Editing DDT (section)

==Properties and chemistry==
DDT is similar in structure to the insecticide [[methoxychlor]] and the [[acaricide]] [[dicofol]]. It is highly [[Hydrophobe|hydrophobic]] and nearly [[Solubility|insoluble]] in [[Properties of water|water]] but has good solubility in most [[Organic chemistry|organic]] [[solvent]]s, [[fat]]s and [[oil]]s. DDT does not occur naturally and is synthesised by consecutive [[Friedel–Crafts reaction]]s between [[chloral]] ({{chem|CCl|3|CHO}}) and two [[equivalent (chemistry)|equivalents]] of [[chlorobenzene]] ({{chem|C|6|H|5|Cl}}), in the presence of an acidic [[Catalysis|catalyst]].<ref name="ATSDRc5"/> DDT has been marketed under [[trade name]]s including Anofex, Cezarex, Chlorophenothane, Dicophane, Dinocide, Gesarol, Guesapon, Guesarol, Gyron, Ixodex, Neocid, Neocidol and Zerdane; [[international nonproprietary name|INN]] is clofenotane.<ref name=EHC009/>

===Isomers and related compounds===
Commercial DDT is a mixture of several closely related compounds. Due to the nature of the chemical reaction used to synthesize DDT, several combinations of ''ortho'' and ''para'' [[arene substitution pattern]]s are formed. The major component (77%) is the desired ''p'',''p{{'}}'' [[isomer]]. The ''o'',''p{{'}}'' isomeric impurity is also present in significant amounts (15%). [[Dichlorodiphenyldichloroethylene]] (DDE) and [[dichlorodiphenyldichloroethane]] (DDD) make up the balance of impurities in commercial samples. DDE and DDD are also the major [[metabolite]]s and environmental breakdown products.<ref name=EHC009/> DDT, DDE and DDD are sometimes referred to collectively as DDX.<ref>{{cite journal |pmid=22020740 |journal=J. Environ. Monit. |date=December 2011 |volume=13 |issue=12 |pages=3358–3364 |doi=10.1039/c1em10479a |title=Sources of organochlorine pesticides in air in an urban Mediterranean environment: volatilisation from soil |first1=G. |last1=Lammel |s2cid=22071869 |display-authors=et al }}</ref>

<gallery mode="packed" heights="100" caption="Components of commercial DDT" class="skin-invert-image">
File:P,p'-dichlorodiphenyltrichloroethane.svg|''p'',''p{{'}}''-DDT<br />(desired compound)
File:O,p'-dichlorodiphenyltrichloroethane.svg|''o'',''p{{'}}''-DDT<br />(isomeric impurity)
File:P,p'-dichlorodiphenyldichloroethene.svg|''p'',''p{{'}}''-DDE<br />(impurity)
File:P,p'-dichlorodiphenyldichloroethane.svg|''p'',''p{{'}}''-DDD<br />(impurity)
</gallery>

===Production and use===
DDT has been formulated in multiple forms, including [[Solution (chemistry)|solution]]s in [[xylene]] or [[petroleum]] [[Distillation|distillates]], [[Emulsion|emulsifiable]] [[concentrate]]s, water-[[wettable powder]]s, granules, [[aerosol]]s, [[Smoke bomb|smoke candles]] and charges for vaporizers and lotions.<ref name=EHC83>{{EHC-ref | id = 83 | name = DDT and Its Derivatives: Environmental Aspects | isbn = 9241542837 |date=1989 }}</ref>

