Chlorothalonil: Difference between revisions

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{{Short description|Fungicide}}
{{chembox
{{Use dmy dates|date=September 2020}}
| verifiedrevid = 329012094
{{Chembox
| Name = Chlorothalonil
| Verifiedfields = changed
| ImageFile = Chlorothalonil-2D-skeletal.png
| Watchedfields = changed
<!-- | ImageSize = 200px -->
| verifiedrevid = 407817485
| ImageName = Chlorothalonil
| Name = Chlorothalonil
| IUPACName = 2,4,5,6-tetrachloroisophthalonitrile
| ImageFile = Chlorothalonil Structural Formula V1.svg
| OtherNames =Bravo<br />Daconil<br/>tetrachloroisophthalonitrile
| ImageName = Chlorothalonil
| Section1 = {{Chembox Identifiers
| PIN = 2,4,5,6-Tetrachlorobenzene-1,3-dicarbonitrile
| ChemSpiderID = 13861400
| OtherNames = 2,4,5,6-Tetrachloroisophthalonitrile<br />Bravo<br />Daconil<br/>Tetrachloroisophthalonitrile<br />Celeste<br />Bronco<br />Agronil<br />Aminil
| SMILES = Clc1c(C#N)c(Cl)c(C#N)c(Cl)c1Cl
|Section1={{Chembox Identifiers
| StdInChI=1S/C8Cl4N2/c9-5-3(1-13)6(10)8(12)7(11)4(5)2-14
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| StdInChIKey = CRQQGFGUEAVUIL-UHFFFAOYSA-N
| ChemSpiderID = 13861400
| CASNo_Ref = {{cascite}}
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = J718M71A7A
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 3639
| SMILES = Clc1c(C#N)c(Cl)c(C#N)c(Cl)c1Cl
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C8Cl4N2/c9-5-3(1-13)6(10)8(12)7(11)4(5)2-14
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = CRQQGFGUEAVUIL-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 1897-45-6
| CASNo = 1897-45-6
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| RTECS = NT2600000
| ChEMBL = 468167
}}
| RTECS = NT2600000
| Section2 = {{Chembox Properties
| KEGG_Ref = {{keggcite|changed|kegg}}
|C=8|Cl=4|N=2
| KEGG = C11037
| MolarMass = 265.91 g mol<sup>−1</sup>
| PubChem = 15910
| Appearance = white crystalline solid
| EC_number = 217-588-1
| Density = 1.8 g cm<sup>−3</sup>, solid
| UNNumber = 3276, 2588
| Solubility = 0.06 g/100 ml
}}
| MeltingPt = 250 °C
|Section2={{Chembox Properties
| BoilingPt = 350 °C (760 mmHg)
| LogP = 2.88-3.86
| C=8 | Cl=4 | N=2
| Appearance = white crystalline solid
}}
| Density = 1.8 g&nbsp;cm<sup>−3</sup>, solid
| Section8 = {{Chembox Related
| Solubility = 10&nbsp;mg/100&nbsp;mL<ref>{{cite web |url=https://pubchem.ncbi.nlm.nih.gov/compound/chlorothalonil#section=Flash-Point |website=Pubchem |title=Chlorothalonil }}</ref>
| Function = [[nitrile]]s
| MeltingPtC = 250
| OtherFunctn = [[benzonitrile]]
| BoilingPtC = 350
| Function = [[organochloride]]s
| BoilingPt_notes = (760 mmHg)
| OtherFunctn = [[hexachlorobenzene]]<br />[[dichlorobenzene]]<br />[[chlorobenzene]]
| LogP = 2.88&ndash;3.86
}}
}}
|Section7={{Chembox Hazards
| GHSPictograms = {{GHS05}}{{GHS06}}{{GHS07}}{{GHS08}}{{GHS09}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|317|318|330|335|351|410}}
| PPhrases = {{P-phrases|201|202|260|261|271|272|273|280|281|284|302+352|304+340|305+351+338|308+313|310|312|320|321|333+313|363|391|403+233|405|501}}
}}
|Section8={{Chembox Related
| OtherFunction_label = [[nitrile]]s; [[organochloride]]s
| OtherFunction = [[benzonitrile]];<br/>[[hexachlorobenzene]], [[dichlorobenzene]], [[chlorobenzene]]
}}
}}
}}


