The report, titled “An investigation of air pollution on the decks of 4 cruise ships” was authored by Dr. Ryan Kennedy, an assistant professor at the Johns Hopkins University Bloomberg School of Public Health.

More than 30 million people worldwide are expected to go on a cruise in 2019, and these cruise passengers and staff may be exposed to concerning levels of air pollution that could impact their health. Despite being on the open sea, they can be breathing dirty air worse than some of the world’s most polluted cities,

...said Dr. Ryan Kennedy, a researcher at the Johns Hopkins University Bloomberg School of Public Health.

The study measured the concentration of PM (particles with sizes between 0.02- 1.0 µm) on

  • the deck of two Carnival Cruise Line ships in the Caribbean, the Carnival Liberty during October 2017 and the Carnival Freedom during April–May 2018;
  • the deck of a Holland America ship (MS Amsterdam) that traveled along the west coast of Canada and the US during October 2018;
  • the deck of a Princess ship (Emerald) that traveled along the west coast of the US and Mexico during November 2018.

Measurements were taken inconspicuously in the bow area (fore of the smokestacks), as well as in two areas in the stern, aft of the ship’s smokestack including areas designated for exercise (running tracks, basketball court).

The average PM readings in the stern areas of each ship were significantly higher than the average readings measured fore of the smokestacks (towards the bow) (paired t-tests, alpha 0.05).

The findings of this study demonstrate that a source of PM—likely, in part from the ship’s exhaust system—is contributing to poorer air quality in the stern areas of these cruise ships.

Concentrations of PM on the decks of these ships are comparable to concentrations measured in polluted cities, including Beijing and Santiago. Despite being on the open water and in open air, vacationers and cruise ship staff may be exposed to elevated concentrations of PM.


  • While all four ships were traveling at sea, average particle counts were significantly higher in the areas behind the smokestacks (stern).
  • Particle counts on the Holland America MS Amsterdam were approximately eight times higher on the stern areas than on the bow.
  • Particle counts on the Carnival Freedom measured as high as 73,621 particles per cubic centimeter (pt/cc) near the running track while at sea.
  • Particle counts on the Princess Cruises Emerald Princess measured as high as 157,716 pt/cc on the lower stern while at sea.

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.

In addition to the report’s documented air pollution impacts on cruise passengers and staff, studies have shown approximately 70% of ship emissions occur within 250 miles of land, potentially exposing millions of unsuspecting people to dangerous air pollution levels and raising serious health concerns for coastal cities and port communities.

Notably, all four ships in this study have scrubbers installed, which allows the ships to burn HFO inside most of the North American and Caribbean Emissions Control Areas, where there are strict limits on emissions. In California, where scrubbers are banned within 24 miles from shore, ships are required to switch to a cleaner-burning fuel.

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