Exhaust gas

{{Short description|Gases emitted as a result of fuel reactions in combustion engines}} {{Use dmy dates|date=June 2023}} {{MCN|date=June 2025}} [[File:Diesel-smoke.jpg|thumb|This diesel-powered truck emits an exhaust gas full of black [[Particulates|particulate matter]] when starting up the engine.]] {{Pollution sidebar|Air}}

'''Exhaust gas''' or [[flue gas]] is emitted as a result of the [[combustion]] of fuels such as [[natural gas]], [[gasoline|gasoline (petrol)]], [[diesel fuel]], [[fuel oil]], biodiesel blends,<ref name="sciencedirect.com">{{cite journal|last1=Omidvarborna|title=Characterization of particulate matter emitted from transit buses fueled with B20 in idle modes|journal=Journal of Environmental Chemical Engineering|volume=2|issue=4|pages=2335–2342|doi=10.1016/j.jece.2014.09.020|display-authors=etal|year=2014}}</ref> or [[coal]]. According to the type of engine, it is discharged into the atmosphere through an [[exhaust pipe]], [[flue gas stack]], or [[propelling nozzle]]. It often disperses downwind in a pattern called an ''exhaust plume''.

It is a major component of [[motor vehicle]] emissions (and from stationary [[internal combustion engine]]s), which can also include [[crankcase]] blow-by and evaporation of unused gasoline.

[[Air pollution]] from burning [[Fossil fuel|fossil fuels]] is estimated to kill over 5 million people each year. Motor vehicle emissions are a common source of air pollution and are a major ingredient in the creation of [[smog]] in some large cities.

==Composition== The largest part of most combustion gas is [[nitrogen]] (N2), water vapor (H2O) (except with pure-carbon fuels), and [[carbon dioxide]] (CO2) (except for fuels without carbon); these are not toxic or noxious (although water vapor and carbon dioxide are [[greenhouse gas]]es that contribute to [[climate change]]). A relatively small part of combustion gas is undesirable, noxious, or toxic substances, such as [[carbon monoxide]] (CO) from incomplete combustion, [[hydrocarbon]]s (properly indicated as CxHy, but typically shown simply as "HC" on emissions-test slips) from unburnt fuel, [[nitrogen oxide]]s (NOx) from excessive combustion temperatures, and [[Atmospheric particulate matter|particulate matter]] (mostly [[soot]]) from incomplete combustion.

==Exhaust gas temperature== Exhaust gas temperature (EGT) is important to the functioning of the [[catalytic converter]] of an [[internal combustion engine]]. It may be measured by an [[exhaust gas temperature gauge]]. EGT is also a measure of engine health in gas-turbine engines (see below).

==Cold engines== [[File:Exhaust.jpg|thumb|right|Steam from tailpipe of cold car]] During the first two minutes after starting the engine of a car that has not been operated for several hours, the amount of emissions can be very high. This occurs for two main reasons: * '''Rich air-fuel ratio requirement in cold engines''': When a cold engine is started, the fuel does not vaporize completely, creating higher emissions of [[hydrocarbon]]s and [[carbon monoxide]], which diminishes only as the engine reaches operating temperature. The duration of this start-up phase has been reduced by advances in materials and technology, including [[Multi-point fuel injection|computer-controlled fuel injection]], shorter intake lengths, and pre-heating of fuel and/or inducted air. * '''Inefficient catalytic converter under cold conditions''': Catalytic converters are very inefficient until warmed up to their [[operating temperature]]. This time has been much reduced by moving the converter closer to the exhaust manifold and even more so placing a small yet quick-to-heat-up converter directly at the exhaust manifold. The small converter handles the start-up emissions, which allows enough time for the larger main converter to heat up. Further improvements can be realised in many ways,<ref>Pulkrabek W.W. (2004) Engineering Fundamentals of the Internal Combustion Engine. Pearson Prentice Hall, new Jersey</ref> including electric heating, thermal battery, chemical reaction preheating, flame heating and superinsulation.

