Which emissions are controlled by Annex VI?

• A. CO2
• B. NOx and SOx
• C. O2
• D. CH4

Answer: (B)

Annex VI targets pollutants that affect local air quality from ships: nitrogen oxides (NOx) and sulfur oxides (SOx). NOx forms in the high-temperature combustion inside ship engines, so the regulation sets engine emission limits that vary by engine type and era to reduce smog, respiratory problems, and ozone formation. SOx comes from sulfur in the fuel; when burned it creates sulfur dioxide and related acidic compounds, which is why there are global sulfur content caps for fuel and stricter limits in certain emission control areas, sometimes supplemented by scrubbers.

CO2 and CH4 are greenhouse gases addressed by broader climate and energy-efficiency efforts rather than Annex VI, and oxygen is not an emission regulated in this context. This is why the focus of Annex VI is on NOx and SOx.