2,4-D

Herbicide vanc April 2025 2,4-Dichlorophenoxyacetic acid 2,4-Dichlorophenoxyacetic acid structure numbered.svg skin-invert-image correct ?? 210 2,4-dichlorophenoxyacetic acid 2,4-Dichlorophenoxyacetic-acid-3D-balls-2.png bg-transparent 220 Ball-and-stick model of 2,4-dichlorophenoxyacetic acid (2,4-Dichlorophenoxy)acetic acid 2,4-D correct EBI 28854 Clc1cc(Cl)ccc1OCC(=O)O 1486 correct kegg C03664 1/C8H6Cl2O3/c9-5-1-2-7(6(10)3-5)13-4-8(11)12/h1-3H,4H2,(H,11,12) OVSKIKFHRZPJSS-UHFFFAOYAM correct EBI 367623 correct chemspider 1S/C8H6Cl2O3/c9-5-1-2-7(6(10)3-5)13-4-8(11)12/h1-3H,4H2,(H,11,12) correct chemspider OVSKIKFHRZPJSS-UHFFFAOYSA-N 94-75-7 correct CAS correct FDA 2577AQ9262 correct chemspider 1441 8 6 2 3 221.04 g/mol white to yellow powder 900 mg/L 140.5 160 0.4 mm Hg ICSC 0033 07 05 supelco 49083 2,4-D March 17, 2022 302 317 318 335 412 261 273 280 305+351+338 nonflammable TWA 10 mg/m30173 TWA 10 mg/m3 100 mg/m3 500 mg/kg (oral, hamster) 100 mg/kg (oral, dog) 347 mg/kg (oral, mouse) 699 mg/kg (oral, rat)2,4-D https://www.cdc.gov/niosh/idlh/94757.html National Institute for Occupational Safety and Health December 4, 2014 February 26, 2015 2,4,5-T, Dichlorprop 2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula C8H6Cl2O3. It is usually referred to by its ISO common name 2,4-D.Compendium of Pesticide Common Names http://www.alanwood.net/pesticides/ It is a systemic herbicide that kills most broadleaf weeds by causing uncontrolled growth, but most grasses such as cereals, lawn turf, and grassland are relatively unaffected. 2,4-D is one of the oldest and most widely available herbicides and defoliants in the world, having been commercially available since 1945, and is now produced by many chemical companies since the patent on it has long since expired. It can be found in numerous commercial lawn herbicide mixtures, and is widely used as a weedkiller on cereal crops, pastures, and orchards. Over 1,500 herbicide products contain 2,4-D as an active ingredient. History List of multiple discoveries William Templeman found that when indole-3-acetic acid (IAA), a naturally occurring auxin, was used at high concentrations, it could stop plant growth. In 1940, he published his finding that IAA killed broadleaf plants within a cereal field.The effect upon the growth of plants of watering with solutions of plant-growth substances and of seed dressings containing these materials Annals of Applied Biology 27 4 Templeman W. G. Marmoy C. J. 453–471 November 1940 10.1111/j.1744-7348.1940.tb07517.x MCPA was discovered at about that time by his ICI group.Cobb Andrew H. https://books.google.com/books?id=hVK4vrpma2YC Herbicides and Plant Physiology Reade John P. H. June 9, 2011 John Wiley & Sons 978-1-4443-2249-1Andrew H. Cobb, John P. H. Reade. Herbicides and Plant Physiology. Wiley-Blackwell; 2nd edition (October 25, 2010) 978-1405129350Sec 7.1 In the United States, a similar search for an acid with a longer half life, i.e., a metabolically and environmentally more stable compound, led to 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), both phenoxy herbicides and analogs of IAA. Robert Pokorny, an industrial chemist for the C.B. Dolge Company in Westport, Connecticut, published their synthesis in 1941, with details of the biology reported in 1944 by Franklin D. Jones.New Compounds. Some Chlorophenoxyacetic Acids Journal of the American Chemical Society 63 6 Pokorny Robert 1768 1941 1941JAChS..63.1768P 10.1021/ja01851a601 The discovery of multiple similar phenoxy herbicides during World War II, is a case of multiple discovery. There were four groups working independently in the United Kingdom and the United States: William G. Templeman and associates at Imperial Chemical Industries (ICI) in the UK; Philip S. Nutman and associates at Rothamsted Research in the UK; Franklin D. Jones and associates at the American Chemical Paint Company; and Ezra Kraus, John W. Mitchell, and associates at the University of Chicago and the United States Department of Agriculture. All four groups were subject to wartime secrecy laws and did not follow the usual procedures of publication and patent disclosure. In December 1942, following a meeting at the Ministry of Agriculture the Rothamsted and ICI workers pooled resources and Nutman moved to Jealott's Hill to join the