==Passenger car emissions summary== {| class="wikitable" |+U.S. Environmental Protection Agency estimates of average passenger car emissions in the United States for April 2000<ref>{{cite web | url = http://www.epa.gov/otaq/consumer/f00013.pdf | archive-url = https://web.archive.org/web/20011125193019/http://www.epa.gov/otaq/consumer/f00013.pdf | archive-date = 25 November 2001 | title = Average Annual Emissions and Fuel Consumption for Passenger Cars and Light Trucks | publisher = United States Environmental Protection Agency | work = Transportation and Air Quality| date = 19 August 2015 }}</ref> ! Component ! Emission Rate ! Annual pollution emitted |- | Hydrocarbons | 2.80 grams/mile (1.75 g/km) | {{convert|77.1|lb}} |- | Carbon monoxide | 20.9 grams/mile (13.06 g/km) | {{convert|575|lb}} |- | NO''x'' | 1.39 grams/mile (0.87 g/km) | {{convert|38.2|lb}} |- | Carbon dioxide - greenhouse gas | 415 grams/mile (258 g/km) | {{convert|11,450|lb}} |}

Comparable with the [[European emission standards]] EURO III as it was applied in October 2000

In 2000, the United States [[United States Environmental Protection Agency|Environmental Protection Agency]] began to implement more stringent [[emissions standard]]s for light duty vehicles. The requirements were phased in beginning with 2004 vehicles and all new cars and light trucks were required to meet the updated standards by the end of 2007. {| class="wikitable" |+United States Light-Duty Vehicle, Light-Duty Truck, and Medium-Duty Passenger Vehicle—Tier 2 Exhaust Emission Standards (for Bin 5)<ref>{{cite web | url = http://www.epa.gov/otaq/standards/light-duty/tier2stds.htm | archive-url = https://archive.today/20120731034855/http://www.epa.gov/otaq/standards/light-duty/tier2stds.htm | archive-date = 31 July 2012 | title = Light-Duty Vehicle, Light-Duty Truck, and Medium-Duty Passenger Vehicle -- Tier 2 Exhaust Emission Standards | work = Emission Standards Reference Guide | publisher = United States Environmental Protection Agency | date = 14 November 2012}}</ref> ! Component ! Emission Rate ! Annual pollution emitted |- | NMOG ([[Volatile organic compound]]s) | 0.075  grams/mile (0.046 g/km) | {{convert|2.1|lb}} |- | Carbon Monoxide | 3.4 grams/mile (2.1 g/km) | {{convert|94|lb}} |- | NO''X'' | 0.05 grams/mile (0.0305 g/km) | {{convert|1.4|lb}} |- | [[Formaldehyde]] | 0.015 grams/mile (0.0092 g/km) | {{convert|0.41|lb}} |}

==Types==

===Internal-combustion engines=== [[Image:Automobile exhaust gas.jpg|thumb|[[Automobile exhaust]]]]

====Spark-ignition and Diesel engines==== {{see also|Automobile emissions control}}

In [[spark-ignition engine]]s the gases resulting from combustion of the fuel and air mix are called exhaust gases. The composition varies from petrol to diesel engines, but is around these levels: {| class="wikitable" |+Combustion-engine exhaust gases<ref name=AUDIEmiss1>{{cite book |title=Self-Study Programme 230: Motor Vehicle Exhaust Emissions |date=April 2000 |publisher=AUDI |url=http://www.volkspage.net/technik/ssp/ssp/SSP_230.pdf |access-date=23 March 2012}}</ref> ''All figures are approximate'' ! rowspan=2|Compound ! colspan="2" | % of total |- ! Petrol ! Diesel |- |[[Nitrogen]] |71 |67 |- |[[Carbon dioxide]] |14 |12 |- |[[Water vapor]] |13 |11 |- |[[Oxygen]] | |10 |- | Trace elements{{citation needed|date=August 2013}} |< 0.6 |~ 0.3 |- |[[Nitrogen oxide]]s |< 0.25 |< 0.15 |- |[[Carbon monoxide]] |1 - 2 |< 0.045 |- |[[Particulate matter]] | |< 0.045 |- |[[Hydrocarbon]]s |< 0.25 |< 0.03 |- |[[Sulfur dioxide]] |Possible traces |< 0.03 |}

