Canada on Friday banned cruise ships from dumping sewage and dirty water close to shore, and said it would impose fines of up to C$250,000 ($190,000) for offending vessels.
A range of anti-pollution measures introduced on a voluntary basis in April 2022 will become obligatory with immediate effect, Transport Minister Omar Alghabra said in a statement.
Environmental groups said Ottawa had ignored the largest source of liquid pollution from cruise ships: the water used to clean exhaust gas cleaning systems, or scrubbers, that remove sulfur from ships' fuel.
"Cruise ships are an important part of our economy and tourism sector, but they need to operate in a more sustainable manner," Alghabra said. Cruise ships generate more than C$4 billion a year for the economy, he added.
The rules ban the discharge of sewage and so-called greywater - the drainage from sinks, laundry machines, bathtubs and showers - within three nautical miles of Canadian shores.
Additionally, ships in non-Arctic waters will have to strengthen the treatments of sewage and greywater dumped between three and 12 nautical miles from shore. Separate rules regulate cruise ship pollution in Arctic waters.
Environmentalists say cruise ships traveling to and from Alaska alone dumped 31 billion liters (8.2 billion U.S. gallons) of inadequately treated pollution into Canada's Pacific waters in 2019.
In statements, the West Coast Environmental Law and stand.earth green groups both welcomed Alghabra's announcement but called for regulations on scrubber water, which accounts for over 90% of the liquid waste from cruise ships. Activists say it is particularly acidic.
They also called for inspectors to be put on board vessels.
A spokeswoman for Alghabra said the government would work with the shipping industry to find a feasible way of reducing or eliminating discharge of scrubber water.
($1 = 1.3199 Canadian dollars)
(Reuters - Reporting by David Ljunggren; Editing by Richard Chang)