Levels of pollution on some cruise ships’ decks are worse than in the world’s most polluted cities, an investigation by Channel 4 Dispatches has found. 

The undercover investigation on Britain’s biggest crew operator P&O Cruises aimed to find out how clean the air holidaymakers breathe when on a ship is. 

It focused on the levels of “ultra-fine particles” found in the air and around the cruise ship and emitted from the fuel the ships’ engines burn. 

But while passengers hope to escape the dirty air of cities for some fresh sea air, the investigation found cruise ships are having a negative impact on the environment. One cruise ship can emit as much particulate matter as a million cars in a day. 

Meanwhile cruise ships are becoming more popular with around two million people from the UK travelling on one every year.

By using a P-Trak ultra-fine particle counter, Dispatches said it was able to measure the levels of the ultra-fine particulates on board the P&O Cruises’ ship Oceana, which can carry more than 2,000 passengers. 

The device found that the air on the deck downwind of, and directly next to the ship’s funnels, had 84,000 ultra-fine particulates per cubic centimetre. 

Directly next to the funnels on the deck, the numbers rocketed to 144,000 with a peak at 226,000. 

This is more than double the average found in central London’s Piccadilly Circus, where using the same device, the Dispatches team recorded 38,400 ultra-fine particulates per cubic centimetre. 

While the deck is popular with sun-bathers, passengers are likely to be breathing some of these particulates, which are harmful for health and the environment. 

Speaking to Dispatches, Dr Matthew Loxham said: “It is clear from those results that there are certain areas of the ship that are affected by quite high levels of particulate matter. 

“These are levels that you would expect to see in the most polluted cities in the world like Shanghai, Delhi and so on.”​

Looking at the results, Dr Loxham also said the findings suggested the majority of the particulates were coming directly from the ship’s funnels. 

He said: “Short term exposure can cause increasing respiratory symptoms. People who are asthmatic for example, that might give them a wheeze. Similarly for people with cardiovascular disease. Now that is not to say that these levels of particulates on this ship are going to do that but there is much evidence out there to suggest that increase levels of particulates can cause these symptoms.” 

Dr Loxham added that crew members working on the ship and who experienced repeated exposure could experience symptoms “that we are just starting to understand”. 

Speaking to the Dispatches team, Daniel Rieger, of the German environment association NABU (Nature And Biodiversity Conservation Union), said: “Ships cause not only greenhouse gas emissions, but also sulphur oxides, nitrogen oxides and particulate matter.

“Per day one cruise ship emits as much particulate matter as a million cars. So 30 cruise ships pollute as much as all the cars in the United Kingdom.”