The 10% oxygen for "diesel" is likely if the engine was idling, e.g. in a test rig. It is much less if the engine is running under load, although diesel engines always operate with an excess of air over fuel. {{citation needed|date=July 2016}} The CO content for petrol engines varies from ≈15 ppm for well tuned engine with fuel injection and a catalytic converter up to 100,000 ppm (10%) for a richly tuned carburetor engine, such as typically found on small generators and garden equipment.<ref>{{cite web|url=https://www.abe.iastate.edu/extension-and-outreach/carbon-monoxide-poisoning-operating-fossil-fuel-engines-inside-buildings-aen-206/|title=Carbon Monoxide Poisoning: Operating Fossil Fuel Engines Inside Buildings (AEN-206)|website=Department of Agricultural and Biosystems Engineering|access-date=18 June 2023}}</ref>

=====Nitromethane additive===== Exhaust gas from an internal combustion engine whose fuel includes [[nitromethane]] will contain [[nitric acid]] vapour, which is corrosive, and when inhaled causes a muscular reaction making it impossible to breathe. People who are likely to be exposed to it should wear a [[gas mask]].<ref>{{cite web |url=http://www.turbofast.com.au/racefuel6.html |title=Race Fuel - Nitromethane |website=www.turbofast.com.au |access-date=23 January 2008 |archive-date=13 March 2018 |archive-url=https://web.archive.org/web/20180313151211/http://www.turbofast.com.au/racefuel6.html }}</ref>

====Diesel engines==== {{See also|Soot}} {{Excerpt|Diesel exhaust|only=paragraphs}}

====Gas-turbine engines==== In aircraft gas turbine engines, "exhaust gas temperature" (EGT) is a primary measure of engine health. Typically the EGT is compared with a primary engine power indication called "engine pressure ratio" (EPR). For example: at full power EPR there will be a maximum permitted EGT limit. Once an engine reaches a stage in its life where it reaches this EGT limit, the engine will require specific maintenance in order to rectify the problem. The amount the EGT is below the EGT limit is called EGT margin. The EGT margin of an engine will be greatest when the engine is new, or has been overhauled. For most airlines, this information is also monitored remotely by the airline maintenance department by means of [[ACARS]].

====Jet engines and rocket engines==== [[Image:Jet exhaust by David Shankbone.jpg|thumb|A [[contrail]] formed by the presence of water vapour in the exhaust from jet engines.]] In [[jet engine]]s and [[rocket engine]]s, exhaust from [[propelling nozzle]]s which in some applications shows [[shock diamond]]s.{{Citation needed|date=April 2009}}

===Other types===

====From burning coal==== [[Flue gas emissions from fossil fuel combustion|Flue gas]] is that emitted from ovens, furnaces and boilers.

====Steam engines==== In [[steam engine]] terminology the exhaust is steam that is now so low in pressure that it can no longer do useful work.

==Main motor vehicle emissions== Road vehicles produce a significant amount of all air pollution. Vehicles with petrol and diesel engines produce about half of their emissions from their [[exhaust gas]], and the other half from [[non-exhaust emissions]] (tire and brake wear and erosion or disturbance of the road surface).

