Despite recent efforts from the cruise industry to cut down on emissions and decrease its impact on the environment, a new report has re-opened the debate on how much still needs to be done.

The study was published in February by the US Bloomberg School of Public Health in collaboration with campaigner group, and claimed to have found extremely high levels of air pollution on-board four different cruise ships.

With estimates suggesting that the shipping sector is responsible for 15% of nitrogen oxides and 8% of sulphur gas worldwide, the new document fuelled further outrage as it revealed a high concentration of particulate matter pollution, which it defined as ‘small solids or liquid droplets suspended in the air’.

Titled “An investigation of air pollution on the decks of 4 cruise ships”, it compared the results to the levels of pollution registered in cities like Beijing and Santiago.

Unsurprisingly, these figures were heavily challenged by Carnival Corporation – owner of the four ships investigated – which, together with other industry stakeholders, hit back at’s “inaccurate” and “ridiculous” report, claiming it had a poor scientific basis.

Worse than a bad day in Beijing

Although this is not the first report to challenge the industry’s environmental impact – nor the only one to be challenged – senior shipping campaigner Kendra Ulrich says its findings are of unprecedented magnitude.

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“We knew that this would be a very eye-opening report, but also one that was likely going to be questioned by the cruise sector,” she says.

For this reason, Dr Ryan Kennedy, the lead author of the report and assistant professor at Bloomberg School of Public Health, took extra precaution during his undercover investigations on the four ships.

“Dr Kennedy wanted to be sure to be very conservative in the assumption, giving a better understanding of what people might actually be exposed to.”

This meant collecting samples in three of the most crowded areas of a cruise ship – one in front and two in the back of it – for a period of 15-20 minutes while the ship was out at sea, therefore with reduced ambient pollution.

“The findings were shocking.”

Dr Kennedy also decided to release all the data he had so that it could be verified and reviewed independently (so far no independently verified results have been released). As such, the data collected remains open to contest.

The levels were measured on four different cruise ships belonging to Carnival Corporation, namely Carnival, Holland America Line and Princess Cruises.

“The findings were shocking,” Ulrich concludes. “In some instances, the air pollution in the back of the ship in places where people would be was as bad as, or worse, than a bad day in Beijing.”

Data from the report also showed high levels of harmful constituents, including metals and polycyclic aromatic hydrocarbons (PAHs), coming from ship exhaust.

These materials are toxic and cancerogenic, and, as Ulrich explains, may be particularly damaging for people spending a long time on-board. “They are certainly concerning for vulnerable passengers who maybe already have cardiovascular issues or asthma,” she says. “But in addition to that, it is the employees that are very much at risk.”

From restaurants to pools, bars and jogging grounds, many of a cruise ship’s bestselling amenities are placed on the open-air decks, meaning there is need for constant staffing to keep business moving.

“This report is very concerning for everyone,” continues Ulrich, “but certainly, for people that are working on the ships and have to be in those locations for their job, those levels of exposure are quite alarming over long periods of time.”

Carnival and CLIA strike back

Reaction from the industry was swift and virulent.

“These fake tests done on the fly under cloak and dagger – without proper scientific controls – are completely ridiculous, inaccurate and in no way represent reality,” said Carnival Corporation in a statement. “We regularly test the air quality of our ships in coordination with the proper authorities and they meet or exceed every requirement.”

Carnival further claimed that Dr. Kennedy did not recognise that one of the ships investigated was already running on MGO on multiple engines at the time, and that stack results gathered by the company during this timeframe did not correspond with the report’s findings.

“These fake tests are completely ridiculous, inaccurate and in no way represent reality.”

Further backlash came from global cruise industry trade association Cruise Lines International Association (CLIA), which stressed the sector’s ongoing environmental commitments deserve more acknowledgement.

“Cruise ships are one of the more high-profile and easy-to-target flashpoints when air pollution and emissions are discussed,” a company statement reads. “The cruise industry is only a small part of this issue, an issue which is facing the wider tourism and shipping sector; but we want to be a large part of the solution.

“Globally, the cruise industry has already invested $1bn in new technologies and cleaner fuels, to significantly reduce ships’ air emissions.”

Yet, Ulrich claims the sector’s response denies the existence of the issue, rather than looking for a way to tackle it: “The cruise industry does not want to acknowledge that there is air pollution on-board a ship,” she says, “and Carnival’s response was very defensive without providing any supporting evidence.”

The two sides go head to head

This ongoing exchange of conflicting opinions between the industry and campaigners adds fuel to the fire around wider debates regarding future environmental strategies in the sector.

On the one hand, CLIA and Carnival say that the industry is already putting considerable effort on decreasing its environmental impact, with much more to come. On the other, however, and other climate activists say these commitments risk outliving their purpose.

“ and other climate activists say the commitments risk outliving their purpose.”

“Looking ahead,” the statement from CLIA reads, “the industry has committed more than $8bn to construction of highly advanced liquefied natural gas (LNG) fuelled cruise ships, which will have lower emissions and higher energy efficiency.

“Other ships are powered by heavy fuel oil but use abatement technologies such as exhaust gas cleaning systems, air lubrication and itinerary planning to minimise their environmental impact.”

In line with these words is Carnival’s recent announcement that all of its cruise ships heading to the Arctic are no longer powered ultra-dirty fuel oil in favour of cleaner alternative marine gasoil.

Having largely praised the move for putting “the shipping sector on the pathway to a truly heavy fuel oil-free Arctic,” nevertheless believes this should only be the beginning, as Ulrich says Carnival is still a long way from being sustainable.

She adds that while marine gasoil undoubtedly deserves appraisal, is lobbying for “Carnival and the subsidiaries it operates to install catalysed diesel particulate filters,” which would significantly reduce the amount of polluting constituents in the air.

These filters, she argues, would work better than the Advanced Air Quality Systems Carnival has currently installed on about 80% of its global fleet, and that Ulrich describes as “simply scrubbers”.

As temperatures rise and arctic ice melts at an unprecedented speed, the cruise sector must undoubtedly take responsibility for its actions. But with both sides fighting their corner, the debate is still open and third parties – passengers, staff and the environment – risking paying the highest price.