International Cooperation

Reducing Air Pollution from International Transportation

Transportation of goods across air, sea and land presents economic opportunities, and also creates significant environmental challenges, including from criteria air pollutants and greenhouse gases. EPA is working with our international partners to reduce the environmental impacts of rapidly increasing international trade.

Growth of International Trade and Transportation

2012 International Trade Contributions to GDP
(For top 10 International Economies by GDP)
Rank Country GDP
(millions, USD)
as %
1 United States 16,244,600 24.75
2 China 8,227,103 47.00
3 Japan 5,959,718 28.26
4 Germany 3,428,131 75.73
5 France 2,612,878 47.56
6 United Kingdom 2,471,784 47.17
7 Brazil 2,252,664 21.12
8 Russian Federation 2,014,775 42.92
9 Italy 2,014,670 48.98
10 India 1,841,710 42.49

Source: World Bank, World Development Indicators Database

The trade of goods, finance, information and people among the world’s economies is not new. But in recent decades the international flow of trade and finance has grown to unprecedented levels and become essential to the world economy. The economic emergence of developing countries (such as Brazil, China and India) has dramatically increased global trade flows overall and also shifted the balance of international trade flows between developed and developing countries.

Since 1950, world trade has increased over 20-fold (by value), far exceeding the growth rate for population or GDP. [1] In the United States, the trade-to-GDP ratio (a measure of the share of total GDP made up of international trade) increased from 20.5% in 1990 to 28.7% for 2006-2008, and it is estimated that it could increase to almost 55% of GDP by 2038. [2]

When goods are traded internationally, they can be moved over water, air or land. The transport choice depends on the geographic proximity of the trading partners, characteristics of the product to be transported, the relative costs of competing transport modes, and other key facilitating services such as communications.

  • Seaborne transportation carries the majority of all goods traded internationally. Since the 1970s, seaborne trade has grown 4% each year.
  • Aviation, the dominant mode of international passenger transportation, is also a critical provider of rapid transportation for high-value and/or time-sensitive goods. Since 1970, the volume of cargo sent by air has grown 9% each year.
  • In the case of neighboring countries, notably nations in Europe and North America, land-based modes (e.g. trucking, rail, pipelines) also move very large volumes of goods in trade.

Top of Page

Reducing Air Pollution from International Transportation

Because of their reliance on petroleum-based fuels and their dramatic growth rates in recent decades, air and sea transport are responsible for significant emissions of both traditional (criteria) air pollutants (e.g. sulfur oxides (SOx), nitrogen oxides (NOx)) and greenhouse gases (e.g. carbon dioxide (CO2)). International seaborne and airborne transportation are estimated to produce perhaps more than 7% of total global CO2 emissions from the combustion of fossil fuels at present. [3] But compared to other transport modes, these have few options for transitioning to other fuels in the near- to medium-term.

U.S. International Merchandise Trade by Transportation Mode: 2011
Mode Billions of U.S. Dollars
Total trade Exports Imports
Water 1,729 570 1,159
Air 918 425 493
Truck 626 323 303
Rail 152 54 97
Pipeline 81 10 71
Other and unknown 46 30 15
Total, all modes 3,551 1,412 2,139
Mode Millions of Short Tons
Total trade Exports Imports
Water 1,480 631 849
Air 8 4 4
Truck 208 119 89
Rail 142 62 80
Pipeline 123 16 107
Other and unknown 13 5 8
Total, all modes 1,974 837 1,137

Notes: 1 short ton = 2,000 pounds. The U.S. Department of Transportation (USDOT), Research and Innovative Technology Administration, Bureau of Transportation Statistics estimated 2011 weight data for truck, rail, pipeline, and other and unknown modes using value-to-weight ratios derived from imported commodities. Totals for the most recent year differ slightly from the USDOT, Federal Highway Administration, Office of Freight Management and Operations, Freight Analysis Framework (FAF) due to variations in coverage and FAF conversion of values to constant dollars. Numbers may not add to totals due to rounding. See figures, sources, excel format and full information from the United States Department of Transportation.

