Globally air pollution from ships is regulated by IMO MARPOL Annex VI on "Regulations for the Prevention of Air Pollution from Ships". Annex VI MARPOL provides for the designation of emission control areas (ECAs), where standards exceeding global requirements apply.
HELCOM has been the regional platform for negotiating submissions to IMO aiming for designating Baltic Sea as a MARPOL ECA in terms of SOx (negotiated 1993-1997, submitted to and adopted by IMO in 1997) and NOx (negotiated 2007-2013, pending submission to IMO).
According to currently valid Annex VI of MARPOL the Baltic Sea is a SOx emission control area where (from January 2015) the sulphur content of any fuel oil used onboard ships within the Baltic Sea has to be 0.1 % or less.
Nitrogen emissions from NOx in ship exhaust gases worsen the nutrient pollution problem of the Baltic Sea, also called eutrophication. Shipping is among the largest sources of airborne NOx ending up in the Baltic Sea, e.g. more important than the combined airborne NOx load from on-land sources in Sweden.
Sulphur, emitted from ships as Sulphur oxides (SOx) in exhaust gases, is not as important pollutant for the status of the Baltic Sea marine environment as it is for inland nature and human health. This is due to the high buffering capacity of seawater which protects it from acidification.
However, it is indirectly very relevant as implementation of SOx regulation ("SECA") is a catalyst for mainstreaming innovative green technologies and alternative fuels such as Liquefied Natural Gas (LNG) which influence also NOx emissions.
In addition to SOx and
NOx, shipping is also contributing to the emissions of particulate matter and greenhouse gases (mainly
CO2) but as these have been perceived as global, not regional, issues they have so far not been the focus of HELCOM work.