'''Chlorothalonil''' (2,4,5,6-tetrachloroisophthalonitrile) is a [[polychlorinated aromatic]] mainly used as a [[broad spectrum]], non-systemic [[fungicide]], with other uses as a wood protectant, [[pesticide]], [[acaricide]], and to control [[mold]], [[mildew]], [[bacteria]], [[algae]].<ref name="EPA RED"/> Chlorothalonil-containing products are sold under the names Bravo, Echo, and Daconil. It was first registered for use in the [[United States of America|US]] in 1966. In 1997, the most recent year for which data is available, it was the third most used fungicide in the US, behind only [[sulfur]] and [[copper]], with some 12 million lbs used in agricultural alone that year.<ref>[http://www.ncfap.org/ncfap/nationalsummary1997.pdf PESTICIDE USE IN U.S. CROP PRODUCTION: 1997] National Center for Food and Agricultural Policy, 1997.</ref> Including non-agricultural uses, the [[United States Environmental Protection Agency|EPA]] estimates that on average almost 15 million lbs were used in annually from 1990-1996.<ref name="EPA RED">[http://www.epa.gov/oppsrrd1/REDs/0097red.pdf Reregistration Eligibility Decision for chlorothalonil], US EPA, 1999.</ref>
'''Chlorothalonil''' ('''2,4,5,6-tetrachloroisophthalonitrile''') is an [[organic compound]] mainly used as a [[broad spectrum]], nonsystemic [[fungicide]], with other uses as a wood protectant, [[pesticide]], [[acaricide]], and to control [[Mold (fungus)|mold]], [[mildew]], [[bacteria]], [[algae]].<ref name="EPA RED"/> Chlorothalonil-containing products are sold under the names Bravo, Echo, and Daconil. It was first registered for use in the [[United States of America|US]] in 1966. In 1997, the most recent year for which data are available, it was the third most used fungicide in the US, behind only [[sulfur]] and [[copper]], with {{convert|12|e6lb|e6kg|abbr=off}} used in agriculture that year.<ref>[http://www.ncfap.org/ncfap/nationalsummary1997.pdf PESTICIDE USE IN U.S. CROP PRODUCTION: 1997] {{webarchive|url=https://web.archive.org/web/20061210165927/http://www.ncfap.org/ncfap/nationalsummary1997.pdf |date=10 December 2006 }} National Center for Food and Agricultural Policy, 1997.</ref> Including nonagricultural uses, the [[United States Environmental Protection Agency]] (EPA) estimates, on average, almost {{convert|15|e6lb|e6kg|abbr=unit}} were used annually from 1990 to 1996.<ref name="EPA RED">[https://archive.epa.gov/pesticides/reregistration/web/pdf/0097red.pdf Reregistration Eligibility Decision for chlorothalonil], US EPA, 1999.</ref>


==Uses==
==Uses==
[[File:Chlorothalonil usage 2002.png|thumb|260px|left|Chlorothalonil use in the US in pounds per square mile in 2002 ([[USGS]] data)]]
In the US, chlorothalonil is used predominantly on [[peanuts]] (about 34% of US usage), [[potatoes]] (about 12%), and [[tomatoes]] (about 7%), though the EPA recognizes its use on many other crops.<ref name="EPA RED"/> It is also used on golf courses and lawns (about 10%) and as a preservative additive in some paints (about 13%), resins, emulsions, and coatings.<ref name="EPA RED"/>


In the US, chlorothalonil is used predominantly on [[peanut]]s (about 34% of usage), [[potato]]es (about 12%), and [[tomato]]es (about 7%), although the EPA recognizes its use on many other crops.<ref name="EPA RED"/> It is also used on golf courses and lawns (about 10%) and as a preservative additive in some paints (about 13%), resins, emulsions, and coatings.<ref name="EPA RED"/>
Chlorothalonil is commercially available in many different formulations and delivery methods. It is applied as a dust, dry or water-soluble grains, a wettable powder, a liquid spray, a fog, and a dip. It may be applied by hand, by ground sprayer, or by aircraft.<ref name="EPA RED"/>

