Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Nitrogen dioxide: Difference between pages

{{short description|Chemical compound with formula NO₂}}

{{Hatnote|Not to be confused with [[nitric oxide]] (formula {{chem2|NO}}), [[nitrous oxide]] ({{chem2|N2O}}), or generic nitrogen oxide pollutants [[NOx]].}}

{{Redirect|NO2}}

| Verifiedfields = changed

| verifiedrevid = 464361763

| ImageFileL1 = Nitrogen-dioxide-2D-dimensions-vector.svg

| ImageNameL1 = Skeletal formula of nitrogen dioxide with some measurementsEP

| ImageFile2 = Nitrogen dioxide at different temperatures.jpg

| ImageSize2 = 240

| ImageCaption2 =

{{chem|NO|2}} converts to the colorless [[dinitrogen tetroxide]] ({{chem|N|2|O|4}}) at low temperatures and reverts to {{chem|NO|2}} at higher temperatures.

| ImageName2 = Nitrogen dioxide at different temperatures

| IUPACName = Nitrogen dioxide

| OtherNames = Nitrogen(IV) oxide,<ref name="nitrogen dioxide (CHEBI:33101)">{{Cite web |title = nitrogen dioxide (CHEBI:33101) |url = https://www.ebi.ac.uk/chebi/searchId.do?chebiId=33101 |work = Chemical Entities of Biological Interest (ChEBI) |publisher = European Bioinformatics Institute |access-date = 4 October 2011 |location = UK |date = 13 January 2008 |at = Main |archive-url = https://web.archive.org/web/20160304055311/https://www.ebi.ac.uk/chebi/searchId.do?chebiId=33101 |archive-date = 4 March 2016 }}</ref> deutoxide of nitrogen

|Section1={{Chembox Identifiers

| CASNo = 10102-44-0

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|changed|FDA}}

| UNII = S7G510RUBH

| PubChem = 3032552

| ChemSpiderID = 2297499

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| EINECS = 233-272-6

| UNNumber = 1067

| ChEBI = 33101

| ChEBI_Ref = {{ebicite|correct|EBI}}

| RTECS = QW9800000

| Gmelin = 976

| SMILES = N(=O)[O]

| SMILES2 = [N+](=O)[O-]

| StdInChI = 1S/NO2/c2-1-3

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| InChI = 1/NO2/c2-1-3

| StdInChIKey = JCXJVPUVTGWSNB-UHFFFAOYSA-N

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| InChIKey = JCXJVPUVTGWSNB-UHFFFAOYAA

|Section2={{Chembox Properties

| Formula = NO{{su|b=2|p=•}}

| N = 1 | O = 2

| Appearance = Brown gas<ref name="crc" />

| Odor = Chlorine-like

| Density = 1.880{{nbsp}}g/L<ref name="crc">Haynes, 4.79.</ref>

| MeltingPtC = −9.3

| MeltingPt_ref=<ref name="crc" />

| BoilingPtC = 21.15

| BoilingPt_ref=<ref name="crc" />

| Solubility = Hydrolyses

| SolubleOther = Soluble in [[carbon tetrachloride|{{chem|CCl|4}}]], [[nitric acid]],<ref>{{Cite journal | last1 = Mendiara | first1 = S. N. | last2 = Sagedahl | first2 = A. | last3 = Perissinotti | first3 = L. J. | title = An electron paramagnetic resonance study of nitrogen dioxide dissolved in water, carbon tetrachloride and some organic compounds | doi = 10.1007/BF03162326 | journal = Applied Magnetic Resonance | volume = 20 | issue = 1–2 | pages = 275–287 | year = 2001 | s2cid = 97875925 }}</ref> [[chloroform]]

| VaporPressure = 98.80{{nbsp}}kPa (at 20&nbsp;°C)

| RefractIndex = 1.449 (at 20&nbsp;°C)

| MagSus = +150.0·10⁻⁶{{nbsp}}cm³/mol<ref>Haynes, 4.134.</ref>

|Section3={{Chembox Structure

| MolShape = Bent

| PointGroup = C_2v

|Section4={{Chembox Thermochemistry

| Thermochemistry_ref =<ref>Haynes, 5.16.</ref>

| DeltaHf = +33.2&nbsp;kJ/mol

| Entropy = 240.1&nbsp;J/(mol·K)

| HeatCapacity = 37.2&nbsp;J/(mol·K)

