Template:Short description {{#invoke:other uses|otheruses}} Template:Use mdy dates Template:Chembox
Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound,<ref name=EHC009/> an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. DDT was first synthesized in 1874 by the Austrian chemist Othmar Zeidler. DDT's insecticidal action was discovered by the Swiss chemist Paul Hermann Müller in 1939. DDT was used in the second half of World War II to limit the spread of the insect-borne diseases malaria and typhus among civilians and troops. Müller was awarded the Nobel Prize in Physiology or Medicine in 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods".<ref name="nobel">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The WHO's anti-malaria campaign of the 1950s and 1960s relied heavily on DDT and the results were promising, though there was a resurgence in developing countries afterwards.<ref name="DDTBP.1/2"/><ref name="Feachem2007"/>
By October 1945, DDT was available for public sale in the United States. Although it was promoted by government and industry for use as an agricultural and household pesticide, there were also concerns about its use from the beginning.<ref name="Distillations"/> Opposition to DDT was focused by the 1962 publication of Rachel Carson's book Silent Spring. It talked about environmental impacts that correlated with the widespread use of DDT in agriculture in the United States, and it questioned the logic of broadcasting potentially dangerous chemicals into the environment with little prior investigation of their environmental and health effects. The book cited claims that DDT and other pesticides caused cancer and that their agricultural use was a threat to wildlife, particularly birds. Although Carson never directly called for an outright ban on the use of DDT, its publication was a seminal event for the environmental movement and resulted in a large public outcry that eventually led, in 1972, to a ban on DDT's agricultural use in the United States.<ref name="Lear">Template:Cite book</ref> Along with the passage of the Endangered Species Act, the United States ban on DDT is a major factor in the comeback of the bald eagle (the national bird of the United States) and the peregrine falcon from near-extinction in the contiguous United States.<ref name=Stokstad07>Template:Cite journal</ref><ref>United States Fish and Wildlife Service, Fact Sheet: Natural History, Ecology, and History of Recovery [1] Template:Webarchive</ref> DDT also caused a catastrophe in Borneo. It caused cats to die, making the rat population rapidly increase. These rats were infected with plague, causing a huge outbreak in the island [2]
The evolution of DDT resistance and the harm both to humans and the environment led many governments to curtail DDT use.<ref name=Chapin81/> A worldwide ban on agricultural use was formalized under the Stockholm Convention on Persistent Organic Pollutants, which has been in effect since 2004. Recognizing that total elimination in many malaria-prone countries is currently unfeasible in the absence of affordable/effective alternatives for disease control, the convention exempts public health use within World Health Organization (WHO) guidelines from the ban.<ref name="Stockholm"/>
DDT still has limited use in disease vector control because of its effectiveness in killing mosquitos and thus reducing malarial infections, but that use is controversial due to environmental and health concerns.<ref name="Larson">Template:Cite journal</ref><ref name=moyers>Template:Cite news</ref> DDT is one of many tools to fight malaria, which remains the primary public health challenge in many countries. WHO guidelines require that absence of DDT resistance must be confirmed before using it.<ref name="IRS-WHO"/> Resistance is largely due to agricultural use, in much greater quantities than required for disease prevention.<ref name="IRS-WHO"/>
Properties and chemistryEdit
DDT is similar in structure to the insecticide methoxychlor and the acaricide dicofol. It is highly hydrophobic and nearly insoluble in water but has good solubility in most organic solvents, fats and oils. DDT does not occur naturally and is synthesised by consecutive Friedel–Crafts reactions between chloral (Template:Chem) and two equivalents of chlorobenzene (Template:Chem), in the presence of an acidic catalyst.<ref name="ATSDRc5"/> DDT has been marketed under trade names including Anofex, Cezarex, Chlorophenothane, Dicophane, Dinocide, Gesarol, Guesapon, Guesarol, Gyron, Ixodex, Neocid, Neocidol and Zerdane; INN is clofenotane.<ref name=EHC009/>
Edit
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 patterns are formed. The major component (77%) is the desired p,pTemplate:' isomer. The o,pTemplate:' 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 metabolites and environmental breakdown products.<ref name=EHC009/> DDT, DDE and DDD are sometimes referred to collectively as DDX.<ref>Template:Cite journal</ref>
- Components of commercial DDT
- P,p'-dichlorodiphenyltrichloroethane.svg
p,pTemplate:'-DDT
(desired compound) - O,p'-dichlorodiphenyltrichloroethane.svg
o,pTemplate:'-DDT
(isomeric impurity) - P,p'-dichlorodiphenyldichloroethene.svg
p,pTemplate:'-DDE
(impurity) - P,p'-dichlorodiphenyldichloroethane.svg
p,pTemplate:'-DDD
(impurity)
Production and useEdit
DDT has been formulated in multiple forms, including solutions in xylene or petroleum distillates, emulsifiable concentrates, water-wettable powders, granules, aerosols, smoke candles and charges for vaporizers and lotions.<ref name=EHC83>Template:EHC-ref</ref>
From 1950 to 1980, DDT was extensively used in agricultureTemplate:Sndmore than 40,000 tonnes each year worldwide<ref name="Geisz">Template:Cite journal</ref>Template:Sndand it has been estimated that a total of 1.8 million tonnes have been produced globally since the 1940s.<ref name="ATSDRc5">Toxicological Profile: for DDT, DDE, and DDE Template:Webarchive. Agency for Toxic Substances and Disease Registry, September 2002.</ref> In the United States, it was manufactured by some 15 companies, including Monsanto, Ciba,<ref>Template:Cite news</ref> Montrose Chemical Company, Pennwalt,<ref name="Oregon DEQ 2009">Environmental Cleanup Site Information Database for Arkema (former Pennwalt) facility Template:Webarchive, Oregon DEQ, April 2009.</ref> and Velsicol Chemical Corporation.<ref>Template:Cite news</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">"DDT Regulatory History: A Brief Survey (to 1975)" Template:Webarchive, U.S. EPA, July 1975.</ref>
China ceased production in 2007,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> leaving India the only country still manufacturing DDT; it is the largest consumer.<ref name="DDTBP.1/2">{{#invoke:citation/CS1|citation |CitationClass=web }}</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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Mechanism of insecticide actionEdit
In insects, DDT opens voltage-sensitive sodium ion channels in neurons, causing them to fire spontaneously, which leads to spasms and eventual death.<ref name=":1">Template:Cite journal</ref> Insects with certain mutations in their sodium channel gene are 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>Template:Cite journal</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>Template:Cite journal</ref> In the absence of genetic adaptation, Roberts and Andre 1994 find behavioral avoidance nonetheless provides insects with some protection against DDT.<ref name="Bijlsma-Loeschcke-2011">Template:Cite journal</ref> The M918T mutation event produces dramatic kdr for pyrethroids but Usherwood et al. 2005 find it is entirely ineffective against DDT.<ref name="Scott-2019">Template:Cite journal</ref> Scott 2019 believes this test in Drosophila oocytes holds for oocytes in general.<ref name="Scott-2019" />
