The data were gathered during the CalNex 2010 field study organized by ARB and the National Oceanic and Atmospheric Administration (NOAA).

The California data were compared to ship-plume measurements made by NOAA near the Port of Houston, Texas in 2006. One finding was that container ships encountered off the Port of Houston, where no clean-fuel use is required, emitted four times as much sulfur dioxide.

Ships, especially ocean-going vessels, are powered by very large diesel engines that generate a tremendous amount of pollution impacting air quality onshore. For some coastal counties in California, ships are the largest source of sulfur dioxide pollution.

CalNex 2010 was supported by three aircraft, a research vessel and dozens of researchers on the ground to measure atmospheric pollution levels.

NOAA researchers on the ship Atlantis focused on various sources of emissions, air quality and meteorology along the California coast and in the San Francisco Bay. The 274-foot research vessel examined the composition of emissions from more than 70 passing ships over 24 days. The researchers also found that every ship in California waters whose emissions were measured was using low-sulfur fuel.

More findings from the CalNex research on a variety of subjects, from the formation of ozone to the interactions of particles and clouds, are being presented at a four-day workshop May 16 through 19 in Sacramento, California.

The 2008 ocean-going vessel (OGV) fuel-use regulation requires all ocean-going vessels within 24 nautical miles of California's coastline use cleaner-burning diesel fuel to reduce emissions of sulfur oxides, nitrogen oxides and diesel particulate matter, a known carcinogen. Since the regulation began implementation in 2009, ships have made more than 18,000 visits to California ports using the lower-sulfur marine distillates rather than the highly polluting heavy-fuel oil, often called bunker fuel.