Sea Transport: The Forgotten Air Pollution

Eighty percent of the goods transported worldwide takes place by sea, generating 13% of annual nitrogen oxide (NOx) emissions and 12% of sulfur oxide (SOx) emissions, among others. Yet it receives little research and policy attention.

Although 80% of the world's goods are transported by sea (which explains the rapid expansion of international trade today), there are many more studies on air pollution from road transport than from shipping. Emissions from sea transport have increased in recent decades, as have those from aviation. This is why three ISGlobal researchers set out to review 32 studies assessing the health burden of shipping-sourced air pollution, including docked ships and port activities.

Every year, 10 billion tonnes of cargo are moved by sea, accounting for about 3% of global greenhouse gas emissions, 13% of nitrogen oxide (NOx) emissions and 12% of sulphur oxide (SOx) emissions. Maritime transport also emits other pollutants that are harmful to human health, such as particulate matter and black carbon.

For all these reasons, it is estimated that it could have caused some 265,000 premature deaths worldwide in 2020. In other words, 0.5% of global mortality would be linked to emissions from sea transport.

And that's not all: by 2050, global demand for maritime trade is expected to grow by 40%.

Every year, 10 billion tonnes of cargo are moved by sea, accounting for about 3% of global greenhouse gas emissions, 13% of nitrogen oxide (NOx) emissions and 12% of sulphur oxide (SOx) emissions

Pollution from Sea Transport Mainly Affects Europe

Air pollution from shipping is a universal problem that knows no borders, but it particularly affects coastal populations, especially European ones, which, unlike Asian ones, are located very close to the busiest shipping routes.

For this reason, most research to date has focused on European seas, especially the North Sea and the Baltic Sea. However, there is a lack of data on the impact on South America, Africa, the Middle East and other populations along major shipping routes (such as the one connecting Asia with Europe via the Red Sea, the Suez Canal, the Mediterranean and the Strait of Gibraltar).

Air pollution from shipping is a universal problem that knows no borders, but it particularly affects coastal populations, especially European ones

What Is the World Doing to Control Shipping Emissions?

In 2005, the International Convention for the Prevention of Pollution from Ships (MARPOL) of the International Maritime Organization (IMO) came into force. Its Annex VI establishes certain standards and emission control areas for sulphur oxides (SOx) and nitrogen oxides (NOx). The standards are mandatory for UN member states and include measures such as the use of cleaner fuels, wind-assisted ship propulsion (WASP), offshore electricity or other technological innovations.

Rotterdam. Photo: Frans Berkelaar / Flickr.

The IMO has committed to a 50% reduction in greenhouse gas emissions by 2050 compared to 2008 levels, but this will only be achieved through significant investment by shipowners to design more efficient ships (e.g. running at lower speed) and the widespread adoption of liquefied natural gas and biofuels, wind power and electrification.

It is estimated that it could have caused some 265,000 premature deaths worldwide in 2020. In other words, 0.5% of global mortality would be linked to emissions from sea transport

In practice, compliance with IMO regulations is expensive, while penalties and the likelihood of an on-board inspection are low, not to mention the fact that there is no authority to monitor compliance outside territorial waters.

More restrictive measures and the extension of emission control areas should be considered. For example, it has been suggested that the use of heavy fuels should be prohibited when ships are near ports and population centers. Regulations for ships at berth could also be tightened, but this depends on national government legislation.

More restrictive measures and the extension of emission control areas should be considered. For example, it has been suggested that the use of heavy fuels should be prohibited when ships are near ports and population center

As a positive trend, shore-side electrification has increased, with major ports in the European Union, for example, required to supply shore-side electricity by the end of 2025.

In summary, our study places shipping as a major source of global air pollution and a health risk factor that needs greater policy and research attention, as well as even more stringent emission control efforts.