HistoryEdit
DDT was first synthesized in 1874 by Othmar Zeidler under the supervision of Adolf von Baeyer.<ref>Template:Cite journal On p. 1181, Zeidler called DDT dimonochlorphenyltrichloräthan.</ref><ref name="augustin">Template:Cite book</ref> It was further described in 1929 in a dissertation by W. Bausch and in two subsequent publications in 1930.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The insecticide properties of "multiple chlorinated aliphatic or fat-aromatic alcohols with at least one trichloromethane group" were described in a patent in 1934 by Wolfgang von Leuthold.<ref>Wolfgang von Leuthold, Schädlingsbekämpfung. DRP Nr 673246, April 27, 1934</ref> DDT's insecticidal properties were not, however, discovered until 1939 by the Swiss scientist Paul Hermann Müller, who was awarded the 1948 Nobel Prize in Physiology and Medicine for his efforts.<ref name=nobel/>
Use in the 1940s and 1950sEdit
.jpg){kind=link}
DDT is the best-known of several chlorine-containing pesticides used in the 1940s and 1950s. During this time, the use of DDT was driven by protecting American soldiers from diseases in tropical areas. Both British and American scientists hoped to use it to control spread of malaria, typhus, dysentery, and typhoid fever among overseas soldiers, especially considering that the pyrethrum was harder to access since it came mainly from Japan.<ref name="auto">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Due to the potency of DDT, it was not long before America's War Production Board placed it on military supply lists in 1942 and 1943 and encouraged its production for overseas use. Enthusiasm regarding DDT became obvious through the American government's advertising campaigns of posters depicting Americans fighting the Axis powers and insects and through media publications celebrating its military uses.<ref name="auto"/> In the South Pacific, it was sprayed aerially for malaria and dengue fever control with spectacular effects. While DDT's chemical and insecticidal properties were important factors in these victories, advances in application equipment coupled with competent organization and sufficient manpower were also crucial to the success of these programs.<ref name="Dunlap">Template:Cite book</ref>
In 1945, DDT was made available to farmers as an agricultural insecticide<ref name=EHC009/> and played a role in the elimination of malaria in Europe and North America.<ref name="Larson"/><ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Despite concerns emerging in the scientific community, and lack of research, the FDA considered it safe up to 7 parts per million in food. There was a large economic incentive to push DDT into the market and sell it to farmers, governments, and individuals to control diseases and increase food production.<ref name="auto"/>
DDT was also a way for American influence to reach abroad through DDT-spraying campaigns. In the 1944 issue of Life magazine there was a feature regarding the Italian program showing pictures of American public health officials in uniforms spraying DDT on Italian families.<ref name="auto"/>
In 1955, the World Health Organization commenced a program to eradicate malaria in countries with low to moderate transmission rates worldwide, relying largely on DDT for mosquito control and rapid diagnosis and treatment to reduce transmission.<ref>Template:Cite journal</ref> The program eliminated the disease in "North America, Europe, the former Soviet Union",<ref name="AmJTrop"/> and in "Taiwan, much of the Caribbean, the Balkans, parts of northern Africa, the northern region of Australia, and a large swath of the South Pacific"<ref name="Gladwell">Template:Cite news</ref> and dramatically reduced mortality in Sri Lanka and India.<ref name=Gordon/>
However, failure to sustain the program, increasing mosquito tolerance to DDT, and increasing parasite tolerance led to a resurgence. In many areas early successes partially or completely reversed, and in some cases rates of transmission increased.<ref name=Chapin81>Template:Cite journal</ref> The program succeeded in eliminating malaria only in areas with "high socio-economic status, well-organized healthcare systems, and relatively less intensive or seasonal malaria transmission".<ref name="AmJTrop">Template:Cite journal</ref>
DDT was less effective in tropical regions due to the continuous life cycle of mosquitoes and poor infrastructure. It was applied in sub-Saharan Africa by various colonial states, but the 'global' WHO eradication program didn't include the region.<ref>Template:Cite book</ref> Mortality rates in that area never declined to the same dramatic extent, and now constitute the bulk of malarial deaths worldwide, especially following the disease's resurgence as a result of resistance to drug treatments and the spread of the deadly malarial variant caused by Plasmodium falciparum. Eradication was abandoned in 1969 and attention instead focused on controlling and treating the disease. Spraying programs (especially using DDT) were curtailed due to concerns over safety and environmental effects, as well as problems in administrative, managerial and financial implementation.<ref name=Chapin81/> Efforts shifted from spraying to the use of bednets impregnated with insecticides and other interventions.<ref name="AmJTrop"/><ref name=Rogan05>Template:Cite journal</ref>
United States banEdit
By October 1945, DDT was available for public sale in the United States, used both as an agricultural pesticide and as a household insecticide.<ref name="Distillations"/> Although its use was promoted by government and the agricultural industry, US scientists such as FDA pharmacologist Herbert O. Calvery expressed concern over possible hazards associated with DDT as early as 1944.<ref name="Davis">Template:Cite book</ref><ref name=EPA1975/><ref name="Distillations"/> In 1947, Bradbury Robinson, a physician and nutritionist practicing in St. Louis, Michigan, warned of the dangers of using the pesticide DDT in agriculture. DDT had been researched and manufactured in St. Louis by the Michigan Chemical Corporation, later purchased by Velsicol Chemical Corporation,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and had become an important part of the local economy.<ref name= STLH>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Citing research performed by Michigan State University<ref>American Potato Journal, June 1947, volume 24, issue 6, pp. 183–187. Results of spraying and dusting potatoes in Michigan in 1946.</ref> in 1946, Robinson, a past president of the local Conservation Club,<ref>"Conservation Club, St. Louis, Has Program", Lansing State Journal (Lansing, Michigan), p. 14, March 2, 1931.</ref> opined that:
<templatestyles src="Template:Blockquote/styles.css" />
perhaps the greatest danger from D.D.T. is that its extensive use in farm areas is most likely to upset the natural balances, not only killing beneficial insects in great number but by bringing about the death of fish, birds, and other forms of wild life either by their feeding on insects killed by D.D.T. or directly by ingesting the poison.<ref>Template:Cite report</ref>{{#if:|{{#if:|}}