Chlorothalonil is commercially available in many different formulations and delivery methods. It is applied as a dust, dry or water-soluble grains, a [[wettable powder]], a liquid spray, a fog, and a dip. It may be applied by hand, by ground sprayer, or by aircraft.<ref name="EPA RED"/>


==Mechanism of action==
==Mechanism of action==
Chlorothalonil reduces fungal intracellular [[glutathione]] molecules to alternate forms which cannot participate in essential [[enzyme|enzymatic]] reactions, ultimately leading to cell death, similar to the mechanism of [[trichloromethyl sulfenyl]].<ref name="tillman73">{{Citation
Chlorothalonil [[organic reduction reaction|reacts]] with [[glutathione]] giving an glutathione adduct with elimination of HCl. Its mechanism of action is similar to that of trichloromethyl sulfenyl fungicides<ref name="tillman73">{{Citation
| last = Tillman
| last1 = Tillman
| first = Ronald
| first1 = Ronald
| last2 = Siegel
| last2 = Siegel
| first2 = Malcom
| first2 = Malcolm
| last3 = Long
| last3 = Long
| first3 = John
| first3 = John
| title = Mechanism of action and fate of the fungicide chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) in biological systems : I. Reactions with cells and subcellular components of Saccharomyces pastorianus
| title = Mechanism of action and fate of the fungicide chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) in biological systems: I. Reactions with cells and subcellular components of ''Saccharomyces pastorianus''
| journal = Pesticide Biochemistry and Physiology
| journal = Pesticide Biochemistry and Physiology
| volume = 3
| volume = 3
| issue = 2
| issue = 2
| pages = 160–167
| pages = 160–167
| date = June, 1973
| date = June 1973
| year = 1973
| doi = 10.1016/0048-3575(73)90100-4
| doi = 10.1016/0048-3575(73)90100-4
}}</ref> such as [[captan]] and [[folpet]].<ref>{{cite journal |title= Reactions of certain trichloromethyl sulfenyl fungicides with low-molecular-weight thiols. ''In vivo'' studies with cells of ''Saccharomyces pastorianus'' |first= Malcolm R. |last= Siegel |journal= J. Agric. Food Chem. |year= 1970 |volume= 18 |issue= 5 |pages= 823–826 |doi= 10.1021/jf60171a034 |pmid= 5474238 }}</ref>
}}</ref>


==Toxicity==
==Toxicity==

===Acute===
===Acute===
According to the [[United States Environmental Protection Agency]], chlorothalonil is a [[Toxicity category rating|Toxicity Category I]] eye irritant, producing severe eye irritation. It is in [[Toxicity category rating|Toxicity Category II]], "moderately toxic," if inhaled (inhaled {{LD50}} 0.094 mg/L in rats.) For skin contact and ingestion, chlorothalonil is rated [[Toxicity category rating|Toxicity Category IV]], "practically non-toxic," meaning the oral and dermal {{LD50}} is greater than 10,000 mg/kg.<ref name="EPA RED"/>
According to the EPS, chlorothalonil is a [[Toxicity category rating|toxicity category I]] eye irritant, producing severe eye irritation. It is in toxicity category II, "moderately toxic", if inhaled (inhaled {{LD50}} 0.094&nbsp;mg/L in rats.) For skin contact and ingestion, chlorothalonil is rated toxicity category IV, "practically nontoxic", meaning the oral and dermal {{LD50}} is greater than 10,000&nbsp;mg/kg.<ref name="EPA RED"/>


===Chronic===
===Chronic===
Long term exposure to chlorothalonil resulted in [[kidney]] damage and tumors in animal tests.<ref name="EPA RED"/>
Long-term exposure to chlorothalonil resulted in [[kidney]] damage and tumors in animal tests.<ref name="EPA RED"/>


===Carcinogenic===
===Carcinogenic===
Chlorothalonil is a Group B2 "probable human [[carcinogen]]", based on observations of [[cancers]] and [[tumors]] of the kidneys and [[forestomach]] in laboratory animals fed diets containing chlorothalonil.<ref name="EPA RED"/>
Chlorothalonil is a Group 2B "'''possible''' human [[carcinogen]]" (N.B. : in the Group 2A of [[International Agency for Research on Cancer| International Agency for Research on Cancer IARC]] are the "'''probable''' human [[carcinogen]]" substances), based on observations of [[cancers]] and [[tumors]] of the kidneys and [[forestomach]]s in laboratory animals fed diets containing chlorothalonil.<ref name="EPA RED"/> To give context, the IARC evaluates Pickled vegetables (traditional Asian) as a Group 2B possible human carcinogen, and night shift work and drinking very hot beverages as Group 2A probable human carcinogen substances.


