In developed countries one of the few places where one can still see black smoke belching from chimneys and smokestacks is around the port.  According to the US Environmental Protection Agency:

• Ships are responsible for approximately 15% of all global anthropogenic nitrogen oxide emissions and approximately 4–9% of sulphur dioxide emissions.
• Ships also emit 1.8 million metric tons of PM10 (particulate matter which is 10 microns or less in diameter).
• Ocean-going ships were responsible for just under 3% of global CO2 emissions in 2007.

A newly published study from researchers at the University of California Riverside indicates that reducing the speed of ships by about 50% (from cruise at 25 – 29 miles per hour to 14 miles per hour) reduces emissions of carbon dioxide, nitrogen oxides, sulphur dioxide, and particulates per mile by substantially more than 50%.

The study focuses on ships in port areas, where air pollutants from ships are still a significant contributor to area air pollution, but the pollution reduction opportunities might provide some worthwhile opportunities for importers seeking to reduce the environmental footprint of their products.

The sample size for this study was small. As researchers routinely say, more study of this apparently worthwhile pollution reduction opportunity is needed.

The US EPA data on emissions from ships are at http://www.epa.gov/international/water/marine/ports.html

The study Greenhouse Gas and Criteria Emission Benefits through Reduction of Vessel Speed at Sea is at http://pubs.acs.org/stoken/presspac/presspac/abs/10.1021/es302371f    – abstract is free; full article requires subscription or payment.