— {{#if:|, in }}Template:Comma separated entries}}
{{#invoke:Check for unknown parameters|check|unknown=Template:Main other|preview=Page using Template:Blockquote with unknown parameter "_VALUE_"|ignoreblank=y| 1 | 2 | 3 | 4 | 5 | author | by | char | character | cite | class | content | multiline | personquoted | publication | quote | quotesource | quotetext | sign | source | style | text | title | ts }}
As its production and use increased, public response was mixed. At the same time that DDT was hailed as part of the "world of tomorrow", concerns were expressed about its potential to kill harmless and beneficial insects (particularly pollinators), birds, fish, and eventually humans. The issue of toxicity was complicated, partly because DDT's effects varied from species to species, and partly because consecutive exposures could accumulate, causing damage comparable to large doses. A number of states attempted to regulate DDT.<ref name="Distillations">Template:Cite journal</ref><ref name=EHC009>Template:EHC-ref</ref> In the 1950s the federal government began tightening regulations governing its use.<ref name=EPA1975/> These events received little attention. Women like Dorothy Colson and Mamie Ella Plyler of Claxton, Georgia, gathered evidence about DDT's effects and wrote to the Georgia Department of Public Health, the National Health Council in New York City, and other organizations.<ref name="Conis">Template:Cite news</ref>
In 1957 The New York Times reported an unsuccessful struggle to restrict DDT use in Nassau County, New York, and the issue came to the attention of the popular naturalist-author Rachel Carson when a friend, Olga Huckins, wrote to her including an article she had written in the Boston Globe about the devastation of her local bird population after DDT spraying.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> William Shawn, editor of The New Yorker, urged her to write a piece on the subject, which developed into her 1962 book Silent Spring. The book argued that pesticides, including DDT, were poisoning both wildlife and the environment and were endangering human health.<ref name="Lear"/> Silent Spring was a best seller, and public reaction to it launched the modern environmental movement in the United States. The year after it appeared, President John F. Kennedy ordered his Science Advisory Committee to investigate Carson's claims. The committee's report "add[ed] up to a fairly thorough-going vindication of Rachel Carson's Silent Spring thesis", in the words of the journal Science,<ref>Template:Cite journal</ref> and recommended a phaseout of "persistent toxic pesticides".<ref name="Michaels2008">Template:Cite book</ref> In 1965, the U.S. military removed DDT from the military supply system due in part to the development of resistance by body lice to DDT; it was replaced by lindane.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
In the mid-1960s, DDT became a prime target of the burgeoning environmental movement, as concern about DDT and its effects began to rise in local communities. In 1966, a fish kill in Suffolk County, New York, was linked to a 5,000-gallon DDT dump by the county's mosquito commission, leading a group of scientists and lawyers to file a lawsuit to stop the county's further use of DDT.Template:R A year later, the group, led by Victor Yannacone and Charles Wurster, founded the Environmental Defense Fund (EDF), along with scientists Art Cooley and Dennis Puleston, and brought a string of lawsuits against DDT and other persistent pesticides in Michigan and Wisconsin.Template:R<ref>Template:Cite magazine</ref>
Around the same time, evidence was mounting further about DDT causing catastrophic declines in wildlife reproduction, especially in birds of prey like peregrine falcons, bald eagles, ospreys, and brown pelicans, whose eggshells became so thin that they often cracked before hatching.Template:R Toxicologists like David Peakall were measuring DDE levels in the eggs of peregrine falcons and California condors and finding that increased levels corresponded with thinner shells.<ref>Template:Cite journal</ref> Compounding the effect was DDT’s persistence in the environment, as it was unable to dissolve in water, and ended up accumulating in animal fat and disrupting hormone metabolism across a wide range of species.Template:R
In response to an EDF suit, the U.S. District Court of Appeals in 1971 ordered the EPA to begin the de-registration procedure for DDT. After an initial six-month review process, William Ruckelshaus, the Agency's first Administrator rejected an immediate suspension of DDT's registration, citing studies from the EPA's internal staff stating that DDT was not an imminent danger.<ref name=EPA1975/> However, these findings were criticized, as they were performed mostly by economic entomologists inherited from the United States Department of Agriculture, who many environmentalists felt were biased towards agribusiness and understated concerns about human health and wildlife. The decision thus created controversy.<ref name=Dunlap/>
The EPA held seven months of hearings in 1971–1972, with scientists giving evidence for and against DDT. In the summer of 1972, Ruckelshaus announced the cancellation of most uses of DDTTemplate:Snd exempting public health uses under some conditions.<ref name=EPA1975/> Again, this caused controversy. Immediately after the announcement, both the EDF and the DDT manufacturers filed suit against EPA. Many in the agricultural community were concerned that food production would be severely impacted, while proponents of pesticides warned of increased breakouts of insect-borne diseases and questioned the accuracy of giving animals high amounts of pesticides for cancer potential.<ref name=":0">Susan Wayland and Penelope Fenner-Crisp. "Reducing Pesticide Risks: A Half Century of Progress". Template:Webarchive. EPA Alumni Association. March 2016.</ref> Industry sought to overturn the ban, while the EDF wanted a comprehensive ban. The cases were consolidated, and in 1973 the United States Court of Appeals for the District of Columbia Circuit ruled that the EPA had acted properly in banning DDT.<ref name=EPA1975/> During the late 1970s, the EPA also began banning organochlorines, pesticides that were chemically similar to DDT. These included aldrin, dieldrin, chlordane, heptachlor, toxaphene, and mirex.<ref name=":0" />
Some uses of DDT continued under the public health exemption. For example, in June 1979, the California Department of Health Services was permitted to use DDT to suppress flea vectors of bubonic plague.<ref name="urlAEI – Short Publications – The Rise, Fall, Rise, and Imminent Fall of DDT">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> DDT continued to be produced in the United States for foreign markets until 1985, when over 300 tons were exported.<ref name="ATSDRc5"/>
International usage restrictionsEdit
In the 1970s and 1980s, agricultural use was banned in most developed countries, beginning with Hungary in 1968<ref name="Cheremisinoff-Rosenfeld-2011">Template:Cite book</ref><ref name="Nagy-Vajna-1972">Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Template:Ndash although in practice it continued to be used through at least 1970.<ref name="ag-use-stats-1979">Template:Cite book Template:OCLC. Template:OCLC. Template:ISBN. Template:OCLC. Template:OCLC. Template:OCLC.</ref> This was followed by Norway and Sweden in 1970, West Germany and the United States in 1972, but not in the United Kingdom until 1984.