}}

|Section5={{Chembox Hazards

| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0930.htm ICSC 0930]

| GHSPictograms = {{GHS03}} {{GHS05}} {{GHS06}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|270|314|330}}

| PPhrases = {{P-phrases|220|260|280|284|305+351+338|310}}

| MainHazards = Poison, oxidizer

| NFPA-H = 4

| NFPA-F = 0

| NFPA-R = 0

| NFPA-S = OX

| PEL = C 5{{nbsp}}ppm (9{{nbsp}}mg/m³)<ref name="PGCH">{{PGCH|0454|Nitrogen dioxide}}</ref>

| REL = ST 1{{nbsp}}ppm (1.8{{nbsp}}mg/m³)<ref name="PGCH" />

| IDLH = 13{{nbsp}}ppm<ref name="PGCH" />

| LC50 = 30{{nbsp}}ppm (guinea pig, 1&nbsp;[[hour|h]])<br />315{{nbsp}}ppm (rabbit, 15&nbsp;min)<br />68{{nbsp}}ppm (rat, 4&nbsp;h)<br />138{{nbsp}}ppm (rat, 30&nbsp;min)<br />1000{{nbsp}}ppm (mouse, 10&nbsp;min)<ref name="IDLH">{{IDLH|10102440|Nitrogen dioxide}}</ref>

| LCLo = 64{{nbsp}}ppm (dog, 8&nbsp;h)<br />64{{nbsp}}ppm (monkey, 8&nbsp;h)<ref name="IDLH" />

|Section8={{Chembox Related

| OtherFunction_label = [[nitrogen oxide]]s

| OtherFunction = [[Dinitrogen pentoxide]]<br />

| OtherCompounds = [[Chlorine dioxide]] <br /> [[Carbon dioxide]]

'''Nitrogen dioxide''' is a [[chemical compound]] with the formula {{chem2|NO2}}. One of several [[nitrogen oxide]]s, nitrogen dioxide is a reddish-brown gas. It is a [[paramagnetic]], bent molecule with C_2v [[molecular symmetry|point group symmetry]]. Industrially, {{chem2|NO2}} is an intermediate in the synthesis of [[nitric acid]], millions of tons of which are produced each year, primarily for the production of [[fertilizer]]s.

Nitrogen dioxide is poisonous and can be fatal if inhaled in large quantities.<ref name="EPAmain">{{EPA content|title=Nitrogen dioxide |url=http://www.epa.gov/airquality/nitrogenoxides/ |publisher=United States Environmental Protection Agency |date=Feb 23, 2016}}</ref> Cooking with a [[gas stove]] produces nitrogen dioxide which causes poorer [[indoor air quality]]. Combustion of gas can lead to increased concentrations of nitrogen dioxide throughout the home environment which is linked to [[Respiratory disease|respiratory issues and diseases]].<ref name=":0">{{Cite web |date=8 November 2023 |title=Clearing the Air: Gas Cooking and Pollution in European Homes |url=https://www.clasp.ngo/research/all/cooking-with-gas-findings-from-a-pan-european-indoor-air-quality-field-study/ |access-date=2024-05-05 |website=CLASP |language=en}}</ref><ref name=":2">{{Cite web |last1=Seals |first1=Brady |last2=Krasner |first2=Andee |title=Gas Stoves: Health and Air Quality Impacts and Solutions |url=https://rmi.org/insight/gas-stoves-pollution-health/ |access-date=2024-05-05 |website=RMI |language=en-US}}</ref> The LC₅₀ ([[median lethal dose]]) for humans has been estimated to be 174 ppm for a 1-hour exposure.<ref name="NIOSH">{{cite web |title=Immediately Dangerous to Life or Health Concentrations (IDLH): Nitrogen dioxide|url=https://www.cdc.gov/niosh/idlh/10102440.html |publisher=The National Institute for Occupational Safety and Health (NIOSH) |date=May 1994 |access-date=October 20, 2023}}</ref> It is also included in the [[NOx|NO_<var>x</var>]] family of [[air pollution|atmospheric pollutants]].