ICI effort.Jealott's Hill: Fifty years of Agricultural Research 1928-1978 F.C. Peacock Allen H.P. etal Chapter 5: Selective herbicides 35–41 Imperial Chemical Industries Ltd. 1978 0-901747-01-7 https://archive.org/details/jealottshillfift0000peac/page/1 The first scientific publication describing the 2,4-D structure and plant growth regulating activity was by Percy Zimmerman and Albert Hitchcock at the Boyce Thompson Institute,Substituted phenoxy and benzoic acid growth substances and the relation of structure to physiological activity. Contrib. Boyce Thompson Institute 12 Zimmerman Percy W. Hitchcock Albert E. 321–343 1942 who were not the original inventors. The precise sequence of early 2,4-D discovery events and publications has been discussed.In the beginning: the multiple discovery of the first hormone herbicides Weed Science 49 2 Troyer James 290–297 2001 10.1614/0043-1745(2001)049[0290:ITBTMD]2.0.CO;2 85637273 2,4-D was not used as a chemical warfare agent during World War II.Sec 7.1 The Allies of World War II were looking for a chemical to starve Nazi Germany and Japan into submission by killing their potato and rice crops, but 2,4-D was found to be ineffective for that purpose, because both crops tolerate it. Within a year after the war ended, 2,4-D was commercially released as an herbicide to control broadleaf weeds in grain crops such as rice and wheat,The weed-crop connection http://www.plantsciences.ucdavis.edu/plantsciences/features/fall2010_rotator/weeds3_weed_crop.htm University of California at Davis November 23, 2015 December 7, 2011 https://web.archive.org/web/20111207192448/http://www.plantsciences.ucdavis.edu/plantsciences/features/fall2010_rotator/weeds3_weed_crop.htm dead and in the 1950s it was registered in the United States to control size and enhance skin color in potatoes without affecting yields.Influence of growth regulators on skin colour and scab diseases of red-skinned potatoes Canadian Journal of Plant Science 90 5 Waterer D. 745–753 September 1, 2010 10.4141/CJPS10055 free The first publication of 2,4-D's use as a selective herbicide came in 1944.10.1021/ba-1950-0001.ch045 2,4-Dichlorophenoxyacetic Acid (2,4-D) as a Selective Herbicide Agricultural Control Chemicals 1 244–249 Advances in Chemistry 1950 Quastel J. H. 9780598202970The Herbicidal Action of 2,4 Dichlorophenoxyacetic and 2,4,5 Trichlorophenoxyacetic Acid on Bindweed https://archive.org/details/sim_science_1944-08-18_100_2590/page/154 Science 100 2590 Hamner CL, Tukey HB 154–155 1944 1944Sci...100..154H 10.1126/science.100.2590.154 17778584 The ability of 2,4-D to control broadleaf weeds in turf was documented soon thereafter, in 1944.Mitchell JW, Davis FF and Marth PC (1944) Turf and weed control with plant growth regulators. Golfdom 18:34-38. Starting in 1945, the American Chemical Paint Company brought 2,4-D to market as an herbicide called "Weedone". It revolutionized weed control, as it was the first compound that, at low doses, could selectively control dicotyledons (broadleaf plants), but not most monocotyledons — narrowleaf crops, such as wheat, maize (corn), rice, and similar cereal grass crops. At a time when labor was scarce and the need for increased food production was large, it literally "replaced the hoe".Sec 7.1 Its effectiveness, together with its non-corrosive, non-explosive and seemingly non-irritating or poisonous qualities, led to it being considered the best all-around herbicide by 1946.http://archive.org/details/sim_consumer-reports_1947?q=Fertilizer Consumer Reports 1947 Consumers Union of U.S., Inc. 1947 375 Englishhttps://archive.org/details/sim_consumer-reports_1947/page/374/mode/2up?q=Fertilizer Consumer Reports 1947 Buying Guide, p. 375. 