This kind of journalism is the worst. Take something large but relatively uncommon and then talk about how much of this or that it emits. Perhaps we should kill all elephants since they proportionally do a lot of damage to nature and emit greenhouse gasses. FYI- ant respiration emits more CO2 than humans by many orders of magnitude.
Rain will wash the pollutant out of the air, and most of the polluting is out in the oceans anyhow- away from cities.
From
Wiki-
The following amount of sulfur dioxide was released in the U.S. per year, measured in thousands of short tons:
1970 31,161
1980 25,905
1990 23,678
1996 18,859
1997 19,363
1998 19,491
1999 18,867
Have these cargo ship emissions been shown to cause any specific problem?