Sea air, good for respiratory health? Uncertain

The origin of the rumor

Since the 18th century, coastal regions have been praised, including by doctors, for their beneficial impacts on the health and recovery of patients. In 1938, doctors writing in the medical journal The Lancet noted that their predecessors, a century and a half earlier, had spoken of the “energizing” effects of sea air. A movement promoting “convalescent homes” on the coast of England had even appeared at the time.

Nowadays, it is rather the tourism industry (like here and here) which praises the health benefits of the coastal environment, particularly in reducing respiratory problems.

Few studies on a link

Yet, there are few studies to confirm whether there is indeed a link. In 2012, researchers in the United Kingdom used the 2001 census to try to answer the question. They noticed that as one approaches the coast, the level of health reported by individuals seems to improve.

In 2019, Belgian scientists did the same exercise and concluded that people who lived less than 5 km from the sea reported better general health than those who lived 50 to 100 km inland. A study carried out by other European researchers in 2023 noted that the health effect reported was greater for people who live less than 2 km from the coast.

According to these scientists, several factors could be at work. For example, the seaside might be more conducive to physical activity and would also reduce stress.

However, it would also be possible that this environment has physical and chemical characteristics that would positively influence health.

What we know about salty air

When waves break on the surface of the sea or ocean, a rain of fine droplets forms and is then carried away by the wind. This is called sea spray. They carry with them salts of sodium, magnesium, calcium and potassium. We can also detect these salts in large quantities in the air up to 500 meters from the seaside, American researchers explained in 2021. Scientists estimate that this concentration is between 0.006 and 0.02 micrograms (μg) of salts per liter of air. A person who breathes this air all day would inhale 60 to 200 μg of salt per day.

Still according to these American researchers – who wondered at the time about the beneficial link that this could have against a respiratory disease like COVID – breathing the salts present in the air would be a good way to improve the hydration of the respiratory tract and help clear mucus.

In interview for the Wall Street Journal In 2014, American doctor Thomas Ferkol reported that several of his patients suffering from cystic fibrosis – a rare disease that affects the mucous and respiratory tract – said they felt better during their trip to the coast.

It was observations of this kind that inspired doctors to develop a device allowing people suffering from cystic fibrosis to inhale a saline solution. According to a study published in 2006 in the New England Journal of Medicineuse of this device for one year was reportedly associated with a “moderate” improvement in lung function and a reduction in the number of episodes of infection and acute lung inflammation. This strategy is still recommended, particularly in the United States, on the Cystic Fibrosis Foundation website.

Furthermore, in their 2021 article, American researchers concluded that the high levels of salts in the air as well as the high level of humidity near the sea would have made it possible to reduce the incidence of COVID-19. 19 and the number of deaths in coastal regions of the United States. According to the authors, saline air reduces the production of droplets and therefore the transmission of the virus.

Really cleaner air?

When we don’t mention salt and water, we often fall backt on lhe better air quality in coastal regions to explain its benefits. In their 2019 study, Belgian researchers also measured that pollution was less significant in cities located less than 5 km from the sea.

However, more recent data seems to indicate that sea air is not as clean as claimed. Biogenic molecules can be found there during the formation of sea spray, explained in 2019 the team of researcher Emmanuel Van Acker, from Ghent University in Belgium. These molecules, which are produced in water by bacteria and phytoplankton, include vitamins, pigments and polyphenols, but also phycotoxins — such as those that can be produced during algae proliferation. These substances could have health impacts when inhaled.

In 2022, the National Agency for Food, Environmental and Occupational Health Safety (ANSES) in France will also warn beach users against the toxins produced by marine microalgae to which they may be exposed. by inhaling sea spray. In a review on the subject published in 2023, scientists recalled that 15% of asthma cases in coastal regions are attributable to these toxins.

Finally, according to a study carried out by researchers from Stockholm in 2024, PFAS – chemical molecules used in several industrial processes and in certain consumer products – could be found in the air of coastal regions, since they are present in sea ​​spray. Indeed, PFAS, because they are known to accumulate in the oceans, can be “ejected” into the air.

Verdict

Certain characteristics of sea air could indeed promote hydration of the respiratory tract and improve the symptoms of certain diseases, particularly respiratory ones. However, in recent years we have discovered that seaside air can also contain contaminants that are harmful to health.