2,4-D is one of the ingredients in Agent Orange, an herbicide that was widely used during the Malayan Emergency and the Vietnam War. However, 2,3,7,8-tetrachlorodibenzodioxin (TCDD), a contaminant in the production of another ingredient in Agent Orange, 2,4,5-T, was the cause of the adverse health effects associated with Agent Orange. In the 2000s, Dow AgroSciences developed a new choline salt version of 2,4-D (2,4-D choline) that Dow included in its "Enlist Duo" herbicide along with glyphosate and an agent that reduces drift; the choline salt form of 2,4-D is less volatile than 2,4-D.Enlist weed control system in Canada. A new tool for managing hard to control and resistant weeds http://www.agannex.com/energy/enlist-weed-control-system-in-canada AG Annex Fleury Donna April 2014 May 3, 2014 May 3, 2014 https://web.archive.org/web/20140503232918/http://www.agannex.com/energy/enlist-weed-control-system-in-canada deadDow AgroSciences Names Its Newest Herbicide Offering Enlist Duo http://farmprogress.com/story-dow-agrosciences-names-its-newest-herbicide-offering-duo-0-52677 Prairie Farmer Flint Josh August 31, 2011 May 4, 2014 https://web.archive.org/web/20140504025154/http://farmprogress.com/story-dow-agrosciences-names-its-newest-herbicide-offering-duo-0-52677 dead Manufacture 2,4-D is a member of the phenoxy family of herbicides. It is manufactured from chloroacetic acid and 2,4-dichlorophenol, which is itself produced by chlorination of phenol. Alternatively, it is produced by the chlorination of phenoxyacetic acid. The production processes may create several contaminants including di-, tri-, and tetrachlorodibenzo-p-dioxin isomers and N-nitrosamines, as well as monochlorophenol.2,4-Dichlorophenoxyacetic Acid (2,4-D) http://www.inchem.org/documents/ehc/ehc/ehc29.htm UNEP, WHO ILO International Programme on Chemical Safety 1984 February 2, 2020 thumb|right|Containers of 2-4 D herbicide, ca. 1947 Mode of action 2,4-D is a synthetic auxin that induces uncontrolled growth and eventually death in susceptible plants.Synthetic Auxins - MSU Extension Montana State University https://www.montana.edu/extension/pubs/herbicideinjuryguide/Auxins.html www.montana.edu December 29, 2023 December 29, 2023 https://web.archive.org/web/20231229173921/https://www.montana.edu/extension/pubs/herbicideinjuryguide/Auxins.html deadInsight into the mode of action of 2,4-dichlorophenoxyacetic acid (2,4-D) as an herbicide Journal of Integrative Plant Biology 56 2 Song Yaling 106–113 2014 2014JIPB...56..106S 10.1111/jipb.12131 free 24237670Weed Control Methods Handbook: 2,4-D http://www.invasive.org/gist/products/handbook/10.24-d.pdf invasive.org April 2001 November 1, 2015 March 4, 2016 https://web.archive.org/web/20160304113140/http://www.invasive.org/gist/products/handbook/10.24-d.pdf live It is absorbed through the leaves and is translocated to the meristems of the plant. Uncontrolled, unsustainable growth ensues, causing stem curl-over, leaf withering, and eventual plant death. 2,4-D is typically applied as an amine salt, but more potent ester versions exist, as well. thumb|right|Effect of 2-4-D foliar application on Lantana Applications 2,4-D is primarily used as a selective herbicide that kills many terrestrial and aquatic broadleaf weeds, but not grasses. 2,4-D can be found in commercial lawn herbicide mixtures, which often contain other active ingredients including mecoprop and dicamba. Over 1,500 herbicide products contain 2,4-D as an active ingredient.EPA Chemical Summary: 2,4-Dichlorophenoxyacetic Acid (2,4-D) http://www.epa.gov/teach/chem_summ/24D_summary.pdf September 10, 2015 https://web.archive.org/web/20150910115620/http://www.epa.gov/teach/chem_summ/24D_summary.pdf dead thumb|Estimated use of 2,4-D in the USA to 2019 A variety of sectors use products containing 2,4-D to kill weeds and unwanted vegetation. In agriculture, it was the first herbicide for selective killing of weeds but not crops. It has been used since 1945Herbicides – 2,4-D & Its Cousins http://www.livinghistoryfarm.org/farminginthe40s/pests_03.html Wessels Living History Farm Ganzel Bill November 12, 2015 November 12, 2015 https://web.archive.org/web/20151112095835/http://www.livinghistoryfarm.org/farminginthe40s/pests_03.html dead to control broad-leafed weeds in pastures, orchards, and cereal crops such as corn, oats, rice, and wheat.2,4-D as a Weed Killer http://ucanr.edu/repository/fileaccess.cfm?article=100374&p=MSQYWZ&CFID=82966751&CFTOKEN=41384002 University of California at Berkeley Harvey W.A. Robblns W.W. February 1947 November 12, 2015 December 8, 2015 https://web.archive.org/web/20151208153136/http://ucanr.edu/repository/fileaccess.cfm?article=100374&p=MSQYWZ&CFID=82966751&CFTOKEN=41384002 live Cereals, in particular, have excellent tolerance to 2,4-D when it is applied before planting. 