From 1950 to 1980, DDT was extensively used in agriculture{{snd}}more than 40,000 [[tonnes]] each year worldwide<ref name="Geisz">{{cite journal | vauthors = Geisz HN, Dickhut RM, Cochran MA, Fraser WR, Ducklow HW | title = Melting glaciers: a probable source of DDT to the Antarctic marine ecosystem | journal = Environmental Science & Technology | volume = 42 | issue = 11 | pages = 3958–3962 | date = June 2008 | pmid = 18589951 | doi = 10.1021/es702919n | bibcode = 2008EnST...42.3958G | url = https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=1984&context=vimsarticles | access-date = August 26, 2020 | archive-date = August 29, 2022 | archive-url = https://web.archive.org/web/20220829055157/https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=1984&context=vimsarticles | url-status = live }}</ref>{{snd}}and it has been estimated that a total of 1.8 million tonnes have been produced globally since the 1940s.<ref name="ATSDRc5">[https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=81&tid=20 ''Toxicological Profile: for DDT, DDE, and DDE''] {{Webarchive|url=https://web.archive.org/web/20211125124535/https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=81&tid=20 |date=November 25, 2021 }}. [[Agency for Toxic Substances and Disease Registry]], September 2002.</ref> In the United States, it was manufactured by some 15 companies, including [[Monsanto]], [[Novartis|Ciba]],<ref>{{cite news|url=http://www.al.com/news/mobileregister/index.ssf?/base/news/1215162908145190.xml&coll=3|title=McIntosh residents file suit against Ciba|last=David|first=David|name-list-style=vanc|date=July 4, 2008|access-date=July 7, 2008|archive-url=https://web.archive.org/web/20090808020048/http://www.al.com/news/mobileregister/index.ssf?%2Fbase%2Fnews%2F1215162908145190.xml&coll=3|archive-date=August 8, 2009|url-status=dead|df=mdy-all}}</ref> [[Montrose Chemical Corporation of California|Montrose Chemical Company]], [[Arkema|Pennwalt]],<ref name="Oregon DEQ 2009">[http://www.deq.state.or.us/lq/ECSI/ecsidetail.asp?seqnbr=398 Environmental Cleanup Site Information Database for Arkema (former Pennwalt) facility] {{Webarchive|url=https://web.archive.org/web/20110723023510/http://www.deq.state.or.us/lq/ECSI/ecsidetail.asp?seqnbr=398 |date=July 23, 2011 }}, Oregon DEQ, April 2009.</ref> and [[Velsicol Chemical Corporation]].<ref>{{cite news |url=http://www.themorningsun.com/stories/012708/loc_tests.shtml| title=Tests shed light on how pCBSA got into St. Louis water |last=Horvath |first=Rosemary | name-list-style = vanc |date=January 27, 2008 |newspaper=Morning Sun |location=Michigan, United States |publisher=[[Journal Register Company]] |access-date=May 16, 2008 |archive-url=https://web.archive.org/web/20080705170443/http://www.themorningsun.com/stories/012708/loc_tests.shtml |archive-date=July 5, 2008 }}</ref> Production peaked in 1963 at 82,000 tonnes per year.<ref name=EHC009/> More than 600,000 tonnes (1.35 billion pounds) were applied in the US before the 1972 ban. Usage peaked in 1959 at about 36,000 tonnes.<ref name="EPA1975">[https://archive.epa.gov/epa/aboutepa/ddt-regulatory-history-brief-survey-1975.html "DDT Regulatory History: A Brief Survey (to 1975)"] {{Webarchive|url=https://web.archive.org/web/20161220162916/https://archive.epa.gov/epa/aboutepa/ddt-regulatory-history-brief-survey-1975.html |date=December 20, 2016 }}, U.S. EPA, July 1975.</ref>

China ceased production in 2007,<ref>{{cite web |url=http://chm.pops.int/Programmes/DDT/Meetings/DDTEG32010/tabid/1108/mctl/ViewDetails/EventModID/1421/EventID/116/xmid/4037/language/en-US/Default.aspx |title=Report of the Third Expert Group Meeting on DDT |publisher=UNEP/POPS/DDT-EG.3/3, Stockholm Convention on Persistent Organic Pollutants |date=November 12, 2010 |access-date=January 26, 2011 |archive-date=December 21, 2010 |archive-url=https://web.archive.org/web/20101221115754/http://chm.pops.int/Programmes/DDT/Meetings/DDTEG32010/tabid/1108/mctl/ViewDetails/EventModID/1421/EventID/116/xmid/4037/language/en-US/Default.aspx |url-status=live }}</ref> leaving India the only country still manufacturing DDT; it is the largest consumer.<ref name="DDTBP.1/2">{{cite web|url=http://www.pops.int/documents/ddt/Global%20status%20of%20DDT%20SSC%2020Oct08.pdf|title=Global status of DDT and its alternatives for use in vector control to prevent disease|last=van den Berg|first=Henk|name-list-style=vanc|date=October 23, 2008|publisher=[[Stockholm Convention on Persistent Organic Pollutants]]/[[United Nations Environment Programme]]|access-date=November 22, 2008|archive-url=https://web.archive.org/web/20101217022138/http://www.pops.int/documents/ddt/Global%20status%20of%20DDT%20SSC%2020Oct08.pdf|archive-date=December 17, 2010|url-status=dead|df=mdy-all}}</ref> In 2009, 3,314 tonnes were produced for malaria control and [[visceral leishmaniasis]].  In recent years, in addition to India, just seven other countries, all in Africa, are still using DDT.<ref>{{Cite web |date=September 13, 2017 |title=Alternatives to DDT |url=http://www.unep.org/topics/chemicals-and-pollution-action/pollution-and-health/persistent-organic-pollutants-pops-0 |access-date=2024-06-10 |website=UNEP - UN Environment Programme |language=en}}</ref>