===Environmental===
===Environmental===
Chlorothalonil was found to be an important factor in the decline of the honey bee population, by making the bees more vulnerable to the gut parasite ''[[Nosema ceranae]]''.<ref>Jeffery S. Pettis, Elinor M. Lichtenberg, Michael Andree, Jennie Stitzinger, Robyn Rose,
Dennis vanEngelsdorp "Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen ''Nosema ceranae''" PLOS One, 24 July 2013, Online: 9 April 2014. [http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0070182]</ref>

Chlorothalonil is highly toxic to fish and aquatic invertebrates, but not toxic to birds.<ref name="WHO EHC">[http://www.inchem.org/documents/ehc/ehc/ehc183.htm Environmental Health Criteria 183], [[World Health Organization]], 1996.</ref>
Chlorothalonil is highly toxic to fish and aquatic invertebrates, but not toxic to birds.<ref name="WHO EHC">[http://www.inchem.org/documents/ehc/ehc/ehc183.htm Environmental Health Criteria 183], [[World Health Organization]], 1996.</ref>


At a concentration of 164&nbsp;μg/L, chlorothalonil was found to kill a species of frog within a 24-hour exposure.<ref>Taegan McMahon, Neal Halstead, Steve Johnson, Thomas R. Raffel, John M. Romansic, Patrick W. Crumrine, Raoul K. Boughton, Lynn B. Martin, Jason R. Rohr "The Fungicide Chlorothalonil is Nonlinearly Associated with Corticosterone Levels, Immunity, and Mortality in Amphibians" Environ Health Perspectives, 2011, Online: 4 April. {{doi|10.1289/ehp.1002956}}</ref>
Chlorothalonil has been suggested as a partial cause of [[Colony Collapse Disorder]], among many other factors.<ref name="Scientific American: Solving the Mystery of the Vanishing Bees">[http://www.sciam.com/article.cfm?id=saving-the-honeybee], [[Scientific American]]</ref>


===Contaminants===
===Contaminants===
Common chlorothalonil synthesis procedures frequently result in chlorothalonil contaminated with small amounts of [[hexachlorobenzene]], which is itself toxic. US regulations limit HCB in commercial production to 0.05% of chlorothalonil. According to the EPA report, "post-application exposure to HCB from chlorothalonil is not expected to be a concern based on the low level of HCB in chlorothalonil."<ref name="EPA RED"/>
Common chlorothalonil synthesis procedures frequently result in contamination of it with small amounts of [[hexachlorobenzene]] (HCB), which is toxic. US regulations limit HCB in commercial production to 0.05% of chlorothalonil. According to the EPA report, "post-application exposure to HCB from chlorothalonil is not expected to be a concern based on the low level of HCB in chlorothalonil. [[2,3,7,8-Tetrachlorodibenzodioxin]] being one of the most potent carcinogens known is also a known contaminant".<ref name="EPA RED"/>