2,4-D is the cheapest way for farmers to control winter annual weeds by spraying in the fall, often at the lowest recommended rate. This is particularly effective before planting beans, peas, lentils, and chickpeas.Fall Weed Control - FAQs http://www.agriculture.gov.sk.ca/adx/aspx/adxGetMedia.aspx?DocID=2686,339,14661,14613,81,1,Documents&MediaID=6006&Filename=Fall+Weed+Control+-+FAQs+-+Printer+Friendly.pdf Saskatchewan Ministry of Agriculture September 2008 November 12, 2015 December 8, 2015 https://web.archive.org/web/20151208160444/http://www.agriculture.gov.sk.ca/adx/aspx/adxGetMedia.aspx?DocID=2686,339,14661,14613,81,1,Documents&MediaID=6006&Filename=Fall+Weed+Control+-+FAQs+-+Printer+Friendly.pdf dead The estimated use of 2,4-D in US agriculture is mapped by the US Geological Survey. In 2019, the latest date for which figures are available, this reached 45000000 lb kg annually.Estimated Agricultural Use for 2,4-D, 2019 https://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2019&map=24D&hilo=L US Geological Survey October 12, 2021 December 27, 2021 In domestic lawn and garden maintenance, 2,4-D is commonly used. In forestry, it is used for stump treatment, trunk injection, and selective control of brush in conifer forests. Along roadways, railways, and power lines, it is used to control weeds and brush which might interfere with safe operation and damage equipment. Along waterways, it is used to control aquatic weeds that might interfere with boating, fishing, and swimming or clog irrigation and hydroelectric equipment. It is often used by government agencies to control the spread of invasive, noxious, and non-native weed species and prevent them from crowding out native species, and also to control many poisonous weeds such as poison ivy and poison oak.35–36 2,4-D Benefits http://www.24d.org/benefits/default.aspx The Industry Task Force II on 2,4-D Research Data 2015 November 6, 2015 November 2, 2015 https://web.archive.org/web/20151102024718/http://www.24d.org/benefits/default.aspx dead A 2010 monitoring study conducted in the US and Canada found that "current exposures to 2,4-D are below applicable exposure guidance values."Biomonitoring data for 2,4-dichlorophenoxyacetic acid in the United States and Canada: interpretation in a public health risk assessment context using Biomonitoring Equivalents Environmental Health Perspectives 118 2 Aylward LL, Morgan MK, Arbuckle TE, Barr DB, Burns CJ, Alexander BH, Hays SM 177–81 February 2010 2010EnvHP.118..177A 10.1289/ehp.0900970 2831914 20123603 2,4-D has been used in laboratories for plant research as a supplement in plant cell culture media such as MS medium since at least 1962.Murashige, T. and F. Skoog. A revised medium for rapid growth and bioassays with tobaccotissue cultures. Physiol. Plantarum 1962. 15:473-97. in: Physiological Comparisons of Pith Callus With Crown-Gall and Genetic Tumors of Nicotiana glauca, N. langsdorffii, and N. glauca-langsdorffii Grown in Vitro. II. Nutritional Physiology. Plant Physiology 44 7 Sharp WR, Gunckel JE 1073–9 July 1969 10.1104/pp.44.7.1073 396217 16657160 2,4-D is used in plant cell cultures as a dedifferentiation (callus induction) hormone. It is classified as an auxin plant hormone derivative.Plant Cell Biotechnology Endreb Rudolf Springer 1994 978-0-387-56947-5 Germany 17, 18 Health effects Health effects of pesticides Pesticide poisoning Men who work with 2,4-D are at risk for abnormally shaped sperm and thus fertility problems; the risk depends on the amount and duration of exposure and other personal factors.The Effects of Workplace Hazards on Male Reproductive Health https://www.cdc.gov/niosh/docs/96-132/ NIOSH May 6, 2017 https://web.archive.org/web/20170506045837/https://www.cdc.gov/niosh/docs/96-132/ dead Acute toxicity According to the U.S. Environmental Protection Agency, "The toxicity of 2,4-D depends on its chemical forms, including salts, esters, and an acid form. 2,4-D generally has low toxicity for humans, except certain acid and salt forms can cause eye irritation. Swimming is restricted for 24 hours after application of certain 2,4-D products applied to control aquatic weeds to avoid eye irritation." 