This story was originally published by National Observer and is reproduced here as part of the Climate Desk collaboration.

Ryan Kennedy had never been on a cruise ship until two years ago when he embarked on four North American cruises armed with a P-TRAK Ultrafine Particle Counter. This device is a portable digital contraption. It measures minute particles of air pollution that, when inhaled, can cause harm to your heart and lungs.

Kennedy, an assistant professor at the Johns Hopkins University Bloomberg School of Public Health, is the author of a new study, released Thursday, which details the findings of a two-year study exposing poor air quality on four Carnival Corporation ships — the largest cruise operator in the world — including one that left Vancouver for Los Angeles in October 2018.

The report, titled “An investigation of air pollution on the decks of four cruise ships,” found that air pollution on these ships was significantly worse than some of the world’s most polluted cities like Beijing, China or Santiago, Chile.

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Kennedy measured air pollution every second for one minute and created an average for each minute for 20 minutes at time, during the day and night. His findings reveal that while all four ships were traveling at sea, average pollution particle counts were significantly higher at the stern — the area on a ship behind the smokestacks.

The lowest particle count across these four ships was 38,888 particles per cubic centimeter (pt/cc), while the highest was 157,716 pt/cc. Particle counts on the L.A.-bound ship got as high as 76,000 pt/cc while out at sea, the investigation found.

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In comparison, pollution measurements taken with the same equipment in Beijing, China in 2009 were 30,000 pt/cc on a busy street, and in Santiago, Chile in 2011-2012 were in the ranges of 8,000-30,100 pt/cc.

“It’s very compelling data,” Kennedy told reporters on a conference call from Baltimore, Maryland. “People who are predisposed with cardiovascular or pulmonary conditions are at greater risk.”

He continued: “It’s dangerous. It’s not a healthy thing for us to be exposed to.”

The study was commissioned by the international environmental organization, and is the first to measure air quality on cruise ships when docked at port and while moving at sea, during multi-day cruises. The research has not yet been submitted to a scientific journal for peer review, but Kennedy said he was considering this as a next step.

Ultrafine particulate pollution can be detrimental to human health because of increased toxicity. These particles are small enough to be inhaled into a person’s lungs and move into the bloodstream, where they can cause higher rates of cardiovascular disease and asthma, Kennedy explained.

Recent studies have suggested that the smallest ultrafine particles may be the most dangerous to human health, and that particulate matter from ship exhaust may be responsible for tens of thousands of annual deaths, according to the report.

In light of the study’s findings, is calling on Carnival Corporation, which holds 40 percent of the global market, to transition away from heavy fuel oil to power its ships, to help reduce ultrafine particulate pollution — and “to step up to the plate and clean up its act,” according to Kendra Ulrich,’s senior shipping campaigner.

Of the 26.6 million people that went on cruises last year, nearly half, about 12 million people, went on a Carnival or one of its 10 subsidiary cruise lines. Most of Carnival Corporation’s ships burn heavy fuel oil where allowable, according to the report. Heavy fuel oil is a toxic, “bottom of the barrel waste sludge leftover” from the refining process, Uldrich explained, and is often classified as hazardous waste.

Ulrich believes the findings have implications far beyond the passengers and workers on the cruise ships. It could impact those who live and work in port and coastal communities where the ship docks or passes. Some studies have shown approximately 70 percent of ship emissions occur within 250 miles of land, she explained.

More than 30 million people worldwide are expected to go on a cruise in 2019 — many of whom are expected to be senior citizens.

“What Dr. Kennedy found on board was shocking,” Ulrich told reporters on the same conference call, noting that the stern — where the highest pollution levels were found — is usually where running tracks, swimming pools, or lounge areas are located on a cruise ship, where people spend the most time. “But, this is a pervasive health concern that extends far beyond the short term acute health exposures on the ship.”

Ulrich is urging Carnival Corporation to switch to a cleaner-burning fuel while installing filters to help reduce ultrafine particulate pollution, and eventually transition away from fossil-fuel powered ships completely.

Kennedy told reporters that there were limitations to his study, in that he conducted it inconspicuously so as to not disrupt cruise passengers and workers. His study measured emissions aboard only four ships, over short intervals rather than extended periods. He told reporters that the potential health impacts from particulate matter can also differ depending on how long someone is exposed to it.

“There are physical models and human studies that can be linked to a physiological impact to even short-term exposure,” Kennedy said. “There would be people who are more vulnerable, there are people who would have asthma, people who would be more concerned.”

But, Kennedy said he “made every effort to be consistent with my methods across environments. But I wasn’t able to measure everything, everywhere, always.”

The report goes on to say that the size of the particulate matter measured by Kennedy’s device “aligns closely with the size of particles known to be generated by ship engines, and the ship’s exhaust system is located between the environments” in question in the study, “suggesting the particulate matter is likely, in part, the ship’s engine exhaust.”

But, the study also says that “there is not universal agreement on how to measure or report particulate matter,” and that there remain unknowns in the study, including which fuel types were used by the ships and how efficient the engines were. The report also notes that higher winds could play a factor in the disparity between measurements in the front and back of the ships, at port and at sea.

In an email statement to National Observera Carnival Corporation spokesperson responded to the study, saying “these so-called fly-by tests are completely ridiculous, inaccurate, and in no way represent reality.”

“We test the air quality of our ships and they meet or exceed every requirement,” the spokesperson said. “The air quality on our ship decks when in port compares favorably with a typical urban or suburban environment. Independent testing on our funnels — which is the area where the exhaust originates — further validates our claims.”

The company declined to answer questions about how they test the air quality.

The spokesperson told National Observer that they have installed Advanced Air Quality Systems on nearly 80 percent of its global fleet, as required by the United States Environmental Protection Agency, “so these systems are environmentally friendly, in addition to rolling out new ships powered by LNG, the cleanest burning fuel available, so their study is misleading and inaccurate.”

The company added in their statement that Stand.Earth is creating “fake tests that really have no scientific basis,” to aid in their fundraising efforts. The organization, the statement said, “is constantly in search of a problem in our industry. 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 insure the utmost safety of our guests and crew.”

Some cruise ships and shipping lines began phasing out bunker fuel as the International Maritime Organization — a body of the United Nations — gears up to implement rules in 2020 that will require ships to either install expensive scrubbers or switch to different fuels.