In contrast to West Germany, in the German Democratic Republic DDT was used until 1988. Especially of relevance were large-scale applications in forestry in the years 1982–1984, with the aim to combat bark beetle and pine moth. As a consequence, DDT-concentrations in eastern German forest soils are still significantly higher compared to soils in the former western German states.<ref>Template:Cite journal</ref>
By 1991, total bans, including for disease control, were in place in at least 26 countries; for example, Cuba in 1970, the US in the 1980s, Singapore in 1984, Chile in 1985, and the Republic of Korea in 1986.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The Stockholm Convention on Persistent Organic Pollutants, which took effect in 2004, put a global ban on several persistent organic pollutants, and restricted DDT use to vector control. The convention was ratified by more than 170 countries. Recognizing that total elimination in many malaria-prone countries is currently unfeasible in the absence of affordable/effective alternatives, the convention exempts public health use within World Health Organization (WHO) guidelines from the ban.<ref name="Stockholm">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Resolution 60.18 of the World Health Assembly commits WHO to the Stockholm Convention's aim of reducing and ultimately eliminating DDT.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Malaria Foundation International states, "The outcome of the treaty is arguably better than the status quo going into the negotiations. For the first time, there is now an insecticide which is restricted to vector control only, meaning that the selection of resistant mosquitoes will be slower than before."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Despite the worldwide ban, agricultural use continued in India,<ref>Template:Cite news</ref> North Korea, and possibly elsewhere.<ref name="DDTBP.1/2"/> As of 2013, an estimated 3,000 to 4,000 tons of DDT were produced for disease vector control, including 2,786 tons in India.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> DDT is applied to the inside walls of homes to kill or repel mosquitoes. This intervention, called indoor residual spraying (IRS), greatly reduces environmental damage. It also reduces the incidence of DDT resistance.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> For comparison, treating Template:Convert of cotton during a typical U.S. growing season requires the same amount of chemical to treat roughly 1,700 homes.<ref name="Roberts 1997">Template:Cite journal</ref>
Environmental impactEdit
DDT is a persistent organic pollutant that is readily adsorbed to soils and sediments, which can act both as sinks and as long-term sources of exposure affecting organisms.<ref name=EHC83/> Depending on environmental conditions, its soil half-life can range from 22 days to 30 years. Routes of loss and degradation include runoff, volatilization, photolysis and aerobic and anaerobic biodegradation. Due to hydrophobic properties, in aquatic ecosystems DDT and its metabolites are absorbed by aquatic organisms and adsorbed on suspended particles, leaving little DDT dissolved in the water (however, its half-life in aquatic environments is listed by the National Pesticide Information Center as 150 years<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>). Its breakdown products and metabolites, DDE and DDD, are also persistent and have similar chemical and physical properties.<ref name="ATSDRc5"/> DDT and its breakdown products are transported from warmer areas to the Arctic by the phenomenon of global distillation, where they then accumulate in the region's food web.<ref>Template:Cite journal</ref>
Medical researchers in 1974 found a measurable and significant difference in the presence of DDT in human milk between mothers who lived in New Brunswick and mothers who lived in Nova Scotia, "possibly because of the wider use of insecticide sprays in the past".<ref>Template:Cite journal</ref>
Because of its lipophilic properties, DDT can bioaccumulate, especially in predatory birds.<ref>Template:Cite book</ref> DDT is toxic to a wide range of living organisms, including marine animals such as crayfish, daphnids, sea shrimp and many species of fish. DDT, DDE and DDD magnify through the food chain, with apex predators such as raptor birds concentrating more chemicals than other animals in the same environment. They are stored mainly in body fat. DDT and DDE are resistant to metabolism; in humans, their half-lives are 6 and up to 10 years, respectively. In the United States, these chemicals were detected in almost all human blood samples tested by the Centers for Disease Control in 2005, though their levels have sharply declined since most uses were banned.<ref name="PineRiver">Template:Cite journal</ref> Estimated dietary intake has declined,<ref name="PineRiver"/> although FDA food tests commonly detect it.<ref>USDA, Pesticide Data Program Annual Summary Calendar YearPesticide Data Program Annual Summary Calendar Year 2005, November 2006.</ref>
Despite being banned for many years, in 2018 research showed that DDT residues are still present in European soils and Spanish rivers.<ref name="Geissen">Template:Cite journal</ref><ref name="PAN-E">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Eggshell thinningTemplate:AnchorEdit
The chemical and its breakdown products DDE and DDD caused eggshell thinning and population declines in multiple North American and European bird of prey species.<ref name="ATSDRc5"/><ref>Template:Cite journal</ref><ref name=Stokstad07/><ref name="Lundholm, 1997"/><ref name=Tubbs2016>Template:Cite journal</ref><ref name="ibis">Template:Cite journal</ref> Both laboratory experiments and field studies confirmed this effect.<ref>Template:Cite news</ref> The effect was first conclusively proven at Bellow Island in Lake Michigan during University of Michigan-funded studies on American herring gulls in the mid-1960s.<ref name="mynorthscience">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> DDE-related eggshell thinning is considered a major reason for the decline of the bald eagle,<ref name=Stokstad07/> brown pelican,<ref>"Endangered and Threatened Wildlife and Plants; 12-Month Petition Finding and Proposed Rule To Remove the Brown Pelican (Pelecanus occidentalis) From the Federal List of Endangered and Threatened Wildlife; Proposed Rule", Fish and Wildlife Service, U.S. Department of the Interior, February 20, 2008. Template:Federal Register</ref> peregrine falcon and osprey.<ref name="ATSDRc5" /> However, birds vary in their sensitivity to these chemicals, with birds of prey, waterfowl and song birds being more susceptible than chickens and related species.<ref name="ATSDRc5"/><ref name="EHC83" /> Even in 2010, California condors that feed on sea lions at Big Sur that in turn feed in the Palos Verdes Shelf area of the Montrose Chemical Superfund site exhibited continued thin-shell problems,<ref>Template:Cite news</ref><ref>Template:Cite journal</ref> though DDT's role in the decline of the California condor is disputed.<ref name="ibis"/><ref name=Tubbs2016/>
The biological thinning mechanism is not entirely understood, but DDE appears to be more potent than DDT,<ref name="ATSDRc5"/> and strong evidence indicates that p,pTemplate:'-DDE inhibits calcium ATPase in the membrane of the shell gland and reduces the transport of calcium carbonate from blood into the eggshell gland. This results in a dose-dependent thickness reduction.<ref name="ATSDRc5"/><ref>Template:Cite book</ref><ref name="Guillette, 2006">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Lundholm, 1997">Template:Cite journal</ref> Other evidence indicates that o,p'-DDT disrupts female reproductive tract development, later impairing eggshell quality.<ref>Template:Cite journal</ref> Multiple mechanisms may be at work, or different mechanisms may operate in different species.<ref name="ATSDRc5"/>
Human healthEdit
DDT is an endocrine disruptor.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is considered likely to be a human carcinogen although the majority of studies suggest it is not directly genotoxic.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=NTP-DDT>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite book</ref> DDE acts as a weak androgen receptor antagonist, but not as an estrogen.<ref>Template:Cite journal</ref> p,pTemplate:'-DDT, DDT's main component, has little or no androgenic or estrogenic activity.<ref name="Cohn07">Template:Cite journal</ref> The minor component o,pTemplate:'-DDT has weak estrogenic activity.
