Arriving in Dublin by ferry, you might expect a breath of fresh sea air. You’d be getting something else. Dublin’s ferry port is the most polluted in Europe, a recent analysis found. In Ireland's capital, ferries emit 16 times more sulfur oxides (SOx) than all the city’s cars combined.
Most people are familiar with the harmful effects of CO2, but far fewer know about the risks posed by SOx. While it does not contribute to global warming, it is highly toxic and severely degrades air quality, causes acid rain, and harms human health. Even at low concentrations, chronic exposure to SOx can lead to the development of respiratory and cardiovascular diseases.
The problem is common to ports across Europe. Studies show that maritime transport can contribute up to a quarter of the annual concentration of SOx and other air pollutants in coastal areas. In 2022, shipping emitted 88% of all sulfur dioxide produced by EU transport.
Most European passenger ferries are older than first smartphones. On average, they are 26 years old and run mostly on fossil fuels. Only 7% of the European fleet is hybrid, running on fossil fuel and electricity, and just 2% are fully electric.
Ships pollute the most during docking and departure, which last between 5 and 35 minutes. It doesn't stop there. When at berth, ships turn their main engine off, but switch on backup generators to keep power on. According to a study of Dublin port emissions, pollution from a single ship can linger for up to 2.5 hours after it docks in the port.
Those improvements are largely thanks to stricter emissions rules for ferries and ships. SECAs – Sulfur Emission Control Areas – are sea areas where air quality is more strictly controlled, specifically in relation to ship emissions. In these areas, ships are restricted to fuel with a sulfur content of 0.1%, compared to 0.5% elsewhere.
The first one came into effect in the Baltic Sea in 2006. Four years later came the European North Sea SECA. The Mediterranean SECA, approved in 2025, is expected to contribute to further reductions.
The real game changer is now in preparation. The North-East Atlantic Emissions Control Area, the largest of its kind in the world, is expected to cut SOx emissions across the region by 82%. After it's fully implemented in 2028, it will also include Dublin. With that, the Irish capital will finally be able to take a breath of fresh air.