Nowadays, Christmas arrives by ship not sleigh. The labels of our new Christmas jumpers, novelty socks, toys and mobile phones reveal the global trade in manufactured goods and the huge distances they travel.
Shipping is more energy efficient than road or air transport, but a lack of controls on ship exhausts and the poor quality of marine fuel mean 15% of global nitrogen oxides and 8% of sulphur gaseous pollution come from ocean-going ships.
This matters because 80% of shipping is within 400km of land, and major sea corridors and ports are large pollution sources. In Hong Kong, the world’s fourth largest port, daily changes in ship pollution have been linked to heart attack frequency. Ship pollution can also be found in smaller port cities such as Cork, Gothenburg and Brisbane.
Marine fuel is mainly residues from refining road and aviation fuel, and therefore contains most of the impurities. Vanadium emitted from ship funnels can be found in the air throughout Europe – in Paris and London, for example. But the greatest impact of shipping pollution in Europe is felt in Denmark and the Netherlands.
Much of waters around the US and Europe are now pollution control zones for ships, requiring them to burn better quality fuel. This does help. Reduced sulphur in fuel from 2006 led to cleaner air in Dover and Rotterdam.
However, growth in shipping and increasingly stringent controls on land-based pollution sources mean ship pollution is set to grow as a proportion of our pollution exposure.