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 Corp. 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."
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.
Kumar said the elevated levels found on the ships' decks "should be a matter of concern" given how easily the particles can enter 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 said the air had a distinctive fuel smell.
"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.
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.
Kennedy's study and others like it do not take into account ambient pollution either at land or at sea. The readings in Kennedy's report range. Sometimes the air quality is worse at port, other times it's worse at sea. But he did note one consistency.
"My trend across all four cruises and dozens of tests is that the stern levels were always higher," he said.
The stern, or back, of the ship is usually closer to the ship's smokestacks and protected from the harsher winds at the front of the ship. It's usually where cruise lines put outdoor amenities including basketball courts, rock climbing walls or mini-golf courses.
"Some of our highest readings were in the space specifically designed for exercise," Kennedy said.
This new study, done in partnership with environmental advocacy group Stand.earth, adds to a slim body of research on the air quality aboard cruise ships, which ferry nearly 30 million people across the world every year. Only two major studies have attempted to track the same data using the same device as Kennedy _ one by the Nature and Biodiversity Conservation Union in Germany and another by an investigative team of British journalists.
In 2017, cruising watchdog group NABU found levels as high as 400,000 ultrafine particles per cubic centimeter in some European ports. The British journalists, with Channel 4 Dispatches, measured particulate counts on deck double that of London's Piccadilly Circus with counts near the exhaust stacks skyrocketing to 144,000 particles per cubic centimeter.
Carnival called into question the motives of Stand.earth in a statement. "This particular organization, for fundraising purposes, is constantly in search of a problem in our industry even if it has to create fake tests that really have no scientific basis," said Frizzell. "The safety of our guests is our top priority and we undertake our cruises in close coordination with national and international regulatory bodies like the EPA to ensure the utmost safety of our guests and crew."