2005 the median lethal dose or LD50 determined in acute toxicity rat studies was 639 mg/kg.US EPA 2,4-D Reregistration Eligibility Decision, 2005. Associated RED Fact sheet https://web.archive.org/web/20080517130243/http://www.epa.gov/oppsrrd1/REDs/factsheets/24d_fs.htm May 17, 2008 EPA Urinary alkalinisation has been used in acute poisoning, but evidence to support its use is poor.Urinary alkalinisation for acute chlorophenoxy herbicide poisoning Cochrane Database Syst Rev 1 Roberts DM, Buckley NA 2007 10.1002/14651858.CD005488.pub2 17253558 CD005488 Roberts Darren M Cancer risk The International Agency for Research on Cancer classifies 2,4-D as a possible carcinogen to humans while the United States Environmental Protection Agency does not.2,4-Dichlorophenoxyacetic acid https://pubchem.ncbi.nlm.nih.gov/compound/2_4-dichlorophenoxyacetic_acid#section=NIOSH-Toxicity-Data pubchem.ncbi.nlm.nih.gov Pubchem May 29, 2015 https://web.archive.org/web/20150529110140/http://pubchem.ncbi.nlm.nih.gov/compound/2_4-dichlorophenoxyacetic_acid#section=NIOSH-Toxicity-Data deadCarcinogenicity of lindane, DDT, and 2,4-dichlorophenoxyacetic acid The Lancet Oncology 16 8 Loomis Dana 891–892 June 22, 2015 10.1016/s1470-2045(15)00081-9 26111929 The International Agency for Research on Cancer (IARC), said 2,4-D was classified as "possibly carcinogenic to humans (Group 2B), based on inadequate evidence in humans and limited evidence in experimental animals".IARC Monographs evaluate DDT, lindane, and 2,4-D https://www.iarc.fr/en/media-centre/pr/2015/pdfs/pr236_E.pdf June 23, 2015 February 14, 2016 In June 2015 the World Health Organization's International Agency for Research on Cancer confirmed its 1987 classification of 2,4-D as a possible carcinogen.Carcinogenicity of lindane, DDT, and 2,4-dichlorophenoxyacetic acid The Lancet Oncology 16 8 Loomis Dana Guyton Kathryn Grosse Yann El Ghissasi Fatiha Bouvard Véronique Benbrahim-Tallaa Lamia Guha Neela Mattock Heidi Straif Kurt 891–892 August 2015 10.1016/S1470-2045(15)00081-9 26111929Carey Gillam for Reuters. June 22, 2015 WHO unit finds 2,4-D herbicide 'possibly' causes cancer in humans https://web.archive.org/web/20150623144109/http://www.msn.com/en-us/news/us/who-unit-finds-24-d-herbicide-possibly-causes-cancer-in-humans/ar-AAbYBtV June 23, 2015 On August 8, 2007, the EPA issued a ruling that existing data do not support a link between human cancer and 2,4-D exposure.EPA: Federal Register: 2,4-D, 2,4-DP, and 2,4-DB; Decision Not to Initiate Special Review http://www.epa.gov/fedrgstr/EPA-PEST/2007/August/Day-08/p15109.htm Epa.gov August 8, 2007 May 3, 2014 August 1, 2012 https://archive.today/20120801064011/http://www.epa.gov/fedrgstr/EPA-PEST/2007/August/Day-08/p15109.htm dead A 1995 panel of 13 scientists reviewing studies on the carcinogenicity of 2,4-D had divided opinions. None of the scientists thought the weight of the evidence indicated that 2,4-D was a "known" or "probable" cause of human cancer. The predominant opinion indicated that it is possible that 2,4-D can cause cancer in humans, although not all of the panelists believed the possibility was equally likely: one thought the possibility was strong, leaning toward probable, and five thought the possibility was remote, leaning toward unlikely. Two panelists believed it unlikely that 2,4-D can cause cancer in humans.Weight of the evidence on the human carcinogenicity of 2,4-D. Environ Health Perspect 96 Ibrahim MA Bond, GG Burke, TA Cole, P Dost, FN Enterline, PE etal 213–22 1991 1991EnvHP..96..213I 10.1289/ehp.9196213 1568222 1820267 In a prior 1987 report the IARC classified some chlorphenoxy herbicides including 2,4-D, MCPA and 2,4,5-T as a group as class 2B carcinogens - "possibly carcinogenic to humans".Chlorphenoxy Herbicides (Group 2B) in IARC monographs on the evaluation of carcinogenic risks to humans: An updating of IARC Monographs volumes 1 to 42. Supplement 7, WHO, Lyon, France 1987. 