Next time you’re on the New York City subway and take a deep breath, it’s more than oxygen and atmospheric moisture you’re breathing in! According to a 2013 study published by the American Society for Microbiology, 15% of what you’re actually breathing in is dead skin from other passengers.
From 2007 to 2008, microbiologists sampled the air at various subway stations in New York. Within the air they sampled, a surprising 15% came from skin of other riders, primarily from the heels and heads of those passengers. 12% of the skin came from other areas such as passenger armpits, ear canals, belly buttons, and rear-ends. The study found that there was little difference between the air from stations such as Grand Central and City Hall to the air breathed outside in Union Square Park. They did notice once exception though: there was an increased amount of fungus in the stations, which the study attributed to wood rot fungi on the wooden subway tracks.
“We encountered no organisms of public health concern,” the study stated. “The general uniformity of microbial assemblages throughout the system indicates good air mixing, a testimony to the efficiency of the train-pumping process.”
What else are you breathing in when you take a deep breath?
By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, which averages around 1% at sea level and 0.4% over the entire atmosphere. In very hot and humid air masses, the amount of water vapor can be as high as 5% of the overall contents of the atmosphere.
While many think air is mainly compromised of oxygen, in places like the New York City subway, there are far more gasses and substances than there is the essential oxygen.