==Properties ==

Nitrogen dioxide is a reddish-brown gas with a pungent, acrid odor above {{convert|21.2|C|F K}} and becomes a yellowish-brown liquid below {{convert|21.2|C|F K}}. It forms an [[Chemical equilibrium|equilibrium]] with its [[Dimer (chemistry)|dimer]], [[dinitrogen tetroxide]] ({{chem2|N2O4}}), and converts almost entirely to {{chem2|N2O4}} below {{convert|-11.2|C|F K}}.<ref name="PGCH" />

The [[chemical bond|bond]] length between the [[nitrogen]] atom and the oxygen atom is 119.7&nbsp;[[picometre|pm]]. This bond length is consistent with a [[bond order]] between one and two.

Unlike [[ozone]] ({{chem2|O3}}) the [[ground state|ground]] [[electronic state]] of nitrogen dioxide is a [[doublet state]], since nitrogen has one unpaired electron,<ref name="G&E">{{Greenwood&Earnshaw2nd|page=455-7}}</ref> which decreases the [[alpha effect]] compared with [[nitrite]] and creates a weak bonding interaction with the oxygen lone pairs. The lone electron in {{chem2|NO2}} also means that this compound is a [[radical (chemistry)|free radical]], so the formula for nitrogen dioxide is often written as {{chem2|^{•}NO2}}.

The reddish-brown color is a consequence of preferential absorption of light in the blue region of the spectrum (400–500&nbsp;nm), although the absorption extends throughout the visible (at shorter wavelengths) and into the infrared (at longer wavelengths). Absorption of light at wavelengths shorter than about 400&nbsp;nm results in photolysis (to form {{chem2|NO + O}}, atomic oxygen); in the atmosphere the addition of the oxygen atom so formed to {{chem2|O2}} results in ozone.

==Preparation==

{{See also|Ostwald process}}

Industrially, nitrogen dioxide is produced and transported as its cryogenic liquid dimer, [[dinitrogen tetroxide]]. It is produced industrially by the oxidation of ammonia, the [[Ostwald Process]]. This reaction is the first step in the production of nitric acid:<ref name=Ull/>

:{{chem2|4 NH3 + 7 O2 -> 4 NO2 + 6 H2O}}

It can also be produced by the oxidation of [[nitrosyl chloride]]:

:{{chem2|2 NOCl + O2 -> 2NO2 + Cl2}}

Instead, most laboratory syntheses stabilize and then heat the nitric acid to accelerate the decomposition. For example, the thermal decomposition of some metal nitrates generates {{chem2|NO2}}:<ref>{{Greenwood&Earnshaw2nd|page=456}} </ref>

:{{chem2|Pb(NO3)2 -> PbO + 2 NO2 +}} {{frac|1|2}}&nbsp;{{chem2|O2}}

Alternatively, dehydration of [[nitric acid]] produces [[dinitrogen pentoxide|nitronium nitrate]]...

:{{chem2|2 HNO3 -> N2O5 + H2O}}

:{{chem2|6 HNO3 +}} {{frac|1|2}}&nbsp;{{chem2|P4O10 -> 3 N2O5 + 2 H3PO4}}

...which subsequently undergoes thermal decomposition:

:{{chem2|N2O5 -> 2 NO2 +}} {{frac|1|2}}&nbsp;{{chem2|O2}}

{{chem2|NO2}} is generated by the reduction of concentrated nitric acid with a metal (such as copper):

:{{chem2|4 HNO3 + Cu -> Cu(NO3)2 + 2 NO2 + 2 H2O}}

==Selected reactions==

Nitric acid decomposes slowly to nitrogen dioxide by the overall reaction:

:4 {{chem2|HNO3}} → 4 {{chem2|NO2}} + 2 {{chem2|H2O}} + {{chem2|O2}}

The nitrogen dioxide so formed confers the characteristic yellow color often exhibited by this acid. However, the reaction is too slow to be a practical source of {{chem2|NO2}}.

