1. Yes, it is so, so many bacteria — but most of them are totally not a big deal.
“The vast majority of what we found are benign or inert for human health,” Mason says. And some of them may even be helpful to our health — like the bacteria associated with cleaning up toxins.

2. You should not be afraid to ride the subway, guys.
Mason isn’t. In fact, he says he’s even less freaked out now than he might have been before he did this study. “If anything, it makes me more confident,” he says. “I ride the subway every day, I bring my daughter on it with me, and the study has actually made me much more confident to grab a pole and hang on than I ever was before.”

3. It’s true, the researchers don’t even know what a lot of these bacteria even are.
“About half the DNA that we touch every day… we have no idea what they are,” Mason says. “It’s completely unclassified.”

4. But that’s an exciting thing, not scary. (At least for the researchers, anyway).
“We know based on these data that the vast majority of the DNA we touch is benign,” Mason says. “And even though a lot of it is unknown, I get excited about that because I’m surrounded by things that have never been seen before that are right under my fingertips. Much like looking at a rainforest, even. I can explore it and find new species, different animals, different plants. So I find that very exciting and invigorating to think about. Not a concern.”

5. That thing you read about the “germs that can cause bubonic plague uptown“? Don’t sweat it.
Don’t you think we’d notice if the bubonic plague were actually sweeping through our subway system and/or the Upper West Side?

“There’s been no documented case of any of the diseases that are associated with some of the DNA we found,” Mason says. “That’s additional evidence that there’s no reason whatsoever to be concerned. It’s really a testament I supposed to what the immune system can do.” The human body: AMAZING.

6. The more dense the population, the greater the diversity of bacteria.
“If you look at an average station in the Bronx, for example, it will have more unique species of bacteria than a station in Manhattan or Staten Island,” Mason says, because the Bronx has greater population density.

7. But more diverse bacteria might actually be a good thing, especially for younger people.
This is due to the “hygiene hypothesis,” Mason says. “It’s a hypothesis being studied in microbiology that thinks about the immune system. Martin Blaser recently wrote a book about this, called Missing Microbes. The idea actually is that when you’re younger, your immune system needs to have the ability for target practice, essentially — it needs to be exposed to antigens. In the absence of that, you’ll actually have a higher risk of asthma and allergies later in life. So to some degree, the greater bacterial diversity found in the surfaces is probably a good thing.” (He pointed out that they didn’t study this specifically in their research, but it’s a general idea that microbiologists are paying attention to lately.)

8. The railings contained the greatest diversity of bacteria.
Mason and his colleagues swabbed railings, seats, turnstiles, kiosks, and trashcans — basically everything that gets a LOT of use all day every day in a subway.

9. But those same metal railings had less total DNA on them than the wooden benches did.
So the bacteria on the poles was most diverse, but there was less of it total compared to other surfaces. “Metal in general is a good idea versus say wood, which can absorb a lot of things,” Mason says. The same can probably be said about seats with fabric on them (looking at you, San Francisco), but they didn’t test that in this study.

10. The bacterial DNA left in some stations could actually predict the ancestry of the people who live in that area.
This didn’t apply to high-traffic areas or to places with a lot of tourists, but in neighborhoods that lean predominantly toward one specific race or ethnicity, the subway bacteria reflected that.

“There are ancestry informative markers, genetic markers that can tell you where you come from in the world, whether you’re Finnish, or you’re British, Japanese, and so on,” Mason says. “There’s a catalogue of genetic variants that are known to be distributed around the world. And we can use the knowledge of human genetic variation, and take that data and combine it with census data, and when we blend those two together we see a mirror of them on the surface of the subway.”

11. Hurricane Sandy impacted the bacteria in South Ferry Station.
“One of the most notable stations was the South Ferry Station,” Mason says. “So it had a unique mixture, and also some lower levels of bacteria. It was a very unique station in that regard, and it’s because it had been so flooded.”

12. There’s a lot of cheese bacteria in the subway because New Yorkers love their pizza.
Oh, and Mason doesn’t think that people are just barfing up pizza on the subway all the time (we asked him). “I think it’s because people eat pizza and they don’t wash their hands after they eat it and they touch the subway railings.” Sounds about right.

13. No subway stations are better or worse than others when it comes to nasty bugs.
“When we looked at one station every hour on the hour, the microbial diversity changes so fast because you have tens of thousands of hands touching every surface,” Mason says. “To say that one station is better or worse than another at one snapshot in time would be unfair to that station, because it could be different the next day. And also everything that would be there would likely be normal healthy things anyway. So I don’t want people to avoid a subway station just because of one dataset from one or two days.”