EPA, industry, and other entities in the U.S. and abroad have taken a number of regulatory and voluntary steps to reduce domestic emissions from maritime shipping and aviation. These efforts have resulted in some emissions reductions here and abroad. However, because of the very nature of these transportation modes (operating largely outside of national boundaries), domestic actions alone cannot control the energy consumption of, or emissions from, these sectors.

Reducing traditional "criteria" air pollutants (e.g., NOx, SOx, PM): Working internationally, the U.S. and other countries have established stringent marine fuel quality and engine emissions standards for international shipping under the auspices of Annex VI of the IMO’s International Convention for the Prevention of Pollution from Ships  (MARPOL). By acting through the IMO, the specialized agency for maritime affairs within the United Nations system, we have achieved dramatic reductions in maritime emissions of criteria air pollutants, while avoiding distortions or disruptions of international trade flows.

Reducing greenhouse gas emissions (GHGs) and saving energy:  In recent decades, industry and government have managed to improve the energy efficiency of ships and airplanes to a considerable degree.  This has been driven by many factors, including the improvements in efficiencies of scale associated with the increasing size/capacity of ships and airplanes, and a desire to address rising fuel prices.  EPA, other governmental entities, and key industry players have been working on this via internal development of new technologies, voluntary partnerships, and coordinated action undertaken in the technical agencies responsible for international maritime and aviation matters within the United Nations system: the IMO and the International Civil Aviation Organization (ICAO).  However, there remains considerable potential for using technical and operational measures to further reduce energy consumption (and thus, emissions) from both ships and airplanes.

Even so, technical and operational measures alone will not be sufficient to reduce the GHG emissions from international transportation in light of long-term projections for world trade and the overall emission reductions required to stabilize climate.  [4]  The overall growth in international transportation-related emissions will more than offset any emissions reductions resulting from transportation industry efficiency improvements.  [5]  

As the IMO framed the situation for the Rio+20 Conference in 2013, “In 2007 international shipping is estimated to have contributed about 2.7% to the global emissions of carbon dioxide (CO2).  If climate is to be stabilized at no more than 2oC warming over pre-industrial levels by 2100 and emissions from shipping continue as projected, then they would constitute between 12% and 18% of the total CO2 emissions in 2050 that would be required to achieve stabilization by 2100.  

The growth of world trade in the future represents a challenge to meeting a target for emissions requred to achieve stabilization in global temperatures and so IMO continues to work on the development of market-based measures as a complimentary means of achieving the required target for emissions.” [6] This conclusion holds even after accounting for the global economic downturn that began in late 2008.  Thus, the U.S. is partnering internationally to establish binding, globally-applicable policies to limit emissions from these transport sectors while avoiding undesirable trade distortions or constraints.

Top of Page

Additional Resources

Top of Page

References cited on this page:

  1. International Transport Forum (ITF), Transport for a Global Economy: Policy Reflections from the Secretariat, ITF Forum 2009, 26-29 May 2009.
  2. IHS Global Insight, An Evaluation of Maritime Policy in Meeting the Commercial and Security Needs of the United States, January 7, 2009.
  3. by the International Maritime Organization (IMO), International Civil Aviation Organization (ICAO) and other entities
  4. David McCollum, Gregory Gould and David Greene, Greenhouse Gas Emissions from Aviation and Maritime Transportation: Mitigation Potential and Policies, prepared for the Pew Center on Global Climate Change, December 2009.
  5. Buhaug et al.  Second IMO GHG Study 2009.  International Maritime Organization, London, UK.  April 2009 
  6. IMO, Air Pollution and Greenhouse Gas (GHG) Emissions from International Shipping, IMO at Rio+20. (PDF) Exit


For additional information on EPA's International Trade efforts, contact:

Joe Ferrante
U.S. Environmental Protection Agency
Office of International and Tribal Affairs (2670R)
1200 Pennsylvania Ave., NW
Washington, DC 20460