Acute toxicityEdit
DDT is classified as "moderately toxic" by the U.S. National Toxicology Program (NTP) and "moderately hazardous" by WHO, based on the rat oral Template:LD50 of 113 mg/kg.<ref name = "zvgfrt">World Health Organization, The WHO Recommended Classification of Pesticides by Hazard Template:Webarchive, 2005.</ref> Indirect exposure is considered relatively non-toxic for humans.<ref name="Agarwal">Template:Cite journal</ref>
Chronic toxicityEdit
Primarily through the tendency for DDT to build up in areas of the body with high lipid content, chronic exposure can affect reproductive capabilities and the embryo or fetus.<ref name="Agarwal"/>
- A review article in The Lancet states: "research has shown that exposure to DDT at amounts that would be needed in malaria control might cause preterm birth and early weaning ... toxicological evidence shows endocrine-disrupting properties; human data also indicate possible disruption in semen quality, menstruation, gestational length, and duration of lactation".<ref name=Rogan05/>
- Other studies document decreases in semen quality among men with high exposures (generally from indoor residual spraying).<ref>Template:Cite journal</ref>
- Studies are inconsistent on whether high blood DDT or DDE levels increase time to pregnancy.<ref name="PineRiver"/> In mothers with high DDE blood serum levels, daughters may have up to a 32% increase in the probability of conceiving, but increased DDT levels have been associated with a 16% decrease in one study.<ref name="Eskenazi">Template:Cite journal</ref>
- Indirect exposure of mothers through workers directly in contact with DDT is associated with an increase in spontaneous abortions.<ref name="Agarwal"/>
- Other studies found that DDT or DDE interfere with proper thyroid function in pregnancy and childhood.<ref name="PineRiver"/><ref>Template:Cite journal</ref>
- Mothers with high levels of DDT circulating in their blood during pregnancy were found to be more likely to give birth to children who would go on to develop autism.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
CarcinogenicityEdit
In 2015, the International Agency for Research on Cancer classified DDT as Group 2A "probably carcinogenic to humans".<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Previous assessments by the U.S. National Toxicology Program classified it as "reasonably anticipated to be a carcinogen" and by the EPA classified DDT, DDE and DDD as class B2 "probable" carcinogens; these evaluations were based mainly on animal studies.<ref name="ATSDRc5"/><ref name=Rogan05/>
A 2005 Lancet review stated that occupational DDT exposure was associated with increased pancreatic cancer risk in 2 case control studies, but another study showed no DDE dose-effect association. Results regarding a possible association with liver cancer and biliary tract cancer are conflicting: workers who did not have direct occupational DDT contact showed increased risk. White men had an increased risk, but not white women or black men. Results about an association with multiple myeloma, prostate and testicular cancer, endometrial cancer and colorectal cancer have been inconclusive or generally do not support an association.<ref name=Rogan05/> A 2017 review of liver cancer studies concluded that "organochlorine pesticides, including DDT, may increase hepatocellular carcinoma risk".<ref>Template:Cite journal</ref>
A 2009 review, whose co-authors included persons engaged in DDT-related litigation, reached broadly similar conclusions, with an equivocal association with testicular cancer. Case–control studies did not support an association with leukemia or lymphoma.<ref name="PineRiver"/>
Breast cancerEdit
The question of whether DDT or DDE are risk factors in breast cancer has not been conclusively answered. Several meta analyses of observational studies have concluded that there is no overall relationship between DDT exposure and breast cancer risk.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The United States Institute of Medicine reviewed data on the association of breast cancer with DDT exposure in 2012 and concluded that a causative relationship could neither be proven nor disproven.<ref>Template:Cite journal</ref>
A 2007 case-control study<ref name="Cohn07"/> using archived blood samples found that breast cancer risk was increased 5-fold among women who were born prior to 1931 and who had high serum DDT levels in 1963. Reasoning that DDT use became widespread in 1945 and peaked around 1950, they concluded that the ages of 14–20 were a critical period in which DDT exposure leads to increased risk. This study, which suggests a connection between DDT exposure and breast cancer that would not be picked up by most studies, has received variable commentary in third-party reviews. One review suggested that "previous studies that measured exposure in older women may have missed the critical period".<ref name="PineRiver"/><ref>Template:Cite journal</ref> The National Toxicology Program notes that while the majority of studies have not found a relationship between DDT exposure and breast cancer that positive associations have been seen in a "few studies among women with higher levels of exposure and among certain subgroups of women".<ref name=NTP-DDT/>
A 2015 case control study identified a link (odds ratio 3.4) between in-utero exposure (as estimated from archived maternal blood samples) and breast cancer diagnosis in daughters. The findings "support classification of DDT as an endocrine disruptor, a predictor of breast cancer, and a marker of high risk".<ref>Template:Cite journal</ref>
Malaria controlTemplate:AnchorEdit
Malaria remains the primary public health challenge in many countries. In 2015, there were 214 million cases of malaria worldwide resulting in an estimated 438,000 deaths, 90% of which occurred in Africa.<ref name=WHO15>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> DDT is one of many tools to fight the disease. Its use in this context has been called everything from a "miracle weapon [that is] like Kryptonite to the mosquitoes",<ref name="salon">Template:Cite news</ref> to "toxic colonialism".<ref>Template:Cite journal</ref>
Before DDT, eliminating mosquito breeding grounds by drainage or poisoning with Paris green or pyrethrum was sometimes successful. In parts of the world with rising living standards, the elimination of malaria was often a collateral benefit of the introduction of window screens and improved sanitation.<ref name="Gladwell"/> A variety of usually simultaneous interventions represents best practice. These include antimalarial drugs to prevent or treat infection; improvements in public health infrastructure to diagnose, sequester and treat infected individuals; bednets and other methods intended to keep mosquitoes from biting humans; and vector control strategies<ref name="wmr09">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> such as larviciding with insecticides, ecological controls such as draining mosquito breeding grounds or introducing fish to eat larvae and indoor residual spraying (IRS) with insecticides, possibly including DDT. IRS involves the treatment of interior walls and ceilings with insecticides. It is particularly effective against mosquitoes, since many species rest on an indoor wall before or after feeding. DDT is one of 12 WHO–approved IRS insecticides.<ref name="AmJTrop"/>
