Big ships, big business.

Cruise liners bring holidaymakers and their money to destinations all over the world ...

But may no longer be welcome in one of the most famous ...

Cannes in the south of France is to ban the environmentally dirtiest ships from next year.

Local mayor, David Lisnard.

"SOUNDBITE) (French) CANNES MAYOR, DAVID LISNARD, SAYING:

"It's not about being against cruise ships. It's about being against pollution."

Down the coast at Nice is Atmosud.

Here they measure local air quality ...

While site manager Florence Perron explains the background to the new restrictions.

(SOUNDBITE) (French) NICE SITE MANAGER OF AIR QUALITY MONITORING AGENCY ATMOSUD, FLORENCE PERRON, SAYING:

"There's a European directive that aims to limit the sulphur content of fuel used by the ships, especially during high emission periods, meaning when they are docked or when they are manoeuvring to enter or exit the port. So, this level should be reduced to 0.1 percent in sulphur so as to limit emissions of sulphur dioxide."

In fact, cruise ship fuel can contain two thousand times more sulphur oxide than ordinary diesel, according to expert analysis.

One major cruise operator - Norwegian Cruise Lines - has signed a charter with the city, promising to make to be more environmentally friendly.

And another, Silversea, is taking steps, says boss Robert Martinoli.

(SOUNDBITE) (English) SILVERSEA CRUISES CEO, ROBERT MARTINOLI, SAYING:

"This year at the end of the summer, we will go into our maintenance cycle, so the ship will be out of service for two or three weeks, and we will implement the changes to the engines to make them comply with the latest environmental regulations."

But the industry may have a race on its hands to catch up with its own rapid growth.

The main trade association expects 30 million passengers to cruise on almost 300 ships this year, nearly twice the volume of a decade ago.