===NO''x''=== [[Image:SmogNY.jpg|thumb|right|Smog in [[New York City]] as viewed from the [[World Trade Center (1973–2001)|World Trade Center]] in 1988]] Mono-[[nitrogen oxide]]s NO and NO2 ([[NOx]]) (whether produced this way or naturally by [[lightning]]) react with [[ammonia]], moisture, and other compounds to form [[nitric acid]] vapor and related particles. Small particles can penetrate deeply into sensitive lung tissue and damage it, causing premature death in extreme cases. Inhalation of NO species increases the risk of [[lung cancer]]<ref>{{cite journal|last1=Hamra|first1=GB|last2=Laden|first2=F|last3=Cohen|first3=AJ|last4=Raaschou-Nielsen|first4=O|last5=Brauer|first5=M|last6=Loomis|first6=D|title=Lung Cancer and Exposure to Nitrogen Dioxide and Traffic: A Systematic Review and Meta-Analysis.|journal=Environmental Health Perspectives|date=November 2015|volume=123|issue=11|pages=1107–12|doi=10.1289/ehp.1408882|pmid=25870974|pmc=4629738}}</ref> and colorectal cancer.<ref>{{cite journal|last1=Turner|first1=MC|last2=Krewski|first2=D|last3=Diver|first3=WR|last4=Pope CA|first4=3rd|last5=Burnett|first5=RT|last6=Jerrett|first6=M|last7=Marshall|first7=JD|last8=Gapstur|first8=SM|title=Ambient Air Pollution and Cancer Mortality in the Cancer Prevention Study II.|journal=Environmental Health Perspectives|date=21 August 2017|volume=125|issue=8|page=087013|doi=10.1289/EHP1249|pmid=28886601|pmc=5783657}} {{open access}}</ref> and inhalation of such particles may cause or worsen respiratory diseases such as [[emphysema]] and [[bronchitis]] and heart disease.<ref>{{cite web | url = http://www.epa.gov/air/nitrogenoxides/health.html | archive-url = https://archive.today/20120802140219/http://www.epa.gov/air/nitrogenoxides/health.html | archive-date = 2 August 2012 | work = Nitrogen Dioxide | title = Health | publisher = United States Environmental Protection Agency | date = 14 February 2013}}</ref><ref>{{cite web | url = http://www.epa.gov/air/noxfacts.pdf | archive-url = https://web.archive.org/web/20011110030903/http://www.epa.gov/air/noxfacts.pdf | archive-date = 10 November 2001 | title = The Regional Transport of Ozone: New EPA Rulemaking on Nitrogen Oxide Emissions (EPA-456/F-98-006) | publisher = United States Environmental Protection Agency | date = September 1998}}</ref><ref name=EPA_NOx>{{cite web | url = http://www.epa.gov/cgi-bin/broker?_service=data&_debug=0&_program=dataprog.national_1.sas&polchoice=NOX | archive-url = https://archive.today/20121213042302/http://www.epa.gov/cgi-bin/broker?_service=data&_debug=0&_program=dataprog.national_1.sas&polchoice=NOX | archive-date = 13 December 2012 | title = State and County Emission Summaries: Nitrogen Oxides | work = Air emission sources | publisher = United States Environmental Protection Agency | date = 25 October 2013}}</ref>

In a 2005 [[United States Environmental Protection Agency|U.S. EPA]] study the largest emissions of {{NOx}} came from on road motor vehicles, with the second largest contributor being [[non-road equipment]] which is mostly gasoline and diesel stations.<ref name="EPA_NOx" />

The resulting nitric acid may be washed into soil, where it becomes [[nitrate]], which is useful to growing plants.

===Volatile organic compounds=== [[File:Sources of Volatile Organic Compounds.PNG|thumb|upright=2.0|right|Non-road equipment is mostly gasoline and diesel stations.<ref name="epa.gov">{{cite web | url = http://www.epa.gov/cgi-bin/broker?_service=data&_debug=0&_program=dataprog.national_1.sas&polchoice=VOC | archive-url = https://archive.today/20120801235821/http://www.epa.gov/cgi-bin/broker?_service=data&_debug=0&_program=dataprog.national_1.sas&polchoice=VOC | archive-date = 1 August 2012 | title = State and County Emission Summaries: Volatile Organic Compounds | work = Air emission sources | publisher = United States Environmental Protection Agency | date = 25 October 2013}}</ref>]] When oxides of nitrogen (NOx) and [[volatile organic compound]]s (VOCs) react in the presence of sunlight, ground level [[ozone]] is formed, a primary ingredient in [[smog]]. A 2005 U.S. EPA report gives road vehicles as the second largest source of VOCs in the U.S. at 26% and 19% are from non road equipment which is mostly gasoline and diesel stations.<ref name="epa.gov"/> 27% of VOC emissions are from solvents which are used in the manufacturer of paints and paint thinners and other uses.<ref>{{cite web | url = https://toxics.usgs.gov/definitions/vocs.html | title = Volatile Organic Compounds (VOCs) | publisher = United States Geological Survey (USGS) | work = Toxic Substances Hydrology Program | date = 12 April 2013 | access-date = 2 June 2014 | archive-date = 5 September 2015 | archive-url = https://web.archive.org/web/20150905205650/http://toxics.usgs.gov/definitions/vocs.html }}</ref>