===Thermal properties===

At low temperatures, {{chem2|NO2}} reversibly converts to the colourless gas [[dinitrogen tetroxide]] ({{chem2|N2O4}}):

:{{chem2|2 NO2 <-> N2O4}}

The exothermic equilibrium has [[enthalpy change]] {{nowrap|1=Δ''H'' = −57.23 kJ/mol}}.<ref name="Holleman">Holleman, A. F.; Wiberg, E. (2001) ''Inorganic Chemistry''. Academic Press: San Diego. {{ISBN|0-12-352651-5}}.</ref>

At {{convert|150|C|F K}}, {{chem2|NO2}} decomposes with release of oxygen via an endothermic process ({{nowrap|1=Δ''H'' = 14 kJ/mol}}):

:2 NO₂ →2 NO + &nbsp;{{chem2|O2}}

===As an oxidizer ===

As suggested by the weakness of the N–O bond, {{chem2|NO2}} is a good oxidizer. Consequently, it will combust, sometimes explosively, in the presence of [[hydrocarbon]]s.<ref>[https://pubs.rsc.org/en/content/articlelanding/2001/cp/b006088g physical chemistry]</ref>

===Hydrolysis===

NO₂ [[hydrolysis|reacts with water]] to give [[nitric acid]] and [[nitrous acid]]:

:{{chem2|2 NO2 + H2O -> HNO3 + HNO2}}

This reaction is one of the steps in the [[Ostwald process]] for the industrial production of nitric acid from ammonia.<ref name=Ull>{{cite encyclopedia |author=Thiemann, Michael |author2=Scheibler, Erich |author3=Wiegand, Karl Wilhelm |year=2005|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a17_293|chapter=Nitric Acid, Nitrous Acid, and Nitrogen Oxides|isbn=978-3-527-30673-2}}</ref> This reaction is negligibly slow at low concentrations of NO₂ characteristic of the ambient atmosphere, although it does proceed upon NO₂ uptake to surfaces. Such surface reaction is thought to produce gaseous [[Nitrous acid|HNO₂]] (often written as [[HONO]]) in outdoor and indoor environments.<ref>{{Cite journal|last1=Finlayson-Pitts|first1=B. J.|last2=Wingen|first2=L. M.|last3=Sumner|first3=A. L.|last4=Syomin|first4=D.|last5=Ramazan|first5=K. A.|date=2002-12-16|title=The heterogeneous hydrolysis of NO₂ in laboratory systems and in outdoor and indoor atmospheres: An integrated mechanism|journal=Physical Chemistry Chemical Physics|language=en|volume=5|issue=2|pages=223–242|doi=10.1039/B208564J|url=https://escholarship.org/content/qt8wx9v8h9/qt8wx9v8h9.pdf?t=njz4b2}}</ref>

===Conversion to nitrates===

{{chem2|NO2}} is used to generate anhydrous metal nitrates from the oxides:<ref name="Holleman" />

:{{chem2|MO + 3 NO2 -> M(NO3)2 + NO}}

Alkyl and metal iodides give the corresponding nitrates:<ref name="G&E" />

:{{chem2|TiI4 + 8 NO2 -> Ti(NO3)4 + 4 NO + 2 I2}}

===With organic compounds===

The reactiivity of nitrogen dioxide toward [[organic compound]]s has long been known.<ref>{{cite journal |doi=10.1021/cr60114a002 |title=The Reactions of Nitrogen Tetroxide with Organic Compounds |date=1945 |last1=Riebsomer |first1=J. L. |journal=Chemical Reviews |volume=36 |issue=2 |pages=157–233 }}</ref> For example, it reacts with amides to give N-nitroso derivatives.<ref>{{cite journal |doi=10.15227/orgsyn.047.0044 |title=Deamination of Amines. 2-Phenylethyl Benzoate Via the Nitrosoamide Decomposition |journal=Organic Syntheses |date=1967 |volume=47 |page=44|author=Emil White }}</ref> It is used for nitrations under anhydrous conditions.<ref>{{March6th|page=687}} </ref>