2,4-D has been linked to lymphoma and bladder cancer in dogs.Canine Cancers Linked to Lawn Care Chemicals https://emagazine.com/canine-cancers-linked-to-lawn-care-chemicals/ Harveston Kate March 13, 2019 Contaminants A July 2013 Four Corners investigation found elevated levels of dioxins in a generic version of 2,4-D, one of Australia's most widely used herbicides. Samples imported from China had "one of the highest dioxin readings for 2,4-D in the last 10 to 20 years, and could pose potential health risks."Four Corners investigation finds dangerous dioxins in widely used herbicide 2,4-D http://www.abc.net.au/news/2013-07-22/four-corners-dangerous-dioxins/4833848 Abc.net.au Four Corners By Janine Cohen July 22, 2013 May 3, 2014 Metabolism When radioactively labeled 2,4-D was fed to livestock, 90% or more of the total radioactive residue (TRR) was shed in urine unchanged or as conjugated forms of 2,4-D. A relatively small portion of 2,4-D was metabolized into dichlorophenol, dichloroanisole, 4-chlorophenoxyacetic acid (6.9% of the TRR in milk), and 2,4-dichlorophenol (5% of the TRR in milk; 7.3% of the TRR in eggs and 4% of the TRR in chicken liver). Residue levels in kidney were the highest.21 Environmental behavior Owing to the longevity and extent of use, 2,4-D has been evaluated several times by regulators and review committees.Potential impact of the herbicide 2,4-dichlorophenoxyacetic acid on human and ecosystems Environment International 111 Islam Faisal Wang Jian Farooq Muhammad A. Khan Muhammad S.S. Xu Ling Zhu Jinwen Zhao Min Muños Stéphane Li Qing X. Zhou Weijun 332–351 2018 2018EnInt.111..332I 10.1016/j.envint.2017.10.020 29203058Systematic Review of Carcinogenic Outcomes and Potential Mechanisms from Exposure to 2,4-D and MCPA in the Environment J Toxicol 2013 von Stackelberg K. A 2013 10.1155/2013/371610 free 3600329 23533401 371610Andrew Pollack for the New York Times. April 9, 2012 E.P.A. Denies an Environmental Group's Request to Ban a Widely Used Weed Killer Quote: "The E.P.A. has reviewed the safety of 2,4-D several times, particularly with regard to an increased risk of cancer." 2,4-D amine salts and esters are not persistent under most environmental conditions.National Pesticide Information Center NPIC 2,4-D Technical Fact Sheet The degradation of 2,4-D is rapid (half life of 6.2 days) in aerobic mineral soils.54 2,4-D is broken down by microbes in soil, in processes that involve hydroxylation, cleavage of the acid side-chain, decarboxylation, and ring opening. The ethyl hexyl form of the compound is rapidly hydrolyzed in soil and water to form the 2,4-D acid. 2,4-D has a low binding affinity in mineral soils and sediment, and in those conditions is considered intermediately to highly mobile, and therefore likely to leach if not degraded. In aerobic aquatic environments, the half life is 15 days. In anaerobic aquatic environments 2,4-D is more persistent, with a half life of 41 to 333 days.Combined Toxicity of 2,4-Dichlorophenoxyacetic Acid and Its Metabolites 2,4-Dichlorophenol (2,4-DCP) on Two Nontarget Organisms ACS Omega 4 1 Ju Zhen Liu Shu-Shen Xu Ya-Qian Li Kai 1669–1677 2019 10.1021/acsomega.8b02282 free 6648169 31459423 2,4-D has been detected in streams and shallow groundwater at low concentrations, in both rural and urban areas. Breakdown is pH dependent. Some ester forms are highly toxic to fish and other aquatic life.2,4-D General Fact Sheet http://npic.orst.edu/factsheets/24Dgen.html National Pesticide Information Center October 7, 2015 "The ester forms of 2,4-D can be highly toxic to fish and other aquatic life. 2,4-D generally has moderate toxicity to birds and mammals, is slightly toxic to fish and aquatic invertebrates, and is practically nontoxic to honeybees" per EPA.Ingredients Used in Pesticide Products 2,4-D https://www.epa.gov/ingredients-used-pesticide-products/24-d www2.epa.gov September 22, 2014 November 6, 2014 April 26, 2022 https://web.archive.org/web/20220426203157/https://www.epa.gov/ingredients-used-pesticide-products/24-d live Microbial breakdown A number of 2,4-D-degrading bacteria have been isolated and characterized from a variety of environmental habitats.Cavalca, L., A. Hartmann, N. Rouard, and G. Soulas. 1999. Diversity of tfdC genes: distribution and polymorphism among 2,4-dichlorophenoxyacetic acid degrading soil bacteria. FEMS Microbiology Ecology 29: 45-58.Characterization of a chromosomally encoded 2,4-dichlorophenoxyacetic acid alpha-ketoglutafate dioxygenase from Burkholderia sp. strain RASC Applied and Environmental Microbiology 62 7 Suwa Y. Wright A.D. Fukimori F. Nummy K.A. Hausinger R.P. Holben W.E. Forney L.J. 2464–2469 1996 1996ApEnM..62.2464S 10.1128/AEM.62.7.2464-2469.1996 168028 8779585 Metabolic pathways for the compound's degradation have been available for many years, and genes encoding 2,4-D catabolism have been identified for several organisms. As