Perhaps it was due to the fever of impending flu, or the arctic winds rattling our Tokyo home, but recent media photos of Beijing's thick smog suddenly brought to mind thoughts of the late U.S. president, John F. Kennedy.

On June 26, 1963, Kennedy delivered his most famous Cold War speech to reassure the people of Germany that the United States would not abandon the citizens of West Berlin.

By then, those citizens had been encircled by the 155-km-long Berlin Wall erected by the German Democratic Republic (East Germany) in 1961, ostensibly to protect them from Nazis still abroad in the West — but actually to stem the rising tide of defections.

"All free men, wherever they may live, are citizens of Berlin, and, therefore, as a free man, I take pride in the words, 'Ich bin ein Berliner!' " Kennedy drawled in his iconic Boston accent from the steps of the Rathaus Schoneberg city hall in West Berlin.

Were Kennedy alive today, and were he as concerned about pollution as he was about communism in 1963, he might visit China to reassure local citizens that the world is taking notice.

Looking out over crowds barely visible through the smoggy haze that often blankets that city, I can imagine Kennedy intoning, "I am a Beijinger!" (in Chinese, of course).

Earlier this month, on Jan. 19, a jocular piece by journalist Jaime A. FlorCruz appeared on the CNN International website decrying Beijing's toxic haze.

"It's another bad-air day in Beijing. You can barely see. You can barely breathe. But you can feel — and even taste — the grit floating in the air," he wrote. "The World Health Organization has set the healthy level of Air Quality Index at 25 micrograms, while Beijing considers a 300 reading as 'Bad' and 500 as 'Hazardous.' Last weekend, however, it breached 700!"

It's not just Beijing. FlorCruz reported that "20 of the 30 most polluted cities in the world are in China," citing the World Bank.

Meanwhile, the rest of us who do not live in the world's murkiest cities breathe a sigh of relief, thankful that we are living in places with better air quality — probably a lot better.

But even as we count our blessings, and chide our global neighbors, we might do well not to dismiss others' air-quality problems too blithely. With serious pollution afflicting most of the developing world, as well as many major cities in developed nations, it is worth considering how closely connected we all are.

The truth is, to some extent, we are all Chinese. We all breathe the air that our fellow global citizens breathe in Beijing.

On June 10, 1963, just two weeks before his speech in Berlin, Kennedy spoke at the American University, in Washington D.C. There, his theme was, in his own words, "the most important topic on Earth: world peace." Though he was speaking at a time when nuclear war was perceived as the greatest threat to Earth, if he were doing so now he might well be addressing the issue of global cooperation to conserve the planet.

"If we cannot end now our differences, at least we can help make the world safe for diversity," he told his Washington audience. "For, in the final analysis, our most basic common link is that we all inhabit this small planet. We all breathe the same air. We all cherish our children's future. And we are all mortal."

That day, Kennedy was not just inspiring and articulate, he was also speaking the truth: We really do all breathe the same air.

Perhaps you have heard the folk wisdom that each day each of us breathes the same air as was in Julius Caesar's last breath. I heard a similar tale in college from a professor of Shakespearean literature who sought to inspire in his students a more personal interest in the Bard.

Since then I've always assumed there must be some truth to this staple of cocktail-party scientific wisdom, but I never made an effort to find out — until now.

An Internet search for "Julius Ceasar's last breath" brought up numerous sites, and one that seemed to have a bit more authority than the others caught my eye.

"Is it true that we're breathing the same molecules once breathed by the dinosaurs, Julius Caesar or Jesus Christ?" read the title of a short piece on the magazine webpage of Marquette University, a private Jesuit seat of learning in Milwaukee, Wisconsin.

"There is some truth to this possibility," writes Dr. Martin St. Maurice. "The air we breathe is composed primarily of nitrogen gas and oxygen gas with a small amount of other gases, including carbon dioxide. All of these individual molecules are constantly rearranged and recycled through biochemical and geochemical processes, so you aren't breathing in the exact same gas molecules that dinosaurs and Julius Caesar once breathed.

"The individual atoms making up those molecules, however, have been on Earth for a long time. So every breath you take and every bit you swallow is composed of atoms that have been here for a long time," explains St. Maurice, an assistant professor of biological sciences.

"So, while you aren't likely to ever share exactly the same atom of oxygen as Brad Pitt, every breath you take has, at one time or another, been associated with another living organism."

But wait. Don't despair if you are a fan of Brad Pitt or Julius Caesar; a certain Jeffery Scott Nuttall disagrees with St. Maurice, judging from a comment on the same page.

"Your conclusion about the slimness of the chances of sharing an atom of oxygen with Caesar is mistaken. It may seem an intuitively obvious result given some of the assumptions and intermediate calculations, but this is a case in which intuition is misleading. For a detailed calculation of the problem, see 'Atom: An Odyssey From the Big Bang to Life on Earth,' by Lawrence Maxwell Krauss. Counterintuitively, and contrary to your conclusion, it turns out that your sharing oxygen atoms with Caesar is not only likely, but almost inevitable — indeed, there's better than a 99 percent chance that any given breath you take shares an atom with Caesar's last breath," writes Nuttall (marquette.edu/magazine/recent.php?subaction=showfull&id=1273588200)

Which brings us back to Kennedy's words and the fact that we all share the same air and, to some extent, the haze in Beijing and in other cities across the planet will eventually make its way into our lungs.

Of course these toxins are an infinitesimal part of all the gases and particulates that pass into our bodies, but the point is that what goes around comes around — again and again and again.

In years past, some of the most hazardous air originated in New York, London and Tokyo; whereas today it might be Bangkok, Beijing and Mexico City. In our air, in our water, in our food, even in every drop of breast milk, there are pollutants that have circled the planet and will do so repeatedly.

Traces of the radioactivity released into the atmosphere because of the reactor accidents at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant following the March 11, 2011, Great East Japan Earthquake have already circled the planet — relatively benignly perhaps, but most certainly.

Just as climate change due to human emissions of greenhouse gases is impacting all areas of our planet, none of us are untouched by the pollution problems that afflict our fellow human beings across the globe.

Kennedy was speaking of world peace, but his prescient words are equally relevant to the pressing environmental challenges that face humanity and Earth:

"In the final analysis, our most basic common link is that we all inhabit this small planet. We all breathe the same air. We all cherish our children's future. And we are all mortal."

Those of us who do not live in Beijing can count our blessings, but with each breath we take it's worth remembering that, to a greater or lesser extent, we are all sharing the same spaceship — Earth.

In that sense, we are all Chinese.

Stephen Hesse is a professor in the Law Faculty of Chuo University and Assistant Director of the Chuo International Center. He can be reached at [email protected].