==Uses==

{{chem2|NO2}} is used as an intermediate in the manufacturing of [[nitric acid]], as a nitrating agent in the manufacturing of [[chemical explosive]]s, as a polymerization inhibitor for [[acrylates]], as a [[flour bleaching agent]],<ref>Subcommittee on Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants; Committee on Toxicology; Board on Environmental Studies and Toxicology; Division on Earth and Life Studies; National Research Council. [http://www.nap.edu/read/11170/chapter/12 Chapter 12: Nitrogen Dioxide] in Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants. National Academies Press, 2007. {{ISBN|978-0-309-09225-8}}</ref>{{rp|223}} and as a room temperature sterilization agent.<ref name="Mechanism Overview, June 2012">{{cite web |title=Mechanism Overview, June 2012 |url=http://noxilizer.com/pdf/news/WhitePaper-Mechanism_Overview_6_14_12.pdf |archive-url=https://web.archive.org/web/20160412094958/http://noxilizer.com/pdf/news/WhitePaper-Mechanism_Overview_6_14_12.pdf |archive-date=12 April 2016 |access-date=2 July 2013 |work=noxilizer.com |publisher=Noxilizer, Inc.}}</ref> It is also used as an [[oxidizer]] in [[rocket fuel]], for example in [[red fuming nitric acid]]; it was used in the [[Titan (rocket family)|Titan rockets]], to launch [[Project Gemini]], in the maneuvering thrusters of the [[Space Shuttle]], and in uncrewed [[space probes]] sent to various planets.<ref name="ChemWorld">Cotton, Simon (21 March 2013) [http://www.rsc.org/chemistryworld/2013/04/nitrogen-dioxide-podcast Nitrogen dioxide]. ''RSC Chemistry World''.</ref>

==Environmental presence==

[[File:Aura_OMI_Nitrogen_dioxide_troposphere_column.png|left|thumb|Nitrogen dioxide [[Troposphere|tropospheric]] column density in 2011.]]

Nitrogen dioxide typically arises via the oxidation of [[nitric oxide]] by oxygen in air (e.g. as result of [[corona discharge]]):<ref name="Holleman" />

:2 {{chem2|NO + O2 → 2 NO2}}

{{chem2|NO2}} is introduced into the environment by natural causes, including entry from the [[stratosphere]], bacterial respiration, volcanos, and lightning. These sources make {{chem2|NO2}} a [[trace gas]] in the [[atmosphere of Earth]], where it plays a role in absorbing [[sunlight]] and regulating the chemistry of the [[troposphere]], especially in determining [[ozone]] concentrations.<ref>WHO Air Quality Guidelines – Second Edition. Chapter 7.1 [http://www.euro.who.int/__data/assets/pdf_file/0017/123083/AQG2ndEd_7_1nitrogendioxide.pdf Nitrogen Dioxide].</ref>

=== Anthropogenic sources ===

[[File:AirQualityLondon1.jpg|thumb|right|Nitrogen dioxide [[diffusion tube]] for [[air quality monitoring]] in the [[City of London]].]]

Nitrogen dioxide also forms in most [[combustion]] processes. At elevated temperatures [[nitrogen]] combines with [[oxygen]] to form nitrogen dioxide:

:{{chem2|N2 + 2 O2 -> 2 NO2}}

For the general public, the most prominent sources of {{chem2|NO2}} are [[internal combustion engines]], as combustion temperatures are high enough to thermally combine some of the nitrogen and oxygen in the air to form {{chem2|NO2}}.<ref name="EPAmain" />

