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Green Vehicle Guide

Light Duty Vehicle Emissions

emissions from vehicleCars, SUVs, and light duty trucks that are fueled by gasoline, diesel, and E85 emit both greenhouse gases and smog-forming pollutants from their tailpipes.


Greenhouse Gas Emissions

  • Greenhouse gases (GHGs) are emitted from the tailpipes of cars and trucks that combust fuel. 
  • Once GHGs are released, they can stay in the atmosphere for 100 years or more.
  • GHGs act like a blanket around Earth, trapping energy in the atmosphere and causing it to warm.  This can change Earth's climate, raise sea levels, and result in dangerous effects to human health and welfare, and to ecosystems.
  • The effects are global.

Smog Forming Emissions

  • Cars and trucks that combust fuel also emit smog forming emissions, such as nitrogen oxide, non-methane organic gases, carbon monoxide, particulate matter, and formaldehyde.
  • These emissions are usually trapped close to the ground, and can form a brownish haze that pollutes our air, particularly over cities in the summertime.
  • Smog can make it difficult for some people to breathe, triggering lung diseases such as asthma, emphysema, and chronic bronchitis.
  • The effects are local, regional, and national.

Electric and hydrogen fuel cell vehicles do not produce tailpipe emissions. Emissions that are related to the production of the fuel used to power vehicles are known as “upstream” emissions. Visit our Beyond Tailpipe Emissions Calculator for specific information on upstream emissions from electric vehicles.

Environmental Ratings on the Label

GHG and Smog ratings on fuel economy labelWe rate greenhouse gas (GHG) and smog forming emissions separately on the fuel economy label because they represent different pollutants that affect different layers in our atmosphere. The GHG rating reflects carbon dioxide (CO2) emissions. CO2 makes up roughly 99% of the total greenhouse gases emitted from the tailpipe. The smog rating reflects the current federal emission standards, which cover:

  • NMOG, NMHC, or THC—types of carbon-containing compounds, including hydrocarbons 
  • NOx—Oxides of Nitrogen, which combine with hydrocarbons to create smog 
  • PM—Particulate Matter, tiny particles of solid matter that lodge in the lungs and deposit on buildings 
  • CO—Carbon Monoxide, a colorless, odorless, poisonous gas 
  • HCHO—Formaldehyde, a lung irritant and carcinogen 

The Good News...


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