page_title: Exhaust gas
section_title: NOx
hierarchical_section_title: Exhaust gas / Main motor vehicle emissions / NOx
context_page_description: Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline, petrol, biodiesel blends, diesel fuel, fuel oil, 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, which can also include:
  Crankcase blow-by
  Evaporation of unused gasoline
  Motor vehicle emissions contribute to air pollution and are a major ingredient in the creation of smog in some large cities. A 2013 study by MIT indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions. 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.
context_section_description: Mono-nitrogen oxides 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 and colorectal cancer. and inhalation of such particles may cause or worsen respiratory diseases such as emphysema and bronchitis and heart disease.
  In a 2005 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.
  The resulting nitric acid may be washed into soil, where it becomes nitrate, which is useful to growing plants.
caption: Smog in New York City as viewed from the World Trade Center in 1988
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