Outdoors, {{chem2|NO2}} can be a result of traffic from motor vehicles.<ref>{{Cite web |url=https://www.who.int/phe/health_topics/outdoorair/outdoorair_aqg/en/ |archive-url=https://web.archive.org/web/20140309212121/http://www.who.int/phe/health_topics/outdoorair/outdoorair_aqg/en/ |archive-date=March 9, 2014 |title=Air quality guidelines – global update 2005 |website=WHO |access-date=2016-10-19}}</ref> Indoors, exposure arises from cigarette smoke,<ref name="ATSDR">US Dept. of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry, Division of Toxicology. April 2002 [http://www.atsdr.cdc.gov/toxfaqs/tfacts175.pdf ATSDR Nitrous Oxides].</ref> and [[butane]] and [[kerosene heater]]s and stoves.<ref>{{cite web |date=2013-03-21 |title=The Impact of Unvented Gas Heating Appliances on Indoor Nitrogen Dioxide Levels in 'TIGHT' Homes |url=http://www.ahrinet.org/App_Content/ahri/files/Product%20Section/Vent-Free%20NO2%20Modeling%20Study%20Final%20Summary%20March%2021%202013.pdf |work=ahrinet.org |access-date=2018-09-25 |archive-date=2020-08-05 |archive-url=https://web.archive.org/web/20200805094718/http://www.ahrinet.org/App_Content/ahri/files/Product%20Section/Vent-Free%20NO2%20Modeling%20Study%20Final%20Summary%20March%2021%202013.pdf }}</ref> Indoor exposure levels of {{chem2|NO2}} are, on average, at least three times higher in homes with gas stoves compared to electric stove.<ref name=":1">{{Cite journal |last1=Garrett |first1=Maria H. |last2=Hooper |first2=Martin A. |last3=Hooper |first3=Beverley M. |last4=Abramson |first4=Michael J. |date=1998-09-01 |title=Respiratory Symptoms in Children and Indoor Exposure to Nitrogen Dioxide and Gas Stoves |url=https://research.monash.edu/files/304219582/304218990_oa.pdf |journal=American Journal of Respiratory and Critical Care Medicine |volume=158 |issue=3 |pages=891–895 |doi=10.1164/ajrccm.158.3.9701084 |pmid=9731022}}</ref><ref name="EPAbasic">{{EPA content|url=https://www.epa.gov/no2-pollution|article=Nitrogen Dioxide Basic Information|access-date=February 23, 2016}}</ref> [[File:Nizhniy tagil ntmk main entrance.JPG|thumb|A "fox tail" over [[Nizhniy Tagil Iron and Steel Works]]|left]]Workers in industries where {{chem2|NO2}} is used are also exposed and are at risk for [[occupational lung disease]]s, and [[NIOSH]] has set exposure limits and safety standards.<ref name="PGCH" /> Workers in high voltage areas especially those with spark or plasma creation are at risk.{{cn|date=December 2022}} [[Farmworker|Agricultural workers]] can be exposed to {{chem2|NO2}} arising from grain decomposing in silos; chronic exposure can lead to lung damage in a condition called "[[Occupational lung disease#Silo-filler.27s disease|silo-filler's disease]]".<ref>{{cite journal|last1=Chan-Yeung |first1=M. |last2=Ashley |first2=M. J. |last3=Grzybowski |first3=S. |title=Grain dust and the lungs |journal=Canadian Medical Association Journal |volume=118 |issue=10 |pages=1271–4 |pmid=348288 |pmc=1818652 |year=1978}}</ref><ref>{{cite journal|doi=10.1148/radiographics.11.4.1887117 |title=Agricultural disorders of the lung|journal=Radiographics|volume=11|issue=4|pages=625–34|pmid=1887117|year=1991|last1=Gurney|first1=J. W.|last2=Unger|first2=J. M.|last3=Dorby|first3=C. A.|last4=Mitby|first4=J. K.|last5=von Essen|first5=S. G.|doi-access=free}}</ref>

==Toxicity==

[[File:No2toxpathwaysEPA.png|thumb|Possible pathways implicated in long-term nitrogen dioxide exposure. Dotted lines indicate findings only supported by [[Animal testing|animal studies]], while solid lines indicate findings from controlled [[Human subject research|human exposure studies]]. Dashed lines indicate speculative links to asthma exacerbation and respiratory tract infections. ELF&nbsp;= [[epithelial lining fluid]].<ref name="EPAassess2016" />{{rp|4–62}}|660x660px]]

{{main|Nitrogen dioxide poisoning}}

{{chem2|NO2}} diffuses into the epithelial lining fluid (ELF) of the [[respiratory epithelium]] and dissolves. There, it chemically reacts with antioxidant and lipid molecules in the ELF. The health effects of {{chem2|NO2}} are caused by the reaction products or their metabolites, which are [[reactive nitrogen species]] and [[reactive oxygen species]] that can drive [[bronchoconstriction]], inflammation, reduced immune response, and may have effects on the heart.<ref name="EPAassess2016">U.S. EPA. Integrated Science Assessment for Oxides of Nitrogen – Health Criteria (2016 Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/068, 2016. [https://www.federalregister.gov/articles/2016/01/28/2016-01548/integrated-science-assessment-for-oxides-of-nitrogen-health-criteria Federal Register Notice Jan 28, 2016] Free download available at [https://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=310879 Report page at EPA website].</ref>