a result of the extensive metadata on environmental behavior, physiology, and genetics, 2,4-D was the first herbicide for which the bacteria actively responsible for in situ degradation were demonstrated.Identification of In Situ 2,4-Dichlorophenoxyacetic Acid-Degrading Soil Microorganisms using DNA-Stable Isotope Probing Soil Biology and Biochemistry 39 1 Cupples A.M. Sims G.K. 232–238 2007 2007SBiBi..39..232C 10.1016/j.soilbio.2006.07.011 This was accomplished using the technique of DNA-based stable isotope probing, which enables a microbial function (activity), such as degrading a chemical, to be linked with the organism's identity without the need to culture the organism involved.Stable-isotope probing as a tool in microbial ecology Nature 403 6770 Radajewski S. Ineson P. Parekh N.R. Murrell J.C. 646–649 2000 2000Natur.403..646R 10.1038/35001054 10688198 4395764 Regulation Maximum residue limits were first set in the EU in 2002 and re-evaluated in 2011 by the European Food Safety Authority, which concluded that the codex maximum residue limits were "not expected to be of concern for European consumers".Review of the existing maximum residue levels (MRLs) for 2,4-D according to Article 12 of Regulation (EC) No 396/2005 EFSA Journal 9 11 European Food Safety Authority 2431 November 2011 10.2903/j.efsa.2011.2431 free26 The total chronic exposure represented less than 10% of the acceptable daily intake (ADI).28 2,4-D is currently not approved for use on lawns and gardens in Denmark, Norway, Kuwait, and the Canadian provinces of QuébecThe Pesticides Management Code - Protecting the environment and health in our green spaces http://www.mddep.gouv.qc.ca/pesticides/permis-en/code-gestion-en/espace-vert.htm Mddep.gouv.qc.ca April 3, 2005 May 3, 2014 and Ontario.Ministry of the Environment | Ontario.ca http://www.ene.gov.on.ca/en/news/2009/030401.php Ene.gov.on.ca May 3, 2014June 2021 2,4-D use is severely restricted in the country of Belize. In 2008, Dow AgroScience, LLC, sued the Canadian government for allowing Quebec to ban 2,4-D, but settled in 2011.Deal confirms government's right to ban 'cosmetic' pesticides, minister says https://www.theglobeandmail.com/news/national/deal-confirms-governments-right-to-ban-cosmetic-pesticides-minister-says/article581189/ The Globe and Mail McKenna Barrie May 27, 2011 June 26, 2015 In 2012, EPA denied the petition filed November 6, 2008, by the Natural Resources Defense Council to revoke all tolerances and to cancel all registrations of 2,4-D. EPA stated that new study and EPA's comprehensive review confirmed EPA's previous finding that the 2,4-D tolerances are safe at anticipated exposure.Petition to Revoke All Tolerances and Cancel All Registrations for the Pesticide 2,4-Dichlorophenoxyacetic Acid (2,4-D); Notice of Availability http://www.regulations.gov/#!docketDetail;dct=FR+PR+N+O+SR;rpp=25;po=0;D=EPA-HQ-OPP-2008-0877 Docket Folder Summary Docket ID: EPA-HQ-OPP-2008-0877 Agency: EPA April 7, 2012 September 12, 20122,4-D; Order Denying NRDC's Petition To Revoke Tolerances http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2008-0877-0446 Order Federal Register 77 75 (Wednesday, April 18, 2012) 23135–23158 April 18, 2012 September 12, 2012 Petitions to Revoke Tolerances; Denials: Natural Resources Defense Council, 2,4-dichlorophenoxyacetic acid (2-4D) Document ID: EPA-HQ-OPP-2008-0877-0446 Document Type: Rule Docket ID: EPA-HQ-OPP-2008-0877 The estimated annual use of 2,4-D in US agriculture is mapped by the US Geological Service.Estimated Agricultural Use for 2,4-D in the USA, 2016 https://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2016&map=24D&hilo=L&disp=2,4-D US Geological Survey February 15, 2020 In October 2014, the US EPA registered Enlist Duo, an herbicide containing the less volatile 2,4-D choline salt, glyphosate, and an antidrift agent, for use in six states: Illinois, Indiana, Iowa, Ohio, South Dakota, and Wisconsin.EPA Press Release. October 15, 2014 EPA Announces Final Decision to Register Enlist Duo, Herbicide Containing 2, 4-D and Glyphosate/Risk assessment ensures protection of human health, including infants, children EPA Documents: Registration of Enlist Duo In November 2015, the EPA attempted to withdraw its own approval of Enlist Duo, as a result of legal actions against both