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.

英国第四频道《深入报道》节目调查发现，邮轮甲板上的空气污染程度超过了世界上污染最严重的城市。

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.

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.