=== Acute exposure ===

Acute harm due to {{chem2|NO2}} exposure is rare. 100–200&nbsp;ppm can cause mild irritation of the nose and throat, 250–500&nbsp;ppm can cause [[Pulmonary edema|edema]], leading to [[bronchitis]] or [[pneumonia]], and levels above 1000&nbsp;ppm can cause death due to asphyxiation from fluid in the lungs. There are often no symptoms at the time of exposure other than transient cough, fatigue or nausea, but over hours inflammation in the lungs causes edema.<ref name="ToxnetHH">Toxnet [https://web.archive.org/web/20180612163553/https://toxnet.nlm.nih.gov/cgi-bin/sis/search2/r?dbs+hsdb:@term+@rn+10102-44-0 Nitrogen dioxide: Human Health Effects] Page accessed March 28, 2016.</ref><ref>CDC NIOSH [https://www.cdc.gov/niosh/ipcsneng/neng0930.html International Chemical Safety Cards (ICSC): Nitrogen Dioxide] Page last reviewed: July 22, 2015; Page last updated: July 1, 2014.</ref>

For skin or eye exposure, the affected area is flushed with saline. For inhalation, oxygen is administered, [[bronchodilators]] may be administered, and if there are signs of [[methemoglobinemia]], a condition that arises when nitrogen-based compounds affect the [[hemoglobin]] in red blood cells, [[methylene blue]] may be administered.<ref>Agency for Toxic Substances and Disease Registry via the CDC [https://web.archive.org/web/20100528070306/http://www.atsdr.cdc.gov/MMG/MMG.asp?id=394&tid=69 Medical Management Guidelines for Nitrogen Oxides] Page last reviewed: October 21, 2014; Page last updated: October 21, 2014</ref><ref>University of Kansas Hospital, Poison Control Center [http://www.kumed.com/~/media/Imported/kumed/documents/kdhe-20nitrogen-20dioxide.ashx?la=en Poison Facts: Medium Chemicals: Nitrogen Dioxide] {{Webarchive|url=https://web.archive.org/web/20160411001233/http://www.kumed.com/~/media/Imported/kumed/documents/kdhe-20nitrogen-20dioxide.ashx?la=en |date=2016-04-11 }} page accessed March 28, 2016</ref>

It is classified as an [[List of extremely hazardous substances|extremely hazardous substance]] in the United States as defined in Section 302 of the U.S. [[Emergency Planning and Community Right-to-Know Act]] (42 U.S.C. 11002), and it is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.<ref name="gov-right-know">{{Cite web | publisher = [[United States Government Publishing Office|Government Printing Office]] | title = 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities | url = http://edocket.access.gpo.gov/cfr_2008/julqtr/pdf/40cfr355AppA.pdf | edition = July 1, 2008 | access-date = October 29, 2011 | archive-url = https://web.archive.org/web/20120225051612/http://edocket.access.gpo.gov/cfr_2008/julqtr/pdf/40cfr355AppA.pdf | archive-date = February 25, 2012 }}</ref>

=== Long-term ===

Exposure to low levels of {{chem2|NO2}} over time can cause changes in lung function.<ref>{{cite journal

| last = Int Panis

| first = L

| title = Short-term air pollution exposure decreases lung function: a repeated measures study in healthy adults

