Air pollution from cruise ships could be damaging the health of people living in port cities by increasing inflammation and susceptibility to viruses such as the common cold and COVID-19.

New research from the University of Southampton published in Environment International studied the air within Southampton’s port.

The air contained ultrafine particulate matter (PM), particles of dust no bigger than one thousandth the width of a human hair, enriched with trace elements from the burning of shipping fuel.

Lab tests found these particles increase inflammatory signals and weaken cells’ defence against viral infections, like COVID-19 or the common cold.

“In this research we’ve identified a clear air pollution ‘signature’ coming from cruise ships burning fuel in ports,” says Matthew Loxham, Professor of Respiratory Biology and Toxicology and senior author of the study.

“The ultrafine particles contained in these ships’ emissions can penetrate deeper into the lungs than larger sizes of particulate matter, and may be able to enter the bloodstream, but particles of this size are essentially unregulated, and generally not monitored.

“We found that exposure of cells to these particles, and vanadium – the most enriched element in the particles – was both pro-inflammatory and facilitated the replication of viruses.”

Identifying the source

For the first-time, researchers have carried out an in-depth investigation of the make-up and toxicology of PM within a busy port.

The team chose five sampling sites located around Southampton’s port area including a dock gate used for movement of heavy good vehicles, a container ship terminal, and a busy cruise terminal. They also sampled a comparison site, situated 5 km away from the port, to provide a benchmark reading.

PM samples were collected in the late spring and early summer, as well as during the winter at the cruise terminal during the ‘off-season’ when far fewer cruise ships visit.

At the cruise terminal, researchers found higher levels of vanadium, nickel and cobalt in fine and ultrafine PM during the busy summer season than in the quieter winter months.

Concentrations of these trace elements were also generally higher across the port than at the comparison site.

Dr Nat Easton, lead author of the study also from the University of Southampton, said: “We see increases in concentration when the wind was coming from the direction of the cruise ships, and when cruise ship presence was higher.

“The higher concentrations at the cruise terminal than the rest of the port is perhaps due to increased emissions from ‘hoteling’ cruise ships compared to cargo ships, but difference in fuel origins and berth occupancy times may also play a role.”

Health implications

In lab tests using lung lining cells, researchers found there was an increase in the expression of genes relating to an inflammatory response and a decrease in expression of antiviral response genes when exposed to the summer season’s cruise terminal ultrafine PM.

Additional tests revealed that vanadium may play a role in this. Prof Loxham explains: “To study this further, we infected bronchial epithelial cells from the lungs of healthy donors with human rhinovirus (the virus which causes the common cold and a leading cause of hospitalisations following asthma attacks) and also used a model of COVID-19 coronavirus infection.

“When exposed to vanadium, the number of copies of both viruses increased, indicating vanadium’s role in diminishing the ability of cells to prevent viral replication. This has potential implications for the severity and spread of infection.”

The researchers say the findings lend weight to calls to reduce emissions from ships in populated areas through the adoption of shoreside power from clean energy sources, carefully-selected alternative fuels, or improvement of emissions reduction technology.

They also say increased monitoring of ultrafine PM and its health impacts is needed to inform regulation and better protect the health of people living near ports around the world.

The paper Unregulated particulate matter emissions from cruise ships promote inflammation and susceptibility to viral infection is published in Environment International and is available online.

The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Leverhulme Trust, Medical Research Council (MRC), National Institute for Health and Care Research (NIHR) Southampton Biomedical Research Centre, the Southampton Marine and Maritime Institute, and the Southampton Institute for Life Sciences.

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