmatic condition and who used shampoo containing only a small amount (0.2% pyrethrin) to wash her dog was documented.[28]
Chronic pyrethrin toxicity in humans
Pyrethrum toxicity
Exposure to pyrethrum, the crude form of pyrethrin,[31] causes harmful health effects for mammals. Pyrethrum also has an allergenic effect that commercial pyrethroids don't have.[31] In mammals, toxic exposure to pyrethrum can lead to tongue and lip numbness, drooling, lethargy, muscle tremors, respiratory failure, vomiting, diarrhea, seizures, paralysis, and death.[29] Exposure to pyrethrum in high levels in humans may cause symptoms such as asthmatic breathing, sneezing, nasal stuffiness, headache, nausea, loss of coordination, tremors, convulsions, facial flushing, and swelling.[32][unreliable source?] A possibility of damage to the immune system exists that leads to a worsening of allergies following toxicity.[29] Infants are unable to resourcefully break down pyrethrum due to the ease of skin penetration, causing similar symptoms as adults, but with an increased risk of death.[33]
Environmental effects
Aquatic habitats
In aquatic settings, toxicity of pyrethrin fluctuates, increasing with rising temperatures, water, and acidity. Run-off after application has become a concern for sediment-dwelling aquatic organisms because pyrethroids can accumulate in these areas.
Terrestrial Habitats
Pyrethrin is mainly used on land and can also have impacts in the places that it is used. For instance pyrethrin has the ability to be persistent in the fields that it is sprayed on. This persistence in crops can lead to negative effects for meat production.[37]
Bees
Pyrethrins are applied broadly as nonspecific insecticides.
References
- ^ a b Mader, Eric, and Nancy Lee Adamson. "Organic-Approved Pesticides."Organic-Approved Pesticides (n.d.): n. pag. The Xerxes Society. The Xerces Society for Invertebrate Conservation, Oct. 2012. Web. 10 Mar. 2015. <http://www.xerces.org/wp-content/uploads/2009/12/xerces-organic-approved-pesticides-factsheet.pdf>
- ^ "Pyrethrins General Fact Sheet". npic.orst.edu. Retrieved 2022-09-26.
- ^ CID 5281045 from PubChem
- ^ ISBN 978-1-4557-3148-0, retrieved 2022-01-12
- ^ PubChem. "Cinerin I". pubchem.ncbi.nlm.nih.gov. Retrieved 2021-10-26.
- ^ CID 12304687 from PubChem
- ^ PubChem. "Pyrethrin II". pubchem.ncbi.nlm.nih.gov. Retrieved 2021-10-26.
- ^ CID 5281548 from PubChem
- ^ CID 12304690 from PubChem
- ^ a b "History." [dubious ] Pyrethrum Nature's Insecticide. MGK, n.d. Web. 23 Apr. 2015.
- .
- ^ Merck Index (11th ed.). p. 7978.[full citation needed]
- ^ Townsend, Michael. McGraw-Hill Ryerson Chemistry 12. p. 99.[full citation needed]
- PMID 11287653.
- ^ a b c d "HOME PRODUCTION OF PYRETHRUM." Home Production of Pyrethrum. N.p., n.d. Web. 23 Apr. 2015.
- ^ Anonym. 1987 (March). Pepping up pesticides naturally. Organic Gardening, 34(3):8.
- ISBN 0-19-508210-9.
- ^ ISBN 978-3-527-30673-2.
- ^ "Pyrethrins General Fact Sheet." National Pesticide Information Center (n.d.): n. pag. Nov. 2014. Web. 26 Apr. 2015. <http://npic.orst.edu/factsheets/pyrethrins.pdf>
- ^ "Pyrethrin." Asktheexterminator.com. Ask the Exterminator, 2011. Web. 2 Apr. 2015. <http://www.asktheexterminator.com/Pesticide/Pyrethrin.shtml Archived 2011-09-04 at the Wayback Machine>
- ^ S2CID 32523158.
- ^ "Pyrethrin - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2022-11-06.
- ^ Todd, G Daniel, David Wohlers, and Mario Citra. "Toxicological Profile for Pyrethrins and Pyrethroids." ATSDR. Agency for Toxic Substances and Disease Registry, Sept. 2001. Web. 26 Apr. 2015. <http://www.atsdr.cdc.gov/ToxProfiles/tp155.pdf>
- PMID 18072143.
- ISBN 9780849356070.
- ^ Caldwell, Brian, Eric Sideman, Abby Seaman, Anthony Shelton, and Christine Smart. "Resource Guide for Organic Insect and Disease Management." (n.d.): n. pag. Cornell University, 2013. Web. 23 Mar. 2015. <http://web.pppmb.cals.cornell.edu/resourceguide/pdf/resource-guide-for-organic-insect-and-disease-management.pdf>
- PMID 31406060.
- PMID 10924422.
- ^ a b c d "Pyrethrins". Extension Toxicology Network. 1996.
- PMID 2083034.
- ^ a b c "Review of the Relationship between Pyrethrins, Pyrethroid Exposure and Asthma and Allergies". US Environmental Protection Agency Office of Pesticide Programs. Sep 2009.
- ^ Occupational Health Services, Inc. "Pyrethrum." Material Safety Data Sheet. 1 April 1987. New York: OHS, Inc.
- ^ "Public Health Statement for Pyrethrins and Pyrethroids". Agency for Toxic Substances & Disease Registry. Sep 2003.
- ^ "Pyrethroids and Pyrethrins". EPA. Dec 2013.
- ^ a b "Environmental Hazard and General Labeling for Pyrethroid Non-Agricultural Outdoor Products". EPA. Feb 2013.
- ^ "Pyrethroids and Pyrethrins." EPA. Environmental Protection Agency, Dec. 2013. Web. 26 Apr. 2015. <http://www.epa.gov/oppsrrd1/reevaluation/pyrethroids-pyrethrins.html#eco>
- PMID 34201914.
- ^ Hooven, L., R. Sagili, and E. Johansen. "How to Reduce Bee Poisoning from Pesticides." (n.d.): n. pag. Oregon State University, Dec. 2006. Web. 23 Mar. 2015. <http://www.ipm.ucdavis.edu/PDF/PMG/pnw591.pdf>
External links
- International Center for Pyrethrum research
- Pyrethrins and Pyrethroids Fact Sheet - National Pesticide Information Center
- Pyrethrins and pyrethroids on the EXTOXNET
- Pyrethrin and Permethrin Toxicity in Dogs and Cats
- Wagner, S. L. (2000). "Fatal asthma in a child after use of an animal shampoo containing pyrethrin". The Western Journal of Medicine. 173 (2): 86–7. PMID 10924422.
- Horton, M. K.; Rundle, A.; Camann, D. E.; Boyd Barr, D.; Rauh, V. A.; Whyatt, R. M. (2011). "Impact of Prenatal Exposure to Piperonyl Butoxide and Permethrin on 36-Month Neurodevelopment". Pediatrics. 127 (3): e699–706. PMID 21300677.
- "Common insecticide used in homes associated with delayed mental development of young children". ScienceDaily (Press release). February 10, 2011.