===Ozone=== Ozone is beneficial in the upper atmosphere,<ref>{{cite web|url=http://www.epa.gov/ozone/basicinfo.html|archive-url=https://archive.today/20140214093341/http://www.epa.gov/ozone/basicinfo.html|archive-date=14 February 2014|title=Ozone Layer Protection - US EPA|first=US|last=EPA, OAR, OAP, SPD|website=US EPA}}</ref> but at ground level ozone irritates the [[respiratory system]], causing coughing, choking, and reduced lung capacity.<ref>{{cite web|url=http://www.epa.gov/airquality/ozonepollution/health.html|archive-url=https://archive.today/20140214093404/http://www.epa.gov/airquality/ozonepollution/health.html|archive-date=14 February 2014|title = Air Quality Planning and Standards}}</ref> It also has many negative effects throughout the ecosystem.<ref>{{cite web |url=http://www.epa.gov/groundlevelozone/ecosystem.html |title=Ecosystem Effects {{!}} Ground-level Ozone {{!}} US EPA |website=[[United States Environmental Protection Agency]] |archive-url=https://web.archive.org/web/20120518004831/http://www.epa.gov/groundlevelozone/ecosystem.html |archive-date=2012-05-18}}</ref>

===Carbon monoxide (CO)=== [[File:MOPITT www.acd.ucar.edu.Web-201003-mixing ratio at surface.png|thumb|upright=1.5|[[MOPITT]] satellite computer image of carbon monoxide March 2010]] [[Carbon monoxide poisoning]] is the most common type of fatal air poisoning in many countries.<ref name="Toxicology2002-omaye">{{cite journal|author=Omaye ST.| title=Metabolic modulation of carbon monoxide toxicity|journal=Toxicology|year=2002|pages=139–150|volume=180|issue=2|doi=10.1016/S0300-483X(02)00387-6|pmid=12324190}}</ref> [[Carbon monoxide]] is colorless, odorless and tasteless, but highly toxic. It combines with [[hemoglobin]] to produce [[carboxyhemoglobin]], which blocks the transport of oxygen. At concentrations above 1000ppm it is considered immediately dangerous and is the most immediate health hazard from running engines in a poorly ventilated space. In 2011, 52% of carbon monoxide emissions were created by mobile vehicles in the U.S.<ref>{{cite web | url = https://www3.epa.gov/cgi-bin/broker?polchoice=CO&_debug=0&_service=data&_program=dataprog.national_1.sas | work = Air Emission Sources | title = State and County Emission Summaries: Carbon Monoxide | date = 25 October 2013 | publisher = United States Environmental Protection Agency}}</ref>

===Hazardous air pollutants (toxics)=== [[Chronic (medicine)|Chronic]] (long-term) exposure to [[Benzene#Health effects|benzene]] ([[Benzene|C6H6]]) damages [[bone marrow]]. It can also cause excessive bleeding and depress the [[immune system]], increasing the chance of [[infection]]. Benzene causes leukemia and is associated with other blood cancers and pre-cancers of the blood.<ref>{{cite web | url = http://www.theaa.com/motoring_advice/car-buyers-guide/cbg_toxics.html | title = Exhaust emissions: What comes out of your car's exhaust? | date = 23 February 2012 | publisher = Automobile Association Developments Limited}}</ref><ref>{{Cite journal | url = http://www.browardcountymufflers.com/wp-content/uploads/2014/07/f02004.pdf | title = Air Toxics from Motor Vehicles | journal = Transportation and Air Quality | publisher = United States Environmental Protection Agency}}</ref>