==Environmental contamination==
==Environmental contamination==
Chlorothalonil has been detected in ambient air in [[Minnesota]]<ref>[http://www.panna.org/docsDrift/minnesotaDriftMap20071019.pdf Pesticides and Air Pollution in Minnesota: The Frequency of Detection of Chlorothalonil, a Fungicide Used on Potatoes.] Pesticide Action Network North America, Oct 2007.</ref> and [[Prince Edward Island]],<ref>{{Citation
Chlorothalonil has been detected in ambient air in [[Minnesota]]<ref>[http://www.panna.org/docsDrift/minnesotaDriftMap20071019.pdf Pesticides and Air Pollution in Minnesota: The Frequency of Detection of Chlorothalonil, a Fungicide Used on Potatoes.]{{dead link|date=August 2017 |bot=InternetArchiveBot |fix-attempted=yes }} Pesticide Action Network North America, Oct 2007.</ref> and [[Prince Edward Island]],<ref>{{cite journal |vauthors = White LM, Ernst WR, Julien G, Garron C, Leger M |title=Ambient air concentrations of pesticides used in potato cultivation in Prince Edward Island, Canada |journal=Pest Manag. Sci. |volume=62 |issue=2 |pages=126–36 |year=2006 |pmid=16358323 |doi=10.1002/ps.1130}}</ref> as well as in [[groundwater]] in [[Long Island, New York]]<ref name="EPA RED"/> and [[Florida]].<ref name="EPA RED"/> In the first three cases, the contamination is presumed to have come from potato farms. It has also been detected in several fish kills in [[Prince Edward Island]].<ref>{{Cite web|url=https://www.princeedwardisland.ca/sites/default/files/publications/fish_kill_statistic_1962-2016.pdf|title=Island Fish Kills from 1962 to 2016|website=Government of PEI|access-date=12 December 2016}}</ref>
| last = White
| first = Louise M
| last2 = ''et al.''
| first2 = WR
| title = Ambient air concentrations of pesticides used in potato cultivation in Prince Edward Island, Canada.
| journal = Pest Manag Sci
| volume = 62
| issue = 2
| pages = 126–136
| date =
| year = 2006
| url = http://www3.interscience.wiley.com/cgi-bin/abstract/112168257/ABSTRACT
| doi = 10.1002/ps.1130
| id =
| pmid = 16358323
| last3 = Julien
| first3 = G
| last4 = Garron
| first4 = C
| last5 = Leger
| first5 = M }}</ref> as well as in [[groundwater]] in [[Long Island, New York]]<ref name="EPA RED"/> and [[Florida]].<ref name="EPA RED"/> In the first three cases, the contamination is presumed to have come from potato farms.


The main breakdown product of chlorothalonil is hydroxy-2,5,6-trichloro-1,3-dicyanobenzene (SDS-3701). It has been shown to be 30 times more acutely toxic than chlorothalonil and more persistent in the environment.<ref>{{cite journal |last1=Arena |first1=Maria |last2=Auteri |first2=Domenica |last3=Barmaz |first3=Stefania |last4=Bellisai |first4=Giulia |last5=Brancato |first5=Alba |last6=Brocca |first6=Daniela |last7=Bura |first7=Laszlo |last8=Byers |first8=Harry |last9=Chiusolo |first9=Arianna |last10=Court Marques |first10=Daniele |last11=Crivellente |first11=Federica |last12=De Lentdecker |first12=Chloe |last13=Egsmose |first13=Mark |last14=Erdos |first14=Zoltan |last15=Fait |first15=Gabriella |last16=Ferreira |first16=Lucien |last17=Goumenou |first17=Marina |last18=Greco |first18=Luna |last19=Ippolito |first19=Alessio |last20=Istace |first20=Frederique |last21=Jarrah |first21=Samira |last22=Kardassi |first22=Dimitra |last23=Leuschner |first23=Renata |last24=Lythgo |first24=Christopher |last25=Magrans |first25=Jose Oriol |last26=Medina |first26=Paula |last27=Miron |first27=Ileana |last28=Molnar |first28=Tunde |last29=Nougadere |first29=Alexandre |last30=Padovani |first30=Laura |last31=Parra Morte |first31=Juan Manuel |last32=Pedersen |first32=Ragnor |last33=Reich |first33=Hermine |last34=Sacchi |first34=Angela |last35=Santos |first35=Miguel |last36=Serafimova |first36=Rositsa |last37=Sharp |first37=Rachel |last38=Stanek |first38=Alois |last39=Streissl |first39=Franz |last40=Sturma |first40=Juergen |last41=Szentes |first41=Csaba |last42=Tarazona |first42=Jose |last43=Terron |first43=Andrea |last44=Theobald |first44=Anne |last45=Vagenende |first45=Benedicte |last46=Verani |first46=Alessia |last47=Villamar‐Bouza |first47=Laura |title=Peer review of the pesticide risk assessment of the active substance chlorothalonil |journal=EFSA Journal |date=January 2018 |volume=16 |issue=1 |pages=e05126 |doi=10.2903/j.efsa.2018.5126|pmid=32625673 |pmc=7009683 |doi-access=free }}</ref><ref name="cox97">{{Citation
The main breakdown product of chlorothalonil is SDS-3701 (4-hydroxy-2,5,6-trichloroisophthalonitrile). It has been shown to be 30 times more acutley toxic than chlorothalonil and more persistent in the environment.<ref name="cox97">{{Citation
| last = Cox
|last = Cox
| first = Caroline
|first = Caroline
| title = Fungicide Factsheet: Chlorothalonil
|title = Fungicide Factsheet: Chlorothalonil
| journal = Journal of Pesticide Reform
|journal = Journal of Pesticide Reform
| volume = 17
|volume = 17
| issue = 4
|issue = 4
| pages = 14–20
|pages = 14–20
| date =
|year = 1997
|url = http://www.pesticide.org/get-the-facts/pesticide-factsheets/factsheets/chlorothalonil
| year = 1997
| url = http://www.pesticide.org/get-the-facts/pesticide-factsheets/factsheets/chlorothalonil
|archive-url = https://web.archive.org/web/20101110064601/http://www.pesticide.org/get-the-facts/pesticide-factsheets/factsheets/chlorothalonil
|archive-date = 10 November 2010}}</ref> Laboratory experiments have shown it can thin the eggshells of birds, but no evidence supports this happening in the environment.<ref name = "EPA RED"/>
| doi =
| id = }}</ref> Laboratory experiments have shown that it can thin the eggshells of birds, but there is no evidence that this is happening in the environment.<ref name = "EPA RED"/>


