Learn about smog, soot, ozone, and other air pollution, as well as EPA programs to reduce them.
- About smog, soot, and other air pollution from transportation
- Programs to reduce smog, soot, and other air pollution from transportation
- Resources for state and local agencies
What is smog?
The term “smog” was first used around 1950 to describe the combination of smoke and fog in London. Today, it refers to a mixture of pollutants made up mostly of ground level ozone.
Air pollution emitted from transportation contributes to smog, and to poor air quality, which has negative impacts on the health and welfare of U.S. citizens. Pollutants that contribute to poor air quality include particulate matter (PM), nitrogen oxides (NOx), and volatile organic compounds (VOCs).
- Over 55% of NOx total emissions inventory in the U.S.
- Less than 10% of VOCs emissions in the U.S.
- Less than 10% of PM2.5 and PM10 emissions in the U.S.
(NOTE: This value does not account for the substantial amount of PM that is formed in the atmosphere from gaseous mobile source emissions)
(Reference: Multi-Pollutant Comparison)
The transportation sector also contributes to emissions of air toxics, which are compounds that are known or suspected to cause cancer or other serious health and environmental effects. Examples of mobile source air toxics include benzene, formaldehyde, and diesel particulate matter.
EPA implements national programs and standards for fuels and vehicles that reduce air pollution including smog, soot, and toxic pollutants, and spur investments in clean vehicle and engine technology. EPA programs to reduce emissions from transportation sources have resulted in less smog and soot, significantly better air quality and better health for Americans. By 2030, EPA air quality emissions standards for vehicles are projected to annually prevent:
- 40,000 premature deaths
- 34,000 avoided hospitalizations
- 4.8 million work days lost
Passenger Vehicle Standards
Passenger vehicles are regulated by EPA under light duty vehicle programs. EPA set stringent emissions standards for passenger vehicles, as well as limits on the amount sulfur, a naturally occurring contaminant, in gasoline. Limiting sulfur in gasoline allows emissions reductions technologies like catalysts to be significantly more effective in reducing nitrogen oxides and other pollutants.
- Final rule for amendments related to tier 3 motor vehicle emission and fuel standards
- Gasoline fuel standards
EPA has a variety of standards to reduce emissions from heavy duty diesel vehicles and engines. These include standards for tractor-trailers, large buses, construction and agricultural equipment, diesel engines in boats and ships, and even locomotives. These standards have significantly reduced emissions of diesel exhaust and improved public health.
- Regulations for smog, soot, and other air pollution from commercial trucks & buses
- Regulations for emissions from heavy equipment
- Regulations for emissions from locomotives
- Regulations for emissions from marine vessels
National Clean Diesel Program
The Clean Diesel Program offers funding in the form of Diesel Emissions Reduction Act grants and rebates as well as other support for projects that protect human health and improve air quality by reducing harmful emissions from diesel engines. Between 2009 and 2013, almost 60,000 engines were retrofitted or replaced through our program. EPA estimates that these projects will result in $11 billion in health benefits from reduced air pollutant emissions over the lifetime of affected engines.
Freight transportation is a large contributor to air pollution and climate change. SmartWay helps the freight transportation industry improve supply chain efficiency to reduce air pollution from their operations. The three core elements of the Smartway Program include transport partnerships between shippers and carriers and the EPA, brand awareness of fuel-saving technologies, and global collaboration.
On March 26, 2010, the International Maritime Organization (IMO) designated coastal areas of U.S., Canadian and French waters as an Emission Control Area (ECA). Within the ECA, large ocean going vessels must adhere to stricter emissions and fuel standards resulting in significantly less air pollution being emitted.
The improvements to air quality that result from the North American ECA are expected to have large benefits to public health. By 2020 the ECA will prevent up to 14,000 premature deaths annually and reduce respiratory symptoms for nearly five million people each year in the U.S. and Canada.
The Ports Initiative is working to develop and implement environmentally sustainable port strategies through partnerships between EPA and ports. The program identifies opportunities to reduce air pollution and improve air quality in port communities, and reduce the carbon pollution that contributes to climate change while supporting jobs and the economy. EPA is supporting these efforts through a number of programs, including funding through the Diesel Emission Reductions Act.
EPA standards for transportation sources and voluntary programs have resulted in significant reductions in mobile source air toxic emissions. Mobile source hazardous air pollutants have been cut in half since 1990. With additional fleet turnover, EPA expects that emission to be cut by 80 percent by the year 2030.
To achieve the benefits of our regulations, EPA must ensure that the standards set for vehicles, engines and fuels are being met. One way EPA achieves this is by surveillance testing of cars, trucks and engines at our state-of-the-art National Vehicle and Fuel Emissions Laboratory. The laboratory also provides critical resource to accomplish the vehicle and engine testing work necessary to set vehicle and engine emissions standards and fuel standards.
In states and communities throughout the country, state and local leaders are seeking to balance their air quality, climate, and transportation goals. EPA provides useful information, tools, and links to resources that identify emission reduction strategies, national policies, regulations, incentive-based programs, funding sources, calculators, and other types of assistance to help states and local areas achieve their air quality and transportation objectives. This site also includes EPA regulations and guidance to support state I/M, fuel, and transportation conformity programs.