===Particulate matter (PM10 and PM2.5)=== The [[Particulate Matter#Health effects|health effects]] of inhaling [[Atmospheric particulate matter|airborne particulate matter]] have been widely studied in humans and animals and include [[asthma]], [[lung cancer]], cardiovascular issues, premature [[death]].<ref>{{cite journal|last1=Kurt|first1=OK|last2=Zhang|first2=J|last3=Pinkerton|first3=KE|title=Pulmonary health effects of air pollution.|journal=Current Opinion in Pulmonary Medicine|date=March 2016|volume=22|issue=2|pages=138–43|doi=10.1097/MCP.0000000000000248|pmid=26761628|pmc=4776742}}</ref><ref>{{cite journal|last1=Bourdrel|first1=T|last2=Bind|first2=MA|last3=Béjot|first3=Y|last4=Morel|first4=O|last5=Argacha|first5=JF|title=Cardiovascular effects of air pollution.|journal=Archives of Cardiovascular Diseases|date=November 2017|volume=110|issue=11|pages=634–642|doi=10.1016/j.acvd.2017.05.003|pmid=28735838|pmc=5963518}}</ref><ref>{{cite journal|last1=Babadjouni|first1=RM|last2=Hodis|first2=DM|last3=Radwanski|first3=R|last4=Durazo|first4=R|last5=Patel|first5=A|last6=Liu|first6=Q|last7=Mack|first7=WJ|title=Clinical effects of air pollution on the central nervous system; a review.|journal=Journal of Clinical Neuroscience|date=September 2017|volume=43|pages=16–24|doi=10.1016/j.jocn.2017.04.028|pmid=28528896|pmc=5544553}}</ref> Because of the size of the particles, they can penetrate the deepest part of the lungs.<ref>Region 4: Laboratory and Field Operations — PM 2.5 (2008).''PM 2.5 Objectives and History.'' U.S. Environmental Protection Agency.</ref> A 2011 UK study estimates 90 deaths per year due to passenger vehicle PM.<ref>{{cite journal| doi=10.1021/es060517w| title=Air Quality Impacts of Climate Mitigation: UK Policy and Passenger Vehicle Choice| year=2007| last1=Mazzi| first1=Eric A.| last2=Dowlatabadi| first2=Hadi| journal=Environmental Science & Technology| volume=41| pages=387–92| issue=2| pmid=17310696| bibcode=2007EnST...41..387M| doi-access=free}}</ref> In a 2006 publication, the [[Federal Highway Administration|U.S. Federal Highway Administration]] (FHWA) state that in 2002 about 1% of all PM10 and 2% of all PM2.5 emissions came from the exhaust of on-road motor vehicles (mostly from [[diesel engine]]s).<ref name="FHA_facts">{{cite web |url=http://www.fhwa.dot.gov/environment/aqfactbk/page10.htm |archive-url=https://web.archive.org/web/20060616142403/http://www.fhwa.dot.gov/environment/aqfactbk/page10.htm |archive-date=16 June 2006 |title=Transportation Air Quality: Selected Facts and Figures |year=2006 |publisher=U.S. Department of Transportation Federal Highway Commission |access-date=2010-04-14}}</ref> In Chinese, European, and Indian markets, both diesel and gasoline vehicles are required to have a [[diesel particulate filter|tailpipe filter]] installed, while the United States has mandated it for diesel only. In 2022, British testing specialist Emissions Analytics estimated that the 300 million or so gasoline vehicles in the US over the subsequent decade would emit around 1.6 septillion harmful particles.<ref>{{cite news |last1=Lewis |first1=Barbara |last2=Carey |first2=Nick |title=Lacking filters, U.S. cars set to emit a septillion more particles - research |url=https://www.reuters.com/business/autos-transportation/lacking-filters-us-cars-set-emit-septillion-more-particles-research-2022-04-27/ |work=Reuters |date=27 April 2022 |language=en}}</ref>

===Carbon dioxide (CO2)=== [[Carbon dioxide]] is a [[greenhouse gas]]. Motor vehicle CO2 emissions are part of the anthropogenic contribution to the growth of CO2 concentrations in the atmosphere which according to the vast majority of the scientific community is causing [[climate change]].<ref>[http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_FINAL.pdf IPCC, 2013: Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.</ref> Motor vehicles are calculated to generate about 20% of the European Union's man-made CO2 emissions, with passenger cars contributing about 12%.<ref>{{cite web |url=http://europa.eu/rapid/pressReleasesAction.do?reference=IP/07/155&format=HTML&aged=0&language=EN&guiLanguage=en |title=Commission plans legislative framework to ensure the EU meets its target for cutting CO2 emissions from cars |date=2007-02-07 |publisher=European Commission}}</ref> [[European emission standards]] limit the CO2 emissions of new passenger cars and light vehicles. The European Union average new car CO2 emissions figure dropped by 5.4% in the year to the first quarter of 2010, down to 145.6 [[g/km]].<ref>{{cite web |url=http://www.autoevolution.com/news/eu-average-new-car-co2-emissions-down-54-percent-in-q1-19385.html |title=EU Average New Car CO2 Emissions Down 5.4 Percent in Q1 |date=2010-04-19 |publisher=SoftNews NET |work=autoevolution}}</ref>

===Water vapour=== Vehicle exhaust contains much [[water vapour]].