The WHO's anti-malaria campaign of the 1950s and 1960s relied heavily on DDT and the results were promising, though temporary in developing countries. Experts tie malarial resurgence to multiple factors, including poor leadership, management and funding of malaria control programs; poverty; civil unrest; and increased irrigation. The evolution of resistance to first-generation drugs (e.g. chloroquine) and to insecticides exacerbated the situation.<ref name="DDTBP.1/2"/><ref name="Feachem2007">Template:Cite journal</ref> Resistance was largely fueled by unrestricted agricultural use. Resistance and the harm both to humans and the environment led many governments to curtail DDT use in vector control and agriculture.<ref name=Chapin81/> In 2006 WHO reversed a longstanding policy against DDT by recommending that it be used as an indoor pesticide in regions where malaria is a major problem.<ref>Template:Cite news</ref>
Once the mainstay of anti-malaria campaigns, as of 2019 only five countries used DDT for Indoor Residual Spraying <ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Initial effectivenessEdit
When it was introduced in World War II, DDT was effective in reducing malaria morbidity and mortality.<ref name=Dunlap/> WHO's anti-malaria campaign, which consisted mostly of spraying DDT and rapid treatment and diagnosis to break the transmission cycle, was initially successful as well. For example, in Sri Lanka, the program reduced cases from about one million per year before spraying to just 18 in 1963<ref>Template:Cite book</ref><ref>Template:Cite news</ref> and 29 in 1964. Thereafter the program was halted to save money and malaria rebounded to 600,000 cases in 1968 and the first quarter of 1969. The country resumed DDT vector control but the mosquitoes had evolved resistance in the interim, presumably because of continued agricultural use. The program switched to malathion, but despite initial successes, malaria continued its resurgence into the 1980s.<ref name="Gordon">Template:Cite book</ref><ref>Template:Cite journal</ref>
DDT remains on WHO's list of insecticides recommended for IRS. After the appointment of Arata Kochi as head of its anti-malaria division, WHO's policy shifted from recommending IRS only in areas of seasonal or episodic transmission of malaria, to advocating it in areas of continuous, intense transmission.<ref> {{#invoke:citation/CS1|citation |CitationClass=web }}</ref> WHO reaffirmed its commitment to phasing out DDT, aiming "to achieve a 30% cut in the application of DDT world-wide by 2014 and its total phase-out by the early 2020s if not sooner" while simultaneously combating malaria. WHO plans to implement alternatives to DDT to achieve this goal.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
South Africa continues to use DDT under WHO guidelines. In 1996, the country switched to alternative insecticides and malaria incidence increased dramatically. Returning to DDT and introducing new drugs brought malaria back under control.<ref>Template:Cite journal</ref> Malaria cases increased in South America after countries in that continent stopped using DDT. Research data showed a strong negative relationship between DDT residual house sprayings and malaria. In a research from 1993 to 1995, Ecuador increased its use of DDT and achieved a 61% reduction in malaria rates, while each of the other countries that gradually decreased its DDT use had large increases.<ref name="Roberts 1997"/><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Mosquito resistanceEdit
In some areas, resistance reduced DDT's effectiveness. WHO guidelines require that absence of resistance must be confirmed before using the chemical.<ref name="IRS-WHO">" Indoor Residual Spraying: Use of Indoor Residual Spraying for Scaling Up Global Malaria Control and Elimination Template:Webarchive". World Health Organization, 2006.</ref> Resistance is largely due to agricultural use, in much greater quantities than required for disease prevention.
Resistance was noted early in spray campaigns. Paul Russell, former head of the Allied Anti-Malaria campaign, observed in 1956 that "resistance has appeared after six or seven years".<ref name="Gladwell"/> Resistance has been detected in Sri Lanka, Pakistan, Turkey and Central America and it has largely been replaced by organophosphate or carbamate insecticides, e.g. malathion or bendiocarb.<ref name="Curtis">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
In many parts of India, DDT is ineffective.<ref>Template:Cite journal</ref> Agricultural uses were banned in 1989 and its anti-malarial use has been declining. Urban use ended.<ref>Template:Cite journal</ref> One study concluded that "DDT is still a viable insecticide in indoor residual spraying owing to its effectivity in well supervised spray operation and high excito-repellency factor."<ref name="mrc">Template:Cite journal</ref>
Studies of malaria-vector mosquitoes in KwaZulu-Natal Province, South Africa found susceptibility to 4% DDT (WHO's susceptibility standard), in 63% of the samples, compared to the average of 87% in the same species caught in the open. The authors concluded that "Finding DDT resistance in the vector An. arabiensis, close to the area where we previously reported pyrethroid-resistance in the vector An. funestus Giles, indicates an urgent need to develop a strategy of insecticide resistance management for the malaria control programmes of southern Africa."<ref name="Hargreaves">Template:Cite journal</ref>
DDT can still be effective against resistant mosquitoes<ref name=PLoS1/> and the avoidance of DDT-sprayed walls by mosquitoes is an additional benefit of the chemical.<ref name="mrc"/> For example, a 2007 study reported that resistant mosquitoes avoided treated huts. The researchers argued that DDT was the best pesticide for use in IRS (even though it did not afford the most protection from mosquitoes out of the three test chemicals) because the other pesticides worked primarily by killing or irritating mosquitoes – encouraging the development of resistance.<ref name="PLoS1">Template:Cite journal</ref> Others argue that the avoidance behavior slows eradication.<ref name="Musawenkosi">Template:Cite journal</ref> Unlike other insecticides such as pyrethroids, DDT requires long exposure to accumulate a lethal dose; however its irritant property shortens contact periods. "For these reasons, when comparisons have been made, better malaria control has generally been achieved with pyrethroids than with DDT."<ref name="Curtis"/> In India outdoor sleeping and night duties are common, implying that "the excito-repellent effect of DDT, often reported useful in other countries, actually promotes outdoor transmission".<ref>Template:Cite journal</ref>