| journal = Environmental Health

| volume = 16

| issue = 1

| page = 60

| year = 2017

| doi = 10.1186/s12940-017-0271-z

| pmid =28615020

| pmc = 5471732

| doi-access = free

| bibcode = 2017EnvHe..16...60I

}}</ref> Cooking with a [[gas stove]] is associated with poorer [[indoor air quality]]. Combustion of gas can lead to increased concentrations of nitrogen dioxide throughout the home environment which is linked to [[Respiratory disease|respiratory issues and diseases]].<ref name=":0" /><ref name=":2" /> Children exposed to {{chem2|NO2}} are more likely to be admitted to hospital with [[asthma]].<ref>{{Cite journal |last1=Wang |first1=Weiyi |last2=Gulliver |first2=John |last3=Beevers |first3=Sean |last4=Freni Sterrantino |first4=Anna |last5=Davies |first5=Bethan |last6=Atkinson |first6=Richard W. |last7=Fecht |first7=Daniela |date=2024 |title=Short-Term Nitrogen Dioxide Exposure and Emergency Hospital Admissions for Asthma in Children: A Case-Crossover Analysis in England |journal=Journal of Asthma and Allergy |volume=17 |pages=349–359 |doi=10.2147/JAA.S448600 |doi-access=free |issn=1178-6965 |pmid=38623450|pmc=11016460 }}</ref>

== Environmental effects ==

Interaction of {{chem2|NO2}} and other {{chem2|NO_{x}|}} with water, oxygen and other chemicals in the atmosphere can form [[acid rain]] which harms sensitive ecosystems such as lakes and forests.<ref>{{Cite web|last=US EPA|first=OAR|date=2016-07-06|title=Basic Information about NO2|url=https://www.epa.gov/no2-pollution/basic-information-about-no2|access-date=2020-07-03|website=US EPA|language=en}}</ref> Elevated levels of {{chem|NO|2}} can also harm vegetation, decreasing growth, and reduce crop yields.<ref>{{Cite web |title=Nitrogen oxides |url=https://www.qld.gov.au/environment/pollution/monitoring/air/air-pollution/pollutants/nitrogen-oxides|access-date=2020-07-03|website=Queensland Government|language=en}}</ref>

==See also==

* [[Dinitrogen tetroxide]] ({{chem2|N2O4}})

* [[Nitric oxide]] ({{chem2|NO}}) – pollutant that is short lived because it converts to {{chem2|NO2}} in the presence of ozone

* [[Nitrite]] ({{chem2|NO2-}})

* [[Nitrous oxide]] ({{chem2|N2O}}) – "laughing gas", a linear molecule, isoelectronic with {{chem2|CO2}} but with a nonsymmetric arrangement of atoms ({{chem2|NNO}})

* [[Nitryl]]

==References==

{{reflist|30em}}

==Cited sources==

*{{cite book | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = [[CRC Press]] | isbn = 978-1-4398-5511-9| title-link = CRC Handbook of Chemistry and Physics }}

==External links==

{{Commons category|Nitrogen dioxide}}

*[http://www.inchem.org/documents/icsc/icsc/eics0930.htm International Chemical Safety Card 0930]

*[http://www.npi.gov.au/resource/oxides-nitrogen-0 National Pollutant Inventory – Oxides of nitrogen fact sheet]

*[https://www.cdc.gov/niosh/npg/npgd0454.html NIOSH Pocket Guide to Chemical Hazards]

*WHO-Europe reports: [http://www.euro.who.int/document/e79097.pdf Health Aspects of Air Pollution (2003)] (PDF) and "[https://web.archive.org/web/20050909162153/http://www.euro.who.int/document/E82790.pdf Answer to follow-up questions from CAFE (2004)] (PDF)

*[http://www.greenfacts.org/air-pollution/nitrogen-dioxide-no2/index.htm Nitrogen Dioxide Air Pollution]

*[https://earth.nullschool.net/#current/chem/surface/level/overlay=no2/winkel3 Current global map of nitrogen dioxide distribution]

*[https://web.archive.org/web/20160415110253/http://www.iom-world.org/pubs/IOM_TM0403.pdf A review of the acute and long term impacts of exposure to nitrogen dioxide in the United Kingdom] IOM Research Report TM/04/03

*[https://pubs.rsc.org/en/content/articlelanding/2001/cp/b006088g Reaction of nitrogen dioxide with hydrocarbons and its influence on spontaneous ignition]

{{nitrogen compounds}}

{{Oxides}}

{{oxygen compounds}}

{{Authority control}}

{{DEFAULTSORT:Nitrogen Dioxide}}

[[Category:Nitrogen oxides]]

[[Category:Bleaches]]

[[Category:Hazardous air pollutants]]

[[Category:Smog]]

[[Category:Free radicals]]

[[Category:Food additives]]

[[Category:Gases with color]]

[[Category:Triatomic molecules]]