====Water recovery==== There has been research into ways that troops in deserts can recover drinkable water from their vehicles' exhaust gases.<ref>{{cite web|url=https://www.google.co.uk/search?q=recovering+water+from+diesel+exhaust&ie=utf-8&oe=utf-8&gws_rd=cr&ei=qI7hVsOSHYr3UKvnruAE#q=recovering+water+from+exhaust|title=recovering water from diesel exhaust - Google Search|website=www.google.co.uk}}</ref>

==Pollution reduction== {{see also | Air suction valve | Vehicle-specific power}} [[Emission standard]]s focus on reducing [[pollutant]]s contained in the exhaust gases from vehicles as well as from industrial flue gas stacks and other [[air pollution]] exhaust sources in various large-scale industrial facilities such as [[oil refinery|petroleum refineries]], [[natural gas processing]] plants, [[petrochemical]] plants and [[chemical]] production plants.<ref>{{cite web|url=http://www.epa.gov/oar/oaqps/peg_caa/pegcaain.html|archive-url=https://archive.today/19970619011807/http://www.epa.gov/oar/oaqps/peg_caa/pegcaain.html|archive-date=19 June 1997|title=EPA Plain English Guide to the Clean Air Act|access-date=18 June 2023}}</ref><ref>[https://archive.today/20100924132127/http://www.epa.gov/ttn/chief/ap42/index.html US EPA Publication] AP 42, Fifth Edition, Compilation of Air Pollutant Emission Factors</ref> However, these are often referred to as [[flue gas]]es. [[Catalytic converter]]s in cars intend to break down the pollution of exhaust gases using a catalyst. [[Scrubber]]s in ships intend to remove the sulfur dioxide (SO2) of marine exhaust gases. The regulations on marine sulfur dioxide emissions are tightening, however only a small number of special areas worldwide have been designated for low sulfur diesel fuel use only.

==Disease and early deaths== Air pollution from fossil fuel use by industry, power generation, and transportation is estimated to kill over 5 million people each year.<ref>{{Cite journal |last=Lelieveld |first=Jos |last2=Haines |first2=Andy |last3=Burnett |first3=Richard |last4=Tonne |first4=Cathryn |last5=Klingmüller |first5=Klaus |last6=Münzel |first6=Thomas |last7=Pozzer |first7=Andrea |date=2023-11-29 |title=Air pollution deaths attributable to fossil fuels: observational and modelling study |url=https://www.bmj.com/content/383/bmj-2023-077784 |journal=BMJ |language=en |volume=383 |article-number=e077784 |doi=10.1136/bmj-2023-077784 |issn=1756-1833 |pmid=38030155|hdl=10230/60465 |hdl-access=free |pmc=10686100 }}</ref> A 2013 study by the [[Massachusetts Institute of Technology]] (MIT) indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions.<ref>{{cite journal |last1=Caiazzo |first1=Fabio |last2=Ashok |first2=Akshay |last3=Waitz |first3=Ian A. |last4=Yim |first4=Steve H.L. |last5=Barrett |first5=Steven R.H. |date=November 2013 |title=Air pollution and early deaths in the United States. Part I: Quantifying the impact of major sectors in 2005 |journal=Atmospheric Environment |volume=79 |pages=198–208 |bibcode=2013AtmEn..79..198C |doi=10.1016/j.atmosenv.2013.05.081}}</ref> According to another study from the same university, traffic fumes alone cause the death of 5,000 people every year just in the United Kingdom.<ref>{{cite news |author=Roland Pease |title=Traffic pollution kills 5,000 a year in UK, says study |url=https://www.bbc.com/news/science-environment-17704116 |work=BBC News}}</ref>