the agency and Dow by two U.S. groups. However, while it was implied that the approval was "gone" because of the action, in fact, Enlist Duo was still approved pending a decision by the courts. On January 25, 2016, the US Ninth Circuit Court of Appeals denied EPA's motion to vacate its Enlist Duo registration. Dow stated the product would be available in 15 US states and Canada for the 2016 crop season.Ninth Circuit Court denies move by EPA to vacate herbicide label https://www.farmprogress.com/soybeans/federal-court-denies-move-epa-vacate-herbicide-label Farm Futures Vogt Willie January 26, 2016 February 5, 2016U.S. court upholds Enlist Duo registration http://www.agcanada.com/daily/u-s-court-upholds-enlist-duo-registration AGCanada.com January 29, 2016 February 5, 2016 On August 21, 2013, the Australian Pesticides and Veterinary Medicines Authority (APVMA) banned selected 2,4-D high volatile ester (HVE) products due to their environmental hazards. HVE 2,4-D products had already been banned in Europe and North America for 20 years; low volatile ester products continue to be available in Australia and worldwide.APVMA 2,4-D Review webpage http://www.apvma.gov.au/products/review/current/2_4_d.php APVMA June 6, 2014 June 6, 2014 https://web.archive.org/web/20140606215228/http://www.apvma.gov.au/products/review/current/2_4_d.php dead In July 2013 APVMA published their report findings.Annex to the APVMA's Preliminary Review Findings (Environment) Part 1 2,4-D Esters Volume 1 Review Summary April 2006 http://www.apvma.gov.au/products/review/docs/2-4-d-hve.pdf APVMA July 2013 August 25, 2016 June 6, 2014 https://web.archive.org/web/20140606215344/http://www.apvma.gov.au/products/review/docs/2-4-d-hve.pdf dead Genetically modified crops In 2010, Dow published that it had created genetically modified soybeans made resistant to 2,4-D by insertion of a bacterial aryloxyalkanoate dioxygenase gene, aad1.Robust crop resistance to broadleaf and grass herbicides provided by aryloxyalkanoate dioxygenase transgenes Proceedings of the National Academy of Sciences of the United States of America 107 47 Wright TR Shan G Walsh TA Lira JM Cui C Song P Zhuang M Arnold NL Lin G Yau K 20240–5 November 23, 2010 2010PNAS..10720240W 10.1073/pnas.1013154107 free 2996712 21059954 Russell SM Cicchillo RM Peterson MA Simpson DM Zhou N Ponsamuel J Zhang ZMark A. Peterson, Guomin Shan, Terence A. Walsh, and Terry R. Wright. Utility of Aryloxyalkanoate Dioxygenase Transgenes for Development of New Herbicide Resistant Crop Technologies ISB News Report,3 pages, May 2011, Research & Development, Dow AgroSciences, Indianapolis1 Dow intended it to be used as an alternative or complement to Roundup Ready crops due to the increasing prevalence of glyphosate-resistant weeds.Dow Weed Killer, Nearing Approval, Runs Into Opposition https://www.nytimes.com/2012/04/26/business/energy-environment/dow-weed-killer-runs-into-opposition.html The New York Times Pollack Andrew April 25, 2012 April 25, 2012 As of April 2014 genetically modified maize and soybeans resistant to 24-D and glyphosate have been approved in Canada. In September 2014 the USDA also approved Dow's maize and soybeans and in October the EPA registered the "Enlist Duo" herbicide containing 24-D and glyphosate.ISAAA GM Approval Database GM Approval Database Genes List Gene: aad1. International Service for the Acquisition of Agri-biotech Applications (ISAAA) n.d. accessed February 27 2015New Generation of GM Crops Puts Agriculture in a 'Crisis Situation' https://www.wired.com/2014/09/new-gm-crops/ Wired Keim Brandon September 25, 2014 April 13, 2015 See also Genetically modified crops#Herbicide resistance Genetic pollution References 30em External links and further reading CDC - NIOSH Pocket Guide to Chemical Hazards Overview of the toxic effects of 2,4-D Sierra Club Canada January 2005 "Review of 2,4-dichlorophenoxyacetic acid (2,4-D) biomonitoring and epidemiology" Review of the literature by Dow scientists Crit Rev Toxicol. Oct 2012 PPDB Pesticides Properties database entry for 2,4-D 2,4-D on Pubchem Category:Dichlorophenyl compounds Category:Auxinic herbicides Category:Phenoxyacetic acids Category:Acetic acids Category:Plant growth regulators Category:IARC Group 2B carcinogens Category:Systemic herbicides Category:Group 4 herbicides