Challenges related to air pollution from cruise ship engines are cropping up elsewhere in the world, even as they’ve been overcome for now in waters around North America.

In Australia, a newly elected government ran in part on a pledge to reduce the amount of sulphur coming from cruise ship smoke stacks to the same low level as in the U.S. and Canada.

Meanwhile in Europe, some regulators are asking whether a popular solution to reducing sulphur emissions — exhaust gas scrubbers — might contribute to water pollution in some areas.

The issues are percolating because of a worldwide effort to cut pollution from ship engines, which rely on oil particularly high in sulphur.

Since Jan. 1, all ships, including cruise vessels, have had to meet a much-reduced standard for sulfur in North America and certain other regions such as the Baltic Sea.

The standard, which remains 3.5% of fuel volume in much of the world, was reduced to 0.1% in so-called Emission Control Areas (ECAs). The change will prevent 14,000 early deaths annually by 2020, according to estimates from the U.S. Environmental Protection Agency (EPA).

Now Australia is seeking parity with the U.S. In late March, voters retained the New South Wales state government led by premier Mike Baird, who campaigned on a pledge to reduce the sulphur content of fuel for cruise ships in Sydney to 0.1% by July 2016.

Such quick action could disrupt Australia’s cruise sector, which has been growing by leaps and bounds.

Bud Darr, senior vice president of technical and regulatory affairs at CLIA, said the industry is “directly and actively engaged” with New South Wales authorities and the Australian EPA on air pollution issues.

“We are exploring a range of possibilities with those authorities,” Darr said in a statement. “We encourage those officials to take into account operational considerations and the results of a science-based study they have commissioned before taking any unilateral actions locally or nationally.”

Globally, the framework for air pollution control is set by the International Maritime Organization (IMO). Sulfur standards are scheduled to drop to 0.5% worldwide in 2020.

Countries can act earlier by setting up ECAs, such as the one formed jointly by the U.S. and Canada. The CLIA statement noted that so far Australia has chosen not to create an ECA.

Because of the expense and time involved in the installation of scrubbers — Carnival Corp. is currently installing scrubbers on 70 of its ships in a three-year project that will cost $400 million — the cruise industry has focused on installing scrubbers for ships with ECA itineraries, not those sailing in non-ECA areas such as Australia.

Darr said that the sulphur content of fuel has been on the decline and in most cases is below 3.5%. He said in Australia, which imports all of its marine fuel, indications are that the content is about 2.5%.

In the past, ships were powered with “residual” fuel left over from distillation of refined products such as gasoline, leaving behind oil with particularly high sulphur levels.

In addition to using more refined fuel, ship owners have turned to exhaust gas scrubbers.  Carnival Corp. and Royal Caribbean Cruises Ltd. are among the companies that have won permission from the EPA to meet lower sulphur standards by scrubbing it from engine exhaust.

The scrubbers generally fit in a ship’s smokestack and use either seawater or fresh water augmented with alkaline to create a chemical reaction that transfers the sulphur from air to water.

The water is then treated and discharged. It can also be recirculated with a smaller discharge amount. The treated water is generally more acidic than seawater, although tests have mostly shown it to fall within parameters set by the EPA.

But some worry that the water, if discharged in certain vulnerable areas such as ports, estuaries and coastal waters, could harm marine life and otherwise disrupt the environment.

Regulators in some European countries have questioned whether discharging scrubber wash water can be reconciled with the European Union’s “Water Framework Directive,” which gives local jurisdictions say over water matters in their areas.

A group of ship owners last year petitioned the EU for clarity, saying the uncertainty over enforcement jeopardizes their investment in scrubbers as a solution to lowering sulfur emissions.

In its statement, CLIA said about one-third of ships operated by its members have either installed scrubbers or committed to do so.

In January, many EU states submitted a plan to the IMO to create an alternate standard for verifying the acidity of washwater. CLIA said it endorsed the proposal, which is set to go before the IMO’s Marine Environmental Protection Committee in May.

CLIA added that the IMO global standards should be the ones used by individual governments to fully encourage development of the new technology.