Researchers from the University of California, Los Angeles School of Public Health say preliminary results of their statistical study of children listed in the California Cancer Registry born between 1998 and 2007 found that traffic pollution may be associated with a 5% to 15% increase in the likelihood of some cancers.<ref>{{cite news | url = http://health.usnews.com/health-news/news/articles/2013/04/09/smog-exposure-during-pregnancy-might-raise-childs-cancer-risk-study | title = Smog Exposure During Pregnancy Might Raise Child's Cancer Risk: Study | date = 9 April 2013 | first = Steven | last = Reinberg | newspaper = USNews}}</ref> A [[World Health Organization]] study found that diesel fumes cause an increase in lung cancer.<ref>{{cite web|url=https://www.iarc.who.int/news-events/iarc-diesel-engine-exhaust-carcinogenic/|title=IARC Diesel engine exhaust carcinogenic |website=iarc.fr|access-date=18 June 2023}}</ref>

The [[California Air Resources Board]] found in studies that 50% or more of the [[air pollution]] ([[smog]]) in [[Southern California]] is due to car emissions.{{Citation needed|date=April 2010}} Concentrations of pollutants emitted from combustion engines may be particularly high around signalized intersections because of idling and accelerations. Computer models often miss this kind of detail.<ref name="Int Panis1">{{cite journal | last = Int Panis L| title = Modelling instantaneous traffic emission and the influence of traffic speed limits | journal = Science of the Total Environment | volume = 371 | issue = 1–3 | pages = 270–285 | year = 2006 | doi =10.1016/j.scitotenv.2006.08.017 | pmid = 17049967 |display-authors=etal| bibcode =2006ScTEn.371..270I}}</ref>

== See also == {{Div col|small=no}} * [[Alternative propulsion]] * [[Atmospheric dispersion modeling]] * [[Automobile#Environmental impact]] * [[Clean Air Act (United States)|Clean Air Act]] * [[Congestion pricing]] * [[Emission standard]] * [[Environmental effects of transport]] * [[European emission standards]] * [[Exhaust gas analyzer]] * [[Flue gas]] * [[Kyoto Protocol]] * [[Landfill gas]] * [[List of most-polluted cities by particulate matter concentration]] * [[Low-emission zone]] * [[Mobile source air pollution]] * [[Motor vehicle emissions and pregnancy]] * [[Rolling coal]] * [[Space jellyfish]] * [[United States emission standards]] * [[Vehicle emissions control]] {{Div col end}}

==References== {{reflist}}

==External links== * [http://www.arb.ca.gov/research/health/health.htm Health and Air Pollution] Publication of the [[California Air Resources Board]] * {{cite news | url = http://www.huffingtonpost.com/2008/11/13/california-air-pollution-_n_143521.html | title = California Air Pollution Kills More People Than Car Crashes, Study Shows | first = Tracie | last = Cone | date = 13 November 2008 | newspaper = Huffington Post}} * {{cite web | url = http://www.nutramed.com/environment/carschemicals.htm | title = Automotive Exhaust Chemicals: disease causing effects | work = Alpha Online | publisher = Environmed Research Inc. | archive-url = https://web.archive.org/web/20140705211720/http://nutramed.com/environment/carschemicals.htm | archive-date = 2014-07-05 }} * {{cite web | url = http://www.ucsusa.org/clean_vehicles/vehicle_impacts/cars_pickups_and_suvs/cars-trucks-air-pollution.html | publisher = Union of Concerned Scientists | title = Cars, Trucks, and Air Pollution | date = 3 September 2013 | work = Clean Vehicles}} * About diesel exhaust: ** [https://www.osha.gov/SLTC/dieselexhaust/ U.S. Department of Labor Occupational Safety & Health Administration: Safety and Health Topics: Diesel Exhaust] ** [https://www.osha.gov/SLTC/dieselexhaust/chemical.html Partial List of Chemicals Associated with Diesel Exhaust] ** [https://web.archive.org/web/20051031101139/http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s069dies.pdf Diesel Exhaust Particulates: Reasonably Anticipated to Be A Human Carcinogen] ** [http://ajrccm.atsjournals.org/cgi/content/full/159/3/702 Scientific Study of Harmful Effects of Diesel Exhaust: Acute Inflammatory Responses in the Airways and Peripheral Blood After Short-Term Exposure to Diesel Exhaust in Healthy Human Volunteers] ** [https://web.archive.org/web/20080414094408/http://www.losh.ucla.edu/catalog/factsheets/diesel_english.pdf Diesel exhaust: what you need to know]

[[Category:Air pollution]] [[Category:Engines]] [[Category:Gases]] [[Category:Smog]] [[Category:Transport and the environment]] [[Category:Pollution]]