===Mechanism of insecticide action===
In insects, DDT opens [[voltage-sensitive sodium channel|voltage-sensitive sodium ion channels]] in [[neuron]]s, causing them to fire spontaneously, which leads to spasms and eventual death.<ref name=":1">{{Cite journal|last=Dong|first=Ke|date=2007-01-06|title=Insect sodium channels and insecticide resistance|journal=Invertebrate Neuroscience |volume=7|issue=1|pages=17–30|doi=10.1007/s10158-006-0036-9|issn=1354-2516|pmc=3052376|pmid=17206406}}</ref> Insects with certain [[mutation]]s in their sodium channel [[gene]] are [[insecticide resistance|resistant]] to DDT and similar insecticides.<ref name=":1" /> DDT resistance is also conferred by up-regulation of genes expressing [[cytochrome P450]] in some insect species,<ref>{{cite journal | vauthors = Denholm I, Devine GJ, Williamson MS | title = Insecticide resistance on the move | journal = Science | volume = 297 | issue = 5590 | pages = 2222–2223 | date = September 2002 | pmid = 12351778 | doi = 10.1126/science.1077266 | s2cid = 83741532}}</ref> as greater quantities of some enzymes of this group accelerate the toxin's metabolism into inactive metabolites. Genomic studies in the model genetic organism ''[[Drosophila melanogaster]]'' revealed that high level DDT resistance is polygenic, involving multiple resistance mechanisms.<ref>{{cite journal | vauthors = Pedra JH, McIntyre LM, Scharf ME, Pittendrigh BR | title = Genome-wide transcription profile of field- and laboratory-selected dichlorodiphenyltrichloroethane (DDT)-resistant ''Drosophila'' | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 101 | issue = 18 | pages = 7034–7039 | date = May 2004 | pmid = 15118106 | pmc = 406461 | doi = 10.1073/pnas.0400580101 | bibcode = 2004PNAS..101.7034P | doi-access = free }}</ref> In the absence of genetic adaptation, Roberts and Andre 1994 find [[avoidance response|behavioral avoidance]] nonetheless provides insects with some protection against DDT.<ref name="Bijlsma-Loeschcke-2011">{{cite journal | title=Genetic erosion impedes adaptive responses to stressful environments | last1=Bijlsma | first1=R. | last2=Loeschcke | first2=Volker | journal=[[Evolutionary Applications]] | publisher=[[Blackwell Publishing|Blackwell]] | issn=1752-4571 | date=7 November 2011 | volume=5 | issue=2 | pages=117–129 | doi=10.1111/j.1752-4571.2011.00214.x | pmid=25568035 | pmc=3353342 | s2cid=18877551}}</ref> The [[M918T]] mutation event produces dramatic ''[[knockdown resistance|kdr]]'' for [[pyrethroid]]s but Usherwood et al. 2005 find it is entirely ineffective against DDT.<ref name="Scott-2019">{{cite journal | last=Scott | first=Jeffrey G. | title=Life and Death at the Voltage-Sensitive Sodium Channel: Evolution in Response to Insecticide Use | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=64 | issue=1 | date=2019-01-07 | issn=0066-4170 | doi=10.1146/annurev-ento-011118-112420 | pages=243–257| pmid=30629893 | s2cid=58667542 }}</ref> Scott 2019 believes this test in ''Drosophila'' [[oocyte]]s holds for oocytes in general.<ref name="Scott-2019" />