Residents' concernsEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} IRS is effective if at least 80% of homes and barns in a residential area are sprayed.<ref name="IRS-WHO"/> Lower coverage rates can jeopardize program effectiveness. Many residents resist DDT spraying, objecting to the lingering smell, stains on walls, and the potential exacerbation of problems with other insect pests.<ref name="Curtis"/><ref name="Musawenkosi"/><ref name="Thurow">"In Malaria War, South Africa Turns To Pesticide Long Banned in the West" Template:Webarchive, Roger Thurow, The Wall Street Journal, July 26, 2001</ref> Pyrethroid insecticides (e.g. deltamethrin and lambda-cyhalothrin) can overcome some of these issues, increasing participation.<ref name="Curtis"/>
Human exposureEdit
A 1994 study found that South Africans living in sprayed homes have levels that are several orders of magnitude greater than others.<ref name="PineRiver"/> Breast milk from South African mothers contains high levels of DDT and DDE.<ref name="PineRiver"/> It is unclear to what extent these levels arise from home spraying vs food residues. Evidence indicates that these levels are associated with infant neurological abnormalities.<ref name="Curtis"/>
Most studies of DDT's human health effects have been conducted in developed countries where DDT is not used and exposure is relatively low.<ref name=Rogan05/><ref name="PineRiver"/><ref>Template:Cite news</ref>
Illegal diversion to agriculture is also a concern as it is difficult to prevent and its subsequent use on crops is uncontrolled. For example, DDT use is widespread in Indian agriculture,<ref>Template:Cite news</ref> particularly mango production<ref>Template:Cite journal</ref> and is reportedly used by librarians to protect books.<ref>Template:Cite news</ref> Other examples include Ethiopia, where DDT intended for malaria control is reportedly used in coffee production,<ref>Template:Cite journal</ref> and Ghana where it is used for fishing.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite news</ref> The residues in crops at levels unacceptable for export have been an important factor in bans in several tropical countries.<ref name="Curtis"/> Adding to this problem is a lack of skilled personnel and management.<ref name="Musawenkosi"/>
Criticism of restrictions on DDT useEdit
Restrictions on DDT usage have been criticized by some organizations opposed to the environmental movement, including Roger Bate of the pro-DDT advocacy group Africa Fighting Malaria and the libertarian think tank Competitive Enterprise Institute; these sources oppose restrictions on DDT and attribute large numbers of deaths to such restrictions, sometimes in the millions.<ref name="Crichton">Template:Cite news</ref><ref>Template:Cite book</ref><ref>Template:Cite journal</ref> These arguments were rejected as "outrageous" by former WHO scientist Socrates Litsios.<ref name="salon"/> May Berenbaum, University of Illinois entomologist, says, "to blame environmentalists who oppose DDT for more deaths than Hitler is worse than irresponsible".<ref name="salon"/> More recently, Michael Palmer, a professor of chemistry at the University of Waterloo, has pointed out that DDT is still used to prevent malaria, that its declining use is primarily due to increases in manufacturing costs, and that in Africa, efforts to control malaria have been regional or local, not comprehensive.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Template:Quote box
Criticisms of a DDT "ban" often specifically reference the 1972 United States ban (with the erroneous implication that this constituted a worldwide ban and prohibited use of DDT in vector control). Reference is often made to Silent Spring, even though Carson never pushed for a DDT ban. John Quiggin and Tim Lambert wrote, "the most striking feature of the claim against Carson is the ease with which it can be refuted".<ref name="quig">Template:Cite news</ref>
Investigative journalist Adam Sarvana and others characterize these notions as "myths" promoted principally by Roger Bate of the pro-DDT advocacy group Africa Fighting Malaria (AFM).<ref name="NRNS">Template:Cite news</ref><ref name="Guts">Template:Cite book. Relevant excerpt at Template:Cite magazine</ref>
AlternativesEdit
InsecticidesEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Organophosphate and carbamate insecticides, e.g. malathion and bendiocarb, respectively, are more expensive than DDT per kilogram and are applied at roughly the same dosage. Pyrethroids such as deltamethrin are also more expensive than DDT, but are applied more sparingly (0.02–0.3 g/m2 vs 1–2 g/m2), so the net cost per house per treatment is about the same.<ref name="AmJTrop"/> DDT has one of the longest residual efficacy periods of any IRS insecticide, lasting 6 to 12 months. Pyrethroids will remain active for only 4 to 6 months, and organophosphates and carbamates remain active for 2 to 6 months. In many malaria-endemic countries, malaria transmission occurs year-round, meaning that the high expense of conducting a spray campaign (including hiring spray operators, procuring insecticides, and conducting pre-spray outreach campaigns to encourage people to be home and to accept the intervention) will need to occur multiple times per year for these shorter-lasting insecticides.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
In 2019, the related compound difluorodiphenyltrichloroethane (DFDT) was described as a potentially more effective and therefore potentially safer alternative to DDT.<ref>Template:Cite journal</ref><ref name="NYT 17 October 2019">Template:Cite newsTemplate:Cbignore</ref>
Non-chemical vector controlEdit
Before DDT, malaria was successfully eliminated or curtailed in several tropical areas by removing or poisoning mosquito breeding grounds and larva habitats, for example by eliminating standing water. These methods have seen little application in Africa for more than half a century.<ref>Template:Cite journal</ref> According to CDC, such methods are not practical in Africa because "Anopheles gambiae, one of the primary vectors of malaria in Africa, breeds in numerous small pools of water that form due to rainfall ... It is difficult, if not impossible, to predict when and where the breeding sites will form, and to find and treat them before the adults emerge."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
The relative effectiveness of IRS versus other malaria control techniques (e.g. bednets or prompt access to anti-malarial drugs) varies and is dependent on local conditions.<ref name="AmJTrop"/>
A WHO study released in January 2008 found that mass distribution of insecticide-treated mosquito nets and artemisinin–based drugs cut malaria deaths in half in malaria-burdened Rwanda and Ethiopia. IRS with DDT did not play an important role in mortality reduction in these countries.<ref>"Impact of long-lasting insecticidal-treated nets (LLINs) and artemisinin-based combination therapies (ACTs) measured using surveillance data in four African countries". World Health Organization, January 31, 2008.</ref><ref>Malaria deaths halved in Rwanda and Ethiopia Better drugs, mosquito nets are the crucial tools Template:Webarchive, David Brown (Washington Post), SF Chronicle, A-12, February 1, 2008.</ref>