In 2019, a review of the evidence found that "a high risk to amphibians and fish was identified for all representative uses", and that chlorothalonil breakdown products may cause DNA damage.<ref name="Carrington 2019">{{cite web | last=Carrington | first=Damian | title=EU bans UK's most-used pesticide over health and environment fears | website=The Guardian | date=2019-03-29 | url=http://www.theguardian.com/environment/2019/mar/29/eu-bans-widely-used-pesticide-over-safety-concerns | access-date=2019-03-29}}</ref><ref>{{Cite web | url=https://www.farminguk.com/news/European-Commission-votes-to-ban-fungicide-Chlorothalonil_51641.html | title=European Commission votes to ban fungicide Chlorothalonil}}</ref> Around the same time, research indicated chlorothalonil and other fungicides to be the strongest factor in bumblebee population decline.<ref name="Carrington 2019"/>
==Chemistry==
Chlorothalonil can by produced by the direct chlorination of isophthalonitrile or by treating tetrachloroisophthaloyl amide with [[phosphoryl chloride]]. It breaks down under basic conditions but is stable in neutral and acidic media.<ref name="WHO EHC"/> Technical chlorothalonil contains traces of [[Dioxins and dioxin-like compounds|dioxins]] and [[hexachlorobenzene]],<ref name="EPA RED"/> a [[persistent organic pollutant]] banned under the [[Stockholm Convention]].


<gallery class="center" caption="Important metabolites of chlorothalonil">
[[Image:Chlorothalonil usage 2002 USGS.png|thumb|260px|right|Chlorothalonil use in the US in pounds per square mile in 2002. Source: [[USGS]]]]
File:2,4,5-trichloro-6-hydroxyisophthalonitrile.svg|2,4,5-trichloro-6-hydroxy&shy;isophthalonitrile (SDS-3701)
File:R417888.svg|Chlorothalonil sulfonic acid (R417888)
File:R471811.svg|R471811
</gallery>

===Gag order===
Syngenta sued to stop communication by Swiss health authorities with the Swiss public regarding the "relevance" of specific metabolites of chlorothalonil that Swiss authorities detected in high concentrations in the groundwater from which hundreds of thousands of Swiss people obtain drinking water. The court banned Swiss health authorities from communicating with the public about the dangers posed by some of the metabolites.<ref>Le Monde, 27 Sept. 2022 [https://www.lemonde.fr/en/environment/article/2022/09/27/by-products-of-pesticide-banned-in-2019-found-in-swiss-drinking-water_5998346_114.html "By-Products of Pesticide Banned in 2019 Found in Swiss Drinking Water, Syngenta, The Producer of The Fungicide Chlorothalonil, Has Sued Swiss Health Authorities for Making Public The Danger Posed by Certain Derivatives of The Pesticide,"]</ref>

