Even out at sea, the air on cruise ships may be dirtier than you think, study shows

You can get away from it all — all, that is, but polluted air — on an ocean cruise. The salt breeze on the deck of a cruise ship may not be as fresh and clean as the beach air its meant to evoke, a new study reveals.

An associate professor at the Johns Hopkins Bloomberg School of Public Health, Ryan Kennedy, secretly measured the amount of ultrafine particles in the air on four cruise ships. He found measurements similar to prominently polluted places such as Beijing and Taipei, Taiwan, with the worst readings taken in areas designated for exercise or children’s activities. Carnival Corporation said Kennedy’s tests were “completely ridiculous, inaccurate and in no way represent reality.”

Kennedy’s research contradicts the long-held belief that the air at sea is clean, and that the emissions from cruise ships don’t affect passengers.

“I think there’s a perception that these ships are out there in the middle of nowhere and the winds just disperse it,” Kennedy said. “You’re still being exposed to these ultrafine particles.”

Quartet of tests

Kennedy tested the air on four cruise ships: Carnival Liberty in October 2017, Carnival Freedom in April-May 2018 in the Caribbean, Holland America Amsterdam in October 2018, and Princess Emerald in November 2018 off the West Coast of the U.S.

He counted the tiny particles of pollutants in the air on board, called ultrafine or nano particles because each piece is smaller than 0.1 cubic centimeters. Currently the Environmental Protection Agency doesn’t have standards for safe limits of those particles, although an EPA scientific advisory board met last month to begin reviewing data.

Nanoparticles are so small that when breathed in they can enter the bloodstream or even the brain, said the University of Miami’s Naresh Kumar, an associate professor of environmental health in the department of public health sciences.

“The smaller the size the more impact they’ll have on more parts of the body,” he said.

These particles can make people sneeze and cough, or even affect their blood pressure. These impacts are more harmful to vulnerable populations such as the elderly, children or people with lung and heart issues. If someone is around these particles often for years at a time, Kumar said, it can even lead to neurodegenerative diseases such as brain tumors or Alzheimer’s.

“If you’re spending a day or two and going back to a safe environment you wouldn’t experience the same effects,” he said.

‘A matter of concern’

Kumar said the elevated levels found on the ships’ decks “should be a matter of concern” given how easily those tiny particles can infiltrate the body.

The source of the particles makes a difference in the health impact; particles from burning diesel are proven carcinogens, but saltwater particles are harmless. Carnival did not confirm what kind of fuel the ships were burning at the time of the tests.

Kennedy did not test which particles were in the ship decks’ air, but he said the fuel smell in the air was distinctive.

“There’s no question in my mind that the source is diesel or some other equivalent,” he said.

So how bad is the air on cruise ships? Unlike the EPA’s standards for fine particulate pollution, which has a clear green-yellow-red system for showing air quality, there’s no such standard for ultrafine particles, so the closest comparison is measuring rates in notably polluted cities.

In this study, Kennedy secretly counted pollutants at port and at sea. He found average particle counts ranging from 1,540 to 33,514 particles per cubic centimeter across all four ships. Before the study began, he tested the air on a beach and found an average reading of under 500 particles per cubic centimeter. A nearby idling diesel car registered in the tens of thousands.

He compared these results to tests done with the exact same device in infamously polluted cities. A busy street in Beijing in 2009 showed concentrations of about 30,000 particles per cubic centimeter, and a train station in Taipei in 2009 had readings averaging 15,500 particles per cubic centimeter.

On the move

Major cruise lines said regulations don’t require them to measure air quality, but Carnival said it tests emissions levels at port and at sea inside the wing-shaped smokestacks that have become the cruise line’s trademark. They also test air quality on deck at port. Roger Frizzell, a Carnival spokesperson, said, “The air quality on our ship decks when in port compares favorably with a typical urban or suburban environment.”

Mike Kaczmarek, Carnival’s senior vice president of marine technology and refit, said ship smokestacks are purposefully tall to disperse pollutants away from passengers.

“It really hasn’t been an issue because the ship is moving, the air is flowing. It’s like sitting on top of your car. Would you be worried about air quality on the roof of your car?” he said.

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