Vietnam has enjoyed declining malaria cases and a 97% mortality reduction after switching in 1991 from a poorly funded DDT-based campaign to a program based on prompt treatment, bednets and pyrethroid group insecticides.<ref>"World Health Organization, A story to be shared: The successful fight against malaria in Vietnam", November 6, 2000. Template:Webarchive</ref>
In Mexico, effective and affordable chemical and non-chemical strategies were so successful that the Mexican DDT manufacturing plant ceased production due to lack of demand.<ref name="PMC1119118">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
A review of fourteen studies in sub-Saharan Africa, covering insecticide-treated nets, residual spraying, chemoprophylaxis for children, chemoprophylaxis or intermittent treatment for pregnant women, a hypothetical vaccine and changing front–line drug treatment, found decision making limited by the lack of information on the costs and effects of many interventions, the small number of cost-effectiveness analyses, the lack of evidence on the costs and effects of packages of measures and the problems in generalizing or comparing studies that relate to specific settings and use different methodologies and outcome measures. The two cost-effectiveness estimates of DDT residual spraying examined were not found to provide an accurate estimate of the cost-effectiveness of DDT spraying; the resulting estimates may not be good predictors of cost-effectiveness in current programs.<ref>Template:Cite journal</ref>
However, a study in Thailand found the cost per malaria case prevented of DDT spraying (US$1.87) to be 21% greater than the cost per case prevented of lambda-cyhalothrin–treated nets (US$1.54),<ref>Template:Cite journal</ref> casting some doubt on the assumption that DDT was the most cost-effective measure. The director of Mexico's malaria control program found similar results, declaring that it was 25% cheaper for Mexico to spray a house with synthetic pyrethroids than with DDT.<ref name="PMC1119118"/> However, another study in South Africa found generally lower costs for DDT spraying than for impregnated nets.<ref>Template:Cite journal</ref>
A more comprehensive approach to measuring the cost-effectiveness or efficacy of malarial control would not only measure the cost in dollars, as well as the number of people saved, but would also consider ecological damage and negative human health impacts. One preliminary study found that it is likely that the detriment to human health approaches or exceeds the beneficial reductions in malarial cases, except perhaps in epidemics. It is similar to the earlier study regarding estimated theoretical infant mortality caused by DDT and subject to the criticism also mentioned earlier.<ref>Template:Cite journal</ref>
A study in the Solomon Islands found that "although impregnated bed nets cannot entirely replace DDT spraying without substantial increase in incidence, their use permits reduced DDT spraying".<ref>Template:Cite journal</ref>
A comparison of four successful programs against malaria in Brazil, India, Eritrea and Vietnam does not endorse any single strategy but instead states, "Common success factors included conducive country conditions, a targeted technical approach using a package of effective tools, data-driven decision-making, active leadership at all levels of government, involvement of communities, decentralized implementation and control of finances, skilled technical and managerial capacity at national and sub-national levels, hands-on technical and programmatic support from partner agencies, and sufficient and flexible financing."<ref>Template:Cite journal</ref>
DDT resistant mosquitoes may be susceptible to pyrethroids in some countries. However, pyrethroid resistance in Anopheles mosquitoes is on the rise with resistant mosquitoes found in multiple countries.<ref>Template:Cite journal</ref>
See alsoEdit
- DDT in New Zealand
- Operation Cat Drop
- Environmental hazard
- Index of pesticide articles
- Mosquito control
ReferencesEdit
Further readingEdit
- Berry-Cabán, Cristóbal S. "DDT and silent spring: fifty years after". Journal of Military and Veterans' Health 19 (2011): 19–24. online
- Conis, Elena. "Debating the health effects of DDT: Thomas Jukes, Charles Wurster, and the fate of an environmental pollutant". Public Health Reports 125.2 (2010): 337–342. online
- Davis, Frederick Rowe. "Pesticides and the perils of synecdoche in the history of science and environmental history". History of Science 57.4 (2019): 469–492. {{#invoke:doi|main}}
- "DDT Banning" in Richard L. Wilson, ed. Historical Encyclopedia of American Business, Vol I. Accounting Industry – Google, (Salem Press: 2009) p. 223 Template:ISBN. Template:OCLC
- Dunlap, Thomas, ed. DDT, Silent Spring, and the Rise of Environmentalism (University of Washington Press, 2008). Template:Oclc
- Dunlap, Thomas, ed. DDT, Silent Spring, and the Rise of Environmentalism: Classic texts (University of Washington Press, 2015). Template:ISBN. Template:OCLC
- Template:Cite journal
- Kinkela, David. DDT and the American Century: Global Health, Environmental Politics, and the Pesticide That Changed the World (University of North Carolina Press, 2011). Template:ISBN. Template:OCLC
- Morris, Peter J. T. (2019). "Chapter 9: A Tale of Two Nations: DDT in the United States and the United Kingdom". Hazardous Chemicals: Agents of Risk and Change, 1800–2000. Environment in History: International Perspectives 17. Berghahn Books. 294–327. {{#invoke:doi|main}} (book: {{#invoke:doi|main}}; Template:JSTOR).
External linksEdit
Template:Sister project Template:Sister project Template:External links
- Chemistry
- DDT at The Periodic Table of Videos (University of Nottingham)
- Toxicity
- {{#invoke:citation/CS1|citation
|CitationClass=web }}
- {{#invoke:citation/CS1|citation
|CitationClass=web }}
- Scorecard: The Pollution Information Site – DDT
- Interview with Barbara Cohn, PhD about DDT and breast cancer
- Pesticide residues in food 2000 : DDT
- Politics and DDT
- {{#invoke:citation/CS1|citation
|CitationClass=web }}
- Malaria and DDT
- Template:Cite news
- 'Andrew Spielman, Harvard School of Public Health, discusses environmentally friendly control of Malaria and uses of DDT Freeview video provided by the Vega Science Trust
- Template:Cite news
- DDT in popular culture
- Template:Skeptoid
- Phil Allegretti Pesticide Collection consisting of ephemera and 3-D objects, including cans, sprayers, and diffusers, related to DDT pesticide and insecticide in the United States in the mid-20th century (all images freely available for download in variety of formats from Science History Institute Digital Collections at digital.sciencehistory.org).
Template:Insecticides Template:Carcinogen Template:Consumer Food Safety Template:Androgen receptor modulators Template:Estrogen receptor modulators Template:Authority control