===Bans===
In March 2019, as a result of the previously mentioned research, the European Union banned the use of chlorothalonil<ref name="Carrington 2019"/> dated to take effect May 20, 2020.<ref name="NFU-Eng-Wal" /> Switzerland followed in December 2019.<ref>{{cite news |title=Swiss ban widely-used pesticide over health and environment fears |url=https://www.swissinfo.ch/eng/chlorothalonil_swiss-ban-widely-used-pesticide-over-health-and-environment-fears/45429716 |access-date=12 December 2019 |work=[[swissinfo]] |language=en}}</ref>

== Removal ==
The removal of chlorothalonil and its metabolites is usually achieved by very expensive, technically complex and unecological methods such as reverse osmosis, nano- or microfiltration. In addition, dilution is achieved by mixing with uncontaminated water. However, this only reduces the concentration, the substances still remain in the water. In technologies based on membrane technology, the membranes must be cleaned regularly with chemicals, which is expensive and not ecological.

Recent research results from a Swiss company show very good results for the removal of chlorothalonil and its metabolites. In contrast to the conclusion described in the Eawag fact-sheet, it was also possible to remove the metabolites R471811 and chlorothalonil sulfonic acid from water using a filter material based on activated carbon. The first measurements did not even reach the detection limit. Thus, it was shown that it is possible to completely remove the pesticide residues.<ref>{{Cite web|title=BioGreen P|url=https://www.uwiag.com/biogreenp|access-date=2021-03-23|website=United Waters Int.|language=en}}</ref>

==Production==
Chlorothalonil can be produced by the direct chlorination of [[isophthalonitrile]] or by dehydration of tetrachloroisophthaloyl amide with [[phosphoryl chloride]].<ref>{{Ullmann |author=Franz Müller |author2=Peter Ackermann |author3=Paul Margot |title=Fungicides, Agricultural, 2. Individual Fungicides|doi=10.1002/14356007.o12_o06}}</ref> It is a white solid. It breaks down under basic conditions, but is stable in neutral and acidic media.<ref name="WHO EHC"/> Technical grade chlorothalonil contains traces of [[Dioxins and dioxin-like compounds|dioxins]] and [[hexachlorobenzene]],<ref name="EPA RED"/> a [[persistent organic pollutant]] banned under the [[Stockholm Convention]].


==References==
==References==
{{reflist}}
{{reflist|refs=

<ref name="NFU-Eng-Wal">{{cite web | author=[[National Farmers' Union of England and Wales]] | title=Chlorothalonil use-by date approaching | website=NFU Online | url=http://www.nfuonline.com:443/sectors/crops/crops-news/chlorothalonil-use-by-date-approaching/ | access-date=2021-03-16}}</ref>

}}


==External links==
==External links==
*[http://pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC34550 Pesticideinfo.org: Chlorothalonil]
*[http://extoxnet.orst.edu/pips/chloroth.htm Extension Toxicology Network: Chlorothalonil Pesticide Information Profile]
*[http://extoxnet.orst.edu/pips/chloroth.htm Extension Toxicology Network: Chlorothalonil Pesticide Information Profile]
*{{PPDB|150}}
*{{cite web | title=2017 Pesticide Use Maps - Low | website=Water Resources | publisher=[[United States Geological Survey]] | url=http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2017&map=CHLOROTHALONIL&hilo=L | access-date=2021-03-16}}
*{{cite web | title=2017 Pesticide Use Maps - High | website=Water Resources | publisher=[[United States Geological Survey]] | url=http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=2017&map=CHLOROTHALONIL&hilo=H | access-date=2021-03-16}}


{{Authority control}}


[[Category:Fungicides]]
[[Category:Fungicides]]
[[Category:Nitriles]]
[[Category:Nitriles]]
[[Category:Organochlorides]]
[[Category:Chloroarenes]]
[[Category:IARC Group 2B carcinogens]]
[[Category:IARC Group 2B carcinogens]]

[[de:Chlorthalonil]]
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[[nl:Chloorthalonil]]
[[ja:クロロタロニル]]
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